FR3139951A1 - CATHODE MATERIAL PRECURSOR, CATHODE MATERIAL, PREPARATION METHOD AND USE OF CATHODE MATERIAL - Google Patents

Abstract

A cathode material precursor is described. The cathode material precursor is prepared by a co-precipitation reaction, and a pH value of a system is controlled between 10 and 12 in the co-precipitation reaction. After the co-precipitation reaction reaches equilibrium, a difference between deformation stacking fault probabilities fD of crystals in the system measured in two arbitrary time periods at an interval of 4 h is greater than or equal to 0.7%, and the deformation stacking fault probability fD is calculated by a formula: fD=0.19FWHM(101)–0.055FWHM(102)–0.5/D(001), where FWHM(101 ) is a half peak width of a (101) diffraction peak, FWHM(102) is a half peak width of a (102) diffraction peak, and D(001) is a grain size d 'a face of crystal (001). The cathode material prepared by the cathode material precursor has excellent cycle performance and high first discharge capacity. (To be published with Figure 1)

Description

CATHODE MATERIAL PRECURSOR, CATHODE MATERIAL, PREPARATION METHOD AND USE OF CATHODE MATERIAL

The invention relates to the technical field of cathode materials for lithium-ion batteries, in particular a cathode material precursor, a cathode material, a preparation method and a use of the cathode material.

TECHNOLOGY BACKGROUND

In the context of "carbon neutrality" and "carbon peak", the traditional industrial energy structure is facing a new round of adjustment. Among others, the lithium battery industry, after several years of development, has become the pillar of the new energy sector. High-performance cathode materials are undoubtedly the crown of the entire upstream and downstream industrial chain, and 60% to 70% of the performance of cathode materials depends on their precursors. So, high-performance precursors are undoubtedly the most dazzling pearl in the crown.

Currently, lithium-ion battery cathode material precursors are generally prepared using a co-precipitation process, in which the nucleation and growth of crystals are mainly driven by a precipitation reaction and a complexation reaction. However, the cathode material prepared from the existing cathode material precursor, which is prepared by the co-precipitation method, has a low first discharge capacity and, at the same time, a cycle performance that still needs to be improved. .

SUMMARY

The present disclosure aims to resolve at least one of the technical problems existing in the prior art. To do this, the present disclosure provides a method for preparing a cathode material precursor. The cathode material prepared from the cathode material precursor, which is prepared by the present preparation method, has excellent cycle performance and high first discharge capacity.

The above technical objective of the present disclosure is achieved by the following technical solution.

A cathode material precursor is provided. The cathode material precursor is prepared by a co-precipitation reaction, a pH value of a system is controlled between 9 and 12 in the co-precipitation reaction; and after the co-precipitation reaction reaches equilibrium, a difference between deformation stacking fault probabilities f _D of crystals in the system measured in two arbitrary time periods at an interval of 4 h is greater or equal to 0.7%, and the deformation stacking fault probability f _D is calculated by a formula: f _D =0.19FWHM ₍₁₀₁₎ –0.055FWHM ₍₁₀₂₎ –0.5/D _（001） , where FWHM ₍₁₀₁₎ is a half peak width of a diffraction peak (101), FWHM ₍₁₀₂₎ is a half peak width of a diffraction peak (102), and D ₍₀₀₁₎ is a grain size of a crystal face (001).

Preferably, after the co-precipitation reaction reaches equilibrium, the strain stacking fault rate f _D of the crystals in the system is 1% to 10%.

Preferably, the cathode material precursor has a particle size distribution span value greater than or equal to 1.30, where span= (D ₉₀ -D ₁₀ )/D ₅₀ .

Preferably, a chemical formula of the cathode material precursor is Ni _x Co _y Mn _z (OH) ₂ , wherein 0 ≤ x ≤ 1, 0 ≤ y ≤ 0.9, 0 ≤ z ≤ 0.9, and x + y + z = 1.

A method for preparing the cathode material precursor as mentioned above comprises the following steps: (1) mixing a metal salt solution containing nickel, cobalt and manganese with a precipitating agent, a complexing agent and an alkaline base solution for a reaction to obtain a mixed solution, wherein a pH value of a system is controlled between 9 and 12 during the reaction; and after the particle size D50 of the obtained precursor crystal reaches 1 to 15 µm, adjusting the pH value of the system to control the co-precipitation reaction to reach an equilibrium, wherein adjusting the pH value comprises an increase in the pH value from 0.02 to 0.04 or a decrease in the pH value from 0.03 to 0.06; and (2) performing solid-liquid separation on the mixed solution obtained in step (1) to obtain a solid, and washing and drying the solid to obtain the cathode material precursor.

More preferably, the pH value is adjusted continuously after the particle size D50 of the precursor crystal obtained has reached 4 to 10 µm.

Preferably, in step (1), the pH adjustment comprises an increase in the pH value of the system from 0.02 to 0.04 when the D50 of the precursor crystal is greater than or equal to 0.3 µm per relative to a target particle size, and a decrease in the pH value of the system from 0.03 to 0.06 when the D50 of the precursor crystal is less than or equal to 0.3 µm relative to the target particle size.

Preferably, in step (1), the total concentration of metal ions of nickel, cobalt and manganese in the metal salt solution containing nickel, cobalt and manganese is 1 to 3 mol/L.

Preferably, in step (1), a molar ratio of the nickel element, the cobalt element and the manganese element in the metal salt solution containing nickel, cobalt and manganese is x:y : z, where 0 ≤ x ≤ 1, 0 ≤ y ≤ 0.9, 0 ≤ z ≤ 0.9, and x + y + z = 1.

Preferably, in step (1), the precipitating agent is at least one of a sodium hydroxide solution and a potassium hydroxide solution, and the precipitating agent has a concentration of 2 to 14 mol/L.

Preferably, in step (1), the complexing agent is ammonia with a mass fraction of 20%.

Preferably, in step (1), the alkaline base solution is a mixed solution of sodium hydroxide and ammonia, and the alkaline base solution has a pH value of 9 to 12 and a concentration of ammonia from 0 to 10 g/L.

Preferably, in step (1), the reaction is carried out in a reaction vessel, and mixing is carried out by adding the metal salt solution containing nickel, cobalt and manganese, the precipitating agent and the complexing agent to the alkaline base solution in parallel.

Preferably, in step (1), after the reaction has reached equilibrium, the difference between strain stacking fault probabilities f _D of the crystals in the mixed solution measured in two arbitrary time periods at a 4-hour interval is greater than or equal to 0.7%.

Preferably, in step (1), the reaction is carried out at a temperature of 50 to 80°C.

Preferably, in step (2), the drying is carried out at a temperature of 90 to 120℃, and the drying lasts for 30 to 50 hours.

A preparation method for a cathode material comprises the following steps: mixing the cathode material precursor as mentioned above with a lithium source and an additive, performing primary sintering in an aerobic atmosphere to obtain a material mainly sintered; and grinding the mainly sintered material, mixing with the additive, and performing secondary sintering in an aerobic atmosphere to obtain the cathode material.

Preferably, the lithium source is at least one of LiOH and Li ₂ CO ₃ .

Preferably, the additive is a compound containing at least one of the elements Ni, Co, Mn, Zr, Al, Mg, Ti, Sr, W, Y, Mo, Sb, Nb, Sn, Zn, La, Ce , B and F, or a combination of compounds containing at least one of the elements Ni, Co, Mn, Zr, Al, Mg, Ti, Sr, W, Y, Mo, Sb, Nb, Sn, Zn, La, This, B and F.

Preferably, a temperature for primary sintering is 700 to 1020°, and primary sintering lasts 28 to 32 hours.

Preferably, a temperature for the secondary sintering is 250 to 750°, and the secondary sintering lasts 6 to 9 hours.

A cathode material is prepared by the preparation method as described above.

Preferably, a chemical formula of the cathode material is Li _1+a Ni _x Co _y Mn _z M _b O ₂ @N _c , in which 0 ≤ a ≤ 0.2, 0 ≤ B ≤ 0.03, 0 ≤ c ≤ 0.04, and M and N are at least one of the elements Ni, Co, Mn, Zr, Al, Mg, Ti, Sr, W, Y, Mo, Sb, Nb, Sn, Zn, La, Ce , B and F.

It is also intended to use the cathode material as mentioned above in the preparation of a lithium-ion battery.

Disclosure of preparation has the following beneficial effects:

(1) In the preparation of the cathode material precursor of the present disclosure, the pH value of the synthesized precursor is controlled between 9 and 12, and the pH value is continuously adjusted after the particle size reaches the size of target particle. By continuously adjusting the pH value, the balance between the co-precipitation reaction and the complexation reaction is controlled, and the crystal growth rate is adjusted. Rapid crystal growth results in a high probability of defects, while slow crystal growth helps in obtaining ideal defect-free crystals. By continuously changing the pH value of the reaction system so as to change the crystal growth rate at different periods, a precursor with a gradient defect structure is obtained. The structural defect of the precursor is expressed by the growth stacking fault probability f _D , which can be calculated by fitting an X-ray diffraction (XRD) pattern of the precursor with X-pert Highscore software. After the precursor is lithiated and sintered at a high temperature, the cathode material inherits the gradient defect structure. The gradient defect structure can also release the stress generated in the lithium ion deintercalation process, so as to reduce the cracking of primary particles and secondary aggregates and improve the cycling performance of the cathode material. Additionally, the gradient defect mentioned above is at the atomic scale inside the material, and a gradient defect will not introduce a new interface or add a new interface impedance, improving thus the electrochemical performance of the material.

(2) In the preparation of the cathode material precursor of the present disclosure, it is easy to obtain high supersaturation (supersaturation S=[Me ²⁺ ][OH ^- ] ² /K ^θ sp,Me(OH) ₂ ) at a high pH value of the reaction system. Since the forces for driving nucleation and crystal growth are both supersaturated, crystals nucleate and grow at a higher rate under high supersaturation, resulting in excessive consumption of supersaturation. Due to the reaction system being at a high pH value, the balance between the precipitation reaction and the complexation reaction is broken, the precipitation reaction is enhanced and leads to the production of smaller particles within a short period of time. time, the particle size distribution of the precursor becomes wider, and a wide particle size distribution can effectively improve the apparent density of particles, thereby improving the energy density of the cathode material. The particle size distribution of the precursor is expressed as a span value, where span=(D ₉₀ -D ₁₀ )/D ₅₀ . The larger the scale value, the broader the particle size distribution of the precursor. As the metal solution is continuously replenished, the magnitude of supersaturation increases again, and then the above reaction process repeats periodically.

There is a scanning electron microscope (SEM) image of an 80 hour precursor process sample prepared in Example 1 of the present disclosure;

there is an SEM image of a precursor process sample at time 84 prepared in Example 1 of the present disclosure;

there is an SEM image of a cathode material prepared in Example 1 of the present disclosure;

there is an SEM image of an 80 hour precursor process sample prepared in Comparative Example 1 of the present disclosure;

there is an SEM image of a precursor process sample at time 84 prepared in Comparative Example 1 of the present disclosure;

there is a comparison chart of cycle capacity retention rates of cathode materials prepared in Example 1 and Comparative Example 1 of the present disclosure;

there is an X-ray diffraction pattern of finite precursors prepared by the co-precipitation method of Example 1 and Comparative Example 1 of the present disclosure.

there is a particle size distribution diagram of the finished precursors prepared by the co-precipitation method of Example 1 and Comparative Example 1 of the present disclosure.

DETAILED DESCRIPTION

The present disclosure will be described in more detail below in combination with specific examples.

Example 1:

A process for preparing a cathode material precursor comprised the following steps:

step 1, selecting as raw materials nickel chloride, cobalt chloride and manganese chloride at a molar ratio of 0.70:0.10:0.20 (Ni:Co:Mn), salt solution metal containing nickel, cobalt and manganese having a total nickel, cobalt and manganese metal ion concentration of 2.0 mol/L was prepared; a sodium hydroxide solution with a concentration of 4.5 mol/L was prepared as a precipitating agent; and ammonia having a mass fraction of 20% was prepared as a complexing agent;

step 2, an alkaline base solution was added into a reaction tank until a bottom stirring paddle overflowed, and stirring was started; where the alkaline base solution was a mixed solution of sodium hydroxide and ammonia, the alkaline base solution had a pH value of 11.7, and the ammonia had a concentration of 8.0 g/L;

step 3, the metal salt solution containing nickel, cobalt and manganese, sodium hydroxide solution and ammonia prepared in step 1 were added into the reaction vessel in parallel for synthesis reaction of a precursor in a continuous mode; where the reaction temperature in the tank was controlled at 65℃, the pH value was 11, and the ammonia had a concentration of 8.0 g/L;

step 4, a target particle size D50 of the precursor in the tank was set to 4.0 μm; and the pH value of the reaction was adjusted when the particle size D50 of the precursor in the tank was detected to be 4.0±0.3 μm, in particular, the pH value was increased by 0.02 when D50 was 0.3 μm larger than the target particle size, and the pH value was decreased by 0.03 μm when D50 was 0.3 μm smaller than the target particle size; and material was collected continuously;

step 5, solid-liquid separation was performed on the collected material, and a precipitate was washed away; And

Step 6, the precipitate was dried at 120℃ for 25 h to obtain a cathode material precursor.

Process samples at hour 80 and hour 84 of the reaction were taken for testing (4 h was much shorter than the residence time τ of the precursor particles in the reaction vessel, and only one small amount of secondary particles were discharged from an overflow port, so the material in the tank could be considered roughly the same batch), and the morphologies of the precursors were shown in the and the . Precursor stacking fault probabilities f _D established using X-pert Highscore software were 4.7% and 3.3%, respectively, a difference between f _D measured twice was 1.4%, and the span values calculated based on the results of a laser particle size analyzer were 1.21 and 1.37, respectively.

A cathode material precursor prepared by the above-mentioned preparation method had a chemical formula of Ni _0.70 Co _0.10 Mn _0.20 (OH) ₂ .

A process for preparing a cathode material included the following steps:

(1) the cathode material precursor as described above was well mixed with LiOH and ZrO ₂ additive, and then primary sintering was carried out in an aerobic atmosphere to obtain a mainly sintered material; where the cathode material precursor and LiOH were mixed at a molar ratio of 1.05 (Li/(Ni + Co + Mn)), the amount of ZrO ₂ added was 3000 ppm (based on the mass of Zr in ZrO ₂ relative to the precursor), a temperature for primary sintering was 925℃, and the primary sintering lasted for 30 h; And

(2) the mainly sintered material obtained in step (1) was coarsely ground, finely ground, and then mixed well with additives of WO ₃ and Al ₂ O ₃ , and secondary sintering was carried out in an aerobic atmosphere to obtaining a cathode material; wherein the amounts of WO ₃ and Al ₂ O ₃ added were 2000 ppm and 1000 ppm, respectively (based on the weights of W in WO ₃ and Al in Al ₂ O ₃ relative to a material of base), a temperature for secondary sintering was 650℃, and secondary sintering lasted for 8 h.

A cathode material prepared by the above-mentioned preparation method had a chemical formula of Li(Ni _0.70 Co _0.10 Mn _0.20 ) _0.997 Zr _0.003 O ₂ @W _0.00108 Al _0.00366 . The SEM image of the cathode material was shown on the .

Example 2:

A process for preparing a cathode material precursor comprised the following steps:

step 1, selecting as raw materials nickel chloride, cobalt chloride and manganese chloride at a molar ratio of 0.65:0.07:0.28 (Ni:Co:Mn), salt solution metal containing nickel, cobalt and manganese having a total nickel, cobalt and manganese metal ion concentration of 2.5 mol/L was prepared; a sodium hydroxide solution with a concentration of 5.5 mol/L was prepared as a precipitating agent; and ammonia having a mass fraction of 20% was prepared as a complexing agent;

step 2, an alkaline base solution was added into a reaction tank until a bottom stirring paddle overflowed, and stirring was started; where the alkaline base solution was a mixed solution of sodium hydroxide and ammonia, the alkaline base solution had a pH value of 11.9, and the ammonia had a concentration of 10 g/L;

step 3, the metal salt solution containing nickel, cobalt and manganese, sodium hydroxide solution and ammonia prepared in step 1 were added into the reaction vessel in parallel for synthesis reaction of a precursor in a continuous mode; where a reaction temperature in the tank was controlled at 60℃, the pH value was 11.5, and the ammonia had a concentration of 10 g/L;

step 4, a target particle size D50 of the precursor in the vat was set at 4.2 µm, a pH value of a reaction was adjusted when the particle size D50 of the precursor in the vat was detected at 4 .2±0.3 µm, in particular, the pH value was increased by 0.04 when D50 was 0.3 µm larger than the target particle size, and the pH value was decreased by 0.06 when D50 was 0.3 µm smaller than the target particle size; and material was collected continuously;

step 5, solid-liquid separation was performed on the collected material, and a precipitate was washed away; And

Step 6, the precipitate was dried at 115℃ for 30 h to obtain a cathode material precursor.

Process samples at hour 80 and hour 84 of the reaction were taken for testing (4 h was much shorter than the residence time τ of the precursor particles in the reaction vessel, and only one small amount of secondary particles were discharged from an overflow port, so the material in the tank could be considered approximately the same batch). Precursor stacking fault probabilities f _D established using X-pert Highscore software were 5.9% and 4.4%, respectively, a difference between f _D measured twice was 1.5%, and the span values calculated based on the results of a laser particle size analyzer were 1.11 and 1.40, respectively.

A cathode material precursor prepared by the above-mentioned preparation method had a chemical formula of Ni _0.65 Co _0.07 Mn _0.28 (OH) ₂ .

A process for preparing a cathode material included the following steps:

(1) the cathode material precursor as described above was well mixed with LiOH and additives of ZrO ₂ and SrO, and then primary sintering was carried out in an aerobic atmosphere to obtain a mainly sintered material; where the cathode material precursor and LiOH were mixed at a molar ratio of 1.06 (Li/(Ni + Co + Mn)), the amounts of ZrO ₂ and SrO added were 2000 ppm and 1500 ppm ( based on the mass of Zr in ZrO ₂ and Sr in SrO relative to the precursor), a temperature for primary sintering was 940℃, and the primary sintering lasted for 28 h; And

(2) the mainly sintered material obtained in step (1) was coarsely ground, finely ground and then mixed well with additives of Sb ₂ O ₃ and TiO ₂ , and secondary sintering was carried out in an aerobic atmosphere to obtaining a cathode material; where the amounts of Sb ₂ O ₃ and TiO ₂ added were 1500 ppm and 2000 ppm, respectively (based on the weights of Sb in Sb ₂ O ₃ and Ti in TiO ₂ relative to a base material ), a temperature for secondary sintering was 550℃, and secondary sintering lasted for 6 h.

A cathode material prepared by the above-mentioned preparation method had a chemical formula of Li(Ni _0.65 Co _0.07 Mn _0.28 ) _0.997 Zr _0.002 Sr _0.001 O ₂ @Sb _0.00122 Ti _0.00730 .

Example 3:

A process for preparing a cathode material precursor comprised the following steps:

step 1, selecting as raw materials nickel chloride, cobalt chloride and manganese chloride at a molar ratio of 0.80:0.10:0.10 (Ni:Co:Mn), salt solution metal containing nickel, cobalt and manganese having a total nickel, cobalt and manganese metal ion concentration of 1.5 mol/L was prepared; a sodium hydroxide solution having a concentration of 10 mol/L was prepared as a precipitating agent; and ammonia having a mass fraction of 20% was prepared as a complexing agent;

step 2, an alkaline base solution was added into a reaction tank until a bottom stirring paddle overflowed, and stirring was started; where the alkaline base solution was a mixed solution of sodium hydroxide and ammonia, the alkaline base solution had a pH value of 10.7, and the ammonia had a concentration of 4 g/L;

step 3, the metal salt solution containing nickel, cobalt and manganese, sodium hydroxide solution and ammonia prepared in step 1 were added into the reaction vessel in parallel for synthesis reaction of a precursor in a continuous mode; where the reaction temperature in the tank was controlled at 72℃, the pH value was 10.7, and the ammonia had a concentration of 4g/L;

step 4, a target particle size D50 of the precursor in the tank was set at 10 µm, a pH value of a reaction was adjusted when the particle size D50 of the precursor in the tank was detected at 10±0 .3 µm, in particular, the pH value was increased by 0.03 when D50 was 0.3 µm larger than the target particle size, and the pH value was decreased by 0.05 when D50 was 0.3 µm. 0.3 µm smaller than the target particle size; and material was collected continuously;

step 5, solid-liquid separation was performed on the collected material, and a precipitate was washed away; And

Step 6, the precipitate was dried at 90℃ for 42 h to obtain a cathode material precursor.

Process samples at hour 80 and hour 84 of the reaction were taken for testing (4 h was much shorter than the residence time τ of the precursor particles in the reaction vessel, and only one small amount of secondary particles were discharged from an overflow port, so the material in the tank could be considered approximately the same batch). Precursor stacking fault probabilities f _D established using X-pert Highscore software were 3.6% and 2.3%, respectively, a difference between f _D measured twice was 1.3%, and the span values calculated based on the results of a laser particle size analyzer were 1.21 and 1.45, respectively.

A cathode material precursor prepared by the above-mentioned preparation method had a chemical formula of Ni _0.80 Co _0.10 Mn _0.10 (OH) ₂ .

A process for preparing a cathode material included the following steps:

(1) The cathode material precursor as described above was well mixed with LiOH and additives of Y ₂ O ₃ and La ₂ O ₃ , and primary sintering was carried out in an aerobic atmosphere to obtain a mainly sintered material; where the cathode material precursor and LiOH were mixed at a molar ratio of 1.02 (Li/(Ni + Co + Mn)), the amounts of Y ₂ O ₃ and La ₂ O ₃ added were 1500 ppm and 2500 ppm (based on the masses of Y in Y ₂ O ₃ and La in La ₂ O ₃ relative to the precursor), a temperature for primary sintering was 875℃, and primary sintering lasted 32 h ; And

(2) the mainly sintered material obtained in step (1) was coarsely ground, finely ground and then mixed well with additives of Nb ₂ O ₅ and CeO ₂ , and secondary sintering was carried out in an aerobic atmosphere to obtaining a cathode material; where the amounts of Nb ₂ O ₅ and CeO ₂ added were 1500 ppm and 1500 ppm, respectively (based on the weights of Nb in Nb ₂ O ₅ and Ce in CeO ₂ relative to a base material) , a temperature for secondary sintering was 420℃, and secondary sintering lasted for 7 h.

A cathode material prepared by the above-mentioned preparation method had a chemical formula of Li(Ni _0.80 Co _0.10 Mn _0.10 ) _0.997 Y _0.00156 La _0.00164 O ₂ @Nb _0.00160 This _0.00552 .

Example 4:

A process for preparing a cathode material precursor comprised the following steps:

step 1, selecting as raw materials nickel chloride, cobalt chloride and manganese chloride at a molar ratio of 0.95:0.02:0.03 (Ni:Co:Mn), salt solution metal containing nickel, cobalt and manganese having a total nickel, cobalt and manganese metal ion concentration of 2 mol/L was prepared; a sodium hydroxide solution having a concentration of 14.0 mol/L was prepared as a precipitating agent; and ammonia having a mass fraction of 20% was prepared as a complexing agent;

step 2, an alkaline base solution was added into a reaction tank until a bottom stirring paddle overflowed, and stirring was started; where the alkaline base solution was a mixed solution of sodium hydroxide and ammonia, the alkaline base solution had a pH value of 10.8, and the ammonia had a concentration of 2 g/L;

step 3, the metal salt solution containing nickel, cobalt and manganese, sodium hydroxide solution and ammonia prepared in step 1 were added into the reaction vessel in parallel for synthesis reaction of a precursor in a continuous mode; where the reaction temperature in the tank was controlled at 50℃, a pH value was 10, and the ammonia had a concentration of 2 g/L;

step 4, a target particle size D50 of the precursor in the vat was set at 8 µm, and a pH value of a reaction was adjusted when the particle size D50 of the precursor in the vat was detected at 8± 0.3 µm, in particular, the pH value was increased by 0.03 when D50 was 0.3 µm larger than the target particle size, and the pH value was decreased by 0.04 when D50 was 0.3 µm smaller than the target particle size; and material was collected continuously;

step 5, solid-liquid separation was performed on the collected material, and a precipitate was washed away; And

Step 6, the precipitate was dried at 100℃ for 36 h to obtain a cathode material precursor.

Process samples at hour 80 and hour 84 of the reaction were taken for testing (4 h was much shorter than the residence time τ of the precursor particles in the reaction vessel, and only one small amount of secondary particles were discharged from an overflow port, so the material in the tank could be considered approximately the same batch). Precursor stacking fault probabilities f _D established using X-pert Highscore software were 2.6% and 1.9%, respectively, a difference between f _D measured twice was 0.7%, and the span values calculated based on the results of a laser particle size analyzer were 1.09 and 1.48, respectively.

A cathode material precursor prepared by the above-mentioned preparation method had a chemical formula of Ni _0.95 Co _0.02 Mn _0.03 (OH) ₂ .

A process for preparing a cathode material included the following steps:

(1) The cathode material precursor as described above was well mixed with LiOH and additives of MoO ₃ and B ₂ O ₃ , and primary sintering was carried out in an aerobic atmosphere to obtain a material mainly sintered; where the cathode material precursor and LiOH were mixed at a molar ratio of 1.01 (Li/(Ni + Co + Mn)), the amounts of MoO ₃ and B ₂ O ₃ added were 3000 ppm and 800 ppm (based on the masses of Mo in MoO ₃ and B in B ₂ O ₃ relative to the precursor), a temperature for primary sintering was 832℃; and the primary sintering lasted for 32 h; And

(2) the mainly sintered material obtained in step (1) was coarsely ground, finely ground and then mixed well with additives of MgCO ₃ and LiF, and secondary sintering was carried out in an aerobic atmosphere to obtain a material cathode; where the amounts of MgCO ₃ and LiF added were 2000 ppm and 1000 ppm, respectively (based on the weights of Mg in MgCO ₃ and F in LiF relative to a base material), a temperature for the Secondary sintering was 300℃, and the secondary sintering lasted for 9 h.

A cathode material prepared by the above-mentioned preparation method had a chemical formula of Li(Ni _0.95 Co _0.02 Mn _0.03 ) _0.997 Mo _0.00289 La _0.00053 O ₂ @Mg _0.00817 F _0.00368 .

Comparative example 1:

A process for preparing a cathode material precursor comprised the following steps:

step 1, selecting as raw materials nickel chloride, cobalt chloride and manganese chloride at a molar ratio of 0.70:0.10:0.20 (Ni:Co:Mn), salt solution metal containing nickel, cobalt and manganese having a total nickel, cobalt and manganese metal ion concentration of 2.0 mol/L was prepared; a sodium hydroxide solution with a concentration of 4.5 mol/L was prepared as a precipitating agent; and ammonia having a mass fraction of 20% was prepared as a complexing agent;

step 2, an alkaline base solution was added into a reaction tank until a bottom stirring paddle overflowed, and stirring was started; where the alkaline base solution was a mixed solution of sodium hydroxide and ammonia, the alkaline base solution had a pH value of 10.6, and the ammonia had a concentration of 4 g/L;

step 3, the metal salt solution containing nickel, cobalt and manganese, sodium hydroxide solution and ammonia prepared in step 1 were added into the reaction vessel in parallel for synthesis reaction of a precursor in a continuous mode; where the reaction temperature in the tank was controlled at 65℃, the pH value was 9.8, and the ammonia had a concentration of 4g/L;

step 4, a target particle size D50 of the precursor in the vat was set at 4.0 µm, a pH value of a reaction was adjusted when the particle size D50 of the precursor in the vat was detected at 4 .0±0.3 µm, in particular, the pH value was increased by 0.02 when D50 was 0.3 µm larger than the target particle size, and the pH value was decreased by 0.03 when D50 was 0.3 µm smaller than the target particle size; and material was collected continuously;

step 5, solid-liquid separation was performed on the collected material, and a precipitate was washed away; And

Step 6, the precipitate was dried at 120℃ for 25 h to obtain a cathode material precursor.

Process samples at hour 80 and hour 84 of the reaction were taken for testing (4 h was much shorter than the residence time τ of the precursor particles in the reaction vessel, and only one small amount of secondary particles were discharged from an overflow port, so the material in the tank could be considered roughly the same batch), and the morphologies of the precursors were shown at the and to the . Precursor stacking fault probabilities f _D established using X-pert Highscore software were 3.6% and 3.8%, respectively, a difference between f _D measured twice was 0.2%, and the span values calculated based on the results of a laser particle size analyzer were 1.12 and 1.11, respectively.

A cathode material precursor prepared by the above-mentioned preparation method had a chemical formula of Ni _0.70 Co _0.10 Mn _0.20 (OH) ₂ .

A process for preparing a cathode material included the following steps:

(1) the cathode material precursor as described above was well mixed with LiOH and ZrO ₂ additive, and then primary sintering was carried out in an aerobic atmosphere to obtain a mainly sintered material; where the cathode material precursor and LiOH were mixed at a molar ratio of 1.05 (Li/(Ni + Co + Mn)), the amount of ZrO ₂ added was 3000 ppm (based on the mass of Zr in ZrO ₂ relative to the precursor), a temperature for primary sintering was 925℃, and the primary sintering lasted for 30 h; And

(2) the mainly sintered material obtained in step (1) was coarsely ground, finely ground, and then mixed well with additives of WO ₃ and Al ₂ O ₃ , and secondary sintering was carried out in an aerobic atmosphere to obtaining a cathode material; wherein the amounts of WO ₃ and Al ₂ O ₃ added were 2000 ppm and 1000 ppm, respectively (based on the weights of W in WO ₃ and Al in Al ₂ O ₃ relative to a material of base), a temperature for secondary sintering was 650℃, and secondary sintering lasted for 8 h.

A cathode material prepared by the above-mentioned preparation method had a chemical formula of Li(Ni _0.70 Co _0.10 Mn _0.20 ) _0.997 Zr _0.003 O ₂ @W _0.00108 Al _0.00366 .

Comparative example 2:

A process for preparing a cathode material precursor comprised the following steps:

step 1, selecting as raw materials nickel chloride, cobalt chloride and manganese chloride at a molar ratio of 0.95:0.02:0.03 (Ni:Co:Mn), salt solution metal containing nickel, cobalt and manganese having a total nickel, cobalt and manganese metal ion concentration of 2 mol/L was prepared; a sodium hydroxide solution with a concentration of 14 mol/L was prepared as a precipitating agent; and ammonia having a mass fraction of 20% was prepared as a complexing agent;

step 2, an alkaline base solution was added into a reaction tank until a bottom stirring paddle overflowed, and stirring was started; where the alkaline base solution was a mixed solution of sodium hydroxide and ammonia, the alkaline base solution had a pH value of 10, and the ammonia had a concentration of 1 g/L;

step 3, the metal salt solution containing nickel, cobalt and manganese, sodium hydroxide solution and ammonia prepared in step 1 were added into the reaction vessel in parallel for synthesis reaction of a precursor in a continuous mode; where the reaction temperature in the tank was controlled at 50℃, the pH value was 9.2, and the ammonia had a concentration of 1 g/L;

step 4, a target particle size D50 of the precursor in the tank was set at 8 µm, a pH value of a reaction was adjusted when the particle size D50 of the precursor in the tank was detected at 8±0 .3 µm, in particular, the pH value was increased by 0.03 when D50 was 0.3 µm larger than the target particle size, and the pH value was decreased by 0.04 when D50 was 0.3 µm. 0.3 µm smaller than the target particle size; and material was collected continuously;

step 5, solid-liquid separation was performed on the collected material, and a precipitate was washed away; And

Step 6, the precipitate was dried at 100℃ for 36 h to obtain a cathode material precursor.

Process samples at hour 80 and hour 84 of the reaction were taken for testing (4 h was much shorter than the residence time τ of the precursor particles in the reaction vessel, and only one small amount of secondary particles were discharged from an overflow port, so the material in the tank could be considered approximately the same batch). Precursor stacking fault probabilities f _D established using X-pert Highscore software were 0.83% and 0.74%, respectively, a difference between f _D measured twice was 0.09%, and the span values calculated based on the results of a laser particle size analyzer were 1.08 and 1.03, respectively.

A cathode material precursor prepared by the above-mentioned preparation method had a chemical formula of Ni _0.95 Co _0.02 Mn _0.03 (OH) ₂ .

A process for preparing a cathode material included the following steps:

(1) The cathode material precursor as described above was well mixed with LiOH and additives of MoO ₃ and B ₂ O ₃ , and primary sintering was carried out in an aerobic atmosphere to obtain a material mainly sintered; where the cathode material precursor and LiOH were mixed at a molar ratio of 1.01 (Li/(Ni + Co + Mn)), the amounts of MoO ₃ and B ₂ O ₃ added were 3000 ppm and 800 ppm (based on the masses of Mo in MoO ₃ and B in B ₂ O ₃ relative to the precursor), a temperature for primary sintering was 832℃; and the primary sintering lasted for 32 h; And

(2) the mainly sintered material obtained in step (1) was coarsely ground, finely ground and then mixed well with additives of MgCO ₃ and LiF, and secondary sintering was carried out in an aerobic atmosphere to obtain a material cathode; where the amounts of MgCO ₃ and LiF added were 2000 ppm and 1000 ppm, respectively (based on the weights of Mg in MgCO ₃ and F in LiF relative to a base material), a temperature for the Secondary sintering was 300℃, and the secondary sintering lasted for 9 h.

A cathode material prepared by the above-mentioned preparation method had a chemical formula of Li(Ni _0.95 Co _0.02 Mn _0.03 ) _0.997 Mo _0.00289 La _0.00053 O ₂ @Mg _0.00817 F _0.00368 .

Test example:

The cathode materials of Examples 1 to 4 and Comparative Examples 1 and 2 were prepared into button cells respectively to test the electrochemical performance of lithium-ion batteries. The specific steps were as follows: using N-methylpyrrolidone as a solvent, a cathode active material was mixed with acetylene black and PVDF at a mass ratio of 8:1:1, and a sheet of aluminum was coated with a mixture and subjected to blow drying at 80℃ for 8 h, then vacuum drying at 120℃ for 12 h. A battery comprising a negative electrode made of a lithium metal plate, a membrane made of a polypropylene film and a 1M LiPF6-EC/DMC electrolyte solution (1:1, v/v) were assembled in test boxes. gloves protected by argon gas. The batteries were discharged at 0.1 C under a specific cut-off voltage to test the first discharge capacity and first efficiency, and then discharged for 100 cycles at 1 C under the same cut-off voltage as in the half test. -battery, and cycle capacity retention rates after 100 cycles were recorded. The test results are shown in Table 1, in which a comparison chart of the cycle capacity retention rates of the cathode materials prepared in Example 1 and Comparative Example 1 is shown in Table 1. ; and an X-ray diffraction (XRD) pattern of the finished precursor prepared by the co-precipitation method in Example 1 and Comparative Example 1 is shown in . It is shown in XRD that the main peak positions of the precursors are not obviously shifted, but in Example 1, the peak intensity ratio of I ₍₁₀₁₎ to I ₍₀₀₁₎ is obviously smaller. It has been shown by theoretical research that the peak intensity ratio of I ₍₁₀₁₎ to I ₍₀₀₁₎ is associated with defects in precursors, and the higher the peak intensity ratio of I ₍₁₀₁₎ to I ₍₀₀₁₎ is smaller, the more defects in the precursors there are. This directly demonstrates that the formation of defects in the precursor can be controlled by changing the process conditions in Example 1, thereby achieving a controllable preparation of a precursor with a gradient defect structure. The particle size distribution diagram of the finished precursors prepared by the co-precipitation method of Example 1 and Comparative Example 1 of the present disclosure is shown in Fig. . As shown in the , the particle size distributions of the precursors of Example 1 and Comparative Example 1 both follow normal distributions. However, the particle size distribution of the precursor in Example 1 is "thicker", indicating that its particle size distribution is broader, while the particle size distribution of the precursor in Comparative Example 1 is relatively concentrated. The particle size distribution of the precursors and the process adjustment mechanism in the examples corroborate each other.

Table 1: Battery performance test results Discharge capacity at 0.1 C (mAh/g) First efficiency Cycle capacity retention rate after 100 cycles Cut-off voltage for test Example 1 204 91.4% 92.4% 2.8 to 4.40 V Example 2 192 90.8% 93.7% 2.8 to 4.35 V Example 3 212 92.5% 91.2% 2.8 to 4.25 V Example 4 235 94.1% 90.1% 2.8 to 4.25 V Comparative example 1 197 88.2% 86.3% 2.8 to 4.40 V Comparative example 2 226 92.0% 87.6% 2.8 to 4.25 V

As shown in Table 1, the cathode material prepared from the cathode material precursor which is prepared by the preparation method of the present disclosure has excellent electrochemical performance, and exhibits discharge capacity at 0.1 C greater than 192 mAh/g, a first efficiency greater than 90.8%, and a cycle capacity retention rate after 100 cycles greater than 90.1%.

The examples described above are preferred embodiments of the present disclosure, but the embodiments of the present disclosure are not limited to the examples described above. All other changes, modifications, substitutions, combinations and simplifications made without departing from the spirit or principle of this disclosure shall be equivalent replacements and all fall within the protective scope of this disclosure.

Claims (9)

Cathode material precursor, wherein the cathode material precursor is prepared by a co-precipitation reaction, a pH value of a system is controlled between 10 and 12 in the co-precipitation reaction; and after the co-precipitation reaction reaches equilibrium, a difference between deformation stacking fault probabilities f _D of crystals in the system measured in two arbitrary time periods at an interval of 4 h is greater or equal to 0.7%, and the deformation stacking fault probability f _D is calculated by a formula: f _D =0.19FWHM ₍₁₀₁₎ –0.055FWHM ₍₁₀₂₎ –0.5/D _（001） , where FWHM ₍₁₀₁₎ is a half peak width of a diffraction peak (101), FWHM ₍₁₀₂₎ is a half peak width of a diffraction peak (102), and D ₍₀₀₁₎ is a grain size of a crystal face (001), the chemical formula of the cathode material precursor being Ni _x Co _y Mn _z (OH) ₂ , in which 0 ≤ x ≤ 1, 0 ≤ y ≤ 0.9, 0 ≤ z ≤ 0.9, and x + y + z = 1. A cathode material precursor according to claim 1, wherein after the co-precipitation reaction reaches equilibrium, the deformation stacking fault probability f _D of the crystals in the system is 1% to 10%. A cathode material precursor according to claim 1, wherein the cathode material precursor has a particle size distribution span value greater than or equal to 1.30, where span=(D ₉₀ -D ₁₀ )/D ₅₀ . Preparation process for the cathode material precursor according to any one of claims 1 to 3, comprising the following steps consisting of:
(1) mixing a metal salt solution containing nickel, cobalt and manganese with a precipitating agent, a complexing agent and an alkaline base solution for reaction to obtain a mixed solution, where a pH value of one system is controlled between 10 and 12 during the reaction, and after a particle size D50 of the obtained precursor crystal reaches 1 to 15 µm, adjust the pH value of the system to control the co-precipitation reaction to reach an equilibrium ; And
(2) performing solid-liquid separation on the mixed solution obtained in step (1) to obtain a solid, and washing and drying the solid to obtain the cathode material precursor. A preparation method for the cathode material precursor according to claim 4, wherein in step (1), adjusting the pH value comprises increasing the pH value of the system from 0.02 to 0, 04 when the D50 of the precursor crystal is greater than or equal to 0.3 µm relative to a target particle size, and a decrease in the pH value of the system from 0.03 to 0.06 when the D50 of the precursor crystal precursor is less than or equal to 0.3 µm relative to the target particle size. A preparation method for a cathode material, comprising the following steps: mixing the cathode material precursor according to any one of claims 1 to 3 with a lithium source and an additive, carrying out primary sintering in an aerobic atmosphere to obtain a mainly sintered material; and grinding the mainly sintered material, mixing with the additive, and performing secondary sintering in an aerobic atmosphere to obtain the cathode material. Process for preparing the cathode material according to claim 6, in which the additive is a compound containing at least one of the elements Ni, Co, Mn, Zr, Al, Mg, Ti, Sr, W, Y, Mo, Sb, Nb, Sn, Zn, La, Ce, B and F, or a combination of compounds containing at least one of the elements Ni, Co, Mn, Zr, Al, Mg, Ti, Sr, W, Y, Mo , Sb, Nb, Sn, Zn, La, Ce, B and F. Cathode material, prepared by the preparation method according to any one of claims 6 and 7, the chemical formula of the cathode material being Li _1+a Ni _x Co _y Mn _z M _b O ₂ @N _c , in which 0 ≤ a ≤ 0.2, 0 ≤ B ≤ 0.03, 0 ≤ c ≤ 0.04, and M and N are at least one of the elements Ni, Co, Mn, Zr, Al, Mg, Ti, Sr , W, Y, Mo, Sb, Nb, Sn, Zn, La, Ce, B and F. Use of the cathode material according to claim 8 in the preparation of a lithium-ion battery.