CN113394385A - Modified NCMA quaternary anode material and preparation method thereof - Google Patents

Modified NCMA quaternary anode material and preparation method thereof Download PDF

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CN113394385A
CN113394385A CN202110940495.6A CN202110940495A CN113394385A CN 113394385 A CN113394385 A CN 113394385A CN 202110940495 A CN202110940495 A CN 202110940495A CN 113394385 A CN113394385 A CN 113394385A
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precursor
nickel
equal
ncma
particle
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黄滔
李厦
李旻
周友元
黄承焕
赵俊豪
熊学
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Hunan Changyuan Lithium New Energy Co ltd
Hunan Changyuan Lico Co Ltd
Jinchi Energy Materials Co Ltd
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Hunan Changyuan Lithium New Energy Co ltd
Hunan Changyuan Lico Co Ltd
Jinchi Energy Materials Co Ltd
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Abstract

The invention belongs to the technical field of lithium ion battery materials, and particularly discloses a modified NCMA quaternary anode material and a preparation method thereof. The quaternary positive electrode material is formed by grading and sintering two precursors with different secondary particle sizes; before grading, the two precursors are pretreated. Pre-treating the precursor, including in-situ coating the precursor with larger particle size to improve the rate capability and capacity; the precursor with smaller particle size is pre-oxidized to improve the structural stability and the cycle stability. The pretreated precursors with two different sizes are mixed with lithium and sintered according to a certain proportion, and the quaternary anode material with higher compaction density and better comprehensive performance can be obtained.

Description

Modified NCMA quaternary anode material and preparation method thereof
Technical Field
The invention belongs to the technical field of battery materials, and particularly relates to a modified NCMA quaternary anode material and a preparation method thereof.
Background
With the rapid development of new energy automobile industry, the energy density of the current commercial anode material is difficult to meet the high requirement of people on endurance mileage, so that it is necessary to deeply research and develop an anode material with higher energy density, wherein the high nickel layered material is widely concerned. The main current high nickel materials are mainly lithium nickel cobalt aluminum oxide (NCA, LiNi)xCoyAl1-x-yO2) And lithium nickel cobalt manganese oxide (NCM, LiNi)xCoyMn1-x-yO2) Two types are provided. In fact, these two transition metal oxides can also be considered as Co, Mn and Co, Al doped LiNiO2A material. As the nickel content in the material increases, the components of the NCM and NCA materials are closer to LiNiO2Therefore, the two high nickel ternary materials are more to some extentExhibit LiNiO2Such as Li/Ni mixed rows, Ni3+Instability, low coulombic efficiency, thermal instability, multiphase transition during cycling, etc. The high-nickel NCM positive electrode material has the specific characteristics of poor safety performance, poor thermal stability and poor cycle performance; the high-nickel NCA anode material has poor first effect and poor cycle performance, and at present, the domestic battery manufacturers have no capacity of directly applying the high-nickel NCA to power batteries. In recent years, researchers have found that Al doping improves the thermal stability and cycle performance of high-nickel NCM anodes, and during the preparation process, Al, Ni, Co, and Mn cations maintain uniform distribution of spherical particles during the Co-precipitation process, which is called a nickel-cobalt-manganese-aluminum (NCMA) quaternary system. In the system, the doping of Al reduces the volume change of lithium ions in the positive electrode material de-intercalation process, effectively inhibits the occurrence and expansion of microcracks in secondary particles and shows good physical and chemical properties. Although the high-nickel NCMA quaternary positive electrode material integrates partial advantages of NCM and NCA, the cycle stability and the like of the high-nickel NCMA quaternary positive electrode material still need to be improved.
At present, the modification method for the NCMA material is similar to that of the traditional high-nickel ternary material, and mainly comprises doping, cladding and the like. As disclosed in patent application publication No. CN111916687A, a boron-tungsten co-doped and fast ion conductor coated NCMA quaternary positive electrode material and a preparation method thereof are provided, the method includes the following steps: 1) Preparing a nickel-cobalt-manganese-aluminum precursor by a coprecipitation method; 2) Preparing boron-tungsten co-doped nickel cobalt manganese lithium aluminate; 3) Preparation of Li6.5Y0.5Zr1.5O7A coating material; 4) And mechanically mixing the doped lithium nickel cobalt manganese aluminate and a coating layer material, and sintering to obtain the quaternary anode material.
Patent publication No. CN111422919A proposes an aluminum and zirconium co-doped and boron-coated NCMA quaternary positive electrode material. In the quaternary anode material, aluminum and zirconium are codoped to have a good synergistic effect, so that the structural stability of a matrix can be better improved, the specific surface area of the material can be effectively reduced through boron coating, and the electrochemical performance of the quaternary anode material is improved.
In fact, the modification methods for polycrystalline materials also include grading.
For example, patent publication No. CN109888235A discloses a method for grading high nickel polycrystal and high nickel monocrystal materials. The method comprises the following steps: 1) Mixing a high-nickel polycrystalline precursor, anhydrous LiOH and a doping additive, sintering, mixing the obtained product with a coating additive, and sintering to obtain a high-nickel polycrystalline material; 2) Mixing the ternary single crystal precursor, a lithium source and a doping additive, sintering, mixing the obtained product with a coating additive, and sintering to obtain a ternary single crystal material; 3) Mixing the high-nickel polycrystalline material with the ternary single crystal material, or mixing the mixture with the coating additive and then sintering.
The invention patent with publication number CN104724763A provides a preparation method of a high-compaction positive electrode material, which comprises the following steps: uniformly mixing large and small precursors with different particle sizes, wherein the particle size of large particles is more than or equal to 10 mu m and less than or equal to D50 and less than or equal to 15 mu m, the particle size of small particles is more than or equal to 4 mu m and less than or equal to D50 and less than or equal to 7 mu m, and then mixing the precursor with Li2CO3Mixing uniformly and sintering; then the precursor with the diameter of 10 mu m and the diameter of D50 which are less than or equal to 12 mu m and Li2CO3Uniformly mixing and sintering the mixture into a single crystal material, and mixing the two sintered materials.
For the NCMA polycrystalline material, if the secondary particle size is larger, the circulation stability is better, and the capacity and rate capability are poorer; if the secondary particle size is small, the capacity and rate capability of the material can be improved to some extent, but the cycle stability is also poor. On the other hand, if the two anode materials are separately prepared and then graded, the process involved in the large-scale production process is complicated, the material mixing times are many, and the utilization rate of a sintering kiln is low. In addition, the loose packing density of the small-particle precursor is low, and the loading amount is small, so that the sintering process is low in efficiency and high in cost.
Disclosure of Invention
Aiming at the problems in the prior art, the invention aims to provide a modified NCMA quaternary positive electrode material and a preparation method thereof.
In order to solve the technical problems, the invention adopts the following technical scheme.
Firstly, the invention provides a modified NCMA quaternary anode material, which is formed by sintering two precursors with different secondary particle sizes after grading; before grading, the two precursors are pretreated.
Pre-treating the precursor, including in-situ coating the precursor with larger particle size to improve the rate capability and capacity; the precursor with smaller particle size is pre-oxidized to improve the structural stability and the cycle stability.
The pretreated precursors with two different sizes are mixed with lithium and sintered according to a certain proportion, and the quaternary anode material with higher compaction density and better comprehensive performance can be obtained.
Based on the same inventive concept, the invention provides a preparation method of the modified NCMA quaternary positive electrode material, which comprises the following steps:
step S1, preparing to obtain SiO2And (3) in-situ coated high-nickel NCMA quaternary precursor.
Adding a large-particle high-nickel NCMA quaternary precursor, tetraethoxysilane TEOS and deionized water into absolute ethyl alcohol for mixing to obtain a mixture A; the particle size Dv50 value of the large-particle precursor is 8-16 mu m;
stirring the mixture A for 1-50 h at the temperature of 20-80 ℃, then continuously heating and stirring at the temperature of 20-100 ℃ until the solvent is completely evaporated to obtain NixCoyMnzAl(1-x-y-z)(OH)2@SiO2And (3) precursor.
Step S2, pre-oxidizing small-grained high-nickel NiaCobMncAl(1-a-b-c)(OH)2And (3) precursor.
Placing a small-particle high-nickel NCMA quaternary precursor into deionized water to obtain a mixture B, and adding Na2S2O8Mixing the mixed solution C with NaOH to obtain a mixed solution C, pouring the mixed solution C into the mixture B while stirring until the pH value of the system reaches 9-13, controlling the temperature of the solution to be 25-100 ℃ while stirring, washing and drying precipitates after stirring for a certain time to obtain a pre-oxidized NCMA quaternary precursor; the particle size Dv50 value of the small-particle precursor is 2-6 μm.
And step S3, mixing the two precursors pretreated in the step S1 and the step S2 according to a certain mass ratio to obtain the precursor after grading.
And step S4, uniformly mixing the precursor subjected to grading in the step S3 with a lithium source and an additive, and sintering in an oxygen atmosphere to obtain the modified NCMA quaternary positive electrode material.
Further, in the above preparation method, the contents of the respective elements of the large-particle high-nickel NCMA quaternary precursor and the small-particle high-nickel NCMA quaternary precursor may be the same or different.
Further, in the preparation method, in step S1, the molar ratio of the addition amount of tetraethoxysilane TEOS to the large-particle high-nickel NCMA precursor is f, and f is between 0.1% and 10%; the mass ratio of the added deionized water to the large-particle high-nickel NCMA precursor is g, wherein g is more than or equal to 0 and less than or equal to 5; the volume ratio of the addition amount of the absolute ethyl alcohol to the deionized water is h, and h is more than or equal to 10 and less than or equal to 200.
Further, in the preparation method, in step S2, the mass ratio of the deionized water in the mixture B to the small-particle high-nickel NCMA precursor is i, i is greater than or equal to 0 and less than or equal to 10, and Na in the mixed solution C2S2O8The molar ratio of the NaOH to the water is j, and j is more than or equal to 0.1 and less than or equal to 10.
Further, in the above production method, in step S3, SiO2The mass ratio of the in-situ coated large-particle high-nickel NCMA quaternary precursor to the pre-oxidized small-particle high-nickel NCMA quaternary precursor is (10-x): x, wherein x is less than or equal to 5.
Further, in the above preparation method, the lithium source in step S4 is LiOH. H2O、LiOH、Li2O or Li2CO3The additive is one or more of oxides of Zr and Sr.
Further, in the above preparation method, the sintering temperature in step S4 is 600-900 ℃, and the sintering time is 8-20 h.
The invention provides a preparation method of a modified NCMA quaternary anode material,
(1) SiO is carried out on the large-particle high-nickel NCMA precursor in the preparation process2In-situ coating treatment and mixingDuring the lithium sintering process, uniform Li can be generated in situ4SiO4A coating layer of SiO4 4-The tetrahedral anion can provide Li benefits+Three-dimensional channels of migration, effectively enhancing Li+The rate capability of the large-particle NCMA material can be better improved by conduction at the electrode/electrolyte interface.
(2) The small-particle high-nickel NCMA precursor is subjected to pre-oxidation treatment in the preparation process, so that the average oxidation valence state of nickel ions in the precursor is improved, and Ni is reduced2+With Li+The interlayer structure collapse phenomenon caused by blending is adopted, so that the structural stability of the small-particle NCMA material is improved, and the cycle stability of the small-particle NCMA material is improved.
The two defects can be effectively improved by simply preprocessing the precursors with two particle sizes, the comprehensive performance of the graded anode material can be effectively improved compared with the direct grading, and the preparation process is simple and suitable for large-scale production.
The NCMA positive electrode material is prepared by grading and sintering two pretreated high-nickel polycrystalline precursors, on one hand, compared with grading and sintering after sintering respectively, the grading and sintering after grading of the two precursors can greatly reduce preparation procedures, improve the utilization rate of equipment and reduce the preparation cost in the actual production process; meanwhile, the grading can improve the overall tap density of the precursor, is beneficial to improving the productivity in the subsequent sintering process and reducing the energy consumption. On the other hand, the process can remarkably increase the compaction density of the cathode material and improve the energy density of the battery.
Drawings
Fig. 1 is an SEM image of the NCMA quaternary positive electrode material prepared in example 1 of the present invention.
FIG. 2 is a graph showing the cycle performance at 45 ℃ and 4.35V of the NCMA quaternary material prepared in example 1, comparative example 1 and comparative example 2 of the present invention.
Detailed Description
The present invention will now be described in detail with reference to the drawings, which are given by way of illustration and explanation only and should not be construed to limit the scope of the present invention in any way. Furthermore, those skilled in the art can combine features from the embodiments of this document and from different embodiments accordingly based on the description of this document.
Example 1
Preparing an NCMA quaternary cathode material:
step 1, high-nickel polycrystalline Ni with Dv50 of 11.5 mu m0.90Co0.05Mn0.04Al0.01(OH)2Precursor, tetraethoxysilane Si (OC)2H5)4Mixing according to a molar ratio of 1.0:0.03, and adding the mixture into a mixed solution of absolute ethyl alcohol and deionized water for dissolving to obtain a mixed solution A. Wherein the mass ratio of the deionized water to the precursor is 2: 5; the volume ratio of the deionized water to the ethanol is 2: 50.
Step 2, stirring the mixed solution A at 50 ℃ for 5h, and then continuing stirring at 80 ℃ until the solution is completely evaporated to obtain large-particle Ni0.90Co0.05Mn0.04Al0.01(OH)2@SiO2The precursor is numbered Lp.
Step 3, preparing high nickel polycrystalline Ni with Dv50 of 3.5 mu m0.90Co0.05Mn0.04Al0.01(OH)2Adding the precursor into deionized water to prepare slurry B, wherein the weight ratio of the precursor to the deionized water is 1: 5; 2 mol/L of Na2S2O8The volume ratio of the solution to 4mol/L NaOH solution is 1: 1 to prepare a mixed solution C.
And 4, slowly adding the mixed solution C into the slurry B, and stirring until the pH value of the solution is 11.5, wherein the system temperature is 50 ℃ during stirring, and the stirring time is 5 hours. Centrifugally drying the stirred mixed slurry to obtain small Ni particles subjected to pre-oxidation treatment0.90Co0.05Mn0.04Al0.01(OH)2Precursor, number Sp.
And 5, according to the ratio of 7: 3, and mixing the precursor after grading with LiOH & H2O, additive ZrO2And an additive SrO. The amount of Zr added was 3000 ppm and the amount of Sr added was 2000 ppm, based on 100% of the total mass of the finally obtained positive electrode material. Mixing the above materials at high speedMixing in a mixer, and sintering in oxygen atmosphere with oxygen content greater than 95%. Wherein the heating rate is 2 ℃/min, the temperature is increased to 740 ℃, and the constant temperature is kept for 12 h.
And 6, carrying out vibration screening and iron removal treatment on the sintered material to obtain the NCMA quaternary anode material.
Fig. 1 is an SEM image of the NCMA quaternary positive electrode material prepared in example 1 of the present invention. As can be seen from the figure, the prepared quaternary anode material has complete surface appearance, and the coating effect is better. In the figure, the surface of the small-particle polycrystalline particles has no obvious change, which shows that the preoxidation treatment has no obvious influence on the surface appearance, and in addition, the small particles have a slight agglomeration phenomenon, are filled in gaps among large particles and have a great contribution to improving the compaction density.
Comparative example 1
High nickel polycrystalline Ni with Dv50 of 11.5 μm0.90Co0.05Mn0.04Al0.01(OH)2Precursor and high nickel polycrystalline Ni with Dv50 of 3.5 mu m0.90Co0.05Mn0.04Al0.01(OH)2The precursor is 7: 3, mixing uniformly.
The precursor after grading is mixed with LiOH H2O, additive ZrO2And an additive SrO are mixed according to a certain proportion. The amount of Zr added was 3000 ppm and the amount of Sr added was 2000 ppm, based on 100% of the total mass of the finally obtained positive electrode material. The materials are uniformly mixed in a high-speed mixer, and the mixture is sintered in an oxygen atmosphere with the oxygen content of more than 95 percent. Wherein the heating rate is 2 ℃/min, the temperature is increased to 740 ℃, and the constant temperature is kept for 12 h.
And (4) vibrating and screening the sintered material, and removing iron to obtain the precursor graded sintered NCMA quaternary anode material.
Comparative example 2
High nickel polycrystalline Ni with Dv50 of 11.5 μm0.90Co0.05Mn0.04Al0.01(OH)2Precursor, tetraethoxysilane Si (OC)2H5)4Mixing at a molar ratio of 1.0:0.03, adding into anhydrous ethanol, and removingDissolving in the mixed solution of water to obtain mixed solution A. Wherein the mass ratio of the deionized water to the precursor is 2: 5; the volume ratio of the deionized water to the ethanol is 2: 50.
Stirring the mixed solution A at 50 ℃ for 5h, and then continuing stirring at 80 ℃ until the solution is completely evaporated to obtain large-particle Ni0.90Co0.05Mn0.04Al0.01(OH)2@SiO2The precursor is numbered Lp.
High nickel polycrystalline Ni with precursors Lp and Dv50 of 3.5 μm0.90Co0.05Mn0.04Al0.01(OH)2The precursor is 7: 3, uniformly mixing the precursor after grading with LiOH & H2O, additive ZrO2And an additive SrO are mixed according to a certain proportion. The amount of Zr added was 3000 ppm and the amount of Sr added was 2000 ppm, based on 100% of the total mass of the finally obtained positive electrode material. The materials are uniformly mixed in a high-speed mixer, and the mixture is sintered in an oxygen atmosphere with the oxygen content of more than 95 percent. Wherein the heating rate is 2 ℃/min, the temperature is increased to 740 ℃, and the constant temperature is kept for 12 h.
And (3) vibrating and screening the sintered material, and removing iron to obtain the NCMA quaternary anode material.
Comparative example 3
High nickel polycrystalline Ni with Dv50 of 11.5 μm0.90Co0.05Mn0.04Al0.01(OH)2Precursor, tetraethoxysilane Si (OC)2H5)4Mixing according to a molar ratio of 1.0:0.03, and adding the mixture into a mixed solution of absolute ethyl alcohol and deionized water for dissolving to obtain a mixed solution A. Wherein the mass ratio of the deionized water to the precursor is 2: 5; the volume ratio of the deionized water to the ethanol is 2: 50. Stirring the mixed solution A at 50 ℃ for 5h, and then continuing stirring at 80 ℃ until the solution is completely evaporated to obtain large-particle Ni0.90Co0.05Mn0.04Al0.01(OH)2@SiO2The precursor is numbered Lp.
The precursor Lp is reacted with LiOH H2O, additive ZrO2And an additive SrO are mixed according to a certain proportion. With the finally obtained positive electrodeThe total mass of the material is 100%, the addition amount of Zr element is 3000 ppm, and the addition amount of Sr element is 2000 ppm. The materials are uniformly mixed in a high-speed mixer, and the mixture is sintered in an oxygen atmosphere with the oxygen content of more than 95 percent. Wherein the heating rate is 2 ℃/min, the temperature is increased to 740 ℃, and the constant temperature is kept for 12 h.
High nickel polycrystalline Ni with Dv50 of 3.5 μm0.90Co0.05Mn0.04Al0.01(OH)2Adding the precursor into deionized water to prepare slurry B, wherein the weight ratio of the precursor to the deionized water is 1: 5; 2 mol/L of Na2S2O8The volume ratio of the solution to 4mol/L NaOH solution is 1: 1 to prepare a mixed solution C. And slowly adding the mixed solution C into the slurry B, and stirring until the pH value of the reaction system is 11.5, wherein the temperature of the system is 50 ℃ during stirring, and the stirring time is 5 hours. Centrifugally drying the stirred mixed slurry to obtain small Ni particles subjected to pre-oxidation treatment0.90Co0.05Mn0.04Al0.01(OH)2Precursor, number Sp.
Reacting the precursor Sp with LiOH. H2O, additive ZrO2And an additive SrO are mixed according to a certain proportion. The amount of Zr added was 3000 ppm and the amount of Sr added was 2000 ppm, based on 100% of the total mass of the finally obtained positive electrode material. The materials are uniformly mixed in a high-speed mixer, and the mixture is sintered in an oxygen atmosphere with the oxygen content of more than 95 percent. Wherein the heating rate is 2 ℃/min, the temperature is increased to 740 ℃, and the constant temperature is kept for 12 h.
And (3) sintering the large-particle positive electrode material and the small-particle positive electrode material according to the weight ratio of 7: and 3, grading, and then performing vibration screening and iron removal treatment to obtain the NCMA quaternary anode material.
Comparative example 1 differs from example 1 in that comparative example 1 did not pretreat the two precursors separately.
Comparative example 2 differs from example 1 in that comparative example 2 does not subject the small particle precursor to a pre-oxidation treatment.
The difference between comparative example 3 and example 1 is that comparative example 3 performs gradation after the precursor is pretreated and prepared as a positive electrode material, respectively.
The apparent density and productivity of the quaternary positive electrode materials prepared in example 1, comparative example 2, and comparative example 3 were further compared, and the results are shown in table 1.
TABLE 1 comparison of bulk density and theoretical pot loading and capacity
Figure 197532DEST_PATH_IMAGE001
Meanwhile, the quaternary positive electrode materials respectively prepared in example 1, comparative example 2 and comparative example 3 were assembled into button cells according to the same conventional method in the art, and the performance parameters of the cells were tested, with the results shown in table 2.
TABLE 2 compacted density and piezoelectric Properties of the finished products
Figure 541051DEST_PATH_IMAGE002
From table 1, after the precursors with two sizes are pretreated and graded, the overall bulk density is slightly less than that of the large-particle precursor, but is obviously improved compared with that of the small-particle precursor. The reason is that the small-particle precursor occupies the gaps among the large-particle precursors after grading, but the bulk density of the small-particle precursor is lower, so that the bulk density of the whole precursor after grading is slightly lower than that of the large-particle precursor. Compared with the yield of the kiln, the yield of a single kiln in the embodiment 1 is improved by about 5% compared with that of the comparative example 3 due to the improvement of the pot loading amount, and the yield is improved by far more than 5% if the yields of all the processes are all integrated and calculated. This shows that the precursor grading in example 1 has a greater advantage than the positive grading in comparative example 3.
From the point of view of compaction density and piezoelectric property, the compaction density is relatively close. However, the rate performance and the cycle retention rate of example 1 are both significantly better than those of comparative examples 1 and 2, and the accompanying drawing 2 can be referred to. On one hand, after the large particle precursor is coated in situ, the surface is generated uniformlyLi of (2)4SiO4A coating layer of SiO4 4-The tetrahedral anion can provide Li benefits+Three-dimensional channels of migration, effectively enhancing Li+The rate performance of the large-particle NCMA material can be better improved by conduction at an electrode/electrolyte interface; on the other hand, after the small-particle NCMA precursor is subjected to pre-oxidation treatment, the average oxidation valence of nickel ions in the precursor is increased, and Ni2+Is greatly reduced, therefore Ni2+With Li+The interlayer structure collapse phenomenon caused by blending is obviously improved, and the structural stability of the small-particle NCMA material is obviously improved. By respectively pretreating the precursors of the large and small particles, the rate capability and the cycling stability of the NCMA anode material are obviously improved. The data of the comparative example 3 and the example 1 are not obviously different, and the sintering after pole matching has no influence on the material performance.
Example 2
High nickel polycrystalline Ni with Dv50 of 14 μm0.92Co0.05Mn0.02Al0.01(OH)2Precursor, tetraethoxysilane Si (OC)2H5)4Mixing according to a molar ratio of 1.0:0.03, and adding the mixture into a mixed solution of absolute ethyl alcohol and deionized water for dissolving to obtain a mixed solution A. Wherein the mass ratio of the deionized water to the precursor is 2: 5; the volume ratio of the deionized water to the ethanol is 2: 50.
Stirring the mixed solution A at 50 ℃ for 5h, and then continuing stirring at 80 ℃ until the solution is completely evaporated to obtain large-particle Ni0.92Co0.05Mn0.02Al0.01(OH)2@SiO2The precursor is numbered Lp.
High nickel polycrystalline Ni with Dv50 of 3.5 μm0.88Co0.06Mn0.05Al0.01(OH)2Adding the precursor into deionized water to prepare slurry B, wherein the weight ratio of the precursor to the deionized water is 1: 5; 2 mol/L of Na2S2O8The volume ratio of the solution to 4mol/L NaOH solution is 1: 1 to prepare a mixed solution C.
Slowly adding the mixed solution C into the slurry B, and stirring until the pH value of the solution is 11.5 while stirringThe temperature of the system is 50 ℃, and the stirring time is 5 h. Centrifugally drying the stirred mixed slurry to obtain small Ni particles subjected to pre-oxidation treatment0.88Co0.06Mn0.05Al0.01(OH)2Precursor, number Sp.
And (3) mixing the precursor Lp and the precursor Sp according to the ratio of 7: 3, and mixing the precursor after grading with LiOH & H2O, additive ZrO2And an additive SrO are mixed according to a certain proportion. The amount of Zr added was 3000 ppm and the amount of Sr added was 2000 ppm, based on 100% of the total mass of the finally obtained positive electrode material. The materials are uniformly mixed in a high-speed mixer, and the mixture is sintered in an oxygen atmosphere with the oxygen content of more than 95 percent. Wherein the heating rate is 2 ℃/min, the temperature is increased to 730 ℃, and the constant temperature is kept for 12 h.
And (3) vibrating and screening the sintered material, and removing iron to obtain the modified NCMA quaternary anode material.
Table 3 example 2 finished product compacted density and fastening performance
Figure 936260DEST_PATH_IMAGE003
As shown in Table 3, the present invention can also achieve excellent performance when applied to the case where the precursor components are different and the difference in the particle size of the precursor is larger.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims (10)

1. A modified NCMA quaternary positive electrode material is prepared by grading and sintering two precursors with different secondary particle sizes; the method is characterized in that before grading, two precursors are respectively pretreated: and carrying out in-situ coating treatment on the precursor with larger particle size, and carrying out pre-oxidation treatment on the precursor with smaller particle size.
2. A preparation method of a modified NCMA quaternary positive electrode material is characterized by comprising the following steps:
step S1, SiO2Coating a large-particle high-nickel NCMA quaternary precursor in situ;
step S2, pre-oxidizing a small-particle high-nickel NCMA quaternary precursor;
step S3, the SiO in step S12Mixing the in-situ coated large-particle high-nickel NCMA quaternary precursor and the pre-oxidized small-particle high-nickel NCMA quaternary precursor in the step S2 according to a certain mass ratio to obtain a graded precursor;
and step S4, uniformly mixing the precursor subjected to grading in the step S3 with a lithium source and an additive, and sintering in an oxygen atmosphere to obtain the modified NCMA quaternary positive electrode material.
3. The method according to claim 2, wherein the particle size Dv50 value of the large-particle high-nickel NCMA quaternary precursor is 8 to 16 μm, and the particle size Dv50 value of the small-particle high-nickel NCMA quaternary precursor is 2 to 6 μm.
4. The method of claim 2 or 3, wherein the high nickel NCMA quaternary precursor has the formula NixCoyMnzAl(1-x-y-z)(OH)2Wherein x is more than or equal to 0.85 and less than or equal to 0.95, y is more than or equal to 0.04 and less than or equal to 0.10, z is more than or equal to 0.03 and less than or equal to 0.11, and 0 is more than or equal to 1-x-y-z and less than or equal to 0.08; the contents of the elements in the large-particle high-nickel NCMA quaternary precursor and the small-particle high-nickel NCMA quaternary precursor may be the same or different.
5. The method according to claim 4,
the specific process of step S1 is: adding a large-particle high-nickel NCMA precursor, tetraethoxysilane TEOS and deionized water into absolute ethyl alcohol for mixing to obtain a mixture A; stirring the mixture A for 1-50 h at the temperature of 20-80 ℃, and then continuously heating and stirring at the temperature of 20-100 ℃ until the solvent is completely evaporatedThen, SiO is obtained2In-situ coated large-particle high-nickel NCMA quaternary precursor;
the specific process of step S2 is: placing a small-particle high-nickel NCMA quaternary precursor into deionized water to obtain a mixture B, and adding Na2S2O8And (3) mixing the mixed solution C with a NaOH solution to obtain a mixed solution C, slowly pouring the mixed solution C into the mixture B while stirring until the pH value of the system reaches q, q is more than or equal to 9 and less than or equal to 13, controlling the stirring temperature to be 25-100 ℃, and washing and drying the precipitate after stirring for a certain time to obtain the small-particle high-nickel NCMA quaternary precursor.
6. The method of claim 5, wherein in step S1, the molar ratio of the amount of tetraethylorthosilicate TEOS added to the large-particle, high-nickel NCMA precursor is f, 0.1% to 10%; the mass ratio of the added deionized water to the large-particle high-nickel NCMA precursor is g, wherein g is more than or equal to 0 and less than or equal to 5; the volume ratio of the addition amount of the absolute ethyl alcohol to the deionized water is h, and h is more than or equal to 10 and less than or equal to 200.
7. The method of claim 5, wherein in step S2, the mass ratio of the deionized water to the small-particle high-nickel NCMA precursor in the mixture B is i, i is greater than or equal to 0 and less than or equal to 10; NaOH and Na in the mixed solution C2S2O8The molar ratio of j is more than or equal to 0.1 and less than or equal to 10.
8. The method of claim 2, wherein in step S3, SiO2The mass ratio of the in-situ coated large-particle high-nickel NCMA quaternary precursor to the pre-oxidized small-particle high-nickel NCMA quaternary precursor is (10-x): x, wherein x is less than or equal to 5.
9. The method of claim 2, wherein the lithium source of step S4 is LiOH-H2O、LiOH、Li2O or Li2CO3The additive is one or more of oxides of Zr and Sr.
10. The method as claimed in claim 2, wherein the sintering temperature in step S4 is 600-900 ℃ and the sintering time is 8-20 h.
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CN104362334A (en) * 2014-11-26 2015-02-18 中国科学院大学 Preparation method of lithium metasilicate coated lithium-enriched laminar positive electrode material of lithium ion battery
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