CN115140782A - Lithium-rich manganese-based positive electrode material precursor with core-shell structure and preparation method thereof - Google Patents
Lithium-rich manganese-based positive electrode material precursor with core-shell structure and preparation method thereof Download PDFInfo
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- 239000002243 precursor Substances 0.000 title claims abstract description 54
- 239000011572 manganese Substances 0.000 title claims abstract description 48
- 229910052748 manganese Inorganic materials 0.000 title claims abstract description 41
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 37
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 title claims abstract description 37
- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 37
- 239000007774 positive electrode material Substances 0.000 title claims abstract description 34
- 239000011258 core-shell material Substances 0.000 title claims abstract description 19
- 238000002360 preparation method Methods 0.000 title claims abstract description 8
- 239000008139 complexing agent Substances 0.000 claims abstract description 19
- 239000000654 additive Substances 0.000 claims abstract description 18
- 230000000996 additive effect Effects 0.000 claims abstract description 18
- 239000007788 liquid Substances 0.000 claims abstract description 18
- 239000012716 precipitator Substances 0.000 claims abstract description 15
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims abstract description 12
- 238000000975 co-precipitation Methods 0.000 claims abstract description 12
- 229910052751 metal Inorganic materials 0.000 claims abstract description 12
- 239000002184 metal Substances 0.000 claims abstract description 12
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 8
- 239000000126 substance Substances 0.000 claims abstract description 5
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims abstract description 4
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 claims abstract description 4
- 235000011114 ammonium hydroxide Nutrition 0.000 claims abstract description 4
- 238000001035 drying Methods 0.000 claims abstract description 4
- 239000011261 inert gas Substances 0.000 claims abstract description 4
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 4
- 238000005406 washing Methods 0.000 claims abstract description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 4
- 238000006243 chemical reaction Methods 0.000 claims description 62
- 239000012792 core layer Substances 0.000 claims description 29
- 239000010410 layer Substances 0.000 claims description 28
- 238000000034 method Methods 0.000 claims description 16
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 14
- 229910021529 ammonia Inorganic materials 0.000 claims description 7
- KZOJQMWTKJDSQJ-UHFFFAOYSA-M sodium;2,3-dibutylnaphthalene-1-sulfonate Chemical compound [Na+].C1=CC=C2C(S([O-])(=O)=O)=C(CCCC)C(CCCC)=CC2=C1 KZOJQMWTKJDSQJ-UHFFFAOYSA-M 0.000 claims description 6
- 239000002002 slurry Substances 0.000 claims description 5
- 239000002131 composite material Substances 0.000 claims description 3
- 238000003756 stirring Methods 0.000 claims description 3
- DBMJMQXJHONAFJ-UHFFFAOYSA-M Sodium laurylsulphate Chemical compound [Na+].CCCCCCCCCCCCOS([O-])(=O)=O DBMJMQXJHONAFJ-UHFFFAOYSA-M 0.000 claims description 2
- CXDBXTHJTZQPOJ-UHFFFAOYSA-M [Na+].CC=C.CC=C.CC=C.CC=C.[O-]S(=O)(=O)C1=CC=CC=C1 Chemical compound [Na+].CC=C.CC=C.CC=C.CC=C.[O-]S(=O)(=O)C1=CC=CC=C1 CXDBXTHJTZQPOJ-UHFFFAOYSA-M 0.000 claims description 2
- GVGUFUZHNYFZLC-UHFFFAOYSA-N dodecyl benzenesulfonate;sodium Chemical compound [Na].CCCCCCCCCCCCOS(=O)(=O)C1=CC=CC=C1 GVGUFUZHNYFZLC-UHFFFAOYSA-N 0.000 claims description 2
- 229940080264 sodium dodecylbenzenesulfonate Drugs 0.000 claims description 2
- 239000010405 anode material Substances 0.000 abstract description 6
- 238000009792 diffusion process Methods 0.000 abstract description 4
- 150000002500 ions Chemical class 0.000 abstract description 4
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonium chloride Substances [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 abstract 1
- 230000000052 comparative effect Effects 0.000 description 18
- 239000002245 particle Substances 0.000 description 10
- 230000001276 controlling effect Effects 0.000 description 6
- 239000011164 primary particle Substances 0.000 description 4
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 3
- 229910001416 lithium ion Inorganic materials 0.000 description 3
- 238000001000 micrograph Methods 0.000 description 3
- FKNQFGJONOIPTF-UHFFFAOYSA-N Sodium cation Chemical compound [Na+] FKNQFGJONOIPTF-UHFFFAOYSA-N 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 239000010406 cathode material Substances 0.000 description 2
- 230000002349 favourable effect Effects 0.000 description 2
- 238000011056 performance test Methods 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 229910001415 sodium ion Inorganic materials 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 238000000635 electron micrograph Methods 0.000 description 1
- 230000002427 irreversible effect Effects 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 231100000956 nontoxicity Toxicity 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
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- H01M10/05—Accumulators with non-aqueous electrolyte
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- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
- H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
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Abstract
A lithium-rich manganese-based anode material precursor with a core-shell structure, the chemical formula of which is Ni x Mn y (OH) 2 The preparation method comprises the following steps: 1. preparing Ni and Mn metal liquid; preparing sodium hydroxide or potassium hydroxide solution as a precipitator; preparing an ammonia solution as a complexing agent; preparing an additive solution; 2. adding pure water, a precipitator and a complexing agent into the kettle to prepare a base solution; 3. introducing nitrogen or inert gas, and continuously adding the metal liquid, the precipitator, the complexing agent and the additive solution into the kettle for coprecipitation; stopping feeding liquid when the granularity grows to 60-80% of the target granularity; reducing the temperature to 55 to 65 ℃, continuously adding the metal liquid, the precipitator and the complexing agent into the kettle for continuous coprecipitation,stopping feeding liquid when the granularity grows to the target granularity; 4. and centrifuging, washing and drying the product to obtain the lithium-rich manganese-based positive electrode material precursor with the core-shell structure. The precursor has stable structure and higher ion diffusion coefficient, and can improve the electrical property of the anode material.
Description
Technical Field
The invention relates to the technical field of lithium ion battery anode materials, in particular to a lithium-rich manganese-based anode material precursor with a core-shell structure and a preparation method thereof.
Background
The lithium-rich manganese-based material has the advantages of low cost, high capacity, no toxicity, safety and the like, and can meet the use requirements of power batteries in the fields of electric vehicles and the like when being used as a positive electrode material.
The specific discharge capacity of the lithium-rich manganese-based positive electrode material reaches more than 300mAh/g, so the lithium-rich manganese-based positive electrode material is considered to be an ideal choice for a new generation of high-energy-density power battery in the future. However, the lithium-rich manganese-based positive electrode material has a low ion diffusion coefficient, so that the rate performance and cycle performance of the lithium-rich manganese-based positive electrode material are poor, and the requirements of a power battery cannot be met. In addition, the lithium-rich manganese-based positive electrode material is easy to generate phase change in the process of charging and discharging, so that the irreversible capacity is improved, and the electrical property is reduced.
Therefore, how to prepare a lithium-rich manganese-based positive electrode material precursor with stable structure and high ion diffusion coefficient to improve the electrical property of the corresponding positive electrode material becomes a subject to be researched by the invention.
Disclosure of Invention
The invention aims to provide a lithium-rich manganese-based positive electrode material precursor with a core-shell structure and a preparation method thereof.
In order to achieve the purpose, the technical scheme adopted by the invention on the product level is as follows:
a lithium-rich manganese-based anode material precursor with a core-shell structure, and the chemical formula isNi x Mn y (OH) 2 Wherein x is more than or equal to 0.30 and less than 0.40, and y is more than or equal to 0.60 and less than 0.70.
The relevant content in the above technical solution is explained as follows:
1. in the scheme, the composite material comprises a core layer and a shell layer, wherein the porosity of the core layer is 40-60%, and the D50 of the core layer is 1 Accounting for 60-80% of the precursor D50; the porosity of the shell layer is 5-8%, and the D50 of the shell layer 2 The ratio of the porosity of the core layer to the porosity of the shell layer is 5.
2. In the scheme, the D50 is 4-7 um, and the tap density is 1.20-1.60 g/cm 3 The specific surface area is 70 to 90m 2 /g。
In order to achieve the purpose, the technical scheme adopted by the invention in the aspect of the method is as follows:
a preparation method of a lithium-rich manganese-based positive electrode material precursor with a core-shell structure comprises the following steps:
step one, preparing Ni and Mn metal liquid with the molar concentration of 1.8-2.2 mol/L;
preparing sodium hydroxide or potassium hydroxide solution with the molar concentration of 8-10 mol/L as a precipitator;
preparing ammonia water solution with the molar concentration of 2-4 mol/L as a complexing agent;
preparing an additive solution with the mass percentage of 1-3%;
step two, adding pure water, the precipitator and the complexing agent into a closed reaction kettle to prepare a base solution, controlling the pH value of the base solution to be 11.5-12.1 through the precipitator, controlling the ammonia concentration in the base solution to be 0.05-0.25 mol/L through the complexing agent, and maintaining the temperature of the base solution at 75-85 ℃;
step three, keeping the stirring of the reaction kettle open, introducing nitrogen or inert gas with the flow of 0.5-0.8 m 3 Step one, continuously adding the metal liquid, the precipitator, the complexing agent and the additive solution in the step one into a reaction kettle at the flow rate of 50-400L/min respectively to perform coprecipitation reaction; the pH value is maintained at 11.5-12.1 in the reaction process, the reaction temperature is maintained at 75-85 ℃, the rotating speed of the reaction kettle is 600-700 r/min, and the reaction is carried outSlurry particle size D50 in reactor 1 Stopping feeding liquid when the particle size grows to 60-80% of the target particle size D50;
reducing the temperature of a reaction kettle to 55-65 ℃, continuously adding the metal liquid, the precipitator and the complexing agent in the step one into the reaction kettle at the flow rate of 50-400L/min respectively to continue coprecipitation reaction, wherein the pH value is maintained at 11.5-12.1 in the reaction process, the reaction temperature is maintained at 55-65 ℃, the rotating speed of the reaction kettle is 500-600 r/min, and the liquid feeding is stopped when the granularity of the slurry in the reaction kettle reaches a target granularity D50;
and step four, centrifuging, washing and drying the coprecipitation product in the step three to obtain the lithium-rich manganese-based positive electrode material precursor with the core-shell structure.
The relevant content in the above technical solution is explained as follows:
1. in the above scheme, in the step one, the additive is one or more of sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, sodium tetrapropylene benzene sulfonate and sodium dibutyl naphthalene sulfonate.
2. In the scheme, in the third step, the mass percentage of the additive in the reaction kettle is 0.02-0.06%.
3. In the scheme, in the third step, the ammonia concentration is kept between 0.05 and 0.25mol/L in the reaction process.
4. In the above scheme, in step three, the target particle size D50 is 4 to 7um.
5. In the above scheme, in the fourth step, the chemical formula of the precursor is Ni x Mn y (OH) 2 Wherein x is more than or equal to 0.30 and less than 0.40, and y is more than or equal to 0.60 and less than 0.70.
6. In the scheme, the precursor comprises a core layer and a shell layer, the porosity of the core layer is 40-60%, and the D50 of the core layer is 1 Accounting for 60-80% of the precursor; the porosity of the shell layer is 5-8%, and the D50 of the shell layer 2 The precursor accounts for 20-40%, and the ratio of the porosity of the core layer to the porosity of the shell layer satisfies 5. The ratio of the porosity of the shell layer to the porosity of the shell layer satisfies 5;
the tap density of the precursor is 1.20-1.60 g/cm 3 Is toThe surface area is 70 to 90m 2 /g。
The working principle and the advantages of the invention are as follows:
1. the invention prepares the lithium-rich manganese-based anode material precursor with a core-shell structure by a coprecipitation method, wherein the porosity of a core layer is 40-60%, and the D50 of the core layer is 1 60-80% of the precursor, 5-8% of the porosity of the shell layer, and D50 of the shell layer 2 The precursor accounts for 20-40%, and the ratio of the porosity of the core layer to the porosity of the shell layer satisfies 5. The core with high porosity can increase the contact area with the electrolyte, improve the transmission efficiency of lithium ions, solve the problem of low ion diffusion coefficient of the lithium-rich manganese-based positive electrode material and improve the electrical property; the outer shell layer has lower porosity, the structure of the outer shell layer is more stable, structural change in the charge and discharge process is favorably relieved, and the structural stability in the charge and discharge process is improved. Furthermore, by precisely controlling the D50 of the nuclear layer 1 D50 with shell layer 2 The ratio of (a) to (b) achieves the purpose of regulating and controlling the high porosity region and the low porosity region, and improves the electrical performance.
2. In the process of preparing the precursor, the precursor of the lithium-rich manganese-based positive electrode material with the core-shell structure is prepared by adding the additive and regulating the reaction temperature. In the process of preparing the nuclear layer, the reaction temperature is maintained at 75-85 ℃, the rotating speed of the reaction kettle is 600-700 r/min, and simultaneously, the additive is added, so that the higher temperature is favorable for improving the reaction rate, accelerating the growth of crystals and facilitating the formation of pores; the high rotating speed can improve the dispersibility between the secondary balls, and the addition of the additive can prevent the adhesion between the primary particles and play a role in increasing the pores; in the process of preparing the shell layer, the reaction temperature is maintained at 55-65 ℃, the rotating speed of the reaction kettle is 500-600 r/min, no additive is added, the temperature is reduced to reduce the growth speed, the compactness among primary particles is improved, the structural stability is enhanced, and the cracking of secondary balls can be effectively prevented by reducing the rotating speed.
Drawings
FIG. 1 is a sectional electron microscope image of a precursor of a core-shell structure lithium-rich manganese-based positive electrode material prepared according to an embodiment of the invention;
FIG. 2 is a cross-sectional electron microscope image of a precursor of the core-shell structure lithium-rich manganese-based positive electrode material prepared in comparative example 1 of the present invention;
FIG. 3 is a cross-sectional electron microscope image of a precursor of the core-shell structure lithium-rich manganese-based positive electrode material prepared in comparative example 2 of the present invention;
fig. 4 is a rate performance test chart of the positive electrode material of the sodium-ion battery prepared in example 1 of the present invention.
Detailed Description
The invention is further described with reference to the following figures and examples:
the present disclosure will be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the disclosure may be shown and described, and which, when modified and varied by the techniques taught herein, can be made by those skilled in the art without departing from the spirit and scope of the disclosure.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the terms "comprising," "including," "having," and the like are open-ended terms that mean including, but not limited to.
As used herein, the term (terms), unless otherwise indicated, shall generally have the ordinary meaning as commonly understood by one of ordinary skill in the art, in this written description and in the claims. Certain words used to describe the disclosure are discussed below or elsewhere in this specification to provide additional guidance to those skilled in the art in describing the disclosure.
Example (b):
a preparation method of a lithium-rich manganese-based positive electrode material precursor with a core-shell structure comprises the following steps:
preparing Ni and Mn metal liquid with the molar concentration of 1.8-2.2 mol/L, wherein the molar ratio of Ni to Mn is 35;
preparing a sodium hydroxide or potassium hydroxide solution with the molar concentration of 10mol/L as a precipitator;
preparing an ammonia water solution with the molar concentration of 2.5mol/L as a complexing agent;
preparing a sodium dibutylnaphthalenesulfonate solution with the mass percentage of 2%;
step two, adding pure water, the precipitant and the complexing agent into a closed reaction kettle to prepare a base solution, controlling the pH value of the base solution to be 11.5-12.1 by the precipitant, controlling the ammonia concentration in the base solution to be 0.2mol/L by the complexing agent, and maintaining the temperature of the base solution at 80 ℃;
step three, keeping the stirring of the reaction kettle open, introducing nitrogen or inert gas with the flow of 0.5-0.8 m 3 Step one, continuously adding the metal liquid, the precipitator, the complexing agent and the additive solution in the step one into a reaction kettle at the flow rate of 50-400L/min respectively to perform coprecipitation reaction; the pH value is maintained at 11.5-12.1 in the reaction process, the reaction temperature is maintained at 80 ℃, the ammonia concentration is controlled at 0.2mol/L in the reaction process, the mass percentage content of the sodium dibutylnaphthalenesulfonate in the reaction kettle is 0.04%, the rotating speed of the reaction kettle is 650r/min, and the particle size D50 of the slurry in the reaction kettle is 1 Feeding liquid is suspended when the grain size grows to 80 percent of the target grain size D50;
reducing the temperature of a reaction kettle to 55-65 ℃, continuously adding the metal liquid, the precipitator and the complexing agent in the step one into the reaction kettle at the flow rate of 50-400L/min respectively to continue coprecipitation reaction, wherein the pH value is maintained at 11.5-12.1 in the reaction process, the ammonia concentration is controlled at 0.2mol/L in the reaction process, the reaction temperature is maintained at 55-65 ℃, the rotating speed of the reaction kettle is 500-600 r/min, and the liquid inlet is stopped when the granularity of slurry in the reaction kettle reaches a target granularity D50;
step four, performing filter pressing, washing and drying on the coprecipitation product in the step three to obtain a lithium-rich manganese-based positive electrode material precursor with a core-shell structure, wherein the porosity of a core layer is 56%, and the D50 of the core layer is 50% 1 80% of the precursor, the porosity of the shell layer is 8%, and the D50 of the shell layer 2 The precursor accounts for 20%, the ratio of the porosity of the core layer to the porosity of the shell layer meets 7 0.35 Mn 0.65 (OH) 2 D50 is 6.524um, and the tap density is 1.55g/cm 3 The specific surface area is 75.2m 2 The data are shown in Table 1.
Comparative example 1:
the difference from the example is that the mass percentage of the sodium dibutylnaphthalenesulfonate in the reaction kettle in the third step is different, the sodium dibutylnaphthalenesulfonate is not added in the comparative example 1, and the rest is the same as the example. The obtained precursor was washed and dried, and the relevant data are shown in table 1.
Comparative example 2:
the difference from the example is that the temperature of the reaction in the third step is different, the temperature of the reaction in the comparative example 2 is maintained at 55-65 ℃, and the rest is the same as the example. The precursor obtained was washed and dried, and the relevant data are shown in table 1.
Comparative example 3:
the difference from the example is that D50 in step three 1 In contrast, comparative example 3, D50 1 The particle size is 40% of the target particle size D50, and the rest is the same as the examples. The precursor obtained was washed and dried, and the relevant data are shown in table 1.
Comparative example 4:
the difference from the example is that D50 in step three 1 In contrast, comparative example 4, D50 1 The particle size is 90% of the target particle size D50, and the rest is the same as the example. The precursor obtained was washed and dried, and the relevant data are shown in table 1.
Table 1 shows the comparison of the data of the finished products obtained in the examples and the comparative examples
From the data in table 1, it can be seen that: in comparative example 1, the porosity of the core layer of the precursor of the lithium-rich manganese-based positive electrode material prepared without adding the additive is obviously lower than that of the core layer of the precursor of the lithium-rich manganese-based positive electrode material prepared with adding the additive, which shows that the additive has the effect of increasing the porosity. In comparative example 2, it is illustrated that when the reaction temperature is lowered, the growth rate becomes slow, resulting in coarsening of primary particles of the core layer and a decrease in porosity. With decreasing porosity of the core layer or D50 of the core layer 1 The proportion of the precursor to the total particle size D50 is reduced, the tap density of the precursor of the prepared lithium-rich manganese-based positive electrode material is gradually improved, and the corresponding ratioThe surface area gradually increases.
Table 2 shows the results of testing the electrical properties of the lithium-rich manganese-based cathode materials corresponding to the lithium-rich manganese-based cathode material precursors prepared in the examples and the respective proportions
From the data in table 2, it can be seen that: the first discharge capacity of the lithium-rich manganese-based positive electrode material corresponding to the precursor of the lithium-rich manganese-based positive electrode material prepared in the embodiment can reach 265.8mAh/g, and the capacity retention rate after 50 times of circulation is 81 percent, which is higher than that of all comparative examples.
Fig. 1, 2 and 3 are electron micrographs of precursors of lithium-rich manganese-based positive electrode materials prepared in examples, comparative examples 1 and 2, respectively.
As can be seen from fig. 1, the core layer part (inside the coil) of the lithium-rich manganese-based positive electrode material precursor has a loose and porous structure, and primary particles are fine and uniform, and the shell layer part is relatively dense, so that the structure is favorable for improving the transmission efficiency of lithium ions and the stability of the structure. The porosity of the inner core layer of the lithium-rich manganese-based positive electrode material precursors prepared in comparative example 1 (fig. 2) and comparative example 2 (fig. 3) was significantly smaller than that of the comparative example.
Fig. 4 shows the rate performance test result of the positive electrode material of the sodium-ion battery prepared in example 1, and it can be known from the figure that the discharge capacity can reach 94mAh/g under the condition that the charge-discharge current density is 5C, and the excellent rate performance is shown.
The above embodiments are merely illustrative of the technical ideas and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered in the protection scope of the present invention.
Claims (10)
1. A lithium-rich manganese-based positive electrode material precursor with a core-shell structure is characterized in that: has a chemical formula of Ni x Mn y (OH) 2 Wherein x is more than or equal to 0.30 and less than 0.40, and y is more than or equal to 0.60 and less than 0.70.
2. A precursor according to claim 1, wherein: comprises a core layer and a shell layer, wherein the porosity of the core layer is 40 to 60 percent, and the D50 of the core layer 1 Accounting for 60 to 80 percent of the precursor; the porosity of the shell is 5 to 8 percent, and the D50 of the shell is 2 The composite material accounts for 20 to 40% of the precursor, and the ratio of the porosity of the core layer to the porosity of the shell layer satisfies 5.
3. A precursor according to claim 1, wherein: d50 is 4 to 7um, and the tap density is 1.20 to 1.60g/cm 3 The specific surface area is 70 to 90m 2 /g。
4. A preparation method of a lithium-rich manganese-based positive electrode material precursor with a core-shell structure is characterized by comprising the following steps: the method comprises the following steps:
step one, preparing Ni and Mn metal liquid with the molar concentration of 1.8 to 2.2mol/L;
preparing a sodium hydroxide or potassium hydroxide solution with the molar concentration of 8-10mol/L as a precipitator;
preparing an ammonia water solution with the molar concentration of 2 to 4mol/L as a complexing agent;
preparing an additive solution with the mass percentage of 1 to 3 percent;
adding pure water, the precipitant and the complexing agent into a closed reaction kettle to prepare a base solution, controlling the pH value of the base solution to be 11.5-12.1 by using the precipitant, controlling the ammonia concentration in the base solution to be 0.05-0.25mol/L by using the complexing agent, and maintaining the temperature of the base solution to be 75-85 ℃;
step three, keeping the stirring of the reaction kettle open, introducing nitrogen or inert gas, wherein the flow rate is 0.5 to 0.8m 3 Continuously adding the molten metal, the precipitator, the complexing agent and the additive solution in the step one into a reaction kettle at the flow rate of 50-400L/min respectively to perform coprecipitation reaction; the pH value is maintained at 11.5 to 12.1 in the reaction process, the reaction temperature is maintained at 75 to 85 ℃, the rotating speed of the reaction kettle is 600 to 700r/min, and when the granularity of slurry in the reaction kettle is D50 1 Grow to the eyeStopping feeding liquid when the standard granularity D50 is 60-80%;
reducing the temperature of a reaction kettle to 55-65 ℃, continuously adding the molten metal, the precipitator and the complexing agent in the step one into the reaction kettle at the flow rate of 50-400L/min respectively, continuously carrying out coprecipitation reaction, wherein the pH value is maintained at 11.5-12.1 in the reaction process, the reaction temperature is maintained at 55-65 ℃, the rotation speed of the reaction kettle is 500-600r/min, and stopping feeding liquid when the granularity of slurry in the reaction kettle reaches a target granularity D50;
and step four, centrifuging, washing and drying the coprecipitation product in the step three to obtain the lithium-rich manganese-based positive electrode material precursor with the core-shell structure.
5. The method of claim 4, wherein: in the first step, the additive is one or more of sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, sodium tetrapropylene benzene sulfonate and sodium dibutyl naphthalene sulfonate.
6. The method of claim 4, wherein: in the third step, the mass percentage of the additive in the reaction kettle is 0.02 to 0.06 percent.
7. The method of claim 4, wherein: in the third step, the ammonia concentration is kept at 0.05 to 0.25mol/L during the reaction.
8. The method of claim 4, wherein: in step three, the target granularity D50 is 4 to 7um.
9. The method of claim 4, wherein: in the fourth step, the chemical formula of the precursor is Ni x Mn y (OH) 2 Wherein x is more than or equal to 0.30 and less than 0.40, and y is more than or equal to 0.60 and less than 0.70.
10. The method of claim 9, wherein: the precursor comprises a core layer and a shell layer, soThe porosity of the core layer is 40 to 60 percent, and the D50 of the core layer 1 Accounting for 60 to 80 percent of the precursor; the porosity of the shell is 5 to 8 percent, and the D50 of the shell is 2 The composite material accounts for 20 to 40% of the precursor, the ratio of the porosity of the core layer to the porosity of the shell layer satisfies 5 to 1, and the ratio of the porosity of the shell layer satisfies 5 to 1 to 8;
the tap density of the precursor is 1.20 to 1.60g/cm 3 The specific surface area is 70 to 90m 2 /g。
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