CN115775875A - High-nickel positive electrode material, preparation method thereof and lithium ion battery - Google Patents
High-nickel positive electrode material, preparation method thereof and lithium ion battery Download PDFInfo
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Abstract
The invention relates to the technical field of lithium ion batteries, in particular to a high-nickel anode material, a preparation method thereof and a lithium ion battery. The preparation method of the high-nickel cathode material comprises the following steps: uniformly mixing nickel manganese hydroxide and a lithium source to obtain a mixture, wherein the lithium source is LiOH and LiNO 3 (ii) a Sintering the mixture to obtain a high-nickel anode material; the sintering process comprises a temperature rise stage, the temperature rise rate of the temperature rise stage and LiNO 3 The product of molar ratios in the lithium source is 20% or less. The preparation method can reduce the content of residual alkali in the sintered product and reduce the alkalinity of the high-nickel cathode material, so that the sintered product does not need to be washed, the process is simplified, the production cost is reduced, and the production cost is avoidedThe surface of the high-nickel anode material is damaged, thereby ensuring the capacity and the cycle performance of the high-nickel anode material and avoiding the phenomenon that LiNO is generated due to the LiNO 3 The safety hidden danger caused by overhigh content and/or too fast temperature rise improves the safety in the preparation process.
Description
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a high-nickel positive electrode material, a preparation method thereof and a lithium ion battery.
Background
The lithium ion battery has the advantages of high voltage platform, good cycle performance, no memory effect, high specific energy and the like, and is the most widely applied power battery at present. With the development of energy storage of a smart power grid and the continuous popularization of new energy automobiles, the lithium ion battery is rapidly developed, and meanwhile, the performance requirement of the market on the lithium ion battery is higher and higher. As the commonly used anode material at present, the lithium nickel manganese cobaltate has the advantages of high energy density, good cycle performance and the like; however, cobalt is expensive and causes great environmental pollution, which limits its application in lithium ion batteries. Therefore, the development of the cobalt-free lithium nickel manganese oxide material has very important significance.
Along with the increase of the nickel content in the cobalt-free nickel lithium manganate material, the capacity of the cobalt-free nickel lithium manganate material is gradually increased, and the residual alkali content of the cobalt-free nickel lithium manganate material is higher and higher. The high residual alkali content can cause water absorption during slurry preparation, which results in poor processing performance of the positive pole piece. For this reason, after the nickel manganese hydroxide is sintered with lithium hydroxide to obtain a nickel lithium manganate material with a high nickel content, it is usually necessary to wash it with water and perform secondary sintering to reduce the surface residual alkali content. However, li in the crystal lattice of the material surface is easily caused in the water washing process + The NiO without electrochemical activity is generated by dissolution, the surface phase structure of the material is damaged, and the capacity and the cycle performance of the material are influenced.
Disclosure of Invention
Therefore, the technical problem to be solved by the invention is how to reduce the residual alkali content of the nickel lithium manganate material with high nickel content and improve the capacity and cycle performance of the nickel lithium manganate material with high nickel content, so as to provide a high-nickel positive electrode material, a preparation method thereof and a lithium ion battery.
The invention provides a high-nickel anode materialThe preparation method of the material comprises the following steps: uniformly mixing nickel manganese hydroxide and a lithium source to obtain a mixture, wherein the lithium source is LiOH and LiNO 3 (ii) a Sintering the mixture to obtain the high-nickel cathode material; the sintering process comprises a temperature rise stage, wherein the temperature rise rate of the temperature rise stage and LiNO 3 The product of molar ratio in the lithium source is less than or equal to 20%, and the unit of the temperature rise rate is ℃/min.
Optionally, the heating rate is 1 ℃/min-3 ℃/min, liNO 3 The molar ratio of the lithium source is 5-20%.
Optionally, the ratio of the molar amount of lithium element in the lithium source to the total molar amount of nickel element and manganese element in the nickel manganese hydroxide is 1.01-1.12.
Optionally, the nickel manganese hydroxide is Ni x Mn 1-x (OH) 2 ，0.85≤x≤0.95。
Optionally, the particle size distribution D50 of the lithium source is less than or equal to 10 μm; the particle size distribution D50 of the nickel-manganese hydroxide is 7-12 mu m, and the specific surface area of the nickel-manganese hydroxide is 8m 2 /g-20m 2 /g。
Optionally, during the sintering process, the mixture is placed in an oxygen atmosphere.
Optionally, in the sintering process, the mixture is placed in a reaction chamber, and oxygen is continuously introduced into the reaction chamber, wherein the flow rate of the oxygen is 5L/min to 10L/min.
Optionally, the temperature-raising stage includes a first temperature-raising stage and a second temperature-raising stage; the sintering process comprises a first temperature rise stage, a first heat preservation stage, a second temperature rise stage, a second heat preservation stage and a temperature reduction stage which are sequentially carried out, wherein the temperature of the first heat preservation stage is higher than that of the second heat preservation stage.
Optionally, the temperature of the first heat preservation stage is 500 ℃ to 600 ℃, and the heat preservation time of the first heat preservation stage is 4h to 7h; the temperature of the second heat preservation stage is 700-800 ℃, and the heat preservation time of the second heat preservation stage is 8-12 h.
Optionally, the preparation method of the high-nickel cathode material further includes: after the mixture is sintered, the prepared high nickel cathode material is sequentially crushed and sieved.
Optionally, the mesh number of the screen used for sieving is 300-400 meshes; after the screening is carried out, the particle size of the high-nickel cathode material is 6-13 μm.
The invention also provides a high-nickel anode material which is prepared by the preparation method of the high-nickel anode material, the pH value of the high-nickel anode material is 11.5-11.8, and the content of residual alkali in the high-nickel anode material is less than or equal to 5000ppm.
The invention also provides a lithium ion battery which comprises the high-nickel cathode material.
The technical scheme of the invention has the following advantages:
1. in the preparation method of the high-nickel cathode material provided by the invention, the lithium source is LiOH and LiNO 3 ，LiNO 3 Has the characteristics of low melting temperature (264 ℃) and low decomposition temperature (600 ℃), thereby being suitable for preparing high-nickel anode materials. LiNO 3 Part of LiOH is replaced by LiNO as a neutral substance 3 The basicity of the lithium source can be reduced, and even if a small amount of unreacted lithium source is contained in the sintered product, the content of LiOH therein is limited, so that the basicity of the sintered product can be reduced; meanwhile, liNO 3 NO is generated during the sintering process 2 NO in the reaction environment after the sintered product is cooled to room temperature 2 Will react with the moisture in the air to generate nitric acid, thereby inhibiting CO in the air 2 、H 2 O and Li 2 And O, thereby reducing the alkalinity of the sintered product. In summary, some of the LiOH groups were replaced with LiNO 3 The content of residual alkali in the sintered product can be reduced, the alkalinity of the high-nickel anode material can be reduced, and the processability of the anode piece is ensured. Because the content of residual alkali in the sintered product is low, the sintered product does not need to be washed by water, the process is simplified, the production cost is reduced, the surface of the high-nickel anode material is prevented from being damaged, and the capacity and the cycle performance of the high-nickel anode material are ensured. Further, liNO 3 For explosive and dangerous chemicals, by limiting the heating rate in the heating stageRatio and LiNO 3 The product of molar ratio in the lithium source is less than or equal to 20%, avoiding the problem of LiNO 3 The safety hidden danger caused by overhigh content and/or too fast temperature rise improves the safety in the preparation process.
2. The lithium ion battery provided by the invention has the advantages that the content of residual alkali of the adopted high-nickel anode material is lower, and the surface structure is complete, so that the energy density and the cycle performance of the lithium ion battery are improved.
Detailed Description
The technical solutions of the present invention are described clearly and completely below, and it is obvious that the described embodiments are some, not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. The examples do not show the specific experimental steps or conditions, and can be performed according to the conventional experimental steps described in the literature in the field. The reagents or instruments used are conventional reagent products which are commercially available, and manufacturers are not indicated.
It is to be understood that the residual alkali mainly includes LiOH and Li 2 CO 3 . The reason for the generation of residual alkali is mainly because the lithium source will volatilize to some extent during the high-temperature sintering process, so the lithium source is usually in an excess amount to compensate for the loss during the sintering process, which results in a small amount of lithium salt (Li at high temperature) remaining in the sintered product 2 In the form of O), after the sintered product is cooled to room temperature, the lithium salt can absorb CO in the air 2 And H 2 O, thereby forming LiOH and Li 2 CO 3 Resulting in a sintered product having a certain basicity. Meanwhile, because the synthesis temperature of the nickel lithium manganate material with high nickel content is lower, the LiOH with lower melting temperature is usually selected as the lithium source for preparing the material, and the LiOH is a strong alkaline substance, so that when a sintering product contains a small amount of unreacted LiOH, the sintering product has strong alkalinity; because the content of residual alkali in the nickel lithium manganate material with high nickel content is more, the nickel lithium manganate material needs to be washed by water, and the surface of the material is damaged in the washing process, so that the nickel lithium manganate material with high nickel content is obtainedThe capacity and the cycle performance of the material are affected. The lithium nickel manganese oxide material with low nickel content has low residual alkali content in the material obtained by sintering, and cannot cause increased influence on the processing of the positive pole piece, so that the lithium nickel manganese oxide material does not need to be washed by water.
Therefore, this embodiment provides a method for preparing a high-nickel cathode material, including:
uniformly mixing nickel manganese hydroxide and a lithium source to obtain a mixture, wherein the lithium source is LiOH and LiNO 3 ；
Sintering the mixture to obtain the high-nickel cathode material; the sintering process comprises a temperature rise stage, wherein the temperature rise rate of the temperature rise stage and LiNO 3 The product of molar ratio in the lithium source is less than or equal to 20 percent, and the unit of the temperature rise rate is ℃/min;
and sequentially crushing and sieving the prepared high-nickel anode material, wherein the mesh number of a sieve used for sieving is 300-400 meshes, and removing partial impurities of the high-nickel anode material through sieving.
In the preparation method of the high-nickel cathode material, the lithium source is LiOH and LiNO 3 ，LiNO 3 Has the characteristics of low melting temperature (264 ℃) and low decomposition temperature (600 ℃), thereby being suitable for preparing high-nickel anode materials. LiNO 3 Part of LiOH is replaced by LiNO as a neutral substance 3 The basicity of the lithium source can be reduced, and even if a small amount of unreacted lithium source is contained in the sintered product, the content of LiOH therein is limited, so that the basicity of the sintered product can be reduced; meanwhile, liNO 3 NO is generated during the sintering process 2 NO in the reaction environment after the sintered product is cooled to room temperature 2 Can react with moisture in the air to generate nitric acid, thereby inhibiting CO in the air 2 、H 2 O and Li 2 And O, thereby reducing the alkalinity of the sintered product. In summary, some of the LiOH groups were replaced with LiNO 3 The content of residual alkali in the sintered product can be reduced, the alkalinity of the high-nickel anode material can be reduced, and the processability of the anode piece is ensured. Because the content of residual alkali in the sintered product is lower, the sintered product does not need to be washed by water, thereby simplifying the process, reducing the production cost,the surface of the high-nickel anode material is prevented from being damaged, and the capacity and the cycle performance of the high-nickel anode material are ensured. Further, liNO 3 Is an explosive and dangerous chemical, and the temperature rise rate and LiNO are limited in the temperature rise stage 3 The product of molar ratio in the lithium source is less than or equal to 20%, thereby avoiding LiNO 3 The potential safety hazard caused by overhigh content and/or over fast temperature rise improves the safety in the preparation process.
It is to be understood that when the lithium source is LiNO only 3 In the process, in order to ensure the safe operation of the reaction, the heating rate and the sintering temperature need to be strictly controlled, the heating rate is as low as possible, and the lower sintering temperature is also adopted, so that the reaction time is longer, and the crystal form of the high-nickel anode material is poor; in this application, liOH and LiNO are used 3 The mixed lithium source can improve the reaction rate, shorten the sintering time and be beneficial to improving the production efficiency on the basis of ensuring the safe reaction, and meanwhile, the mixed lithium source can also form a high-nickel anode material with a good crystal form, thereby being beneficial to improving the capacity and prolonging the cycle life.
Further, the heating rate is 1-3 ℃/min, liNO 3 The molar ratio of the lithium source is 5-20%; illustratively, the ramp rate can be 1 deg.C/min, 1.25 deg.C/min, 1.5 deg.C/min, 1.75 deg.C/min, 2 deg.C/min, 2.25 deg.C/min, 2.5 deg.C/min, 2.75 deg.C/min, 3 deg.C/min, and any number therebetween; liNO 3 The molar ratio in the lithium source may be 5%, 7.5%, 10%, 12.5%, 15%, 17.5%, 20% and any value therebetween, the temperature increase rate in the temperature increase stage and the LiNO 3 The product of the molar ratio in the lithium source may be 1%, 2.5%, 5%, 7.5%, 10%, 12.5%, 15%, 17.5%, 20%, and any number therebetween, liNO 3 The higher the content of (b), the slower the temperature rise rate; the mesh size of the screen used for screening may be 300 mesh, 325 mesh, 350 mesh, 375 mesh, 400 mesh and any number between the above.
In this embodiment, the ratio of the molar amount of lithium element in the lithium source to the total molar amount of nickel element and manganese element in the nickel manganese hydroxide is 1.01 to 1.12, which affects the ratio of the molar amount of lithium element to the molar amount of nickel manganese element in the high nickel positive electrode material. Illustratively, the ratio of the molar amount of lithium element in the lithium source to the total molar amount of nickel element and manganese element in the nickel manganese hydroxide is 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.1, 1.11, 1.12 and any number therebetween.
Further, the nickel manganese hydroxide is Ni x Mn 1-x (OH) 2 X is more than or equal to 0.85 and less than or equal to 0.95, the ratio of the molar weight of the nickel element to the molar weight of the manganese element in the high-nickel positive electrode material is directly influenced, the nickel lithium manganate material with high nickel content is prepared by limiting x to be the value, manganese mainly plays a role in stabilizing a material skeleton in the nickel lithium manganate material, and the content of nickel is closely related to the specific capacity of the nickel lithium manganate material, so that the energy density of a lithium ion battery is influenced. Illustratively, x may be 0.85, 0.86, 0.87, 0.88, 0.89, 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, and any number therebetween.
Further, the particle size distribution D50 of the lithium source is less than or equal to 10 μm, the particle size distribution D50 of the nickel-manganese hydroxide is 7 μm-12 μm, and the specific surface area of the nickel-manganese hydroxide is 8m 2 /g-20m 2 And/g, the above parameters of the lithium source and the nickel manganese hydroxide are limited, so that the lithium source and the nickel manganese hydroxide are favorably fully reacted, the reaction efficiency is favorably improved, and the residual lithium source amount, namely the residual alkali content, in the generated high-nickel cathode material is favorably reduced. Illustratively, the particle size distribution D50 of the lithium source may be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm and any value therebetween, the particle size distribution D50 of the nickel manganese hydroxide may be 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm and any value therebetween, and the specific surface area of the nickel manganese hydroxide may be 8m 2 /g、10m 2 /g、12m 2 /g、14m 2 /g、16m 2 /g、18m 2 /g、20m 2 G and any value therebetween.
Further, in the sintering process, the mixture is placed in an oxygen atmosphere, that is, the mixture is placed in a reaction chamber, and oxygen is continuously introduced into the reaction chamber, so that the forward progress of the reaction can be promoted, the reaction efficiency can be improved, and the reduction of the amount of residual lithium source in the generated high-nickel anode material, namely the residual alkali content, can be facilitated. Specifically, the flow rate of the oxygen is 5L/min-10L/min; illustratively, the flow rate of oxygen may be 5L/min, 6L/min, 7L/min, 8L/min, 9L/min, 10L/min, and any value therebetween.
Further, the temperature rise stage comprises a first temperature rise stage and a second temperature rise stage; the sintering process comprises a first temperature rise stage, a first heat preservation stage, a second temperature rise stage, a second heat preservation stage and a temperature reduction stage which are sequentially carried out, wherein the temperature of the first heat preservation stage is higher than that of the second heat preservation stage. Specifically, the temperature of the first heat preservation stage is 500-600 ℃, the heat preservation time of the first heat preservation stage is 4-7 h, the temperature of the second heat preservation stage is 700-800 ℃, and the heat preservation time of the second heat preservation stage is 8-12 h. For example, the temperature of the first incubation period may be 500 ℃, 525 ℃, 550 ℃, 575 ℃, 600 ℃ and any value therebetween, the incubation time of the first incubation period may be 4h, 4.5h, 5h, 5.5h, 6h, 6.5h, 7h and any value therebetween, the temperature of the second incubation period may be 700 ℃, 725 ℃, 750 ℃, 775 ℃, 800 ℃ and any value therebetween, and the incubation time of the second incubation period may be 8h, 9h, 10h, 11h, 12h and any value therebetween.
In this embodiment, after weighing the nickel manganese hydroxide and the lithium source, placing the nickel manganese hydroxide and the lithium source in a mixer for mixing, wherein the rotation speed of the mixer is 700rpm to 1000rpm, and the mixing time is 10min to 20min; illustratively, the rotational speed of the mixer may be 700rpm, 750rpm, 800rpm, 850rpm, 900rpm, 950rpm or 1000rpm, and the mixing time may be 10min, 12min, 14min, 16min, 18min or 20min.
Prepared in this exampleThe high nickel anode material is Li y Ni x Mn 1-x O 2 Y is more than or equal to 1.01 and less than or equal to 1.12, x is more than or equal to 0.85 and less than or equal to 0.95, the pH value is 11.5 to 11.8, the content of residual alkali is less than or equal to 5000ppm, and the specific surface area is 0.3m 2 /g-1.5m 2 (ii)/g; after sieving, the particle size of the high nickel anode material is 6-13 μm.
The embodiment also provides a lithium ion battery which comprises the high-nickel cathode material. Because the content of residual alkali of the high-nickel anode material is lower and the surface structure is complete, the energy density and the cycle performance of the lithium ion battery are improved.
The following is an illustrative and complete description of the preparation method of the high nickel cathode material provided by the present invention, and it is obvious that the described embodiments are a part of the embodiments of the present invention, but not all of them.
Example 1
The embodiment provides a preparation method of a high-nickel cathode material, which comprises the following steps:
weighing nickel manganese hydroxide, liOH and LiNO 3 ，LiNO 3 The molar ratio of the lithium source to the nickel manganese hydroxide is 10%, and the ratio of the molar amount of the lithium element in the lithium source to the total molar amount of the nickel element and the manganese element in the nickel manganese hydroxide is 1.05, wherein the nickel manganese hydroxide is Ni 0.92 Mn 0.08 (OH) 2 The particle diameter is 10-12 μm, the specific surface area is 8m 2 /g-20m 2 G, liOH and LiNO 3 The particle diameters of the particles are less than or equal to 10 mu m;
mixing nickel manganese hydroxide, liOH and LiNO 3 Placing the mixture in a mixer, and uniformly mixing to obtain a mixture, wherein the rotating speed of the mixer is 850rpm, and the mixing time is 15min;
placing the mixture in a sintering furnace, continuously introducing oxygen into the sintering furnace with the flow of 5L/min, heating the sintering furnace to 600 ℃ at the heating rate of 1 ℃/min, preserving heat for 5h, heating to 720 ℃ at the heating rate of 1 ℃/min, and preserving heat for 10h; then naturally cooling;
after the temperature in the sintering furnace is reduced to room temperature, taking out and crushing the sintered product, and sieving the crushed sintered product with a 400-mesh sieve to obtain the high-nickel anode materialIs Li 1.05 Ni 0.92 Mn 0.08 O 2 。
Example 2
The embodiment provides a preparation method of a high-nickel cathode material, which comprises the following steps:
weighing nickel manganese hydroxide, liOH and LiNO 3 ，LiNO 3 The molar ratio of the lithium source to the nickel manganese hydroxide is 5%, and the ratio of the molar amount of the lithium element in the lithium source to the total molar amount of the nickel element and the manganese element in the nickel manganese hydroxide is 1.03, wherein the nickel manganese hydroxide is Ni 0.9 Mn 0.1 (OH) 2 The particle diameter is 10-12 μm, the specific surface area is 8m 2 /g-20m 2 G, liOH and LiNO 3 The particle diameters of the particles are less than or equal to 10 mu m;
mixing nickel manganese hydroxide, liOH and LiNO 3 Placing the mixture into a mixer to be uniformly mixed to obtain a mixture, wherein the rotating speed of the mixer is 700rpm, and the mixing time is 20min;
placing the mixture in a sintering furnace, continuously introducing oxygen into the sintering furnace, wherein the flow of the oxygen is 7.5L/min, heating the sintering furnace to 600 ℃ at the heating rate of 2 ℃/min, preserving heat for 4h, heating to 750 ℃ at the heating rate of 2 ℃/min, and preserving heat for 8h; then naturally cooling;
after the temperature in the sintering furnace is reduced to room temperature, taking out and crushing the sintered product, and sieving the crushed sintered product with a 400-mesh sieve to obtain the high-nickel anode material, wherein the high-nickel anode material is Li 1.03 Ni 0.9 Mn 0.1 O 2 。
Example 3
The embodiment provides a preparation method of a high-nickel cathode material, which comprises the following steps:
weighing nickel manganese hydroxide, liOH and LiNO 3 ，LiNO 3 The molar ratio of the lithium source to the nickel manganese hydroxide is 20%, and the ratio of the molar amount of the lithium element in the lithium source to the total molar amount of the nickel element and the manganese element in the nickel manganese hydroxide is 1.08, wherein the nickel manganese hydroxide is Ni 0.85 Mn 0.15 (OH) 2 The particle diameter is 10-12 μm, the specific surface area is 8m 2 /g-20m 2 G, liOH and LiNO 3 The particle diameters of the particles are less than or equal to 10 mu m;
mixing nickel manganese hydroxide, liOH and LiNO 3 Placing the mixture in a mixer, and uniformly mixing to obtain a mixture, wherein the rotating speed of the mixer is 1000rpm, and the mixing time is 10min;
placing the mixture in a sintering furnace, continuously introducing oxygen into the sintering furnace with the flow of the oxygen being 10L/min, heating the sintering furnace to 500 ℃ at the heating rate of 3 ℃/min, preserving heat for 7h, heating to 780 ℃ at the heating rate of 3 ℃/min, and preserving heat for 12h; then naturally cooling;
after the temperature in the sintering furnace is reduced to room temperature, taking out and crushing the sintered product, and sieving the crushed sintered product through a 400-mesh sieve to obtain the high-nickel anode material, wherein the high-nickel anode material is Li 1.08 Ni 0.85 Mn 0.15 O 2 。
Comparative example 1
This comparative example provides a method for preparing a high nickel cathode material, which is different from the method for preparing a high nickel cathode material provided in example 1 in that: the lithium source is only LiOH.
Comparative example 2
This comparative example provides a method for preparing a high nickel cathode material, which is different from the method for preparing a high nickel cathode material provided in example 2 in that: the lithium source is only LiOH.
Comparative example 3
This comparative example provides a method for producing a high nickel positive electrode material, which is different from the method for producing a high nickel positive electrode material provided in example 3 in that: the lithium source is only LiOH.
Test example 1
The residual alkali content and PH of the high nickel positive electrode materials prepared in examples 1 to 3 and comparative examples 1 to 3 were measured, and the results are shown in table 1.
TABLE 1
| Li 2 CO 3 Amount (ppm) | Amount of LiOH (ppm) | Total amount of residual alkali (ppm) | pH | |
| Example 1 | 1200 | 3200 | 4400 | 10.84 |
| Example 2 | 1000 | 3300 | 4300 | 10.82 |
| Example 3 | 1400 | 3500 | 4900 | 11.23 |
| Comparative example 1 | 5800 | 6400 | 12200 | 11.89 |
| Comparative example 2 | 5200 | 6200 | 11400 | 11.74 |
| Comparative example 3 | 5700 | 6100 | 11800 | 11.73 |
Test example 2
Mixing the high-nickel cathode materials prepared in the examples 1-3 and the comparative examples 1-3 with conductive carbon black and polyvinylidene fluoride (PVDF) glue solution in a mass ratio of 92:4:4, mixing and homogenizing to obtain anode slurry, wherein the solid content of the polyvinylidene fluoride glue solution is 6.25%, and the solvent of the polyvinylidene fluoride glue solution is N-methylpyrrolidone (NMP); coating the positive electrode slurry on the surface of an aluminum foil, and then sequentially drying and rolling to obtain a positive electrode plate; and assembling the lithium plate serving as a negative electrode and the electrolyte serving as a carbonate electrolyte to obtain the R2032 button cell.
Carrying out charge and discharge tests on the assembled lithium ion battery at 25 ℃ and 0.1 ℃ to obtain the gram discharge capacity of the lithium ion battery; the cycle performance test was performed at 1C to obtain capacity retention after 50 cycles, and the test results are shown in table 1.
TABLE 2
| Capacity (mAh/g) | Capacity retention (%) | |
| Example 1 | 220.5 | 96 |
| Example 2 | 217.2 | 96.3 |
| Example 3 | 210.5 | 97.2 |
| Comparative example 1 | 214.3 | 94 |
| Comparative example 2 | 210.3 | 93.2 |
| Comparative example 3 | 204.5 | 92.7 |
As is clear from tables 1 and 2, part of LiOH was replaced with LiNO 3 The residual alkali content in the high-nickel anode material can be effectively reduced, and the pH value of the high-nickel anode material is reduced, so that the discharge capacity and the cycle performance of the lithium ion battery can be improved.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications derived therefrom are intended to be within the scope of the invention.
Claims (10)
1. A preparation method of a high-nickel cathode material is characterized by comprising the following steps:
uniformly mixing nickel manganese hydroxide and a lithium source to obtain a mixture, wherein the lithium source is LiOH and LiNO 3 ；
Sintering the mixture to obtain the high-nickel cathode material; the sintering process comprises a temperature rise stage, wherein the temperature rise rate of the temperature rise stage and LiNO 3 The product of molar ratio in the lithium source is less than or equal to 20%, and the unit of the temperature rising rate is ℃/min.
2. The method for producing a high-nickel positive electrode material according to claim 1, wherein the temperature increase rate is 1 ℃/min to 3 ℃/min, or LiNO 3 The molar ratio of the lithium source is 5-20%.
3. The method for producing a high nickel positive electrode material according to claim 1, wherein a ratio of a molar amount of lithium element in the lithium source to a total molar amount of nickel element and manganese element in the nickel manganese hydroxide is 1.01 to 1.12.
4. The method for producing a high nickel positive electrode material according to any one of claims 1 to 3, wherein the nickel manganese hydroxide is Ni x Mn 1-x (OH) 2 ，0.85≤x≤0.95。
5. The method for producing a high nickel positive electrode material according to any one of claims 1 to 3, characterized in that the particle size distribution D50 of the lithium source is 10 μm or less; the particle size distribution D50 of the nickel-manganese hydroxide is 7-12 mu m, and the specific surface area of the nickel-manganese hydroxide is 8m 2 /g-20m 2 /g。
6. The method for producing a high-nickel cathode material according to any one of claims 1 to 5, wherein the mixture is placed in an oxygen atmosphere during the sintering;
preferably, in the sintering process, the mixture is placed in a reaction chamber, oxygen is continuously introduced into the reaction chamber, and the flow rate of the oxygen is 5L/min-10L/min.
7. The method for producing a high-nickel cathode material according to claim 1 or 6, wherein the temperature rise phase includes a first temperature rise phase and a second temperature rise phase; the sintering process comprises the first temperature rise stage, the first heat preservation stage, the second temperature rise stage, the second heat preservation stage and the temperature reduction stage which are sequentially carried out, wherein the temperature of the first heat preservation stage is higher than that of the second heat preservation stage;
preferably, the temperature of the first heat preservation stage is 500-600 ℃, and the heat preservation time of the first heat preservation stage is 4-7 h; the temperature of the second heat preservation stage is 700-800 ℃, and the heat preservation time of the second heat preservation stage is 8-12 h.
8. The method for producing a high-nickel cathode material according to any one of claims 1 to 7, further comprising: after sintering the mixture, sequentially crushing and sieving the prepared high-nickel cathode material;
preferably, the mesh number of the screen used for sieving is 300-400 meshes; after the screening, the particle size of the high-nickel cathode material is 6-13 μm.
9. The high-nickel positive electrode material is characterized by being prepared by the preparation method of the high-nickel positive electrode material according to any one of claims 1 to 8, wherein the pH value of the high-nickel positive electrode material is 11.5-11.8, and the content of residual alkali in the high-nickel positive electrode material is less than or equal to 5000ppm.
10. A lithium ion battery comprising the high nickel positive electrode material according to claim 9.
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