CN115863585A - Modification method of high-nickel oxide, positive electrode material and lithium ion battery - Google Patents
Modification method of high-nickel oxide, positive electrode material and lithium ion battery Download PDFInfo
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Abstract
The invention belongs to the technical field of anode materials for batteries, and particularly relates to a method for modifying high-nickel oxide, and an anode material and a lithium ion battery prepared by the method. Mixing organic acid and volatile organic solvent to prepare organic acid solution, mixing the high nickel oxide with the organic acid solution, and reacting under stirring; the organic acid is at least one of capric acid, oxalic acid and tartaric acid. The invention can neutralize residual alkali on the surface of the nickelic oxide at a lower temperature by utilizing the specific organic acid, so that the invention can solve the problem of residual alkali on the surface of the nickelic oxide on the premise of not influencing the performance of the nickelic oxide. The positive electrode material comprises the high nickel oxide and a modification layer coating at least one part of the surface of the high nickel oxide, and the high nickel oxide modified by the lithium salt of the organic acid shows better structural stability and mechanical integrity and shows good capacity retention rate in a long-term cycle test.
Description
Technical Field
The invention belongs to the technical field of anode materials for batteries, and particularly relates to a method for modifying high-nickel oxide, and an anode material and a lithium ion battery prepared by the method.
Background
Lithium ion batteries are widely used as energy sources for rechargeable power supplies, portable electronic products and electric vehicles due to their relatively high energy density. In the quest for further improvements in the energy density of lithium batteries, nickel-rich layered oxides such as LiNi x Co y Mn z O 2 (x.gtoreq.0.6) is considered to be one of the most promising positive electrode materials for lithium ion batteries. However, the higher the Ni content in the nickel-rich cathode material, the more serious the problems in the aspects of surface slurrying, structure deterioration, interface parasitic side reaction, mechanical cracking, and the like. Wherein, the structural degradation of the material starts from the surface and extends to the matrix, which inevitably leads to slow diffusion of lithium ions, thereby deteriorating electrochemical performance, resulting in rapid capacity and potential decay; in addition, another important problem of the nickel-rich cathode material is surface residual lithium compounds such as LiOH and Li 2 CO 3 Inevitably formed on the surface of the material during the synthesis process.
Surface modification is one of the most effective means to improve the cycling stability of nickel-rich cathode materials in order to reduce the negative effects of residual alkali. Chinese patent document CN114937771A discloses a method for mixing and coating a high-nickel positive electrode material by using a supramolecular polymer formed by a nitrogenous organic matter and an acidic organic matter, and placing the polymer-coated high-nickel positive electrode material in an oxygen-containing atmosphere for heat treatment, thereby obtaining a high-nickel positive electrode materialForming a first organic salt coating layer and a second graphite-phase carbon nitride coating layer on the surface of the electrode material; the combined action of the double coating layers can improve the structural stability of the nickel anode material, promote the improvement of the cycle performance, reduce the residual alkali on the surface of the material, overcome the problems of high impedance and irreversible capacity decline caused by the residual alkali and obviously improve the conductivity of the coating layer. However, in the above-mentioned technique, the polymer needs to be heat-treated at a relatively high temperature (400 to 600 ℃) for 2 to 8 hours in order to form graphite-phase carbon nitride, and although the heat treatment is performed in an aerobic environment, ni inevitably occurs in the high-nickel positive electrode material 4+ Reduced, which results in the formation of NiO-like rock salt impurity phases in the positive electrode material that increase charge transfer resistance, thereby reducing the electrochemical performance of the high nickel positive electrode.
Disclosure of Invention
In view of the above, the technical problem to be solved by the present invention is that the existing method for reducing the residual alkali on the surface of the high nickel anode material can cause Ni 4+ Is reduced to influence the electrochemical performance of the high nickel anode, thereby providing a method which can effectively reduce the residual alkali on the surface of the high nickel anode material and simultaneously can not influence the electrochemical performance of the high nickel anode material.
The purpose of the invention is realized by the following technical scheme:
according to an embodiment of the present invention, in a first aspect, the present invention provides a method for modifying nickel oxide, including the steps of:
mixing organic acid with volatile organic solvent to prepare organic acid solution; the organic acid is at least one of capric acid, oxalic acid and tartaric acid;
mixing the nickelic oxide with the organic acid solution, reacting under stirring, removing the volatile organic solvent, and drying.
In the embodiment of the invention, the molar concentration of the organic acid in the organic acid solution is 2-4 mol/L.
In an embodiment of the present invention, the molar ratio of the nickelous oxide to the organic acid is 1:0.01 to 0.04 percent.
In an embodiment of the invention, said height isThe chemical structural general formula of the nickel oxide is Li 1.06 Ni a Co b Mn c O 2 Wherein a is more than or equal to 0.95 and less than or equal to 0.99,0.005 and less than or equal to b is more than or equal to 0.03,0.005 and less than or equal to c is less than or equal to 0.15, and a + b + c =1.
In the embodiment of the invention, the reaction temperature is 60-80 ℃, and the reaction time is 15-30 h.
In the embodiment of the present invention, the volatile organic solvent is at least one of acetone, butanone, cyclohexanone, dioxane, trichloroethylene and dichloromethane.
In the embodiment of the invention, the drying temperature is 100-150 ℃, and the drying time is 5-10 h.
According to an embodiment of the invention, in a second aspect, the invention provides a cathode material prepared by the method, and the specific surface area of the cathode material is 0.62-0.65 m 2 /g。
In an embodiment of the present invention, the positive electrode material includes a high nickel oxide and a modification layer coating at least a part of a surface of the high nickel oxide, and the modification layer is a lithium salt of an organic acid.
In an embodiment of the present invention, the median particle diameter of the positive electrode material is 9.0 to 11.0 μm.
According to an embodiment of the present invention, in a third aspect, the present invention also provides a lithium ion battery, including the above-mentioned cathode material.
Compared with the prior art, the technical scheme of the invention has the following advantages:
1. the invention provides a method for modifying high nickel oxide, which comprises the steps of mixing organic acid and volatile organic solvent to prepare organic acid solution, mixing the high nickel oxide with the organic acid solution, and reacting under stirring; wherein the organic acid is at least one of capric acid, oxalic acid, tartaric acid, etc. After a great deal of tests, the invention surprisingly discovers that the residual alkali on the surface of the high nickel oxide can be neutralized by using the specific organic acid, and the problems of high impedance and irreversible capacity decline of the material caused by the existence of the residual alkali are solved; because the neutralization reaction of the invention can be carried out at a lower temperature (not more than 80 ℃), the modification method of the invention can avoidNi in high nickel oxide 4+ And the reduction is carried out, and meanwhile, the organic solvent is adopted, so that the problems of increased side reactions on the surface of the high nickel oxide, surface structure recombination and the like caused by the existence of water can be avoided. Namely, the modification method can solve the problem of residual alkali on the surface of the high-nickel anode material on the premise of not influencing the performance of the high-nickel anode material.
2. The positive electrode material provided by the invention comprises a high nickel oxide and a modified layer coating at least one part of the surface of the high nickel oxide, wherein the modified layer is a lithium salt of organic acid. The lithium salt of the specific organic acid is selected as a modification layer for coating the high-nickel oxide, and the modification layer can stably exist in the battery circulation process, inhibits the direct contact of the electrolyte and the positive electrode material, improves the electrochemical stability and the ionic conductivity of the positive electrode material, enables the modified high-nickel oxide to show better structural stability and mechanical integrity, and shows good capacity retention rate in a long-term circulation test.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is an SEM image of the cathode material prepared in example 1.
Fig. 2 is a partially enlarged view of fig. 1.
Fig. 3 is an SEM image of the cathode material prepared in comparative example 1.
Fig. 4 is a partially enlarged view of fig. 3.
Fig. 5 is an SEM image of the cathode material prepared in comparative example 2.
Fig. 6 is a partially enlarged view of fig. 5.
Detailed Description
The following examples are provided to further understand the present invention, not to limit the scope of the present invention, but to provide the best mode, not to limit the content and the protection scope of the present invention, and any product similar or similar to the present invention, which is obtained by combining the present invention with other prior art features, falls within the protection scope of the present invention.
The examples do not indicate specific experimental procedures or conditions, and can be performed according to the procedures or conditions of the conventional experimental procedures described in the literature in the field. The reagents or instruments used are not indicated by manufacturers, and are all conventional reagent products which can be obtained commercially.
According to an embodiment of the present invention, in a first aspect, the present invention provides a method for modifying a nickel oxide, including the steps of:
mixing organic acid and volatile organic solvent to prepare organic acid solution, wherein the organic acid is at least one of capric acid, oxalic acid and tartaric acid;
mixing the high nickel oxide with the organic acid solution, reacting under stirring, removing the volatile organic solvent after the reaction is finished, and drying.
In the embodiment of the invention, the molar concentration of the organic acid in the organic acid solution is 2-4 mol/L, and the organic acid in the organic acid solution is favorably ionized sufficiently at the concentration, so that enough hydrogen ions are generated for the neutralization reaction. If the concentration of the organic acid is too low and the amount of generated hydrogen ions is too small, a large amount of organic acid solution needs to be consumed, so that resource waste is caused; if the concentration of the organic acid is too high, the amount of generated hydrogen ions is too large, and the nickel oxide is corroded, so that the electrochemical performance of the material is influenced.
In an embodiment of the present invention, the molar ratio of the nickelous oxide to the organic acid is 1: 0.01-0.04, and the organic acid can neutralize and remove most residual alkali on the surface of the high nickel oxide under the proportion, so that the existence of the residual alkali can not generate adverse effect on the performance of the battery, and meanwhile, the specific surface area of the anode material can be regulated within a proper range, thereby being beneficial to improving the electrical property of the material.
In the embodiment of the invention, the chemical structural general formula of the nickelic oxide is Li 1.06 Ni a Co b Mn c O 2 Wherein a is more than or equal to 0.95 and less than or equal to 0.99,0.005 and less than or equal to b is more than or equal to 0.03,0.005 and less than or equal to c is less than or equal to 0.15, and a + b + c =1. The higher the nickel content in the nickel oxide is, the larger the residual alkali amount on the surface of the nickel oxide is, and the modification method can solve the problem of residual alkali on the surface of the nickel oxide on the premise of not influencing the material performance.
In the embodiment of the invention, the organic acid solution can be mixed with residual alkali on the surface of the nickelic oxide such as LiOH and Li at normal temperature 2 O、Li 2 CO 3 The neutralization reaction is carried out, the reaction temperature is properly increased to 60-80 ℃, the reaction rate can be accelerated, and the reaction time can be shortened.
In the case of capric acid, the reaction is as follows:
2CH 3 (CH 2 ) 8 COOH+Li 2 O＝2CH 3 (CH 2 ) 8 COOLi+H 2 O
CH 3 (CH 2 ) 8 COOH+LiOH＝CH 3 (CH 2 ) 8 COOLi+H 2 O
2CH 3 (CH 2 ) 8 COOH+Li 2 CO 3 ＝2CH 3 (CH 2 ) 8 COOLi+H 2 O+CO 2
in the embodiment of the present invention, the volatile organic solvent is at least one of acetone, butanone, cyclohexanone, dioxane, trichloroethylene and dichloromethane. The volatile organic solvent is used, so that the solvent removing step can be carried out at a lower temperature, the influence of high temperature on the high-nickel oxide is avoided, and meanwhile, the water solvent can be avoided, and the increase of side reactions on the surface of the high-nickel oxide and the surface structure recombination are prevented.
After a great deal of tests, the invention surprisingly discovers that the residual alkali on the surface of the high nickel oxide can be neutralized by using the specific organic acid, and the problems of high impedance and irreversible capacity decline of the material caused by the existence of the residual alkali are solved; because the neutralization reaction of the invention can be carried out at a lower temperature (not more than 80 ℃), the modification method of the invention can avoid Ni in the nickelic oxide 4+ Is reduced, and simultaneously the invention adopts organic solvent,the problems of increased side reactions on the surface of the high nickel oxide, surface structure recombination and the like caused by the existence of water can be avoided. That is, the modification method of the invention can solve the problem of residual alkali on the surface of the nickel oxide without influencing the performance of the nickel oxide.
According to an embodiment of the invention, in a second aspect, the invention provides a cathode material prepared by the method, and the specific surface area of the cathode material is 0.62-0.65 m 2 (ii) in terms of/g. The larger the specific surface area is, the larger the contact area between the anode material and the electrolyte is, the more side reactions are, and the poorer the electrical property is; however, if the specific surface area is too small, the contact area between the positive electrode material and the electrolyte is too small, which is disadvantageous to lithium ion transfer, and the electrical properties are also deteriorated. The specific surface area of the anode material prepared by the invention is in the range, so that the transfer of lithium ions can be ensured, the side reaction on the surface of the anode material can be reduced, and the electrical property of the material is facilitated.
In an embodiment of the invention, the cathode material comprises a high nickel oxide and a modification layer coating at least a part of the surface of the high nickel oxide, and the modification layer is a lithium salt of an organic acid. The lithium salt of the specific organic acid is selected as a modification layer for coating the high-nickel oxide, and the modification layer can stably exist in the battery circulation process, inhibits the direct contact of the electrolyte and the positive electrode material, improves the electrochemical stability and the ionic conductivity of the positive electrode material, enables the modified high-nickel oxide to show better structural stability and mechanical integrity, and shows good capacity retention rate in a long-term circulation test.
In an embodiment of the present invention, the median particle diameter of the positive electrode material is 9.0 to 11.0 μm. If the particle size is too small, the specific surface area of the material is large, the contact surface with the electrolyte is large, side reactions are increased, the structure of the positive electrode is damaged, and the cycle performance is poor; on the other hand, if the particle size is too large, the lithium ion transport path becomes long, resistance increases, and battery capacity decreases. Therefore, the present invention can balance the battery performance by selecting the particle size of the positive electrode material within the above range.
According to the embodiment of the invention, in a third aspect, the invention also provides a lithium ion battery, which has higher 0.1C specific discharge capacity, first efficiency and cycle retention rate due to the inclusion of the positive electrode material.
The following describes the modification method of the nickel oxide provided by the present invention, and the cathode material and the lithium ion battery prepared by the modification method in detail with reference to specific examples.
Example 1
The preparation method of the cathode material provided by the embodiment comprises the following steps:
(1) Precursor Ni of high-nickel polycrystalline cathode material 0.96 Co 0.02 Mn 0.02 (OH) 2 And LiOH in a molar ratio of 1:1.06, mixing uniformly at 690 deg.C 2 Sintering for 10h in the atmosphere with the purity of 99.99 percent to obtain the high-nickel polycrystalline anode material Li 1.06 Ni 0.96 Co 0.02 Mn 0.02 O 2 ；
(2) Mixing the high nickel polycrystalline anode material obtained in the step (1) with 2mol/L decanoic acid (chemical formula: CH) 3 (CH 2 ) 8 COOH) and mixing the high nickel polycrystalline anode material and decanoic acid according to the molar ratio of 1:0.03, stirring for 15 hours in a constant-temperature water bath at 80 ℃, drying for 8 hours in a vacuum drying oven at 150 ℃ after the solvent is completely evaporated to obtain the modified high-nickel polycrystalline anode material Li 1.06 Ni 0.96 Co 0.02 Mn 0.02 O 2 ﹒(CH 3 (CH 2 ) 8 COOLi) 0.03 。
Example 2
The preparation method of the cathode material provided by the embodiment includes the following steps:
the high nickel polycrystalline anode material obtained in the step (1) in the example 1 is mixed with 2mol/L decanoic acid (chemical formula: CH) 3 (CH 2 ) 8 COOH) and mixing the high nickel polycrystalline anode material and decanoic acid according to the molar ratio of 1:0.02, evenly mixing, stirring in water bath at the constant temperature of 80 ℃ for 15h, drying in a vacuum drying oven at the temperature of 150 ℃ for 8h after the solvent is completely evaporated to obtain the modified high-nickel polycrystalline anode material Li 1.06 Ni 0.96 Co 0.02 Mn 0.02 O 2 ﹒(CH 3 (CH 2 ) 8 COOLi) 0.02 。
Example 3
The preparation method of the cathode material provided by the embodiment comprises the following steps:
the high nickel polycrystalline anode material obtained in the step (1) in the example 1 is mixed with 2mol/L decanoic acid (chemical formula: CH) 3 (CH 2 ) 8 COOH) and mixing the high nickel polycrystalline anode material and decanoic acid according to the molar ratio of 1:0.04, stirring for 15h in a constant-temperature water bath at 80 ℃, drying for 8h in a vacuum drying oven at 150 ℃ after the solvent is completely evaporated to obtain the modified high-nickel polycrystalline anode material Li 1.06 Ni 0.96 Co 0.02 Mn 0.02 O 2 ﹒(CH 3 (CH 2 ) 8 COOLi) 0.04 。
Example 4
The preparation method of the cathode material provided by the embodiment comprises the following steps:
the high nickel polycrystalline anode material obtained in the step (1) in the example 1 is mixed with 3mol/L decanoic acid (chemical formula: CH) 3 (CH 2 ) 8 COOH) and mixing the high nickel polycrystalline anode material and decanoic acid according to the molar ratio of 1:0.03, stirring for 15 hours in a constant-temperature water bath at 80 ℃, drying for 8 hours in a vacuum drying oven at 150 ℃ after the solvent is completely evaporated to obtain the modified high-nickel polycrystalline anode material Li 1.06 Ni 0.96 Co 0.02 Mn 0.02 O 2 ﹒(CH 3 (CH 2 ) 8 COOLi) 0.03 。
Example 5
The preparation method of the cathode material provided by the embodiment comprises the following steps:
the high nickel polycrystalline anode material obtained in the step (1) in the example 1 is mixed with 4mol/L decanoic acid (chemical formula: CH) 3 (CH 2 ) 8 COOH) and mixing the high nickel polycrystalline anode material and decanoic acid according to the molar ratio of 1:0.03, stirring for 15 hours in a constant-temperature water bath at 80 ℃, drying for 8 hours in a vacuum drying oven at 150 ℃ after the solvent is completely evaporated to obtain the modified high-nickel polycrystalline anode material Li 1.06 Ni 0.96 Co 0.02 Mn 0.02 O 2 ﹒(CH 3 (CH 2 ) 8 COOLi) 0.03 。
Example 6
The preparation method of the cathode material provided by the embodiment comprises the following steps:
(1) Precursor Ni of high-nickel polycrystalline positive electrode material 0.95 Co 0.03 Mn 0.02 (OH) 2 And LiOH at a molar ratio of 1:1.06, mixing uniformly at 690 deg.C 2 Sintering for 10h in the atmosphere with the purity of 99.99 percent to obtain the high-nickel polycrystalline anode material Li 1.06 Ni 0.95 Co 0.03 Mn 0.02 O 2 ；
(2) Mixing the high nickel polycrystalline anode material obtained in the step (1) with 2mol/L decanoic acid (chemical formula: CH) 3 (CH 2 ) 8 COOH) and mixing the high nickel polycrystalline anode material and decanoic acid according to the molar ratio of 1:0.03, stirring for 15 hours in a constant-temperature water bath at 80 ℃, drying for 8 hours in a vacuum drying oven at 150 ℃ after the solvent is completely evaporated to obtain the modified high-nickel polycrystalline anode material Li 1.06 Ni 0.95 Co 0.03 Mn 0.02 O 2 ﹒(CH 3 (CH 2 ) 8 COOLi) 0.03 。
Example 7
The preparation method of the cathode material provided by the embodiment comprises the following steps:
(1) Precursor Ni of high-nickel polycrystalline positive electrode material 0.99 Co 0.05 Mn 0.005 (OH) 2 And LiOH in a molar ratio of 1:1.06, mixing uniformly at 690 deg.C 2 Sintering for 10h in the atmosphere with the purity of 99.99 percent to obtain the high-nickel polycrystalline anode material Li 1.06 Ni 0.99 Co 0.005 Mn 0.005 O 2 ；
(2) Mixing the high nickel polycrystalline anode material obtained in the step (1) with 2mol/L decanoic acid (chemical formula: CH) 3 (CH 2 ) 8 COOH) and mixing the high nickel polycrystalline anode material and decanoic acid according to the molar ratio of 1:0.03, stirring in a constant-temperature water bath at 80 ℃ for 15 hoursAfter the solvent is completely evaporated, the mixture is placed in a vacuum drying oven at 150 ℃ for drying for 8 hours to obtain the modified high-nickel polycrystalline anode material Li 1.06 Ni 0.99 Co 0.005 Mn 0.005 O 2 ﹒(CH 3 (CH 2 ) 8 COOLi) 0.03 。
Example 8
The preparation method of the cathode material provided by the embodiment comprises the following steps:
the high nickel polycrystalline cathode material obtained in the step (1) in the example 7 is mixed with 2.5mol/L tartaric acid (chemical formula: CH) 3 (COOH) 3 ) Mixing the high nickel polycrystalline anode material and tartaric acid according to the mol ratio of 1:0.01, stirring for 20 hours in a constant temperature water bath at 60 ℃, drying for 10 hours in a vacuum drying oven at 120 ℃ after the solvent is completely evaporated to obtain the modified high-nickel polycrystalline anode material Li 1.06 Ni 0.99 Co 0.005 Mn 0.005 O 2 ﹒(CH 3 (COOLi) 3 ) 0.01 。
Example 9
The preparation method of the cathode material provided by the embodiment comprises the following steps:
the high nickel polycrystalline positive electrode material obtained in the step (1) in example 7 was mixed with 3.5mol/L of a dichloromethane solution of oxalic acid (chemical formula: HOOCCOOH) in a molar ratio of the high nickel polycrystalline positive electrode material to oxalic acid of 1:0.01, stirring the mixture in a constant temperature water bath at 70 ℃ for 30 hours, putting the mixture in a vacuum drying oven at 100 ℃ after the solvent is completely evaporated, and drying the mixture for 5 hours to obtain the modified high-nickel polycrystalline anode material Li 1.06 Ni 0.99 Co 0.005 Mn 0.005 O 2 ﹒(LiOOCCOOLi) 0.01 。
Comparative example 1
The preparation method of the cathode material provided by the comparative example comprises the following steps:
precursor Ni of high-nickel polycrystalline positive electrode material 0.96 Co 0.02 Mn 0.02 (OH) 2 And LiOH at a molar ratio of 1:1.06, mixing uniformly at 690 deg.C and O 2 Sintering for 10h in the atmosphere with the purity of 99.99 percent to obtain the high-nickel polycrystalline anode material Li 1.06 Ni 0.96 Co 0.02 Mn 0.02 O 2 。
Comparative example 2
The preparation method of the cathode material provided by the comparative example comprises the following steps:
mixing the high-nickel polycrystalline positive electrode material obtained in the step (1) in the example 1 with an acetone solution with the same volume as that of the example 1, stirring the mixture in a constant-temperature water bath at 80 ℃ for 15 hours, and after the solvent is completely evaporated, drying the mixture in a vacuum drying oven at 150 ℃ for 8 hours to obtain a high-nickel polycrystalline positive electrode material Li 1.06 Ni 0.96 Co 0.02 Mn 0.02 O 2 。
Comparative example 3
The preparation method of the cathode material provided by the comparative example comprises the following steps:
the high nickel polycrystalline anode material obtained in the step (1) in the example 1 is mixed with 2mol/L decanoic acid (chemical formula: CH) 3 (CH 2 ) 8 COOH) and mixing the high-nickel polycrystalline positive electrode material and decanoic acid according to the molar ratio of 1:0.05, stirring for 15 hours in a constant-temperature water bath at 80 ℃, drying for 8 hours in a vacuum drying oven at 150 ℃ after the solvent is completely evaporated to obtain the modified high-nickel polycrystalline anode material Li 1.06 Ni 0.96 Co 0.02 Mn 0.02 O 2 ﹒(CH 3 (CH 2 ) 8 COOLi) 0.05 。
Comparative example 4
The preparation method of the cathode material provided by the comparative example comprises the following steps:
the high nickel polycrystalline cathode material obtained in the step (1) in the example 1 is mixed with 2mol/L acetic acid (chemical formula: CH) 3 COOH) in an acetone solution, and mixing the high-nickel polycrystalline positive electrode material and acetic acid according to a molar ratio of 1:0.03, stirring for 15 hours in a constant-temperature water bath at 80 ℃, drying for 8 hours in a vacuum drying oven at 150 ℃ after the solvent is completely evaporated to obtain the modified high-nickel polycrystalline anode material Li 1.06 Ni 0.96 Co 0.02 Mn 0.02 O 2 ﹒(CH 3 COOLi) 0.03 。
Comparative example 5
The preparation method of the cathode material provided by the comparative example is the same as the example 1 in the specification of the Chinese patent document CN 114937771A.
Experimental example 1
The positive electrode materials prepared in the embodiment 1 and the comparative examples 1 to 2 are tested by adopting a scanning electron microscope, wherein the micro-morphology of the positive electrode material prepared in the embodiment 1 is shown in fig. 1 to 2, and as can be seen from fig. 1 to 2, the surface of the positive electrode material prepared in the embodiment 1 is provided with a layer of obvious cladding, namely a lithium decanoate modified layer; the particle size of the positive electrode material was 10.0. Mu.m.
While no coating was observed on the surface of the cathode materials synthesized in comparative examples 1 and 2, see fig. 3 to 6.
Experimental example 2
The Specific Surface Areas (SSA) of the positive electrode materials prepared in examples 1 to 9 and comparative examples 1 to 5 were measured by heating at 200 ℃ for 1 hour in a liquid nitrogen atmosphere using a Bei Shide specific surface area tester, and the results are shown in table 1.
TABLE 1
| LiOH/％ | Li 2 CO 3 /％ | Total alkali/%) | SSA(m 2 /g) | |
| Example 1 | 0.11 | 0.34 | 0.45 | 0.62 |
| Example 2 | 0.09 | 0.38 | 0.47 | 0.63 |
| Example 3 | 0.09 | 0.34 | 0.43 | 0.62 |
| Example 4 | 0.10 | 0.39 | 0.49 | 0.63 |
| Example 5 | 0.11 | 0.35 | 0.46 | 0.65 |
| Example 6 | 0.06 | 0.34 | 0.4 | 0.64 |
| Example 7 | 0.07 | 0.39 | 0.46 | 0.64 |
| Example 8 | 0.09 | 0.40 | 0.49 | 0.63 |
| Example 9 | 0.08 | 0.40 | 0.48 | 0.64 |
| Comparative example 1 | 0.94 | 0.85 | 1.79 | 1.25 |
| Comparative example 2 | 0.88 | 0.90 | 1.78 | 1.14 |
| Comparative example 3 | 0.10 | 0.41 | 0.51 | 0.84 |
| Comparative example 4 | 0.87 | 0.95 | 1.82 | 0.95 |
| Comparative example 5 | 0.91 | 0.92 | 1.83 | 0.99 |
As can be seen from table 1, the total alkali content of the cathode materials synthesized in examples 1 to 9 was lower than that of comparative examples 1 to 5, and the specific surface area SSA satisfied 0.62m 2 /g≤SSA≤0.65m 2 The fact that the organic acid and the residual alkali (Li) on the surface of the nickelic oxide are treated by the nickelic oxide modified method provided by the invention 2 O、LiOH、Li 2 CO 3 ) And carrying out chemical reaction to reduce the content of residual alkali and form a lithium salt modified layer of organic acid coating the surface of the high nickel oxide, wherein the modified layer can effectively control the specific surface area of the positive electrode material to be in the proper range.
Experimental example 3
Taking a proper amount of the positive electrode materials of examples 1-9 and comparative examples 1-5 to prepare homogenate, and coating the homogenate on an aluminum foil to prepare a positive electrode piece; the positive electrode material comprises the following components in percentage by mass: conductive carbon black: polyvinylidene fluoride cement =92, the solid content of polyvinylidene fluoride cement is 6.05%.
The prepared positive pole piece is subjected to buckling assembly by adopting a BR2032 shell (a button cell comprises a set of button cell shell and internal components, the types of general button cell shells are BR2032, CR2025, CR2016 and the like, BR2032 or CR2032 cell shells are commonly used in a laboratory), and then electrochemical test is carried out on a cell performance test system, wherein the test voltage range is 3.0-4.3V. The cells were subjected to a charge-discharge cycle test at a discharge efficiency of 0.1C, and two weeks after the cycle, the charge-discharge test was performed at 1C for 50 weeks. The average value of each group is obtained, and the test results of the average first discharge specific capacity, the average first discharge efficiency (namely, first effect) and the normal-temperature cycle retention rate (namely, 50-week retention rate) of the battery are shown in table 2.
TABLE 2
As can be seen from table 2, compared with comparative examples 1 to 5, in examples 1 to 9, after being treated with the specific organic acid of the present invention, the surface residual alkali of the high-nickel polycrystalline positive electrode material is effectively reduced, and a layer of lithium salt of organic acid is coated, so that the positive electrode material has higher 0.1C specific discharge capacity, first efficiency and cycle retention rate, which indicates that the lithium salt modified layer of organic acid in the positive electrode material provided by the present invention can improve the conductivity of lithium ions, and is beneficial to electron transfer, thereby improving the 0.1C specific discharge capacity and first efficiency of the positive electrode material, and meanwhile, the modified layer can effectively inhibit the contact between the electrolyte and the positive electrode material, reduce the occurrence of side reactions, and thereby improve the cycle performance of the positive electrode material. The electrochemical performance of the positive electrode materials in comparative examples 1 and 2 is poor, because more residual alkali still exists on the surface of the positive electrode material, and the diffusion and transfer of lithium ions and electrons in the positive electrode material are inhibited, so that the electrochemical performance of the positive electrode material is reduced.
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 therefrom are within the scope of the invention.
Claims (10)
1. A method for modifying high nickel oxide is characterized by comprising the following steps:
mixing organic acid and a volatile organic solvent to prepare an organic acid solution, wherein the organic acid is at least one of capric acid, oxalic acid and tartaric acid;
mixing the nickelic oxide with the organic acid solution, reacting under stirring, removing the volatile organic solvent, and drying.
2. The method for modifying nickel oxide according to claim 1, wherein the molar concentration of the organic acid in the organic acid solution is 2 to 4mol/L.
3. The method for modifying nickel oxide according to claim 1 or 2, wherein the molar ratio of the nickel oxide to the organic acid is 1:0.01 to 0.04.
4. The method for modifying nickel oxide according to claim 1, wherein the general chemical structure of the nickel oxide is Li 1.06 Ni a Co b Mn c O 2 Wherein a is more than or equal to 0.95 and less than or equal to 0.99,0.005 and less than or equal to 0.03,0.005 and less than or equal to c and less than or equal to 0.15, and a + b + c =1.
5. The method for modifying nickelic oxide according to claim 1, wherein the reaction temperature is 60 to 80 ℃ and the reaction time is 15 to 30 hours.
6. The method of claim 1, wherein the volatile organic solvent is at least one of acetone, methyl ethyl ketone, cyclohexanone, dioxane, trichloroethylene, and dichloromethane; and/or the drying temperature is 100-150 ℃, and the drying time is 5-10 h.
7. A positive electrode material produced by the method according to any one of claims 1 to 6, characterized in that the specific surface area of the positive electrode material is 0.62 to 0.65m 2 /g。
8. The positive electrode material according to claim 7, comprising a high nickel oxide and a modification layer covering at least a part of a surface of the high nickel oxide, wherein the modification layer is a lithium salt of the organic acid.
9. The positive electrode material according to claim 7 or 8, wherein the median particle diameter of the positive electrode material is 9.0 to 11.0 μm.
10. A lithium ion battery comprising the positive electrode material according to any one of claims 7 to 9.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116454285A (en) * | 2023-06-16 | 2023-07-18 | 中节能万润股份有限公司 | Method for reducing residual alkali on surface of layered positive electrode material of sodium ion battery and application |
| CN117543007A (en) * | 2024-01-09 | 2024-02-09 | 华北电力大学 | High-nickel ternary nickel-cobalt-aluminum positive electrode material and preparation method and application thereof |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116454285A (en) * | 2023-06-16 | 2023-07-18 | 中节能万润股份有限公司 | Method for reducing residual alkali on surface of layered positive electrode material of sodium ion battery and application |
| CN117543007A (en) * | 2024-01-09 | 2024-02-09 | 华北电力大学 | High-nickel ternary nickel-cobalt-aluminum positive electrode material and preparation method and application thereof |
| CN117543007B (en) * | 2024-01-09 | 2024-03-29 | 华北电力大学 | High-nickel ternary nickel-cobalt-aluminum positive electrode material and preparation method and application thereof |
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