CN117117110A - Modification method of ternary positive electrode material, modified ternary positive electrode material and lithium ion battery - Google Patents
Modification method of ternary positive electrode material, modified ternary positive electrode material and lithium ion battery Download PDFInfo
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- 239000007774 positive electrode material Substances 0.000 title claims abstract description 85
- 238000002715 modification method Methods 0.000 title claims abstract description 19
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 9
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 9
- 239000000843 powder Substances 0.000 claims abstract description 59
- 239000000463 material Substances 0.000 claims abstract description 38
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 claims abstract description 27
- 239000004327 boric acid Substances 0.000 claims abstract description 27
- 238000000034 method Methods 0.000 claims abstract description 24
- 238000002156 mixing Methods 0.000 claims abstract description 21
- 230000008569 process Effects 0.000 claims abstract description 13
- 238000007873 sieving Methods 0.000 claims description 16
- 230000004048 modification Effects 0.000 claims description 5
- 238000012986 modification Methods 0.000 claims description 5
- 239000002243 precursor Substances 0.000 claims description 5
- 229910013716 LiNi Inorganic materials 0.000 claims description 3
- 239000010406 cathode material Substances 0.000 claims 1
- 239000003513 alkali Substances 0.000 abstract description 22
- 239000000654 additive Substances 0.000 abstract description 4
- 230000000996 additive effect Effects 0.000 abstract description 4
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 abstract description 4
- 229910052808 lithium carbonate Inorganic materials 0.000 abstract description 4
- 238000012545 processing Methods 0.000 abstract description 4
- 230000000052 comparative effect Effects 0.000 description 10
- 230000014759 maintenance of location Effects 0.000 description 8
- 238000012360 testing method Methods 0.000 description 7
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 description 6
- 229910015872 LiNi0.8Co0.1Mn0.1O2 Inorganic materials 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- 238000002360 preparation method Methods 0.000 description 4
- 238000001878 scanning electron micrograph Methods 0.000 description 4
- 238000005406 washing Methods 0.000 description 4
- 239000003054 catalyst Substances 0.000 description 3
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 3
- 239000011248 coating agent Substances 0.000 description 3
- 238000000576 coating method Methods 0.000 description 3
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 description 2
- 230000006978 adaptation Effects 0.000 description 2
- 239000010405 anode material Substances 0.000 description 2
- 238000012512 characterization method Methods 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000011267 electrode slurry Substances 0.000 description 2
- 238000005245 sintering Methods 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 101150058243 Lipf gene Proteins 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- 239000006230 acetylene black Substances 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 239000006258 conductive agent Substances 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 238000000265 homogenisation Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000002427 irreversible effect Effects 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000012046 mixed solvent Substances 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- -1 polyethylene Polymers 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000008961 swelling Effects 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/362—Composites
- H01M4/364—Composites as mixtures
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- 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
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
- H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention provides a modification method of a ternary positive electrode material, a modified ternary positive electrode material and a lithium ion battery. According to the modification method provided by the invention, NCM ternary positive electrode active material is screened by a pair of rollers to obtain NCM ternary positive electrode active material powder; then putting the NCM ternary positive electrode active material powder and boric acid powder into a high-speed mixer for mixing to obtain a modified material; in the process, boric acid powder is controlled to be a certain additive amount and a certain mixing condition is controlled, so that the residual alkali content on the surface of the NCM ternary positive electrode material can be effectively reduced, the gram capacity and the cycle performance of the ternary material are ensured, in addition, the method disclosed by the invention is simple in process, the cost can be reduced, the processing performance of the material is optimized, the utilization rate of lithium carbonate is improved, and the electrochemical performance of the material is improved.
Description
Technical Field
The invention relates to the field of lithium ion battery materials, in particular to a modification method of a ternary positive electrode material, a modified ternary positive electrode material and a lithium ion battery.
Background
Too high a residual alkali content on the surface of the positive electrode material can have a number of negative effects on electrochemical performance. Firstly, it affects the coating, and the NCM ternary positive electrode materials easily form jelly-like during the homogenization process, mainly because of the too high basic oxide content of their surface, which absorbs water. The effect of surface alkaline compounds on electrochemical performance is mainly manifested by increased irreversible capacity loss while deteriorating cycle performance. In addition, for NCM ternary positive electrode materials, li at the surface 2 CO 3 Decomposition at high voltage is one of the main reasons for causing the swelling of the battery to bring about potential safety hazards to the service performance of the battery. Therefore, the reduction of the residual alkali content on the surface is of great importance for the practical application of ternary materials in power batteries.
At present, the technology of washing the ternary material with water and then secondarily sintering (washing with water and secondary sintering) at a lower temperature is commonly adopted by domestic manufacturers to reduce the residual alkali content on the surface of the NCM ternary positive electrode material. The method can clean the surface residual alkali thoroughly, but has obvious defects, the multiplying power and the cycle performance of the ternary material after treatment are obviously reduced and can not meet the use requirement of the power battery, and the cost is increased due to water washing and secondary burning.
The invention aims to provide a method for reducing the residual alkali content on the surface of an NCM ternary positive electrode material, which is simple and convenient to operate and low in cost, so as to reduce the potential safety hazard problem of the gas expansion bulge of a finished battery while improving the material homogenate coating performance.
Disclosure of Invention
In view of the above, the invention provides a modification method of a ternary positive electrode material, a modified ternary positive electrode material and a lithium ion battery. The modification method can effectively reduce the residual alkali content of the surface of the NCM ternary positive electrode material, ensure the multiplying power and the cycle performance of the ternary material, and has simple process and low cost.
The invention provides a modification method of a ternary positive electrode material, which comprises the following steps:
a) Sieving the NCM ternary positive electrode active material by a pair of rollers to obtain NCM ternary positive electrode active material powder;
b) Putting the NCM ternary positive electrode active material powder and boric acid powder into a high-speed mixer for mixing to obtain a modified material;
the mixing conditions are as follows: the rotating speed is 500-1000 r/min, and the time is 40-60 min.
Preferably, in step b), the boric acid powder is added to the NCM ternary positive electrode active material powder in a proportion of 500 to 2000ppm.
Preferably, in step a), the NCM ternary positive electrode active material has the general formula LiNi x Co y Mn z O 2 Wherein x+y+z=1 and the molar ratio of Ni to Co to Mn is 8:1:1.
Preferably, in step a), the sieving is by a 200-500 mesh sieve.
Preferably, in step b), the boric acid powder is added to the NCM ternary positive electrode active material powder in a proportion of 700ppm.
Preferably, in step b), the mixing conditions are: the rotating speed is 700r/min, and the time is 40min.
Preferably, in step a), the sieving is a 325 mesh sieve.
Preferably, in step a), the NCM ternary positive electrode active material is prepared from precursor Ni x Co y Mn z (OH) 2 With Li 2 CO 3 Reacting to obtain the product; wherein x+y+z=1 and the molar ratio of Ni to Co to Mn is 8:1:1.
The invention also provides a modified ternary anode material prepared by the modification method in the technical scheme.
The invention also provides a lithium ion battery, wherein the positive electrode active material on the positive electrode is the modified ternary positive electrode material in the technical scheme.
According to the modification method provided by the invention, NCM ternary positive electrode active material is screened by a pair of rollers to obtain NCM ternary positive electrode active material powder; then putting the NCM ternary positive electrode active material powder and boric acid powder into a high-speed mixer for mixing to obtain a modified material; in the process, boric acid powder is controlled to be a certain additive amount and a certain mixing condition is controlled, so that the residual alkali content on the surface of the NCM ternary positive electrode material can be effectively reduced, the gram capacity and the cycle performance of the ternary material are ensured, in addition, the method disclosed by the invention is simple in process, the cost can be reduced, the processing performance of the material is optimized, the utilization rate of lithium carbonate is improved, and the electrochemical performance of the material is improved.
The test result shows that the product of the invention has the surface residual alkali LiOH content of less than 0.025 percent, li 2 CO 3 The content is below 0.2%, the gram capacity of the first discharge is above 203mAh/g, the normal-temperature capacity retention rate is above 92%, the high Wen Rongliang retention rate is above 88%, and the catalyst has low residual alkali content, high gram capacity and excellent cycle performance.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only embodiments of the present invention, and that other drawings can be obtained according to the provided drawings without inventive effort for a person skilled in the art.
FIG. 1 is an SEM image of the product obtained in comparative example 1;
FIG. 2 is an SEM image of the product obtained in example 1.
Detailed Description
The invention provides a modification method of a ternary positive electrode material, which comprises the following steps:
a) Sieving the NCM ternary positive electrode active material by a pair of rollers to obtain NCM ternary positive electrode active material powder;
b) Putting the NCM ternary positive electrode active material powder and boric acid powder into a high-speed mixer for mixing to obtain a modified material;
the mixing conditions are as follows: the rotating speed is 500-1000 r/min, and the time is 40-60 min.
According to the modification method provided by the invention, NCM ternary positive electrode active material is screened by a pair of rollers to obtain NCM ternary positive electrode active material powder; then putting the NCM ternary positive electrode active material powder and boric acid powder into a high-speed mixer for mixing to obtain a modified material; in the process, boric acid powder is controlled to be a certain additive amount and a certain mixing condition is controlled, so that the residual alkali content on the surface of the NCM ternary positive electrode material can be effectively reduced, the gram capacity and the cycle performance of the ternary material are ensured, in addition, the method disclosed by the invention is simple in process, the cost can be reduced, the processing performance of the material is optimized, the utilization rate of lithium carbonate is improved, and the electrochemical performance of the material is improved.
Regarding step a):
a) And sieving the NCM ternary positive electrode active material by a pair of rollers to obtain NCM ternary positive electrode active material powder.
In the invention, the general formula of the NCM ternary positive electrode active material is LiNi x Co y Mn z O 2 Wherein x+y+z=1. Preferably, in the above formula, the molar ratio of Ni to Co to Mn is 8:1:1. In the invention, the NCM ternary positive electrode active material is preferably prepared from a precursor Ni x Co y Mn z (OH) 2 With Li 2 CO 3 Is prepared by reaction, in particular to a precursor Ni x Co y Mn z (OH) 2 With Li 2 CO 3 The preparation is carried out by roasting, other details in the preparation process are not particularly limited, and the preparation is carried out according to the conventional operation in the field; wherein, the values of x, y and z are consistent with the values described above, and are not repeated here.
In the invention, ni is used as a precursor x Co y Mn z (OH) 2 With Li 2 CO 3 And (3) roasting to obtain the NCM ternary positive electrode active material, and then sieving by a pair of rollers. The sieving is preferably 200-500 mesh sieving, and can be 200Mesh, 250 mesh, 300 mesh, 325 mesh, 350 mesh, 400 mesh, 450 mesh, 500 mesh, more preferably 325 mesh. And (3) performing the treatment to obtain NCM ternary positive electrode active material powder.
Regarding step b):
b) And (3) putting the NCM ternary positive electrode active material powder and boric acid powder into a high-speed mixer for mixing to obtain the modified material.
In the present invention, the boric acid powder is preferably added in a proportion of 500 to 2000ppm, that is, the mass ratio of boric acid powder to NCM ternary positive electrode active material powder is 500 to 2000ppm, and if the addition amount is too low, the electrochemical performance of the material cannot be effectively improved, and if the addition amount is too high, the gram capacity of the material is reduced, and the above-mentioned addition proportion may be specifically 500ppm, 600ppm, 700ppm, 800ppm, 900ppm, 1000ppm, 1100ppm, 1200ppm, 1300ppm, 1400ppm, 1500ppm, 1600ppm, 1700ppm, 1800ppm, 1900ppm, 2000ppm.
In the invention, NCM ternary positive electrode active material powder and boric acid powder are put into a high-speed mixer for mixing, specifically, after the materials are put into the high-speed mixer, circulating water is closed, and stirring and mixing are started. In the invention, the rotation speed of the mixing is 500-1000 r/min, specifically 500r/min, 600r/min, 700r/min, 800r/min, 900r/min, 1000r/min, preferably 700r/min. The mixing time is preferably 40-60 min, specifically 40min, 45min, 50min, 55min, 60min, preferably 40min. If the speed is too low or the time is too short, the materials cannot be effectively mixed, if the speed is too high, the materials are easily broken, the ideal granularity of the invention is not easily obtained, and if the time is too long, the segregation of the materials is easily caused, and the invention is beneficial to improving the performance of the materials under the speed and the time range. After the above treatment, the modified NCM ternary positive electrode active material is obtained.
The invention also provides a modified ternary anode material prepared by the preparation method in the technical scheme.
The invention also provides a lithium ion battery, wherein the positive electrode active material on the positive electrode is the modified ternary positive electrode material in the technical scheme.
According to the modification method provided by the invention, NCM ternary positive electrode active material is screened by a pair of rollers to obtain NCM ternary positive electrode active material powder; then putting the NCM ternary positive electrode active material powder and boric acid powder into a high-speed mixer for mixing to obtain a modified material; in the process, boric acid powder is controlled to be a certain additive amount and a certain mixing condition is controlled, so that the residual alkali content on the surface of the NCM ternary positive electrode material can be effectively reduced, the gram capacity and the cycle performance of the ternary material are ensured, in addition, the method disclosed by the invention is simple in process, the cost can be reduced, the processing performance of the material is optimized, the utilization rate of lithium carbonate is improved, and the electrochemical performance of the material is improved.
The test result shows that the product of the invention has the surface residual alkali LiOH content of less than 0.025 percent, li 2 CO 3 The content is below 0.2%, the gram capacity of the first discharge is above 203mAh/g, the normal-temperature capacity retention rate is above 92%, the high Wen Rongliang retention rate is above 88%, and the catalyst has low residual alkali content, high gram capacity and excellent cycle performance.
For a further understanding of the present invention, preferred embodiments of the invention are described below in conjunction with the examples, but it should be understood that these descriptions are merely intended to illustrate further features and advantages of the invention, and are not limiting of the claims of the invention.
Example 1
a) NCM ternary positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O 2 And (5) sieving by a 325-mesh sieve to obtain NCM ternary positive electrode active material powder.
b) Boric acid powder was added to 1kg of the above NCM ternary positive electrode active material powder at a ratio of 1000ppm, and mixed at 700r/min for 40min in a high-speed mixer to obtain a modified material.
Example 2
a) NCM ternary positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O 2 And (5) sieving by a 325-mesh sieve to obtain NCM ternary positive electrode active material powder.
b) Boric acid powder was added to 1kg of the above NCM ternary positive electrode active material powder at a ratio of 700ppm, and mixed in a high-speed mixer at 700r/min for 40min to obtain a modified material.
Example 3
a) NCM ternary positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O 2 And (5) sieving by a 325-mesh sieve to obtain NCM ternary positive electrode active material powder.
b) Boric acid powder was added to 1kg of the above NCM ternary positive electrode active material powder at a ratio of 1000ppm, and mixed at 500r/min for 40min in a high-speed mixer to obtain a modified material.
Example 4
a) NCM ternary positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O 2 And (5) sieving by a 325-mesh sieve to obtain NCM ternary positive electrode active material powder.
b) Boric acid powder was added to 1kg of the above NCM ternary positive electrode active material powder at a ratio of 1000ppm, and mixed in a high-speed mixer at 700r/min for 20min to obtain a modified material.
Comparative example 1
a) NCM ternary positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O 2 And (5) sieving by a 325-mesh sieve to obtain NCM ternary positive electrode active material powder.
b) 1kg of NCM ternary positive electrode active material powder is washed in a stripping reaction kettle for 10min at a rotating speed of 180r/min, and the washing solid content is 20%. After that, drying to obtain the product.
Comparative example 2
The procedure is as in example 2, except that boric acid powder is not added in step b).
Comparative example 3
The procedure is as in example 1, except that the boric acid powder in step b) is replaced by citric acid.
Example 6: product testing
1. SEM characterization
SEM characterization of the products obtained in example 1 and comparative example 1, respectively, is shown in FIGS. 1-2, FIG. 1 being an SEM image of the product obtained in comparative example 1, and FIG. 2 being an SEM image of the product obtained in example 1.
2. Testing of pH and surface residual alkali and gram Capacity
The products obtained in examples 1 to 4 and comparative examples 1 to 3 were tested for pH and surface residual alkali, respectively, and the results are shown in Table 1.
Assembling a battery:
9g of positive electrode active material, 0.5g of acetylene black conductive agent and 0.5g of PVDF binder are weighed, mixed, added with NMP solvent until the solid content is 2%, and uniformly dispersed to obtain positive electrode slurry. And coating the positive electrode slurry on the two sides of an aluminum foil (with the thickness of 6 mu m), and drying to obtain the positive electrode plate. Positive electrode sheet, metal lithium sheet negative electrode sheet, polyethylene diaphragm (thickness 25 μm), liPF 6 The electrolyte (concentration 1mol/L, solvent is mixed solvent of ethyl carbonate EC: dimethyl carbonate DMC: diethyl carbonate EMC volume ratio=1:1:1) is assembled into CR2032 button cell in an anaerobic glove box.
The materials obtained in examples 1 to 4 and comparative examples 1 to 3 were used as positive electrode active materials, respectively, and assembled into a button cell according to the above-described procedure, and then charge and discharge tests were performed at a charge and discharge rate of 0.1C/0.1C in a voltage range of 4.4 to 3.0V, to measure gram capacity for the first discharge. In addition, the cycle performance test was performed under the above voltage and rate conditions, and the capacity retention after 50 weeks of cycle at normal temperature (25 ℃) and the capacity retention after 50 weeks of cycle at high temperature (45 ℃) were respectively tested, and the results are shown in table 1.
Table 1: product test results
As can be seen from the test results in Table 1, the products obtained in examples 1 to 4 of the present invention have a residual alkali LiOH content of less than 0.025%, li 2 CO 3 The content is below 0.2%, the gram capacity of the first discharge is above 203mAh/g, the normal-temperature capacity retention rate is above 92%, the high Wen Rongliang retention rate is above 88%, and the catalyst has low residual alkali content, high gram capacity and excellent cycle performance. Compared with comparative example 2, the surface residual alkali of example 2 is reduced, and the gram capacity and the cycle performance are improved at the same time, which proves that the boric acid powder is introduced,not only can reduce the content of residual alkali, but also can improve gram capacity and cycle performance. Compared with comparative example 3, the gram capacity and the cycle performance of example 1 are obviously improved, and the residual surface alkali content is kept low, so that the improvement of the invention by adopting the specific boric acid compared with other similar substances can be proved, and the gram capacity and the cycle performance can be simultaneously improved and both the low residual surface alkali content and the improved gram capacity and the cycle performance can be simultaneously considered.
The principles and embodiments of the present invention have been described herein with reference to specific examples, the description of which is intended only to aid in understanding the method of the invention and its core concept, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. It should be noted that it will be apparent to those skilled in the art that various modifications and adaptations of the invention can be made without departing from the principles of the invention and these modifications and adaptations are intended to be within the scope of the invention as defined in the following claims. The scope of the patent protection is defined by the claims and may include other embodiments that occur to those skilled in the art. Such other embodiments are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.
Claims (10)
1. The modification method of the ternary positive electrode material is characterized by comprising the following steps of:
a) Sieving the NCM ternary positive electrode active material by a pair of rollers to obtain NCM ternary positive electrode active material powder;
b) Putting the NCM ternary positive electrode active material powder and boric acid powder into a high-speed mixer for mixing to obtain a modified material;
the mixing conditions are as follows: the rotating speed is 500-1000 r/min, and the time is 40-60 min.
2. The modification method according to claim 1, wherein in the step b), the boric acid powder and the NCM ternary positive electrode active material powder are added in a ratio of 500 to 2000ppm.
3. The modification method according to claim 1, wherein in the step a), the NCM ternary positive electrode active material has a general formula LiNi x Co y Mn z O 2 Wherein x+y+z=1 and the molar ratio of Ni to Co to Mn is 8:1:1.
4. The modification process according to claim 1, wherein in step a), the sieving is performed by a 200 to 500 mesh sieve.
5. The modification method according to claim 1 or 2, wherein in the step b), the addition ratio of the boric acid powder to the NCM ternary positive electrode active material powder is 700ppm.
6. The modification process according to claim 1, wherein in step b), the mixing conditions are: the rotating speed is 700r/min, and the time is 40min.
7. The modification process according to claim 1 or 4, wherein in step a), the sieving is a 325 mesh sieve.
8. The modification method according to claim 1, wherein in step a), the NCM ternary positive electrode active material is composed of precursor Ni x Co y Mn z (OH) 2 With Li 2 CO 3 Reacting to obtain the product; wherein x+y+z=1 and the molar ratio of Ni to Co to Mn is 8:1:1.
9. A modified ternary cathode material made by the modification method of any one of claims 1-8.
10. A lithium ion battery wherein the positive electrode active material on the positive electrode is the modified ternary positive electrode material of claim 9.
Priority Applications (1)
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