ELECTROCHEMICAL APPARATUS AND ELECTRONIC APPARATUS
20240038995 ยท 2024-02-01
Assignee
Inventors
Cpc classification
H01M2004/021
ELECTRICITY
International classification
Abstract
An electrochemical apparatus includes a positive electrode, the positive electrode includes a current collector and a positive electrode mixture layer disposed on at least one surface of the current collector. The positive electrode mixture layer includes a positive electrode active substance and a binder. The binder includes a fluorine-containing polymer. In an XRD diffraction pattern of the fluorine-containing polymer, a diffraction peak A appears at 25 to 27 and corresponds to a (111) crystal plane, and a diffraction peak B appears at 37 to 39 and corresponds to a (022) crystal plane, where an area ratio of the diffraction peak A to the diffraction peak B satisfies 1A(111)/B(022)4.
Claims
1. An electrochemical apparatus, comprising a positive electrode, wherein the positive electrode comprises a current collector and a positive electrode mixture layer disposed on at least one surface of the current collector; and the positive electrode mixture layer comprises a positive electrode active substance and a binder; wherein the binder comprises a fluorine-containing polymer, and in an XRD diffraction pattern of the fluorine-containing polymer, a diffraction peak A appears at 25 to 27 and corresponds to a (111) crystal plane, and a diffraction peak B appears at 37 to 39 and corresponds to a (022) crystal plane, wherein 1A(111)/B(022)4, A(111) is an area of the diffraction peak A and B(022) is an area of the diffraction peak B.
2. The electrochemical apparatus according to claim 1, wherein in the XRD diffraction pattern of the fluorine-containing polymer, a diffraction peak C appears at 42 to 43 and corresponds to a (131) crystal plane.
3. The electrochemical apparatus according to claim 1, wherein a weight-average molecular weight of the binder is 800000 to 1100000.
4. The electrochemical apparatus according to claim 1, wherein a molecular weight distribution of the binder satisfies: 2.05Mw/Mn3.6, wherein Mn is a number-average molecular weight of the binder, and Mw is a weight-average molecular weight of the binder.
5. The electrochemical apparatus according to claim 1, wherein the fluorine-containing polymer comprises at least one selected from the group consisting of homopolymers or copolymers of vinylidene fluoride, hexafluoropropylene, pentafluoropropylene, tetrafluoropropylene, trifluoropropylene, perfluorobutene, hexafluorobutadiene, hexafluoroisobutylene, trifluoroethylene, trifluorochloroethylene, and tetrafluoroethylene.
6. The electrochemical apparatus according to claim 1, wherein an ultimate compacted density of the positive electrode mixture layer is 3.0 g/mm.sup.3 to 4.5 g/mm.sup.3.
7. The electrochemical apparatus according to claim 1, wherein an adhesion force between the positive electrode mixture layer and the current collector is 15 N/m to 35 N/m.
8. The electrochemical apparatus according to claim 1, wherein a D.sub.v50 of the positive electrode active substance is 0.5 m to 35 m.
9. The electrochemical apparatus according to claim 1, wherein a thickness of the current collector is 7 m to 20 m.
10. The electrochemical apparatus according to claim 1, wherein the positive electrode satisfies at least one of the following characteristics: (a) a compacted density of the positive electrode mixture layer is 4.1 g/mm.sup.3 to 4.4 g/mm.sup.3; (b) a D.sub.v50 of the positive electrode active substance is 10 m to 25 m; (c) a single-sided thickness of the positive electrode mixture layer is 40.5 m to 55 m; (d) a thickness of the current collector is 8 m to 12 m; or (e) a mass percentage of the binder in the positive electrode mixture layer is 1% to 5%.
11. An electronic apparatus, comprising an electrochemical apparatus, the electrochemical apparatus comprises a positive electrode, wherein the positive electrode comprises a current collector and a positive electrode mixture layer disposed on at least one surface of the current collector; and the positive electrode mixture layer comprises a positive electrode active substance and a binder; wherein the binder comprises a fluorine-containing polymer, and in an XRD diffraction pattern of the fluorine-containing polymer, a diffraction peak A appears at 25 to 27 and corresponds to a (111) crystal plane, and a diffraction peak B appears at 37 to 39 and corresponds to a (022) crystal plane, wherein 1A(111)/B(022)4, A(111) is an area of the diffraction peak A and B(022) is an area of the diffraction peak B.
12. The electronic apparatus according to claim 11, wherein in the XRD diffraction pattern of the fluorine-containing polymer, a diffraction peak C appears at 42 to 43 and corresponds to a (131) crystal plane.
13. The electronic apparatus according to claim 11, wherein a weight-average molecular weight of the binder is 800000 to 1100000.
14. The electronic apparatus according to claim 11, wherein a molecular weight distribution of the binder satisfies: 2.05Mw/Mn3.6, wherein Mn is a number-average molecular weight of the binder, and Mw is a weight-average molecular weight of the binder.
15. The electronic apparatus according to claim 11, wherein the fluorine-containing polymer comprises at least one selected from the group consisting of homopolymers or copolymers of vinylidene fluoride, hexafluoropropylene, pentafluoropropylene, tetrafluoropropylene, trifluoropropylene, perfluorobutene, hexafluorobutadiene, hexafluoroisobutylene, trifluoroethylene, trifluorochloroethylene, and tetrafluoroethylene.
16. The electronic apparatus according to claim 11, wherein an ultimate compacted density of the positive electrode mixture layer is 3.0 g/mm.sup.3 to 4.5 g/mm.sup.3.
17. The electronic apparatus according to claim 11, wherein an adhesion force between the positive electrode mixture layer and the current collector is 15 N/m to 35 N/m.
18. The electronic apparatus according to claim 11, wherein a D.sub.v50 of the positive electrode active substance is 0.5 m to 35 m.
19. The electronic apparatus according to claim 11, wherein a thickness of the current collector is 7 m to 20 m.
20. The electronic apparatus according to claim 11, wherein the positive electrode satisfies at least one of the following characteristics: (a) a compacted density of the positive electrode mixture layer is 4.1 g/mm.sup.3 to 4.4 g/mm.sup.3; (b) a D.sub.v50 of the positive electrode active substance is 10 m to 25 m; (c) a single-sided thickness of the positive electrode mixture layer is 40.5 m to 55 m; (d) a thickness of the current collector is 8 m to 12 m; or (e) a mass percentage of the binder in the positive electrode mixture layer is 1% to 5%.
Description
BRIEF DESCRIPTION OF DRAWINGS
[0042] To describe the technical solutions in this application and the prior art more clearly, the following briefly describes the accompanying drawings required for describing embodiments and the prior art. Apparently, the accompanying drawings in the following description show merely some embodiments of this application.
[0043]
[0044]
DETAILED DESCRIPTION
[0045] To make the objectives, technical solutions, and advantages of this application more comprehensible, the following further describes this application in detail with reference to accompanying drawings and embodiments. Apparently, the described embodiments are only some but not all of the embodiments of this application. All other embodiments obtained by persons of ordinary skill in the art based on this application shall fall within the protection scope of this application.
[0046] It should be noted that in specific embodiments of this application, an example in which a lithium-ion battery is used as an electrochemical apparatus is used to illustrate this application. However, the electrochemical apparatus of this application is not limited to the lithium-ion battery.
[0047] As shown in
[0048] As shown in
EXAMPLES
[0049] The following describes some embodiments of this application more specifically by using examples and comparative examples. Various tests and evaluations are performed according to the following methods. In addition, unless otherwise specified, part and % are based on weight.
[0050] Test Methods and Equipment
[0051] XRD Test
[0052] 1.0 g of binder sample prepared in each example and comparative example was taken and put into a recess of a glass sample holder, compressed and smoothed with a glass sheet, and tested with an X-ray diffractometer (model: Bruker, D8) according to JJS K 0131-1996 General Rules for X-ray Diffraction Analysis to obtain an XRD diffraction pattern of the binder, where the test voltage was set to 40 kV, current to 30 mA, scanning angle to a range of 10 to 90, and scanning step to 0.0167, with a time set for each scanning step being 0.24 s.
[0053] Adhesion Force Test
[0054] (1) A discharged lithium-ion battery under test was disassembled, and then a positive electrode plate was taken out. The positive electrode plate was soaked in DMO (dimethyl oxalate) for 30 min to remove electrolyte and by-products on the surface of the positive electrode plate, and then dried in a fume hood at 25 C. for 4 hours. The dried positive electrode plate was taken out and then cut into a sample being 30 mm wide and 100 mm long with a blade.
[0055] (2) A double-sided tape being 20 mm wide and 90 mm long was pasted to a steel plate.
[0056] (3) The sample obtained by cutting in step (1) was pasted to the double-sided tape, with the test surface facing downward to be attached to the double-sided tape.
[0057] (4) A paper tape with the same width as the sample and a length of 80 mm greater than that of the sample was inserted below the sample and fastened with a wrinkle stipple.
[0058] (5) A tensile machine (brand: Sunstest, and model: Instron 3365) was powered on, and after an indicator lit, a restraint block was adjusted to an appropriate position.
[0059] (6) The sample prepared in (4) was fastened on a test bench, and the paper tape was folded upward and fastened with clamps. The paper tape was pulled at a speed of 10 mm/min and within a test range of 0 mm to 40 mm at 90, so that a positive electrode mixture layer and a current collector that were attached to the surface of the double-sided tape were pulled apart until the end of the test.
[0060] (7) The test data was saved according to software prompts, to obtain adhesion force data between the positive electrode mixture layer and the current collector. After the test was completed, the sample was taken out, and the instrument was turned off.
[0061] Brittle Fracture Test of Electrode Plate
[0062] At 25 C. and 40% RH (relative humidity), the cold-pressed positive electrode plate prepared in each example and comparative example was dried in the fume hood for 4 hours, and then the dried positive electrode plate was taken out. Then, the positive electrode plate was cut into a sample of 4 cm25 cm. The sample was pre-folded along its longitudinal direction, the pre-folded test film was placed on the platform of the test bench, and a 2 kg cylinder was used to roll the pre-folded sample twice in the same direction. The sample was folded back along the longitudinal crease, and the electrode plate was unfolded and observed against the light. If the folded electrode plate fractured or the light transmission parts formed a line, the result was defined as severe. If the folded electrode plate showed scattered light transmission, the result was defined as slight. If the folded electrode plate had no light transmission or fracture, the result was defined as none.
[0063] Ultimate Compacted Density Test of Positive Electrode Mixture Layer
[0064] Compacted density of positive electrode mixture layer=mass of positive electrode active substance layer per unit area (g/mm.sup.2)/thickness of positive electrode mixture layer (mm). A discharged lithium-ion battery under test was disassembled, and then a positive electrode plate was taken out. The positive electrode plate was soaked in DMO (dimethyl oxalate) for 30 min to remove electrolyte and by-products on the surface of the positive electrode plate, and then dried in the fume hood for 4 hours. The dried positive electrode plate was taken out, and the thickness of the positive electrode mixture layer in the positive electrode plate was measured with a ten-thousandths micrometer. Then, the positive electrode active substance layer per unit area in the positive electrode plate was scraped with a scraper, the mass of the positive electrode active substance layer per unit area in the positive electrode plate was weighed with a balance, and the compacted density of the positive electrode mixture layer was calculated according to the foregoing formula.
[0065] The ultimate compacted density of the positive electrode mixture layer is a corresponding compacted density of the positive electrode mixture layer when the positive electrode is subjected to the maximum press amount (corresponding to the maximum equipment pressure and the minimum roller gap).
[0066] Measurement of Weight-Average Molecular Weight and Number-Average Molecular Weight of Binder
[0067] Molecular weight and molecular weight distribution were tested using an advanced polymer chromatography (ACQUITY APC) and a detector (ACQUITY refractive index detector) with reference to GB/T 21863-2008 Gel Permeation Chromatography. The test steps were as follows: (1) Power on and warm up: the chromatographic column and pipeline were installed, the console, test power supply, and the like were turned on in sequence, and then the test software Empower was opened. (2) Parameter setting and sample volume: 0 L to 50 L (depending on the sample concentration); pump flow rate: 0.2 mL/min; mobile phase: NMP solution with 30 mol/L LiBr; sealing cleaning solution: isopropanol; precolumn: PL gel 10 um MiniMIX-B Guard (size: 50 mm4.6 mm2); analytical phase: PL gel 10 um MiniMIX-B (size: 250 mm4.6 mm); standard sample: polystyrene standards; running time: 30 min; detector: ACQUITY refractive index (RI) detector; column oven temperature: 90 C.; and detector temperature: 55 C. (3) Sample test: a. standard sample and test sample preparation: 0.002 g to 0.004 g standard sample/test sample were weighed and added to 2 mL mobile phase liquid to prepare 0.1% to 0.5% mixed standard sample, and then the sample was placed in a refrigerator for more than 8 h; and b. standard liquid/sample test: the sample group under test was edited, the established sample group method was selected, and after the baseline stabilized, the run queue was clicked on to start testing the sample. (4) Data processing: a calibration curve was established using a chemical workstation according to the relationship between retention time and molecular weight, quantitative integration was performed on the sample chromatogram, and the chemical workstation automatically generated molecular weight and molecular weight distribution results.
[0068] Test of D.sub.v50 and D.sub.v10 of Positive Electrode Active Substance
[0069] D.sub.v50 of the positive electrode active substance was tested using a laser particle size analyzer.
[0070] Capacity Retention Rate Test:
[0071] At a test environment temperature of 25 C., the lithium-ion battery after formation was charged to a cut-off voltage of 4.45 V at a current of 0.7 C in a constant-current charging phase, and then charged to a cut-off current of 0.05 C at a constant voltage to stop the charging. After fully charged, the battery was left standing for 5 min, and then discharged to 3.0 V at a current of 0.5 C. This was one charge and discharge cycle. After 500 such charge and discharge cycles were conducted, a discharge capacity of the 500th cycle was divided by a discharge capacity of the first cycle to obtain the cycling capacity retention rate.
[0072] Thickness Swelling Test of Lithium-Ion Battery
[0073] Thickness of the lithium-ion battery was tested using a PPG plate thickness gauge. Thickness swelling rate of lithium-ion battery=(fully charged thickness after cyclingfirst fully charged thickness)/first fully charged thickness100%.
Example 1
[0074] <1-1. Preparation of Positive Electrode Plate>
[0075] <1-1-1. Preparation of Binder>
[0076] After a reactor with a volume of 25 L was evacuated and nitrogen was pumped to replace oxygen, 18 kg deionized water, 200 g sodium perfluorooctanoate solution with a mass concentration of 5%, and 80 g of paraffin wax (with a melting point of 60 C.) were put into the reactor, with a stirring speed adjusted to 130 rpm/min and temperature of the reactor raised to 85 C., and then vinylidene fluoride monomers were added to reach a reactor pressure of 5.0 MPa. 1.15 g of initiator dioctyl peroxydicarbonate was added to start a polymerization reaction. Then, the vinylidene fluoride monomers were added to maintain the reactor pressure at 5.0 MPa. 0.01 g of initiator was added in batches every 10 min, and a chain transfer agent HFC-4310 was added in four batches at conversion rates of 20%, 40%, 60%, and 80%, respectively, with 5 g added each time. A total of 5 kg vinylidene fluoride monomers were added for the reaction. The reaction continued until the pressure dropped to 4.0 MPa, and then degassing and material collecting were performed. The reaction time was 2 hours and 20 minutes. After centrifugation, washing, and drying, the binder PVDF was obtained. The PVDF had a weight-average molecular weight of 900000 and a molecular weight distribution of Mw/Mn=2.15. The binder had a diffraction peak A at 26.2, a diffraction peak B at 38.5, and a diffraction peak C at 42.2, and an area ratio of the diffraction peak A to the diffraction peak B satisfied A(111)/B(022)=1.0.
[0077] <1-1-2. Preparation of Positive Electrode Plate Containing Binder>
[0078] Positive electrode active substance lithium cobalt oxide (with D.sub.v50 of 15.6 m), acetylene black, and the prepared binder were mixed at a mass ratio of 96:2:2, then NMP was added as a solvent to obtain a slurry with a solid content of 75%, and the slurry was stirred to uniformity. The slurry was uniformly applied onto one surface of a 9 m thick aluminum foil and dried at 90 C., followed by cold pressing, to obtain a positive electrode plate with a 46 m thick positive electrode mixture layer. Then, the same steps were repeated on the other surface of the positive electrode plate to obtain a positive electrode plate coated with positive electrode active substance layers on two surfaces. The positive electrode plate was cut into a size of 74 mm867 mm and then welded with tabs for use.
[0079] <1-2. Preparation of Negative Electrode Plate>
[0080] Negative electrode active substance artificial graphite, styrene-butadiene rubber, and sodium carboxymethyl cellulose were mixed at a mass ratio of 96:2:2, then deionized water was added as a solvent to obtain a slurry with a solid content of 70%, and the slurry was stirred to uniformity. The slurry was uniformly applied onto one surface of an 8 m thick copper foil and dried at 110 C., followed by cold pressing, to obtain a negative electrode plate with a 50 m thick negative electrode mixture layer and one surface coated with a negative electrode active substance layer. Then, the same coating steps were repeated on the other surface of the negative electrode plate to obtain a negative electrode plate coated with negative electrode active substance layers on two surfaces. The negative electrode plate was cut into a size of 74 mm867 mm and then welded with tabs for use.
[0081] <1-3. Preparation of Separator>
[0082] A 15 m thick polyethylene (PE) porous polymer film was used as a separator.
[0083] <1-4. Preparation of Electrolyte>
[0084] In an environment with a water content less than 10 ppm, non-aqueous organic solvents ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) were mixed at a mass ratio of 1:1:1, and then lithium hexafluorophosphate (LiPF.sub.6) was added to the non-aqueous organic solvents for dissolving and mixing to uniformity, to obtain an electrolyte, where a concentration of LiPF.sub.6 was 1.15 mol/L.
[0085] <1-5. Preparation of Lithium-Ion Battery>
[0086] The prepared positive electrode plate, separator, and negative electrode plate were stacked in sequence, so that the separator was sandwiched between the positive electrode plate and the negative electrode plate for separation. Then the resulting stack was wound to obtain an electrode assembly. The electrode assembly was placed into an aluminum-plastic packaging bag and dehydrated at 80 C., and the prepared electrolyte was injected, followed by processes such as vacuum sealing, standing, formation, and shaping, to obtain a lithium-ion battery.
Example 2
[0087] Example 2 was the same as Example 1 except that in <Preparation of binder>, the reaction temperature was adjusted to 88 C., such that the area ratio of the diffraction peak A to the diffraction peak B of the binder satisfied A(111)/B(022)=1.5.
Example 3
[0088] Example 3 was the same as Example 1 except that in <Preparation of binder>, the reaction temperature was adjusted to 92 C., such that the area ratio of the diffraction peak A to the diffraction peak B of the binder satisfied A(111)/B(022)=2.4.
Example 4
[0089] Example 4 was the same as Example 1 except that in <Preparation of binder>, phenoxyethyl peroxydicarbonate was used as the initiator, such that the area ratio of the diffraction peak A to the diffraction peak B of the binder satisfied A(111)/B(022)=3.2.
Example 5
[0090] Example 5 was the same as Example 1 except that in <Preparation of binder>, phenoxyethyl peroxydicarbonate was used as the initiator and the reaction temperature was adjusted to 90 C., such that the area ratio of the diffraction peak A to the diffraction peak B of the binder satisfied A(111)/B(022)=3.9.
Example 6
[0091] Example 6 was the same as Example 1 except that in <Preparation of binder>, the binder PVDF was replaced with the copolymer formed by 95% VDF and 5% hexafluoropropylene.
Example 7
[0092] Example 7 was the same as Example 1 except that in <Preparation of binder>, the binder PVDF was replaced with the copolymer formed by 85% VDF, 10% pentafluoropropylene, and 5% hexafluorobutadiene.
Example 8
[0093] Example 8 was the same as Example 1 except that in <Preparation of binder>, the binder PVDF was replaced with the copolymer formed by 90% VDF and 10% trifluoroethylene.
Example 9
[0094] Example 9 was the same as Example 1 except that in <Preparation of binder>, the binder PVDF was replaced with the copolymer formed by 85% VDF, 10% perfluorobutene, and 5% tetrafluoroethylene.
Example 10
[0095] Example 10 was the same as Example 1 except that in <Preparation of binder>, the reaction time was adjusted to 2 h, such that the binder had no diffraction peak C at 42.2.
Example 11
[0096] Example 11 was the same as Example 2 except that in <Preparation of binder>, the weight-average molecular weight of the binder was adjusted to 800000.
Example 12
[0097] Example 12 was the same as Example 2 except that in <Preparation of binder>, the weight-average molecular weight of the binder was adjusted to 950000.
Example 13
[0098] Example 13 was the same as Example 2 except that in <Preparation of binder>, the weight-average molecular weight of the binder was adjusted to 1100000.
Example 14
[0099] Example 14 was the same as Example 2 except that in <Preparation of binder>, the molecular weight distribution of the binder was adjusted to satisfy Mw/Mn=2.05.
Example 15
[0100] Example 15 was the same as Example 2 except that in <Preparation of binder>, the molecular weight distribution of the binder was adjusted to satisfy Mw/Mn=2.8.
Example 16
[0101] Example 16 was the same as Example 2 except that in <Preparation of binder>, the molecular weight distribution of the binder was adjusted to satisfy Mw/Mn=3.2.
Example 17
[0102] Example 17 was the same as Example 2 except that in <Preparation of binder>, the molecular weight distribution of the binder was adjusted to satisfy Mw/Mn=3.6.
Example 18
[0103] Example 18 was the same as Example 2 except that in <Preparation of positive electrode plate>, D.sub.v50 of the positive electrode active substance was adjusted to 0.5 m.
Example 19
[0104] Example 19 was the same as Example 2 except that in <Preparation of positive electrode plate>, D.sub.v50 of the positive electrode active substance was adjusted to 10 m.
Example 20
[0105] Example 20 was the same as Example 2 except that in <Preparation of positive electrode plate>, D.sub.v50 of the positive electrode active substance was adjusted to 20 m.
Example 21
[0106] Example 21 was the same as Example 2 except that in <Preparation of positive electrode plate>, D.sub.v50 of the positive electrode active substance was adjusted to 35 m.
Example 22
[0107] Example 22 was the same as Example 2 except that in <Preparation of positive electrode plate>, the single-sided thickness of the positive electrode mixture layer was adjusted to 40.5 m.
Example 23
[0108] Example 23 was the same as Example 2 except that in <Preparation of positive electrode plate>, the single-sided thickness of the positive electrode mixture layer was adjusted to 45 m.
Example 24
[0109] Example 24 was the same as Example 2 except that in <Preparation of positive electrode plate>, the single-sided thickness of the positive electrode mixture layer was adjusted to 50 m.
Example 25
[0110] Example 25 was the same as Example 2 except that in <Preparation of positive electrode plate>, the single-sided thickness of the positive electrode mixture layer was adjusted to 55 m.
Example 26
[0111] Example 26 was the same as Example 2 except that in <Preparation of positive electrode plate>, the thickness of the positive electrode current collector was adjusted to 7 m.
Example 27
[0112] Example 27 was the same as Example 2 except that in <Preparation of positive electrode plate>, the thickness of the positive electrode current collector was adjusted to 10 m.
Example 28
[0113] Example 28 was the same as Example 2 except that in <Preparation of positive electrode plate>, the thickness of the positive electrode current collector was adjusted to 20 m.
Example 29
[0114] Example 29 was the same as Example 2 except that in <Preparation of binder>, the weight-average molecular weight of the binder was adjusted to 1200000.
Example 30
[0115] Example 30 was the same as Example 2 except that in <Preparation of binder>, the weight-average molecular weight of the binder was adjusted to 700000.
Example 31
[0116] Example 31 was the same as Example 2 except that in <Preparation of binder>, the molecular weight distribution of the binder was adjusted to satisfy Mw/Mn=2.00.
Example 32
[0117] Example 32 was the same as Example 2 except that in <Preparation of binder>, the molecular weight distribution of the binder was adjusted to satisfy Mw/Mn=3.70.
Example 33
[0118] Example 33 was the same as Example 2 except that in <Preparation of positive electrode plate>, D.sub.v50 of the positive electrode active substance was adjusted to 0.2 m.
Example 34
[0119] Example 34 was the same as Example 2 except that in <Preparation of positive electrode plate>, D.sub.v50 of the positive electrode active substance was adjusted to 38 m.
Example 35
[0120] Example 35 was the same as Example 2 except that in <Preparation of positive electrode plate>, the single-sided thickness of the positive electrode mixture layer was adjusted to 40 m.
Example 36
[0121] Example 36 was the same as Example 2 except that in <Preparation of positive electrode plate>, the single-sided thickness of the positive electrode mixture layer was adjusted to 56 m.
Example 37
[0122] Example 37 was the same as Example 2 except that in <Preparation of positive electrode plate>, the thickness of the positive electrode current collector was adjusted to 6 m.
Example 38
[0123] Example 38 was the same as Example 2 except that in <Preparation of positive electrode plate>, the thickness of the positive electrode current collector was adjusted to 22 m.
Comparative Example 1
[0124] Comparative Example 1 was the same as Example 1 except that in <Preparation of binder>, the PVDF-HFP (Wu Yu, #W7500) polymer was used as the binder.
Comparative Example 2
[0125] Comparative Example 2 was the same as Example 1 except that in <Preparation of binder>, the polyimide (PI) was used as the binder.
Comparative Example 3
[0126] Comparative Example 3 was the same as Example 1 except that in <Preparation of binder>, the PVDFCOOH (Solvay S.A., 5130) polymer was used as the binder.
Comparative Example 4
[0127] Comparative Example 4 was the same as Example 1 except that in <Preparation of binder>, the reaction temperature was adjusted to 95 C. and the reaction time was adjusted to 2 h, such that the binder had no diffraction peak C at 42.2 and the area ratio of the diffraction peak A to the diffraction peak B satisfied A(111)/B(022)=5.05.
Comparative Example 5
[0128] Comparative Example 5 was the same as Example 1 except that in <Preparation of binder>, the reaction temperature was adjusted to 95 C., such that the area ratio of the diffraction peak A to the diffraction peak B of the binder satisfied A(111)/B(022)=5.05.
Comparative Example 6
[0129] Comparative Example 6 was the same as Example 1 except that in <Preparation of binder>, the reaction temperature was adjusted to 85 C., such that the area ratio of the diffraction peak A to the diffraction peak B of the binder satisfied A(111)/B(022)=0.55.
[0130] The preparation parameters and test results of the examples and comparative examples are shown in Table 1 and Table 2 below.
TABLE-US-00001 TABLE 1 Adhesion force between positive electrode mixture (111) (022) (131) layer diffraction diffraction diffraction and Ultimate Thickness Capacity Material peak peak peak current compacted swelling retention of A at B at A(111)/ C at collector density Brittle rate rate binder 26.2 38.5 B(022) 42.2 (N/m) (g/mm.sup.3) fracture (%) (%) Example 1 PVDF Found Found 1.0 Found 18.4 4.33 None 8.20 84.30 Example 2 PVDF Found Found 1.5 Found 18.6 4.34 None 7.80 86.30 Example 3 PVDF Found Found 2.4 Found 17.9 4.34 None 7.90 84.90 Example 4 PVDF Found Found 3.2 Found 18.4 4.32 None 8.60 83.90 Example 5 PVDF Found Found 3.9 Found 18.2 4.31 None 8.90 82.90 Example 6 Copolymer formed by Found Found 1.8 Found 17.8 4.23 None 9.80 80.90 95% VDF and 5% hexafluoropropylene Example 7 Copolymer formed by Found Found 2.2 Found 18.2 4.23 None 10.20 81.90 85% VDF, 10% pentafluoropropylene, and 5% hexafluorobutadiene Example 8 90% VDF and Found Found 1.8 Found 18.0 4.23 None 9.70 81.20 10% trifluoroethylene Example 9 Copolymer formed by Found Found 2.1 Found 18.3 4.23 None 10.10 81.50 85% VDF, 10% perfluorobutene, and 5% tetrafluoroethylene Example 10 PVDF Found Found 1.0 None 16.3 4.21 Slight 10.30 78.80 Comparative PVDF-HFP Found None None 14.2 4.21 Severe 15.80 72.80 Example 1 Comparative PI None None None 8.8 4.05 Severe 22.50 50.60 Example 2 Comparative PVDF-COOH None Found None 10.8 3.95 Severe 17.80 68.30 Example 3 Comparative PVDF Found Found 5.05 None 19.8 4.24 Severe 13.60 73.50 Example 4 Comparative PVDF Found Found 5.05 Found 17.3 4.29 Severe 12.80 72.60 Example 5 Comparative PVDF Found Found 0.55 Found 17.4 4.27 Slight 13.30 74.90 Example 6 In Table 1, means not detected.
TABLE-US-00002 TABLE 2 Single- sided Weight- D.sub.v50 thickness average of of (111) (022) molecular positive positive diffraction diffraction weight electrode electrode Material peak peak of active mixture of A at B at A(111)/ binder substance layer binder 26.2 38.5 B(022) (10.sup.4) Mw/Mn (m) (m) Example PVDF Found Found 1.5 80 2.18 15.6 46 11 Example PVDF Found Found 1.5 95 2.18 15.6 46 12 Example PVDF Found Found 1.5 110 2.18 15.6 46 13 Example PVDF Found Found 1.5 90 2.05 15.6 46 14 Example PVDF Found Found 1.5 90 2.8 15.6 46 15 Example PVDF Found Found 1.5 90 3.2 15.6 46 16 Example PVDF Found Found 1.5 90 3.6 15.6 46 17 Example PVDF Found Found 1.5 90 2.18 0.5 46 18 Example PVDF Found Found 1.5 90 2.18 10 46 19 Example PVDF Found Found 1.5 90 2.18 20 46 20 Example PVDF Found Found 1.5 90 2.18 35 46 21 Example PVDF Found Found 1.5 90 2.18 15.6 40.5 22 Example PVDF Found Found 1.5 90 2.18 15.6 45 23 Example PVDF Found Found 1.5 90 2.18 15.6 50 24 Example PVDF Found Found 1.5 90 2.18 15.6 55 25 Example PVDF Found Found 1.5 90 2.18 15.6 46 26 Example PVDF Found Found 1.5 90 2.18 15.6 46 27 Example PVDF Found Found 1.5 90 2.18 15.6 46 28 Example PVDF Found Found 1.5 120 2.18 15.6 46 29 Example PVDF Found Found 1.5 70 2.18 15.6 46 30 Example PVDF Found Found 1.5 90 2.00 15.6 46 31 Example PVDF Found Found 1.5 90 3.70 15.6 46 32 Example PVDF Found Found 1.5 90 2.18 0.2 46 33 Example PVDF Found Found 1.5 90 2.18 38 46 34 Example PVDF Found Found 1.5 90 2.18 15.6 40 35 Example PVDF Found Found 1.5 90 2.18 15.6 56 36 Example PVDF Found Found 1.5 90 2.18 15.6 46 37 Example PVDF Found Found 1.5 90 2.18 15.6 46 38 Adhesion force between Thickness positive of electrode positive mixture electrode Ultimate layer and Thickness Capacity current compacted current swelling retention collector density collector Brittle rate rate (m) (g/mm.sup.3) (N/m) fracture (%) (%) Example 9 4.33 17.3 None 8.30 85.20 11 Example 9 4.34 18.6 None 7.80 86.30 12 Example 9 4.34 18.9 None 7.90 85.30 13 Example 9 4.32 18.5 None 8.30 83.30 14 Example 9 4.33 17.4 None 8.00 82.30 15 Example 9 4.32 16.5 None 8.20 82.1 16 Example 9 4.34 15.8 None 8.50 81.60 17 Example 9 3.9 11.3 None 9.50 80.30 18 Example 9 4.15 13.4 None 9.20 81.90 19 Example 9 4.22 15.7 None 10.30 82.50 20 Example 9 4.13 16.5 None 12.50 79.70 21 Example 9 4.28 13.5 None 8.50 81.30 22 Example 9 4.31 18.2 None 8.30 85.50 23 Example 9 4.26 17.6 None 9.60 85.30 24 Example 9 4.23 16.8 None 9.90 83.20 25 Example 7 4.25 15.8 None 8.20 84.30 26 Example 10 4.35 17.9 None 8.30 82.90 27 Example 20 4.31 16.5 None 8.10 83.70 28 Example 9 4.29 19.3 None 9.70 80.80 29 Example 9 4.32 16.2 None 8.80 84.30 30 Example 9 4.15 15.5 None 9.80 77.80 31 Example 9 4.16 15.3 None 11.30 78.50 32 Example 9 3.85 10.3 Slight 10.40 78.30 33 Example 9 4.05 10.3 Slight 15.60 78.80 34 Example 9 4.21 12.3 None 8.80 81.80 35 Example 9 4.18 11.9 None 10.90 79.50 36 Example 6 4.05 13.2 Slight 8.80 79.90 37 Example 22 4.25 16.2 None 8.30 80.30 38
[0131] It can be learned from Examples 1 to 10 and Comparative Examples 1 to 6 that when the binder has the (111) diffraction peak A at 26.2 and the (022) diffraction peak B at 38.5 and A(111)/B(022) is within the range of this application, the positive electrode plate of this application has a high ultimate compacted density, alleviating the brittle fracture of the positive electrode plate, and improving the anti-swelling performance and cycling performance of the lithium-ion battery.
[0132] It can be learned from Example 1 and Example 10 that when the binder has the (131) diffraction peak C at 42.2, the ultimate compacted density of the positive electrode plate can be further increased, and the anti-swelling performance and cycling performance of the lithium-ion battery can be further improved.
[0133] It can be learned from Examples 11 to 13 and Examples 29 and 30 that the weight-average molecular weight of the binder being controlled within the range of this application can further increase the ultimate compacted density of the positive electrode plate and improve the anti-swelling performance and cycling performance of the lithium-ion battery.
[0134] It can be learned from Examples 14 to 17 and Examples 31 and 32 that the molecular weight distribution Mw/Mn of the binder being controlled within the range of this application can further increase the ultimate compacted density of the positive electrode plate, enhance the adhesion between the positive electrode mixture layer and the current collector, and improve the anti-swelling performance and cycling performance of the lithium-ion battery.
[0135] It can be learned from Examples 18 to 21 and Examples 33 and 34 that D.sub.v50 of the positive electrode active substance being controlled within the range of this application can further increase the ultimate compacted density of the positive electrode plate, alleviate the brittle fracture of the positive electrode plate, enhance the adhesion between the positive electrode mixture layer and the current collector, and improve the anti-swelling performance and cycling performance of the lithium-ion battery.
[0136] It can be learned from Examples 22 to 25 and Examples 35 and 36 that the single-sided thickness of the positive electrode mixture layer being controlled within the range of this application can further increase the ultimate compacted density of the positive electrode plate, enhance the adhesion between the positive electrode mixture layer and the current collector, and improve the cycling performance of the lithium-ion battery.
[0137] It can be learned from Examples 26 to 28 and Examples 37 and 38 that the thickness of the positive electrode current collector being controlled within the range of this application can further increase the ultimate compacted density of the positive electrode plate, alleviate the brittle fracture of the positive electrode plate, and improve the anti-swelling performance and cycling performance of the lithium-ion battery.
[0138] The foregoing descriptions are merely preferred embodiments of this application, and are not intended to limit this application. Any modifications, equivalent replacements, improvements, and the like made without departing from the spirit and principle of this application shall fall within the protection scope of this application.