CN107403905B - Lithium ion battery positive plate and preparation method thereof - Google Patents
Lithium ion battery positive plate and preparation method thereof Download PDFInfo
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- CN107403905B CN107403905B CN201610331430.0A CN201610331430A CN107403905B CN 107403905 B CN107403905 B CN 107403905B CN 201610331430 A CN201610331430 A CN 201610331430A CN 107403905 B CN107403905 B CN 107403905B
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- 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
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
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- 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
- H01M4/04—Processes of manufacture in general
- H01M4/0402—Methods of deposition of the material
- H01M4/0404—Methods of deposition of the material by coating on electrode collectors
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- 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
- H01M4/04—Processes of manufacture in general
- H01M4/043—Processes of manufacture in general involving compressing or compaction
- H01M4/0433—Molding
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- 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
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
- H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2220/00—Batteries for particular applications
- H01M2220/30—Batteries in portable systems, e.g. mobile phone, laptop
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- 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 discloses a preparation method of a lithium ion battery positive plate, which comprises the following steps: providing a positive current collector; preparing positive electrode slurry containing a positive electrode active material with a crystal form of a laminated structure, uniformly distributing the positive electrode slurry on a positive electrode current collector, drying, and then carrying out primary cold pressing and slicing to obtain a positive plate; carrying out infiltration treatment on the positive plate by using a solvent; and drying and cold pressing for the second time to obtain the lithium ion battery positive plate. The method adopts the solvent to perform infiltration treatment on the positive plate subjected to primary cold pressing, so that the residual stress of the positive plate can be effectively reduced, the expansion of the positive plate is reduced, the thickness of the lithium ion battery is reduced, and the energy density of the lithium ion battery is improved. In the subsequent charge-discharge cycle process, the contact among the positive active material particles is tighter, and the cycle performance of the lithium ion battery is obviously improved. In addition, the invention also discloses the lithium ion battery positive plate prepared by the preparation method and the lithium ion battery adopting the lithium ion battery positive plate.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a lithium ion battery positive plate and a preparation method thereof.
Background
In recent years, with the popularization and lightening of electronic devices such as smart phones, tablet computers, wearable devices and the like, the demand for energy density of consumer lithium ion batteries is also increasing.
The energy density of the lithium ion battery is calculated according to the following formula: initial volumetric energy density is the first discharge energy of the cell (cell capacity x discharge plateau)/(cell length x width x thickness). From the above calculation formula, it can be known that the thickness of the lithium ion battery affects the energy density of the lithium ion battery under the same material system (the battery capacity is consistent with the discharge plateau) and the length and width dimensions of the battery.
The thickness of the lithium ion battery is determined by the thicknesses of the positive and negative electrode active materials and auxiliary materials such as current collectors and separators. Since the thickness of the auxiliary material does not change, the increase in thickness comes from the expansion of the positive and negative electrode sheets. Taking a lithium ion battery with commercial lithium cobaltate and graphite as positive and negative electrode active materials respectively as an example, the thickness of the lithium ion battery increases by about 7% from cold pressing to capacity separation, wherein 5% is caused by the expansion of the graphite negative electrode and 2% is caused by the expansion of the lithium cobaltate positive electrode.
Therefore, the effect of reducing the thickness expansion of the positive plate from cold pressing to capacity grading on the improvement of the initial volume energy density of the lithium ion battery is remarkable. In addition, through hundreds of charge-discharge cycle processes, with the continuous lithium insertion/removal of the positive electrode active material and the release of cold pressing residual stress, the thickness expansion of the lithium ion battery is about 10%, wherein about 7% is caused by the expansion of the graphite negative electrode, about 3% is caused by the expansion of the lithium cobaltate positive electrode, and the increase of the thickness of the lithium ion battery tends to reduce the volume energy density of the lithium ion battery in the using process.
The swelling of the positive electrode sheet also causes deterioration of contact between positive active material particles, deterioration of conductivity, and increase of impedance, thereby further deteriorating electrochemical performance of the lithium ion battery.
Before cold pressing of the positive plate, the positive active material particles, the binder and the conductive agent are in a fluffy state, for example, the initial bulk density of the coated lithium cobaltate positive electrode is 2-2.5 g/cc. In the cold pressing process, the positive active material, the binder and the conductive agent are rapidly and violently compressed, the stacking density of the positive electrode is instantly improved to 3.8-4.2 g/cc, and the thickness is compressed to 40% -70% of the initial thickness. In this process, repulsive forces tend to be generated between the positive active material particles that interact to restore the pole piece to the pre-stressed state. However, due to the mutual adhesive force, the repulsive force between some positive electrode active material particles is cancelled, so that the positive electrode active material particles cannot be completely expanded, i.e., the stress cannot be completely released, which is called residual stress. In the subsequent processes of processing and charging and discharging, residual stress is released continuously, so that the positive plate expands rapidly and the thickness of the battery cell is increased, and energy density loss and cycle performance are deteriorated.
The existing method for reducing the residual stress of the positive plate mainly comprises high-temperature heat treatment or long-time standing, but both methods cannot effectively reduce the residual stress and are long in time consumption and low in efficiency.
In view of this, it is necessary to provide a positive plate of a lithium ion battery and a method for preparing the same.
Disclosure of Invention
The invention aims to: the defects of the prior art are overcome, and the lithium ion battery positive plate and the preparation method thereof are provided, so that the cold pressing residual stress of the positive plate can be reduced, and the expansion of the positive plate in the preparation process and the expansion of the positive plate in the charging and discharging process can be reduced.
In order to achieve the above object, the present invention provides a method for preparing a positive plate of a lithium ion battery, comprising the following steps:
providing a positive current collector;
preparing positive electrode slurry containing a positive electrode active material with a crystal form of a laminated structure, uniformly distributing the positive electrode slurry on a positive electrode current collector, drying, and then carrying out primary cold pressing and slicing to obtain a positive plate;
carrying out infiltration treatment on the positive plate by using a solvent; and
and drying and cold pressing for the second time to obtain the lithium ion battery positive plate.
As an improvement of the preparation method of the lithium ion battery positive plate, the solvent is one or more of ethyl acetate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, propylene carbonate, fluoroethylene carbonate, n-heptane, n-hexane, carbon disulfide, dichloromethane, benzene, xylene, dimethyl sulfoxide, diethyl ether and nitrogen-methyl pyrrolidone.
As an improvement of the preparation method of the lithium ion battery positive plate, the method for carrying out infiltration treatment on the positive plate by using the solvent comprises rotary spraying and transfer coating.
As an improvement of the preparation method of the lithium ion battery positive plate, the solvent amount adopted in the infiltration treatment is 1-20% of the mass of the positive active material. The solvent amount is too small to infiltrate into the positive plate, and the stress release is insufficient; the solvent amount is too much, the cohesive force is seriously damaged, and even the adhesion of the positive electrode film and the current collector is influenced, so that the positive electrode film is easy to be stripped.
As an improvement of the preparation method of the lithium ion battery positive plate, the solvent amount adopted in the infiltration treatment is 5-15% of the mass of the positive active material.
As an improvement of the preparation method of the lithium ion battery positive plate, the positive active material is one or more of lithium cobaltate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, lithium manganese oxide and lithium nickelate.
As an improvement of the preparation method of the lithium ion battery positive plate, the XRD peak intensity ratio 003/110 of the anode active material after the infiltration treatment is reduced by 5-50% compared with the XRD peak intensity ratio 003/110 of the anode active material without the infiltration treatment.
As an improvement of the preparation method of the lithium ion battery positive plate, the XRD peak intensity ratio of the infiltrated positive active material is 003/110, which is reduced by 10-40% compared with the XRD peak intensity ratio of the non-infiltrated positive active material, which is 003/110.
In order to achieve the purpose, the invention also provides a lithium ion battery positive plate, and the lithium ion battery positive plate is prepared according to the preparation method of the lithium ion battery positive plate.
In addition, the invention also provides a lithium ion battery, which comprises a positive plate, a negative plate, an isolating membrane arranged between the positive plate and the negative plate, and electrolyte, wherein the positive plate is the lithium ion battery positive plate.
Compared with the prior art, the invention has the following technical effects:
according to the invention, the solvent is adopted to perform infiltration treatment on the positive plate subjected to primary cold pressing, so that the bonding force among particles of the positive active material is reduced, the thickness of the positive plate expands (10%) under the action of residual stress, and then the residual stress is released. In the process, although the stacking density is slightly reduced, the stacking density of the positive plate after the solvent soaking treatment is far larger than that of the positive plate after coating and natural stacking, and after the positive plate is subjected to secondary cold pressing to the required stacking density, the accumulated internal stress of the positive plate is far smaller than that accumulated in the primary cold pressing. Therefore, in the preparation process of the lithium ion battery, the expansion of the positive plate from cold pressing to capacity grading is reduced, the thickness of the lithium ion battery is reduced, and the energy density of the lithium ion battery is improved.
In the subsequent charge-discharge cycle process, because the expansion of the positive plate is reduced, the contact between positive active material particles is tighter, the polarization caused by poor contact is reduced, and the cycle performance of the lithium ion battery is improved.
Drawings
The lithium ion battery positive plate and the preparation method thereof of the present invention are described in detail below with reference to the accompanying drawings and examples, wherein:
fig. 1 is a schematic view showing the distribution of positive electrode active material particles in the positive electrode sheet before and after cold pressing.
Fig. 2 is a distribution diagram of the maximum peak position of the raman spectrum before and after the solvent infiltration treatment of the positive electrode sheets of comparative example 1 and example 4, and the internal stress of the positive electrode sheets is characterized.
Fig. 3 shows the XRD characterization 003/110 peak intensity ratio before and after the solvent infiltration treatment of the positive electrode sheets of comparative example 1 and example 4.
Examples
In order to make the objects, technical solutions and technical effects of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the examples given in this specification are for the purpose of illustration only and are not intended to limit the invention.
Example 1
1. Preparation of lithium ion battery positive plate
LiCoO as positive electrode active material2The conductive agent, conductive carbon SP and binder PVDF are mixed according to the mass ratio of 95: 2: 3 evenly mixing the mixture in N-methyl pyrrolidone serving as a solvent to prepare anode slurry, evenly coating the anode slurry on an anode current collector aluminum foil, drying the anode slurry, and carrying out cold pressing once until the stacking density is reached4.1g/cc, and slicing to obtain the positive plate.
And (3) performing infiltration treatment by using ethyl acetate as a solvent, uniformly spraying ethyl acetate which is 1% of the mass of the positive active material on the surface of the positive plate prepared in the step by adopting a rotary spraying mode, and then drying and carrying out secondary cold pressing to obtain the lithium ion battery positive plate with the required bulk density.
Fig. 1 is a schematic diagram of the distribution of positive active material particles in positive plates before and after cold pressing: prior to cold pressing, the pellets are relatively loosely packed. After cold pressing, the particles are severely compressed under the action of cold pressing pressure, and after the pressure is removed, repulsive force of interaction exists among the particles, and the particles cannot be restored to the initial state under the action of the adhesive force.
2. Preparation of lithium ion battery negative plate
Mixing graphite serving as a negative electrode active material, SBR serving as a binder, CMC serving as a thickening agent and SP serving as a conductive agent in a mass ratio of 96: 1.5: 1.5: 1, uniformly mixing the mixture in solvent water to prepare negative electrode slurry, uniformly coating the negative electrode slurry on a negative current collector copper foil, drying, cold-pressing to a bulk density of 1.7g/cc, and slicing to prepare the lithium ion battery negative plate.
3. Preparation of lithium ion battery electrolyte
Mixing Ethylene Carbonate (EC), Propylene Carbonate (PC), ethyl methyl carbonate (DEC) and fluoroethylene carbonate (FEC) according to a mass ratio of 25: 25: 45: 5 mixing well with lithium hexafluorophosphate (LiPF)6) As a solute, a lithium ion battery electrolyte, LiPF, was prepared6The concentration of (2) is 1.1 mol/L.
4. Preparation of lithium ion battery
Winding and packaging the prepared lithium ion battery positive plate, the lithium ion battery negative plate and the Polyethylene (PE) isolating membrane to prepare a lithium ion battery cell with the thickness of 4mm, the width of 35mm and the length of 80 mm; vacuum baking at 75 deg.C for 12h, injecting lithium ion battery electrolyte and standing for 24 h; charging to 4.35V at 35 ℃ by using a constant current of 0.1C, then charging to a current reduced to 0.05C by using a constant voltage of 4.35V, then discharging to 3.0V by using a constant current of 0.5C, repeating the charging and discharging for 2 times, and finally charging the lithium ion battery to 3.85V by using a constant current of 0.5C to complete capacity division to obtain the lithium ion battery of the embodiment 1 of the invention.
Example 2
The lithium ion battery in embodiment 2 of the present invention is basically the same as the lithium ion battery in embodiment 1 of the present invention, except that: and during the soaking treatment, uniformly spraying ethyl acetate which accounts for 5 percent of the mass of the positive active material on the surface of the positive plate prepared in the step by a rotary spraying mode.
Example 3
The lithium ion battery in embodiment 3 of the present invention is basically the same as the lithium ion battery in embodiment 1 of the present invention, except that: and during the soaking treatment, uniformly spraying ethyl acetate which is 10 percent of the mass of the positive active material on the surface of the positive plate prepared in the step by a rotary spraying mode.
Example 4
The lithium ion battery in embodiment 4 of the present invention is basically the same as the lithium ion battery in embodiment 1 of the present invention, except that: and during the soaking treatment, uniformly spraying ethyl acetate which accounts for 15 percent of the mass of the positive active material on the surface of the positive plate prepared in the step by a rotary spraying mode.
Example 5
The lithium ion battery in embodiment 5 of the present invention is basically the same as the lithium ion battery in embodiment 1 of the present invention, except that: and during the soaking treatment, uniformly spraying ethyl acetate which accounts for 20 percent of the mass of the positive active material on the surface of the positive plate prepared in the step by a rotary spraying mode.
Example 6
The lithium ion battery in embodiment 6 of the present invention is basically the same as the lithium ion battery in embodiment 1 of the present invention, except that: during the infiltration treatment, the selected solvent is dimethyl carbonate, and the dimethyl carbonate which is 10 percent of the mass of the positive active material is uniformly sprayed on the surface of the positive plate prepared in the previous step in a rotary spraying mode.
Example 7
The lithium ion battery in embodiment 7 of the present invention is basically the same as the lithium ion battery in embodiment 1 of the present invention, except that: and during the infiltration treatment, the selected solvent is normal hexane, and the normal hexane which is 10 percent of the mass of the positive electrode active material is uniformly sprayed on the surface of the positive electrode sheet prepared in the previous step in a rotary spraying mode.
Example 8
The lithium ion battery in embodiment 8 of the present invention is basically the same as the lithium ion battery in embodiment 1 of the present invention, except that: during the soaking treatment, the selected solvent is dichloromethane, and dichloromethane which is 10% of the mass of the positive electrode active material is uniformly sprayed on the surface of the positive electrode plate prepared in the previous step in a rotary spraying mode.
Example 9
The lithium ion battery in embodiment 9 of the present invention is basically the same as the lithium ion battery in embodiment 1 of the present invention, except that: during the infiltration treatment, the selected solvent is benzene, and benzene which is 10% of the mass of the positive active material is uniformly sprayed on the surface of the positive plate prepared in the previous step in a rotary spraying mode.
Example 10
The lithium ion battery in embodiment 10 of the present invention is basically the same as the lithium ion battery in embodiment 1 of the present invention, except that: during the infiltration treatment, the selected solvent is dimethyl sulfoxide, and the dimethyl sulfoxide which is 10% of the mass of the positive active material is uniformly sprayed on the surface of the positive plate prepared in the previous step in a rotary spraying mode.
Example 11
The lithium ion battery in embodiment 11 of the present invention is basically the same as the lithium ion battery in embodiment 1 of the present invention, except that: during the soaking treatment, the selected solvent is diethyl ether, and diethyl ether which is 10% of the mass of the positive electrode active material is uniformly transferred to the surface of the positive electrode plate prepared in the previous step in a transfer coating mode.
Example 12
The lithium ion battery in embodiment 12 of the present invention is basically the same as the lithium ion battery in embodiment 1 of the present invention, except that: during the soaking treatment, the selected solvent is nitrogen-methyl pyrrolidone, and the nitrogen-methyl pyrrolidone which is 10 percent of the mass of the positive active material is uniformly transferred to the surface of the positive plate prepared in the previous step in a transfer coating mode.
Example 13
The lithium ion battery in embodiment 13 of the present invention is basically the same as the lithium ion battery in embodiment 1 of the present invention, except that: the positive active material is nickel cobalt lithium manganate, the stacking density is 3.5g/cc through one-step cold pressing, during the infiltration treatment, ethyl acetate is selected as a solvent, and ethyl acetate which is 10% of the mass of the positive active material is uniformly sprayed on the surface of the positive plate prepared in the previous step in a rotary spraying mode.
Example 14
The lithium ion battery in embodiment 14 of the present invention is basically the same as the lithium ion battery in embodiment 1 of the present invention, except that: the positive active material is nickel cobalt lithium aluminate, the stacking density is 3.5g/cc through one-time cold pressing, during the infiltration treatment, ethyl acetate is selected as a solvent, and the ethyl acetate which is 10% of the mass of the positive active material is uniformly sprayed on the surface of the positive plate prepared in the previous step in a rotary spraying mode.
Example 15
The lithium ion battery in embodiment 15 of the present invention is basically the same as the lithium ion battery in embodiment 1 of the present invention, except that: the positive electrode active material is lithium nickelate, the stacking density is 3.5g/cc through one-time cold pressing, during the infiltration treatment, ethyl acetate is selected as a solvent, and ethyl acetate which is 10% of the mass of the positive electrode active material is uniformly sprayed on the surface of the positive electrode sheet prepared in the previous step in a rotary spraying mode.
Example 16
The lithium ion battery in embodiment 16 of the present invention is basically the same as the lithium ion battery in embodiment 1 of the present invention, except that: the positive active material is lithium manganate, the bulk density is 3.5g/cc through one-time cold pressing, during the infiltration treatment, ethyl acetate is selected as a solvent, and ethyl acetate which is 10% of the mass of the positive active material is uniformly sprayed on the surface of the positive plate prepared in the previous step in a rotary spraying mode.
Comparative example 1
The lithium ion battery of comparative example 1 is substantially the same as the lithium ion battery of example 1 of the present invention, except that: and (3) the anode plate is not subjected to infiltration treatment, the anode slurry is uniformly coated on an anode current collector aluminum foil, and after drying and cold pressing to the stacking density of 4.1g/cc, the lithium ion battery anode plate is directly prepared by slicing.
Comparative example 2
Comparative example 2 a lithium ion battery was substantially the same as the lithium ion battery of example 1 of the present invention, except that: and during the soaking treatment, ethyl acetate which is 0.5 percent of the mass of the positive active material is uniformly sprayed on the surface of the positive plate prepared in the previous step in a rotary spraying mode.
Comparative example 3
Comparative example 3 a lithium ion battery is substantially the same as the lithium ion battery of example 1 of the present invention, except that: and during the soaking treatment, uniformly spraying ethyl acetate which accounts for 25 percent of the mass of the positive active material on the surface of the positive plate prepared in the step by a rotary spraying mode.
Comparative example 4
The lithium ion battery of comparative example 4 is substantially the same as the lithium ion battery of example 13 of the present invention, except that: and (3) the anode plate is not subjected to infiltration treatment, the anode slurry is uniformly coated on an anode current collector aluminum foil, and after drying and cold pressing to the stacking density of 3.5g/cc, the lithium ion battery anode plate is directly prepared by slicing.
Comparative example 5
The lithium ion battery of comparative example 5 is substantially the same as the lithium ion battery of example 14 of the present invention, except that: and (3) the anode plate is not subjected to infiltration treatment, the anode slurry is uniformly coated on an anode current collector aluminum foil, and after drying and cold pressing to the stacking density of 3.5g/cc, the lithium ion battery anode plate is directly prepared by slicing.
Comparative example 6
The lithium ion battery of comparative example 6 is substantially the same as the lithium ion battery of example 15 of the present invention, except that: and (3) the anode plate is not subjected to infiltration treatment, the anode slurry is uniformly coated on an anode current collector aluminum foil, and after drying and cold pressing to the stacking density of 3.5g/cc, the lithium ion battery anode plate is directly prepared by slicing.
Comparative example 7
The lithium ion battery of comparative example 7 is substantially the same as the lithium ion battery of example 16 of the present invention, except that: and (3) the anode plate is not subjected to infiltration treatment, the anode slurry is uniformly coated on an anode current collector aluminum foil, and after drying and cold pressing to the stacking density of 3.5g/cc, the lithium ion battery anode plate is directly prepared by slicing.
Lithium ion battery performance testing
Positive plate performance test
The positive plate XRD tests the particle alignment orientation: XRD tests of the layered positive electrode sheet, in which the intensity ratio of the 003 peak (C003) and the 110 peak (C110) reflects the stacking orientation of the particles in the positive electrode sheet, and the larger the ratio, the stronger the orientation. The positive electrode active material is preferentially oriented in the 003 direction by the cold pressing pressure. After the solvent infiltration treatment, the positive plate expands due to the release of internal stress, so that the arrangement of positive active material particles is readjusted, the orientation is weakened, and although the secondary cold pressing is carried out, the orientation is still not as good as that of an untreated state.
Internal stress test of positive plate
The raman spectrum has the advantages of no loss and high resolution when measuring residual stress, and energy exchange occurs between photons through change of polarizability generated when the raman spectrum vibrates or rotates with substance molecules. When there is residual stress in the object, the band sensitive to stress shifts: if the pressure stress is applied, the bond length of the molecule is shortened, and the force constant is increased according to the relation between the force constant and the bond length, so that the photon vibration frequency is improved, and the peak moves to the direction of high wave number; when a tensile stress is applied, the vibration frequency becomes low and the peak shifts in the low wave number direction. In the cold-pressed positive electrode sheet, most of the residual stress is compressive stress, and therefore the magnitude of the residual stress can be judged through the wave number change of the Raman spectrum.
Fig. 2 is the peak position information of the maximum peak of the raman spectrum of the positive electrode sheet before and after the lithium ion battery of the embodiment of the present invention is subjected to the infiltration treatment with ethyl acetate, from which it can be seen that: after treatment with ethyl acetate, the raman spectrum peak shifts to the low wavenumber direction (relative to the non-wetted anode), indicating a decrease in residual stress in the anode; after the secondary cold pressing, the positive electrode sheet slightly moved in the high wave number direction, but the negative shift was still significant as compared with the positive electrode sheet which had not been subjected to the wet treatment, indicating that the residual stress accumulated in the positive electrode sheet was reduced.
Fig. 3 shows the XRD characteristic 003/110 peak intensity ratio before and after the solvent infiltration treatment of the positive electrode sheets in comparative example 1 and example 4, and it can be seen from fig. 3 that the XRD peak intensity ratio 003/110 of the positive electrode active material after the infiltration treatment is reduced by 5 to 50%, preferably 10 to 40%, compared with the XRD peak intensity ratio 003/110 of the positive electrode active material without the infiltration treatment.
Lithium ion battery performance testing
Initial volumetric energy density test of battery
The thickness of the lithium ion battery at 3.85V is tested by an altimeter, then the lithium ion battery is charged to 4.35V at a constant current of 0.5C at 25 ℃, further charged to a current of 0.05C at a constant voltage of 4.35V, and then discharged to 3.0V at a constant current of 0.5C, and the energy data of the discharging process is recorded by an instrument.
The lithium ion battery initial energy density calculation formula is as follows:
initial energy density (Wh/L) [ initial discharge energy (Wh)/cell length (mm)/initial cell thickness (mm)/cell width (mm) × 1000000], in which the cell lengths are all 80mm and the widths are all 35 mm.
Expansion rate of positive plate after capacity grading
The expansion rate of the positive plate after capacity grading is calculated according to the following formula:
and (3) the expansion rate (%) of the positive plate after capacity separation is 100% (the thickness of the positive plate after capacity separation-the thickness of the positive current collector)/(the thickness of the positive plate after cold pressing-the thickness of the positive current collector) -1], wherein the thickness of the positive plate is measured by a spiral micrometer.
Test of Battery Capacity conservation Rate
At 25 ℃, the lithium ion battery is charged to 4.35V at a constant current of 0.5C, then further charged to a constant voltage of 4.35V until the current is 0.05C, and then discharged to 3.0V at a constant current of 0.5C, wherein the discharge capacity at this time is the first discharge capacity of the lithium ion battery. The discharge capacity per cycle was recorded during the cycle in the above charge-discharge manner.
The capacity retention of the lithium ion battery is calculated according to the following formula:
the N-cycle capacity retention ratio (%) [ nth-cycle discharge capacity/first discharge capacity ] × 100%.
Post cycle battery expansion ratio
The post-cycle cell expansion rate was calculated according to the following formula: and (3) the post-cycle battery expansion rate (%) (post-cycle battery thickness-post-capacity-grading battery thickness)/post-capacity-grading battery thickness ]. 100%, wherein the battery thickness is measured by a height gauge, and the battery expansion rate level represents the expansion rate level of the positive and negative electrode plates forming the battery.
Referring to Table 1, Table 1 shows the parameters and performance test results of examples 1-16 and comparative examples 1-6.
TABLE 1 parameters and Performance test results for examples 1-16 and comparative examples 1-7
As can be seen from examples 1 to 5, 13 to 16 and comparative example 1, after the positive electrode was subjected to the impregnation treatment with ethyl acetate as a solvent, the expansion rate of the positive electrode from cold pressing to capacity separation was reduced due to the reduction of accumulated internal stress, so that the thickness of the battery was reduced and the initial energy density was improved. In addition, the swelling of the battery during the cycle is also reduced, and the cycle performance is improved. Among them, ethyl acetate reduces the binding force between particles of the positive electrode active material. In examples 6 to 12, dimethyl carbonate, n-hexane, dichloromethane, benzene, dimethyl sulfoxide, diethyl ether, and N-methylpyrrolidone acted similarly, and both the cyclic spray coating method and the transfer coating method achieved the effect, and the final effect was to reduce the large residual stress accumulated during cold pressing.
As can be seen from examples 1 to 5 and comparative examples 1 to 3, when the ethyl acetate treatment amount is less than 15%, the improvement effect becomes remarkable as the amount thereof increases, because a certain amount of solvent is required to infiltrate into the inside of the positive electrode sheet; when the treatment amount is less than 1%, the solvent can only infiltrate into the surface layer of the positive plate and cannot play a role. When the ethyl acetate treatment capacity is larger than 15%, the use amount is continuously increased, the effect is not increased any more, and even the effect is deteriorated when the use amount exceeds 20%, because the adhesive force among positive active material particles is greatly damaged when the ethyl acetate treatment capacity is excessive, and when the isopropanol infiltrates into the innermost layer, the adhesive force between a positive membrane and an aluminum foil substrate is even damaged, so that the positive membrane is stripped, and the performance of the battery is finally influenced.
As can be seen from table 1, the solvent infiltration treatments obtained in examples 13 to 16 and comparative examples 4 to 7 have similar effects on other positive active materials, and are not described again here.
In combination with the above description of the embodiments of the present invention, it can be seen that, compared with the prior art, the present invention has the following technical effects:
according to the invention, a certain solvent is adopted to perform infiltration treatment on the positive plate subjected to primary cold pressing, the solvent enables the bonding force between positive active material particles to be reduced, the positive plate undergoes thickness expansion under the action of residual stress, and then the residual stress is released. In the process, although slight thickness expansion and reduction of bulk density are accompanied, the bulk density of the positive plate after the solvent soaking treatment is far higher than that of the positive plate after coating and natural stacking, and after the positive plate is subjected to secondary cold pressing to reach the required bulk density, the accumulated internal stress of the positive plate is far smaller than that accumulated in primary cold pressing. Therefore, in the preparation process of the lithium ion battery, the expansion of the positive plate from cold pressing to capacity grading is reduced, the thickness of the lithium ion battery is reduced, and the energy density of the lithium ion battery is improved.
In the subsequent charge-discharge cycle process, because the expansion of the positive plate is reduced, the contact between positive active material particles is tighter, the polarization caused by poor contact is reduced, and the cycle performance of the lithium ion battery is improved.
The present invention can be modified and adapted appropriately from the above-described embodiments, according to the principles described above. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and variations of the present invention should fall within the scope of the claims of the present invention. Furthermore, although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
Claims (9)
1. A preparation method of a lithium ion battery positive plate is characterized by comprising the following steps:
providing a positive current collector;
preparing positive electrode slurry containing a positive electrode active material with a crystal form of a laminated structure, uniformly distributing the positive electrode slurry on a positive electrode current collector, drying, and then carrying out primary cold pressing and slicing to obtain a positive plate;
carrying out infiltration treatment on the positive plate by using a solvent, wherein the solvent adopted in the infiltration treatment is one or more of ethyl acetate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, propylene carbonate, fluoroethylene carbonate, n-heptane, n-hexane, carbon disulfide, dichloromethane, benzene, xylene, dimethyl sulfoxide, diethyl ether and nitrogen-methyl pyrrolidone; and
and drying and cold pressing for the second time to obtain the lithium ion battery positive plate.
2. The method for preparing the positive plate of the lithium ion battery according to claim 1, wherein the method for performing the infiltration treatment on the positive plate by using the solvent comprises spin coating and transfer coating.
3. The method for preparing the positive plate of the lithium ion battery according to claim 1, wherein the amount of the solvent used in the infiltration treatment is 1-20% of the mass of the positive active material.
4. The method for preparing the positive plate of the lithium ion battery according to claim 1, wherein the amount of the solvent used in the infiltration treatment is 5-15% of the mass of the positive active material.
5. The method for preparing the positive plate of the lithium ion battery according to claim 1, wherein the method comprises the following steps: the positive active material is one or more of lithium cobaltate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, lithium manganese oxide and lithium nickelate.
6. The method for preparing the positive plate of the lithium ion battery according to claim 1, wherein the method comprises the following steps: the XRD peak intensity ratio 003/110 of the cathode active material after the infiltration treatment is reduced by 5-50% compared with the XRD peak intensity ratio 003/110 of the cathode active material without the infiltration treatment.
7. The method for preparing the positive plate of the lithium ion battery according to claim 1, wherein the XRD peak intensity ratio 003/110 of the cathode active material after the infiltration treatment is reduced by 10-40% compared with the XRD peak intensity ratio 003/110 of the cathode active material without the infiltration treatment.
8. The utility model provides a lithium ion battery positive plate which characterized in that: the lithium ion battery positive plate is prepared by the preparation method of the lithium ion battery positive plate according to any one of claims 1 to 7.
9. A lithium ion battery comprising: the lithium ion battery comprises a positive plate, a negative plate, a separation film and electrolyte, wherein the separation film is arranged between the positive plate and the negative plate, and the positive plate is the positive plate of the lithium ion battery in claim 8.
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Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109950474B (en) * | 2018-06-29 | 2020-04-24 | 宁德时代新能源科技股份有限公司 | Lithium ion battery |
| CN108878892B (en) * | 2018-06-29 | 2019-04-30 | 宁德时代新能源科技股份有限公司 | Positive pole piece and battery |
| CN108808072A (en) * | 2018-06-29 | 2018-11-13 | 宁德时代新能源科技股份有限公司 | Lithium ion battery |
| CN109560255B (en) * | 2018-12-20 | 2022-05-10 | 天津市捷威动力工业有限公司 | Lithium ion battery pole piece processing method, pole piece and lithium ion battery |
| CN111864261A (en) * | 2019-04-26 | 2020-10-30 | 宁德时代新能源科技股份有限公司 | Electrolyte and lithium ion battery |
| KR102293034B1 (en) * | 2020-06-04 | 2021-08-24 | 에스케이이노베이션 주식회사 | Cathode active material for lithium secondary battery and lithium secondary battery including the same |
| CN114079046B (en) * | 2020-08-14 | 2024-01-09 | 比亚迪股份有限公司 | Mixed positive electrode material, positive electrode plate, manufacturing method of positive electrode plate and battery |
| CN114079047B (en) * | 2020-08-14 | 2023-12-12 | 比亚迪股份有限公司 | Composite positive electrode material, positive electrode plate, manufacturing method of positive electrode plate and battery |
| CN113488700A (en) * | 2021-06-30 | 2021-10-08 | 湖南立方新能源科技有限责任公司 | Infiltration method of secondary battery and application thereof |
Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1956243A (en) * | 2005-10-24 | 2007-05-02 | 比亚迪股份有限公司 | Battery pole piece and manufacturing method of lithium ion secordary battery containing the pole piece |
| CN1988219A (en) * | 2005-12-22 | 2007-06-27 | 比亚迪股份有限公司 | Method for preparing battery electrode and its device |
| JP2007265889A (en) * | 2006-03-29 | 2007-10-11 | Dainippon Printing Co Ltd | Electrode plate for nonaqueous electrolytic solution secondary battery, and its manufacturing method as well as nonaqueous electrolytic solution secondary battery |
| CN101207195A (en) * | 2006-12-22 | 2008-06-25 | 比亚迪股份有限公司 | Method for preparation of battery pole piece |
| JP2011198559A (en) * | 2010-03-18 | 2011-10-06 | Nissan Motor Co Ltd | Electrode manufacturing method, electrode manufacturing apparatus, and electrode |
| CN102496482A (en) * | 2011-12-26 | 2012-06-13 | 东莞新能源科技有限公司 | Pole piece of supercapacitor and production method for pole piece |
| CN102694150A (en) * | 2012-06-12 | 2012-09-26 | 宁德新能源科技有限公司 | Method for preparing lithium-ion secondary battery pole piece |
| JP2013000727A (en) * | 2011-06-21 | 2013-01-07 | Fuji Kikai Kogyo Kk | Intermittent coating apparatus |
| JP2015076230A (en) * | 2013-10-08 | 2015-04-20 | 株式会社豊田自動織機 | Roll press device |
-
2016
- 2016-05-18 CN CN201610331430.0A patent/CN107403905B/en active Active
Patent Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1956243A (en) * | 2005-10-24 | 2007-05-02 | 比亚迪股份有限公司 | Battery pole piece and manufacturing method of lithium ion secordary battery containing the pole piece |
| CN1988219A (en) * | 2005-12-22 | 2007-06-27 | 比亚迪股份有限公司 | Method for preparing battery electrode and its device |
| JP2007265889A (en) * | 2006-03-29 | 2007-10-11 | Dainippon Printing Co Ltd | Electrode plate for nonaqueous electrolytic solution secondary battery, and its manufacturing method as well as nonaqueous electrolytic solution secondary battery |
| CN101207195A (en) * | 2006-12-22 | 2008-06-25 | 比亚迪股份有限公司 | Method for preparation of battery pole piece |
| JP2011198559A (en) * | 2010-03-18 | 2011-10-06 | Nissan Motor Co Ltd | Electrode manufacturing method, electrode manufacturing apparatus, and electrode |
| JP2013000727A (en) * | 2011-06-21 | 2013-01-07 | Fuji Kikai Kogyo Kk | Intermittent coating apparatus |
| CN102496482A (en) * | 2011-12-26 | 2012-06-13 | 东莞新能源科技有限公司 | Pole piece of supercapacitor and production method for pole piece |
| CN102694150A (en) * | 2012-06-12 | 2012-09-26 | 宁德新能源科技有限公司 | Method for preparing lithium-ion secondary battery pole piece |
| JP2015076230A (en) * | 2013-10-08 | 2015-04-20 | 株式会社豊田自動織機 | Roll press device |
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