阅读说明：本技术 功能涂覆隔膜及其制备方法、锂离子电芯、锂离子电池包及其应用 (Functional coating diaphragm and preparation method thereof, lithium ion battery cell, lithium ion battery pack and application thereof ) 是由 徐峤 洪晔 李进 梅骜 于 2020-03-26 设计创作，主要内容包括：本发明公开了一种功能涂覆隔膜及其制备方法、锂离子电芯、锂离子电池包及其应用,功能涂覆隔膜包括基膜、涂覆于基膜单面或双面上的陶瓷涂层,以及涂覆于陶瓷涂层上的复合涂覆层,复合涂覆层包含陶瓷材料及聚合物,陶瓷材料以团聚颗粒的形式分布于聚合物中起到支架作用。致密的陶瓷涂层为隔膜提供优越的耐热性能,复合涂敷层中的聚合物可以提供极片与隔膜之间的粘接力,而陶瓷材料给复合涂覆层提供了有效的支撑,且在隔膜和极片之间制造了空间,提高了隔膜的浸润性和保液量,并为锂电池充放电过程中负极的反复膨胀收缩提供了一定的空间或缓冲,从而大大改善电池的充放电性能和循环性能。(The invention discloses a functional coating diaphragm and a preparation method thereof, a lithium ion battery cell, a lithium ion battery pack and application thereof. The compact ceramic coating provides excellent heat resistance for the diaphragm, the polymer in the composite coating layer can provide bonding force between the pole piece and the diaphragm, the ceramic material provides effective support for the composite coating layer, a space is formed between the diaphragm and the pole piece, the wettability and the liquid retention of the diaphragm are improved, a certain space or buffer is provided for repeated expansion and contraction of a negative electrode in the charging and discharging processes of the lithium battery, and therefore the charging and discharging performance and the cycle performance of the battery are greatly improved.)

1. A functionally coated separator, comprising:

a base film;

a ceramic coating coated on one side or both sides of the base film; and

the composite coating layer is coated on the ceramic coating and comprises a ceramic material and a polymer, and the ceramic material is distributed in the polymer in the form of agglomerated particles and plays a role of a bracket.

2. The functionally coated separator according to claim 1, wherein the base membrane is selected from one of a dry PP porous separator, a dry PE porous separator, a wet PE porous separator, or a PP/PE/PP composite three-layer porous separator, a non-woven fabric porous separator, the thickness of the base membrane is between 7 and 25um, and the porosity of the base membrane is between 35 and 75%.

3. The functionally coated membrane according to claim 1, wherein the functionally coated membrane has a thickness of between 18 and 35um, the ceramic coating has a thickness of between 1 and 15um, preferably the ceramic coating has a thickness of between 3 and 6 um; the thickness of the composite coating layer is between 1 and 15 microns, and preferably, the thickness of the composite coating layer is between 2 and 5 microns.

4. The functionally coated membrane of claim 1 wherein the functionally coated membrane has an areal density of from 10 to 40 grams per square meter, the ceramic coating and the composite coating layer comprise a functional coating layer, and the functional coating layer has an areal density of from 3 to 15 grams per square meter.

5. The functionally coated separator of claim 1, wherein a ceramic coating slurry is applied to one or both sides of the base film and dried to obtain the ceramic coating, wherein the ceramic coating slurry comprises, in parts by weight: 30-70 parts of ceramic material, 0.1-5 parts of dispersing agent, 0.1-10 parts of water-based acrylic latex and 0.5-5 parts of sodium carboxymethyl cellulose solution, wherein the mass fraction of the water-based acrylic latex is 40-50%, and the mass fraction of the sodium carboxymethyl cellulose solution is 3%.

6. The functionally coated separator of claim 1, wherein a composite coating slurry is applied to the ceramic coating layer and dried to obtain a composite coating layer, wherein the composite coating slurry comprises, in parts by weight: 50-90 parts of ceramic material, 10-50 parts of polymer particles, 0.5-10 parts of dispersing agent, 0.5-10 parts of wetting agent, 3-10 parts of adhesive and 0.1-8 parts of thickening agent.

7. The functionally coated separator according to claim 5 or 6, wherein the ceramic material is selected from the group consisting of alumina, silica, boehmite, zirconia, zinc oxideThe ceramic material is characterized by comprising one or more of titanium dioxide, magnesium oxide and barium sulfate, the particle size of the ceramic material is 50-1800 um, the D50 of the ceramic material particles is 50-1500 nm, and the specific surface area of the ceramic material is 0.5-200 m²Between/g.

8. The functionally coated separator of claim 5 or 6, wherein the dispersant is one or a combination of polyacrylic acid (PAA), polyethylene glycol (PEG), sodium polyacrylate (PAA-Na), potassium polyacrylate (PAA-K), sodium polymetaphosphate, sodium silicate, and sodium dodecyl sulfate.

9. The functionally coated separator of claim 6, wherein the polymer particles are one or more of polyvinylidene fluoride (PVDF), Polytetrafluoroethylene (PTFE), polyvinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, polyethylene oxide, and polymethyl methacrylate, and the particle size of the polymer particles is 0.1-2 um.

10. The functionally coated separator of claim 6 wherein the wetting agent is one or more of a fluorinated alkyl methoxy ether alcohol, a fluorinated alkyl ethoxy ether alcohol, an alkylphenol ethoxylate, a fatty alcohol ethoxylate, and a fatty acid ethoxylate.

11. The functionally coated separator of claim 6, wherein the adhesive is one or more of styrene-butadiene latex, pure benzene latex, styrene-acrylic latex, polymethacrylate, polybutylmethacrylate, polyethylacrylate, polyvinyl alcohol, ethylene-vinyl acetate copolymer, polyvinyl acetate, and polyurethane.

12. The functionally coated separator of claim 6, wherein the thickener is one or a combination of several of hydroxymethyl cellulose, methyl hydroxyethyl cellulose, sodium carboxymethyl cellulose (CMC-Na), Polyacrylamide (PAM), and sodium alginate.

13. A method for producing a functionally coated separator according to any one of claims 1 to 12, comprising the steps of:

(1) preparing ceramic slurry, coating the ceramic slurry on one side or two sides of a base film, and drying to obtain a ceramic coating;

(2) preparing composite coating slurry, coating the composite coating slurry on the ceramic coating, drying to obtain a composite coating layer, and further obtaining the functional coating diaphragm, wherein the composite coating slurry comprises a ceramic material and a polymer, and the ceramic material is distributed in the polymer in the form of agglomerated particles to play a role of a support.

14. The method of preparing a functionally coated separator as claimed in claim 13, wherein the step (1) comprises:

adding deionized water and a dispersing agent into a stirrer, wherein the dispersing agent accounts for 0.5-5%, and stirring to obtain a mixed slurry I;

adding a ceramic material into the mixed slurry I, and stirring to form mixed slurry II;

adding the aqueous acrylic latex solution and the sodium carboxymethyl cellulose solution into the mixed slurry II, and stirring to form slurry III;

stirring for 1h at a low speed in vacuum, dispersing and screening to obtain ceramic slurry, coating the ceramic slurry on a base film, and drying to obtain a ceramic coating.

15. The method of preparing a functionally coated separator as recited in claim 14, wherein the step (2) comprises:

adding deionized water, a dispersing agent and a thickening agent into a stirrer, and stirring at a low speed until the deionized water, the dispersing agent and the thickening agent are completely dissolved to obtain mixed slurry I;

adding polymer particles into the mixed slurry I, and stirring and dispersing to obtain mixed slurry II;

adding a wetting agent into the mixed slurry II, uniformly stirring, adding an adhesive, and sieving by using a screen to obtain mixed slurry III;

adding the ceramic slurry into the mixed slurry III, and stirring to obtain composite coating slurry; and

and coating the composite coating slurry on the ceramic coating, drying to obtain a composite coating layer, and further obtaining the functional coating diaphragm, wherein the composite coating slurry comprises a ceramic material and a polymer formed by dissolving polymer particles, and the ceramic material is distributed in the polymer in the form of agglomerated particles to play a role of a support.

16. A lithium ion battery cell, comprising:

a negative plate;

a positive plate;

the functionally coated separator according to any one of claims 1 to 12, which is interposed between the negative electrode sheet and the positive electrode sheet; and

the packaging bag is made of an aluminum-plastic film composite material, and the negative plate, the positive plate and the bare cell made of the functional coating diaphragm are arranged in the packaging bag.

17. A lithium ion battery pack, characterized in that it comprises a lithium ion cell according to claim 16.

18. Applying the lithium ion battery pack of claim 17 to an automobile, motorcycle, or bicycle.

Technical Field

The invention relates to the field of energy storage devices, in particular to a functional coating diaphragm and a preparation method thereof, a lithium ion battery cell, a lithium ion battery pack and application thereof.

Background

The lithium ion battery diaphragm is an electric insulation material component which is arranged between the anode and the cathode of the battery and allows ions to pass through, can preserve electrolyte through gaps, and can prevent active substances from being mixed to prevent the anode and the cathode from contacting. The diaphragm used in the lithium ion battery with high energy density is mostly composed of a basal membrane and a functional coating layer; the base film takes polyolefin resin as a main raw material, has a porous structure and has a thickness of 5-30 mu m; the functional coating layer is widely used and generally coated on the surface of the base film to improve the performance of the separator.

The lithium ion battery is widely applied to the fields of 3C digital, energy storage and power automobiles, the industry of new energy automobiles is developed rapidly in recent years, the requirement on the energy density of the lithium ion battery is higher and higher, the thickness of a diaphragm is reduced along with the requirement, and the safety of a battery core is directly influenced. In order to achieve the design and performance targets of 300Wh/kg power batteries, the chemical system of the lithium ion battery with a high nickel positive electrode and a silicon negative electrode is the best choice. The high-nickel anode has strong oxidizability, the silicon-containing cathode can repeatedly expand and contract in the charging and discharging processes to cause the breakage of an SEI film, electrolyte is consumed to continuously generate SEI and extrude a diaphragm, the performance of the battery is reduced, and the aged and damaged diaphragm shrinks, melts and breaks to cause the internal short circuit of the battery, possibly causing the combustion and even explosion of the battery. Meanwhile, when the battery is charged for multiple cycles, under high-current charging or low-temperature charging, lithium can be separated out from the negative electrode due to local polarization, and the generated lithium dendrite can pierce through the diaphragm to cause short circuit of the positive electrode and the negative electrode. The single-layer polyolefin diaphragm can not meet the requirements of safety and use of the lithium ion power battery, the current solution with the widest applicability is to coat an aluminum oxide ceramic material on the diaphragm, and the thermal stability and the mechanical strength of the diaphragm can be effectively improved after the diaphragm is coated with the ceramic, so that the service life of the diaphragm is prolonged, and the safety performance is improved. But the traditional ceramic diaphragm coating still directly contacts with the anode and the cathode, side reactions still occur, the liquid retention performance of the diaphragm cannot be improved, and the battery performance improvement space is large. In order to further improve the performance of batteries and separators, lithium ion power battery separators coated with functional coating layers have received increasing attention.

The diaphragm of most of the existing lithium batteries for mass production is generally coated with single-sided or double-sided alumina nano ceramic particles on a base film, so that the thermal stability of the diaphragm is improved, and the oxidation resistance is enhanced. Polymer glue coating layers can be added on two surfaces of a diaphragm of part of products so as to provide the adhesion of the diaphragm to a pole piece, increase the hardness of the battery cell and reduce the processing difficulty. The coatings are functionally unique and independent of each other, multiple coatings combine the advantages of different coatings, ceramic is used as an oxidation resistant, thermally enhanced stable coating, and polymer is used to provide adhesion.

However, such a separator having ceramic and polymer coatings still has various problems, whether the polymer coating is made using a spray coating process or a roll coating process. Specifically, the polymer coating prepared by the spraying process only has a small liquid retention function and is not uniformly distributed, so that the size uniformity of pores between the pole piece and the diaphragm is poor, and the uniformity of current density between the pole pieces is influenced. After the electric core is subjected to hot pressing, gaps between the ceramic coating and the pole pieces are small, the negative pole can directly extrude a ceramic layer closely connected with the base film when expanding and contracting under charging and discharging, the diaphragm is aged, the volume change of the electric core cannot be inhibited, and the effect of improving the cycle performance is limited. The polymer coating prepared by the roller coating process has smaller gaps than a spraying process, is uniformly distributed, reduces the air permeability of the diaphragm, increases the possibility of hole blocking, increases the battery impedance, reduces the liquid retention, has little effect on improving the cycle performance, and only obviously improves the processing performance of the battery core.

Therefore, it is necessary to provide a method for improving the adhesion between the electrode sheet and the separator, improving the size of the gap between the electrode sheet and the separator, providing a certain space for the repeated expansion and contraction of the negative electrode during the charge and discharge of the lithium battery, and improving the wettability and the liquid retention of the separator.

Disclosure of Invention

The first purpose of the invention is to provide a functional coating diaphragm, which can ensure the adhesion between the diaphragm and a pole piece, improve the size of a gap between the diaphragm and the pole piece, provide a certain space for the repeated expansion and contraction of a negative electrode in the charge and discharge processes of a lithium ion cell, and improve the wettability and the liquid retention capacity of the diaphragm.

The second purpose of the invention is to provide a preparation method of the functional coating diaphragm, and the functional coating diaphragm prepared by the preparation method can ensure the adhesion between the diaphragm and a pole piece, improve the size of a gap between the diaphragm and the pole piece, provide a certain space for the repeated expansion and contraction of a negative electrode in the charge and discharge processes of a lithium ion battery cell, and improve the wettability and the liquid retention capacity of the diaphragm.

The third objective of the present invention is to provide a lithium ion battery cell, which includes a functional coating diaphragm, and the functional coating diaphragm can ensure the adhesion between the functional coating diaphragm and a pole piece, improve the size of a gap between the functional coating diaphragm and the pole piece, provide a certain space for the repeated expansion and contraction of a negative electrode during the charge and discharge processes of the lithium ion battery cell, and improve the wettability and the liquid retention capacity of the diaphragm.

The fourth objective of the present invention is to provide a lithium ion battery pack, which includes a lithium ion battery cell, wherein the lithium ion battery cell includes a functional coating diaphragm, and the functional coating diaphragm can ensure adhesion between the functional coating diaphragm and a pole piece, improve the size of a gap between the functional coating diaphragm and the pole piece, provide a certain space for repeated expansion and contraction of a negative electrode during charging and discharging of the lithium ion battery cell, and improve the wettability and the liquid retention capacity of the diaphragm.

A fifth object of the present invention is to apply the lithium ion battery pack to an automobile, a motorcycle, or a bicycle.

In order to achieve the above object, the present invention provides a functional coating separator, which includes a base film, a ceramic coating layer coated on one or both sides of the base film, and a composite coating layer coated on the ceramic coating layer, wherein the composite coating layer includes a ceramic material and a polymer, and the ceramic material is distributed in the polymer in the form of agglomerated particles to function as a scaffold.

Further, the base membrane is selected from one of a dry PP porous membrane, a dry PE porous membrane, a wet PE porous membrane or a PP/PE/PP composite three-layer porous membrane and a non-woven fabric porous membrane, the thickness of the base membrane is 7-25 um, and the porosity of the base membrane is 35-75%.

Further, the thickness of the functional coating diaphragm is 18-35 um, the thickness of the ceramic coating is 1-15 um, and preferably the thickness of the ceramic coating is 3-6 um; the thickness of the composite coating layer is between 1 and 15 microns, and preferably, the thickness of the composite coating layer is between 2 and 5 microns.

The functional coating membrane is characterized in that the area density of the functional coating membrane is between 10 and 40 grams per square meter, the ceramic coating and the composite coating layer form a functional coating layer, and the area density of the functional coating layer is between 3 and 15 grams per square meter.

Further, coating ceramic coating slurry on one side or two sides of the base film, and drying to obtain the ceramic coating, wherein the ceramic coating slurry comprises the following components in parts by weight: 30-70 parts of ceramic material, 0.1-5 parts of dispersing agent, 0.1-10 parts of water-based acrylic latex and 0.5-5 parts of sodium carboxymethyl cellulose solution, wherein the mass fraction of the water-based acrylic latex is 40-50%, and the mass fraction of the sodium carboxymethyl cellulose solution is 3%.

Further, coating the ceramic coating with composite coating slurry, and drying to obtain a composite coating layer, wherein the composite coating slurry comprises the following components in parts by weight: 50-90 parts of ceramic material, 10-50 parts of polymer particles, 0.5-10 parts of dispersing agent, 0.5-10 parts of wetting agent, 3-10 parts of adhesive and 0.1-8 parts of thickening agent.

Further, the ceramic material is selected from one or a combination of more of aluminum oxide, silicon dioxide, boehmite, zirconia, zinc oxide, titanium dioxide, magnesium oxide and barium sulfate, the particle size of the ceramic material is 50-1800 um, the D50 of the ceramic material particles is 50-1500 nm, and the specific surface area of the ceramic material is 0.5-200 m²Between/g.

Further, the dispersant is one or a combination of polyacrylic acid (PAA), polyethylene glycol (PEG), sodium polyacrylate (PAA-Na), potassium polyacrylate (PAA-K), sodium polymetaphosphate, sodium silicate and sodium dodecyl sulfate.

Further, the polymer particles are one or a composition of several of polyvinylidene fluoride (PVDF), Polytetrafluoroethylene (PTFE), polyvinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, polyethylene oxide and polymethyl methacrylate, and the particle size of the polymer particles is 0.1-2 um.

Further, the wetting agent is one or a combination of more of fluoroalkyl methoxy ether alcohol, fluoroalkyl ethoxy ether alcohol, alkylphenol ethoxylates, fatty alcohol-polyoxyethylene ether and fatty acid-polyoxyethylene ether.

Further, the adhesive is one or a combination of more of styrene-butadiene latex, pure benzene latex, styrene-acrylic latex, polymethacrylate, polybutylmethacrylate, polyethylacrylate, polyvinyl alcohol, ethylene-vinyl acetate copolymer, polyvinyl acetate and polyurethane.

Further, the thickening agent is one or a composition of more of hydroxymethyl cellulose, methyl hydroxyethyl cellulose, sodium carboxymethyl cellulose (CMC-Na), Polyacrylamide (PAM) and sodium alginate.

The present invention also provides a method for preparing a functional coated separator, for preparing the functional coated separator as set forth in the above, the method comprising the steps of:

(1) preparing ceramic slurry, coating the ceramic slurry on one side or two sides of a base film, and drying to obtain a ceramic coating;

(2) preparing composite coating slurry, coating the composite coating slurry on the ceramic coating, drying to obtain a composite coating layer, and further obtaining the functional coating diaphragm, wherein the composite coating slurry comprises a ceramic material and a polymer, and the ceramic material is distributed in the polymer in the form of agglomerated particles to play a role of a support.

Further, the step (1) includes:

adding deionized water and a dispersing agent into a stirrer, wherein the dispersing agent accounts for 0.5-5%, and stirring to obtain a mixed slurry I;

adding a ceramic material into the mixed slurry I, and stirring to form mixed slurry II;

adding the aqueous acrylic latex solution and the sodium carboxymethyl cellulose solution into the mixed slurry II, and stirring to form slurry III; and

stirring for 1h at a low speed in vacuum, dispersing and screening to obtain ceramic slurry, coating the ceramic slurry on a base film, and drying to obtain a ceramic coating.

More specifically, the step (1) includes:

A. adding deionized water and a dispersing agent into a planetary stirrer with an ultrasonic vibration plate, wherein the dispersing agent accounts for 0.5-5%, simultaneously performing ultrasonic vibration and stirring, and adjusting the pH value to 7.5-8.5 to form mixed slurry I;

B. adding a ceramic material into the mixed slurry I, and simultaneously performing ultrasonic oscillation and stirring to form mixed slurry II;

C. adding the aqueous acrylic latex solution and the sodium carboxymethyl cellulose solution into the mixed slurry II, and simultaneously performing ultrasonic oscillation and stirring to form mixed slurry III;

D. reducing the stirring speed, closing ultrasonic oscillation, starting vacuum, stirring for 1h, then closing the vacuum to obtain primary ceramic slurry, pre-dispersing by a ball mill, dispersing by a high-speed dispersion machine, and screening by a screen to obtain ceramic slurry;

E. and placing the base film on a coating machine, coating the ceramic slurry on one or two sides of the base film, optionally selecting a coating mode from micro gravure coating, dip coating and extrusion coating, wherein the coating speed is 20-80 m/min, and drying after coating to obtain the ceramic coating.

Further, the step (2) includes:

adding deionized water, a dispersing agent and a thickening agent into a stirrer, and stirring at a low speed until the deionized water, the dispersing agent and the thickening agent are completely dissolved to obtain mixed slurry I;

adding polymer particles into the mixed slurry I, and stirring and dispersing to obtain mixed slurry II;

adding a wetting agent into the mixed slurry II, uniformly stirring, adding an adhesive, and sieving by using a screen to obtain mixed slurry III;

adding the ceramic slurry into the mixed slurry III, and stirring to obtain composite coating slurry; and

and coating the composite coating slurry on the ceramic coating, drying to obtain a composite coating layer, and further obtaining the functional coating diaphragm, wherein the composite coating slurry comprises a ceramic material and a polymer formed by dissolving polymer particles, and the ceramic material is distributed in the polymer in the form of agglomerated particles to play a role of a support.

More specifically, the step (2) includes:

A. adding deionized water, a dispersing agent and a thickening agent into a planetary stirrer, and stirring at a low speed until the deionized water, the dispersing agent and the thickening agent are completely dissolved to obtain mixed slurry I;

B. adding polymer particles into the mixed slurry I, stirring for 30-90 minutes, and then starting high-speed dispersion to obtain mixed slurry II;

C. adding a wetting agent into the mixed slurry II, adding an adhesive after uniformly stirring, and sieving by using a 400-mesh sieve to obtain mixed slurry III;

D. adding the ceramic slurry into the mixed slurry III, and slowly stirring to obtain composite coating slurry;

E. and placing the base film coated with the ceramic coating on a coating machine, coating the composite coating slurry on the ceramic coating, wherein the selected coating mode can be one of micro-gravure coating, dip coating or extrusion coating, the coating speed is 20-80 m/min, and drying after coating to obtain a composite coating layer, thereby obtaining the functional coating diaphragm.

The invention also provides a lithium ion battery cell, which comprises a negative plate, a positive plate, the functional coating diaphragm and a packaging bag, wherein the functional coating diaphragm is arranged between the negative plate and the positive plate, the packaging bag is made of an aluminum-plastic film composite material, and the negative plate, the positive plate and a bare battery cell made of the functional coating diaphragm are arranged in the packaging bag.

The invention also provides a lithium ion battery pack which comprises the lithium ion battery cell.

The lithium ion battery pack is also applied to automobiles, motorcycles or bicycles.

Compared with the prior art, the invention provides the functional coating diaphragm which comprises a base film, a ceramic coating coated on one side or two sides of the base film and a composite coating coated on the ceramic coating, wherein the composite coating comprises a ceramic material and a polymer, and the ceramic material is distributed in the polymer in the form of agglomerated particles to play a role of a support. The functional coating diaphragm designed by the invention has the advantages that the compact ceramic coating layer provides excellent heat resistance for the diaphragm, the polymer in the composite coating layer can provide the adhesive force between the pole piece and the diaphragm, the dislocation of the pole piece of the battery is avoided, the ceramic material is distributed in the polymer in the form of agglomerated particles, the ceramic material provides effective support for the composite coating layer, a space is formed between the diaphragm and the pole piece, the size of a gap between the diaphragm and the pole piece is improved, the diaphragm can absorb and store more electrolyte, the wettability and the liquid retention of the diaphragm are improved, a certain space or buffer is provided for the repeated expansion and contraction of a negative electrode in the charge-discharge process of the lithium battery, the extrusion between the pole piece and the diaphragm is reduced, the service life of the diaphragm is prolonged, and the charge-discharge performance and the cycle performance of the battery are greatly improved. The preparation process of the functional coating diaphragm is simple, the cost is low, and the slurry with water as the solvent is very environment-friendly.

Drawings

Fig. 1 is an electron microscope scanning picture of a functional coated membrane according to a first embodiment of the present invention.

Detailed Description

The "ranges" disclosed herein are in the form of lower and upper limits. There may be one or more lower limits, and one or more upper limits, respectively. The given range is defined by the selection of a lower limit and an upper limit. The selected lower and upper limits define the boundaries of the particular range. All ranges that can be defined in this manner are inclusive and combinable, i.e., any lower limit can be combined with any upper limit to form a range. For example, ranges of 60-120 and 80-110 are listed for particular parameters, with the understanding that ranges of 60-110 and 80-120 are also contemplated. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present invention, all embodiments and preferred embodiments mentioned herein may be combined with each other to form a new technical solution, if not specifically stated.

In the present invention, all the technical features mentioned herein and preferred features may be combined with each other to form a new technical solution, if not specifically stated.

In the present invention, all the steps mentioned herein may be performed sequentially or randomly, if not specifically stated, but preferably sequentially.

The invention provides a lithium ion battery pack, which comprises a battery module, a circuit board, a shell and the like, wherein the battery module, the circuit board and the like are assembled in the shell to form the lithium ion battery pack, the lithium ion battery pack has various specifications, can be adjusted and designed according to needs, and is not limited in the process, and the assembly mode of the lithium ion battery pack in the prior art can be applied to the invention.

The battery module is composed of a plurality of lithium ion battery cells connected in series and in parallel, and similarly, the battery module has various specifications and can be adjusted and designed according to needs.

The lithium ion battery pack can be applied to an automobile, a motorcycle or a bicycle to provide power for the automobile, the motorcycle or the bicycle.

Various embodiments of the functionally coated separator, lithium ion battery cell of the present invention are described below.

Example 1

(1) Preparation of functional coated separator

Preparing ceramic slurry, coating the ceramic slurry on one side or two sides of a base film, and drying to obtain a ceramic coating; the method specifically comprises the following steps:

A. adding deionized water and a dispersing agent into a planetary stirrer with an ultrasonic vibration plate, wherein the dispersing agent accounts for 0.5-5%, and simultaneously performing ultrasonic vibration and stirring to adjust the pH value to form mixed slurry I;

B. adding a ceramic material into the mixed slurry I, and simultaneously performing ultrasonic oscillation and stirring to form mixed slurry II;

C. adding the aqueous acrylic latex solution and the sodium carboxymethyl cellulose solution into the mixed slurry II, and simultaneously performing ultrasonic oscillation and stirring to form mixed slurry III;

D. reducing the stirring speed, closing ultrasonic oscillation, starting vacuum, stirring for 1h, then closing the vacuum to obtain primary ceramic slurry, pre-dispersing by a ball mill, dispersing by a high-speed dispersion machine, and screening by a screen to obtain ceramic slurry;

E. and placing the base film on a coating machine, coating the ceramic slurry on one or two sides of the base film, optionally selecting a coating mode from micro gravure coating, dip coating and extrusion coating, wherein the coating speed is 20-80 m/min, and drying after coating to obtain the ceramic coating.

And then, preparing composite coating slurry, coating the composite coating slurry on the ceramic coating, and drying to obtain a composite coating layer, thereby obtaining the functional coating diaphragm. The method specifically comprises the following steps:

A. adding deionized water, a dispersing agent and a thickening agent into a planetary stirrer, and stirring at a low speed until the deionized water, the dispersing agent and the thickening agent are completely dissolved to obtain mixed slurry I;

B. adding polymer particles into the mixed slurry I, stirring for 30-90 minutes, and then starting high-speed dispersion to obtain mixed slurry II;

C. adding a wetting agent into the mixed slurry II, adding an adhesive after uniformly stirring, and sieving by using a 400-mesh sieve to obtain mixed slurry III;

D. adding the ceramic slurry into the mixed slurry III, and slowly stirring to obtain composite coating slurry;

E. and placing the base film coated with the ceramic coating on a coating machine, coating the composite coating slurry on the ceramic coating, wherein the selected coating mode can be one of micro-gravure coating, dip coating or extrusion coating, the coating speed is 20-80 m/min, and drying after coating to obtain a composite coating layer, thereby obtaining the functional coating diaphragm.

Wherein, the ceramic material is selected from aluminum oxide, the dispersing agent is selected from polyacrylic acid (PAA), the polymer particles are selected from polyvinylidene fluoride (PVDF), the wetting agent is selected from fluoroalkyl methoxy ether alcohol, the adhesive is selected from styrene-butadiene latex, and the thickening agent is selected from hydroxymethyl cellulose.

An electron microscope scanning picture of the functionally coated separator prepared in example 1 is shown in fig. 1.

(2) Preparation of positive plate

LiNi-Co-Mn LiNi as positive electrode active material_0.5Co_0.2Mn_0.3O₂Mixing the conductive carbon black (super-P) as a conductive agent, Carbon Nano Tubes (CNT) and polyvinylidene fluoride (PVDF) as a binding agent according to a mass ratio of 96.8: 1.5: 0.5: 1.2, adding N-methyl pyrrolidone (NMP), and stirring and mixing uniformly by a vacuum stirrer to obtain the anode active material slurry. And (3) uniformly coating the slurry on two surfaces of an aluminum foil (with the thickness of 12 mu m) positive current collector, and drying, cold pressing and cutting to obtain the positive plate.

(3) Preparation of negative plate

Mixing the negative active material artificial graphite, the silicon-carbon composite material, conductive carbon black (super-P) serving as a conductive agent, Carbon Nano Tubes (CNT), Styrene Butadiene Rubber (SBR) serving as a binding agent, sodium carboxymethylcellulose (CMC) and polyacrylic acid (PAA) according to a mass ratio of 85: 9: 1.5: 0.5: 2.2: 1.4: 0.4, adding deionized water, and stirring and mixing uniformly by a vacuum stirrer. Then, an aqueous solution of lithium nitrate was added, the mass of lithium nitrate being 0.5% of the total mass of the negative electrode active material, and the slurry was further mixed and dispersed to obtain a negative electrode slurry. And (3) uniformly coating the negative electrode slurry on two surfaces of a copper foil (with the thickness of 8 mu m) negative electrode current collector, and drying, cold pressing and slitting to obtain a negative electrode sheet.

(4) Preparation of lithium ion cell

The functional coating diaphragm is arranged between the negative plate and the positive plate, a square naked battery cell is prepared in a winding mode, a packaging bag is made of an aluminum-plastic film composite material, the naked battery cell is placed into the packaging bag for packaging to obtain a dry battery cell, and the dry battery cell is subjected to the procedures of baking, dewatering, liquid injection, sealing, standing, formation, degassing packaging, capacity grading and the like to obtain the lithium ion battery cell.

It should be noted that, in this embodiment, the square bare cell is prepared by winding, of course, in other embodiments, the bare cell may also be prepared by lamination, or the bare cell may also be prepared into other shapes, such as a cylinder or an ellipse, that is, the conventional preparation method of the lithium ion cell may be applied to the present invention, and is not limited herein.

Example 2

The functional coating diaphragm, the positive plate, the negative plate and the lithium ion battery cell are prepared according to the method in the embodiment 1, and the only difference is that a ceramic material is selected from silicon dioxide, a dispersing agent is selected from polyethylene glycol (PEG), polymer particles are selected from Polytetrafluoroethylene (PTFE), a wetting agent is selected from fluoroalkyl ethoxy ether alcohol, an adhesive is selected from pure benzene latex, and a thickening agent is selected from methyl hydroxyethyl cellulose.

Example 3

The functional coating diaphragm, the positive plate, the negative plate and the lithium ion battery cell are prepared according to the method in the embodiment 1, and the only difference is that the ceramic material is selected from boehmite, the dispersing agent is selected from sodium polyacrylate (PAA-Na), the polymer particles are selected from polyvinylidene fluoride-hexafluoropropylene copolymer, the wetting agent is selected from alkylphenol polyoxyethylene ether, the adhesive is selected from styrene-acrylic latex, and the thickening agent is selected from sodium carboxymethylcellulose (CMC-Na).

Example 4

The functional coating diaphragm, the positive plate, the negative plate and the lithium ion battery cell are prepared according to the method in the embodiment 1, and the only difference is that the ceramic material is selected from zirconia, the dispersing agent is selected from potassium polyacrylate (PAA-K), the polymer particles are selected from polyacrylonitrile, the wetting agent is selected from fatty alcohol-polyoxyethylene ether, the adhesive is selected from polymethacrylate, and the thickening agent is selected from Polyacrylamide (PAM).

Example 5

The functional coating diaphragm, the positive plate, the negative plate and the lithium ion battery cell are prepared according to the method in the embodiment 1, and the only difference is that the ceramic material is selected from zinc oxide, the dispersing agent is selected from sodium polymetaphosphate, the polymer particles are selected from polyethylene oxide, the wetting agent is selected from fatty acid polyoxyethylene ether, the adhesive is selected from polybutylmethacrylate, and the thickening agent is selected from sodium alginate.

Example 6

The functional coating diaphragm, the positive plate, the negative plate and the lithium ion battery cell are prepared according to the method in the embodiment 1, and the only difference is that the ceramic material is titanium dioxide, the dispersing agent is sodium silicate, the polymer particles are polymethyl methacrylate, and the adhesive is polyethyl acrylate.

Example 7

The functional coating diaphragm, the positive plate, the negative plate and the lithium ion battery cell are prepared according to the method in the embodiment 1, and the only difference is that the ceramic material is selected from magnesium oxide, the dispersing agent is selected from sodium dodecyl sulfate, the wetting agent is fluoroalkyl ethoxy ether alcohol, the adhesive is selected from polyvinyl alcohol, and the thickening agent is selected from methyl hydroxyethyl cellulose.

Example 8

The functional coating diaphragm, the positive plate, the negative plate and the lithium ion battery cell are prepared according to the method in the embodiment 1, and the only difference is that the ceramic material is barium sulfate, the polymer particles are Polytetrafluoroethylene (PTFE), the wetting agent is alkylphenol ethoxylate, the adhesive is ethylene-vinyl acetate copolymer, and the thickening agent is sodium carboxymethylcellulose (CMC-Na).

Comparative example 1

The functional coating diaphragm, the positive plate, the negative plate and the lithium ion battery cell are prepared according to the method in the embodiment 1, and the only difference is that no composite coating layer is arranged.

Comparative example 2

The functionally coated separator, the positive plate, the negative plate and the lithium ion battery cell were prepared as described in example 1, with the only difference being that no ceramic coating was present.

Comparative example 3

The functional coating diaphragm, the positive plate, the negative plate and the lithium ion battery cell are prepared according to the method in the embodiment 1, and the only difference is that the composite coating layer is not added with a ceramic material.

Comparative example 4

The functional coating diaphragm, the positive plate, the negative plate and the lithium ion battery cell are prepared according to the method in the embodiment 1, and the only difference is that no polymer particles are added in the composite coating layer.

And (3) testing the performance of the lithium ion battery cell:

test of ordinary temperature cycle Performance

In a thermostat at 25 ℃, the lithium ion cells obtained in the above examples 1 to 8 and comparative examples 1 to 4 were charged to 4.3V at a constant current of 1C, then charged to a current of 0.05C at a constant voltage, and then discharged to 2.5V at a constant current of 1C, so that charge/discharge cycles were performed, and the capacity retention rate was obtained after 200 cycles of the battery.

The lithium ion cell 200-cycle capacity retention ratio (%) (200-cycle discharge capacity/1-cycle discharge capacity × 100%

The data of the cycle capacity retention rate of the lithium ion cells in the examples 1 to 8 and the comparative examples 1 to 4 are shown in Table 1.

TABLE 1 retention of circulating capacity of each of the examples and comparative examples

As can be seen from table 1, the retention rate of the 200-cycle capacity of the lithium ion batteries of examples 1 to 8 is significantly improved compared to the respective comparative examples.

Compared with the prior art, the invention provides the functional coating diaphragm which comprises a base film, a ceramic coating coated on one side or two sides of the base film and a composite coating coated on the ceramic coating, wherein the composite coating comprises a ceramic material and a polymer, and the ceramic material is distributed in the polymer in the form of agglomerated particles to play a role of a support. The functional coating diaphragm designed by the invention has the advantages that the compact ceramic coating layer provides excellent heat resistance for the diaphragm, the polymer in the composite coating layer can provide the adhesive force between the pole piece and the diaphragm, the dislocation of the pole piece of the battery is avoided, the ceramic material is distributed in the polymer in the form of agglomerated particles, the ceramic material provides effective support for the composite coating layer, a space is formed between the diaphragm and the pole piece, the size of a gap between the diaphragm and the pole piece is improved, the diaphragm can absorb and store more electrolyte, the wettability and the liquid retention of the diaphragm are improved, a certain space or buffer is provided for the repeated expansion and contraction of a negative electrode in the charge-discharge process of the lithium battery, the extrusion between the pole piece and the diaphragm is reduced, the service life of the diaphragm is prolonged, and the charge-discharge performance and the cycle performance of the battery are greatly improved. The preparation process of the functional coating diaphragm is simple, the cost is low, and the slurry with water as the solvent is very environment-friendly.

The above disclosure is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the scope of the present invention, therefore, the present invention is not limited by the appended claims.