Battery monomer, isolating membrane, preparation method of isolating membrane, battery device and power utilization device

Abstract

The invention discloses a battery monomer, an isolating membrane, a preparation method of the isolating membrane, a battery device and a power utilization device, the battery monomer comprises the isolating membrane and electrolyte, and the isolating membrane comprises a porous base membrane; the coating is arranged on at least one side of the porous base membrane and comprises a polymer additive, and the polymer additive comprises a first functional group and a second functional group; the first functional group comprises one or more of bis (fluorosulfonyl) imino group, bis (trifluoromethyl) sulfonyl imino group, trifluoroboric acid group, hexafluorophosphoric acid group, sulfonic acid group, hexafluoroarsenate group, trifluoromethanesulfonic acid group, difluorophosphoric acid group, bis (oxalato) boric acid group, difluoro (oxalato) boric acid group, difluoro (oxalato) phosphoric acid group, tetrafluoro (oxalato) phosphoric acid group and imidazolyl; the second functional group comprises one or more of quaternary ammonium ions, pyrrolidinyl, pyrrolyl, piperidinyl, pyridyl and imidazolyl. The battery monomer has good dynamic performance; the invention provides the isolating membrane for realizing the beneficial effects of the battery monomer, the preparation method of the isolating membrane, the battery device and the power utilization device.

Description

Technical Field

[0001] This application belongs to the field of battery technology, specifically relating to a battery cell, a separator and its preparation method, a battery device and an electrical device. Background Technology

[0002] As the application of battery cells becomes more and more widespread, people's demands for battery cells are also increasing, such as the increasing requirements for energy density and fast charging performance of battery cells.

[0003] Therefore, how to enable battery cells to have higher levels of fast charging performance while maintaining high energy density is a technical problem that urgently needs to be solved. Summary of the Invention

[0004] This application provides a battery cell with good kinetic performance; this application also provides a separator capable of achieving the beneficial effects of the battery cell and a method for preparing the separator therefrom; this application also provides a battery device and an electrical device having the beneficial effects of the battery cell.

[0005] In a first aspect, this application provides a battery cell, comprising: a separator and an electrolyte; the separator comprises: a porous base membrane; a coating disposed on at least one side of the porous base membrane, the coating comprising a polymer additive, the polymer additive comprising a first functional group and a second functional group, the first functional group comprising one or more of bis(trifluoromethyl)sulfonylimino, bis(trifluoromethyl)sulfonylimino, trifluoroborate, hexafluorophosphate, sulfonic acid, hexafluoroarsenate, trifluoromethanesulfonic acid, difluorophosphate, bis(oxalate-borate), difluorooxalate-borate, difluorobis(oxalate-phosphate), tetrafluorooxalate-phosphate, and imidazole; the second functional group comprises one or more of quaternary ammonium ion, pyrrolyl, pyrrole, piperidinyl, pyridinyl, and imidazole; in the electrolyte environment, the first functional group forms a positively charged group, and the second functional group forms a negatively charged group.

[0006] In the embodiments of this application, the polymer additive in the coating of the separator contains a first functional group and a second functional group, which have both electron-donating sites and electron-accepting sites. The first functional group and the second functional group can form a unique dual-channel transport mechanism in the coating of the separator, providing a fast channel for active ions to pass through the separator, improving the ion conductivity of the separator, enhancing the active ion transport rate, reducing the transport resistance of active ions in the battery cell, and thus improving the fast charging performance of the battery cell.

[0007] In addition, the first and second functional groups in the polymer additives can have a certain selectivity for the transported metal ions, reduce the ion throughput of side reactions, reduce side reactions at the negative electrode interface, and also form a denser SEI film, which improves the cycle stability of the battery cell.

[0008] In some optional embodiments, the coating includes a polymer additive at a mass content of 0.1% to 10%, optionally 3% to 8%, based on the total mass of the coating. When the mass content of the polymer additive in the coating is within the above range, the polymer additive can achieve good adhesion with other components in the coating and the porous base film, enabling the battery cell to possess both good fast-charging performance and high energy density.

[0009] In some alternative embodiments, the first functional group and the second functional group respectively include an imidazole group, and the polymer additive includes one or more of polybenzimidazole, polyvinylimidazolium, polyacetylimidazole and N-vinylimidazolium copolymer.

[0010] In the embodiments of this application, the first and second functional groups on the coating of the separator membrane respectively include imidazole groups, which can give the coating a unique dual-channel transport mechanism, which has sites that provide electrons and sites that accept electrons, thus improving the active ion transport efficiency and the dynamic performance of the battery cell.

[0011] The reason for this is that the imidazole ring has two opposite potential types on both sides: the first and second functional groups each contain imidazole groups. This specific structure exhibits a dual-channel ion transfer mechanism. The presence of lone pairs of electrons on (-N=) is conducive to strong coordination with lithium ions, thereby promoting the dissociation of lithium ions from lithium salts. At the same time, the H atoms on (-NH-) are easily ionized, resulting in a positive potential distribution on its surface, which can form hydrogen bonds with anions in the electrolyte, effectively anchoring anion transfer. This provides a fast channel for active ions to pass through the membrane. This dual effect helps to improve the efficiency of active ion transfer.

[0012] In some alternative embodiments, the polymer additive has the chemical formula shown in formula (a) or formula (b):

[0013]

[0014] R1, R3, R5, and R6 respectively include empty, unsubstituted, or halogen-substituted C1 to C8 alkylene groups, R2 represents the first functional group, R4 represents the second functional group, and n is a positive integer.

[0015] In some optional embodiments, the weight-average molecular weight of the polymer additive is 8,000 to 80,000. When the weight-average molecular weight of the polymer additive is within this range, the polymer has a network of appropriately sized pores, resulting in a coating with a suitable network size. This improves the electronic and ion conduction pathways within the separator, facilitating the wetting of the separator in the electrolyte within the battery cell, promoting the movement of active ions, and improving the charge-discharge efficiency of the battery cell. It also reduces the probability of coating blockage or ion transport inhibition caused by high molecular weight binders in the coating.

[0016] In some optional embodiments, the swelling degree of the polymer additive after immersion at 60°C for 7 days in a mixed solvent of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 3:7 is less than or equal to 2%. The low swelling degree of the polymer additive in organic solvents results in high structural stability of the battery cell during long-term use, thereby improving the problem of decreased air permeability of the separator during use and extending the lifespan of the battery cell.

[0017] In some optional embodiments, the polymer additive includes one or more compounds of formulas (1) to (15):

[0018]

[0019] In some alternative embodiments, the coating includes fillers comprising one or more of boehmite, alumina, barium sulfate, magnesium oxide, magnesium hydroxide, silicon oxide, tin dioxide, titanium oxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, nickel oxide, hafnium dioxide, cerium oxide, zirconium titanate, barium titanate, magnesium fluoride, aluminum hydroxide, barium oxide, silicon carbide, boron carbide, aluminum nitride, silicon nitride, boron nitride, calcium fluoride, barium fluoride, magnesium aluminum silicate, lithium magnesium silicate, sodium magnesium silicate, bentonite, hydropyrite, and Pb(Zr,Ti)O3.

[0020] In some optional embodiments, the coating thickness can be 0.5 μm to 5 μm. This is beneficial for improving the transport efficiency of active ions and enhancing the kinetic performance of the battery cell.

[0021] In some optional embodiments, the areal density of the coating is 0.5 g / m². 2 ~9.5g / m 2 The dosage can be selected from 4.5 to 9.5 g / m³. 2 .

[0022] When the coating surface density is within the above range, the resistance of the separator can be kept within a suitable range, improving ion conductivity and enhancing battery performance, such as kinetic performance. When the coating surface density is within the above range, it can affect the electrolyte permeability and ion migration rate, which is beneficial to improving the kinetic performance of the battery cell.

[0023] In some optional embodiments, the ionic conductivity of the separator is from 0.457 ms / cm to 2.37 ms / cm. Therefore, the ionic conductivity of the separator is within the above range, thus improving the kinetic performance of the battery cell.

[0024] Secondly, embodiments of this application provide a separator for a battery cell, comprising:

[0025] Porous base membrane;

[0026] A coating is disposed on at least one side of a porous base membrane; the coating includes a polymer additive; the polymer additive includes a first functional group and a second functional group, the first functional group including one or more of bis(trifluoromethyl)sulfonylimino, bis(trifluoromethyl)sulfonylimino, trifluoroborate, hexafluorophosphate, sulfonic acid, hexafluoroarsenic, trifluoromethanesulfonic acid, difluorophosphate, bis(oxalate)borate, difluorooxalateborate, difluorobis(oxalate)phosphate, tetrafluorooxalate phosphate, and imidazolium; the second functional group includes one or more of quaternary ammonium ion, pyrrolyl, pyrrole, piperidinyl, pyridinyl, and imidazolium.

[0027] In an electrolyte environment, the first functional group forms a positively charged group, and the second functional group forms a negatively charged group.

[0028] In the embodiments of this application, the polymer additive in the coating of the separator contains a first functional group and a second functional group, such as polybenzimidazole (PBI), which has both electron-donating and electron-accepting sites. The first and second functional groups can form a unique dual-channel transport mechanism in the coating of the separator, providing a fast channel for active ions to pass through the separator, improving the ion conductivity of the separator, enhancing the active ion transport rate, reducing the transport resistance of active ions in the battery cell, and thus improving the fast-charging performance of the battery cell.

[0029] In addition, the first and second functional groups in the polymer additives can have a certain selectivity for the transported metal ions, reduce the ion throughput of side reactions, reduce side reactions at the negative electrode interface, and also form a denser SEI film, which improves the cycle stability of the battery cell.

[0030] Thirdly, embodiments of this application provide a method for preparing a separator for a battery cell, comprising:

[0031] A coating slurry comprising a polymer additive is provided; the polymer additive comprises a first functional group and a second functional group, the first functional group comprising one or more of the following: bis(trifluoromethyl)sulfonylimino, bis(trifluoromethyl)sulfonylimino, trifluoroborate, hexafluorophosphate, sulfonic acid, hexafluoroarsenate, trifluoromethanesulfonic acid, difluorophosphate, dioxaloateborate, difluorooxaloateborate, difluorodioxaloatephosphate, tetrafluorooxaloatephosphate, and imidazolyl; the second functional group comprises one or more of the following: quaternary ammonium ion, pyrrolyl, pyrrole, piperidinyl, pyridinyl, and imidazolyl.

[0032] The coating slurry is applied to at least one side of the porous base membrane and dried to obtain the isolation membrane.

[0033] In this embodiment, a polymer additive is added to the coating slurry. This additive contains a first functional group and a second functional group, and has both electron-donating and electron-accepting sites. The first and second functional groups can form a unique dual-channel transport mechanism in the coating of the separator, providing a fast channel for active ions to pass through the separator, improving the ion conductivity of the separator, enhancing the active ion transport rate, reducing the transport resistance of active ions in the battery cell, and thus improving the fast-charging performance of the battery cell.

[0034] In addition, the first and second functional groups in the polymer additives can have a certain selectivity for the transported metal ions, reduce the ion throughput of side reactions, reduce side reactions at the negative electrode interface, and also form a denser SEI film, which improves the cycle stability of the battery cell.

[0035] In some alternative embodiments, the coating slurry may include the fillers, binders, and optional dispersants described above. The fillers, binders, and dispersants described above have already been submitted and will not be repeated here.

[0036] Fourthly, embodiments of this application provide a battery device, comprising a battery cell as described in the first aspect, or forming a battery cell by fabricating a separator as described in the second aspect. The battery device of this application embodiment at least possesses the beneficial effects of a battery cell.

[0037] Fifthly, embodiments of this application provide an electrical device, including the battery device of the third aspect. The electrical device of this application embodiment at least has the beneficial effects of a single battery cell. Attached Figure Description

[0038] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly described below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0039] Figure 1 A schematic diagram of one embodiment of the battery cell of this application is shown.

[0040] Figure 2 It shows Figure 1 An exploded view of one embodiment of the battery cell is shown.

[0041] Figure 3 A schematic diagram of the battery pack according to one embodiment of this application is shown.

[0042] Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown.

[0043] Figure 5 A schematic diagram of one embodiment of an electrical device incorporating the battery cell of this application as a power source is shown.

[0044] The accompanying drawings are not necessarily drawn to scale. Detailed Implementation

[0045] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the battery cell, separator, preparation method thereof, battery device, and power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0046] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0047] Unless otherwise specified, all embodiments and optional embodiments of this application may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this application.

[0048] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0049] Unless otherwise specified, in this application, the term "active ion" refers to lithium ions that can be inserted and extracted back and forth between the positive and negative electrodes of a battery cell.

[0050] In this application, "multiple" refers to two or more items (including two). Similarly, "multiple types" or "several kinds" refers to two or more items (including two).

[0051] Unless otherwise stated, the test temperature for all parameters mentioned in this disclosure is 25°C.

[0052] The battery device mentioned in the embodiments of this disclosure may include one or more battery modules for providing voltage and capacity. The battery module may include multiple battery cells connected in series, parallel, or mixed connections via a busbar.

[0053] In some alternative embodiments, a battery cell assembly is typically formed by arranging multiple battery cells; as an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells into a single module. As an example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0054] In some alternative embodiments, the battery device can be a battery pack, comprising a housing and one or more battery cell assemblies housed within the housing. As an example, the battery cell assembly can be a battery module, which can be housed within the housing by securing the battery module to the housing. Alternatively, the battery cell assembly can be housed within the housing by directly securing multiple battery cells to the housing.

[0055] A single battery cell is the smallest unit that makes up a battery device, and it can independently perform the functions of charging and discharging. A single battery cell can be cylindrical, cuboid, or other shapes, and the embodiments disclosed herein are not limited to this. Figure 1 The example shown is a rectangular battery cell 5.

[0056] In some embodiments, individual battery cells can be assembled into a battery module, and the number of individual battery cells contained in the battery module can be multiple, the specific number of which can be adjusted according to the application and capacity of the battery module. Figure 2 This is a schematic diagram of battery module 4 as an example. Figure 2 As shown, in battery module 4, multiple battery cells 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple battery cells 5 can be fixed in place using fasteners.

[0057] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0058] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0059] Figure 3 and Figure 4 This is a schematic diagram of battery pack 1 as an example. Figure 3 and Figure 4 As shown, the battery pack 1 may include a housing and multiple battery modules 4 disposed within the housing. The housing includes an upper housing 2 and a lower housing 3. The upper housing 2 covers the lower housing 3, forming a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the housing.

[0060] In some embodiments, the battery device may be an energy storage device. Energy storage devices include energy storage containers, energy storage cabinets, etc.

[0061] In this embodiment of the application, the battery cell can be a secondary battery, which refers to a battery cell that can be recharged to activate the active materials and continue to be used after the battery cell has been discharged.

[0062] The battery cells provided in the embodiments of this disclosure may include, but are not limited to, lithium battery cells and sodium battery cells. Lithium battery cells may be lithium-ion battery cells, lithium metal battery cells, etc. Sodium battery cells may be sodium-ion battery cells, sodium metal battery cells, etc.

[0063] The battery cell can also be a sodium lithium-ion battery cell, a lithium sulfur battery cell, a magnesium ion battery cell, a nickel-metal hydride battery cell, a nickel-cadmium battery cell, a lead-acid battery cell, etc., but the embodiments of this application are not limited to this.

[0064] The battery cell may also include an outer packaging, which can be used to encapsulate the electrode assembly. The outer packaging can be a rigid shell, such as a hard plastic shell, aluminum shell, or steel shell. The outer packaging can also be a flexible package, such as a pouch-type flexible package. The material of the flexible package can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0065] The battery cell includes an electrode assembly. The electrode assembly can be a wound structure or a stacked structure, and the embodiments of this application are not limited to this.

[0066] The electrode assembly includes a positive electrode, a negative electrode, and a separator, with the separator located between the positive and negative electrode.

[0067] The separator is positioned between the positive and negative electrodes, primarily serving to prevent short circuits between the positive and negative electrodes. This application does not impose any particular restriction on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0068] The separator is a crucial component that supports the charging and discharging electrochemical processes of individual battery cells. Commonly used separators are mostly polyolefin films; however, polyolefin films have poor heat resistance and are prone to softening or melting at high temperatures, which can lead to short circuits in the battery cells. To improve the heat resistance of the separator, a coating is usually applied to it.

[0069] In related technologies, the fast charging performance of battery cells is usually achieved by reducing the thickness of the electrode sheets or reducing the compaction, but this technology has certain limitations.

[0070] Based on this, the present disclosure provides a battery cell that enables the battery cell to have better fast charging performance.

[0071] In a first aspect, embodiments of this application provide a battery cell, including: a separator and an electrolyte.

[0072] In some optional embodiments, the separator includes: a porous base membrane; a coating disposed on at least one side of the porous base membrane, the coating including a polymer additive, the polymer additive including a first functional group and a second functional group, the first functional group including one or more of bis(trifluoromethyl)sulfonylimino, bis(trifluoromethyl)sulfonylimino, trifluoroborate, hexafluorophosphate, sulfonic acid, hexafluoroarsenate, trifluoromethanesulfonic acid, difluorophosphate, bis(oxalate)borate, difluorooxalateborate, difluorobis(oxalate)phosphate, tetrafluorooxalate phosphate, and imidazole, the second functional group including one or more of quaternary ammonium ion, pyrrolyl, pyrrole, piperidinyl, pyridinyl, and imidazole; in an electrolyte environment, the first functional group forms a positively charged group, and the second functional group forms a negatively charged group.

[0073] In the embodiments of this application, the polymer additive in the coating of the separator contains a first functional group and a second functional group, which have both electron-donating sites and electron-accepting sites. The first functional group and the second functional group can form a unique dual-channel transport mechanism in the coating of the separator, providing a fast channel for active ions to pass through the separator, improving the ion conductivity of the separator, enhancing the transport speed of active ions, reducing the transport resistance of active ions in the battery cell, and thus improving the fast charging performance of the battery cell.

[0074] In addition, the first and second functional groups in the polymer additives can have a certain selectivity for the transported metal ions, reduce the ion throughput of side reactions, reduce side reactions at the negative electrode interface, and also form a denser SEI film, which improves the cycle stability of the battery cell.

[0075] As an example, polymer additives containing first and second functional groups can improve the transport rate of Na ions.

[0076] In some alternative embodiments, the coating includes a polymer additive at a mass content of 0.1% to 10%, optionally 3% to 8%, based on the total mass of the coating.

[0077] Optionally, the mass content of the polymer additive in the coating can be any value or range thereof from 0.1%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, 6.0%, 6.5%, 7.0%, 7.5%, 8.0%, 8.5%, 9.0%, 9.5%, and 10.0%.

[0078] When the mass content of polymer additives in the coating is within the above range, the polymer additives can achieve good adhesion with other components in the coating and the porous base film, enabling the battery cell to have both good fast charging performance and high energy density.

[0079] In some alternative embodiments, the first functional group and the second functional group respectively include an imidazole group, and the polymer additive includes one or more of polybenzimidazole, polyvinylimidazolium, polyacetylimidazole and N-vinylimidazolium copolymer.

[0080] In the embodiments of this application, the first and second functional groups on the coating of the separator membrane respectively include imidazole groups, which can give the coating a unique dual-channel transport mechanism, which has sites that provide electrons and sites that accept electrons, thus improving the active ion transport efficiency and the dynamic performance of the battery cell.

[0081] It is understandable that: Polyvinylimidazole: obtained by polymerization of vinylimidazolium monomers, it has an imidazole ring structure with nitrogen atoms, and can form hydrogen bonds or coordinate bonds with other molecules. Polyacrylimidazole: obtained by polymerization of acetylimidazolium monomers, usually prepared by polymerization of acryloylimidazolium. N-vinylimidazole copolymer: N-vinylimidazole can be copolymerized with other vinyl monomers (such as styrene, acrylic acid, etc.), and the resulting copolymer combines the characteristics of the imidazole ring with the functional properties of the comonomer.

[0082] Taking the example of imidazole groups as the first and second functional groups, the reason for this analysis is that there are two opposite potential types on both sides of the imidazole ring: the (-NH-) group has a positive potential, and the (-N=) group has a negative potential. This is mainly because the N atom in the double bond of the imidazole ring is sp2 hybridized, while the N atom in the single bond is sp3 hybridized. The N atom in the double bond has lone pairs of electrons that are coplanar with the ring and do not participate in conjugation, thus exhibiting a high electron cloud density, indicating electronegativity and promoting the formation of coordinate bonds with metals. The N atom does not contain lone pairs of electrons and has a low electron cloud density, which makes the H atom easier to ionize and create a positively charged environment around the NH bond. The increased active ion transport rate is mainly due to strong electrostatic interaction.

[0083] As an example, the first and second functional groups each include an imidazole group, which has two opposite potential types on both sides: the (-NH-) group has a positive potential, and the (-N=) group has a negative potential. This is mainly because the N atom in the double bond of the imidazole ring is sp2 hybridized, while the N atom in the single bond is sp3 hybridized. This specific structure exhibits a dual-channel ion transfer mechanism. The presence of lone pairs of electrons on (-N=) is conducive to strong coordination with lithium ions, thereby promoting the dissociation of lithium ions from lithium salts. At the same time, the H atoms on (-NH-) are easily ionized, resulting in a positive potential distribution on its surface, which can form hydrogen bonds with anions in the electrolyte, effectively anchoring anion transfer. This provides a fast channel for active ions to pass through the membrane, and this dual effect helps to improve the efficiency of active ion transfer.

[0084] The components and their contents in the separator membrane can be determined using methods conventional in the art. For example, they can be detected using gas chromatography-mass spectrometry (GC-MS), ion chromatography (IC), liquid chromatography (LC), inductively coupled plasma optical emission spectrometry (ICP-OES), infrared spectroscopy, Raman spectroscopy, and nuclear magnetic resonance. For instance, infrared spectroscopy can be used to identify compounds in the electrolyte, such as the characteristic peaks of sulfur-oxygen double bonds in sulfoxide compounds at 3200-3400 cm⁻¹. -11 or 1600-1700cm -1 Within the specified range, high-resolution gas chromatography-high-resolution mass spectrometry (HPLC-MS) can separate different components in the electrolyte and obtain high-precision molecular weights, thereby determining the atomic composition; then, the specific molecular structure of each component can be confirmed by nuclear magnetic resonance (NMR) spectroscopy results.

[0085] In some alternative embodiments, the polymer additive has the chemical formula shown in formula (a) or formula (b):

[0086]

[0087] R1, R3, R5, and R6 respectively include empty, unsubstituted, or halogen-substituted C1 to C8 alkylene groups, R2 represents the first functional group, R4 represents the second functional group, and n is a positive integer.

[0088] An empty group can be understood as an adjacent group being connected. For example, R1 is empty and R2 is directly connected to a carbon atom; R1, R3, and R5 are empty and R2 is directly connected to R4.

[0089] In some optional embodiments, the weight-average molecular weight of the polymer additive is 8,000 to 80,000.

[0090] Optionally, the weight-average molecular weight of the polymer additive can be any value or a range of combinations thereof from 8000, 8500, 9000, 9500, 10000, 10500, 11000, 11500, 12000, 12500, 13000, 13500, 14000, 14500, 15000, 20000, 30000, 40000, 50000, 60000, 70000, and 80000.

[0091] When the weight-average molecular weight of the polymer additive is within the aforementioned range, the polymer possesses a network with appropriately sized pores, resulting in a coating with a suitable network size. This improves the electronic and ion conduction pathways within the separator, facilitating the wetting of the separator in the electrolyte within the battery cell, promoting the movement of active ions, and enhancing the charge-discharge efficiency of the battery cell. The weight-average molecular weight of the polymer additive also reduces the probability of coating blockage or ion transport inhibition caused by high-molecular-weight binders in the coating.

[0092] The weight-average molecular weight of polymers has a meaning known in the art and can be determined using instruments and methods known in the art, such as high-temperature gel permeation chromatography. The test can be performed using a gel permeation chromatography (GPC) instrument, such as the Polymer Char GPC-IR high-temperature gel permeation chromatograph. The test can be referenced to the international standard ISO 16014-1-2019.

[0093] In some optional embodiments, the swelling degree of the polymer additive after immersion at 60°C for 7 days in a mixed solvent of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 3:7 is less than or equal to 2%. The low swelling degree of the polymer additive in organic solvents results in high structural stability of the battery cell during long-term use, thereby improving the problem of decreased air permeability of the separator during use and extending the lifespan of the battery cell. As an example, the swelling degree of the polymer additive can be 0.1%, 0.5%, 1%, 1.5%, etc.

[0094] Polymer additives can be understood as organic particles. The swelling degree of polymer additives can be tested as follows: Take an appropriate amount of sample (e.g., about 1g), denoted as m1, and place it in a semi-permeable membrane sample bag. Seal the bag; the sample bag should be permeable to the mixed solvent but not to the sample. Immerse the sample bag in an appropriate amount of solvent (e.g., about 50g) at 60°C for 7 days. After immersion, remove the sample bag and the sample from the bag. Wipe away excess solvent and weigh the sample again, m2. Swelling degree = (m2-m1) / m1 × 100%. The mixed solvent is a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7.

[0095] In some optional embodiments, the polymer additive includes one or more compounds of formulas (1) to (15):

[0096]

[0097]

[0098] In some optional embodiments, the coating includes fillers comprising one or more of boehmite, alumina, barium sulfate, magnesium oxide, magnesium hydroxide, silicon oxides, tin dioxide, titanium oxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, nickel oxide, hafnium dioxide, cerium oxide, zirconium titanate, barium titanate, magnesium fluoride, aluminum hydroxide, barium oxide, silicon carbide, boron carbide, aluminum nitride, silicon nitride, boron nitride, calcium fluoride, barium fluoride, magnesium aluminum silicate, lithium magnesium silicate, sodium magnesium silicate, bentonite, hydropyrite, and Pb(Zr,Ti)O3. The fillers of the above types can be obtained through chemical modification and / or physical modification.

[0099] In some alternative embodiments, the coating includes an adhesive, which may include, but is not limited to, one or more of polyacrylate adhesives, nitrile rubber adhesives, polyacrylic acid, polymethacrylic acid, sodium polyacrylate, polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0100] In some optional embodiments, the binder content in the coating, based on the total mass of the coating, can be 0.5%-10%, for example, it can be 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, or any range of the above values. Optionally, the binder content in the coating can be 1%-8% by mass.

[0101] In some alternative embodiments, the coating may also include a dispersant, such as one or more of the following: alkylphenol polyoxyethylene ethers, polyacrylic acid dispersants, and cellulose dispersants. As an example, the dispersant may include, but is not limited to, sodium carboxymethyl cellulose, sodium polyacrylate, and ammonium polyacrylate.

[0102] In some optional embodiments, the coating thickness can be 0.5 μm-5 μm. The coating thickness refers to the thickness of the coating on one side of the porous base film. Optionally, the coating thickness can be 0.5 μm-4 μm, 0.5 μm-3 μm, 0.5 μm-2 μm, 0.8 μm-4 μm, 0.8 μm-3 μm, 0.8 μm-2 μm, 1 μm-3 μm, etc. This is beneficial for improving the transport efficiency of active ions and enhancing the kinetic performance of the battery cell.

[0103] In some optional embodiments, the thickness of the separator can be 5μm-14μm, optionally 5μm-7μm or 6μm-12μm.

[0104] In some optional embodiments, the areal density of the coating is 0.5 g / m². 2 ~9.5g / m 2 The dosage can be selected from 4.5 to 9.5 g / m³. 2 .

[0105] Optionally, the areal density of the coating can be 0.5 g / m³. 2 1.0g / m 2 1.5g / m 2 2.0g / m 2 2.5g / m 2 3.0g / m 2 3.5g / m 2 4.0g / m 2 4.5g / m 2 5.0g / m 2 5.5g / m 2 6.0g / m 2 6.5g / m 2 7.0g / m 27.5g / m 2 8.0g / m 2 8.5g / m 2 9.0g / m 2 9.5g / m 2 Any value in or a range thereof.

[0106] When the coating surface density is within the above range, the resistance of the separator can be kept within a suitable range, improving ion conductivity and enhancing battery performance, such as kinetic performance. When the coating surface density is within the above range, it can affect the electrolyte permeability and ion migration rate, which is beneficial to improving the kinetic performance of the battery cell.

[0107] In some alternative embodiments, the ionic conductivity of the separator is from 0.457 ms / cm to 2.37 ms / cm.

[0108] Optionally, the ionic conductivity of the separator is 0.457 ms / cm, 0.50 ms / cm, 0.55 ms / cm, 0.60 ms / cm, 0.65 ms / cm, 0.70 ms / cm, 0.75 ms / cm, 0.80 ms / cm, 0.85 ms / cm, 0.90 ms / cm, 0.95 ms / cm, 1.00 ms / cm, 1.05 ms / cm, 1.10 ms / cm, 1.15 ms / cm, 1.20 ms / cm, 1.25 ms / cm, 1.30 ms / cm, 1.35 ms / cm, and 1.40 ms / cm. The ionic conductivity of the separator is within any value or a range of combinations thereof, from 1.45 ms / cm, 1.50 ms / cm, 1.55 ms / cm, 1.60 ms / cm, 1.65 ms / cm, 1.70 ms / cm, 1.75 ms / cm, 1.80 ms / cm, 1.85 ms / cm, 1.90 ms / cm, 1.95 ms / cm, 2.00 ms / cm, 2.05 ms / cm, 2.10 ms / cm, 2.15 ms / cm, 2.20 ms / cm, 2.25 ms / cm, 2.30 ms / cm, 2.35 ms / cm, and 2.37 ms / cm. The ionic conductivity of the separator within this range improves the kinetic performance of the battery cell.

[0109] In some optional embodiments, the porous base membrane may comprise a membrane or nonwoven fabric selected from any one or at least two of the following: polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene ether, cyclic olefin copolymer, polyphenylene sulfide, and polyvinylidene naphthalene. In some optional embodiments, the porous base membrane may further comprise one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film.

[0110] Porous base membranes can be single-layer thin films or multi-layer composite thin films. When a porous base membrane is a multi-layer composite thin film, the materials of each layer can be the same or different.

[0111] In some optional embodiments, the thickness of the porous base film can be 4μm-12μm, optionally 4μm-9μm.

[0112] In some optional embodiments, the porosity of the porous base membrane can be 25%-60%, optionally 28%-50%. The porosity of the base membrane is defined in a way known in the art and can be tested using instruments and methods known in the art. An exemplary testing method is as follows: Take five 100mm × 100mm base membrane samples, measure their weights, and take the average as the base membrane weight M (mg). Calculate the porosity X of the base membrane using the formula X = [1-M / (T×S×ρ)]×100%, where T is the thickness of the base membrane, S is the area of ​​the base membrane, and ρ is the density of the polymer in the base membrane formulation.

[0113] In some optional embodiments, the porosity of the separator is 25% to 40%, optionally 27% to 34.5%. A porosity within this range allows for the passage of more active ions, which can improve the cycle capacity retention of the battery cells.

[0114] The porosity of the separator can be measured using methods known in the art, such as the liquid adsorption method and the gas adsorption method. For example, it can be measured using an AccuPyc II 1340 true density meter. The specific testing method involves measuring the total volume V1 and the actual volume V2 of the separator, and then using the formula: Porosity = (V1 - V2) / V1 × 100%, the porosity of the separator can be obtained.

[0115] [Preparation method of the separating membrane]

[0116] This application provides a method for preparing a separator for a battery cell, comprising:

[0117] A coating slurry comprising a polymer additive is provided; the polymer additive comprises a first functional group and a second functional group, the first functional group comprising one or more of the following: bis(trifluoromethyl)sulfonylimino, bis(trifluoromethyl)sulfonylimino, trifluoroborate, hexafluorophosphate, sulfonic acid, hexafluoroarsenate, trifluoromethanesulfonic acid, difluorophosphate, dioxaloateborate, difluorooxaloateborate, difluorodioxaloatephosphate, tetrafluorooxaloatephosphate, and imidazolyl; the second functional group comprises one or more of the following: quaternary ammonium ion, pyrrolyl, pyrrole, piperidinyl, pyridinyl, and imidazolyl.

[0118] The coating slurry is applied to at least one side of the porous base membrane and dried to obtain the isolation membrane.

[0119] In this embodiment, a polymer additive containing a first functional group and a second functional group is added to the coating slurry. This additive has both electron-donating and electron-accepting sites. The first and second functional groups can form a unique dual-channel transport mechanism in the separator coating, providing a rapid channel for active ions to pass through the separator, improving the ion conductivity of the separator, enhancing the active ion transport rate, and reducing the transport resistance of active ions in the battery cell, thereby improving the fast-charging performance of the battery cell. In some optional embodiments, the coating slurry may include the filler, binder, and optionally a dispersant as described above. The filler, binder, and dispersant have already been submitted and will not be elaborated upon here.

[0120] [Positive electrode plate]

[0121] In some alternative embodiments, the positive electrode can be a positive electrode sheet, which may include a positive current collector and a positive active material disposed on at least one surface of the positive current collector.

[0122] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material is disposed on either or both of the two opposite surfaces of the positive current collector.

[0123] As an example, the positive current collector can be a metal foil, a conductive polymer material, a carbon material, or a composite current collector. For example, as a metal foil, pure metals, alloys, or surface-treated metals can be used, including but not limited to stainless steel, copper, aluminum, nickel, titanium, or silver. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0124] As an example, the positive electrode active material may include at least one of the following materials: lithium phosphate, lithium transition metal oxide, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium phosphate include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0125] Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.8 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Modified compounds refer to substances obtained by modification methods such as doping or coating based on the above-mentioned substances.

[0126] When the battery cell is a sodium-ion battery cell or a sodium metal battery cell, the positive electrode active material may include, but is not limited to, one or more of the following: sodium-containing transition metal oxides, polyanionic materials (such as phosphates, fluorophosphates, pyrophosphates, sulfates, etc.), and Prussian blue materials.

[0127] As an example, positive electrode active materials may include NaFeO2, NaCoO2, NaCrO2, NaMnO2, NaNiO2, and NaNi 1 / 2Ti 1 / 2 O2, NaNi 1 / 2 Mn 1 / 2 O2, Na 2 / 3 Fe 1 / 3 Mn 2 / 3 O2, NaNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, NaFePO4, NaMnPO4, NaCoPO4, Prussian blue materials and materials with the general formula X p M' q (PO4) r O x Y 3-x One or more of the materials. In general formula X p M' q (PO4) r O x Y 3-x In the given condition, 0 < p ≤ 4, 0 < q ≤ 2, 1 ≤ r ≤ 3, 0 ≤ x ≤ 2, and X includes elements selected from H. + Li + Na + K + and NH4 + One or more of the following, M' is a transition metal cation, which may be selected from one or more of V, Ti, Mn, Fe, Co, Ni, Cu and Zn, and Y is a halide anion, which may be selected from one or more of F, Cl and Br.

[0128] The modified compounds for the above-mentioned positive electrode active materials can be obtained by doping and / or surface coating of the positive electrode active materials.

[0129] During the charging and discharging process, battery cells undergo Li or Na insertion / extraction and consumption, resulting in varying molar contents of Li or Na at different discharge states. In the examples of positive electrode active materials in this disclosure, the molar contents of Li or Na represent the initial state of the material, i.e., the state before material addition. After charge-discharge cycles, the molar contents of Li or Na will change when the positive electrode active material is applied to the battery cell. Similarly, the molar contents of oxygen (O) in the examples of positive electrode active materials in this disclosure are only theoretical values. Lattice oxygen release will cause changes in the molar contents of O, and the actual molar contents of O will also fluctuate.

[0130] In some alternative embodiments, the positive electrode can be a foamed metal. The foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloy, or foamed carbon, etc. When foamed metal is used as the positive electrode, the surface of the foamed metal may or may not contain a positive electrode active material. As an example, a positive electrode active material is filled and / or deposited within the foamed metal.

[0131] The positive electrode active material film layer is typically formed by coating a positive electrode slurry onto a positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is usually formed by dispersing positive electrode active material particles, optional conductive agents, optional binders, and any other components in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP), but is not limited to it.

[0132] As an example, based on the total mass of the positive electrode active material, conductive agent, and binder, the total amount of binder added is preferably 1wt% to 2.5wt%, for example, 1wt%, 1.5wt%, 2wt%, and 2.5wt%. If the amount of polymer or binder added is too low, insufficient binder will not be able to support the strength of the positive electrode active material film layer, thus failing to meet the requirements of rolling and thinning. If the amount of binder added is too high, it will cause the positive electrode active material film layer to have high viscosity, making it easy for the film to stick to the rollers during the rolling process, making it impossible to perform thinning and current collector bonding.

[0133] [Negative electrode plate]

[0134] The specific composition and structure of the negative electrode sheet can be selected according to the type of battery cell, and the embodiments of this application are not limited in this regard.

[0135] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector and comprising a negative electrode active material. For example, the negative current collector has two surfaces opposite each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative current collector.

[0136] The negative electrode active material is a material capable of extracting and inserting active ions, and can be any material known in the art. As examples, negative electrode active materials include, but are not limited to, one or more of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. Silicon-based materials may include one or more of elemental silicon, silicon oxide, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more of elemental tin, tin oxide, and tin alloys. This application is not limited to these materials, and other conventionally known materials that can be used as negative electrode active materials may also be used.

[0137] In some optional embodiments, the negative electrode film layer may also optionally include a negative electrode conductive agent. This application does not impose any particular limitation on the type of negative electrode conductive agent; as an example, the negative electrode conductive agent may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0138] In some optional embodiments, the negative electrode film layer may also optionally include a negative electrode binder. This application does not impose any particular limitation on the type of negative electrode binder. As an example, the negative electrode binder may include one or more of the following: styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0139] In some alternative embodiments, the negative electrode film layer may also optionally include other additives. As an example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc.

[0140] In some alternative embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, copper foil may be used. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. As an example, the metal material may include one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymer substrate may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0141] The negative electrode film is typically formed by coating a negative electrode slurry onto a negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry is usually formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional additives in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to these.

[0142] The negative electrode sheet does not exclude other additional functional layers besides the negative electrode film layer. For example, in some optional embodiments, the negative electrode sheet of this application may also include a conductive undercoat layer (e.g., composed of a conductive agent and an adhesive) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector; in some optional embodiments, the negative electrode sheet of this application may also include a protective layer covering the surface of the negative electrode film layer.

[0143] When the battery cell is a lithium metal battery cell, the negative electrode sheet may not include a negative electrode active material capable of extracting and embedding active ions. For example, in some optional embodiments, the negative electrode sheet may include a lithium sheet or a lithium alloy sheet; in other embodiments, the negative electrode sheet includes a mesh or foam-like three-dimensional framework layer, such as foamed copper (or copper alloy), foamed nickel (or nickel alloy), foamed aluminum (or aluminum alloy), copper (or copper alloy) mesh, nickel (or nickel alloy) mesh, aluminum (or aluminum alloy) mesh, etc.

[0144] Electrolyte

[0145] In some embodiments, the battery cell includes an electrolyte. The electrolyte acts as a conductor of active ions between the positive and negative electrodes. This application does not impose specific limitations on the type of electrolyte; it can be selected according to requirements.

[0146] In some alternative embodiments, the electrolyte comprises an electrolyte salt and a solvent.

[0147] There are no specific restrictions on the types of electrolyte salts; they can be selected according to actual needs.

[0148] In some alternative embodiments, the electrolyte salt includes one or more selected from lithium salts for lithium-ion batteries and sodium salts for sodium-ion batteries.

[0149] As an example, lithium salts include one or more selected from lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0150] As an example, sodium salts include one or more selected from NaPF6, NaClO4, NaBCl4, NaSO3CF3, and Na(CH3)C6H4SO3.

[0151] The type of solvent is not specifically limited and can be selected according to actual needs. As an example, the solvent may include one or more selected from ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0152] In some optional embodiments, the electrolyte may also include polymer additives. For example, the polymer additives may include negative electrode film-forming polymer additives, positive electrode film-forming polymer additives, and polymer additives that can improve certain battery performance, such as polymer additives that improve battery overcharge performance, polymer additives that improve battery high-temperature performance, and polymer additives that improve battery low-temperature power performance.

[0153] In some alternative embodiments, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0154] In some alternative embodiments, the outer packaging of the battery cell can be a rigid shell, such as a hard plastic shell, aluminum shell, steel shell, etc. The outer packaging of the battery cell can also be a flexible package, such as a pouch. The material of the flexible package can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), etc.

[0155] [Preparation Method]

[0156] The method for preparing the battery cell of this application is well known. In some optional embodiments, a positive electrode, a separator, a negative electrode, and an electrolyte can be assembled to form a battery cell. As an example, the positive electrode, separator, and negative electrode can be formed into an electrode assembly through a winding process and / or a stacking process. The electrode assembly is placed in an outer packaging, dried, and then injected with electrolyte. After encapsulation, settling, formation, and shaping processes, a battery cell is obtained.

[0157] Electrical appliances

[0158] This application provides an electrical device, including the battery device described above.

[0159] A single battery cell can be used as a power source for an electrical device or as an energy storage unit for that device. Electrical devices can be, but are not limited to, mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0160] Figure 5 This is a schematic diagram of an example electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the device's requirements for high power and high energy density, a battery pack or battery module can be used.

[0161] Another example of an electrical device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0162] Example

[0163] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0164] Example 1

[0165] Preparation of the separating membrane: Polybenzimidazole with a weight average molecular weight of 10,000, ceramic particles, and polyacrylate binder were mixed in a mass ratio of 10:80:10, and N-methylpyrrolidone was added to prepare a coating slurry with a solid content of 40 wt%. The ceramic particles were boehmite.

[0166] Using a 10 μm thick polyethylene film as a porous base membrane, a coating slurry was applied to both sides of the porous base membrane. After drying, a separator membrane with a coating thickness of 5 μm on either side was obtained, and the areal density of the coating on one side was 0.7 g / m². 2 .

[0167] Preparation of lithium battery cells:

[0168] Preparation of the positive electrode sheet: Lithium iron phosphate: conductive carbon black: polyvinylidene fluoride (PVDF) = 8:1:1 were mixed according to the mass ratio, and then the solvent N-methylpyrrolidone was added to prepare a positive electrode slurry. The solid content of the positive electrode slurry was 53 wt%. The positive electrode slurry was coated on both sides of an aluminum foil with a thickness of 15 μm, and after drying, a positive electrode coating with a thickness of 120 μm was obtained, thus preparing the positive electrode sheet.

[0169] Negative electrode sheet: Artificial graphite, conductive carbon black, binder carboxymethyl cellulose (CMC) and solvent water were uniformly mixed according to the weight ratio of 95:2:3:100 to obtain a negative electrode slurry. The negative electrode slurry was uniformly coated on both sides of a copper foil with a thickness of 13 μm at a coating density of 13.6 mg / cm 2 ; then, after drying, cold pressing and slitting, the negative electrode sheet of Example 1 was obtained.

[0170] Electrolyte: Ethylene carbonate, diethyl carbonate, and dimethyl carbonate were mixed in a volume ratio of 1:1:1, and LiPF6 was dissolved in the above solution to obtain an electrolyte. In this electrolyte, the concentration of LiPF6 was 1 mol / L

[0171] Assembly: Using the separator prepared above, it was placed in the order of "separator - positive electrode sheet - separator - negative electrode sheet - separator", and the winding shaft was rotated by a motor to wind the positive electrode sheet, negative electrode sheet and separator to obtain a wound bare battery cell. The bare battery cell was placed in an outer package, the above electrolyte was injected and sealed to obtain a lithium-ion battery assembled.

[0172] Examples 2 to 5

[0173] The differences between Examples 2 to 5 and Example 1 were that the added mass of the polymer additive was different, as shown in Table 1.

[0174] Examples 6 to 8

[0175] The differences between Examples 6 to 8 and Example 1 were that the weight-average molecular weight of the polymer additive was different, as shown in Table 1.

[0176] Examples 9 to 14

[0177] The differences between Examples 9 to 14 and Example 1 were that the types of the polymer additive were different, as shown in Table 1.

[0178] Comparative Example 1

[0179] The difference between this comparative example and Example 1 was that the above polybenzimidazole was not added, and the coating was composed of polyacrylate and boehmite, and the mass ratio of polyacrylate to boehmite in the coating was 10:80.

[0180] Test section

[0181] The specific test methods for electrochemical performance testing of the lithium battery cells prepared in the examples and comparative examples are as follows.

[0182] 1) Fast charging performance of individual battery cells at 25℃: At 25℃, a three-electrode cell was fabricated by inserting copper wire into the cell. First, lithium plating was performed using the positive electrode (copper wire) at 20uA for 2 hours and the negative electrode (copper wire) at 20uA for 2 hours as reference electrodes to detect the negative electrode potential. Then, the cell was fully charged at 1 / 3C, allowed to stand for 60 minutes, and then discharged at 1 / 3C to 10% SOC. The cell was then charged at 3C, 2C, 1C, 0.5C, 0.2C, 0.1C, and 0.05C respectively. When the negative electrode potential reached 0V, the cell was disassembled, and the negative electrode interface was observed. The maximum fast charging rate was determined by combining the negative electrode potential and the interface condition. After fully charging the battery cell, discharge it to 90% SOC at 1 / 3C. Then charge the battery cell at 3C, 2C, 1C, 0.5C, 0.2C, 0.1C, and 0.05C respectively. When the negative electrode potential reaches 0V, disassemble the battery cell and observe the negative electrode interface. Determine the maximum fast charging rate by combining the negative electrode potential and the interface condition.

[0183] 2) Battery cell capacity retention test at 25℃:

[0184] The lithium-ion battery prepared above was subjected to 500 cycles of charge and discharge at a 1C charge-discharge rate using the Shenzhen Xinwei Battery Testing System. The test temperature was 25.0℃ and the charge-discharge voltage was 2.0V-3.7V. The capacity retention rate was obtained by dividing the discharge capacity of the last 500 cycles by the discharge capacity of the first cycle.

[0185] The test results of the examples and comparative examples are shown in Table 1.

[0186] Table 1

[0187]

[0188]

[0189] As can be seen from the test results in Table 1, compared with Comparative Example 1, the addition of different types and amounts of polymer additives in Examples 1-15 significantly improved the rate capability and cycle capacity retention of the battery cells. The reason for this is that the first and second functional groups in the polymer additives can form a unique dual-channel transport mechanism in the separator coating, providing a rapid channel for active ions to pass through the separator, improving the ion conductivity of the separator, and thus enhancing the fast-charging performance of the battery cells. The first and second functional groups in the polymer additives can also exhibit a certain selectivity for the transported metal ions, reducing the permeability of ions involved in side reactions and minimizing side reactions at the negative electrode interface; they also form a denser SEI film, improving the cycle stability of the battery cells.

[0190] Examples 1-5 show that different amounts of polybenzimidazole were added, ranging from 3% to 8%, and the rate performance and cycle capacity stability of the battery cells were significantly better than those with other added amounts.

[0191] Compared with Example 1, Examples 6-8 added polybenzimidazole with different weight-average molecular weights. The weight-average molecular weight of polybenzimidazole affects the performance of the monolayer monomer. The performance of the battery cell containing polybenzimidazole with a weight-average molecular weight of 8,000 to 15,000 is significantly better than that of other weight-average molecular weights.

[0192] Compared with Example 1, Examples 9-14 added different types of polymer additives with different types of first and second functional groups, which also affected the rate capability and cycle capacity stability of the battery cells.

[0193] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A battery cell, characterized in that, include: A separator and an electrolyte, wherein the separator comprises: Porous base membrane; A coating is disposed on at least one side of the porous base membrane. The coating includes a polymer additive, which includes a first functional group and a second functional group. The first functional group includes one or more of the following: bis(trifluoromethyl)sulfonylimino, bis(trifluoromethyl)sulfonylimino, trifluoroborate, hexafluorophosphate, sulfonic acid, hexafluoroarsenic, trifluoromethanesulfonic acid, difluorophosphate, bis(oxalate)borate, difluorooxalateborate, difluorobis(oxalate)phosphate, tetrafluorooxalate phosphate, and imidazole. The second functional group includes one or more of the following: quaternary ammonium ion, pyrrolyl, pyrrole, piperidinyl, pyridinyl, and imidazole. In an electrolyte environment, the first functional group forms a positively charged group, and the second functional group forms a negatively charged group.

2. The battery cell according to claim 1, characterized in that, Based on the total mass of the coating, the coating comprises a polymer additive at a mass content of 0.1% to 10%.

3. The battery cell according to claim 1 or 2, characterized in that, Based on the total mass of the coating, the coating includes a polymer additive at a mass content of 3% to 8%.

4. The battery cell according to any one of claims 1 to 3, characterized in that, The first functional group and the second functional group each include an imidazole group, and the polymer additive includes one or more of polybenzimidazole, polyvinylimidazolium, polyacetylimidazole and N-vinylimidazolium copolymer.

5. The battery cell according to any one of claims 1 to 4, characterized in that, The chemical formula of the polymer additive is shown in formula (a) or formula (b): R1, R3, R5, and R6 respectively include empty, unsubstituted, or halogen-substituted C1 to C8 alkylene groups, R2 represents the first functional group, R4 represents the second functional group, and n is a positive integer.

6. The battery cell according to any one of claims 1 to 5, characterized in that, The polymer additive has a weight-average molecular weight of 8000–80000; and / or, The swelling degree of the polymer additive after being immersed in a mixed solvent of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 3:7 at 60°C for 7 days is less than or equal to 2%.

7. The battery cell according to any one of claims 1 to 6, characterized in that, The polymer additive comprises one or more compounds of formula (1) to formula (15):

8. The battery cell according to any one of claims 1 to 7, characterized in that, The coating includes fillers comprising one or more of boehmite, alumina, barium sulfate, magnesium oxide, magnesium hydroxide, silicon oxide, tin dioxide, titanium oxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, nickel oxide, hafnium dioxide, cerium oxide, zirconium titanate, barium titanate, magnesium fluoride, aluminum hydroxide, barium oxide, silicon carbide, boron carbide, aluminum nitride, silicon nitride, boron nitride, calcium fluoride, barium fluoride, magnesium aluminum silicate, lithium magnesium silicate, sodium magnesium silicate, bentonite, hydropyrite, and Pb(Zr,Ti)O3.

9. The battery cell according to any one of claims 1 to 8, characterized in that, The coating satisfies one or more of the following conditions: 1) The thickness of the coating is 0.5μm to 5μm; 2) The areal density of the coating is 0.5 g / m³. 2 ~9.5g / m 2 .

10. The battery cell according to any one of claims 1 to 9, characterized in that, The ionic conductivity of the isolation membrane ranges from 0.457 ms / cm to 2.37 ms / cm.

11. A separator for a battery cell, comprising: Porous base membrane; A coating is disposed on at least one side of the porous base membrane; the coating includes a polymer additive; the polymer additive includes a first functional group and a second functional group, the first functional group including one or more of bis(trifluoromethyl)sulfonylimino, bis(trifluoromethyl)sulfonylimino, trifluoroborate, hexafluorophosphate, sulfonic acid, hexafluoroarsenate, trifluoromethanesulfonic acid, difluorophosphate, bis(oxalate)borate, difluorooxalateborate, difluorobis(oxalate)phosphate, tetrafluorooxalate phosphate, and imidazole; the second functional group includes one or more of quaternary ammonium ion, pyrrolyl, pyrrole, piperidinyl, pyridinyl, and imidazole. In an electrolyte environment, the first functional group forms a positively charged group, and the second functional group forms a negatively charged group.

12. A method for preparing a separator for a battery cell, comprising: A coating slurry comprising a polymer additive is provided; the polymer additive comprises a first functional group and a second functional group, the first functional group comprising one or more of the following: bis(trifluoromethyl)sulfonylimino, bis(trifluoromethyl)sulfonylimino, trifluoroborate, hexafluorophosphate, sulfonic acid, hexafluoroarsenate, trifluoromethanesulfonic acid, difluorophosphate, bis(oxalate)borate, difluorooxalateborate, difluorobis(oxalate)phosphate, tetrafluorooxalate phosphate, and imidazolyl; the second functional group comprises one or more of the following: quaternary ammonium ion, pyrrolyl, pyrrole, piperidinyl, pyridinyl, and imidazolyl. The coating slurry is applied to at least one side of a porous base membrane and dried to obtain a separation membrane.

13. A battery device, characterized in that, The battery cell can be formed by preparing the battery cell according to any one of claims 1 to 10 or by preparing the separator according to claim 11 or the separator prepared by the method of claim 12.

14. An electrical appliance, characterized in that, Includes the battery device as described in claim 13.

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