Separator, method for manufacturing the same, battery, battery pack, and electric device

Abstract

The embodiment of the present application provides a diaphragm and a preparation method thereof, a battery, a battery pack and an electric device. The diaphragm comprises a base film and a coating layer arranged on at least one side surface of the base film, and the coating layer comprises a polymer skeleton and a lithium supplement agent and an unsaturated amino acid material dispersed in the polymer skeleton. The diaphragm has good thermal stability and ionic conductivity, and can improve the cycle performance and safety performance of the battery.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a separator and its preparation method, a battery, a battery pack, and an electrical device. Background Technology

[0002] In high-power applications such as new energy vehicles, energy storage systems, and consumer electronics, secondary batteries need to operate stably under high temperatures or extreme conditions. The separator is one of the core components of the battery, and its performance directly affects the battery's safety and cycle life.

[0003] However, current separators have poor thermal stability and are prone to shrinkage or even melting under high-temperature conditions, causing short circuits, fires, or even explosions, resulting in poor battery safety. Furthermore, conventional separators have low ionic conductivity, leading to reduced battery cycle life.

[0004] Therefore, it is urgent to improve the thermal stability and ionic conductivity of the separator in order to enhance battery safety and cycle life. Summary of the Invention

[0005] This invention provides a separator and its preparation method, a battery, a battery pack, and an electrical device. The separator has high thermal stability and ionic conductivity, which can improve the safety and cycle life of the battery.

[0006] This invention provides a separator, including a base membrane and a coating disposed on at least one surface of the base membrane. The coating includes a polymer backbone and lithium supplementing agent and unsaturated amino acid material dispersed in the polymer backbone.

[0007] In some embodiments of the present invention, the polymer skeleton includes polyamino acid materials and non-amino acid polymer fiber materials.

[0008] In some embodiments of the present invention, the polyamino acid material includes structural units derived from the unsaturated amino acid material.

[0009] In some embodiments of the present invention, the total mass ratio of the unsaturated amino acid material and the polyamino acid material to the mass ratio of the non-amino acid polymer fiber material is (0.02~1):1;

[0010] And / or, the non-amino acid polymer fiber material accounts for 38wt%~85wt% of the mass percentage in the coating;

[0011] And / or, the mass ratio of the lithium supplement to the non-amino acid polymer fiber material is (0.05~0.80):1;

[0012] And / or, the mass percentage of the unsaturated amino acid-based material in the total mass of the unsaturated amino acid-based material and the polyamino acid-based material is less than or equal to 20 wt%.

[0013] In some embodiments of the present invention, the unsaturated amino acid-based material includes one or more of tryptophan, tryptophan derivatives, asparagine, asparagine derivatives, glutamine, and glutamine derivatives;

[0014] And / or, the non-amino acid-based polymer fiber material includes one or more of fluoropolymers, polyesters, celluloses, cellulose derivatives, polyolefins, polylactic acids, polyamides, polyimides, polyacrylonitriles, and polyethylene oxides;

[0015] And / or, the lithium supplement includes at least one of organic lithium salts and inorganic lithium salts;

[0016] The base film includes one or more materials of polyethylene and polypropylene.

[0017] In some embodiments of the present invention, the inorganic lithium salt includes Li 1+a Al a Ti 2-a (PO4)3, Li 3b La 2 / 3-b TiO3, Li 6+2c La3Zr 2-c M c O 12 , lithium nitrate, lithium iodide, lithium bromide, lithium chloride, lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, or the like; wherein, 0.1 ≤ a ≤ 0.5, 0.04 ≤ b ≤ 0.16, 0 < c ≤ 0.6, and M is selected from one or more elements of Ta, Nb, and Al;

[0018] The organic lithium salt includes one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium trifluoromethanesulfonate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, and lithium bis(oxalato)phosphate.

[0019] The embodiments of the present invention further provide a method for preparing the separator as described above, including the following steps,

[0020] Coating a slurry including a polymer skeleton raw material, a lithium supplement, and an auxiliary agent on at least one surface of the base film, and obtaining the separator after a polymerization reaction;

[0021] The polymer skeleton raw material includes an unsaturated amino acid-based material.

[0022] In some embodiments of the present invention, the slurry further includes a non-amino acid-based polymer fiber material;

[0023] And / or, the auxiliary agent includes at least one of an initiator and a catalyst.

[0024] In some embodiments of the present invention, the mass ratio of the initiator to the unsaturated amino acid material is (0.01% to 2%):1, preferably (0.2% to 1%):1;

[0025] And / or, the reaction temperature of the polymerization reaction can be 40℃~85℃, and the reaction time can be 0.3h~18h.

[0026] In some embodiments of the present invention, the initiator includes one or more of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, dilauryl peroxide, diethylhexyl percarbonate, cumene hydroperoxide, tert-butyl hydroperoxide, dodecyl peroxide, tert-butyl peroxide, tert-butyl peroxybenzoate, diisopropyl peroxide, potassium persulfate, or ammonium persulfate.

[0027] This invention also provides a battery comprising the separator as described above, or a separator prepared by the method described above.

[0028] This invention also provides a battery pack comprising at least two batteries as described above.

[0029] This invention also provides an electrical device, including the battery described above, or the battery pack described above.

[0030] The present invention provides a separator and its preparation method, a battery, a battery pack, and an electrical device. By providing a coating on at least one side of the base membrane, the coating includes a polymer skeleton and a lithium supplement agent and an unsaturated amino acid material dispersed in the polymer skeleton. The polymer skeleton has strong thermal stability, and the unsaturated amino acid material can uniformly disperse the lithium supplement agent in the polymer skeleton. The synergistic effect of the three is beneficial to improving both the thermal stability and ionic conductivity of the separator, thereby improving the cycle performance and safety performance of the battery. Attached Figure Description

[0031] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0032] Figure 1 This is a SEM image of the diaphragm surface provided in Embodiment 1 of the present invention.

[0033] The accompanying drawings have illustrated specific embodiments of the invention, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0035] Currently, the low thermal stability and ionic conductivity of separators make it difficult to improve battery safety and cycle life.

[0036] Existing technologies often involve coating the surface of the separator substrate (base membrane) with a polymer coating to improve its heat shrinkage resistance (thermal stability). However, most polymers still cannot withstand the high temperatures of the battery, and the thermal stability of the separator has not been significantly improved. Furthermore, the polymer coating will further deteriorate the ionic conductivity of the battery, resulting in a reduction in the battery's cycle performance.

[0037] The inventors attempted to add lithium supplements (lithium salts) to the polymer coating to improve the ionic conductivity of the battery. However, the lithium supplements had poor compatibility with the polymer materials in the polymer coating, resulting in uneven distribution of coating components, which reduced the thermal stability of the separator and failed to effectively improve the safety performance of the battery.

[0038] Therefore, the inventors aimed to improve both the thermal stability and ionic conductivity of the separator in order to enhance the safety and cycle life of the battery.

[0039] Based on this, embodiments of the present invention provide a diaphragm, including a base membrane and a coating disposed on at least one side surface of the base membrane, the coating including a polymer backbone and lithium salt and unsaturated amino acid materials dispersed in the polymer backbone.

[0040] When the separator of the present invention has the above-described structure and composition, it has good thermal stability and ionic conductivity, which can improve the safety performance and cycle performance of the battery.

[0041] The inventors analyzed that the reason why the separator of the present invention can improve the safety performance and cycle performance of the battery is that: the separator of the present invention has a coating on at least one side of the base film. The coating includes a polymer skeleton and lithium replenishing agent and unsaturated amino acid materials dispersed in the polymer skeleton. First, the polymer skeleton, as the main structural body of the separator, can not only make the separator have excellent mechanical strength, but also effectively improve the thermal stability of the separator through its high glass transition temperature (Tg) or rigid segments, thereby suppressing the melting shrinkage and deformation of the separator at high temperature. At the same time, the introduction of the lithium replenishing agent can dissociate free lithium ions, significantly improving the ionic conductivity of the system. On the other hand, it can release active lithium during the first cycle of the battery, playing an in-situ lithium replenishment role, which is beneficial to improving ionic conductivity and alleviating irreversible capacity loss at the negative electrode interface. Furthermore, unsaturated amino acid units can form coordination or electrostatic interactions with lithium-replenishing anions (such as TFSI⁻, FSI⁻, etc.) or lithium ions through polar functional groups (such as carboxyl groups, amino groups, etc.) on their side chains, effectively anchoring the lithium-replenishing agent. This ensures uniform dispersion of the lithium-replenishing agent in the polymer matrix, avoiding uneven ion transport caused by salting out or aggregation. This intermolecular interaction also enhances the physical crosslinking density between polymer segments, thereby synergistically strengthening the mechanical properties and heat resistance of the separator. Moreover, the hydrophilic groups introduced by unsaturated amino acids can significantly reduce the surface energy of the separator, improve its wetting behavior with organic electrolytes, increase electrolyte absorption and retention capacity, thereby optimizing electrode / electrolyte interface contact, reducing interfacial impedance, and ultimately synergistically promoting efficient and uniform lithium-ion conduction in the separator. Finally, when the coating of this embodiment includes unsaturated amino acids, it can also capture free radicals generated during battery cycling through amino groups, which helps reduce battery gas production and better improve the battery's cycle performance and safety performance. In summary, the polymer skeleton, lithium replenishing agent, and unsaturated amino acids work synergistically to improve the overall performance of the separator in terms of ionic conductivity, mechanical strength, and thermal stability, thereby enhancing the cycle performance and safety performance of the battery.

[0042] The above-described structure of the separator can be tested using conventional testing methods and instruments in the art, such as SEM and infrared spectroscopy. Specifically, the battery can be fully discharged and disassembled, and the separator can be separated. Then, a cross-section of the separator can be obtained using FIB, and the surface and cross-section of the separator can be observed using SEM. This allows for the differentiation between the base film and the coating. In the coating portion, the lithium supplement and polymer backbone can be identified by the difference in elemental contrast under SEM, allowing for the analysis of the lithium supplement content. By sampling the coating and performing infrared spectroscopy, the type and content of unsaturated amino acid materials and lithium supplements included in the coating can be obtained based on the type and area of ​​characteristic peaks. Specifically, in infrared spectroscopy analysis, if the coating contains unsaturated amino acid materials, these peaks are typically visible at 3200–3500 cm⁻¹.-1 N–H stretching vibration absorption peaks were observed at 1640–1690 cm⁻¹. -1 An amide I band (C=O) or stretching vibration peak of carboxylic acid C=O appears, and an amide II band (N–H bending vibration) appears at 1500–1560 cm⁻¹. If carbon-carbon unsaturated bonds or aromatic ring structures are present, a peak may appear at 1600–1650 cm⁻¹. -1 A C=C stretching vibration peak appears, possibly accompanied by a peak at 2500–3300 cm⁻¹. -1 The broad O–H peaks of carboxylic acids and 1000–1300 cm⁻¹ -1 The C–N stretching vibrations are within a certain range; however, the infrared characteristics of lithium supplements vary depending on the type, for example, lithium carbonate (Li₂CO₃) exhibits characteristics within 1430–1500 cm⁻¹. -1 860–880 cm -1 and 700–750 cm -1 Corresponding to CO3 2- Asymmetric stretching, out-of-plane bending, and in-plane bending vibrations, phosphate lithium supplements such as Li3PO4 at 1000–1100 cm⁻¹ -1 Presenting PO4 3- The strong and broad stretching vibration peak is observed in organic lithium supplements, which may be around 1550–1650 cm⁻¹. -1 A C=O splitting peak appears in lithium carboxylate, and it is located at 1000–1100 cm⁻¹. -1 The region shows C–O–Li related vibrations, and some organolithium salts containing unsaturated structures may also be present at 1600–1650 cm⁻¹. -1 C=C absorption occurs; in addition, the type and content of lithium supplement can be comprehensively judged by combining infrared, XRD, XPS or Raman spectroscopy.

[0043] In some embodiments of the present invention, the polymer backbone includes polyamino acid materials and non-amino acid polymer fiber materials, which is beneficial for further improving the ion conductivity and thermal stability of the membrane, thereby improving its overall performance. Specifically, the polyamino acid materials and non-amino acid polymer fiber materials can better form an interpenetrating network through hydrogen bonds, allowing for better dispersion of the lithium supplement in the coating. Specifically, the polyamino acid materials in the embodiments of the present invention can be polypeptide materials obtained by the condensation reaction of amino and carboxyl groups of conventional amino acids, or polyamino acids obtained by the condensation of unsaturated bonds (such as carbon-carbon double bonds and carbon-oxygen double bonds) of unsaturated amino acids; no particular limitation is made in this regard.

[0044] In some embodiments, coating at least a portion of the surface of the lithium replenisher with an unsaturated amino acid material can further improve the dispersibility of the lithium replenisher, thereby improving the thermal stability of the separator and thus improving the safety performance of the battery.

[0045] In some embodiments, the polyamino acid material includes structural units derived from unsaturated amino acid materials, which can further promote the compatibility between the components in the coating, better improve the thermal stability of the separator, and thus better improve the thermal safety performance of the battery.

[0046] In some embodiments of the present invention, the mass ratio of the total mass of unsaturated amino acid materials and polyamino acid materials to the mass ratio of the non-amino acid polymer fiber materials is (0.02~1):1, which is beneficial to further improve the thermal stability of the separator and thus better improve the safety performance of the battery. For example, the mass ratio of the total mass of unsaturated amino acid materials and polyamino acid materials to the mass ratio of the non-amino acid polymer fiber materials is, for example, 0.02:1, 0.1:1, 0.2:1, 0.4:1, 0.6:1, 1:1, or any combination thereof. The embodiments of the present invention can use conventional testing methods in the art to test the mass ratio of the total mass of unsaturated amino acid materials and polyamino acid materials to the mass ratio of the non-amino acid polymer fiber materials, for example, infrared spectroscopy can be used as described above. In this embodiment of the invention, when the mass ratio of the total mass of unsaturated amino acid materials and polyamino acid materials to the mass ratio of the non-amino acid polymer fiber materials exceeds 1:1 (for example, 1.5:1), the improvement in the mechanical strength and thermal stability of the diaphragm is not significant compared to when the mass ratio of the total mass of unsaturated amino acid materials and polyamino acid materials to the mass ratio of the non-amino acid polymer fiber materials is 1:1. Therefore, a mass ratio of the total mass of unsaturated amino acid materials and polyamino acid materials to the mass ratio of the non-amino acid polymer fiber materials of (0.02~1):1 is beneficial to further improve industrial economics.

[0047] In some embodiments, the non-amino acid polymer fiber material accounts for 38 wt% to 85 wt% of the coating by mass, which is beneficial for further improving the mechanical strength and thermal stability of the separator. Furthermore, this mass percentage range can better balance ion transport performance and structural integrity, thereby more effectively ensuring the safety performance of the battery. For example, the mass percentage of the non-amino acid polymer fiber material in the coating may be 38 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, or any combination thereof. The embodiments of the present invention can use conventional testing methods in the art to test the mass percentage of the non-amino acid polymer fiber material in the coating. For example, referring to the above method, infrared spectroscopy can be used for testing, and the polymer component can be semi-quantitatively analyzed by the relative intensity of characteristic absorption peaks. This can be calibrated using a standard curve or a sample with known proportions to determine its specific mass percentage in the coating.

[0048] In some embodiments, the mass ratio of lithium replenisher to non-amino acid polymer fiber material is (0.05–0.8):1, which can better provide an active lithium source and better maintain the basic structure of the separator. This mass ratio range can better suppress irreversible capacity loss during the first cycle, while further reducing interfacial side reactions or mechanical property degradation caused by excessive lithium replenisher, thereby better improving the cycle performance and safety performance of the battery. For example, the mass ratio of lithium replenisher to non-amino acid polymer fiber material is, for example, 0.05:1, 0.20:1, 0.40:1, 0.60:1, 0.80:1, or any combination thereof. The mass ratio of lithium replenisher to non-amino acid polymer fiber material can be tested using conventional testing methods in the art. For example, referring to the above method, SEM combined with energy dispersive spectroscopy (EDS) can be used to perform semi-quantitative characterization of the coating surface to determine its specific mass ratio.

[0049] In some embodiments, the mass percentage of unsaturated amino acid materials in the total mass of unsaturated amino acid materials and polyamino acid materials is less than or equal to 20 wt%. This better preserves the structural integrity and film-forming properties of the polyamino acid backbone, and better balances the uniform dispersion of lithium salts, sufficient electrolyte wetting, and effective improvement of ionic conductivity. The embodiments of the present invention can use conventional testing methods in the art to test the mass percentage of unsaturated amino acid materials in the total mass of unsaturated amino acid materials and polyamino acid materials. For example, referring to the above method, infrared spectroscopy can be used for testing, and semi-quantitative analysis can be performed by the relative intensity of characteristic absorption peaks (such as C=O stretching vibration peaks and C=C stretching vibration peaks). Calibration can be performed using a standard curve or samples with known proportions to determine its specific mass percentage. Furthermore, in some embodiments, if the unsaturated amino acid materials form a polyamino acid network via peptide bonds, amide bond characteristic peaks can be used for characterization.

[0050] In some embodiments of the present invention, the unsaturated amino acid material includes one or more of tryptophan, tryptophan derivatives, asparagine, asparagine derivatives, glutamine, and glutamine derivatives, which is beneficial to further improve the dispersion performance of the lithium supplement and thus better improve the cycle performance of the battery.

[0051] In some embodiments, non-amino acid polymer fiber materials include one or more of fluoropolymers, polyesters, cellulose, cellulose derivatives, polyolefins, polylactic acid, polyamides, polyimides, polyacrylonitrile, and polyethylene oxide, which can further improve the thermal stability of the separator, thereby better improving the safety and cycle performance of the battery.

[0052] In some embodiments, the lithium supplementing agent includes at least one of organic lithium salts and inorganic lithium salts, which is beneficial to further alleviate the capacity attenuation during cycling and better improve the cycling performance of the battery.

[0053] In some embodiments of the present invention, the inorganic lithium salt includes Li 1+a Al a Ti 2-a (PO4)3, Li 3b La 2 / 3-b TiO3, Li 6+ 2c La3Zr 2-c M c O 12 、lithium nitrate, lithium iodide, lithium bromide, lithium chloride, lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, or one or more of them; wherein, 0.1 ≤ a ≤ 0.5, 0.04 ≤ b ≤ 0.16, 0 < c ≤ 0.6, and M is selected from one or more elements of Ta, Nb, and Al, which is beneficial to further alleviate the capacity attenuation during cycling and better improve the cycling performance of the battery.

[0054] In some embodiments, the base film includes at least one of polyethylene and polypropylene, which is beneficial to further improve the thermal stability of the separator and thus better improve the safety performance of the battery. Specifically, the base film of the embodiments of the present invention can be a multi-layer material obtained by compounding polyethylene (PE) material and polypropylene (PP) material. For example, it can be a base film obtained by combining a three-layer material of PE / PP / PE.

[0055] In some embodiments, the organic lithium salt includes one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium trifluoromethanesulfonate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, and lithium bis(oxalato)phosphate, which is beneficial to further alleviate the capacity attenuation during cycling and better improve the cycling performance of the battery.

[0056] The embodiments of the present invention also provide a preparation method of the above-mentioned separator, including the following steps: coating a slurry including a polymer skeleton raw material, a lithium supplementing agent, and an auxiliary agent on at least one surface of the base film, and obtaining the separator after a polymerization reaction; the polymer skeleton raw material includes unsaturated amino acid materials.

[0057] The present invention provides a separator with the aforementioned structure and composition prepared by the method described above. This separator includes a base membrane and a coating disposed on at least one surface of the base membrane. The coating comprises a polymer backbone and lithium supplementing agents and unsaturated amino acid materials dispersed within the polymer backbone. This separator exhibits good thermal stability and ionic conductivity, which is beneficial for improving battery safety and cycle performance. Furthermore, this preparation method, through a one-step coating process (without plasma pretreatment), directly forms a coating with a three-dimensional polymer backbone structure, greatly simplifying the separator preparation process and improving industrial economics.

[0058] In detail, the polymer skeleton raw material in this embodiment of the invention includes unsaturated amino acid materials. After the unsaturated amino acid materials undergo a polymerization reaction, a portion of the unsaturated amino acid materials form a polymer skeleton through the polymerization reaction, while a portion of the unsaturated amino acid materials do not participate in the polymerization reaction and remain in the coating in a form containing unsaturated bonds. That is, the polyamino acid materials in the membrane include structural units from the unsaturated amino acid materials, and the formed coating includes unsaturated amino acid materials.

[0059] In detail, the additives in the embodiments of the present invention are used to promote the polymerization reaction. The polymerization reaction in the embodiments of the present invention can be a polymerization reaction between unsaturated bonds of unsaturated amino acid materials, or a condensation reaction between amino and carboxyl groups of unsaturated amino acid materials.

[0060] In some embodiments of the present invention, the slurry further includes a solvent. The present invention does not impose specific limitations on the selection of the solvent, which can be chosen according to actual circumstances. For example, the solvent can be water.

[0061] The embodiments of the present invention can also perform a mixing process on the slurry, which further improves the uniformity of the components in the slurry and is more conducive to the preparation of a membrane with higher thermal stability and ionic conductivity.

[0062] In some embodiments, the slurry also includes non-amino acid polymer fiber materials, which helps to further improve the thermal stability of the separator and thus better improve the thermal safety performance of the battery.

[0063] The embodiments of the present invention can control the mass ratio of non-amino acid polymer fiber materials in the coating by controlling the mass ratio of non-amino acid polymer fiber materials in the slurry during the preparation process; and can control the mass ratio of lithium supplementing agent to non-amino acid polymer fiber materials by controlling the mass ratio of lithium supplementing agent to non-amino acid polymer fiber materials in the slurry during the preparation process.

[0064] In some embodiments, the additives include at least one of an initiator and a catalyst, which can further promote the polymerization reaction, better prepare a thermally stable separator, and better improve the safety of the battery.

[0065] In some embodiments, the mass ratio of initiator to unsaturated amino acid material is (0.01% to 2%):1, which allows for better control of the polymerization rate and crosslinking degree, further improving the mechanical strength and thermal stability of the membrane. For example, the mass ratio of initiator to unsaturated amino acid material may be 0.01%:1, 0.1%:1, 0.2%:1, 0.5%:1, 1%:1, 2%:1, or any combination thereof. Preferably, it is (0.2% to 1%):1, further enhancing the above-mentioned effects.

[0066] In detail, embodiments of the present invention can control the mass ratio of unsaturated amino acid materials in the total mass of unsaturated amino acid materials and polyamino acid materials by controlling the amount of initiator used.

[0067] The embodiments of the present invention can control the ratio of the total mass of unsaturated amino acid materials and polyamino acid materials to the mass of non-amino acid polymer fiber materials by controlling the amount of unsaturated amino acid materials (i.e., polymer backbone raw materials) and non-amino acid polymer fiber materials used in the preparation method.

[0068] In some embodiments, the polymerization reaction temperature can be 40°C to 85°C, and the reaction time can be 0.3h to 18h. This allows for better cross-linking of unsaturated amino acid materials, better ensuring the uniformity of the polymer backbone film formation and the integrity of the pore structure. This, in turn, balances the mechanical properties, thermal stability, and ion transport capacity of the separator, thereby improving the battery's safety and cycle performance. For example, the polymerization reaction temperature can be a range of 40°C, 50°C, 60°C, 70°C, 80°C, 85°C, or any combination thereof, and the reaction time can be a range of 0.3h, 1h, 3h, 6h, 12h, 18h, or any combination thereof.

[0069] In some embodiments of the present invention, the initiator includes one or more of azobisisobutyronitrile (AIBN), azobisisoheptanenitrile, benzoyl peroxide, dilauryl peroxide, diethylhexyl percarbonate, cumene hydroperoxide, tert-butyl hydroperoxide, dodecyl peroxide, tert-butyl peroxide, tert-butyl peroxybenzoate, tert-butyl peroxyvalerate, diisopropyl peroxide, potassium persulfate, or ammonium persulfate, which can better promote the polymerization reaction.

[0070] In the above preparation method, the condensation ratio is determined by the absorption peaks in the infrared spectral region of the coating through infrared spectral testing. The condensation ratio is calculated based on the absorption position and intensity of the double bonds (including carbon-carbon double bonds and carbon-oxygen double bonds). The condensation ratio is calculated as follows: (double bond absorption peak intensity before condensation ratio - double bond absorption peak intensity after condensation ratio) / double bond absorption peak intensity before condensation ratio × 100%.

[0071] This invention also provides a battery including the above-described positive electrode sheet. The battery of this invention has advantages corresponding to the above-described separator, which will not be elaborated here.

[0072] Generally, a battery includes an electrolyte, a battery cell, and a casing that encapsulates the battery cell. The electrolyte is injected into the battery cell inside the casing. The battery cell includes a positive electrode, a negative electrode, and a separator located between the positive and negative electrode. The battery cell can be a stacked cell, meaning it is composed of alternating layers of positive electrode, separator, and negative electrode; or it can be a wound cell, meaning it is composed of stacked positive electrode, separator, and negative electrode, which are then wound together.

[0073] In this embodiment of the invention, the battery cell can be packaged using conventional housing materials in the art, such as flexible packaging materials like aluminum-plastic film, but is not limited thereto.

[0074] Specifically, the positive electrode sheet includes a positive current collector and a positive active material layer located on at least one side surface of the positive current collector. Specifically, the positive active material layer can be provided on one side surface in the thickness direction of the positive current collector, or positive active material layers can be provided on both opposite sides surface in the thickness direction of the positive current collector.

[0075] The positive electrode active material layer includes a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder. In the positive electrode active material layer, the mass percentage of the positive electrode active material can be 70% to 99%, for example, 70%, 75%, 80%, 85%, 90%, 93%, 95%, 97%, 99%, or any combination thereof. The mass fraction of the positive electrode conductive agent can be 0.5% to 15%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 8%, 10%, 13%, 15%, or any combination thereof. The mass fraction of the positive electrode binder can be 0.5% to 15%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 8%, 10%, 13%, 15%, or any combination thereof.

[0076] In some embodiments, the battery is a lithium-ion battery, and the positive electrode active material includes, but is not limited to, LiCoO2, LiNiO2, and LiCo. x Ni1-x O2 (0≤x≤1), LiCo x Ni 1-x-y Al y O2 (0≤x≤1, 0≤y≤1), LiMn2O4, LiFe x Mn y M z O4 (M is one or more of Al, Mg, Ga, Cr, Co, Ni, Cu, Zn or Mo, 0≤x≤1, 0≤y≤1, 0≤z≤1, x+y+z=1), Li 1＋ x L 1－y－z M y N z O2 (L, M, N are one or more of Li, Co, Mn, Ni, Fe, Al, Mg, Ga, Ti, Cr, Cu, Zn, Mo, F, I, S, B, -0.1≤x≤0.2, 0≤y≤1, 0≤z≤1, 0≤y+z≤1), LiFePO4, Li3V2(PO4)3, Li3V3(PO4)3, LiVPO4F, Li2CuO2, Li5FeO4, and metal sulfides and oxides (such as TiS2, V2S3, FeS, FeS2, LiMS) x (M is at least one of the transition metal elements such as Ti, Fe, Ni, Cu, Mo, etc., 1≤x≤2.5), TiO2, Cr3O8, V2O5, MnO2, etc.

[0077] In this embodiment of the invention, the positive electrode conductive agent in the positive electrode active material layer can be a conventional conductive material in the art. For example, the positive electrode conductive agent in the positive electrode active material layer may include one or more of conductive carbon black, conductive graphite, carbon nanotubes (CNTs), carbon fibers, graphene, acetylene black, and Ketjen black.

[0078] In this embodiment of the invention, the positive electrode binder in the positive electrode active material layer can be a conventional binder in the art. For example, the positive electrode binder in the positive electrode active material layer may include one or more of the following: polyvinylidene fluoride (PVDF), polyvinylidene fluoride, polyvinyl fluoride, polyethylene, polypropylene, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, etc.

[0079] The embodiments of the present invention may employ conventional positive current collectors in the art, for example, positive current collectors may include aluminum foil.

[0080] In this embodiment of the invention, the positive electrode sheet can be prepared by conventional methods in the art, such as by coating. Specifically, the components used to form the positive electrode active material layer, such as the positive electrode conductive agent and the positive electrode binder, can be dispersed in a solvent, such as N-methylpyrrolidone (NMP), to prepare a positive electrode slurry. This slurry is then coated onto the surface of the positive electrode current collector, and after drying, rolling, and other processes, the positive electrode sheet is obtained. The coating, drying, and rolling processes involved are conventional operations for preparing positive electrode sheets using the coating method, and are not particularly limited thereto.

[0081] In practice, a slurry containing positive electrode active material can be prepared at a temperature of 20~45℃; conventional coating equipment in the field, such as continuous coating equipment, can be used to coat the slurry containing positive electrode active material onto the surface of the positive electrode current collector.

[0082] Specifically, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer located on at least one side surface of the negative electrode current collector. Specifically, the negative electrode active material layer can be provided on one side surface of the negative electrode current collector, or negative electrode active material layers can be provided on both opposite sides of the negative electrode current collector in the thickness direction.

[0083] Specifically, the negative electrode active material layer may include a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder, all of which can be conventional materials in the art. For example, the negative electrode active material may include graphite, and the negative electrode conductive agent may include one or more of conductive carbon black, carbon nanotubes (CNT), acetylene black, graphene, Ketjen black, and carbon fiber; the negative electrode binder may include one or more of sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyvinyl alcohol, and sodium polyacrylate.

[0084] The embodiments of the present invention may employ conventional negative electrode current collectors in the art, for example, negative electrode current collectors include copper foil.

[0085] In this embodiment of the invention, the negative electrode sheet can be prepared by conventional methods in the art, such as by coating. Specifically, the components used to form the negative electrode active material layer, negative electrode conductive agent, negative electrode binder, etc., can be dispersed in a solvent, such as water, to prepare a negative electrode slurry. This slurry is then coated onto the surface of the negative electrode current collector, and after drying, rolling, and other processes, the negative electrode sheet is obtained. The coating, drying, and rolling processes involved are conventional operations for preparing negative electrode sheets using the coating method, and are not particularly limited thereto.

[0086] In practice, a slurry containing negative electrode active material can be prepared at a temperature of 20℃~45℃; conventional coating equipment in the field, such as continuous coating equipment, can be used to coat the slurry containing negative electrode active material onto the surface of the negative electrode current collector.

[0087] In this embodiment of the invention, the separator is used to separate the positive electrode and the negative electrode to prevent the positive electrode and the negative electrode from coming into contact and short-circuiting.

[0088] The electrolyte in this embodiment of the invention can be a conventional electrolyte in the art. For example, the electrolyte is a non-aqueous electrolyte, which may specifically include organic solvents, additives and electrolyte salts. Organic solvents include one or more of ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC) and propylene carbonate (PC). Additives include, for example, fluoroethylene carbonate (FEC) and vinylene carbonate (VC). Electrolyte salts may include lithium salts (if it is a lithium-ion battery), such as lithium hexafluorophosphate (LiPF6), but are not limited thereto.

[0089] The embodiments of the present invention can assemble components such as positive electrode, separator and negative electrode into a battery using conventional methods in the art. For example, positive electrode, separator and negative electrode can be stacked in an alternating manner to obtain a stacked cell (or wound into a wound cell); then the cell is placed in a casing (outer packaging) and after conventional processes such as electrolyte injection (i.e., injection of electrolyte) and encapsulation, the battery is obtained.

[0090] This invention also provides a battery pack comprising at least two of the above-described batteries, which has advantages corresponding to the above-described separator, and will not be described in detail hereafter.

[0091] Generally, a battery pack includes multiple batteries as individual cells, which are connected to form the battery pack. These batteries can be electrically connected using methods conventional in the art, such as series connection, parallel connection, or a combination of these connection methods, without any particular limitation.

[0092] This invention also provides an electrical device including the battery described above, which has advantages corresponding to the diaphragm described above, and will not be described in detail here.

[0093] The electrical equipment used in the embodiments of the present invention can be conventional electrical equipment in the art, such as power equipment (e.g., electric vehicles, electric cars), electronic equipment (e.g., mobile phones, tablets, laptops, digital cameras, etc.), wearable devices (e.g., watches, bracelets, VR glasses, etc.), energy storage power stations, etc., and there are no particular limitations on this.

[0094] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0095] Example 1

[0096] The diaphragm in this embodiment is prepared by the following method:

[0097] Dissolve 100g of polyimide fiber (polymer backbone material), 10g of lithium carbonate (lithium supplement) and 0.05g of AIBN (initiator) in 300ml of water. After stirring until dissolved, add 25g of tryptophan (an unsaturated amino acid material, also part of the polymer backbone material) and continue mixing for 30min to obtain a slurry. Then, transfer the slurry onto a PE base film by microgravure roller coating and bake at 75℃ for 1h (polymerization reaction) to obtain a separator.

[0098] Example 2

[0099] This embodiment is basically the same as Embodiment 1, except that the unsaturated amino acid material in this embodiment is asparagine, and the lithium supplementer is Li. 1.3 Al 0.3 Ti 1.7 (PO4)3.

[0100] Example 3

[0101] This embodiment is basically the same as that of Embodiment 1, except that the initiator in this embodiment is azobisisoheptanenitrile.

[0102] The difference between Examples 4-16 and Example 1 lies in the amount of polymer skeleton raw materials (including unsaturated amino acid materials and non-amino acid polymer fiber materials; in the examples and comparative examples of this invention (if non-amino acid polymer fiber materials are present), the amount of lithium supplementer, and the amount of initiator. The parameters such as the total mass ratio of unsaturated amino acid materials and polyamino acid materials to the mass ratio of non-amino acid polymer fiber materials in the prepared membrane, the mass percentage of non-amino acid polymer fiber materials in the coating, the mass ratio of lithium supplementer to non-amino acid polymer fiber materials, and the mass percentage of unsaturated amino acid materials in the total mass of unsaturated amino acid materials and polyamino acid materials are different, as detailed in Table 1.

[0103] Example 17

[0104] The difference between this embodiment and Embodiment 1 is that the slurry in this embodiment does not include polyimide fibers, and the mass of tryptophan is 25g.

[0105] Comparative Example 1

[0106] The difference between this comparative example and Example 1 is that the slurry in this comparative example is prepared by the following method: 100g of polyimide fiber and 10g of ceramic are dissolved in 300ml of water and stirred until dissolved. Then, 25g of polymethyl methacrylate is added and the mixture is stirred for 30min to obtain the slurry.

[0107] Comparative Example 2

[0108] The difference between this comparative example and Example 1 is that the slurry in this comparative example does not contain tryptophan.

[0109] Comparative Example 3

[0110] The difference between this comparative example and Example 1 is that the diaphragm in this comparative example is a common PP diaphragm.

[0111] The differences in parameters such as the total mass ratio of unsaturated amino acid materials and polyamino acid materials to non-amino acid polymer fiber materials, the mass percentage of non-amino acid polymer fiber materials in the coating, the mass ratio of lithium supplement to non-amino acid polymer fiber materials, and the mass percentage of unsaturated amino acid materials in the total mass of unsaturated amino acid materials and polyamino acid materials prepared in the above embodiments and comparative examples are shown in Table 1.

[0112] Table 1

[0113]

[0114] In Table 1, " / " indicates that the substance is not present.

[0115] Test case

[0116] (a) Diaphragm property testing

[0117] After the battery is fully discharged, it is disassembled and the separator is separated. The cross-section of the separator is then obtained using FIB (Fiber Optic Infrared) and observed using SEM (Scanning Electron Microscopy). This allows for the differentiation between the base film and the coating. In the coating section, the difference in elemental contrast between the lithium replenishing agent and the polymer backbone under SEM can be used for identification. Infrared spectroscopy testing of coating samples reveals the types and composition of unsaturated amino acid materials and lithium replenishing agents included in the coating. This includes the mass ratio of the total mass of unsaturated amino acid and polyamino acid materials to the mass of non-amino acid polymer fiber materials, the mass percentage of non-amino acid polymer fiber materials in the coating, the mass ratio of lithium replenishing agents to non-amino acid polymer fiber materials, and the mass percentage of unsaturated amino acid materials in the total mass of unsaturated amino acid and polyamino acid materials. Specifically, the presence and content of unsaturated amino acid materials in the coating can be analyzed using the following characteristic peaks and peak areas: [The peak area is typically found in the 3200–3500 cm⁻¹ region]. -1 N–H stretching vibration absorption peaks were observed at 1640–1690 cm⁻¹. -1An amide I band (C=O) or stretching vibration peak of carboxylic acid C=O appears, and an amide II band (N–H bending vibration) appears at 1500–1560 cm⁻¹; in addition, unsaturated amino acid materials contain carbon-carbon unsaturated bonds or aromatic ring structures, and can reach 1600–1650 cm⁻¹. -1 A C=C stretching vibration peak appears, accompanied by a peak at 2500–3300 cm⁻¹. -1 The broad O–H peaks of carboxylic acids and 1000–1300 cm⁻¹ -1 C–N stretching vibrations within the range; lithium carbonate (Li₂CO₃) as a lithium supplement in the range of 1430–1500 cm⁻¹. -1 860–880cm -1 and 700–750 cm -1 Corresponding to CO3 2- Asymmetric stretching, out-of-plane bending, and in-plane bending vibrations, phosphate lithium supplements such as Li3PO4 at 1000–1100 cm⁻¹ -1 Presenting PO4 3- The strong and broad stretching vibration peaks of organic lithium supplements are observed at 1550–1650 cm⁻¹. -1 A C=O splitting peak appears in lithium carboxylate, and it is located at 1000–1100 cm⁻¹. -1 The region shows C–O–Li correlated vibrations, with some organolithium salts containing unsaturated structures exhibiting vibrations at 1600–1650 cm⁻¹. -1 C=C absorption occurs. SEM images of the membrane from Example 1 are shown below. Figure 1 As shown, by Figure 1 It is known that the coating of the diaphragm in Example 1 includes a polymer backbone.

[0118] Heat shrinkage performance test method: Disassemble the battery in an inert atmosphere glove box, carefully separate the positive and negative electrode plates, and remove the separator; then immerse the separator in anhydrous dimethyl carbonate or anhydrous ethanol and rinse repeatedly 3-5 times to remove electrolyte residue, and then vacuum dry at 60℃ for more than 12 hours. Cut the dried separator into samples according to GB / T 36363-2018 standard, and bake in an oven at 180℃ for 1 hour. After cooling, measure the dimensional change and calculate the heat shrinkage rate. The test results are shown in Table 2.

[0119] Ionic conductivity testing method: The diaphragm sample was obtained through the same disassembly, cleaning, and drying process described above. During testing, following GB / T 36363-2018 standard, the dried diaphragm was sandwiched between two stainless steel electrodes, and its impedance spectrum was measured using the AC impedance method (frequency range 1 MHz~1 Hz). The ionic conductivity (in S / cm) was calculated using the formula σ = L / (R × A), where L is the diaphragm thickness in cm and A is the electrode contact area in cm². 2R is the bulk resistance, expressed in Ω. The test results are shown in Table 2.

[0120] (ii) Battery assembly and performance testing

[0121] Battery Assembly: The separators prepared in all examples and comparative examples were assembled with positive electrode plates, negative electrode plates, and electrolytes according to the following method to obtain a pouch cell. The method includes:

[0122] 1) The positive electrode active material (specifically lithium cobalt oxide LiCoO2) was mixed with conductive carbon black and PVDF at a weight ratio of 96%:2%:2%, and dispersed to obtain a positive electrode slurry. This positive electrode slurry was then coated onto an aluminum foil current collector, with a positive electrode areal density of 4.12 g / cm³. 3 The positive electrode sheet is prepared by rolling.

[0123] 2) Artificial graphite, styrene-diene rubber (SBR), sodium carboxymethyl cellulose, and conductive carbon black are mixed in a weight ratio of 94%:3%:2%:1%. The mixture is dispersed in water and then mixed using a double planetary mixer to obtain a negative electrode slurry. This negative electrode slurry is coated onto a copper current collector, followed by rolling and drying to obtain a negative electrode sheet.

[0124] 3) Assemble the positive electrode, negative electrode, and separators from the above examples and comparative examples into lithium-ion batteries, and inject them with a non-aqueous electrolyte. The electrolyte is prepared by mixing ethylene carbonate (EC): diethyl carbonate (DEC): propylene carbonate (PC) in a mass ratio of 2:5:3. Then, add 5 wt% fluoroethylene carbonate (FEC), 13 wt% lithium hexafluorophosphate (LiPF6), and additive VC, with the additive content accounting for 2 wt% of the total electrolyte content.

[0125] Battery cycle capacity retention test method: The soft-pack batteries of the above examples and comparative examples were cycled for 500 cycles at 1C rate in an environment of 45℃±2℃. The test instrument was a battery formation and capacity cabinet. The discharge capacity of the first cycle and the last cycle were recorded. The capacity retention rate is the ratio of the discharge capacity of the last cycle to the discharge capacity of the first cycle. The test results are shown in Table 2.

[0126] Battery gas production test method: After the soft-pack batteries of the above examples and comparative examples were left to stand at 85℃±2℃ for 24 hours, the gas volume was directly measured using the water displacement gas collection method. The test results are shown in Table 2.

[0127] Battery thermal runaway temperature test method: The soft-pack batteries of the above embodiments and comparative examples were first heated to 100°C at a rate of 5°C / min, and then heated to 150°C at a rate of 1°C / min. The temperature at which fire or explosion occurred was recorded. The test results are shown in Table 2.

[0128]

[0129] As shown in Table 2, compared with the comparative example, the embodiments of the present invention, by setting a coating on the surface of the separator and making the coating include a polymer skeleton, lithium replenishing agent and unsaturated amino acid material, can improve the thermal stability and ionic conductivity of the separator, thereby improving the cycle performance and safety performance of the battery.

[0130] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A diaphragm, characterized in that, The coating includes a base film and a coating disposed on at least one surface of the base film, the coating comprising a polymer backbone and lithium supplementing agent and unsaturated amino acid material dispersed in the polymer backbone.

2. The diaphragm according to claim 1, characterized in that, The polymer skeleton includes polyamino acid materials and non-amino acid polymer fiber materials.

3. The diaphragm according to claim 2, characterized in that, The polyamino acid material includes structural units derived from the unsaturated amino acid material.

4. The diaphragm according to claim 2 or 3, characterized in that, The total mass ratio of the unsaturated amino acid material and the polyamino acid material to the mass ratio of the non-amino acid polymer fiber material is (0.02~1):1; And / or, the non-amino acid polymer fiber material accounts for 38wt%~85wt% of the mass percentage in the coating; And / or, the mass ratio of the lithium supplement to the non-amino acid polymer fiber material is (0.05-0.8):1; And / or, the mass percentage of the unsaturated amino acid material in the total mass of the unsaturated amino acid material and the polyamino acid material is less than or equal to 20 wt%.

5. The diaphragm according to any one of claims 2-4, characterized in that, The unsaturated amino acid materials include one or more of tryptophan, tryptophan derivatives, asparagine, asparagine derivatives, glutamine, and glutamine derivatives; And / or, the non-amino acid polymer fiber material includes one or more of the following: fluoropolymers, polyesters, cellulose, cellulose derivatives, polyolefins, polylactic acid, polyamides, polyimides, polyacrylonitrile, and polyethylene oxide; And / or, the lithium supplement includes at least one of organic lithium salts and inorganic lithium salts; The base film includes one or more materials selected from polyethylene and polypropylene.

6. The diaphragm according to claim 5, characterized in that, The inorganic lithium salt includes Li 1+a Al a Ti 2-a (PO4)3, Li 3b La 2 / 3-b TiO3, Li 6+2c La3Zr 2-c M c O 12 , lithium nitrate, lithium iodide, lithium bromide, lithium chloride, lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, or one or more thereof; wherein, 0.1 ≤ a ≤ 0.5, 0.04 ≤ b ≤ 0.16, 0 < c ≤ 0.6, and M is selected from one or more elements of Ta, Nb, and Al; The organic lithium salt includes one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium trifluoromethanesulfonate, lithium di(oxalate)borate, lithium di(fluorooxalate)borate, and lithium di(oxalate)phosphate.

7. A method for preparing the diaphragm according to any one of claims 1-6, characterized in that, Includes the following steps, A slurry comprising polymer backbone raw materials, lithium supplementer, and additives is coated onto at least one side surface of a base membrane, and the membrane is obtained after polymerization reaction. The polymer backbone material includes unsaturated amino acid materials.

8. The method for preparing the diaphragm according to claim 7, characterized in that, The slurry also includes non-amino acid polymer fiber materials; And / or, the auxiliary agent includes at least one of an initiator and a catalyst.

9. The method for preparing the diaphragm according to claim 8, characterized in that, The mass ratio of the initiator to the unsaturated amino acid material is (0.01% to 2%):1, preferably (0.2% to 1%):1; And / or, the reaction temperature of the polymerization reaction can be 40℃~85℃, and the reaction time can be 0.3h~18h.

10. The method for preparing the diaphragm according to claim 8 or 9, characterized in that, The initiator includes one or more of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, dilauryl peroxide, diethylhexyl percarbonate, cumene hydroperoxide, tert-butyl hydroperoxide, dodecyl peroxide, tert-butyl peroxide, tert-butyl peroxybenzoate, diisopropyl peroxide, potassium persulfate, or ammonium persulfate.

11. A battery, characterized in that, The membrane includes the membrane according to any one of claims 1-6, or the membrane prepared by the method for preparing the membrane according to any one of claims 7-10.

12. A battery pack, characterized in that, It includes at least two batteries as described in claim 11.

13. An electrical appliance, characterized in that, Includes the battery of claim 11, or the battery pack of claim 12.

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