Battery cell, battery and electrical device

Abstract

A battery cell, a battery and an electrical device. The battery cell comprises a positive electrode sheet, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer, the positive electrode active material layer is provided on the surface of the positive electrode current collector, and the positive electrode active material layer comprises polycarbodiimide. The moisture removal effect of the battery cell can meet production requirements without affecting the performance of the battery cell.

Description

A battery cell, a battery, and an electrical device. Cross-references to related applications

[0001] This application claims priority to Chinese Patent Application No. 202510005308.3, filed on January 2, 2025, entitled “A Battery Cell, Battery and Electrical Device”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of battery technology, and in particular to a battery cell, a battery, and an electrical device. Background Technology

[0003] In the process of preparing battery cells, moisture adsorbed from the air by the positive electrode material or positive electrode slurry may produce a series of chemical side reactions in the battery cell, thereby affecting the performance of the battery cell. Therefore, it is necessary to control the moisture in the positive electrode sheet during the preparation of battery cells.

[0004] In some proposed solutions, water-removing additives are added to the positive electrode slurry to absorb moisture from the positive electrode sheet. However, the water-removing effect of these additives may still not meet the production requirements of individual battery cells. Summary of the Invention

[0005] This application is made in view of the above-mentioned problems, and its purpose is to provide a battery cell, battery module, battery and electrical device that can meet the production requirements in terms of water removal effect without affecting the performance of the battery cell.

[0006] To achieve the above objectives, this application provides a battery cell, a battery module, a battery, and an electrical device.

[0007] A first aspect of this application provides a battery cell including a positive electrode sheet, wherein the positive electrode sheet includes: a positive current collector; a positive active material layer disposed on the surface of the positive current collector; wherein the positive active material layer comprises polycarbodiimide.

[0008] In this embodiment, the positive electrode active material layer contains polycarbodiimide. Using a macromolecular polymer as a dehydration additive results in better electrode dehydration, thereby improving the cycle life and storage performance of the battery cell. Furthermore, polycarbodiimide can continue to dehydrate under high-temperature conditions, thus shortening the electrode baking time for removing moisture from the positive electrode, thereby increasing the battery cell's capacity and reducing the negative impact of excessively long electrode baking time on battery cell performance. Simultaneously, using polycarbodiimide as a dehydration additive can also remove hydrofluoric acid from the battery cell electrolyte, thereby reducing acid-induced damage to the negative electrode SEI film, reducing the increase in battery cell internal resistance, stabilizing the negative electrode interface, and thus improving the battery cell's lifespan. It also reduces acid-induced damage to the positive and negative electrode materials and current collectors, improving the battery cell's reliability.

[0009] In any embodiment, the density D of the polycarbodiimide satisfies: 1.05 g / cm³. 3 ≤D≤1.15g / cm 3 When macromolecular polymers are used as dehydration additives, the additives have higher densities, resulting in better dehydration of the electrode and thus improving the cycle life and storage performance of the battery cells. Furthermore, when polycarbodiimide has a suitable density, it can have a higher softening point, thereby improving its dehydration efficiency against moisture inside the positive electrode.

[0010] In any embodiment, the viscosity V of the polycarbodiimide satisfies: 2200 mPa·s ≤ V ≤ 8000 mPa·s. When a macromolecular polymer is used as a dehydration additive, the dehydration additive has a higher viscosity, thereby achieving better dehydration of the electrode and improving the cycle life and storage performance of the battery cell. Furthermore, when the polycarbodiimide has a suitable viscosity, it can have a higher softening point, thereby improving its dehydration efficiency for moisture inside the positive electrode.

[0011] In any embodiment, the softening point S of the polycarbodiimide satisfies: 70℃≤S≤80℃. This reduces the reaction between the polycarbodiimide and moisture in the air before electrode baking, allowing the dehydration effect of the polycarbodiimide to act more effectively on the moisture inside the positive electrode during baking, thereby improving the dehydration efficiency of the polycarbodiimide on the moisture inside the positive electrode.

[0012] In any embodiment, the mass percentage M of the polycarbodiimide in the positive electrode active material layer satisfies: 0.05% ≤ M ≤ 0.5%. Because polycarbodiimide exhibits a dehydration effect under high-temperature conditions, it can achieve higher dehydration efficiency when targeting moisture inside the positive electrode sheet. Therefore, under the same dehydration requirements, the amount of polycarbodiimide applied in the positive electrode active material layer can be lower, thereby reducing the load on the positive electrode sheet and improving the performance of the battery cell.

[0013] Optionally, the mass percentage M of the polycarbodiimide in the positive electrode active material layer satisfies: 0.1% ≤ M ≤ 0.3%. When the amount of polycarbodiimide applied in the positive electrode active material layer is within a suitable range, the positive electrode can have a smaller load while meeting the requirements for electrode dehydration, thereby enabling the battery cell to have better battery cell performance.

[0014] In any embodiment, the positive electrode active material layer includes a positive electrode active material, which includes one or more of lithium transition metal oxides, lithium iron phosphate, and lithium manganese iron phosphate. For battery cell applications with high surface residual alkali and large specific surface area that are sensitive to water, polycarbodiimide can have better electrode dewatering effect, removing trace amounts of water from the positive electrode, reducing the reaction between water and surface residual alkali and other impurities in materials with large specific surface area, improving gas generation in the battery cell system, and enhancing the reliability of the battery cell's life cycle.

[0015] In any embodiment, the positive electrode active material layer includes at least one of the following: diisocyanate, triisocyanate, and polyisocyanate. When the positive electrode active material layer contains a component that can undergo a condensation reaction to produce linear polycarbodiimide or polycarbodiimide with a branched structure as a dehydration additive, it can produce effects similar to those of the aforementioned polycarbodiimide.

[0016] A second aspect of this application provides a battery module including the battery cell of the first aspect of this application.

[0017] A third aspect of this application provides a battery, including a battery cell of the first aspect of this application and / or a battery module of the second aspect.

[0018] A fourth aspect of this application provides an electrical device comprising at least one selected from the battery cell of the first aspect of this application, the battery module of the second aspect of this application, or the battery of the third aspect of this application. Attached Figure Description

[0019] Figure 1 is a schematic diagram of the positive electrode sheet according to an embodiment of this application.

[0020] Figure 2 is a schematic diagram of a battery cell according to one embodiment of this application.

[0021] Figure 3 is a schematic diagram of a battery module according to one embodiment of this application.

[0022] Figure 4 is a schematic diagram of a battery according to one embodiment of this application.

[0023] Figure 5 is an exploded view of the battery according to one embodiment of this application, as shown in Figure 4.

[0024] Figure 6 is a schematic diagram of an electrical device in which a single battery cell is used as a power source according to an embodiment of this application.

[0025] Figure 7 is a schematic diagram of the 25°C cycle performance test results in Example 1 and Comparative Example 1 of this application.

[0026] Figure 8 is a schematic diagram of the 25°C cycle performance test results in Comparative Examples 1 and 2 of this application.

[0027] Figure 9 is a schematic diagram of the 60°C high-temperature storage performance test results in Embodiment 1 and Comparative Example 1 of this application.

[0028] Figure 10 is a schematic diagram of the 60℃ high-temperature storage performance test results in Comparative Examples 1 and 2 of this application.

[0029] Explanation of reference numerals in the attached figures:

[0030] 1 Battery; 2 Upper casing; 3 Lower casing; 4 Battery module; 5 Battery cell; 6 Positive electrode sheet; 61 Positive current collector; 62 Positive active material layer. Detailed Implementation

[0031] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the electrode plates, battery cells, battery modules, batteries, and power-consuming devices 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.

[0032] 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.

[0033] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0034] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0035] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates 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.

[0036] The development of battery technology requires consideration of multiple design factors, such as electrode materials and cell performance. With the widespread use of batteries, the production requirements for battery electrodes are gradually increasing. During its research on the cell manufacturing process, the applicant discovered that moisture absorbed from the air by the positive electrode material or slurry can trigger a series of chemical side reactions within the cell, thereby affecting its performance. Therefore, it is necessary to control the moisture content within the positive electrode during cell manufacturing.

[0037] In some related technologies, water-removing additives are added to the positive electrode slurry to absorb moisture from the positive electrode sheet. However, the water-removing effect of these additives may still not meet the production requirements of individual battery cells.

[0038] In view of this, this application provides a battery cell including a positive electrode sheet, wherein the positive electrode sheet includes: a positive current collector; and a positive active material layer disposed on the surface of the positive current collector; wherein the positive active material layer comprises polycarbodiimide. This allows the water removal effect of the battery cell to meet production requirements without affecting the battery cell's performance.

[0039] [Battery cell]

[0040] In one embodiment of this application, a battery cell 5 is provided. The battery cell 5 includes a positive electrode 6.

[0041] Figure 1 is a schematic diagram of the structure of the positive electrode 6 according to an embodiment of this application. The positive electrode 6 includes a positive current collector 61 and a positive active material layer 62. The positive active material layer 62 is disposed on the surface of the positive current collector 61, wherein the positive active material layer 62 contains polycarbodiimide.

[0042] In one possible scenario, polycarbodiimide has a linear polymer structure. For example, polycarbodiimide may have the following chemical formula:

[0043]

[0044] Where n is a positive integer.

[0045] Another possible scenario is that polycarbodiimide can also be a polymer structure with a branched chain.

[0046] As an example, the polycarbodiimide in the positive electrode active material layer 62 can be a polycarbodiimide with a linear polymer structure, or a polycarbodiimide with a branched polymer structure, or it can simultaneously contain both a polycarbodiimide with a linear polymer structure and a polycarbodiimide with a branched polymer structure. This application does not limit the specific types of polycarbodiimides.

[0047] In this embodiment, the positive electrode active material layer 62 of the positive electrode 6 contains polycarbodiimide. Using a macromolecular polymer as a dehydration additive results in better electrode dehydration, thereby improving the cycle life and storage performance of the battery cell 5. Furthermore, polycarbodiimide can continue to dehydrate under high-temperature conditions, thus shortening the electrode baking time for removing moisture from the positive electrode 6, thereby increasing the battery cell's capacity and reducing the negative impact of excessively long electrode baking time on the battery cell's performance. Simultaneously, using polycarbodiimide as a dehydration additive can also remove hydrofluoric acid from the electrolyte of the battery cell 5, thereby reducing acid-induced damage to the negative electrode SEI film, reducing the increase in internal resistance of the battery cell 5, stabilizing the negative electrode interface, and thus improving the battery cell's lifespan. It also reduces acid-induced damage to the positive and negative electrode materials and current collectors, improving the reliability of the battery cell 5.

[0048] In some embodiments, the density D of the polycarbodiimide satisfies: 1.05 g / cm³. 3 ≤D≤1.15g / cm 3 .

[0049] D can be 1.05 g / cm³ 3 1.07 g / cm 3 1.09 g / cm 3 1.11 g / cm 3 1.13 g / cm³, 1.15 g / cm³ 3 Or any value within the above range.

[0050] When macromolecular polymers are used as dehydration additives, the additives have higher densities, resulting in better dehydration of the electrode and thus improving the cycle life and storage performance of the battery cell 5. Furthermore, when polycarbodiimide has a suitable density, it can have a higher softening point, thereby improving its dehydration efficiency for the internal moisture of the positive electrode 6.

[0051] In some embodiments, the viscosity V of polycarbodiimide satisfies: 2200 mPa·s ≤ V ≤ 8000 mPa·s.

[0052] V can be 2200 mPa·s, 2500 mPa·s, 3000 mPa·s, 3500 mPa·s, 4000 mPa·s, 4500 mPa·s, 5000 mPa·s, 5500 mPa·s, 6000 mPa·s, 6500 mPa·s, 7000 mPa·s, 7500 mPa·s, 8000 mPa·s, or any value within the above range.

[0053] When macromolecular polymers are used as dehydration additives, the additives have higher viscosity, resulting in better dehydration of the electrode and thus improving the cycle life and storage performance of the battery cell 5. Furthermore, when polycarbodiimide has a suitable viscosity, it can have a higher softening point, thereby improving its dehydration efficiency for the internal moisture of the positive electrode 6.

[0054] In some embodiments, the softening point S of polycarbodiimide satisfies: 70℃≤S≤80℃.

[0055] S can be 70℃, 72℃, 74℃, 76℃, 78℃, 80℃ or any value within the above range.

[0056] This reduces the reaction between polycarbodiimide and moisture in the air before the electrode is baked, allowing the dehydration effect of polycarbodiimide to act more effectively on the moisture inside the positive electrode 6 during baking, thereby improving the dehydration efficiency of polycarbodiimide on the moisture inside the positive electrode 6.

[0057] In some embodiments, the mass percentage M of polycarbodiimide in the positive electrode active material layer 62 satisfies: 0.05% ≤ M ≤ 0.5%.

[0058] M can be 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, or any value within the above range.

[0059] Because polycarbodiimide has a dehydration effect under high temperature conditions, it can achieve higher dehydration efficiency when targeting moisture inside the positive electrode 6. Therefore, under the same dehydration requirement, the amount of polycarbodiimide applied in the positive electrode active material layer 62 can be lower, thereby reducing the load on the positive electrode 6 and improving the performance of the battery cell 5.

[0060] Optionally, the mass percentage M of polycarbodiimide in the positive electrode active material layer 62 satisfies: 0.1% ≤ M ≤ 0.3%.

[0061] When the amount of polycarbodiimide applied in the positive electrode active material layer 62 is within a suitable range, the positive electrode 6 can have a smaller load while meeting the requirements for dehydration of the electrode, thereby enabling the battery cell 5 to have better battery cell performance.

[0062] In some embodiments, the positive electrode active material layer 62 includes a positive electrode active material, which includes one or more of lithium transition metal oxides, lithium iron phosphate, and lithium manganese iron phosphate.

[0063] For battery cell applications with high surface alkali residue and high water sensitivity, polycarbodiimide can have better electrode dewatering effect, remove trace amounts of water from the positive electrode, reduce the reaction between water and impurities such as surface alkali residue in materials with high surface area, improve gas generation in the battery cell system, and improve the reliability of the battery cell's 5-year life cycle.

[0064] In some embodiments, the positive electrode active material layer 62 includes at least one of the following: diisocyanate, triisocyanate, or polyisocyanate.

[0065] When the positive electrode active material layer 62 contains a component that can undergo a condensation reaction to produce linear polycarbodiimide or polycarbodiimide with a branched structure as a dehydration additive, it can produce effects similar to those of the aforementioned polycarbodiimide.

[0066] In addition, the battery cell, battery module, battery and power device of this application will be described below with appropriate reference to the accompanying drawings.

[0067] Typically, a battery cell includes a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0068] [Positive electrode plate]

[0069] The positive electrode can be the aforementioned positive electrode 6.

[0070] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0071] In some embodiments, the positive electrode active material layer may employ positive electrode active materials known in the art for use in batteries. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, 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 transition metal oxides 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 NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, 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.

[0072] In some embodiments, the positive electrode active material layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0073] In some embodiments, the positive electrode active material layer may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0074] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, polycarbodiimide, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0075] [Negative electrode plate]

[0076] The negative electrode includes a negative current collector and a negative electrode film layer disposed on the negative current collector.

[0077] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. The negative electrode current collector may be copper foil. The composite negative electrode current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0078] In some embodiments, the negative electrode film layer includes a negative electrode active material. The negative electrode active material may be any negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material may be selected from one or more of elemental silicon, silicon-oxygen compounds, silicon-carbon compounds, silicon-nitrogen compounds, and silicon alloys. The tin-based material may be selected from one or more of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0079] In some embodiments, the negative electrode film layer may optionally include a binder. As an example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0080] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0081] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0082] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode film, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0083] [Electrolytes]

[0084] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0085] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0086] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0087] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0088] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0089] [Isolation membrane]

[0090] In some embodiments, the battery cell also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0091] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0092] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0093] In some embodiments, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0094] In some embodiments, the outer packaging of the battery cell can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. 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; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0095] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 2 shows an example battery cell 5, which may include a housing. The positive electrode, negative electrode, and separator can be formed into an electrode assembly using a winding or stacking process. The electrode assembly is encapsulated within the housing. Electrolyte is immersed in the electrode assembly. The battery cell 5 can contain one or more electrode assemblies, which can be selected by those skilled in the art according to specific practical needs.

[0096] In some implementations, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0097] Figure 3 shows a battery module 4 as an example. Referring to Figure 3, in the battery module 4, multiple battery cells 5 can be arranged sequentially along the length of the battery module 4. Of course, they can also be arranged in any other manner. Furthermore, the multiple battery cells 5 can be fixed in place using fasteners.

[0098] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0099] In some embodiments, the battery modules described above can also be assembled into a battery. The number of battery modules contained in the battery can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery.

[0100] Figures 4 and 5 illustrate a battery 1 as an example. Referring to Figures 4 and 5, the battery 1 may include a battery case and multiple battery modules 4 disposed within the battery case. The battery case includes an upper casing 2 and a lower casing 3, with the upper casing 2 covering the lower casing 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery case.

[0101] In addition, this application also provides an electrical device, which includes at least one of the battery cell, battery module, or battery provided in this application. The battery cell, battery module, or battery can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., 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.

[0102] As the electrical device, a single battery cell, a battery module, or a battery can be selected according to its usage requirements.

[0103] Figure 6 shows an example of an electrical device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the battery cells in this device, batteries or battery modules can be used.

[0104] Another example 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.

[0105] [Example]

[0106] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0107] Example 1

[0108] (1) Preparation of negative electrode sheet

[0109] The negative electrode active material graphite, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener / dispersant sodium carboxymethyl cellulose (CMC-Na) are dissolved in deionized water at a mass ratio of 96.0:1:2:1 and thoroughly mixed to prepare a negative electrode slurry. The negative electrode slurry is coated onto the negative electrode current collector copper foil, and then dried, cold-pressed, and slit to obtain the negative electrode sheet.

[0110] (2) Preparation of positive electrode sheet

[0111] Positive electrode active material Li 1.2 Ni 0.2 Mn 0.6 O2, polycarbodiimide, polyvinylidene fluoride (PVDF) binder, and acetylene black conductive agent are dry-mixed in a mass ratio of 96.7:0.3:1.5:1.5. Then, N-methylpyrrolidone (NMP) solvent is added and the mixture is stirred thoroughly to prepare a positive electrode slurry. The positive electrode slurry is uniformly coated on the positive electrode current collector aluminum foil, and then dried, cold-pressed, and slit to obtain the positive electrode sheet.

[0112] (3) Separating membrane

[0113] PE film was selected as the separator, and CCS coating was used.

[0114] (4) Electrolyte

[0115] Ethyl carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1, and then LiPF6 was uniformly dissolved in the above solution at a concentration of 1 mol / L to obtain the electrolyte.

[0116] (5) Preparation of battery cells

[0117] The positive electrode, separator, and negative electrode are stacked in sequence to obtain a soft-pack stacked cell; the cell is placed in a pre-cut aluminum-plastic bag, the electrolyte prepared above is added, and it is sealed. After high-temperature standing, formation, aging, capacity measurement, and k-value measurement, a single battery cell is obtained.

[0118] Examples 2-5

[0119] The difference between Examples 2-5 and Example 1 is that the mass percentage of polycarbodiimide in the positive electrode active material layer is different.

[0120] Examples 6-7

[0121] The difference between Examples 6-7 and Example 1 is that the positive electrode active material in the positive electrode active material layer is different.

[0122] Comparative Example 1

[0123] The difference between Comparative Example 1 and Example 1 is that no polycarbodiimide was added to the positive electrode active material layer.

[0124] Comparative Example 2

[0125] The difference between Comparative Example 2 and Example 1 is that the components of the positive electrode active material layer are different.

[0126] Comparative Example 3

[0127] The difference between Comparative Example 3 and Example 5 is that the components of the positive electrode active material layer are different.

[0128] Comparative Example 4

[0129] The difference between Comparative Example 4 and Example 6 is that no polycarbodiimide was added to the positive electrode active material layer.

[0130] Comparative Example 5

[0131] The difference between Comparative Example 5 and Example 7 is that no polycarbodiimide was added to the positive electrode active material layer.

[0132] The specific parameters of the battery cells in Examples 1-7 and Comparative Examples 1-5 are shown in Table 1 below.

[0133] Table 1: Specific parameters of Examples 1-7 and Comparative Examples 1-5

[0134] In addition, the battery cells in Examples 1-7 and Comparative Examples 1-5 were subjected to performance tests. The test results are shown in Tables 2 and 3 and Figures 7 to 10 below. In Figures 7 to 10, "base" represents Comparative Example 1, "0.3% CH-1" represents Comparative Example 2, and "0.3% CH-2" represents Example 1.

[0135] Table 2: Performance test results of Examples 1-7 and Comparative Examples 1-5

[0136] Table 3: Performance test results of Examples 1-3, 5 and Comparative Examples 1-2

[0137] [Testing methods for individual battery cell parameters]

[0138] (1) Test of water content of positive electrode sheet

[0139] Take a positive electrode sample and measure the moisture content directly using an AKF-CH6 Karl Fischer analyzer.

[0140] (2) Testing of the 25℃ cycle performance of individual battery cells

[0141] At 25°C, the prepared battery was charged at a constant current of 0.5C to the upper limit cutoff voltage of 4.4V, then charged at a constant voltage of 4.4V until the current ≤0.05C, rested for 5 minutes, and then discharged at 0.5C to 2.5V. The resulting capacity was recorded as the initial capacity C0. The above steps were repeated for the same battery, and the discharge capacity C of the battery after the nth cycle was recorded. n Then, the battery capacity retention rate P after each cycle n =C n / C0×100%, with battery capacity retention rate on the ordinate and the corresponding number of cycles on the abscissa, a curve of battery capacity retention rate versus number of cycles is obtained.

[0142] (3) Testing of the storage performance of individual battery cells at 60℃

[0143] ① Charge the prepared battery cells at a constant current of 1 / 3C to 4.4V, then charge at a constant voltage of 4.4V until the current ≤0.05C, let stand for 5 minutes, and then discharge at 1 / 3C to 2.5V. Repeat this process twice, and record the discharge capacity D0 of the second discharge. ② Charge the battery cells at a constant current of 1 / 3C to 4.4V, then charge at a constant voltage of 4.4V until the current ≤0.05C, and then store them in a constant temperature environment at 60℃ for a specified number of days. ③ Discharge at 1 / 3C to 2.5V, let stand for 5 minutes, then charge at a constant voltage of 4.4V until the current ≤0.05C, let stand for 5 minutes, and then discharge at 1 / 3C to 2.5V. Record the capacity as D. n D n Divide by the value of D0 to obtain the degree of cell degradation on day n of high-temperature storage; ④: Repeat steps ② and ③ until the cell storage life degradation is recorded.

[0144] (4) Testing the softening point of the component substances

[0145] Under constant rate heating conditions, a wire with a specified load and a cross-sectional area of ​​1 mm² is used. 2 The flat-top needle is placed on the component material sample. The temperature at which the flat-top needle penetrates 1 mm into the component material sample is the measured softening point temperature.

[0146] Referring to Examples 1-5 in Table 2 and Comparative Example 1, when polycarbodiimide components with a mass percentage of 0.05%, 0.1%, 0.3%, 0.5%, and 1.0% were added to the positive active material layer of the positive electrode sheets in Examples 1-5, the moisture content of the positive electrode sheets after baking for 12 hours and 24 hours was lower than that of the positive electrode sheet in Comparative Example 1 without the addition of a dehydrating additive. This demonstrates that polycarbodiimide, when added as a dehydrating additive to the positive active material layer of the positive electrode sheet, has a good effect on removing moisture from the positive electrode sheet. Furthermore, referring to Table 3 and Figure 7, Example 1... The battery cells in Example 1-3 exhibited higher capacity retention rates at 25°C after 400 cycles compared to those in Comparative Example 1, demonstrating that polycarbodiimide, when added as a dehydration additive to the positive electrode active material layer, effectively improves the cycle life of the battery cells. Furthermore, as shown in Table 3 and Figure 9, the battery cells in Examples 1-3 also showed higher capacity retention rates at 60°C after 60 days compared to those in Comparative Example 1, further demonstrating that polycarbodiimide, when added as a dehydration additive to the positive electrode active material layer, also effectively improves the storage performance of the battery cells.

[0147] As shown in Table 2, Examples 1 and 3 and Comparative Examples 2 and 3, compared with Examples 1 and 3, when the positive electrode active material layer in Comparative Examples 2 and 3 is supplemented with the monomeric carbodiimide component, the electrode moisture content of the positive electrode in Comparative Examples 2 and 3 after baking for 12 hours and 24 hours is higher than that of the positive electrode in Examples 1 and 3 using polycarbodiimide as a dehydration additive. This proves that when a macromolecular polymer is used as a dehydration additive, it can have a better dehydration effect on the electrode, thereby improving the cycle life and storage performance of the battery cell. Furthermore, as shown in Table 3 and Figures 7 and 8, compared to Example 1, the battery capacity retention rate of the battery cell in Comparative Example 2 at 25°C was consistently lower than that of Comparative Example 1 after the start of cycling. This indirectly shows that the battery capacity retention rate of Comparative Example 2 was consistently lower than that of Example 1, thus proving that using macromolecular polymers as dehydration additives also has a good effect on improving the cycle life of battery cells. At the same time, as shown in Table 3 and Figures 9 and 10, the battery capacity retention rate of the battery cell in Example 1 at 60°C high-temperature storage after 60 days was also higher than that of Comparative Example 2, thus proving that using macromolecular polymers as dehydration additives added to the positive electrode active material layer of the positive electrode sheet also has a good effect on improving the storage performance of battery cells.

[0148] Referring to Examples 1-5 in Table 2, when the density D of polycarbodiimide satisfies 1.05 g / cm³... 3 ≤D≤1.15g / cm 3 When the softening point S of polycarbodiimide is 70℃≤S≤80℃, the reaction between polycarbodiimide and moisture in the air before the electrode is baked can be reduced. This allows the dehydration effect of polycarbodiimide to act more on the moisture inside the positive electrode during baking, thereby improving the dehydration efficiency of polycarbodiimide on the moisture inside the positive electrode.

[0149] As shown in Examples 1-5 in Table 2, when the viscosity V of polycarbodiimide satisfies 2200 mPa·s ≤ V ≤ 8000 mPa·s, the softening point S of polycarbodiimide can satisfy 70℃ ≤ S ≤ 80℃. This can reduce the reaction between polycarbodiimide and moisture in the air before the electrode is baked, so that the dehydration effect of polycarbodiimide can act more on the moisture inside the positive electrode during baking, thereby improving the dehydration efficiency of polycarbodiimide on the moisture inside the positive electrode.

[0150] Referring to Examples 1-5 in Table 2, the mass percentage of polycarbodiimide in the positive electrode active material layer is 0.3% in Example 1 and 1.0% in Example 5. The difference in moisture content of the positive electrode sheets after baking between Examples 1 and 5 is very small. This demonstrates that under similar electrode dehydration requirements, the mass percentage of polycarbodiimide in the positive electrode active material layer can be as low as 0.05%-0.5%, thereby reducing the load on the positive electrode sheet and improving the performance of the battery cell. Preferably, referring to Examples 1-5, when the mass percentage of polycarbodiimide in the positive electrode active material layer is further limited to 0.1%-0.3%, the positive electrode sheet can have a smaller load while meeting the electrode dehydration requirements, thus enabling the battery cell to have better performance.

[0151] Referring to Example 1 and Comparative Example 1 in Table 2, when the positive electrode active material is Li 1.2 Ni 0.2 Mn 0.6 In the application scenario of O2 battery cells, when polycarbodiimide is added to the positive electrode active material layer of the positive electrode sheet, Example 1 has a lower electrode water content compared to the positive electrode sheet without polycarbodiimide in Comparative Example 1. This proves that polycarbodiimide, when added as a dehydration additive to the positive electrode active material Li... 1.2 Ni 0.2 Mn 0.6 When removing the positive electrode active material layer of O2, for positive electrode active material of Li 1.2Ni 0.2 Mn 0.6 O2 has a good effect on the moisture in the positive electrode of a battery cell.

[0152] As shown in Table 2, Example 6 and Comparative Example 4 demonstrate that in the application scenario of battery cells with lithium iron phosphate as the positive electrode active material, when polycarbodiimide is added to the positive electrode active material layer of the positive electrode sheet, Example 6 has a lower electrode sheet water content compared to the positive electrode sheet without polycarbodiimide in Comparative Example 4. This proves that polycarbodiimide, when added as a dehydration additive to the positive electrode active material layer of lithium iron phosphate as the positive electrode active material, has a good effect on removing moisture from the positive electrode sheet of battery cells with lithium iron phosphate as the positive electrode active material.

[0153] Referring to Example 7 and Comparative Example 5 in Table 2, when the positive electrode active material is lithium iron manganese phosphate + LiNi 0.5 Co 0.2 Mn 0.3 In the application scenario of O2 battery cells, when polycarbodiimide is added to the positive electrode active material layer of the positive electrode sheet, Example 7 has a lower electrode water content compared to the positive electrode sheet without polycarbodiimide in Comparative Example 5. This proves that polycarbodiimide, when added as a dehydration additive to the positive electrode active material of lithium iron manganese phosphate + LiNi, can effectively remove water. 0.5 Co 0.2 Mn 0.3 When removing the positive electrode active material layer of O2, for positive electrode active materials of lithium iron manganese phosphate + LiNi 0.5 Co 0.2 Mn 0.3 O2 has a good effect on the moisture in the positive electrode of a battery cell.

[0154] 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, Includes a positive electrode plate, wherein the positive electrode plate comprises: Positive current collector; A positive electrode active material layer is disposed on the surface of the positive electrode current collector; The positive electrode active material layer contains polycarbodiimide.

2. The battery cell according to claim 1, characterized in that, The density D of the polycarbodiimide satisfies: 1.05 g / cm³ 3 ≤D≤1.15g / cm 3 .

3. The battery cell according to claim 1 or 2, characterized in that, The viscosity V of the polycarbodiimide satisfies: 2200 mPa·s ≤ V ≤ 8000 mPa·s.

4. The battery cell according to any one of claims 1-3, characterized in that, The softening point S of the polycarbodiimide satisfies: 70℃≤S≤80℃.

5. The battery cell according to any one of claims 1-4, characterized in that, The mass percentage M of the polycarbodiimide in the positive electrode active material layer satisfies: 0.05% ≤ M ≤ 0.5%.

6. The battery cell according to claim 5, characterized in that, The mass percentage M of the polycarbodiimide in the positive electrode active material layer satisfies: 0.1% ≤ M ≤ 0.3%.

7. The battery cell according to any one of claims 1-6, characterized in that, The positive electrode active material layer includes a positive electrode active material, which includes one or more of lithium transition metal oxides, lithium iron phosphate, and lithium manganese iron phosphate.

8. A battery, characterized in that, Includes the battery cell according to any one of claims 1-7.

9. An electrical device, characterized in that, It includes at least one of the battery cells selected from any one of claims 1-7 or the battery described in claim 8.

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