Lithium ion battery monomer, lithium ion battery and power utilization device

Abstract

The invention provides a lithium ion battery monomer, a lithium ion battery and a power utilization device. The lithium ion battery monomer comprises a positive pole piece, an isolating membrane and a negative pole piece, the isolating membrane is located between the positive pole piece and the negative pole piece, the isolating membrane comprises a base material and a coating located on the surface of the base material, and the coating comprises a redox agent. And the redox potential of the redox agent is between the positive potential and the negative potential of the lithium ion battery monomer at the charging upper limit. The coating containing the redox agent is arranged on the surface of the base material of the isolating membrane of the single lithium ion battery, and an oxidation product generated at the positive pole piece can be reduced at the isolating membrane through the redox agent, so that the amount of the oxidation product transferred to the negative pole piece can be reduced, the consumption of active lithium ions is reduced, and the service life of the lithium ion battery is prolonged. And the storage performance of the lithium ion battery is improved.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a lithium-ion battery cell, a lithium-ion battery, and an electrical device. Background Technology

[0002] Lithium-ion batteries are widely used in energy storage systems for hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric cars, military equipment, aerospace, and many other fields. With the increasing adoption of lithium-ion batteries, consumers are placing higher demands on their performance. For example, the storage performance of lithium-ion batteries needs further improvement. Summary of the Invention

[0003] The first aspect of this application provides a lithium-ion battery cell, including a positive electrode, a separator, and a negative electrode. The separator is located between the positive electrode and the negative electrode. The separator includes a substrate and a coating on the surface of the substrate. The coating contains an oxidizing agent, and the oxidizing-reduction potential of the oxidizing agent is located between the positive potential and the negative potential of the lithium-ion battery cell at the upper limit of charging.

[0004] In the aforementioned lithium-ion battery cell, a coating containing an oxidizing agent is provided on the surface of the separator substrate. Since the oxidizing-reduction potential of the oxidizing agent is located between the positive and negative electrode potentials of the lithium-ion battery at the upper limit of charging, the oxidation products generated at the positive electrode can be reduced at the separator by the oxidizing agent. This reduces the amount of oxidation products transferred to the negative electrode and reduces the consumption of active lithium ions, thus improving the storage performance of the lithium-ion battery.

[0005] In some embodiments, the redox potential of the redox agent is 1V-4.75V. This redox potential range allows for better compatibility with lithium-ion battery cells across various voltage ranges, enabling more reduction of oxidation products generated at the positive electrode at the separator, reducing the amount of oxidation products transferred to the negative electrode, and further improving the storage performance of the battery cell.

[0006] In some embodiments, the redox agents include Li5FeO4, Li2NiO2, Li6CoO4, Li2CuO2, Li2MoO2, Li5ReO6, Li2O, Li2O2, Li2S, LiCoO2, LiMn2O4, Li2MnO3, LiFePO4, LiMnFePO4, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and Li4Ti5O. 12 And one or more of TiNb2O7.

[0007] In some embodiments, the redox agent constitutes 50% to 98% of the coating by mass. Within this range, the redox agent's role is fully realized, further promoting the improvement of the battery cell's storage performance.

[0008] In some embodiments, the coating further comprises an adhesive. The adhesive can maintain good adhesion between the coating and the substrate, which helps to maintain a stable structure of the release liner.

[0009] In some embodiments, the binder constitutes 2%-50% of the coating by mass. This binder content allows for maintaining a suitable mass of redox agents in the coating, ensuring both a stable structure and good redox properties in the release liner.

[0010] In some embodiments, the adhesive includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, styrene-acrylic latex, styrene-butadiene rubber, polymethyl methacrylate, polybutyl methacrylate, polyvinylpyrrolidone, polyethylene oxide, polyvinyl alcohol, and sodium carboxymethyl cellulose.

[0011] In some embodiments, the coating further comprises a conductive agent. The conductive agent enhances the electronic conductivity between coating particles and improves reaction kinetics.

[0012] In some embodiments, the conductive agent accounts for 0.01%-5% of the coating by mass.

[0013] In some embodiments, the conductive agent includes one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0014] In some embodiments, the coating includes a first coating disposed on a surface of the substrate and located between the positive electrode and the substrate. The redox agent includes a first redox agent, and the first coating contains the first redox agent. The redox potential of the first redox agent is 2V-4.75V. The first coating, located between the positive electrode and the substrate and containing the first redox agent, allows oxidation products generated by the positive electrode to be reduced more quickly at the first coating, further reducing the amount of oxidation products transferred to the negative electrode, further reducing the consumption of active lithium ions, and thus improving the storage performance of the lithium-ion battery cell.

[0015] In some embodiments, the first redox agent includes one or more of Li5FeO4, Li2NiO2, Li6CoO4, Li2CuO2, Li2MoO2, Li5ReO6, Li2O, Li2O2, Li2S, LiCoO2, LiMn2O4, Li2MnO3, LiFePO4, LiMnFePO4, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

[0016] In some embodiments, the first oxidizing agent accounts for 50%-98% of the mass percentage of the first coating. Within this range, the first oxidizing agent can fully exert its function and further promote the improvement of the battery cell's storage performance.

[0017] In some embodiments, the thickness of the first coating is 0.1 μm-100 μm. A thickness within this range allows the separator to maintain a suitable thickness, thereby enabling the battery cell to maintain a high energy density. Optionally, the thickness of the first coating is 3 μm-50 μm. More preferably, the thickness of the first coating is 10 μm-15 μm.

[0018] In some embodiments, the lithium-ion battery cell further includes a first porous insulating film located between the positive electrode and the first coating. The presence of the first porous insulating film reduces the risk of direct contact between the positive electrode active material and the first oxidizing agent, decreases the occurrence of side reactions in the battery cell, and further improves the storage performance of the battery cell.

[0019] In some embodiments, the material of the first porous insulating film includes one or more of polyethylene, polypropylene, polyvinylidene fluoride, glass fiber, nonwoven fabric, and ceramics.

[0020] In some embodiments, the thickness of the first porous insulating film is 5 μm-15 μm.

[0021] In some embodiments, the coating includes a second coating disposed on a surface of the substrate and located between the negative electrode and the substrate. The redox agent includes a second redox agent, and the second coating contains the second redox agent. The redox potential of the second redox agent is 1V-2V. The second coating, located between the negative electrode and the substrate and containing the second redox agent, can oxidize the reduction products at the negative electrode, reducing the interaction between the positive and negative electrodes and thus further improving the cycle performance of the battery cell.

[0022] In some embodiments, the second redox agent includes Li4Ti5O12 One or more of TiNb2O7.

[0023] In some embodiments, the second oxidizing agent accounts for 50%-98% of the mass percentage of the second coating. Within this range, the second oxidizing agent can fully exert its effect, further promoting the improvement of the battery cell's storage performance.

[0024] In some embodiments, the thickness of the second coating is 0.1 μm-100 μm. A thickness within this range allows the separator to maintain a suitable thickness, thereby enabling the battery cell to maintain a high energy density. Optionally, the thickness of the second coating is 3 μm-50 μm. More preferably, the thickness of the second coating is 10 μm-15 μm.

[0025] In some embodiments, the lithium-ion battery cell further includes a second porous insulating film located between the negative electrode sheet and the second coating. The presence of the second porous insulating film reduces the risk of direct contact between the negative electrode active material and the second redox agent, decreases the occurrence of side reactions in the battery cell, and further improves the storage performance of the battery cell.

[0026] In some embodiments, the material of the second porous insulating film includes one or more of polyethylene, polypropylene, polyvinylidene fluoride, glass fiber, nonwoven fabric, and ceramics.

[0027] In some embodiments, the thickness of the second porous insulating film is 5 μm-15 μm.

[0028] In some embodiments, the positive electrode potential of the lithium-ion battery cell at the upper limit of charging is 4V-4.8V. At this point, the positive electrode potential is relatively high, which is beneficial for improving the energy density of the battery cell.

[0029] In some embodiments, the positive electrode sheet includes a positive current collector and a positive active layer disposed on at least one surface of the positive current collector, the positive active layer including a positive active material, the positive active material including one or more of lithium nickel manganese oxide, lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide.

[0030] In some embodiments, the lithium-ion battery cell further includes an electrolyte comprising an electrolyte salt and a solvent, wherein the solvent comprises one or more of methyltrifluoroethyl carbonate and fluoroethylene carbonate. Methyltrifluoroethyl carbonate and fluoroethylene carbonate have good oxidation resistance, which can help maintain good stability of the electrolyte when the battery cell voltage is high, further improving the performance of the battery cell.

[0031] In some embodiments, the solvent comprises the methyltrifluoroethyl carbonate and the fluoroethylene carbonate, wherein the volume ratio of the methyltrifluoroethyl carbonate to the fluoroethylene carbonate is (6-8):(2-4). This volume ratio of methyltrifluoroethyl carbonate to fluoroethylene carbonate within this range allows the electrolyte to exhibit better high-voltage stability, which is beneficial for further improving the performance of individual battery cells.

[0032] A second aspect of this application provides a lithium-ion battery. The lithium-ion battery includes the lithium-ion battery cell.

[0033] A third aspect of this application provides an electrical device. The electrical device includes the lithium-ion battery. Attached Figure Description

[0034] To better describe and illustrate the embodiments or examples provided in this application, reference may be made to one or more accompanying drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed applications, the currently described embodiments or examples, or the best mode of conduct of these applications as currently understood. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0035] Figure 1 This is a schematic diagram of a battery cell according to one embodiment of this application.

[0036] Figure 2 for Figure 1 An exploded view of a battery cell according to one embodiment of this application is shown.

[0037] Figure 3 This is a schematic diagram of an electrical device in which a single battery cell is used as a power source according to one embodiment of this application.

[0038] Figure 4 The graphs show the capacity retention rate of individual cells in Examples 1-2 and Comparative Example 1 of this application as a function of storage time.

[0039] Figure 5 This is a comparison chart of the gas production of individual cells in Examples 1-2 and Comparative Example 1 after 40 days of storage.

[0040] Figure 6 This is a comparative graph showing the composition of gases generated by storing individual battery cells of Examples 1-2 and Comparative Example 1 for 40 days.

[0041] Explanation of reference numerals in the attached figures:

[0042] 1. Battery cell; 11. Casing; 12. Electrode assembly; 13. Cover plate; 2. Electrical device. Detailed Implementation

[0043] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of this application.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0045] The "range" disclosed in this application can be defined in the form of 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; any endpoint can be independently included or excluded, and they can be combined arbitrarily, meaning 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 ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also 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" and "5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when describing a parameter as an integer ≥ 2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12 for that parameter. For instance, when describing a parameter as an integer selected from "2-10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0046] In this application, the terms "multiple" or "various" are used unless otherwise specified, referring to a quantity greater than or equal to 2. For example, "one or more" means one or more types.

[0047] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0048] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. The term "implementation" as used herein has a similar understanding.

[0049] Those skilled in the art will understand that the order in which the steps are written in the methods of various embodiments or examples does not imply a strict execution order and does not constitute any limitation on the implementation process. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of this application may be performed sequentially or randomly. 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.

[0050] In this application, open-ended technical features or solutions described using terms such as "containing," "including," or "comprising" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, if A includes a1, a2, and a3, it may also include other members or exclude additional members unless otherwise specified. This can be considered as providing both the feature or solution that "A consists of a1, a2, and a3" and the feature or solution that "A includes not only a1, a2, and a3, but also other members."

[0051] In this application, unless otherwise specified, A (e.g., B) means that B is a non-limiting example of A, and it is understood that A is not limited to B.

[0052] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0053] In this application, unless otherwise specified, "cell battery" refers to the basic unit capable of converting chemical energy into electrical energy, and generally includes at least a positive electrode, a negative electrode, and an electrolyte. During the charging and discharging process of the battery, active ions move back and forth between the positive and negative electrode plates, inserting and extracting. The electrolyte acts as a conductor for the active ions between the positive and negative electrode plates.

[0054] During the storage process of lithium-ion batteries, there is a certain interaction between the positive and negative electrodes. For example, oxidation products generated at the positive electrode can be transferred to the negative electrode and react, consuming active lithium ions and reducing the storage performance of the lithium-ion battery.

[0055] One embodiment of this application provides a lithium-ion battery cell, including a positive electrode, a separator, and a negative electrode. The separator is located between the positive and negative electrode. The separator includes a substrate and a coating on the surface of the substrate. The coating contains an oxidizing agent. The oxidation-reduction potential of the oxidizing agent is located between the positive and negative electrode potentials of the lithium-ion battery cell at the upper limit of charging.

[0056] In the lithium-ion battery cell of this application, a coating containing an oxidizing agent is provided on the substrate surface of the separator. Since the oxidation-reduction potential of the oxidizing agent is located between the positive and negative electrode potentials of the lithium-ion battery at the upper limit of charging, the oxidation products generated at the positive electrode can be reduced at the separator by the oxidizing agent. This can reduce the amount of oxidation products transferred to the negative electrode and reduce the consumption of active lithium ions, thus improving the storage performance of the lithium-ion battery.

[0057] It is understood that the redox potential of the redox agent in this application represents the initial potential when the redox agent undergoes a redox reaction.

[0058] The redox potential of the redox agent in this application can be measured by the following test method:

[0059] (1) A slurry was prepared by mixing an oxidizing agent, a conductive agent (carbon nanotubes), a binder (polyvinylidene fluoride, PVDF), and a dispersant (polyvinylpyrrolidone, PVP) in a mass ratio of 94.5%:3%:2%:0.5%, and then adding N-methylpyrrolidone (NMP) and stirring. The slurry was uniformly coated onto an aluminum foil, dried, cold-pressed, and die-cut to prepare test electrodes. The test electrodes were coated on one side only.

[0060] (2) Assemble the test electrode and lithium sheet into a coin cell and perform charge-discharge tests. Charge the coin cell to 5V at a constant current of 0.05C and obtain the voltage change curve over time during the charging process. Take the potential where the voltage increases sharply over time in the curve as the upper limit voltage of the charge. Charge another identical coin cell to the upper limit voltage at a constant current of 0.05C and then let it stand for 5 minutes. Then discharge it to 0V at a constant current of 0.05C and obtain the voltage change curve over time during the discharge process. Take the potential where the voltage decreases sharply over time in the curve as the redox potential of the redox agent.

[0061] The positive and negative electrode potentials of the lithium-ion battery cell at the upper limit of charging in this application can be measured by the following method:

[0062] (1) Charge the lithium-ion battery cell to 5V at a constant current of 0.05C, obtain the voltage change curve with time during the charging process, and take the potential where the voltage increases sharply with time in the change curve as the upper limit voltage of the lithium-ion battery cell.

[0063] (2) Disassemble another identical lithium-ion battery cell to obtain the positive electrode and negative electrode. Assemble the positive electrode and lithium sheet into a coin cell and perform charge-discharge tests. Charge the cell at a constant current of 0.05C to the upper limit of the charging voltage in (1). Obtain the voltage change curve over time during the charging process. Take the potential where the voltage increases sharply over time in the change curve as the positive electrode potential of the lithium-ion battery cell at the upper limit of the charging voltage. Assemble the negative electrode and lithium sheet into a coin cell and perform charge-discharge tests. Charge the cell at a constant current of 0.05C to the upper limit of the charging voltage in (1). Obtain the voltage change curve over time during the charging process. Take the potential where the voltage increases sharply over time in the change curve as the negative electrode potential of the lithium-ion battery cell at the upper limit of the charging voltage.

[0064] In some embodiments, the redox potential of the redox agent is 1V-4.75V. This range of redox potential allows for better compatibility with lithium-ion battery cells across various voltage ranges, enabling more reduction of oxidation products generated at the positive electrode at the separator, reducing the amount of oxidation products transferred to the negative electrode, and further improving the storage performance of the battery cell. Optionally, the redox potential of the redox agent can be 1V, 1.2V, 1.5V, 1.8V, 2V, 2.2V, 2.5V, 2.8V, 3V, 3.2V, 3.5V, 3.8V, 4V, 4.2V, 4.5V, 4.7V, 4.75V, or any value within the range of any two of the above values. For example, the redox potential of an oxidizing agent can be 1V-2V, 1.5V-2V, 2V-3.8V, 2.5V-4.3V, 2.5V-4.7V, 3V-4.3V, 3V-4.4V, 3.1V-4.7V, 3.5V-4.4V, 3.8V-4.3V, 4.2V-4.7V, etc.

[0065] In some embodiments, the redox agents include Li5FeO4, Li2NiO2, Li6CoO4, Li2CuO2, Li2MoO2, Li5ReO6, Li2O, Li2O2, Li2S, LiCoO2, LiMn2O4, Li2MnO3, LiFePO4, LiMnFePO4, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and Li4Ti5O. 12 And one or more of TiNb2O7. Optionally, non-limiting examples of lithium nickel cobalt manganese oxides may include LiNi. 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 Examples of lithium nickel cobalt aluminum oxides include LiNi, etc. 0.8 Co0.15 Al 0.05 O2. Understandably, the redox agent may also include at least one of the modified products of lithium nickel cobalt manganese oxide and modified products of lithium nickel cobalt aluminum oxide.

[0066] In some embodiments, the redox agent constitutes 50%-98% of the coating by mass. Within this range, the redox agent can fully exert its effect, further promoting the improvement of the battery cell's storage performance. Optionally, the redox agent's mass percentage in the coating can be 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 98%, or any value within the range of any two of the above values.

[0067] It is understood that the coating also contains a binder. The binder helps maintain good adhesion between the coating and the substrate, which is beneficial for maintaining a stable structure of the release liner. Optionally, the binder accounts for 2%-50% of the coating's mass. Within this range, the binder content ensures that the redox agents in the coating maintain an appropriate mass, allowing the release liner to achieve both a stable structure and good redox performance. Optionally, the binder's mass percentage in the coating can be 2%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or any value within the range of any two of the above values.

[0068] Optionally, the binder in the coating includes polyvinylidene fluoride, polytetrafluoroethylene, styrene-acrylic latex, styrene-butadiene rubber, polymethyl methacrylate, polybutyl methacrylate, polyvinylpyrrolidone, polyethylene oxide, polyvinyl alcohol, sodium carboxymethyl cellulose, etc.

[0069] In some embodiments, a conductive agent may be added to the coating to enhance the electronic conductivity between coating particles and improve reaction kinetics. That is, the coating also contains a conductive agent. Optionally, the conductive agent may be one or more selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. Optionally, the conductive agent accounts for 0.01% to 5% of the coating by mass. For example, the conductive agent may account for 0.01%, 0.1%, 1%, 2%, 3%, 4%, 5%, or any value within the range of any two of the above values.

[0070] In some embodiments, the coating includes a first coating disposed on one surface of the substrate and located between the positive electrode and the substrate. The redox agent includes a first redox agent, and the first coating contains the first redox agent. The redox potential of the first redox agent is 2V-4.75V. The first coating, located between the positive electrode and the substrate and containing the first redox agent, allows oxidation products generated by the positive electrode to be reduced more quickly at the first coating, further reducing the amount of oxidation products transferred to the negative electrode, further reducing the consumption of active lithium ions, and thus improving the storage performance of the lithium-ion battery cell. Simultaneously, the positive electrode potential of the battery cell is often high. When the redox potential of the first redox agent is between 2V and 4.75V, the first redox agent can better adapt to the positive electrode, allowing for the reduction of oxidation products at a suitable rate while reducing abnormal problems caused by violent reactions within the battery cell. Optionally, the redox potential of the first redox agent can be 2V, 2.2V, 2.5V, 2.8V, 3V, 3.2V, 3.5V, 3.8V, 4V, 4.2V, 4.5V, 4.7V, or any value within the range of any two of the above values. For example, the redox potential of the first redox agent can be 2V-3.8V, 2.5V-4.3V, 2.5V-4.7V, 3V-4.3V, 3V-4.4V, 3.1V-4.7V, 3.5V-4.4V, 3.8V-4.3V, 4.2V-4.7V, etc. Further optionally, the first redox agent includes one or more of Li5FeO4, Li2NiO2, Li6CoO4, Li2CuO2, Li2MoO2, Li5ReO6, Li2O, Li2O2, Li2S, LiCoO2, LiMn2O4, Li2MnO3, LiFePO4, LiMnFePO4, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

[0071] In some embodiments, the first oxidizing agent accounts for 50%-98% of the mass percentage of the first coating. Within this range, the first oxidizing agent can fully exert its effect, further promoting the improvement of the battery cell's storage performance. Optionally, the first oxidizing agent can account for 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 98%, or any value within the range of any two of the above values.

[0072] It is understood that the first coating also includes an adhesive. Optionally, the adhesive accounts for 2%-50% of the mass percentage of the first coating. An adhesive content within this range allows the first coating to maintain good adhesion to the substrate, which is beneficial for maintaining a stable structure of the release liner. Optionally, the adhesive percentage of the first coating can be 2%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or any value within the range of any two of the above values.

[0073] Optionally, the binder in the first coating includes polyvinylidene fluoride, polytetrafluoroethylene, styrene-acrylic latex, styrene-butadiene rubber, polymethyl methacrylate, polybutyl methacrylate, polyvinylpyrrolidone, polyethylene oxide, polyvinyl alcohol, sodium carboxymethyl cellulose, etc.

[0074] In some embodiments, the thickness of the first coating is 0.1 μm-100 μm. A thickness within this range allows the separator to maintain a suitable thickness, thereby enabling the battery cell to maintain a high energy density. Optionally, the thickness of the first coating can be 0.1 μm, 0.5 μm, 0.8 μm, 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, or any value within the range of any two of the above values. For example, the thickness of the first coating can be 8 μm-20 μm, 18 μm-30 μm, 22 μm-40 μm, 55 μm-75 μm, 60 μm-90 μm, etc. Further optionally, the thickness of the first coating is 3μm-50μm. Even further optionally, the thickness of the first coating is 10μm-15μm.

[0075] In some embodiments, the lithium-ion battery cell further includes a first porous insulating film located between the positive electrode and the first coating. The presence of the first porous insulating film reduces the risk of direct contact between the positive electrode active material and the first oxidizing agent, decreases the occurrence of side reactions in the battery cell, and further improves the storage performance of the battery cell.

[0076] Optionally, the material of the first porous insulating film includes one or more of polyethylene, polypropylene, polyvinylidene fluoride, glass fiber, nonwoven fabric, and ceramics. More preferably, the thickness of the first porous insulating film is 5μm-15μm. For example, the thickness of the first porous insulating film can be 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, or any value within the range of any two of the above values.

[0077] In some embodiments, the coating includes a second coating disposed on one surface of the substrate and located between the negative electrode and the substrate. The redox agent includes a second redox agent, and the second coating contains the second redox agent. The redox potential of the second redox agent is 1V-2V. The second coating, located between the negative electrode and the substrate and containing the second redox agent, can oxidize the reduction products at the negative electrode, reducing the interaction between the positive and negative electrodes, which is beneficial for further improving the cycle performance of the battery cell. Optionally, the redox potential of the second redox agent can be 1V, 1.2V, 1.5V, 1.8V, 2V, or any value within the range of any two of the above values. For example, the redox potential of the redox agent can be 1V-2V, 1.5V-2V, etc. Further optionally, the second redox agent includes Li4Ti5O. 12 One or more of TiNb2O7.

[0078] In some embodiments, the second redox agent accounts for 50%-98% of the mass percentage of the second coating. This mass percentage range allows the second redox agent to fully exert its effect, further improving the storage performance of the battery cells. Optionally, the mass percentage of the second redox agent in the second coating can be 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 98%, or any value within the range of any two of the above values.

[0079] It is understood that the second coating also includes an adhesive. Optionally, the adhesive accounts for 2%-50% of the mass of the second coating. An adhesive content within this range allows the second coating to maintain good adhesion to the substrate, which is beneficial for maintaining a stable structure of the release liner. Optionally, the adhesive percentage of the second coating can be 2%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or any value within the range of any two of the above values.

[0080] Optionally, the binder in the second coating includes polyvinylidene fluoride, polytetrafluoroethylene, styrene-acrylic latex, styrene-butadiene rubber, polymethyl methacrylate, polybutyl methacrylate, polyvinylpyrrolidone, polyethylene oxide, polyvinyl alcohol, sodium carboxymethyl cellulose, etc.

[0081] In some embodiments, the thickness of the second coating is 0.1 μm-100 μm. A thickness within this range allows the separator to maintain a suitable thickness, thereby enabling the battery cell to maintain a high energy density. Optionally, the thickness of the second coating can be 0.1 μm, 0.5 μm, 0.8 μm, 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, or any value within the range of any two of the above values. For example, the thickness of the second coating can be 8 μm-20 μm, 18 μm-30 μm, 22 μm-40 μm, 55 μm-75 μm, 60 μm-90 μm, etc. Further optionally, the thickness of the second coating is 3μm-50μm. Even further optionally, the thickness of the second coating is 10μm-15μm.

[0082] In some embodiments, the lithium-ion battery further includes a second porous insulating film located between the negative electrode and the second coating. The presence of the second porous insulating film reduces the risk of direct contact between the negative electrode active material and the second redox agent, decreases side reactions within the battery cell, and further improves the storage performance of the battery cell.

[0083] Optionally, the material of the second porous insulating membrane includes one or more of polyethylene, polypropylene, polyvinylidene fluoride, glass fiber, nonwoven fabric, and ceramics. Further optionally, the thickness of the second porous insulating membrane is 5μm-15μm. For example, the thickness of the second porous insulating membrane can be 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, or any value within the range of any two of the above values.

[0084] Alternatively, the substrate material of the separator may include one or more of polyethylene, polypropylene, polyvinylidene fluoride, glass fiber, nonwoven fabric, and ceramics.

[0085] In some implementations, the positive electrode potential of a lithium-ion battery cell at its maximum charging limit is 4V-4.8V. At this level, the higher positive electrode potential is beneficial for increasing the energy density of the battery cell.

[0086] In some embodiments, the positive electrode includes a positive current collector and a positive active layer disposed on at least one surface of the positive current collector. The positive active layer includes a positive active material, which includes one or more of lithium phosphate, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide. Non-limiting examples of lithium phosphate may include, but are not limited to, lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites. Non-limiting examples of lithium cobalt oxide may include LiCoO2; non-limiting examples of lithium nickel oxide may include LiNiO2; non-limiting examples of lithium manganese oxide may include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxide may include LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.5 Co 0.25 Mn 0.25 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, etc. Non-limiting examples of lithium nickel cobalt aluminum oxides may include LiNi. 0.8 Co 0.15 Al 0.05 O2. It is understood that the positive electrode active material may also include at least one of the following: modified products containing lithium phosphate, modified products containing lithium cobalt oxide, modified products containing lithium nickel oxide, modified products containing lithium manganese oxide, modified products containing lithium nickel cobalt oxide, modified products containing lithium manganese cobalt oxide, modified products containing lithium nickel manganese oxide, modified products containing lithium nickel cobalt manganese oxide, and modified products containing lithium nickel cobalt aluminum oxide. Optionally, the positive electrode active material includes one or more of lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

[0087] In some embodiments, the negative electrode sheet includes a negative current collector and a negative active layer disposed on at least one surface of the negative current collector. The negative active layer includes a negative active material, which is a carbon-based material. The carbon-based material includes one or more of graphite, soft carbon, and hard carbon. Optionally, the graphite includes artificial graphite and natural graphite.

[0088] In some embodiments, the lithium-ion battery cell further includes an electrolyte comprising an electrolyte salt and a solvent, wherein the solvent comprises one or more of methyltrifluoroethyl carbonate and fluoroethylene carbonate. Methyltrifluoroethyl carbonate and fluoroethylene carbonate have good oxidation resistance, which can help maintain good stability of the electrolyte when the battery cell voltage is high, thereby further improving the performance of the battery cell.

[0089] In some embodiments, the solvent comprises methyltrifluoroethyl carbonate and fluoroethylene carbonate in a volume ratio of (6-8):(2-4). This volume ratio of methyltrifluoroethyl carbonate to fluoroethylene carbonate within this range allows the electrolyte to exhibit better high-voltage stability, which is beneficial for further improving the performance of individual battery cells.

[0090] In some embodiments, the mass percentage of the additive in the electrolyte is less than or equal to 0.1%, optionally, the mass percentage of the additive in the electrolyte is less than or equal to 0.01%, and further optionally, the mass percentage of the additive in the electrolyte is 0.

[0091] Another embodiment of this application provides a lithium-ion battery. The lithium-ion battery includes the aforementioned lithium-ion battery cell.

[0092] Another embodiment of this application provides an electrical device. The electrical device includes the aforementioned lithium-ion battery.

[0093] The following description, with appropriate reference to the accompanying drawings, describes the battery cell, battery, and power device of this application.

[0094] 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.

[0095] Positive electrode sheet

[0096] The positive electrode sheet includes a positive current collector and a positive active layer disposed on at least one surface of the positive current collector, the positive active layer comprising a positive active material.

[0097] As a non-limiting example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0098] In some embodiments, the positive electrode 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 material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be obtained by forming a metal material on a polymer material substrate. Non-limiting examples of the metal material in the positive electrode current collector may include one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Non-limiting examples of the polymer material substrate in the positive electrode current collector may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0099] In some embodiments, in addition to the active materials involved in this application, the positive electrode active material may also be a positive electrode active material known in the art for use in batteries.

[0100] In some embodiments, the positive electrode active layer may optionally include a binder. As a non-limiting example, the binder may include one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0101] In some embodiments, the positive electrode active layer may optionally include a conductive agent. As a non-limiting example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0102] In some embodiments, the positive electrode sheet can be prepared by dispersing components for preparing the positive electrode sheet, such as positive active materials, conductive agents, binders, and any other components, in a solvent to form a positive electrode slurry; coating the positive electrode slurry onto at least one surface of a positive current collector, and then obtaining the positive electrode sheet through processes such as drying and cold pressing. The solvent can be selected from N-methylpyrrolidone (NMP). The surface of the positive current collector coated with the positive electrode slurry can be a single surface or both surfaces of the positive current collector. The solid content of the positive electrode slurry can be 40% by weight (wt%) to 80% by weight. The viscosity of the positive electrode slurry at room temperature can be adjusted to 5000 mPa·s to 25000 mPa·s. When coating the positive electrode slurry, the areal density per unit area (dry weight, minus solvent) can be 15 mg / cm². 2 -35mg / cm 2 The compacted density of the positive electrode sheet can be 3.0 g / cm³. 3-3.6g / cm 3 3.3g / cm³ is an option. 3 -3.5g / cm 3 .

[0103] Negative electrode sheet

[0104] The negative electrode sheet includes a negative current collector and a negative active layer disposed on at least one surface of the negative current collector, the negative active layer including a negative active material.

[0105] As a non-limiting example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0106] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymeric material substrate and a metal layer formed on at least one surface of the polymeric material substrate. The composite current collector can be obtained by forming a metal material on the polymeric material substrate. Non-limiting examples of the metal material in the negative electrode current collector may include one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Non-limiting examples of the polymeric material substrate in the negative electrode current collector may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0107] In some embodiments, in addition to the carbon-based materials described above, the negative electrode active material may also be a known battery negative electrode active material. As a non-limiting example, the negative electrode active material may include one or more of the following materials: silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may include one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include 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 battery negative electrode active materials may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0108] In some embodiments, the negative electrode active layer may optionally include a binder. The binder may include one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0109] In some embodiments, the negative electrode active layer may optionally include a conductive agent. The conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0110] In some embodiments, the negative electrode active layer may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0111] 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 active material, conductive agent, binder, and any other components, in a solvent (a non-limiting example of a solvent is deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto at least one surface of a negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing, or other processes. The surface of the negative electrode current collector coated with the negative electrode slurry can be a single surface of the negative electrode current collector or both surfaces of the negative electrode current collector. The solid content of the negative electrode slurry can be 40wt%~60wt%. The viscosity of the negative electrode slurry at room temperature can be adjusted to 2000mPa·s-10000mPa·s. When coating the negative electrode slurry, the coating unit areal density (dry weight, minus solvent) can be 75 g / m². 2 -220g / m 2 The compaction density of the negative electrode sheet can be 1.0 g / cm³. 3 -1.8g / cm 3 .

[0112] electrolytes

[0113] Electrolytes function to conduct ions between the positive and negative electrode plates. This application does not impose any particular restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or completely solid.

[0114] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0115] In some embodiments, the electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0116] In some embodiments, the solvent may include ethylene carbonate (EC, ), propylene carbonate (PC, ), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butene carbonate ( One or more of the following: fluoroethylene carbonate (FEC), 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.

[0117] 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.

[0118] Separating membrane

[0119] In some embodiments, the separator can be the separator described above. The separator can be a single-layer film or a multi-layer composite film; there are no particular limitations. When the separator is a multi-layer composite film, the materials of each layer can be the same or different; there are no particular limitations.

[0120] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0121] 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.

[0122] 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; further, non-limiting examples of plastic may include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0123] A lithium-ion battery includes at least one battery cell. A lithium-ion battery may include one or more battery cells.

[0124] 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 1 Here is a square-structured battery cell 1 as an example.

[0125] In some implementations, refer to Figure 2The outer packaging may include a housing 11 and a cover plate 13. The housing 11 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 11 has an opening communicating with the receiving cavity, and the cover plate 13 can be placed over the opening to close the receiving cavity. The positive electrode sheet, negative electrode sheet, and separator can be formed into an electrode assembly 12 by a winding process or a stacking process. The electrode assembly 12 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 12. The number of electrode assemblies 12 contained in a single battery cell 1 can be one or more, which can be selected by those skilled in the art according to actual needs.

[0126] Lithium-ion batteries can be battery modules or battery packs.

[0127] A battery module includes at least one battery cell. The number of battery cells in a battery module can be one or more, and those skilled in the art can select an appropriate number based on the application and capacity of the battery module.

[0128] In a battery module, multiple battery cells can be arranged sequentially along the length of the module. Of course, they can also be arranged in any other manner. Furthermore, these battery cells can be secured using fasteners.

[0129] Optionally, the battery module may also include a housing with a receiving space in which multiple battery cells are housed.

[0130] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the battery pack may contain one or more battery modules. Those skilled in the art can select an appropriate number based on the application and capacity of the battery pack.

[0131] The battery pack may include a battery box and multiple battery modules disposed within the battery box. The battery box includes an upper body and a lower body, with the upper body covering the lower body to form a closed space for accommodating the battery modules. The multiple battery modules can be arranged in any manner within the battery box.

[0132] In addition, this application also provides an electrical device, which includes the lithium-ion battery provided in this application. The lithium-ion 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, electric vehicles, electric trains, ships and satellites, energy storage systems, etc. Among them, mobile devices may be, for example, mobile phones, laptops, etc.; electric vehicles may be, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc., but are not limited to.

[0133] As an electrical device, lithium-ion batteries can be selected based on its usage requirements.

[0134] Figure 3 Here is an example of an electrical device 2. This electrical 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 secondary battery for this electrical device, a battery pack or battery module can be used.

[0135] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0136] To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the application will be further described in detail below with reference to embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its applications. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0137] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0138] Example 1

[0139] (1) Preparation of positive electrode sheet

[0140] Lithium nickel manganese oxide (LiNi) 0.5 Mn 1.5 O4), conductive carbon nanotubes, binder polyvinylidene fluoride (PVDF), and dispersant polyvinylpyrrolidone (PVP) are mixed in a mass ratio of 94.5%:3%:2%:0.5%, and N-methylpyrrolidone (NMP) is added and stirred to prepare a positive electrode slurry. The positive electrode slurry is uniformly coated on aluminum foil, dried, cold-pressed, and die-cut to prepare positive electrode sheets. The positive electrode sheets are coated on one side only.

[0141] (2) Preparation of negative electrode sheet

[0142] Graphite, conductive agent carbon black, and binder polytetrafluoroethylene (PTFE) were mixed in a mass ratio of 96%:2%:2%, and deionized water was added and stirred to prepare a negative electrode slurry. The negative electrode slurry was uniformly coated on copper foil, dried, cold-pressed, and die-cut to prepare negative electrode sheets. The negative electrode sheets were double-sided coated.

[0143] (4) Preparation of the isolation membrane

[0144] The redox agent LiNi 0.8 Co 0.1 Mn 0.1 O2, polyvinylidene fluoride (PVDF) binder, and conductive carbon black were mixed in a mass ratio of 90%:5%:5%, and N-methylpyrrolidone (NMP) was added and stirred to prepare a coating slurry with a solid content of 40%. The coating slurry was applied to one side of a 7μm thick polypropylene substrate and dried to obtain a release film. The coating thickness was 10μm.

[0145] (5) Preparation of electrolyte

[0146] Lithium hexafluorophosphate (LiPF6) was uniformly dissolved in an organic solvent in an argon-atmosphere glove box with a water content of <10 ppm to obtain an electrolyte. The molar concentration of LiPF6 in the electrolyte was 1 mol / L. The organic solvent was methyl trifluoroethyl carbonate (FEMC) and fluoroethylene carbonate (FEC) in a volume ratio of 7:3.

[0147] (6) Preparation of battery cells

[0148] The positive electrode, the first porous insulating film (polypropylene film, 7μm thick), the separator, the negative electrode, the separator, the second porous insulating film (polypropylene film, 7μm thick), and the positive electrode are stacked in sequence to form a battery cell, with the separator coating facing the positive electrode. The battery cell is placed in an outer packaging, then left to stand, undergo formation testing, and age to obtain a single battery cell. The voltage range of the single battery cell is 3.5V-4.9V.

[0149] Example 2

[0150] The difference between Example 2 and Example 1 is that the redox agent is replaced with LiFePO4.

[0151] Comparative Example 1

[0152] The difference between Comparative Example 1 and the Examples is that the separator does not have a coating.

[0153] Test case

[0154] (1) The storage capacity of the battery cells in the examples and comparative examples was tested: the battery cells were stored at 45°C. Every 3 days, they were taken off the shelf for room temperature capacity testing and returned to the oven at 45°C for storage until the capacity retention rate was 80%.

[0155] Specifically, the storage capacity testing method is as follows:

[0156] ① At 25℃, charge the battery cell at a constant current of 0.33C to 4.9V, then charge it at a constant voltage of 4.9V to 0.05C; then discharge it at a constant current of 0.33C to 3.5V, then discharge it at a constant voltage of 3.5V to 0.05C, and test the initial capacity C0 of the battery cell.

[0157] ② At 25℃, charge at a constant current of 0.33C to 4.9V, and then charge at a constant voltage of 4.9V to 0.05C; then store in a constant temperature chamber at 45℃ for 3 days.

[0158] ③ At 25℃, discharge at a constant current of 0.33C to 3.5V, then discharge at a constant voltage of 3.5V to 0.05C; then charge at a constant current of 0.33C to 4.9V, then charge at a constant voltage of 4.9V to 0.05C; then discharge at a constant current of 0.33C to 3.5V, then discharge at a constant voltage of 3.5V to 0.05C, and test the capacity Cn of the battery cell.

[0159] ④ Repeat steps ②-③ until the capacity retention rate of the battery cell is 80%, that is, until Cn / C0×100%=80%.

[0160] The capacity retention rate of the battery cells in Examples 1-2 and Comparative Example 1 as a function of storage time is shown in the curves. Figure 4 As shown. By Figure 4 It can be seen that the storage capacity retention rate of the battery cells in Examples 1-2 is higher than that in Comparative Example 1, indicating that the introduction of a redox agent into the separator can improve the storage performance of the battery cells. Furthermore, the storage capacity retention rate of the battery cells in Example 1 is higher than that in Example 2, indicating that the redox agent is LiNi. 0.8 Co 0.1 Mn 0.1 O2 can further improve the storage performance of individual battery cells.

[0161] (2) The gas production of the battery cells in the examples and comparative examples was tested: The water displacement method was used. The battery cell tabs were sealed with insulating tape at 45°C. One end of the battery cell was wrapped with insulating tape, and the other end was fixed and suspended on the equipment. Maintaining the same tension, the battery cell was immersed in a beaker containing pure water, ensuring the tabs were level with the water surface. The weight was recorded after the balance stabilized (the beaker was placed on the balance). The gas production of the battery cell after 40 days of storage was recorded. The gas production results are as follows: Figure 5 As shown. By Figure 5 It can be seen that the gas production of the battery cells in Examples 1-2 is lower than that in Comparative Example 1, indicating that introducing a redox agent into the separator can improve the storage performance of the battery cells. Furthermore, the gas production of the battery cells in Example 1 is lower than that in Example 2, indicating that the redox agent is LiNi. 0.8 Co 0.1 Mn 0.1 O2 can further improve the storage performance of individual battery cells.

[0162] (3) The gases generated by storing the battery cells in the examples and comparative examples at 45°C for 40 days were analyzed using gas chromatography-TCD. The composition results are as follows: Figure 6 As shown. By Figure 6 As can be seen, compared with Comparative Example 1, the reduction gas hydrogen generated by the battery cells in Examples 1-2 during storage is reduced, indicating that the oxidation products reduced at the negative electrode are reduced. This suggests that when the separator coating contains a redox agent, it can reduce the amount of oxidation products transferred to the negative electrode, thus improving the storage performance of the battery cells. Furthermore, almost no hydrogen is generated during the storage of the battery cells in Example 1, indicating that the redox agent is LiNi. 0.8 Co 0.1 Mn 0.1 O2 can further improve the storage performance of individual battery cells.

[0163] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0164] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A lithium-ion battery cell, characterized in that, The lithium ion battery cell includes a positive electrode sheet, a separator, and a negative electrode sheet, the separator is located between the positive electrode sheet and the negative electrode sheet, the separator includes a substrate and a coating layer located on the surface of the substrate, the coating layer contains a redox agent, and the redox potential of the redox agent is between the positive electrode potential and the negative electrode potential of the lithium ion battery cell at the upper limit of charging.

2. The lithium-ion battery cell of claim 1, wherein, The redox potential of the redox agent is 1V-4.75V.

3. The lithium-ion battery cell according to claim 1 or 2, characterized in that, Li5Fe04, Li2Ni02, Li6Co04, Li2Cu02, Li2Mo02, Li5Re06, Li20, Li202, Li2S, LiCo02, LiMn204, Li2Mn03, LiFeP04, LiMnFeP04, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, Li4Ti50 12 and one or more of TiNb207.

4. The lithium-ion battery cell of any one of claims 1-3, wherein, The mass percentage of the redox agent in the coating layer is 50%-98%.

5. The lithium-ion battery cell of any one of claims 1-4, wherein, The coating layer further contains a binder.

6. The lithium-ion battery cell of claim 5, wherein, The binder satisfies one or more of the following characteristics: (1) The mass percentage of the binder in the coating layer is 2%-50%; (2) The binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, styrene-acrylic latex, styrene-butadiene rubber, polymethyl methacrylate, polybutyl methacrylate, polyvinylpyrrolidone, polyethylene oxide, polyvinyl alcohol, and sodium carboxymethyl cellulose.

7. The lithium-ion battery cell of any one of claims 1-6, wherein, The coating layer further contains a conductive agent.

8. The lithium-ion battery cell of claim 7, wherein, The conductive agent satisfies one or more of the following characteristics: (1) The mass percentage of the conductive agent in the coating layer is 0.01%-5%; (2) The conductive agent includes one or more of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

9. The lithium-ion battery cell of any one of claims 1-8, wherein, The coating layer includes a first coating layer, the first coating layer is located on one surface of the substrate and between the positive electrode sheet and the substrate, the redox agent includes a first redox agent, the first coating layer contains the first redox agent, and the redox potential of the first redox agent is 2V-4.75V.

10. The lithium-ion battery cell of claim 9, wherein, The first redox agent includes one or more of Li5FeO4, Li2NiO2, Li6CoO4, Li2CuO2, Li2MoO2, Li5ReO6, Li2O, Li2O2, Li2S, LiCoO2, LiMn2O4, Li2MnO3, LiFePO4, LiMnFePO4, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

11. The lithium-ion battery cell according to claim 9 or 10, characterized in that The mass percentage of the first redox agent in the first coating layer is 50%-98%.

12. The lithium-ion battery cell of any one of claims 9-11, wherein, The thickness of the first coating layer is 0.1μm-100μm.

13. The lithium-ion battery cell of any one of claims 9-12, wherein, The thickness of the first coating layer is 3μm-50μm.

14. The lithium-ion battery cell of any one of claims 9-13, wherein, The thickness of the first coating layer is 10μm-15μm.

15. The lithium-ion battery cell of any one of claims 9-14, wherein, The lithium ion battery cell further includes a first porous insulating film, and the first porous insulating film is located between the positive electrode sheet and the first coating layer.

16. The lithium-ion battery cell of claim 15, wherein, The first porous insulating film satisfies one or more of the following characteristics: (1) The material of the first porous insulating film includes one or more of polyethylene, polypropylene, polyvinylidene fluoride, glass fiber, non-woven fabric, and ceramic; (2) The thickness of the first porous insulating film is 5μm-15μm.

17. The lithium-ion battery cell of any one of claims 1-16, wherein, The coating includes a second coating disposed on a surface of the substrate between the negative electrode tab and the substrate, the redox agent includes a second redox agent, the second coating includes the second redox agent, and the second redox agent has a redox potential of 1 V to 2 V.

18. The lithium-ion battery cell of claim 17, wherein, The second redox agent includes one or more of Li4Ti5O 12 and TiNb2O7.

19. The lithium-ion battery cell of claim 17 or 18, wherein, The second redox agent accounts for 50% to 98% of the mass percentage of the second coating.

20. The lithium-ion battery cell of any one of claims 17-19, wherein, The second coating has a thickness of 0.1 μm to 100 μm.

21. The lithium-ion battery cell of any one of claims 17-20, wherein, The second coating has a thickness of 3 μm to 50 μm.

22. The lithium-ion battery cell of any one of claims 17-21, wherein, The second coating has a thickness of 10 μm to 15 μm.

23. The lithium-ion battery cell of any one of claims 17-22, wherein, The lithium ion battery cell further includes a second porous insulating film between the negative electrode tab and the second coating.

24. The lithium-ion battery cell of claim 23, wherein, The second porous insulating film satisfies one or more of the following characteristics: (1) the material of the second porous insulating film includes one or more of polyethylene, polypropylene, polyvinylidene fluoride, glass fiber, non-woven fabric, and ceramic; (2) the thickness of the second porous insulating film is 5 μm to 15 μm.

25. The lithium-ion battery cell of any one of claims 1-24, wherein, The lithium ion battery cell has a positive electrode potential of 4 V to 4.8 V at a charge upper limit.

26. The lithium-ion battery cell of claim 25, wherein, The positive electrode tab includes a positive electrode current collector and a positive electrode active layer disposed on at least one surface of the positive electrode current collector, the positive electrode active layer includes a positive electrode active material, and the positive electrode active material includes one or more of lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

27. The lithium-ion battery cell of any one of claims 1-26, wherein, The lithium ion battery cell further includes an electrolyte, the electrolyte includes an electrolyte salt and a solvent, and the solvent includes one or more of methyl trifluoroethyl carbonate and fluoroethylene carbonate.

28. The lithium-ion battery cell of claim 27, wherein, The solvent includes the methyl trifluoroethyl carbonate and the fluoroethylene carbonate, and the volume ratio of the methyl trifluoroethyl carbonate to the fluoroethylene carbonate is (6-8):(2-4).

29. A lithium-ion battery, characterized by, The lithium ion battery cell includes any one of claims 1-28.

30. An electrical device, comprising: The lithium ion battery includes claim 29.

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