Lithium ion battery and preparation method thereof, positive electrode slurry, positive electrode plate and electric device

Abstract

The invention provides a lithium ion battery and a preparation method thereof, positive electrode slurry, a positive electrode plate and a power utilization device, the lithium ion battery comprises the positive electrode plate, the positive electrode plate comprises a positive electrode active material layer, and the positive electrode active material layer comprises a lithium-rich manganese-based positive electrode material and a thiourea additive. The thiourea additive is added into the positive electrode active material layer, and the thiourea additive can synergistically participate in the intercalation / deintercalation process of lithium ions, and plays a role in promoting deintercalation of the lithium ions in the charging and discharging process; meanwhile, the thiourea additive acts with the lithium-rich manganese-based positive electrode material, so that the dissolution of transition metal in the lithium-rich manganese-based positive electrode material can be reduced, and the structural stability of the material is improved. The lithium ion battery has relatively good cycle performance and storage performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a lithium ion battery, a preparation method of the lithium ion battery, a positive electrode slurry, a positive electrode sheet and an electric device. BACKGROUND

[0002] In recent years, with the application range of lithium ion batteries becoming more and more extensive, lithium ion batteries are widely used in energy storage power supply systems such as hydraulic, thermal, wind and solar power stations, and in many fields such as electric tools, electric bicycles, electric motorcycles and electric vehicles.

[0003] The lithium-rich manganese-based positive electrode material has the advantages of high energy density and abundant raw material sources. Therefore, the lithium-rich manganese-based positive electrode material has obtained wide attention as the positive active material of a lithium ion battery. However, the lithium-rich manganese-based positive electrode material also has the disadvantage of poor cycle performance and storage performance, which limits its application in lithium ion batteries.

[0004] Therefore, how to improve the cycle performance and storage performance of a lithium ion battery using a lithium-rich manganese-based positive electrode material is one of the directions that the person skilled in the art focuses on. SUMMARY

[0005] The present application is carried out in view of the above-mentioned problems, and one of the purposes is to provide a lithium ion battery using a lithium-rich manganese-based positive electrode material with good cycle performance and storage performance, and correspondingly to provide a preparation method of the lithium ion battery, a positive electrode slurry, a positive electrode sheet and an electric device using the lithium ion battery.

[0006] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a lithium ion battery, comprising a positive electrode sheet, the positive electrode sheet comprising a positive active material layer, the positive active material layer comprising a lithium-rich manganese-based positive electrode material and a thiourea-based additive.

[0007] By adding a thiourea-based additive in the positive active material layer, the thiourea-based additive can participate in the embedding / detaching process of lithium ions, and plays a role in promoting the embedding and detaching of lithium ions in the charging and discharging process; at the same time, the thiourea-based additive acts with the lithium-rich manganese-based positive electrode material, which can reduce the dissolution of transition metals in the lithium-rich manganese-based positive electrode material and improve the material structure stability. The lithium ion battery has good cycle performance and storage performance.

[0008] In any embodiment, the mass of the thiourea-based additive in the positive active material layer is 0.3% to 1% of the mass of the lithium-rich manganese-based positive electrode material. In this way, the lithium ion battery can obtain better cycle performance and storage performance.

[0009] In any embodiment, the mass of the thiourea additive in the positive electrode active material layer is 0.3% to 0.7% of the mass of the lithium-rich manganese-based positive electrode material. This further improves the cycle performance and storage performance of the lithium-ion battery.

[0010] In any embodiment, the thiourea additive includes one or more of thiourea, ethylene thiourea, propylene thiourea, and ammonia thiourea. The aforementioned thiourea additives can effectively reduce the leaching of transition metals in lithium-rich manganese-based cathode materials and improve the structural stability of lithium-rich manganese-based cathode materials, thereby effectively improving the cycle performance and storage performance of lithium-ion batteries.

[0011] In any embodiment, the BET specific surface area of ​​the lithium-rich manganese-based cathode material is 1.0 m². 2 / g~2.0m 2 / g. In this way, not only can thiourea additives fully combine with the surface of lithium-rich manganese-based cathode materials, but side reactions between lithium-rich manganese-based cathode materials and electrolytes can also be reduced, thereby further improving the cycle performance and storage performance of lithium-ion batteries.

[0012] In any embodiment, the manganese leaching amount of the lithium-rich manganese-based cathode material is less than 80 ppm. The lithium-ion battery of this application exhibits good structural stability and low manganese leaching amount in its lithium-ion cathode material.

[0013] In any embodiment, the chemical formula of the lithium-rich manganese-based cathode material is Li[Li] x Ni a Co b Mn c M d O2, where x+a+b+c+d=1, x>0, a>0, 0≤b≤0.1, c≥0.5, d>0, a+b+c+d<1; M is one or more of Mg, Nb, Cr, Ce, Fe, Ta, Al, V, Ti, Zr, Sn and Mo.

[0014] The second aspect of this application provides a method for preparing a lithium-ion battery, comprising the following steps:

[0015] A lithium-rich manganese-based cathode material is mixed with thiourea additives to obtain a cathode slurry;

[0016] The positive electrode slurry is placed on the positive electrode current collector to form a positive electrode slurry layer, and then dried to obtain a positive electrode sheet.

[0017] The lithium-ion battery preparation method described in this application can improve the cycle performance and storage performance of lithium-ion batteries. Furthermore, this preparation method does not require high-temperature treatment or post-treatment, and the process is simple and has a short preparation cycle.

[0018] In any embodiment, the mass of the thiourea additive in the cathode slurry is 0.3% to 1% of the mass of the lithium-rich manganese-based cathode material. This enables the lithium-ion battery to achieve better cycle performance and storage performance.

[0019] In any embodiment, the mass of the thiourea additive in the cathode slurry is 0.3% to 0.7% of the mass of the lithium-rich manganese-based cathode material. This further improves the cycle performance and storage performance of the lithium-ion battery.

[0020] In any embodiment, the thiourea additive includes one or more of thiourea, ethylene thiourea, propylene thiourea, and ammonia thiourea. The aforementioned thiourea additives can effectively reduce the leaching of transition metal manganese in lithium-rich manganese-based cathode materials and improve the structural stability of lithium-rich manganese-based cathode materials, thereby effectively improving the cycle performance and storage performance of lithium-ion batteries.

[0021] A third aspect of this application provides a positive electrode slurry comprising a lithium-rich manganese-based positive electrode material and a thiourea additive. By adding a thiourea additive to the positive electrode slurry, lithium-ion batteries using positive electrode sheets formed from this slurry can exhibit better cycle performance and storage performance.

[0022] A fourth aspect of this application provides a positive electrode sheet, comprising a positive electrode active material layer, wherein the positive electrode active material layer comprises a lithium-rich manganese-based positive electrode material and a thiourea additive. By adding a thiourea additive to the positive electrode active material layer of the positive electrode sheet, lithium-ion batteries using this positive electrode sheet can exhibit better cycle performance and storage performance.

[0023] The fifth aspect of this application provides an electrical device, including one or more of the lithium-ion batteries of the first aspect of this application and the lithium-ion batteries prepared by the preparation method of the lithium-ion batteries of the second aspect of this application.

[0024] Details of one or more embodiments of this application are set forth in the following drawings and description. Other features, objects, and advantages of this application will become apparent from the specification, drawings, and claims. Attached Figure Description

[0025] 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:

[0026] Figure 1This is a schematic diagram of a battery cell according to one embodiment of this application;

[0027] Figure 2 for Figure 1 An exploded view of a battery cell according to one embodiment of this application is shown.

[0028] Figure 3 This is a schematic diagram of an electrical device that uses a lithium-ion battery as a power source according to one embodiment of this application.

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

[0030] 5. Battery cell; 51. Casing; 52. Electrode assembly; 53. Cover plate; 6. Electrical device. Detailed Implementation

[0031] The following describes in detail, with appropriate reference to the accompanying drawings, embodiments of the lithium-ion battery and its preparation method, as well as embodiments of the power-using device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for 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 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; 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 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 "a~b" 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 a parameter is described as an integer ≥2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2~10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0033] 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.

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

[0035] 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.

[0036] 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, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) can 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.

[0037] 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." In this application, unless otherwise specified, A (e.g., B) indicates that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0038] 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.

[0039] Lithium-rich manganese-based cathode materials have broad application prospects as positive electrode active materials for lithium-ion batteries due to their advantages of high energy density, abundant raw material sources, and low price. However, lithium-ion batteries using lithium-rich manganese-based cathode materials exhibit poor cycle performance and storage performance, severely limiting their application in lithium-ion batteries. To address this, this application improves the positive electrode active material layer of the cathode sheet, effectively enhancing the cycle performance and storage performance of lithium-ion batteries using lithium-rich manganese-based cathode materials.

[0040] In one embodiment of this application, a lithium-ion battery is provided, which includes a positive electrode sheet, the positive electrode sheet including a positive active material layer, the positive active material layer including a lithium-rich manganese-based positive electrode material and a thiourea additive.

[0041] Lithium-rich manganese-based cathode materials continuously release oxygen during battery cycling and storage, leading to structural instability and a tendency for phase transitions in the cathode active material. This results in poor cycle and storage performance of lithium-ion batteries and a decrease in battery safety. Traditional solutions to these problems typically involve modifying the lithium-rich manganese-based cathode material, primarily through bulk doping, surface coating, and morphology control. These modification methods often require high-temperature treatment, which can affect the structure of the cathode material, and the preparation cycle is lengthy.

[0042] The lithium-ion battery described in this application uses a lithium-rich manganese-based cathode material as the cathode active material layer, and adds a thiourea additive to the cathode active material layer. The thiourea additive has strong N / S bond stability and can synergistically participate in the lithium-ion insertion / extraction process, promoting lithium-ion insertion and extraction during charge and discharge. Simultaneously, due to the introduction of the thiourea additive, a certain degree of SO exchange occurs on the surface of the lithium-rich manganese-based cathode material. The binding energy of sulfur with transition metals is greater than that of oxygen with transition metals, which can reduce the dissolution of transition metals in the lithium-rich manganese-based cathode material and improve the structural stability of the material, thereby improving the cycle performance and storage performance of the lithium-ion battery. Moreover, the method of adding thiourea additives to the cathode active material layer is simpler and has a shorter preparation cycle compared to traditional modification treatments.

[0043] In some embodiments, the mass of thiourea additives in the positive electrode active material layer is 0.3% to 1% of the mass of the lithium-rich manganese-based positive electrode material. By examining the effect of different contents of thiourea additives on the performance of lithium-ion batteries, it was found that adding 0.3% to 1% of thiourea additives in the positive electrode active material layer, based on the mass of the lithium-rich manganese-based positive electrode material, can enable lithium-ion batteries to achieve better cycle performance and storage performance.

[0044] It is understandable that the content of thiourea additives in the positive electrode active material layer can be 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, 1% of the mass of the lithium-rich manganese-based positive electrode material, or any value within the range formed by any two of the above values.

[0045] In some embodiments, the mass of thiourea additives in the positive electrode active material layer is 0.3% to 0.7% of the mass of the lithium-rich manganese-based positive electrode material. Thus, by controlling the amount of thiourea additives in the positive electrode active material layer within the aforementioned range, the cycle performance and storage performance of the lithium-ion battery can be further improved.

[0046] In some embodiments, the thiourea additive includes one or more of thiourea, ethylene thiourea, propylene thiourea, and ammonia thiourea. Adding these types of thiourea additives to the positive electrode active material layer can effectively reduce the dissolution of transition metals in lithium-rich manganese-based positive electrode materials and improve the structural stability of lithium-rich manganese-based positive electrode materials, thereby effectively improving the cycle performance and storage performance of lithium-ion batteries. In some specific examples, the thiourea additive is thiourea.

[0047] In some embodiments, the evaporation temperature of the thiourea additive is higher than 150°C. During the preparation of the positive electrode sheet, positive active material, thiourea additive, conductive agent, binder, and solvent are mixed to form a positive electrode slurry. This slurry is then coated onto a positive current collector to form a positive electrode slurry layer. The slurry layer is then dried to form a positive active material layer, thus obtaining the positive electrode sheet. In the above process, the drying temperature of the positive electrode slurry layer is typically no higher than 150°C, generally around 100°C. By using a thiourea additive with an evaporation temperature higher than 150°C, the thiourea additive can be prevented from evaporating during the drying process of the positive electrode slurry layer, thus allowing it to remain in the positive active material layer.

[0048] It should be noted that the evaporation temperature of thiourea additives refers to the temperature at which thiourea additives change from a solid or liquid state to a gaseous state under normal pressure.

[0049] In some embodiments, the BET specific surface area of ​​the lithium-rich manganese-based cathode material is 1.0 m².2 / g~2.0m 2 / g. A small BET specific surface area in lithium-rich manganese-based cathode materials results in low surface activity, which is detrimental to the surface bonding of thiourea additives with the lithium-rich manganese-based cathode material. Conversely, a large BET specific surface area leads to high surface activity, which easily increases side reactions with the electrolyte. By controlling the BET specific surface area of ​​the lithium-rich manganese-based cathode material within the aforementioned range, not only can thiourea additives fully bond with the surface of the lithium-rich manganese-based cathode material, but side reactions between the lithium-rich manganese-based cathode material and the electrolyte can also be reduced, thereby further improving the cycle performance and storage performance of lithium-ion batteries.

[0050] Understandably, the BET specific surface area of ​​lithium-rich manganese-based cathode materials can be 1.0 m². 2 / g, 1.1m 2 / g, 1.2m 2 / g, 1.3m 2 / g, 1.4m 2 / g, 1.5m 2 / g, 1.6m 2 / g, 1.7m 2 / g, 1.8m 2 / g, 1.9m 2 / g, 2.0m 2 / g and any value within the range formed by any two of the above values.

[0051] In some embodiments, the manganese leaching amount of the lithium-rich manganese-based cathode material is less than 80 ppm. During battery cycling, manganese ions often dissolve from lithium-rich manganese-based cathode materials due to structural degradation. The amount of manganese leaching reflects the structural stability of the lithium-rich manganese-based cathode material. The lower the manganese leaching amount, the more stable the structure of the lithium-rich manganese-based cathode material. This application effectively reduces the dissolution of transition metal manganese ions in lithium-rich manganese-based cathode materials by adding thiourea additives to the cathode active material layer, achieving a manganese leaching amount of less than 80 ppm and effectively improving the structural stability of the cathode material. Here, manganese leaching amount refers to the content of manganese dissolved from the cathode material under specific conditions. The manganese leaching amount of the lithium-rich manganese-based cathode material is measured by ICP (Inductively Coupled Plasma).

[0052] In some embodiments, the chemical formula of the lithium-rich manganese-based cathode material is Li[Li] x Ni a Co b Mn c M dO2, where x+a+b+c+d=1, x>0, a>0, 0≤b≤0.1, c≥0.5, d>0, a+b+c+d<1; M is one or more of Mg, Nb, Cr, Ce, Fe, Ta, Al, V, Ti, Zr, Sn and Mo.

[0053] In one embodiment of this application, a method for preparing the lithium-ion battery described above is provided, the method comprising the following steps S100 to S400:

[0054] Step S100: Mix the lithium-rich manganese-based cathode material and thiourea additives evenly to obtain a cathode slurry;

[0055] Step S200: Place the positive electrode slurry on the positive electrode current collector to form a positive electrode slurry layer, and dry it to obtain a positive electrode sheet;

[0056] Step S300: Assemble the bare cell by stacking the positive electrode sheet, the separator, and the negative electrode sheet;

[0057] Step S400: Place the bare battery cell in the outer packaging, inject electrolyte, and encapsulate to obtain a lithium-ion battery.

[0058] The problem of lithium-rich manganese-based cathode materials releasing oxygen during battery cycling and storage, leading to material structural instability and consequently poor cycle and storage performance of lithium-ion batteries, is addressed by traditional methods such as bulk doping, surface coating, and morphology control. These modification methods often require high-temperature treatment, which can affect the structure of the cathode material and result in long preparation cycles.

[0059] The lithium-ion battery preparation method disclosed in this application involves adding thiourea additives during the homogenization process of the positive electrode slurry. These thiourea additives can be uniformly mixed in the positive electrode slurry and synergistically participate in the lithium-ion insertion / extraction process, promoting lithium-ion insertion / extraction during charge and discharge. Furthermore, they can interact with lithium-rich manganese-based positive electrode materials, improving the structural stability of the materials and reducing manganese ion dissolution, thereby enhancing the cycle performance and storage performance of the lithium-ion battery. In addition, this preparation method eliminates the need for high-temperature treatment and post-treatment, resulting in a simple process and short preparation cycle.

[0060] Understandably, the positive electrode slurry may also optionally include conductive agents, binders, and solvents.

[0061] In some embodiments, the mass of thiourea additives in the cathode slurry is 0.3% to 1% of the mass of the lithium-rich manganese-based cathode material. Adding thiourea additives at a content of 0.3% to 1% of the mass of the lithium-rich manganese-based cathode material to the cathode slurry can enable lithium-ion batteries to obtain better cycle performance and storage performance.

[0062] It is understandable that the content of thiourea additives in the cathode slurry can be 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, 1% of the mass of the lithium-rich manganese-based cathode material, or any value within the range formed by any two of the above values.

[0063] In some embodiments, the mass of thiourea additives in the cathode slurry is 0.3% to 0.7% of the mass of the lithium-rich manganese-based cathode material. Thus, by controlling the amount of thiourea additives in the cathode slurry within the aforementioned range, the cycle performance and storage performance of the lithium-ion battery can be further improved.

[0064] In some embodiments, the thiourea additive includes one or more of thiourea, ethylene thiourea, propylene thiourea, and ammonia thiourea. Adding these types of thiourea additives to the cathode slurry can effectively reduce the leaching of transition metal manganese in lithium-rich manganese-based cathode materials and improve the structural stability of these materials, thereby effectively improving the cycle performance and storage performance of lithium-ion batteries. In some specific examples, the thiourea additive is thiourea.

[0065] In some embodiments, the evaporation temperature of the thiourea additive is higher than the drying temperature of the positive electrode slurry layer. This prevents the thiourea additive from evaporating during the drying process of the positive electrode slurry layer, allowing it to remain within the positive electrode active material layer. Generally, the drying temperature of the positive electrode slurry layer does not exceed 150°C.

[0066] In one embodiment of this application, an electrical device is provided, which includes one or more of the lithium-ion battery described above and the lithium-ion battery prepared by the method described above.

[0067] The lithium-ion battery and power device of this application will be described below with appropriate reference to the accompanying drawings.

[0068] In one embodiment of this application, a lithium-ion battery is provided.

[0069] Typically, a lithium-ion battery consists of 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 extracting. The electrolyte acts as a conductor 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.

[0070] The positive electrode includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector.

[0071] As a non-limiting example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0072] 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 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 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 polymeric 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).

[0073] In some embodiments, the positive electrode active material includes lithium-rich manganese-based positive electrode materials, and may also include other positive electrode active materials known in the art for use in batteries.

[0074] As a non-limiting example, the positive electrode active material of a lithium-ion battery may include one or more 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 of 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, one or more of 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 their modified compounds. Non-limiting examples of lithium phosphates with an olivine structure include, but are not limited to, one or more of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium iron manganese phosphate and carbon composites. Non-limiting examples of lithium cobalt oxides may include LiCoO2; non-limiting examples of lithium nickel oxides may include LiNiO2; non-limiting examples of lithium manganese oxides may include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxides may include LiNi 1 / 3Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi0.5 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. 0.85 Co 0.1 Al 0.05 O2.

[0075] Understandably, lithium (Li) is intercalated and deintercalated during the charging and discharging process of a battery, and the Li content in the positive electrode varies depending on the state of discharge. Unless otherwise specified, the Li content in the examples of positive electrode materials listed in this application refers to the initial state of the material. When a positive electrode material is applied to a positive electrode in a battery system, the Li content in the positive electrode material typically changes after charge-discharge cycles. The Li content can be measured using molar content, but is not limited to this. Regarding "Li content refers to the initial state of the material," the initial state of the material refers to its state before being added to the positive electrode slurry. It is understood that new materials obtained by appropriately modifying the listed positive electrode materials are also within the scope of positive electrode materials. The aforementioned appropriate modification refers to acceptable modification methods for the positive electrode material; non-limiting examples include coating modification.

[0076] In the examples of cathode materials in this application, the oxygen (O) content is only a theoretical value. Lattice oxygen release will cause changes in the molar content of oxygen, and the actual O content will fluctuate. The O content can be measured in molar content, but is not limited to this.

[0077] In some embodiments, the positive electrode active material layer may optionally include a binder. As a non-limiting 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. The binder accounts for 0% to 20% by weight of the positive electrode active material layer, based on the total weight of the positive electrode active material layer.

[0078] In some embodiments, the positive electrode active material 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. The conductive agent accounts for 0% to 20% by weight of the positive electrode active material layer, based on the total weight of the positive electrode active material layer.

[0079] In some embodiments, the positive electrode sheet can be prepared by dispersing the components used to prepare the positive electrode sheet, such as the positive active material, conductive agent, binder, and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry, wherein the solid content of the positive electrode slurry is 40wt%~80wt%, and the viscosity at room temperature is adjusted to 5000mPa·s~25000mPa·s. The positive electrode slurry is then coated onto the surface of the positive current collector, dried, and cold-pressed using a cold rolling mill to form the positive electrode sheet; the areal density of the positive electrode powder coating is 150mg / m². 2 ~350mg / m 2 The compaction density of the positive electrode sheet is 3.0 g / cm³. 3 ~3.6g / cm 3 3.3g / cm³ is an option. 3 ~3.5g / cm 3 .

[0080] The negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector, wherein the negative active material layer includes a negative active material.

[0081] 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 material layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0082] 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 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 the polymer 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 polymer 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).

[0083] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries.

[0084] As a non-limiting example, the negative electrode active material of a lithium-ion battery 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. 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 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.

[0085] In some embodiments, the negative electrode active material 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).

[0086] In some embodiments, the negative electrode active material 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.

[0087] In some embodiments, the negative electrode active material layer may also optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0088] 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 obtaining the negative electrode sheet after drying, cold pressing, and 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, deducting solvent) can be 75g / m². 2 ~220g / m 2 The compaction density of the negative electrode sheet can be 1.0 g / cm³. 3 ~1.8g / cm 3 .

[0089] 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.

[0090] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0091] In some embodiments, the electrolyte salt of the lithium-ion battery 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 difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0092] In some embodiments, the solvent may include one or more of the following: fluoroethylene carbonate (FEC), 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), butyl carbonate (BC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0093] 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.

[0094] In some embodiments, the additives in the electrolyte may include, but are not limited to, one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethyl ethylene carbonate (TFPC), etc.

[0095] In some embodiments, the lithium-ion battery 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.

[0096] In some embodiments, the material of the separator may include one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may 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 may be the same or different, without particular limitation.

[0097] In some embodiments, the thickness of the separator is 6 μm to 40 μm, and optionally 12 μm to 20 μm.

[0098] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0099] In some embodiments, the lithium-ion battery may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0100] In some embodiments, the outer packaging of the lithium-ion battery can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the lithium-ion battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; further, non-limiting examples of plastic may include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0101] A lithium-ion battery includes at least one battery cell. A lithium-ion battery may include one or more battery cells.

[0102] 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.

[0103] 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 The example shown is a square-structured battery cell 5.

[0104] In some implementations, refer to Figure 2The outer packaging may include a housing 51 and a cover plate 53. The housing 51 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 51 has an opening communicating with the receiving cavity, and the cover plate 53 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 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in a single battery cell 5 can be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0105] In some embodiments, the battery cells 5 can be assembled into a battery module, and the number of battery cells 5 contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0106] In the battery module, multiple battery cells 5 can be arranged sequentially along the length of the battery module. Of course, they can also be arranged in any other manner. Furthermore, these multiple battery cells 5 can be secured with fasteners.

[0107] Optionally, the battery module may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0108] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0109] 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.

[0110] In addition, this application also provides an electrical device, which includes at least one of the lithium-ion battery, battery module, or battery pack provided in this application. The lithium-ion battery, battery module, or battery pack 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.

[0111] As an electrical device, lithium-ion batteries, battery modules, or battery packs can be selected according to their usage requirements.

[0112] Figure 3 Here is an example of an electrical device 6. 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 lithium-ion batteries for this electrical device, a battery pack or battery module can be used.

[0113] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use lithium-ion batteries as their power source.

[0114] The following are some examples.

[0115] 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.

[0116] 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.

[0117] Example 1:

[0118] (1) Preparation of positive electrode sheet

[0119] The specific surface area of ​​BET is 1.6m². 2 / g of lithium-rich manganese-based cathode material Li 1.13 Mn 0.56 Ni 0.29 Al 0.02 O2 was added to a 5L mixing tank and premixed for 30 minutes. Then, acetylene black (SP), 0.3 wt% of lithium-rich manganese-based cathode material (propylene thiourea), and polyvinylidene fluoride (PVDF) binder were added for a second dry mixing process of 30 minutes. Next, N-methylpyrrolidone (NMP) solvent was added and the mixture was rapidly stirred under vacuum to form a cathode slurry. The mass ratio of the cathode active material mixture (lithium-rich manganese-based cathode material + propylene thiourea):acetylene black:polyvinylidene fluoride was 96:2:2, and the solid content of the cathode slurry was 68.6 wt%.

[0120] The positive electrode slurry was uniformly coated onto both sides of a 12 μm thick aluminum foil. The coated electrode was then dried in an oven at 100℃ for half an hour to obtain the positive electrode sheet. The positive electrode active material loading of the positive electrode sheet was 20.1 mg / cm³. 2 .

[0121] (2) Preparation of negative electrode sheet

[0122] Artificial graphite and hard carbon, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) are thoroughly mixed in a deionized water solvent system at a weight ratio of 90:5:2:2:1 to obtain a negative electrode slurry. The negative electrode slurry is coated onto copper foil, dried, and cold-pressed to obtain a negative electrode sheet.

[0123] (3) Separating membrane

[0124] A polyethylene film with a thickness of 13 μm was used as the separator.

[0125] (4) Battery assembly

[0126] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The cells are then wound to obtain a bare cell. The bare cell is placed in an outer packaging, and the prepared basic electrolyte, 1 mol / L LiPF6 / (EC+EMC+DMC) (volume ratio 1:1:1), is injected and sealed to obtain a full cell.

[0127] Example 2:

[0128] This embodiment is basically the same as that of embodiment 1, except that: in step (1), the amount of propylene thiourea used is 0.1 wt% of the mass of the lithium-rich manganese-based cathode material.

[0129] Example 3:

[0130] This embodiment is basically the same as that of embodiment 1, except that: in step (1), the amount of propylene thiourea used is 0.5 wt% of the mass of the lithium-rich manganese-based cathode material.

[0131] Example 4:

[0132] This embodiment is basically the same as that of embodiment 1, except that: in step (1), the amount of propylene thiourea used is 0.7 wt% of the mass of the lithium-rich manganese-based cathode material.

[0133] Example 5:

[0134] This embodiment is basically the same as embodiment 1, except that: in step (1), the amount of propylene thiourea used is 1 wt% of the mass of the lithium-rich manganese-based cathode material.

[0135] Example 6:

[0136] This embodiment is basically the same as that of embodiment 1, except that: in step (1), thiourea is used instead of propylene thiourea, and the amount of thiourea is 0.1 wt% of the mass of the lithium-rich manganese-based cathode material.

[0137] Example 7:

[0138] This embodiment is basically the same as embodiment 1, except that thiourea is used instead of propylene thiourea in step (1).

[0139] Example 8:

[0140] This embodiment is basically the same as embodiment 1, except that: in step (1), thiourea is used instead of propylene thiourea, and the amount of thiourea is 0.5 wt% of the mass of the lithium-rich manganese-based cathode material.

[0141] Example 9:

[0142] This embodiment is basically the same as that of embodiment 1, except that: in step (1), thiourea is used instead of propylene thiourea, and the amount of thiourea is 0.7 wt% of the mass of the lithium-rich manganese-based cathode material.

[0143] Example 10:

[0144] This embodiment is basically the same as embodiment 1, except that: in step (1), thiourea is used instead of propylene thiourea, and the amount of thiourea is 1 wt% of the mass of the lithium-rich manganese-based cathode material.

[0145] Example 11:

[0146] This embodiment is basically the same as Embodiment 1, except that the BET specific surface area of ​​the lithium-rich manganese-based cathode material in step (1) is 1.0 m². 2 / g.

[0147] Example 12:

[0148] This embodiment is basically the same as Embodiment 1, except that the BET specific surface area of ​​the lithium-rich manganese-based cathode material in step (1) is 2.0 m². 2 / g.

[0149] Example 13:

[0150] This embodiment is basically the same as Embodiment 1, except that: the chemical formula of the lithium-rich manganese-based cathode material in step (1) is: Li 1.13 Mn 0.55 Co 0.02 Ni 0.28 Al 0.02 O2.

[0151] Comparative Example 1:

[0152] This comparative example is basically the same as Example 1, except that: thiourea is not added in step (1).

[0153] Test method:

[0154] (1) Test method for thiourea additive content

[0155] The positive electrode active material layer is digested into a solution, and the content of characteristic elements is measured by ICP, thereby obtaining the mass of lithium-rich manganese-based positive electrode material and thiourea additives in the positive electrode active material layer.

[0156] The mass percentage of thiourea additives relative to the mass of lithium-rich manganese-based cathode material is obtained by multiplying the mass of thiourea additives by the mass of lithium-rich manganese-based cathode material by 100%.

[0157] (2) BET testing method

[0158] The test method is based on the national standard GB / T 19587-2004.

[0159] (3) Test of Mn dissolution in cathode material

[0160] The solute used is ascorbic acid, and the specific test method is as follows:

[0161] ① Weigh 1 ± 0.01 g of sample scraped from the positive electrode and add it to a beaker;

[0162] ② Add 50mL of ultrapure water to a 150mL beaker, slowly add an appropriate amount of ascorbic acid powder (VC), and sonicate for 5 minutes until completely dissolved to obtain a VC solution;

[0163] ③ Measure out the prepared VC solution and add it to the beaker in ①. After adding a small magnetic stir bar, seal the beaker and stir magnetically at a speed of 500 rpm. The process is as follows: stir magnetically for 5 min, let stand for 24 min, stir magnetically for 1 min.

[0164] ④ Take the stirred solution and filter it into a 4mL test tube;

[0165] ⑤ Add 2 mL of nitric acid to a 100 mL glass volumetric flask, then take 1 mL of filtrate from the test tube in the previous step and add it to the volumetric flask to make up to volume.

[0166] ⑥ Use inductively coupled plasma optical emission spectroscopy (ICP-OES) to test the concentration of Mn element, input the dilution factor and the fixed volume / sample mass, and record the experimental results Mn / ppm.

[0167] (4) Battery cell storage performance testing method

[0168] Under constant temperature of 25℃, let stand for 5 minutes, discharge at 1 / 3C to 2.5V, let stand for 5 minutes, charge at 1 / 3C to 4.5V, then charge at 4.5V at constant voltage until the current is ≤0.05mA, let stand for 5 minutes, and record the charging capacity at this time as C0. Then discharge at 1 / 3C to 2.8V, and record the discharge capacity at this time as the initial specific capacity as D0. The first efficiency is D0 / C0*100%.

[0169] Then, the battery was charged from 0.33C constant current to 4.5V and constant voltage until the current ≤0.05mA. After standing for 5 minutes, it was placed in a 60℃ temperature chamber and left to stand for 1 hour until the battery temperature reached the target temperature of 60℃ before storage. After 15 days, it was taken out and the previous process was repeated in a constant temperature environment of 25℃. The capacity Dn (n=0, 1, 2...) was recorded every 15 days. The capacity retention rate after 60 days of storage was calculated as: (D4-D0) / D0*100%.

[0170] (5) Battery cell cycle performance testing method

[0171] Battery cell cycle retention rate (%): Using a full cell as the test object, under a constant temperature environment of 25℃, the cell is charged at a rate of 0.5C to 4.43V at a voltage of 2.5V~4.43V, and then charged at a constant voltage of 4.43V until the current is ≤0.05mA. After resting for 5 minutes, the cell is discharged at a rate of 0.2C to 2.5V, and the discharge capacity is recorded. The previous process is repeated to obtain the capacity retention rate after 300 cycles. Capacity retention rate = discharge capacity in the first cycle / discharge capacity at the specified number of cycles × 100%.

[0172] (6) Discharge capacity test

[0173] Assemble the CR2032 button cell in an argon-filled glove box. The assembly sequence from top to bottom is: positive electrode shell, positive electrode plate, separator, negative electrode plate, steel plate, spring plate, and negative electrode shell. After assembly, let it stand for 6 hours for later use.

[0174] Using a coin cell as the test object, it is charged to 4.55V at a rate of 0.33C within a voltage range of 2.5V to 4.55V, and then charged at a constant voltage at 4.55V until the current is ≤0.05mA. After resting for 2 minutes, the charging capacity at this time is recorded as C0. Then it is discharged to 2.5V at a rate of 0.33C. The discharge capacity at this time is the gram capacity, recorded as D0.

[0175] The parameters and performance data of the lithium-ion batteries in the above embodiments and comparative examples are shown in Tables 1 and 2. " / " indicates that the battery does not exist.

[0176] Table 1

[0177]

[0178] Table 2

[0179]

[0180] As shown in Tables 1 and 2, this application can effectively reduce the dissolution of transition metal Mn in lithium-rich manganese-based cathode materials by adding thiourea additives to the cathode active material layer, thereby enabling lithium-ion batteries using lithium-rich manganese-based cathode materials to have better cycle performance and better storage performance. At the same time, the addition of thiourea additives will not have a significant adverse effect on the discharge capacity of lithium-ion batteries.

[0181] The description of the various embodiments above tends to emphasize the differences between the various embodiments. The similarities or similarities between them can be referred to, and for the sake of brevity, they will not be repeated here.

[0182] 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 lithium ion battery, comprising a positive electrode sheet, the positive electrode sheet comprising a positive electrode active material layer, the positive electrode active material layer comprising a lithium-rich manganese-based positive electrode material and a thioureido additive.

2. The lithium-ion battery of claim 1, wherein, The mass of the thioureido additive in the positive electrode active material layer is 0.3%to 1%of the mass of the lithium-rich manganese-based positive electrode material.

3. The lithium-ion battery of claim 2, wherein, The mass of the thioureido additive in the positive electrode active material layer is 0.3%to 0.7%of the mass of the lithium-rich manganese-based positive electrode material.

4. The lithium-ion battery of any one of claims 1-3, wherein, The thioureido additive comprises one or more of thiourea, ethylenethiourea, propylenethiourea, and thiosemicarbazide.

5. The lithium-ion battery of any one of claims 1-3, wherein, The BET specific surface area of the lithium-rich manganese-based positive electrode material is 1.0 m 2 / g~2.0 m 2 / g.

6. The lithium-ion battery of any one of claims 1-3, wherein, The manganese elution amount of the lithium-rich manganese-based positive electrode material is less than 80 ppm.

7. The lithium-ion battery of any one of claims 1-3, wherein, The lithium-rich manganese-based positive electrode material has a chemical formula of Li[Li x Ni a Co b Mn c M d ]O2, wherein x+a+b+c+d=1, x>0, a>0, 0≤b≤0.1, c≥0.5, d>0, a+b+c+d<1; M is one or more of Mg, Nb, Cr, Ce, Fe, Ta, Al, V, Ti, Zr, Sn and Mo. 8.A method for preparing a lithium ion battery, comprising the following steps: mixing a lithium-rich manganese-based positive electrode material and a thioureido additive to obtain a positive electrode slurry; arranging the positive electrode slurry on a positive electrode current collector to form a positive electrode slurry layer, and drying to obtain a positive electrode sheet.

9. The method of producing a lithium-ion battery according to claim 8, wherein, The mass of the thioureido additive in the positive electrode slurry is 0.3%to 1%of the mass of the lithium-rich manganese-based positive electrode material.

10. The method of producing a lithium-ion battery according to claim 9, wherein, The mass of the thioureido additive in the positive electrode slurry is 0.3%to 0.7%of the mass of the lithium-rich manganese-based positive electrode material.

11. The method of producing a lithium-ion battery according to any one of claims 8 to 10, wherein, The thioureido additive comprises one or more of thiourea, ethylenethiourea, propylenethiourea, and thiosemicarbazide. 12.A positive electrode slurry, comprising a lithium-rich manganese-based positive electrode material and a thioureido additive. 13.A positive electrode sheet, comprising a positive electrode active material layer, the positive electrode active material layer comprising a lithium-rich manganese-based positive electrode material and a thioureido additive.

14. The cathode sheet of claim 13, wherein, The thioureido additive comprises one or more of thiourea, ethylenethiourea, propylenethiourea, and thiosemicarbazide. 15.An electric device, comprising one or more of the lithium ion battery of any one of claims 1 to 7 and the lithium ion battery prepared by the method for preparing a lithium ion battery of any one of claims 8 to 11.

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