Lithium ion battery, preparation method of positive active material and electric device

Abstract

This application provides a lithium-ion battery, a method for preparing a positive electrode active material, and an electrical device. The lithium-ion battery includes a positive electrode, a negative electrode, and an electrolyte. The positive electrode includes a positive current collector and a positive active layer located on at least one surface of the positive current collector. The positive active material of the positive active layer includes a lithium-containing transition metal oxide, which includes lithium, non-lithium alkali metal elements, and transition metal elements, including nickel, cobalt, and manganese. In the fully discharged state of the lithium-ion battery, the molar percentage of non-lithium alkali metal elements is 0.5% to 10% of the total molar amount of lithium and non-lithium alkali metal elements. Introducing 0.5% to 10% of non-lithium alkali metal elements into the lithium-containing transition metal oxide can suppress the dissolution of manganese and improve the battery's storage performance.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a lithium-ion battery, a method for preparing a positive electrode active material, and an electrical device thereof. Background Technology

[0002] In recent years, lithium-ion batteries and other batteries have been 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 continuous expansion of the application range of lithium-ion batteries, correspondingly higher requirements are being placed 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. The lithium-ion battery includes a positive electrode, a negative electrode, and an electrolyte; the positive electrode includes a positive current collector and a positive active layer located on at least one surface of the positive current collector, the positive active material of the positive active layer including a lithium-containing transition metal oxide, the lithium-containing transition metal oxide including lithium, non-lithium alkali metal elements, and transition metal elements, the transition metal elements including nickel, cobalt, and manganese; in the fully discharged state of the lithium-ion battery, the molar percentage of the non-lithium alkali metal elements, based on the total molar amount of the lithium and the non-lithium alkali metal elements, is 0.5% to 10%.

[0004] In the aforementioned lithium-ion batteries, introducing non-lithium alkali metal elements with a molar percentage of 0.5% to 10% into lithium-containing transition metal oxides can suppress the dissolution of manganese and improve the battery's storage performance.

[0005] In some embodiments, when the lithium-ion battery is fully discharged, the molar percentage of nickel is 50% to 60%, the molar percentage of cobalt is 0 to 10%, and the molar percentage of manganese is 10% to 50% based on the total molar amount of nickel, cobalt, and manganese.

[0006] In some embodiments, the non-lithium alkali metal element includes one or more of sodium and potassium.

[0007] In some embodiments, the lithium-containing transition metal oxide comprises Li 1-x M x (Ni a Co b Mn c ) 1- d Z d O 2-y Ay The material has the following properties: 0.005≤x≤0.1, 0.5≤a≤0.6, 0≤b≤0.1, 0.1≤c≤0.5, a+b+c=1, 0≤d<1, 0≤y<2, M includes one or more of non-lithium alkali metal elements, Z includes one or more of Zr, Sr, B, Sn, Al, Mg, Fe, Cu, V, Ti, Zr, W, Sb, Dy and Te, and A includes one or more of N, P, S and halogen elements.

[0008] The second aspect of this application provides a method for preparing a positive electrode active material, comprising the following steps: mixing raw materials to obtain a mixture, wherein the raw materials include a nickel-cobalt-manganese precursor, a lithium source, and a non-lithium alkali metal source, wherein the molar percentage of the non-lithium alkali metal element is 0.5% to 10% based on the total molar amount of lithium element in the lithium source and non-lithium alkali metal element in the non-lithium alkali metal source; and sintering the mixture.

[0009] In some embodiments, the nickel-cobalt-manganese precursor contains, by percentage of the total molar amount of nickel, cobalt, and manganese, nickel at a molar percentage of 50% to 60%, cobalt at a molar percentage of 0 to 10%, and manganese at a molar percentage of 10% to 50%.

[0010] In some embodiments, the non-lithium alkali metal source comprises two or more non-lithium alkali metal compounds with different melting points. A eutectic is formed using two or more non-lithium alkali metal compounds with different melting points. The melting point of the eutectic can be controlled by adjusting the proportions of the two or more non-lithium alkali metal compounds with different melting points, thus facilitating the control of the sintering temperature.

[0011] In some embodiments, two or more of the aforementioned non-lithium alkali metal compounds comprise the same non-lithium alkali metal element.

[0012] In some embodiments, the non-lithium alkali metal compound includes non-lithium alkali metal carbonates and non-lithium alkali metal hydroxides.

[0013] In some embodiments, the raw materials used in the preparation also include sintering aids.

[0014] In some embodiments, the sintering aid includes one or more of sodium chloride and potassium chloride.

[0015] In some embodiments, the ratio of the total molar amount of nickel, cobalt and manganese in the nickel-cobalt-manganese precursor to the molar amount of the sintering aid is 1:(0.1~0.3).

[0016] In some embodiments, the sintering temperature is 700°C to 1000°C.

[0017] In some embodiments, the sintering process takes 10 to 20 hours.

[0018] A third aspect of this application provides an electrical device including the lithium-ion battery of the first aspect. Attached Figure Description

[0019] 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:

[0020] Figure 1 This is a schematic diagram of a lithium-ion battery according to one embodiment of this application.

[0021] Figure 2 for Figure 1 An exploded view of a lithium-ion battery according to an embodiment of this application is shown.

[0022] 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.

[0023] Figure 4 This is a comparison chart showing the content of manganese, nickel, and cobalt in the negative electrode of the lithium-ion batteries after storage in Example 1 and Comparative Example 1.

[0024] Figure 5 This is a comparison diagram of the lithium plating state of the negative electrode before and after storage in Example 1 of this application.

[0025] Figure 6 This is a comparison diagram of the lithium plating state of the negative electrode before and after storage in Comparative Example 1 of this application.

[0026] Explanation of reference numerals in the attached figures:

[0027] 1. Lithium-ion battery; 11. Casing; 12. Electrode assembly; 13. Cover plate; 2. Electrical device. Detailed Implementation

[0028] To facilitate understanding of this application, a more comprehensive description will be provided below with reference to the accompanying drawings; however, some unnecessary details may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of essentially the same structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the scope of protection of this application.

[0029] 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 the specific range. Ranges defined in this way can include or exclude endpoints. Any endpoint can be included or excluded independently, 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 ​​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 "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.

[0030] In this application, unless otherwise specified, "about" means within a reasonable range above and below the stated number, and the range of fluctuation may vary depending on the type and value of the stated number. For example, a range of ±10%, ±5%, ±2%, ±1% is permissible. For instance, taking "about 20°C" as an example, where the approximation is ±1°C, approximate values ​​such as 19°C and 19.5°C within the approximation range indicated by "about 20°C" should also be included in the range indicated by "about 20°C".

[0031] In this application, the terms "multiple," "various," "multiple items," "several," etc., unless otherwise specified, refer to a quantity greater than or equal to 2. For example, "one or more" means one or more items. It can be understood that when "any number of" items are involved, it refers to any suitable combination of multiple items, that is, a combination of "any number of" items in a manner that does not conflict and enables the implementation of this application.

[0032] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0033] In this application, the reference to "embodiment" means that a specific 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.

[0034] 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, but are preferably performed sequentially. For example, if method M 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, method M may also include step (c), meaning that step (c) can be added to method M in any order. For example, method M 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.

[0035] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it is selected from either "with" or "without." If multiple "options" appear in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "option" is independent. Unless otherwise specified, the descriptions such as "optionally include" and "optionally contain" in this application, taking "optionally include" as an example, mean "may include or not include."

[0036] In this application, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. Any and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "M and / or N" represents a group consisting of M, N, and "a combination of M and N". "Containing M and / or N" can mean "containing M, containing N, and containing both M and N", or "containing M, containing N, or containing both M and N", and can be appropriately understood according to the context.

[0037] The terms “combinations thereof,” “any combination thereof,” and “any combination thereof” as used in this application include all suitable combinations of any two or more of the listed items.

[0038] In this application, the term "suitable" in "suitable combination", "suitable method", "any suitable method", etc., refers to the technical solution that can implement this application.

[0039] In this application, terms such as "further," "even more," "especially," "for example," "as," "example," and "exemplary" are used for descriptive purposes to indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0040] In this application, the terms "first aspect," "second aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first aspect," "second aspect," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on quantity.

[0041] In this application, unless otherwise expressly specified and limited, the phrase "above" or "below" the second feature can mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. In this application, unless otherwise expressly specified and limited, the phrase "above" or "below" the second feature can indicate a horizontal positional relationship, or it can simply indicate the existence of an attachment relationship without specifying a horizontal positional relationship.

[0042] In this application, the terms "room temperature" and "normal temperature" generally refer to 4℃~35℃, and may refer to 20℃±5℃. In some embodiments or examples of this application, room temperature and normal temperature may refer to 20℃~30℃.

[0043] In this application, if the unit for a data range is only followed by the right endpoint, it indicates that the units for the left and right endpoints are the same. For example, 3~5h or 3~5h both mean that the unit for the left endpoint "3" and the right endpoint "5" is h (hours), and both have the same meaning as 3h~5h. Furthermore, similar descriptions of other parameters such as temperature and size are interpreted in the same way.

[0044] In this application, the exemplary descriptions such as "in some implementations or embodiments" and "in one implementation or embodiment" may cover, but are not limited to, the following meanings: these solutions can be combined with other solutions in a suitable manner to form new technical solutions.

[0045] In this application, unless otherwise specified, "lithium-ion battery" refers to a basic unit capable of converting chemical energy into electrical energy, and more generally includes a positive electrode, a negative electrode, and an electrolyte. During the charging and discharging process, active ions repeatedly insert and extract between the positive and negative electrode. The electrolyte acts as a conductor for the active ions between the positive and negative electrode.

[0046] In some implementations, lithium-ion batteries can be either power batteries or energy storage batteries.

[0047] In lithium-ion batteries, lithium-containing transition metal oxides (LMOs) are among the most widely used positive electrode active materials. The main transition metal elements in LMOs include nickel, cobalt, and manganese. Reducing the cobalt content and increasing the manganese content helps reduce the amount of precious cobalt used, thus lowering the manufacturing cost of LMOs. However, with the increase in manganese content, the amount of manganese dissolved from the positive electrode increases after LMOs are used in the battery. When this dissolved manganese is transported to the negative electrode, it deposits there, damaging the SEI film. This increases side reactions between the electrolyte and the negative electrode active material, leading to increased consumption of active lithium and ultimately reducing the battery's storage performance.

[0048] Based on this, one embodiment of this application provides a lithium-ion battery. The lithium-ion battery includes a positive electrode, a negative electrode, and an electrolyte. The positive electrode includes a positive current collector and a positive active layer located on at least one surface of the positive current collector. The positive active material of the positive active layer includes a lithium-containing transition metal oxide, which includes lithium, non-lithium alkali metal elements, and transition metal elements, including nickel, cobalt, and manganese. In the fully discharged state of the lithium-ion battery, the molar percentage of non-lithium alkali metal elements, based on the total molar amount of lithium and non-lithium alkali metal elements, is 0.5% to 10%.

[0049] In the lithium-ion battery of this embodiment, the introduction of a non-lithium alkali metal element with a molar percentage of 0.5% to 10% into the lithium-containing transition metal oxide can suppress the dissolution of manganese and improve the battery's storage performance. Simultaneously, a molar percentage of non-lithium alkali metal elements of less than or equal to 10% in the lithium-containing transition metal oxide can maintain a high lithium content, which is beneficial for achieving a high energy density in the battery.

[0050] Specifically, the atomic radius of non-lithium alkali metal elements is larger than that of lithium. Compared with the crystal phase formed by lithium atoms, oxygen atoms, and manganese atoms, the crystal phase formed by non-lithium alkali metal atoms, oxygen atoms, and manganese atoms is more likely to combine with high-valence manganese elements, such as tetravalent manganese elements. This can effectively reduce the transformation of high-valence manganese elements to low-valence manganese elements, suppress the Jan Taylor effect of trivalent manganese elements, and thus reduce the dissolution of manganese elements.

[0051] Furthermore, the lithium-nickel mixture present in lithium-containing transition metal oxides alters the electron cloud distribution, potentially causing the lithium-ion reduction potential to advance during charging. This makes lithium-ions more easily reduced to metallic lithium on the negative electrode surface, increasing the risk of lithium plating. In the lithium-ion battery of this embodiment, by introducing an appropriate proportion of non-lithium alkali metal elements into the lithium-containing transition metal oxide, the lithium-nickel mixture in the lithium-containing transition metal oxide can be reduced, which helps to lower the risk of lithium plating at the battery negative electrode.

[0052] It is understandable that non-lithium alkali metal elements refer to alkali metal elements other than lithium.

[0053] It is understandable that the fully discharged state of a lithium-ion battery refers to the state in which the lithium-ion battery is discharged to the discharge cutoff voltage. Optionally, a fully discharged lithium-ion battery can be obtained by discharging it at a constant current of 0.33C to the cutoff voltage.

[0054] Optionally, the lithium-containing transition metal oxide has a layered structure. Non-lithium alkali metal elements can be doped into the lithium layer containing lithium transition metal elements, and stabilize the layered structure of the lithium-containing transition metal oxide through the pillar effect. This helps to maintain the good structural stability of the lithium-containing transition metal oxide and further improves the storage performance of the battery.

[0055] In some implementations, when the lithium-ion battery is fully discharged, the molar percentage of nickel is 50% to 60%, the molar percentage of cobalt is 0 to 10%, and the molar percentage of manganese is 10% to 50% based on the total molar amount of nickel, cobalt, and manganese.

[0056] In this application, the molar percentages of nickel, cobalt, manganese, and non-lithium alkali metals can be measured using inductively coupled plasma spectrometry (ICP) and scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDS).

[0057] In this application, when testing the molar percentage of nickel, cobalt, manganese, and non-lithium alkali metal elements, the lithium-ion battery is discharged to a fully discharged state, the battery is disassembled to obtain the positive electrode sheet, and the organic components such as binders in the positive electrode active layer are dissolved in a solvent to obtain the positive electrode active material, which is then tested. The solvent may optionally include one or more of dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC).

[0058] Optionally, the molar percentage of nickel, in terms of the total molar amount of nickel, cobalt, and manganese, is 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, or any value within the range of any two of the above values.

[0059] Optionally, the molar percentage of cobalt, as a percentage of the total molar amount of nickel, cobalt, and manganese, can be 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0, or any value within the range of any two of the above values. It is understood that the molar percentage of cobalt can be 0, indicating that the cobalt content in the lithium-containing transition metal oxide is 0.

[0060] Optionally, the molar percentage of manganese, as a percentage of the total molar amount of nickel, cobalt, and manganese, is 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or any value within the range of any two of the above values.

[0061] Optionally, the molar percentage of non-lithium alkali metal elements, expressed as a percentage of the total molar amount of lithium and non-lithium alkali metal elements, is 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any value within the range of any two of the above values.

[0062] In some implementations, the non-lithium alkali metal element includes one or more of sodium and potassium.

[0063] In some implementations, the lithium-containing transition metal oxide comprises single-crystal particles.

[0064] In some embodiments, the Dv50 of the positive electrode active material is 3 μm to 6 μm. Optionally, the Dv50 of the positive electrode active material can be 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, or any value within the range of any two of the above values.

[0065] In this application, Dv50 represents the particle size corresponding to a cumulative volumetric distribution percentage of 50%. It can be determined using a laser particle size analyzer according to standard GB / T 19077-2016. The laser particle size analyzer can be a Malvern Master Size 3000.

[0066] Optionally, lithium-containing transition metal oxides include those with the chemical formula Li 1-x M x (Ni a Co b Mn c ) 1-d Z d O 2-y A y The material has the following properties: 0.005≤x≤0.1, 0.5≤a≤0.6, 0≤b≤0.1, 0.1≤c≤0.5, a+b+c=1, 0≤d<1, 0≤y<2, M includes one or more of non-lithium alkali metal elements, Z includes one or more of Zr, Sr, B, Sn, Al, Mg, Fe, Cu, V, Ti, Zr, W, Sb, Dy and Te, and A includes one or more of N, P, S and halogen elements.

[0067] Optionally, M is selected from one or more non-lithium alkali metal elements, Z is selected from one or more of Zr, Sr, B, Sn, Al, Mg, Fe, Cu, V, Ti, Zr, W, Sb, Dy and Te, and A includes one or more of N, P, S and halogen elements.

[0068] Optionally, the lithium-containing transition metal oxide has the chemical formula Li. 1-x M x (Ni a Co b Mn c ) 1-d Z d O 2-y A y .

[0069] Understandably, 'a' can be used to represent the nickel content in lithium-containing transition metal oxides. A larger 'a' indicates a higher nickel content, while a smaller 'a' indicates a lower nickel content. As some possible examples of 'a', 'a' can be 0.5, 0.51, 0.52, 0.53, 0.54, 0.55, 0.56, 0.57, 0.58, 0.59, 0.6, or any value within the range of any two of the above values.

[0070] Understandably, 'b' can be used to represent the cobalt content in lithium-containing transition metal oxides. A larger 'b' indicates a higher cobalt content in the lithium-containing transition metal oxide, while a smaller 'b' indicates a lower cobalt content. As some possible examples of 'b', it can be 0.1, 0.09, 0.08, 0.07, 0.06, 0.05, 0.04, 0.03, 0.02, 0.01, 0, or any value within the range of any two of the above values.

[0071] Understandably, 'c' can be used to represent the manganese content in lithium-containing transition metal oxides. A larger 'c' indicates a higher manganese content, while a smaller 'c' indicates a lower manganese content. As some optional examples of 'c', 'c' can be 0.1, 0.2, 0.3, 0.4, 0.5, or any value within the range of any two of the above values.

[0072] Understandably, x can be used to represent the content of non-lithium alkali metal elements in lithium-containing transition metal oxides. The larger the x, the higher the content of non-lithium alkali metal elements in the lithium-containing transition metal oxide; the smaller the x, the lower the content of non-lithium alkali metal elements in the lithium-containing transition metal oxide. As some optional examples of x, x can be 0.005, 0.006, 0.007, 0.008, 0.009, 0.1, and any value within the range of any two of the above values.

[0073] Understandably, d is typically used to represent the Z element content in lithium-containing transition metal oxides. A larger d indicates a higher Z element content, while a smaller d indicates a lower Z element content. As some possible examples of d, d can be 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and any value within the range of any two of the above values. Optionally, 0 ≤ d ≤ 0.05.

[0074] Understandably, y is typically used to represent the content of element A in lithium-containing transition metal oxides. A larger y indicates a higher content of element A, while a smaller y indicates a lower content of element A. As some possible examples of y, y can be 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 1.91, 1.92, 1.93, 1.94, 1.95, 1.96, 1.97, 1.98, 1.99, and any value within the range of any two of the above values. Optionally, 0 ≤ y ≤ 0.05.

[0075] It is understandable that A includes one or more of N, P, S and halogen elements, where halogen elements can be F, Cl, Br, etc.

[0076] Optionally, the lithium-containing transition metal oxide includes Li 0.98 Na 0.02 Ni 0.55 Co 0.06 Mn 0.39 O2, Li 0.95 Na 0.05 Ni 0.55 Co 0.06 Mn 0.39 O2, Li 0.92 Na 0.08 Ni 0.55 Co 0.06 Mn 0.39 O2 and Li 0.9 Na 0.1 Ni 0.55 Co 0.06 Mn 0.39 One or more of O2.

[0077] Optionally, the lithium-containing transition metal oxide accounts for 90% to 100% of the mass of the positive electrode active material. Optionally, the mass percentage of the lithium-containing transition metal oxide in the positive electrode active material can be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or any value within the range of any two of the above values.

[0078] In some embodiments, the positive electrode active material may include, in addition to lithium-containing transition metal oxides, positive electrode active materials known in the art for use in batteries.

[0079] In some embodiments, the positive electrode active material may further include one or more of the following materials: lithium cobalt oxide, lithium manganese oxide, lithium manganese cobalt oxide, and modified compounds thereof. Non-limiting examples of lithium cobalt oxide may include LiCoO2. Non-limiting examples of lithium manganese oxide may include LiMnO2, LiMn2O4, etc.

[0080] In some embodiments, the positive electrode active material may further include lithium phosphate. Lithium phosphate has a higher cycle life, which can further improve the cycle performance of the battery. Optionally, the lithium phosphate accounts for 0% to 10% of the mass of the positive electrode active material. Optionally, the mass percentage of lithium phosphate in the positive electrode active material can be 0%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any value within the range of any two of the above values.

[0081] Optionally, lithium-containing phosphates may include at least one of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites. Lithium-containing phosphates may also include one or more of lithium manganese phosphate and lithium manganese phosphate and carbon composites.

[0082] In some embodiments, the positive electrode active material accounts for 90% to 99% of the mass percentage of the positive electrode active layer. A mass percentage greater than or equal to 90% allows for a higher concentration of positive electrode active material in the active layer, providing more reactive sites and further improving the cycle performance of the lithium-ion battery. Simultaneously, a higher concentration of positive electrode active material can also improve the energy density of the lithium-ion battery, resulting in a higher energy density. A mass percentage less than or equal to 99% allows for appropriate content of functional additives such as conductive agents and binders in the active layer, which is beneficial for improving the overall performance of the positive electrode sheet. Optionally, the mass percentage of the positive electrode active material in the active layer can be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or any value within the range of any two of the above values.

[0083] 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 (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins. Optionally, the binder accounts for 0.5% to 5% of the mass percentage of the positive electrode active layer. Optionally, the mass percentage of the binder in the positive electrode active layer may be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or any value within the range of any two of the above values.

[0084] 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. Optionally, the conductive agent accounts for 0.1% to 5% of the mass percentage of the positive electrode active layer. Optionally, the mass percentage of the conductive agent in the positive electrode active layer may be 0.1%, 0.3%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or any value within the range of any two of the above values.

[0085] 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).

[0086] 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 electrode active material, conductive agent, binder, and any other components, in a solvent to form a positive electrode slurry; coating the positive electrode slurry onto at least one surface of the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing, and other processes. The solvent can be selected from, but is not limited to, any of the solvents described in the foregoing embodiments, such as N-methylpyrrolidone (NMP). The surface of the positive electrode current collector coated with the positive electrode slurry can be a single surface of the positive electrode current collector or both surfaces of the positive electrode current collector.

[0087] In some implementations, the mass percentage of manganese in the negative electrode of a lithium-ion battery under full charge is less than or equal to 200 ppm. In these implementations, by designing the positive electrode active material, the mass percentage of manganese in the negative electrode under full charge can be effectively reduced, decreasing the risk of SEI film damage and further improving battery storage performance. For example, under full charge, the mass percentage of manganese in the negative electrode of a lithium-ion battery is between 10 ppm and 200 ppm.

[0088] Optionally, the mass percentage of manganese in the negative electrode can be tested using ICP or SEM-EDS.

[0089] Optionally, when testing the mass percentage of manganese in the negative electrode, the lithium ions are charged to a full charge, the battery is disassembled to obtain the negative electrode, and the mass percentage of manganese in the negative electrode is tested.

[0090] It is understandable that a fully charged lithium-ion battery represents the state of the lithium-ion battery when it is charged to the charging cutoff voltage. Optionally, a fully charged lithium-ion battery can be obtained by charging the lithium-ion battery at a constant current of 0.33C to the charging cutoff voltage, and then charging it at a constant voltage until the current is less than or equal to 0.05C.

[0091] Another embodiment of this application provides a positive electrode active material. The positive electrode active material includes a lithium-containing transition metal oxide, which includes lithium, non-lithium alkali metal elements, and transition metal elements, including nickel, cobalt, and manganese; the molar percentage of non-lithium alkali metal elements is 0.5% to 10% of the total molar amount of lithium and non-lithium alkali metal elements.

[0092] Furthermore, in terms of the percentage of the total molar amount of nickel, cobalt, and manganese, the molar percentage of nickel is 50% to 60%, the molar percentage of cobalt is 0% to 10%, and the molar percentage of manganese is 10% to 50%.

[0093] Optionally, the non-lithium alkali metal elements include one or more of sodium and potassium.

[0094] It is understandable that the relevant parameters in the positive electrode active material can be selected from the description of lithium-ion batteries above, and will not be repeated here.

[0095] Another embodiment of this application provides a method for preparing a positive electrode active material. The method includes the following steps: mixing raw materials to obtain a mixture, the raw materials including a nickel-cobalt-manganese precursor, a lithium source, and a non-lithium alkali metal source, wherein the molar percentage of the non-lithium alkali metal element is 0.5% to 10% of the total molar amount of lithium in the lithium source and non-lithium alkali metal element in the non-lithium alkali metal source. The mixture is then subjected to sintering treatment.

[0096] In this embodiment, a mixed melt-sintering process is performed on raw materials including a nickel-cobalt-manganese precursor, a lithium source, and a non-lithium alkali metal source. This achieves an atomic-level reaction environment, allowing non-lithium alkali metal atoms to be doped into the lithium layer of a lithium-containing transition metal oxide, thus improving the structural stability of the lithium-containing transition metal oxide. Simultaneously, the atomic radius of the non-lithium alkali metal elements is larger than that of lithium. Compared to the crystal phase formed by lithium, oxygen, and manganese atoms, the crystal phase formed by non-lithium alkali metal atoms, oxygen, and manganese atoms more readily combines with high-valence manganese elements, such as tetravalent manganese. This effectively reduces the transformation of high-valence manganese to low-valence manganese, suppresses the Jan Taylor effect of trivalent manganese, and thus reduces manganese dissolution. Using this positive electrode active material in lithium-ion batteries can improve the battery's storage performance.

[0097] In some embodiments, the nickel-cobalt-manganese precursor contains 50% to 60% nickel, 0 to 10% cobalt, and 10% to 50% manganese in terms of the total molar amount of nickel, cobalt, and manganese.

[0098] It is understandable that in the preparation method of the positive electrode active material, the molar percentages of nickel, cobalt, and manganese can be selected from the content on lithium-ion batteries above, based on the total molar amount of nickel, cobalt, and manganese, and will not be repeated here.

[0099] In this application, the nickel-cobalt-manganese precursor can be purchased from commercial products or prepared using conventional methods in the art. For example, the nickel-cobalt-manganese precursor can be prepared by the following method: First, nickel acetate, cobalt acetate, and manganese acetate are added to deionized water in stoichiometric proportions and stirred until homogeneous to obtain a metal salt solution. A sodium carbonate solution is then poured into the metal salt solution, and the reaction continues for 9 hours, followed by standing and aging for 4 hours to allow for primary particle growth. The mixture is then washed three times with deionized water, dried in a blower dryer, and then vacuum dried at 100°C for 12 hours. The collected solid is the nickel-cobalt-manganese precursor.

[0100] In some embodiments, the sintering temperature is 700°C to 1000°C. For example, the sintering temperature can be 700°C, 720°C, 750°C, 780°C, 800°C, 820°C, 850°C, 880°C, 900°C, 920°C, 950°C, 980°C, 1000°C, or any value within the range of any two of the above values.

[0101] In some embodiments, the sintering time is 10h to 20h. For example, the sintering time can be 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, or any value within the range of any two of the above values.

[0102] It is understandable that sintering the mixture involves: pre-sintering the mixture and then heating it to the sintering temperature for sintering.

[0103] Optionally, the pre-sintering temperature is 450℃~550℃, and the pre-sintering time is 3h~8h. For example, the pre-sintering temperature can be 450℃, 460℃, 470℃, 480℃, 490℃, 500℃, 510℃, 520℃, 530℃, 540℃, 550℃, or any value within the range of any two of the above values. The pre-sintering time can be 3h, 4h, 5h, 6h, 7h, 8h, or any value within the range of any two of the above values.

[0104] In some embodiments, the mixture is pre-sintered by heating it from room temperature to the pre-sintering temperature at a rate of 3°C / min. Then, it is sintered by heating it to the sintering temperature at a rate of 3°C / min. After sintering, it is cooled to room temperature to obtain the positive electrode active material.

[0105] In some embodiments, the non-lithium alkali metal source includes two or more non-lithium alkali metal compounds with different melting points. A eutectic is formed using two or more non-lithium alkali metal compounds with different melting points. The melting point of the eutectic can be controlled by adjusting the proportions of the two or more non-lithium alkali metal compounds with different melting points, thus facilitating the control of the sintering temperature.

[0106] Optionally, the two or more non-lithium alkali metal compounds include the same non-lithium alkali metal element. Optionally, the non-lithium alkali metal compounds include non-lithium alkali metal carbonates and non-lithium alkali metal hydroxides. Further optionally, the mass ratio of the non-lithium alkali metal carbonate to the non-lithium alkali metal hydroxide is (1~10):(90~99). For example, the mass ratio of the non-lithium alkali metal carbonate to the non-lithium alkali metal hydroxide can be 1:99, 2:98, 3:97, 4:96, 5:95, 6:94, 7:93, 8:92, 9:91, 10:90, and any value within the range of any two of the above values. Further optionally, the non-lithium alkali metal carbonate includes one or more of sodium carbonate and potassium carbonate, and the non-lithium alkali metal hydroxide includes one or more of sodium hydroxide and potassium hydroxide.

[0107] In some implementations, the non-lithium alkali metal element in the non-lithium alkali metal source includes one or more of sodium and potassium.

[0108] In some embodiments, the ratio of the total molar amount of nickel, cobalt, and manganese to the molar amount of lithium is 1:(1.01~1.1). Optionally, the ratio of the total molar amount of nickel, cobalt, and manganese to the molar amount of lithium can be 1:1.01, 1:1.02, 1:1.03, 1:1.04, 1:1.05, 1:1.06, 1:1.07, 1:1.08, 1:1.09, 1:1.1, or any value within the range of any two of the above values.

[0109] In some embodiments, the raw materials further include sintering aids. Optionally, the sintering aids include one or more of sodium chloride and potassium chloride. Further, the molar ratio of sodium chloride to potassium chloride is 1:(0.8~1.2). For example, the molar ratio of sodium chloride to potassium chloride is 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, and any value within the range of any two of the above values.

[0110] In some embodiments, the ratio of the total molar amount of nickel, cobalt, and manganese to the molar amount of the sintering aid is 1:(0.1~0.3). Optionally, the ratio of the total molar amount of nickel, cobalt, and manganese to the molar amount of the sintering aid can be 1:0.1, 1:0.12, 1:0.15, 1:0.18, 1:0.2, 1:0.22, 1:0.25, 1:0.28, 1:0.3, or any value within the range of any two of the above values.

[0111] Another embodiment of this application provides a positive electrode sheet. The positive electrode sheet includes a positive current collector and a positive active layer located on at least one surface of the positive current collector. The positive active layer includes one or more of the above-described positive active material and positive active materials prepared by the above-described method for preparing positive active materials.

[0112] In some embodiments, the negative electrode includes a negative current collector and a negative electrode film located on at least one surface of the negative current collector, the negative electrode film including a negative electrode active layer. The negative electrode active layer includes a negative electrode active material.

[0113] In some embodiments, the negative electrode active material may be any negative electrode active material known in the art for use in batteries. Optionally, the negative electrode active material includes graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Graphite may include one or more of natural graphite and artificial graphite. Silicon-based materials include one or more of silicon-oxygen materials and silicon-carbon composite materials. 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.

[0114] Optionally, the negative electrode active material includes graphite.

[0115] Optionally, the negative electrode active material accounts for 92% to 99% of the mass of the negative electrode active layer. Optionally, the mass percentage of the negative electrode active material in the negative electrode active layer can be 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or any value within the range of any two of the above values.

[0116] 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). Optionally, the binder accounts for 0.5% to 5% of the mass percentage of the negative electrode active layer. Optionally, the mass percentage of the binder in the negative electrode active layer may be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or any value within the range of any two of the above values.

[0117] 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. Optionally, the conductive agent accounts for 0.5% to 5% of the mass percentage of the negative electrode active layer. Optionally, the mass percentage of the conductive agent in the negative electrode active layer may be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or any value within the range of any two of the above values.

[0118] In some embodiments, the negative electrode active layer may optionally include other additives, such as thickeners. Thickeners include sodium carboxymethyl cellulose (CMC-Na). Optionally, the thickener accounts for 0.5% to 5% of the mass of the negative electrode active layer. Optionally, the mass percentage of the thickener in the negative electrode active layer can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or any value within the range of any two of the above values.

[0119] 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).

[0120] 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 to form a negative electrode slurry. A non-limiting example of the solvent is deionized water. The negative electrode slurry is coated onto at least one surface of the negative electrode current collector, and after drying, cold pressing, or other processes, the negative electrode sheet is obtained. 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.

[0121] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0122] 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 bisfluorosulfonylimide (LiFSI), lithium bistrifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0123] In some embodiments, the solvent may include one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butenyl carbonate, 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.

[0124] 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.

[0125] 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).

[0126] It is understood that lithium-ion batteries may also include a separator. The separator is located between the positive electrode and the negative electrode. This application does not impose any particular restriction on the type of separator; any well-known porous separator with good chemical and mechanical stability can be selected.

[0127] 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.

[0128] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0129] 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.

[0130] 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.

[0131] This application does not impose any particular limitation on the shape of the lithium-ion battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 This is an example of a square-structured lithium-ion battery 1.

[0132] In some implementations, refer to Figure 2 The 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. Positive electrode sheets, negative electrode sheets, and a separator can be formed into an electrode assembly 12 via 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 lithium-ion battery 1 may contain one or more electrode assemblies 12, which can be selected by those skilled in the art according to actual needs.

[0133] In some implementations, the lithium-ion battery can be a single cell, a battery module, or a battery pack.

[0134] The battery module includes at least one lithium-ion battery. The battery module may contain one or more lithium-ion batteries, and those skilled in the art can select an appropriate number based on the application and capacity of the battery module.

[0135] In a battery module, multiple lithium-ion batteries can be arranged sequentially along the length of the module. Of course, they can also be arranged in any other manner. Furthermore, these multiple lithium-ion batteries can be secured using fasteners.

[0136] Optionally, the battery module may also include a housing with a receiving space in which multiple lithium-ion batteries are housed.

[0137] In some embodiments, the battery modules 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.

[0138] 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.

[0139] In addition, this application also provides an electrical device, which includes the lithium-ion battery provided in this application. The battery can be used as a power source for the electrical device or as an energy storage unit of 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.

[0140] As an electrical device, lithium-ion batteries can be selected based on its usage requirements.

[0141] 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 this electrical device, a battery pack or battery module can be used.

[0142] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can be powered by a battery.

[0143] 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.

[0144] 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.

[0145] Example 1

[0146] (1) Nickel-cobalt-manganese precursor

[0147] Nickel acetate, cobalt acetate, and manganese acetate were added to deionized water in a stoichiometric ratio of 55:6:39 and stirred until homogeneous to obtain a metal salt solution. A sodium carbonate solution was then added to the metal salt solution, and the reaction continued for 9 hours, followed by aging for 4 hours to allow for primary particle growth. The mixture was then washed three times with deionized water, dried in a blower dryer, and then vacuum-dried at 100°C for 12 hours. The collected solid was the nickel-cobalt-manganese precursor.

[0148] (2) Positive electrode active material

[0149] A nickel-cobalt-manganese precursor, a lithium source, a non-lithium alkali metal source, and sintering aids were mixed and ground into powder to obtain a mixture. The lithium source was lithium carbonate. The non-lithium alkali metal source consisted of sodium carbonate and sodium hydroxide in a mass ratio of 6:94. The sintering aids consisted of sodium chloride and potassium chloride in a molar ratio of 1:1. The molar ratio of total nickel, cobalt, and manganese in the nickel-cobalt-manganese precursor to that in the lithium source was 1:1.0165:0.0535:0.2.

[0150] The mixture was transferred to a crucible and placed in a programmed temperature-controlled muffle furnace. Pre-sintering was carried out at 500°C from room temperature for 5 hours at a heating rate of 3°C / min, followed by sintering at 850°C for 12 hours at a heating rate of 3°C / min. After cooling to room temperature, the positive electrode active material Li was collected. 0.95 Na 0.05 Ni 0.55 Co 0.06 Mn 0.39 O2.

[0151] (3) Positive electrode plate

[0152] Li, the positive electrode active material 0.95 Na 0.05 Ni 0.55 Co 0.06 Mn 0.39 O2, conductive agent carbon black, and binder polyvinylidene fluoride are mixed thoroughly in an appropriate amount of solvent N-methylpyrrolidone at a weight ratio of 92:3:5 to form a uniform positive electrode slurry. The positive electrode slurry is then uniformly coated onto the surface of the positive electrode current collector aluminum foil. After drying and cold pressing, the positive electrode sheet is obtained. Li... 0.95 Na 0.05 Ni 0.55 Co 0.06 Mn 0.39 O2 is a single crystal particle, and Dv50 is 4.5μm.

[0153] (4) Negative electrode plate

[0154] Artificial graphite (anode active material), styrene-butadiene rubber (binder), sodium carboxymethyl cellulose (thickener), and carbon black (conductive agent) were mixed thoroughly in an appropriate amount of deionized water at a weight ratio of 96.2:1.8:1.2:0.8 to form a uniform anode slurry. The anode slurry was then uniformly coated onto the surface of copper foil (anode current collector), and after drying and cold pressing, the anode sheet was obtained.

[0155] (5) Separating membrane

[0156] Porous polyethylene (PE) membrane is used as the separator.

[0157] (6) Electrolyte

[0158] In an environment with a water content of less than 10 ppm, ethylene carbonate (EC) and diethyl carbonate (DMC) are mixed at a mass ratio of 1:1 to obtain a solvent. Then, lithium hexafluorophosphate is mixed with the solvent to prepare an electrolyte with a lithium salt concentration of 1 mol / L.

[0159] (7) Lithium-ion batteries

[0160] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. The electrode assembly is then wound up. The electrode assembly is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained.

[0161] Examples 2 to 4

[0162] Compared with Example 1, Examples 2 to 4 differ in that the amount of raw materials used in the preparation method of the positive electrode active material is adjusted to obtain different positive electrode active materials. The positive electrode active materials are shown in Table 1.

[0163] Comparative Example 1

[0164] Compared with Example 1, the difference in Comparative Example 1 is that the preparation method of the positive electrode active material is as follows:

[0165] A nickel-cobalt-manganese precursor and a lithium source were mixed and ground into powder to obtain a mixture. The lithium source was lithium carbonate. The total molar amount of nickel, cobalt, and manganese in the nickel-cobalt-manganese precursor to the molar amount of lithium in the lithium source was 1:1.07.

[0166] The mixture was transferred to a crucible and placed in a muffle furnace with programmed temperature rise. Pre-sintering was carried out at 500°C from room temperature for 5 hours at a heating rate of 3°C / min, followed by sintering at 850°C for 12 hours at a heating rate of 3°C / min. After cooling to room temperature, the positive electrode active material LiNi was collected. 0.55 Co 0.06 Mn 0.39 O2.

[0167] Test case

[0168] (1) The storage performance of the lithium-ion batteries in the examples and comparative examples was tested. The test method was as follows: at 60°C, the lithium-ion batteries prepared in each example and comparative example were charged at a constant current rate of 0.33C to the charging cutoff voltage of 4.4V, then charged at a constant voltage rate until the current was ≤0.05C, left to stand for 5 minutes, and then discharged at a constant current rate of 0.33C to the discharge cutoff voltage of 2.8V, left to stand for 5 minutes, and the initial capacity C1 was measured. The lithium-ion batteries were transferred to a 60°C oven for high-temperature storage, and cross-capacity tests were performed every 3 months. The capacity test method was the same as the test method for the initial capacity C1, until the battery capacity decayed to 80%. The final number of days of battery storage was calculated. The results are shown in Table 1.

[0169] (2) After storage at 60℃ for 30 days, the batteries obtained in Example 1 and Comparative Example 1 were fully charged. The batteries were disassembled, and the mass percentages of manganese, nickel, and cobalt in the negative electrode were tested. The results are as follows: Figure 4 As shown. By Figure 4 It can be seen that in Example 1, the mass percentage of manganese in the negative electrode is 145 ppm, the mass percentage of nickel is 64 ppm, and the mass percentage of cobalt is 76 ppm. In Comparative Example 1, the mass percentage of manganese in the negative electrode is 217 ppm, the mass percentage of nickel is 131 ppm, and the mass percentage of cobalt is 226 ppm. This shows that the amount of manganese leached from the positive electrode in Example 1 is significantly lower than that in Comparative Example 1, indicating that the design of the positive electrode active material in Example 1 can effectively reduce the amount of manganese leached from the positive electrode active material. Combined with Table 1, it can be seen that the storage performance of Example 1 is higher than that of Comparative Example 1. That is, the design of the positive electrode active material in Example 1 can effectively improve the high-temperature storage performance of the battery.

[0170] (3) After storage at 60°C for 30 days, the batteries obtained in Example 1 and Comparative Example 1 were fully charged. The batteries were disassembled, and the lithium plating state on the negative electrode surface before and after storage was observed. The results are as follows: Figures 5-6 As shown. Among them, Figure 5 This refers to Example 1. Figure 5 In the text, (a) represents before storage and (b) represents after storage. Figure 6 This represents Comparative Example 1. Figure 6In the diagram, (a) represents the state before storage, and (b) represents the state after storage. Figure 5 and Figure 6 As can be seen, compared with before storage, no lithium plating occurred on the negative electrode of the battery in Example 1 after storage, while obvious lithium plating occurred on the battery in Comparative Example 1 after storage. This indicates that the design of the positive electrode active material in Example 1 can reduce the risk of lithium plating on the negative electrode and improve the high-temperature storage performance of the battery.

[0171] Table 1

[0172]

[0173] As can be seen from Table 1, introducing an appropriate proportion of Na element into the positive electrode active material can effectively improve the high-temperature storage performance of the battery.

[0174] 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.

[0175] 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, characterized in that, The battery includes a positive electrode, a negative electrode, and an electrolyte. The positive electrode includes a positive current collector and a positive active layer located on at least one surface of the positive current collector. The positive active material of the positive active layer includes a lithium-containing transition metal oxide, which includes lithium, non-lithium alkali metal elements, and transition metal elements, including nickel, cobalt, and manganese. In the fully discharged state of the lithium-ion battery, the molar percentage of the non-lithium alkali metal elements is 0.5% to 10% of the total molar amount of lithium and non-lithium alkali metal elements.

2. The lithium-ion battery according to claim 1, characterized in that, In the fully discharged state of the lithium-ion battery, the molar percentage of nickel is 50% to 60%, the molar percentage of cobalt is 0% to 10%, and the molar percentage of manganese is 10% to 50%, based on the total molar amount of nickel, cobalt, and manganese.

3. The lithium-ion battery according to any one of claims 1 to 2, characterized in that, The non-lithium alkali metal elements include one or more of sodium and potassium.

4. The lithium-ion battery according to any one of claims 1 to 3, characterized in that, The lithium-containing transition metal oxide includes the chemical formula Li 1-x M x (Ni a Co b Mn c ) 1-d Z d O 2-y A y The material has the following properties: 0.005≤x≤0.1, 0.5≤a≤0.6, 0≤b≤0.1, 0.1≤c≤0.5, a+b+c=1, 0≤d<1, 0≤y<2, M includes one or more of non-lithium alkali metal elements, Z includes one or more of Zr, Sr, B, Sn, Al, Mg, Fe, Cu, V, Ti, Zr, W, Sb, Dy and Te, and A includes one or more of N, P, S and halogen elements.

5. A method for preparing a positive electrode active material, characterized in that, Includes the following steps: The raw materials are mixed to obtain a mixture, which includes a nickel-cobalt-manganese precursor, a lithium source, and a non-lithium alkali metal source. The molar percentage of the non-lithium alkali metal element is 0.5% to 10% based on the total molar amount of lithium in the lithium source and non-lithium alkali metal in the non-lithium alkali metal source. The mixture is then subjected to sintering treatment.

6. The method for preparing the positive electrode active material according to claim 5, characterized in that, In the nickel-cobalt-manganese precursor, the molar percentage of nickel is 50% to 60%, the molar percentage of cobalt is 0% to 10%, and the molar percentage of manganese is 10% to 50%, based on the total molar amount of nickel, cobalt, and manganese.

7. The method for preparing the positive electrode active material according to any one of claims 5 to 6, characterized in that, The non-lithium alkali metal source includes two or more non-lithium alkali metal compounds with different melting points; Optionally, the non-lithium alkali metal compound satisfies one or more of the following characteristics: (1) Two or more of the aforementioned non-lithium alkali metal compounds comprise the same non-lithium alkali metal element; (2) The non-lithium alkali metal compounds include non-lithium alkali metal carbonates and non-lithium alkali metal hydroxides.

8. The method for preparing the positive electrode active material according to any one of claims 5 to 7, characterized in that, The raw materials used in the preparation also include sintering aids; Optionally, the sintering aid satisfies one or more of the following characteristics: (1) The sintering aid includes one or more of sodium chloride and potassium chloride; (2) The ratio of the total molar amount of nickel, cobalt and manganese in the nickel-cobalt-manganese precursor to the molar amount of the sintering aid is 1: (0.1~0.3).

9. The method for preparing the positive electrode active material according to any one of claims 5 to 8, characterized in that, The sintering process satisfies one or more of the following characteristics: (1) The sintering temperature is 700℃~1000℃; (2) The sintering time is 10h~20h.

10. An electrical device, characterized in that, The lithium-ion battery includes any one of claims 1 to 4.

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