High-nickel positive electrode active material, method of preparing the same, lithium ion battery including the same, battery module, battery pack, and electric device

Abstract

The present application provides a high-nickel ternary positive electrode active material, which comprises a core Li 1+a [Ni x Co y Mn z M b ]O2, and a first shell layer of fast ion conductor Li α Al X Si Y O4, an oxide of R elements of a second shell layer, and a transition layer Li p R q O w The high-nickel ternary positive electrode active material of the present application has a significantly reduced amount of surface miscellaneous lithium, and creatively converts the surface miscellaneous lithium into an effective component of fast ion conductor Li α Al X Si Y O4, Li p R q O w , which significantly improves the electrolyte decomposition gas caused by the surface miscellaneous lithium, so that the high-nickel ternary lithium ion battery has high energy density, good cycle performance and safety performance.

Description

Technical Field

[0001] The present application relates to the field of electrochemistry, and in particular to a high-nickel positive electrode active material, a preparation method thereof, a positive electrode sheet containing the same, a lithium-ion battery, a battery module, a battery pack, and an electrical device. Background Art

[0002] With the rapid development of the new energy field, lithium-ion batteries are widely used in various large-scale power devices, energy storage systems and various consumer products due to their excellent electrochemical properties, no memory effect and low environmental pollution. They are especially widely used in new energy vehicles such as pure electric vehicles and hybrid electric vehicles.

[0003] Compared to lithium iron phosphate materials, nickel-cobalt-manganese ternary cathode active materials are widely used due to their high gram capacity. However, existing technologies have not been able to achieve comprehensive improvements in the energy density, cycling performance, and safety performance of ternary lithium-ion batteries. In particular, the higher the nickel atomic content in the ternary cathode active material, the more difficult it is to achieve comprehensive improvements in the energy density, cycling performance, and safety performance of the lithium-ion battery containing it, which greatly limits the wider application of ternary lithium-ion batteries.

[0004] Therefore, it is very difficult to design a lithium-ion battery with high energy density, good cycle performance and good safety performance. Summary of the Invention

[0005] This application is made in view of the above-mentioned problems, and its purpose is to provide a high-nickel ternary positive electrode active material so that the ternary lithium-ion battery has high energy density, good cycle performance and good safety performance.

[0006] The first aspect of the present application provides a core-shell structured high nickel positive electrode active material, wherein:

[0007] The core includes Li 1+a [Ni x Co y Mn z M b ]O2, where 0.6≤x<1,0 <y<0.3,0<z<0.3,0<a<0.2,0<b<0.2,x+y+z+b=1,M为Mg、Ca、Sb、Ce、Ti、Zr、Sr、Al、Zn、Mo及B中的一种以上;

[0008] The shell includes a first shell layer covering the core, and a second shell layer covering the first shell layer; wherein,

[0009] The first shell is a fast ion conductor composed of four elements: lithium, aluminum, silicon and oxygen;

[0010] The second shell layer includes an oxide of an R element, and the R is selected from one or more of Al, B, Ti, P, Co, and La.

[0011] In any embodiment, the shell further includes a transition layer formed between the first shell and the second shell, wherein the transition layer includes one or more fast ion conductors Li formed by the first shell component and the second shell component. p R q O w , where 1≤p≤4, 1≤q≤5, 1≤w≤12, and p, q and w are all integers.

[0012] In any embodiment, the fast ion conductor of the first shell is Li α Al X Si Y O4, where 0 <X<2.4,0<Y<1.8,0.8≤α≤1.2,铝元素的化学计量系数X与硅元素的化学计量系数Y之比为0.8~1.2。

[0013] In any embodiment, the fast ion conductor Li in the transition layer described in the present application p R q O w Selected from LiAlO2, Li3BO3, Li4Ti5O 12 , Li3PO4, LiCoO2 or LiLaO.

[0014] In any embodiment, the nickel content of the high-nickel positive electrode active material in the present application is greater than 80%, that is, 0.8≤x<1, based on the total number of nickel, cobalt and manganese atoms.

[0015] In any embodiment, in the core of the high-nickel positive electrode active material of the present application, M may be one or more of Sb, Ti, Zr, Sr, Al, and B.

[0016] In any embodiment, in the high-nickel positive electrode active material of the present application, R may be one or more of Al, La, B, Co, and Ti.

[0017] In any embodiment, in the high-nickel positive electrode active material of the present application, the mass ratio of the lithium element in the core to the lithium element in the shell is 40 to 1300:1.

[0018] In any embodiment, when M is selected from one or more of Al, B or Ti, R is different from M, and based on the total mass of the high-nickel positive electrode active material, the mass content of the M element in the high-nickel positive electrode active material is 1000 to 5000 ppm, and can be optionally 3000 to 5000 ppm.

[0019] In any embodiment, when M is selected from one or more of Al, B or Ti, R is different from M, and the mass content of the R element is 100 to 20,000 ppm based on the total mass of the high-nickel positive electrode active material.

[0020] In any embodiment, in the high-nickel positive electrode active material, the mass ratio of the Si element to the R element is 0.1 to 7.0:1, and can be optionally 0.1 to 4.4:1.

[0021] In any embodiment, based on the total mass of the high-nickel positive electrode active material, the total mass content of silicon and aluminum in the first shell layer is 435 to 13150 ppm.

[0022] In any embodiment, the volume average particle size Dv50 of the high-nickel positive electrode active material of the present application is 1.5 to 20 μm, and the total thickness of the shell layer is 0.001 to 1 μm.

[0023] A second aspect of the present application provides a method for preparing a high-nickel positive electrode active material, comprising the following steps:

[0024] S1: providing a high nickel ternary precursor coated with silicon aluminum hydroxide to obtain a first intermediate;

[0025] S2: mixing the first intermediate with an M precursor and a lithium precursor, and sintering the mixture to obtain a second intermediate;

[0026] S3: mixing the second intermediate with the R precursor, and sintering to obtain the high-nickel positive electrode active material;

[0027] Wherein, the high nickel positive electrode active material is a core-shell structure,

[0028] The core includes Li 1+a [Ni x Co y Mn z M b ]O2, where 0.6≤x<1,0 <y<0.3,0<z<0.3,0<a<0.2,0<b<0.2,x+y+z+b=1,M为Mg、Ca、Sb、Ce、Ti、Zr、Sr、Al、Zn、Mo及B中的一种以上;

[0029] The shell includes a first shell layer covering the core, and a second shell layer covering the first shell layer; wherein,

[0030] The first shell is a fast ion conductor composed of four elements: lithium, aluminum, silicon and oxygen;

[0031] The second shell layer includes an oxide of element R, and the R is selected from one or more of Al, B, Ti, P, Co, and La.

[0032] The preparation method of the present application has a wide range of raw material sources, low cost, simple process, and is more conducive to large-scale industrialization.

[0033] In any embodiment, in step S1, the preparation process of the high nickel ternary precursor coated with silicon aluminum hydroxide is:

[0034] (a) completely dissolving an aluminum precursor and a silicon precursor in an alkaline solution, and then adding a high nickel ternary precursor to obtain a solid-liquid mixture;

[0035] (b) lowering the pH of the solid-liquid mixture to induce a hydrolysis-in-situ precipitation reaction between the aluminum precursor and the silicon precursor to obtain a high-nickel ternary precursor coated with silicon-aluminum hydroxide.

[0036] In any embodiment, in the step (a), the aluminum precursor and the silicon precursor are added to the alkaline solution at a molar ratio of aluminum:silicon = 0.8 to 1.2:1.

[0037] In any embodiment, in the step (a), based on the total mass of the solid-liquid mixture, the mass proportion of the high-nickel ternary precursor is 16% to 50%.

[0038] In any embodiment, in step (a), the pH of the alkaline solution is 11 to 13;

[0039] In the step (b), a weakly acidic gas is introduced into the solid-liquid mixture at a flow rate of 1 to 20 mL / min to reduce the pH of the solid-liquid mixture to 8 to 10.

[0040] In any embodiment, in the step (b), the reaction temperature of the hydrolysis-in-situ precipitation reaction is 20-40° C., the reaction time is 0.1-2 h, and the stirring linear speed is 1-6 m / s.

[0041] In any embodiment, in step S2, assuming that the total molar amount of nickel atoms, cobalt atoms, and manganese atoms in the first intermediate is Me2, then:

[0042] The lithium precursor is added in an amount of 0.9 to 1.1 Me2 of lithium atoms, and the M precursor is added in an amount of (8×10 -4 ~180×10 -4 )Me2 is added in an amount mixed with the first intermediate.

[0043] In any embodiment, in step S2, the sintering temperature is 700-950°C, the sintering time is 10-20 hours, and the sintering atmosphere is air or oxygen.

[0044] In any embodiment, in step S3, assuming that the total molar amount of nickel atoms, cobalt atoms, and manganese atoms in the second intermediate is Me3, then:

[0045] The R precursor is based on the R atom (16×10 -4 ~330×10 -4 )Me3 is added in an amount mixed with the second intermediate.

[0046] In any embodiment, in step S3, the sintering temperature is 200-700° C., the sintering time is 5-15 hours, and the sintering atmosphere is air or oxygen.

[0047] The third aspect of the present application provides a positive electrode plate, comprising the high-nickel positive electrode active material described in the first aspect of the present application or the high-nickel positive electrode active material prepared by the preparation method of the second aspect of the present application.

[0048] The fourth aspect of the present application provides a lithium-ion battery, comprising the high-nickel positive electrode active material described in the first aspect of the present application, or the high-nickel positive electrode active material prepared by the preparation method of the second aspect of the present application, or the positive electrode sheet of the third aspect of the present application.

[0049] In a fifth aspect, the present application provides a battery module, comprising the lithium-ion battery of the fourth aspect. The battery module can be prepared using methods known in the art for preparing battery modules.

[0050] In a sixth aspect, the present application provides a battery pack comprising at least one of the lithium-ion battery of the fourth aspect or the battery module of the fifth aspect. The battery pack can be prepared using methods known in the art for preparing battery packs.

[0051] In a seventh aspect, the present application provides an electrical device comprising one or more of the lithium-ion battery of the fourth aspect, the battery module of the fifth aspect, or the battery pack of the sixth aspect, wherein the lithium-ion battery, the battery module, or the battery pack serves as a power source or an energy storage unit for the electrical device. The electrical device can be prepared using methods known in the art for preparing electrical devices.

[0052] [Beneficial Effects]

[0053] The present invention is to coat the first shell of the fast ion conductor, especially Li α Al X Si Y O4, fast ion conductor Li in the transition layerp R q O w The high nickel ternary positive electrode active material of the present invention has a significantly reduced amount of surface impurities of lithium and creatively converts the surface impurities of lithium into a fast ion conductor Li that accelerates the insertion / extraction of lithium ions in the core. α Al X Si Y O4、Li p R q O w The effective components in the electrolyte significantly improve the decomposition and gas production caused by surface impurities of lithium, so that the high nickel ternary lithium-ion battery has high energy density while also having good cycle performance and safety performance.

[0054] The battery module, battery pack and electrical device of the present application include the lithium-ion battery provided by the present application, and thus have at least the same advantages as the lithium-ion battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 Schematic diagram of the structure of a high-nickel positive electrode active material according to one embodiment of the present application.

[0056] Figure 2 This is a volume average particle size distribution diagram of one embodiment of the present application.

[0057] Figure 3 Schematic diagram of a lithium-ion battery according to one embodiment of the present application.

[0058] Figure 4 yes Figure 3 An exploded view of a lithium-ion battery according to an embodiment of the present application is shown.

[0059] Figure 5 Schematic diagram of a battery module according to one embodiment of the present application.

[0060] Figure 6 Schematic diagram of a battery pack according to one embodiment of the present application.

[0061] Figure 7 yes Figure 6 An exploded view of a battery pack according to an embodiment of the present application is shown.

[0062] Figure 8 It is a schematic diagram of an electrical device according to one embodiment of the present application.

[0063] Description of reference numerals:

[0064] 1 battery pack

[0065] 2 upper box

[0066] 3 lower cabinets

[0067] 4 battery modules

[0068] 5. Lithium-ion battery

[0069] 51 shell

[0070] 52 electrode assembly

[0071] 53 top cover assembly

[0072] 6 cores

[0073] 7 First Shell

[0074] 8 transition layers

[0075] 9 Second Shell DETAILED DESCRIPTION

[0076] Hereinafter, the high nickel positive electrode active material, its preparation method, lithium ion battery, battery module, battery pack and electric device specifically disclosed in this application will be described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0077] " scope " disclosed in the application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of specific range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a scope with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 listed, and if the maximum range value 3,4 and 5 are listed, then the following scope can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0078] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0079] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0080] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0081] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0082] The terms "above" and "below" used in this application include the number, for example, "one or more" means one or more, and "one or more of A and B" means "A", "B" or "A and B".

[0083] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0084] It should be noted that the term "shell" refers to the portion coated on the "core" of the high-nickel positive electrode active material, which may but does not necessarily completely coat the "core". The use of "shell" or "shell layer" or "first shell layer" or "transition layer" or "second shell layer" is for ease of description and is not intended to limit this application. Similarly, "the second shell layer coats the first shell layer" means that the second shell layer completely coats or partially coats the first shell layer.

[0085] The term "high nickel content" means that the number of nickel atoms in the corresponding positive electrode active material accounts for more than 60% of the total number of nickel, cobalt and manganese atoms. Similarly, the term "nickel content" used in this article refers to the percentage of nickel atoms in the positive electrode active material to the total number of nickel, cobalt and manganese atoms. The term "high nickel ternary precursor" used in this application refers to a nickel, cobalt and manganese ternary material in the form of hydroxide, in which the number of nickel atoms accounts for more than 60% based on the total number of nickel, cobalt and manganese atoms.

[0086] The term "fast ionic conductor" is also called a superionic conductor, and sometimes also called a solid electrolyte. Its most basic feature that distinguishes it from a general ionic conductor is that it has an ionic conductivity (0.01Ω·cm) comparable to that of a liquid electrolyte within a certain temperature range and a low ionic conductivity activation energy (≤0.40eV). For example, as an example, the fast ionic conductors that may exist in the first shell and the second shell of the present invention include LiAl 0.971 Si 1.022 O4, Li3BO3, etc.

[0087] The term "precursor" of an element as used herein may refer to a raw material, or may refer to a compound containing the element obtained by subjecting the initial material to a certain treatment before obtaining the target product, and which may undergo further reaction under the conditions of the preparation method of the present application to obtain the target product. For example, a "precursor" may be an oxide, hydroxide or water-soluble salt of the corresponding element. As an example, for example, when M represents elemental aluminum, its precursor may be a metaaluminate or aluminum hydroxide; for another example, the precursor of the lithium element may be lithium hydroxide; for another example, a high-nickel ternary precursor refers to a composite hydroxide formed by five elements: nickel, cobalt, manganese, oxygen and hydrogen.

[0088] The inventors of this application discovered in their actual work that increasing the lithium content in the layered structure of nickel-cobalt-manganese ternary cathode active materials can significantly increase the material's charge-discharge capacity per gram, significantly improving the energy density of lithium-ion batteries. However, when the nickel atomic content in the nickel-cobalt-manganese ternary cathode active material exceeds 60% (based on the total number of nickel, cobalt, and manganese atoms), the corresponding lithium-ion battery experiences a series of phenomena that seriously threaten the battery's electrochemical performance and safety, including a severe decline in cycle performance and a sharp increase in internal gas production.

[0089] After extensive research by the inventors, it was found that the reasons why the above-mentioned high-nickel ternary positive electrode active materials have the above-mentioned adverse effects are as follows: First, with the repeated insertion / extraction of lithium ions, compared with the low-nickel ternary positive electrode active materials, the microscopic layered structure of the high-nickel ternary positive electrode active materials is more prone to lattice distortion and layered structure collapse, thereby losing the ability to insert and extract lithium ions, and ultimately causing the energy density and cycle performance of the lithium-ion battery to decline seriously. Second, for the high-nickel ternary positive electrode active materials, the amount of impurities (for example, lithium oxide, lithium carbonate) on their surface is greater, causing serious side reactions at the interface where they contact the electrolyte, thereby seriously increasing the gas production inside the battery, resulting in a significant decline in the battery's cycle performance and safety performance.

[0090] Therefore, although high-nickel ternary positive electrode active materials can increase battery energy density by increasing nickel content, they will also significantly reduce the battery's cycle performance and safety performance.

[0091] In response to the above research topic, the inventors of this application, starting from comprehensively improving the comprehensive performance of ternary lithium-ion batteries, have developed a high-nickel ternary positive electrode active material by modifying the high-nickel ternary positive electrode active material, which can comprehensively improve the energy density, cycle performance and safety performance of lithium-ion batteries.

[0092] [High nickel ternary positive electrode active material]

[0093] The present application provides a high nickel positive electrode active material, which is a core-shell structure, wherein:

[0094] The core includes Li 1+a [Ni x Co y Mn z M b ]O2, where 0.6≤x<1,0 <y<0.3,0<z<0.3,0<a<0.2,0<b<0.2,x+y+z+b=1,M为Mg、Ca、Sb、Ce、Ti、Zr、Sr、Al、Zn、Mo及B中的一种以上;

[0095] The shell includes a first shell layer covering the core, and a second shell layer covering the first shell layer; wherein,

[0096] The first shell is a fast ion conductor composed of four elements: lithium, aluminum, silicon and oxygen;

[0097] The second shell layer includes an oxide of element R, and the R is selected from one or more of Al, B, Ti, P, Co, and La.

[0098] In some embodiments, optionally, in the core of the positive electrode active material of the present application, the ratio of z to y is 2:1 to 1:2, optionally 3:2 to 2:3.

[0099] In some embodiments, optionally, in the core of the positive electrode active material of the present application, the ratio of y to z and y+z to x is 1:10 to 1:7, optionally 1:9 to 1:8.

[0100] In some embodiments, optionally, the fast ion conductor in the first shell is Li α Al X Si Y O4, where 0 <X<2.4,0<Y<1.8,0.8≤α≤1.2,铝元素的化学计量系数X与硅元素的化学计量系数Y之比为0.8~1.2。

[0101] The high nickel cathode active material of the present application has a core-shell structure with two shell layers covering the core, wherein the core comprises Li 1+a [Ni x Co y Mn z M b ]O2. The continuous two-layer shell coating can prevent the core material from embedding / escaping the main body of lithium ions, namely Li 1+a [Ni x Co y Mn z M b ]O2, the crystal structure collapses after several charge and discharge cycles, and on the other hand, it can also isolate the direct contact between the core material and the electrolyte, thereby reducing the corrosion of the surface of the positive electrode active material by the corrosive substances in the electrolyte, reducing the side reactions of the electrolyte on the positive electrode surface, and preventing gas production inside the battery. In addition, the continuous two-shell coating can also prevent the dissolution of the transition metal elements of the core material during the battery cycle and storage process, and prevent the dissolved transition metal elements from depositing on the negative electrode surface. Last but not least, the continuous two-shell coating can significantly improve the amount of impurities on the surface of the high-nickel positive electrode active material and significantly increase the relative proportion of active lithium in the high-nickel positive electrode active material. In short, the continuous two-shell coating can comprehensively improve the energy density, cycle performance and safety performance of high-nickel ternary lithium-ion batteries through the above four effects.

[0102] Furthermore, the core of the high nickel positive electrode active material of the present application includes Li 1+a [Ni x Co y Mn z M b ]O2. M element is doped into the core material and can form Li 1+a [Ni x Co y Mn z M b]O2, improve the structural stability of the core material, prevent the structural collapse of the core material during multiple charge and discharge cycles, and thus improve the cycle performance of the battery.

[0103] It is worth mentioning that the high-nickel positive electrode active material of the present application is particularly suitable for high-nickel ternary lithium-ion batteries, and is particularly suitable for nickel contents above 60%, and particularly suitable for nickel contents above 80%. Optionally, the nickel content can be 60%, 80%, or 90%.

[0104] It is worth mentioning that when M is one or more of Sb, Ti, Zr, Sr, Al, and B, the improvement in the charge and discharge capacity, cycle capacity retention rate, and gas production of the lithium-ion battery is more significant.

[0105] Furthermore, the first shell is a fast ion conductor layer composed of four elements: lithium, aluminum, silicon, and oxygen. For example, the fast ion conductor is Li α Al X Si Y O4. Fast ion conductor Li α Al X Si Y The presence of O4: On the one hand, it can creatively transform the lithium components on the surface of the core material into Li α Al X Si Y The structural lithium in O4 can effectively reduce the amount of impurity lithium in high nickel ternary positive electrode active materials, thereby improving the interface side reaction between the material and the electrolyte and improving the cycle performance of the battery; on the other hand, Li α Al X Si Y O4 can significantly increase the insertion and extraction rate of lithium ions, thereby improving the charge and discharge capacity and cycle performance of the battery.

[0106] It is worth mentioning that for the fast ion conductor Li α Al X Si Y The molar ratio of O4, Al atoms to Si atoms, that is, the ratio of X to Y is 0.8 to 1.2. When the ratio of X to Y is within the above range, it is conducive to the formation of a good fast ion conductor on the surface of the positive electrode material, which in turn helps to reduce the surface impurity lithium content, reduce the interface side reactions of the material, and at the same time improve the lithium ion transmission rate, thereby improving the cycle performance and safety performance of the battery. It is worth noting that when the Al or Si content is too much, that is, when the ratio of X to Y deviates from the above range, low-activity Al or Si substances may form on the surface of the positive electrode material, which in turn affects the transmission of lithium ions.

[0107] It is worth mentioning that the Li α Al X Si YThe α in O4 is in the range of 0.8 to 1.2, and can be selected as 1 or any natural number in the range of 0.8 to 1.2. When the value of α is lower than the above range, the relative content of lithium ions in the fast ion conductor in the first shell is relatively small, and the rate at which the formed fast ion conductor transports lithium ions may be poor, affecting battery performance. When the value of α is higher than the above range, excessive lithium ions may cause an increase in the amount of impurity lithium on the surface of the positive electrode material, resulting in an increase in interfacial side reactions with the electrolyte, affecting the safety performance of the battery.

[0108] Furthermore, the second shell layer includes an oxide of element R, wherein R is one or more of Al, B, Ti, P, Co, and La. The second shell layer can prevent the fast ion conductor Li α Al X Si Y O4 can prevent component loss and structural damage caused by electrolyte immersion, and can isolate the contact between the core material and the electrolyte, which plays an important role in improving the stability of high-nickel positive electrode active materials, and is beneficial to improving battery energy density, cycle performance and safety performance.

[0109] It should be noted that when R is Co, if the sintering temperature during preparation of the second shell layer is relatively low, for example, 200°C, then Co hydroxide Co(OH)2 may also be present, which is also encompassed within the scope of the present invention. Therefore, the term "oxide of element R" herein should be specifically understood to include, in addition to the oxide of element R, Co hydroxide Co(OH)2 when R is Co.

[0110] It is worth mentioning that when R is one or more of Al, La, B, Co, and Ti, the improvement in the charge and discharge capacity, cycle capacity retention rate, and gas production of the lithium-ion battery is more significant.

[0111] In some embodiments, the shell further includes a transition layer formed between the first shell and the second shell, wherein the transition layer includes one or more fast ion conductors Li formed by the first shell component and the second shell component. p R q O w , where 1≤p≤4, 1≤q≤5, 1≤w≤12, and p, q and w are all integers.

[0112] In the shell layer of the high nickel positive electrode active material of the present application, the transition layer is a transition region formed by the first shell layer and the second shell layer, and the Li p R q O wThe components can further increase the rate of lithium ion insertion and extraction in the high-nickel cathode active material. Therefore, in the high-nickel cathode active material of the present application, the synergistic effect of the two layers of fast ion conductors (i.e., the first shell and the second shell) greatly increases the specific capacity of the high-nickel cathode active material.

[0113] It is worth mentioning that in the high-nickel positive electrode active material of the present application, a transition region similar to the transition layer between the first shell and the second shell may be included between the core and the shell, which may be a continuous layered structure or a discontinuous layered structure, and may have a uniform or non-uniform thickness.

[0114] It is worth mentioning that the transition layer formed between the first shell and the second shell is a continuous layered structure. p R q O w The components make the connection between the two shells tighter, thereby preventing the second shell from falling off during the use of the battery, and at the same time it is more conducive to fully improving the gram capacity of the high nickel positive electrode active material.

[0115] In some embodiments, optionally, the fast ion conductor Li in the transition layer p R q O w Selected from LiAlO2, Li3BO3, Li4Ti5O 12 , Li3PO4, LiCoO2 or LiLaO.

[0116] In some embodiments, optionally, the x is 0.8≤x<1, the M is one or more of Sb, Ti, Zr, Sr, Al, and B, and the R is one or more of Al, La, B, Co, and Ti.

[0117] In some embodiments, optionally, in the high-nickel positive electrode active material of the present application, the mass ratio of the lithium element in the core layer to the lithium element in the shell layer is 40 to 1300:1.

[0118] The ratio of the mass of lithium element in the core to the mass of lithium element in the shell of the high nickel positive electrode active material of the present application is within the above range: on the one hand, it can ensure that there is enough active lithium in the core to contribute to the gram capacity of the high nickel positive electrode active material, thereby improving the battery energy density and cycle performance; on the other hand, it can ensure that there is an appropriate amount of lithium element as an effective component in the first shell, the transition layer, and the second shell to form a fast ion conductor Li α Al X Si Y O4、Li p R q O wFurthermore, a suitable ratio of the core lithium mass to the shell lithium mass can effectively prevent the formation of lithium species on the surface of high-nickel cathode active materials, thereby reducing side reactions within the battery. In summary, through the above three effects, a suitable ratio of the core lithium mass to the shell lithium mass can help improve battery energy density, cycle performance, and safety performance (mainly reflected in improved gas production within the battery).

[0119] In some embodiments, optionally, when M is selected from one or more of Al, B or Ti, R is different from M, and based on the total mass of the high-nickel positive electrode active material, the mass content of the M element in the high-nickel positive electrode active material is 1000 to 5000 ppm, optionally 3000 to 5000 ppm.

[0120] Compared with the ternary cathode active materials with low nickel content, the core material Li 1+a [Ni x Co y Mn z M b ]The doping of M element in O2 can significantly improve the core material Li 1+a [Ni x Co y Mn z M b The structural collapse and destruction of O2 due to repeated insertion and extraction of lithium ions builds a more stable channel for lithium ion transmission, which is beneficial to increasing the gram capacity of high-nickel positive electrode active materials, thereby improving the energy density and cycle performance of lithium-ion batteries.

[0121] In some embodiments, optionally, when M is selected from one or more of Al, B or Ti, R is different from M, and the mass content of the R element is 100 to 20,000 ppm based on the total mass of the high-nickel positive electrode active material.

[0122] Limiting the mass content of the R element to a reasonable range: On the one hand, it can form an R oxide with a more stable physicochemical structure, effectively blocking electrolyte corrosion on the core material and the first shell, reducing side reactions within the battery; on the other hand, the presence of the second shell, including the R element oxide, can also effectively prevent the cracking and fragmentation of the high-nickel positive electrode active material, thereby preventing thermal runaway within the battery caused by small particles generated by the core material fragmentation. In summary, through the above effects, limiting the mass content of the R element to a reasonable range can improve the energy density, cycle performance, and safety performance of the battery.

[0123] Furthermore, when the mass content of the R element is 500 to 15000 ppm, the improvement in the charge and discharge capacity, cycle capacity retention rate and gas production of the lithium-ion battery is more significant.

[0124] In some embodiments, optionally, in the high-nickel positive electrode active material, the ratio of the mass of the Si element to the mass of the R element is 0.1 to 7.0:1, and optionally 0.1 to 4.4:1.

[0125] In the high-nickel positive electrode active material, the appropriate mass ratio of Si element to R element means that the mass ratio of the first shell to the second shell is within a suitable range. If the R element is too little and the Si element is too much, that is, the second shell coating is incomplete and the first shell coating is too thick, it may not play a role in reducing the side reaction between the electrolyte and the surface of the high-nickel material. At the same time, it may also reduce the gram capacity of the material itself because the first shell (Si element does not contribute to capacity) is too thick, resulting in a low battery discharge capacity. On the contrary, if the R element is too little and the Si element is too much, that is, the first shell coating is incomplete and the second shell coating is too thick, it may make the high-nickel positive electrode active material unable to build a complete network structure for fast lithium ion conduction, thereby reducing the lithium ion deintercalation rate, reducing the gram capacity of the high-nickel positive electrode active material, reducing the battery discharge capacity, affecting the battery cycle performance, and at the same time, it may also reduce the gram capacity of the material itself because the second shell (R element does not contribute to capacity) is too thick, resulting in a low battery discharge capacity.

[0126] In some embodiments, optionally, based on the total mass of the high-nickel positive electrode active material, the total mass content of silicon and aluminum in the first shell layer is 435 to 13150 ppm.

[0127] The total mass content of silicon and aluminum in the first shell is equal to the total mass content of Li in the first shell. α Al X Si Y A layer of fast ion conductor Li is coated on the surface of the high nickel active material. α Al X Si Y O4 can effectively improve the transmission rate of lithium ions, reduce the side reactions between the interface and the electrolyte, and improve the capacity and long-term performance; but the coating amount should not be too little or too much. Too little may not work, and too much may reduce the material's specific capacity and increase the lithium ion transmission resistance.

[0128] In some embodiments, optionally, the volume average particle size Dv50 of the high-nickel positive electrode active material is 1.5 to 20 μm, and the shell thickness is 0.001 to 1 μm. In the high-nickel positive electrode active material of the present application, if the volume average particle size Dv50 of the particles is too large, it will lead to an increase in the resistance to lithium ion deintercalation and insertion, resulting in an increase in the internal resistance of the battery; at the same time, the volume average particle size Dv50 should not be too small, because too small a particle size will increase the complexity of the process and increase production costs on the one hand, and on the other hand, it will also increase the contact area with the electrolyte. Once the shell function is lost, it may cause the battery performance to deteriorate rapidly. Similarly, when the shell thickness is too large, it will increase the internal resistance of the battery and reduce the gram capacity of the material, but when the shell thickness is too small, it may be difficult to effectively play the beneficial functions of the shell.

[0129] The high-nickel positive electrode active material of the present application can be a polycrystalline ternary material or a single-crystalline ternary material; the polycrystalline ternary material has a polycrystalline structure, and the single-crystalline ternary material has a single-crystalline structure or a quasi-single-crystalline structure. When the high-nickel positive electrode active material has a polycrystalline structure, the gram capacity contributed by the high-nickel positive electrode active material is higher, and when the high-nickel ternary positive electrode active material has a single-crystalline structure or a quasi-single-crystalline structure, the corresponding lithium-ion battery has better cycle performance.

[0130] In some embodiments, the single crystal structure or quasi-single crystal structure of the high nickel positive electrode active material described in this application can be synthesized by controlling the particle size of the high nickel ternary precursor between 1 and 5 μm and by increasing the calcination temperature of the key preparation step.

[0131] For example, in the method described in this application, by increasing the sintering temperature of step S2 from 700°C to 950°C and adjusting the precursor Dv50 particle size in step S1 from 9μm to 3μm, a high-nickel positive electrode active material with a good single crystal or single crystal-like structure can be synthesized.

[0132] Those skilled in the art can select the high-nickel ternary positive electrode active material with a polycrystalline structure of the present application, or the high-nickel ternary positive electrode active material with a single crystal or quasi-single crystal structure according to different application scenarios of lithium-ion batteries.

[0133] The present application provides a method for preparing a high-nickel positive electrode active material, comprising the following steps:

[0134] S1: providing a high nickel ternary precursor coated with silicon aluminum hydroxide to obtain a first intermediate;

[0135] S2: mixing the first intermediate with an M precursor and a lithium precursor, and sintering the mixture to obtain a second intermediate;

[0136] S3: mixing the second intermediate with the R precursor, and sintering to obtain the high-nickel positive electrode active material;

[0137] Wherein, the high nickel positive electrode active material is a core-shell structure,

[0138] The core includes Li 1+a [Ni x Co y Mn z M b ]O2, where 0.6≤x<1,0 <y<0.3,0<z<0.3,0<a<0.2,0<b<0.2,x+y+z+b=1,M为Mg、Ca、Sb、Ce、Ti、Zr、Sr、Al、Zn、Mo及B中的一种以上;

[0139] The shell includes a first shell layer covering the core, and a second shell layer covering the first shell layer; wherein,

[0140] The first shell is a fast ion conductor composed of four elements: lithium, aluminum, silicon and oxygen;

[0141] The second shell layer includes an oxide of element R, and the R is selected from one or more of Al, B, Ti, P, Co, and La.

[0142] The preparation method of the present application has a wide range of raw materials, low cost, simple process, and is more conducive to large-scale industrialization.

[0143] In some embodiments, optionally, in step S1, the preparation process of the high nickel ternary precursor coated with silicon aluminum hydroxide is:

[0144] (a) completely dissolving an aluminum precursor and a silicon precursor in an alkaline solution, and then adding a high nickel ternary precursor to obtain a solid-liquid mixture;

[0145] (b) lowering the pH of the solid-liquid mixture to induce a hydrolysis-in-situ precipitation reaction between the aluminum precursor and the silicon precursor to obtain a high-nickel ternary precursor coated with silicon-aluminum hydroxide.

[0146] In step (a), the above-mentioned aluminum precursor can be one or more of sodium aluminate (NaAlO2), potassium aluminate (KAlO2), and lithium aluminate (LiAlO2), and the silicon precursor can be one or more of sodium silicate (Na2O·nSiO2), potassium silicate (K2O·nSiO2), and lithium silicate (Li2O·nSiO2).

[0147] In step (a), the solid-liquid mixture maintains a relatively high pH, ​​ensuring sufficient dissolution of the aluminum and silicon precursors without causing excessive hydrolysis of the aluminum and silicon precursors. The addition of the high-nickel ternary precursor provides a precipitation surface for the subsequent hydrolysis-in-situ precipitation reaction of the aluminum and silicon precursors.

[0148] Further, in step (b), reducing the pH of the solid-liquid mixture can initiate a hydrolysis-in-situ precipitation reaction of the aluminum precursor and the silicon precursor, so that the silicon-aluminum hydroxide generated by the hydrolysis is co-precipitated onto the surface of the high-nickel ternary precursor, to obtain a first intermediate.

[0149] Further, in step (a), the aluminum precursor and the silicon precursor are added to the alkaline solution in a molar ratio of aluminum:silicon = 0.8-1.2:1.

[0150] Further, in step (a), the mass fraction of the high-nickel ternary precursor in the total mass of the solid-liquid mixture is 16%-50%.

[0151] Further, in step (a), the pH of the alkaline solution is 11-13, for preventing the hydrolysis of the aluminum precursor and the silicon precursor.

[0152] Further, a weakly acidic gas is introduced into the solid-liquid mixture at a flow rate of 1-20 mL / min, to reduce the pH of the solid-liquid mixture to 8-10.

[0153] In some embodiments, optionally, the weakly acidic gas is one or more of CO2 and SO2.

[0154] Further, in step (b), the reaction temperature of the hydrolysis-in-situ precipitation reaction is 20-40°C, the reaction time is 0.1-2 h, and the stirring line speed is 1-6 m / s.

[0155] In some embodiments, optionally, in step S2, let the total molar amount of nickel atoms, cobalt atoms, and manganese atoms in the first intermediate be Me2, then:

[0156] The lithium precursor is added in an amount of 0.9-1.1 Me2 of lithium atoms, and the M precursor is added in an amount of (8x10 -4 -180x10 -4 Me2 of M atoms, to the first intermediate.

[0157] Further, in step S2, the sintering temperature is 700-950°C, the sintering time is 10-20 h, and the sintering atmosphere is air or oxygen.

[0158] In some embodiments, optionally, in step S3, let the total molar amount of nickel atoms, cobalt atoms, and manganese atoms in the second intermediate be Me3, then:

[0159] The R precursor is added in an amount of (16x10 -4 -330x10 -4The Me3 is added in an amount to mix with the second intermediate.

[0160] In some embodiments, the R precursor can be one or more of an Al-containing oxide, hydroxide, or inorganic acid salt, the R precursor can be one or more of a B-containing oxide, hydroxide, or inorganic acid salt, the R precursor can be one or more of a Ti-containing oxide, hydroxide, or inorganic acid salt, the R precursor can be one or more of a P-containing oxide, hydroxide, or inorganic acid salt, the R precursor can be one or more of a Co-containing oxide, hydroxide, or inorganic acid salt, and the R precursor can be one or more of a La-containing oxide, hydroxide, or inorganic acid salt.

[0161] In some embodiments, the sintering temperature in step S3 is 200-700°C, the sintering time is 5-15h, and the sintering atmosphere is air or oxygen. It is worth noting here that the sintering temperature in step S3 is at least 500°C lower than the sintering temperature in step S2, so that the M element in step S2 enters the core structure, while the R element in step S3 does not substantially enter the core structure.

[0162] [Positive electrode sheet]

[0163] The present application provides a positive electrode sheet, which comprises the high-nickel positive electrode active material of the present application.

[0164] The positive electrode sheet comprises a positive electrode current collector and a positive electrode material disposed on at least one surface of the positive electrode current collector. As an example, the positive electrode current collector has two surfaces opposite in the thickness direction thereof, and the positive electrode material is disposed on either one or both of the two opposite surfaces of the positive electrode current collector.

[0165] In the lithium ion battery of the present application, the positive electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, an aluminum foil can be used. The composite current collector can comprise a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer material base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), 1,3-propanesultone, polyethylene (PE), etc.), but the present application is not limited to these materials.

[0166] The positive electrode material may also optionally include a conductive agent. However, the type of conductive agent is not particularly limited, and those skilled in the art may select one based on actual needs. For example, the conductive agent used in the positive electrode material may be selected from one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0167] In the present application, the positive electrode sheet can be prepared according to methods known in the art. As an example, the positive electrode active material, conductive agent, and binder of the present application can be dispersed in a solvent (e.g., N-methylpyrrolidone (NMP)) to form a uniform positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing, and other processes, the positive electrode sheet is obtained.

[0168] [Negative electrode]

[0169] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0170] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0171] In the lithium-ion battery of the present application, 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 base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.), but the present application is not limited to these materials.

[0172] In the negative electrode sheet of the present application, the negative electrode film layer generally comprises a negative electrode active material and, optionally, a binder, an optional conductive agent, and other optional additives, and is generally formed by coating and drying a negative electrode slurry. The negative electrode slurry is generally formed by dispersing the negative electrode active material, the optional conductive agent, and the binder in a solvent and stirring the mixture uniformly. The solvent may be N-methylpyrrolidone (NMP) or deionized water.

[0173] As an example, the conductive agent may be selected from one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0174] In the negative electrode tab of the present application, the negative electrode film layer can optionally include other commonly used negative electrode active materials in addition to the negative electrode active material. For example, as the other commonly used negative electrode active material, artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material, and lithium titanate can be listed. The silicon-based material can be selected from one or more of elemental silicon, silicon oxide compound, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy. The tin-based material can be selected from one or more of elemental tin, tin oxide compound, and tin alloy.

[0175] [Electrolyte]

[0176] The electrolyte plays a role in conducting ions between the positive electrode tab and the negative electrode tab. The type of electrolyte is not particularly limited in the present application and can be selected as needed. For example, the electrolyte can be selected from at least one of a solid-state electrolyte and a liquid electrolyte (i.e., electrolyte solution).

[0177] In some embodiments, the electrolyte employs an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0178] In some embodiments, the electrolyte salt can be selected from one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonylimide (LiFSI), lithium bis-trifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate borate (LiDFOB), lithium difluorophosphate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorophosphate dioxalate (LiDFOP), and lithium tetrafluorophosphate oxalate (LiTFOP).

[0179] In some embodiments, the solvent can be selected from one or more of 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), butylene carbonate (BC), fluoroethylene carbonate (FEC), 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).

[0180] In some embodiments, the electrolyte can further include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, an additive capable of improving certain performance of the battery, such as an additive capable of improving overcharge performance of the battery, an additive capable of improving high-temperature performance of the battery, and an additive capable of improving low-temperature performance of the battery, etc.

[0181] [Separator]

[0182] In some embodiments of the lithium ion battery using the electrolyte and some embodiments of the lithium ion battery using a solid-state electrolyte, a separator is further included. The separator is disposed between the positive electrode sheet and the negative electrode sheet, and functions as a separator. The type of the separator is not particularly limited in the present application, and any known porous structure separator having good chemical stability and mechanical stability can be used. In some embodiments, the material of the separator can be selected from one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, and is not particularly limited. When the separator is a multi-layer composite film, the materials of the respective layers can be the same or different, and are not particularly limited.

[0183] [Lithium ion battery]

[0184] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be used to make an electrode assembly by a winding process or a stacking process, and the positive electrode sheet can include the high-nickel positive electrode active material of the present application.

[0185] In some embodiments, the lithium ion battery can include an outer package. The outer package can be used to package the electrode assembly and the electrolyte described above.

[0186] In some embodiments, the outer package of the lithium ion battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the lithium ion battery can also be a soft package, such as a bag-type soft package. The material of the soft package can be plastic, and as the plastic, polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS), etc. can be listed.

[0187] The shape of the lithium ion battery is not particularly limited in the present application, and the lithium ion battery can be cylindrical, square, or any other shape. For example, Figure 3 is a square structure lithium ion battery 5 as an example.

[0188] In some embodiments, with reference to Figure 4, the outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the lithium-ion battery 5 can be one or more, and those skilled in the art can select according to specific needs.

[0189] [Battery Module]

[0190] In some embodiments, lithium-ion batteries can be assembled into a battery module. The number of lithium-ion batteries contained in the battery module can be one or more. The specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0191] Figure 5 4 is an example of a battery module. Figure 5 In the battery module 4, the plurality of lithium-ion batteries 5 can be arranged in sequence along the length direction of the battery module 4. Of course, they can also be arranged in any other manner. The plurality of lithium-ion batteries 5 can further be fixed by fasteners.

[0192] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of lithium-ion batteries 5 are received in the receiving space.

[0193] [Battery Pack]

[0194] In some embodiments, the battery modules described above may also be assembled into a battery pack. Those skilled in the art may select the number of battery modules contained in the battery pack according to the application and capacity of the battery pack.

[0195] Figure 6 and Figure 7 The battery pack 1 is used as an example. Figure 6 and Figure 7 The battery pack 1 may include a battery box and multiple battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner in the battery box.

[0196] [Electrical devices]

[0197] In addition, the present application also provides an electrical device, which includes one or more of the lithium-ion batteries, battery modules, or battery packs provided in the present application. The lithium-ion batteries, battery modules, or battery packs can be used as the power source of the device, and can also be used as the energy storage unit of the device. The device can be, but is not limited to, a mobile device (such as a mobile phone, a laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc.

[0198] As the electrical device, a lithium-ion battery, a battery module or a battery pack can be selected according to its usage requirements.

[0199] Figure 8 This is an example device. This device is a pure electric vehicle, hybrid electric vehicle, or plug-in hybrid electric vehicle. To meet the device's requirements for high power and high energy density of lithium-ion batteries, a battery pack or battery module can be used.

[0200] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be lightweight and thin, and may use a lithium-ion battery as a power source.

[0201] Example

[0202] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and should not be construed as limiting the present application. If specific techniques or conditions are not specified in the embodiments, they are carried out according to the techniques or conditions described in the literature in this area or according to the product specifications. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products commonly used in this area that can be obtained commercially. The content of each component in the embodiments of the present application, unless otherwise specified, is measured by mass.

[0203] Example 1

[0204]

Preparation of high nickel ternary positive electrode active materials

[0205] S1, preparation of the first intermediate: weigh 13.02g of sodium aluminate (calculated as NaAlO2) and 19.37g of sodium silicate (calculated as Na2O·SiO2) and dissolve them in 2L of NaOH aqueous solution with a pH of 12.2, then add 953.00g of high nickel ternary precursor (Ni 0.9 Co 0.05 Mn 0.05)(OH)2, stirring was started, CO2 gas was introduced at a flow rate of 10 mL / min during stirring, stirring was continued at 30°C at a linear velocity of 3 m / s for 2 h, stirring was stopped, and the mixture was filtered, dried, and sieved to obtain a high nickel ternary precursor coated with silicon aluminum hydroxide, i.e., the first intermediate;

[0206] S2, preparation of the second intermediate: 980.62 g of the first intermediate, 472 g of lithium hydroxide (calculated as LiOH·H2O), and 8.33 g of titanium oxide (calculated as TiO2) were mixed uniformly, and sintered at 700°C in an oxygen atmosphere for 20 h to obtain a second intermediate;

[0207] S3, obtaining the target product: 1000 g of the second intermediate and 3.18 g of boron oxide (calculated as B2O3) were mixed evenly, and sintered at 200° C. in an oxygen atmosphere for 5 h to obtain the high-nickel positive electrode active material of Example 1.

[0208] Specific preparation parameters of high nickel positive electrode active materials of other embodiments and comparative examples are shown in Tables A to H.

[0209] The product parameters of the high nickel active materials of the examples and comparative examples and the performance parameters of the lithium ion batteries are shown in Tables 1 to 8.

[0210]

Positive electrode

[0211] The high-nickel positive electrode active material, binder polyvinylidene fluoride (PVDF), conductive agent acetylene black and solvent N-methylpyrrolidone (NMP) were mixed uniformly in a mass ratio of 94:3:3 to obtain a positive electrode slurry; the slurry was coated on aluminum foil, dried, cold pressed and cut to obtain a positive electrode sheet.

[0212]

Negative electrode

[0213] The negative electrode active material artificial graphite, hard carbon, conductive agent acetylene black, adhesive styrene butadiene rubber (SBR), thickener sodium carboxymethyl cellulose (CMC-Na) were mixed uniformly with deionized water in a mass ratio of 90:5:2:2:1 to obtain a mixture, and the mixture was coated on a copper foil, dried, and cold pressed to obtain the negative electrode sheet of Example 1.

[0214]

Electrolyte

[0215] EC:DEC:DMC were mixed in a volume ratio of 1:1:1, and LiPF6 was added to form an electrolyte, in which the concentration of LiPF6 was 1 mol / L.

[0216]

Isolation film

[0217] Polypropylene release film.

[0218] Preparation of lithium-ion batteries

[0219] The positive electrode sheet, the separator, and the negative electrode sheet are stacked in order, the separator is positioned between the positive electrode sheet and the negative electrode sheet to play a role of separation, and then the lithium ion battery is obtained after the square bare cell is wound, is packaged in an aluminum plastic film, is injected with a corresponding non-aqueous electrolyte, is sealed, is subjected to processes such as standing, hot and cold pressing, formation, clamping, and capacity distribution, and the like.

[0220]

High-nickel positive electrode active material related parameter test

[0221] 1. Surface lithium impurity content test

[0222] Acid-base titration method: 30 g of the high-nickel positive electrode active material of the embodiment is placed in 100 ml of deionized water and stirred for 30 min, and then filtered after standing for 5 min. 10 mL of the supernatant is titrated with a 0.05 mol / L hydrochloric acid standard solution. A pH electrode is used as an indicator electrode, and the end point is determined by means of a potential change jump, and the surface lithium impurity content Q of the positive electrode material (unit: ppm) is calculated. The specific formula is Q = V2 x C x 6.94 x n x 100 / (m x 1000) x 100000, wherein C is the concentration of the hydrochloric acid standard solution (unit: mol / L); V2 is the total volume of the hydrochloric acid standard solution consumed from the start of titration to the second titration end point (unit: mL); n is the ratio of V2 to V1, V1 is the total volume of the 10 mL supernatant after titration and V2; m is the mass of the sample (unit: g).

[0223] 2. Test of the content of each element in the high-nickel positive electrode active material

[0224] An inductively coupled plasma optical emission spectrometer (ICP-OES) is used, and the equipment model is ICAP7400 of Thermo Fisher Scientific, USA. First, 1 g of the sample is weighed in a beaker, 25 ml of a 25% HNO3 solution is added to the sample to dissolve the sample, and 475 ml of deionized water is used for dilution, and then the diluted liquid is placed into the instrument equipment for target element analysis, and the content of the target element is calculated.

[0225] 3. Test of the mass distribution of lithium elements in the core and the shell

[0226] An IB-19500CP ion polisher and EPMA (Electron Probe Microanalysis) equipment were used in combination. The sample preparation tools were cleaned, and the sample preparation glue (a colloid formed by dispersing PVDF in NMP, with a PVDF content of 8%) was mixed with the sample powder (the powder weight was approximately 5 times that of the glue). The mixture was evenly applied to the copper foil and dried at 60°C for 30 minutes. The prepared sample was cut into 6mm x 6mm pieces using scissors, fixed on the sample stage, and placed in an ion polisher (model: IB-19500CP) for cutting, obtaining a cross-sectional image with a clear boundary between the core structure and the layer structure.

[0227] Combined with the cross-sectional diagram, EPMA testing was performed to analyze the lithium element at three points in the core and shell respectively. Finally, the average value was taken to obtain the mass percentage of lithium element in the core and shell. The detailed operation process of EPMA can be found in standard NFA92-801-4-2006 (NF A92-801-4-2006, Advanced Industrial Ceramics, Test Methods for Ceramic Coatings, Part 4: Measurement of Chemical Composition by Electrical Probe Microanalysis (EPMA)).

[0228] 4. Volume average particle size Dv50 test

[0229] Take a clean beaker, add an appropriate amount of the sample to be tested, and ultrasonically control it at 120W / 5min to ensure that the sample is completely dispersed. The test instrument is the American Malvern 2000. After the sample is poured into the injection tower, it circulates with the solution to the test optical system. Under the irradiation of the laser beam, the particle size distribution characteristics of the particles can be obtained by receiving and measuring the energy distribution of the scattered light (shading degree: 8-12%). Draw a particle size volume distribution diagram based on the test data (see attached). Figure 2 , which is a particle size volume distribution diagram of the high-nickel active material of Example 1. From this distribution diagram, it can be seen that if 50% of the particles by volume have a diameter greater than a certain Dv50 value, and another 50% of the particles by volume have a diameter less than this Dv50 value, then this Dv50 value is the volume average particle size of the particles.

[0230] 5. Shell thickness test

[0231] An IB-19500CP ion polisher and a US-based FEI Tecnai G2 transmission electron microscope were used. Sample preparation tools were cleaned, and the sample preparation glue (a colloid formed by dispersing PVDF in NMP, with an 8% PVDF content by weight) was mixed with the sample powder (the powder weight was approximately five times that of the glue). The mixture was evenly applied to copper foil and dried at 60°C for 30 minutes. The prepared sample was cut into 6mm x 6mm pieces using scissors, secured to a sample stage, and placed in an ion polisher (Model: IB-19500CP) for cutting. The cut sample was then placed in a US-based FEI Tecnai G2 transmission electron microscope for shell thickness testing, which revealed the particle shell thickness.

[0232] The methods for determining the above-mentioned relevant parameters of the comparative example are the same as those of the embodiment.

[0233]

Battery performance test

[0234] 1. Initial discharge capacity

[0235] The lithium-ion battery of the example was placed in a 25°C oven, allowed to rest for 5 minutes, and then subjected to a charge and discharge test. The charge and discharge process was as follows: discharge at a constant current of 1 / 3C to 2.8V, rest for 5 minutes, continue charging at a constant current of 1 / 3C to 4.25V, then charge at a constant voltage at 4.25V to a current of ≤0.05mA, rest for 5 minutes, and then discharge at a constant current of 1 / 3C to 2.8V. The discharge capacity at this point is the initial discharge capacity described in this application.

[0236] 2. Cycle capacity retention rate

[0237] All lithium-ion batteries from the examples and comparative examples were subjected to charge and discharge tests at 25°C. One charge-discharge cycle was as follows: 1C constant-current charging to 4.25V, followed by constant-voltage charging at 4.25V until the current was ≤0.05mA, followed by 5 minutes of rest, and then 1C constant-current discharge to 2.8V. The battery capacity at this point was recorded as C1. This constituted one charge-discharge cycle. This process was repeated 300 times, and the battery capacity at this point was recorded as C300. Cycle capacity retention = C300 / C1 × 100%.

[0238] The cycle capacity retention rates in Tables 1 to 8 were all measured after 300 cycles.

[0239] 3. 70℃ flatulence performance test

[0240] The initial volume of a single battery was tested by the drainage method at 70°C for a battery of 100% SOC (State of Charge) (nominal capacity 2.25 Ah), the battery was taken out and put into a storage oven at 70°C for 48 h, after cooling to room temperature, the volume of the battery was tested by the drainage method again, V1, the above steps were repeated, after 20 days of storage, the volume of the battery was tested by the drainage method, V10, and the amount of swelling = (V10-V0) / 2.25.

[0241] The amount of swelling in Tables 1-8 was measured after 20 days of storage.

[0242] The battery performance of the comparative example was measured in the same way as the examples.

[0243]

[0244]

[0245]

[0246]

[0247]

[0248]

[0249]

[0250]

[0251]

[0252]

[0253]

[0254]

[0255] From the comprehensive analysis of Example 1 and Examples 34-35 in Table 8, it can be seen that when the volume average particle size Dv50 of the high-nickel positive electrode active material is 1.5-20 μm and the shell thickness is 0.001-1 μm, the amount of surface lithium impurities and the amount of swelling inside the lithium ion battery are improved, and the lithium ion battery has good discharge capacity, safety performance and cycle performance.

[0256] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely illustrative, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A core-shell structured high nickel positive electrode active material, wherein: The core includes Li 1+a [Ni x Co y Mn z M b O2, where 0.6 ≤ x < 1, 0 < y < 0.3, 0 < z < 0.3, 0 < a < 0.2, 0 < b < 0.2, x + y + z + b = 1, and M is one or more of Mg, Ca, Sb, Ce, Ti, Zr, Sr, Al, Zn, Mo, and B; The shell includes a first shell layer covering the core, and a second shell layer covering the first shell layer; wherein, The first shell is a fast ion conductor composed of four elements: lithium, aluminum, silicon and oxygen; The second shell layer includes an oxide of element R, wherein R is selected from one or more of Al, B, Ti, P, Co, and La; wherein, The shell further includes a transition layer formed between the first shell and the second shell, wherein the transition layer includes one or more fast ion conductors Li formed by the first shell component and the second shell component. p R q O w , where 1≤p≤4, 1≤q≤5, 1≤w≤12, and p, q and w are all integers.

2. The high nickel positive electrode active material according to claim 1, wherein The fast ion conductor of the first shell layer is Li α Al X Si Y O4, where 0 < X < 2.4, 0 < Y < 1.8, 0.8 ≤ α ≤ 1.2, and the ratio of the stoichiometric coefficient X of aluminum element to the stoichiometric coefficient Y of silicon element is 0.8 to 1.

2.

3. The high nickel positive electrode active material according to any one of claims 1 to 2, wherein The fast ion conductor Li in the transition layer p R q O w Selected from LiAlO2, Li3BO3, Li4Ti5O 12 , Li3PO4, LiCoO2 or LiLaO.

4. The high nickel positive electrode active material according to any one of claims 1 to 2, wherein The x is 0.8≤x<1, the M is one or more of Sb, Ti, Zr, Sr, Al, and B, and the R is one or more of Al, La, B, Co, and Ti.

5. The high nickel positive electrode active material according to any one of claims 1 to 2, wherein The mass ratio of the lithium element in the core to the lithium element in the shell is 40 to 1300:

1.

6. The high nickel positive electrode active material according to any one of claims 1 to 2, wherein When M is selected from one or more of Al, B or Ti, R is different from M, and the mass content of the M element in the high nickel positive electrode active material is 1000 to 5000 ppm based on the total mass of the high nickel positive electrode active material.

7. The high nickel positive electrode active material according to any one of claims 1 to 2, wherein When M is selected from one or more of Al, B or Ti, R is different from M, and the mass content of the R element is 100 to 20,000 ppm based on the total mass of the high-nickel positive electrode active material.

8. The high nickel positive electrode active material according to any one of claims 1 to 2, wherein In the high-nickel positive electrode active material, the mass ratio of the silicon element to the R element is 0.1 to 7.0:

1.

9. The high nickel positive electrode active material according to any one of claims 1 to 2, wherein Based on the total mass of the high-nickel positive electrode active material, the total mass content of silicon and aluminum in the first shell layer is 435 to 13150 ppm.

10. The high nickel positive electrode active material according to any one of claims 1 to 2, wherein The volume average particle size Dv50 of the high nickel positive electrode active material is 1.5 to 20 μm, and the total thickness of the shell layer is 0.001 to 1 μm.

11. A method for preparing a high-nickel positive electrode active material, comprising the following steps: S1: providing a high nickel ternary precursor coated with silicon aluminum hydroxide to obtain a first intermediate; S2: mixing the first intermediate with an M precursor and a lithium precursor, and sintering the mixture to obtain a second intermediate; S3: mixing the second intermediate with the R precursor, and sintering to obtain the high-nickel positive electrode active material; in, The high nickel positive electrode active material is a core-shell structure. The core includes Li 1+a [Ni x Co y Mn z M b O2, where 0.6 ≤ x < 1, 0 < y < 0.3, 0 < z < 0.3, 0 < a < 0.2, 0 < b < 0.2, x + y + z + b = 1, and M is one or more of Mg, Ca, Sb, Ce, Ti, Zr, Sr, Al, Zn, Mo, and B; The shell includes a first shell layer covering the core, and a second shell layer covering the first shell layer; wherein, The first shell is a fast ion conductor composed of four elements: lithium, aluminum, silicon and oxygen; The second shell layer includes an oxide of element R, wherein R is selected from one or more of Al, B, Ti, P, Co, and La; wherein, The shell further includes a transition layer formed between the first shell and the second shell, wherein the transition layer includes one or more fast ion conductors Li formed by the first shell component and the second shell component. p R q O w , where 1≤p≤4, 1≤q≤5, 1≤w≤12, and p, q and w are all integers.

12. The preparation method according to claim 11, wherein In step S1, the preparation process of the high nickel ternary precursor coated with silicon aluminum hydroxide is as follows: (a) completely dissolving an aluminum precursor and a silicon precursor in an alkaline solution, and then adding a high nickel ternary precursor to obtain a solid-liquid mixture; (b) lowering the pH of the solid-liquid mixture to induce a hydrolysis-in-situ precipitation reaction between the aluminum precursor and the silicon precursor to obtain a high-nickel ternary precursor coated with silicon-aluminum hydroxide.

13. A lithium-ion battery comprising the high-nickel positive electrode active material according to any one of claims 1 to 10 or the high-nickel positive electrode active material prepared by the preparation method according to claim 11 or 12.

14. A battery module comprising the lithium-ion battery according to claim 13. 15 . A battery pack comprising any one of the lithium-ion battery according to claim 13 or the battery module according to claim 14 .

16. An electrical device, comprising any one of the lithium-ion battery according to claim 13, the battery module according to claim 14, or the battery pack according to claim 15, wherein the lithium-ion battery, the battery module, or the battery pack is used as a power source for the electrical device or an energy storage unit for the electrical device.

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