Lithium-ion secondary battery, electric device and positive electrode material

Abstract

Provided in the present disclosure are a lithium-ion secondary battery, an electric device and a positive electrode material. The lithium-ion secondary battery comprises a positive electrode sheet, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer that is located on at least one side of the positive electrode current collector and comprises a positive electrode material, the positive electrode material comprising a lithium transition metal oxide which comprises secondary particles formed by a plurality of primary particles having a particle size of 0.2-1 μm. The lithium transition metal oxide comprises nickel, cobalt and manganese, wherein on the basis of the total moles of nickel, cobalt and manganese, the molar percentage of nickel is greater than or equal to 50% and less than 100%, and the molar percentage of manganese is greater than or equal to that of cobalt. The lithium transition metal oxide further comprises a modifying element which is one or more of zirconium, yttrium, sodium, potassium, phosphorus, antimony, aluminum, titanium, boron, tungsten and carbon. At 100% SOC, the oxygen release temperature of the positive electrode sheet as determined by thermogravimetry-mass spectrometry is 210-230°C.

Description

Lithium-ion secondary batteries, electrical devices and cathode materials

[0001] Cross-references to related applications

[0002] This disclosure is based on and claims priority to Chinese Patent Application No. 202510486752.1, filed on April 17, 2025, entitled "Lithium-ion Secondary Battery, Electrical Device and Cathode Material", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to the field of battery technology, and in particular to a lithium-ion secondary battery, an electrical device, and a positive electrode material. Background Technology

[0004] In recent years, with the increasingly wide application of lithium-ion batteries, they have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power plants, as well as in many fields such as power tools, electric bicycles, electric motorcycles, electric cars, and aerospace.

[0005] Due to the significant advancements in lithium-ion batteries, higher requirements have been placed on their cycle performance and safety performance. Summary of the Invention

[0006] This disclosure is made in view of the above-mentioned problems, and its object is to provide a lithium-ion secondary battery, an electrical device, and a positive electrode material. The lithium-ion secondary battery provided by this disclosure has improved cycle performance and safety performance.

[0007] To achieve the above objectives, the first aspect of this disclosure provides a lithium-ion secondary battery, including a positive electrode sheet. The positive electrode sheet includes a positive current collector and a positive electrode film layer located on at least one side of the positive current collector and including a positive electrode material. The positive electrode material includes a lithium transition metal oxide, which comprises secondary particles formed by a plurality of primary particles with a particle size of 0.2 μm to 1 μm. The lithium transition metal oxide includes nickel, cobalt, and manganese. Based on the total molar number of nickel, cobalt, and manganese, the molar percentage of nickel is greater than or equal to 50% and less than 100%, and the molar content of manganese is greater than or equal to the molar content of cobalt. The lithium transition metal oxide also includes a modifying element, which is one or more of zirconium, yttrium, sodium, potassium, phosphorus, antimony, aluminum, titanium, boron, tungsten, and carbon. At 100% SOC, the oxygen release temperature of the positive electrode sheet in the thermogravimetric-mass spectrometry test results is 210℃ to 230℃. Therefore, lithium transition metal oxides have high structural stability and small volume change during cycling, which is beneficial to improving the cycle performance of secondary batteries. In addition, the cathode material has good thermal stability, which is beneficial to improving the cycle performance and safety performance of lithium-ion secondary batteries.

[0008] In some implementations, at 100% SOC, the oxygen release temperature of the positive electrode sheet, as measured by thermogravimetric-mass spectrometry (TGA), is 215°C to 230°C. This is beneficial to the cycle performance and safety performance of the lithium-ion secondary battery.

[0009] In some embodiments, at 100% SOC, the peak decomposition temperature of the positive electrode sheet in thermogravimetric-mass spectrometry (TGA) tests is 215℃~235℃. This reflects the good thermal stability of the positive electrode material, which is beneficial to the cycle performance and safety performance of lithium-ion secondary batteries.

[0010] In some embodiments, at 100% SOC, the oxygen release in the positive electrode sheet measured by thermogravimetric-mass spectrometry is 80 μL / mg to 115 μL / mg. This reflects the good thermal stability of the positive electrode material, which is beneficial to the cycle performance and safety performance of lithium-ion secondary batteries.

[0011] In some implementations, based on the total molar amounts of nickel, cobalt, and manganese, the molar content of manganese is M1, the molar content of cobalt is M2, and 0 ≤ M1 - M2 ≤ 8%. This is beneficial for further improving the stability of the cathode material, thereby improving the cycle performance and safety performance of the lithium-ion secondary battery.

[0012] In some embodiments, the molar content of manganese in the lithium transition metal oxide is 4% to 13% based on the total molar number of nickel, cobalt, and manganese. This is beneficial for improving the cycle life and safety performance of lithium-ion secondary batteries, and also helps to reduce costs.

[0013] In some embodiments, the molar content of cobalt in the lithium transition metal oxide is 4% to 10% based on the total molar number of nickel, cobalt, and manganese. This reduces costs while maintaining the conductivity of the cathode material, which is beneficial to the electrical performance of the secondary battery.

[0014] In some embodiments, the content of the modifying element is less than or equal to 1% based on the total mass of the lithium transition metal oxide. This is beneficial for improving the structural stability of the cathode material and enhancing its safety performance.

[0015] In some embodiments, the zirconium, yttrium, sodium, potassium, phosphorus, and antimony elements in the modified elements are uniformly distributed in the bulk phase of the lithium transition metal oxide. This helps to improve the stability of the cathode material and enhance the safety performance of the secondary battery.

[0016] In some embodiments, the modified elements, such as aluminum, titanium, boron, tungsten, and carbon, are distributed on the surface of the lithium transition metal oxide. This improves the stability of the cathode material and enhances the cycle stability of the lithium-ion secondary battery.

[0017] In some embodiments, the modifying elements include aluminum and / or zirconium. This is beneficial for further improving the stability of the cathode material.

[0018] In some implementations, the lithium-nickel mixing ratio of the cathode material is 2% to 3%. This is beneficial for improving the capacity of lithium-ion secondary batteries, as well as their cycle performance and safety.

[0019] In some implementations, the molar percentage of nickel is 80% to 92% based on the total molar number of nickel, cobalt, and manganese. This is beneficial for improving the energy density of the secondary battery.

[0020] In some embodiments, the cathode material satisfies one or more of the following characteristics: (1) 2μm≤Dv2≤4μm; (2) 3μm≤Dv10≤7μm; (3) 7μm≤Dv50≤13μm; (4) 16μm≤Dv90≤24μm; (5) 20μm≤Dv99≤35μm. This is beneficial for improving the specific capacity of the cathode material, and also for ensuring good structural stability, thereby improving the cycle performance of the lithium-ion secondary battery.

[0021] In some embodiments, the tap density of the cathode material is 2.4 g / cm³. 3 ~3.0g / cm 3 This is beneficial for improving the energy density of lithium-ion secondary batteries.

[0022] A second aspect of this disclosure also provides an electrical device including a lithium-ion secondary battery according to the first aspect of this disclosure.

[0023] The third aspect of this disclosure also provides a cathode material, comprising a lithium transition metal oxide, wherein the lithium transition metal oxide comprises secondary particles formed by multiple primary particles with a particle size of 0.2 μm to 1 μm; the lithium transition metal oxide comprises nickel, cobalt, and manganese, wherein, based on the total molar number of nickel, cobalt, and manganese, the molar percentage of nickel is greater than or equal to 50% and less than 100%, and the molar content of manganese is greater than or equal to the molar content of cobalt; the lithium transition metal oxide further comprises modifying elements, which are one or more selected from zirconium, yttrium, sodium, potassium, phosphorus, antimony, aluminum, titanium, boron, tungsten, and carbon; the oxygen release temperature of the cathode material in thermogravimetric-mass spectrometry testing at 100% SOC is 210℃ to 230℃. This is beneficial for improving the cycle performance and safety performance of lithium-ion secondary batteries.

[0024] In some embodiments, at 100% SOC, the oxygen release temperature of the cathode material, as determined by thermogravimetric-mass spectrometry (TGA), is 215°C to 230°C. This is beneficial to the cycle performance and safety of the lithium-ion secondary battery.

[0025] In some embodiments, at 100% SOC, the peak decomposition temperature of the cathode material in thermogravimetric-mass spectrometry (TGA) tests is 215℃~235℃. This reflects the good thermal stability of the cathode material, which is beneficial to the cycle performance and safety performance of lithium-ion secondary batteries.

[0026] In some embodiments, at 100% SOC, the oxygen release of the cathode material, as measured by thermogravimetric-mass spectrometry (TGA), ranges from 80 μL / mg to 115 μL / mg. This reflects the good thermal stability of the cathode material, which is beneficial to the cycle performance and safety of lithium-ion secondary batteries.

[0027] In some implementations, based on the total molar amounts of nickel, cobalt, and manganese, the molar content of manganese is M1, the molar content of cobalt is M2, and 0 ≤ M1 - M2 ≤ 8%. This is beneficial for further improving the stability of the cathode material, thereby improving the cycle performance and safety performance of the lithium-ion secondary battery.

[0028] In some embodiments, the molar content of manganese in the lithium transition metal oxide is 4% to 13% based on the total molar number of nickel, cobalt, and manganese. This is beneficial for improving the cycle life and safety performance of lithium-ion secondary batteries, and also helps to reduce costs.

[0029] In some embodiments, the molar content of cobalt in the lithium transition metal oxide is 4% to 10% based on the total molar number of nickel, cobalt, and manganese. This reduces costs while maintaining the conductivity of the cathode material, which is beneficial to the electrical performance of the secondary battery.

[0030] In some embodiments, the content of the modifying element is less than or equal to 1% based on the total mass of the lithium transition metal oxide. This is beneficial for improving the structural stability of the cathode material and enhancing its safety performance.

[0031] In some embodiments, the zirconium, yttrium, sodium, potassium, phosphorus, and antimony elements in the modified elements are uniformly distributed in the bulk phase of the lithium transition metal oxide. This helps to improve the stability of the cathode material and enhance the safety performance of the secondary battery.

[0032] In some embodiments, the modified elements, such as aluminum, titanium, boron, tungsten, and carbon, are distributed on the surface of the lithium transition metal oxide. This improves the stability of the cathode material and enhances the cycle stability of the lithium-ion secondary battery.

[0033] In some embodiments, the modifying elements include aluminum and / or zirconium. This is beneficial for further improving the stability of the cathode material.

[0034] In some implementations, the lithium-nickel mixing ratio of the cathode material is 2% to 3%. This is beneficial for improving the capacity of lithium-ion secondary batteries, as well as their cycle performance and safety.

[0035] In some implementations, the molar percentage of nickel is 80% to 92% based on the total molar number of nickel, cobalt, and manganese. This is beneficial for improving the energy density of the secondary battery.

[0036] In some embodiments, the cathode material satisfies one or more of the following characteristics: (1) 2μm≤Dv2≤4μm; (2) 3μm≤Dv10≤7μm; (3) 7μm≤Dv50≤13μm; (4) 16μm≤Dv90≤24μm; (5) 20μm≤Dv99≤35μm. This is beneficial for improving the specific capacity of the cathode material, and also for ensuring good structural stability, thereby improving the cycle performance of the lithium-ion secondary battery.

[0037] In some embodiments, the tap density of the cathode material is 2.4 g / cm³. 3 ~3.0g / cm 3 This is beneficial for improving the energy density of lithium-ion secondary batteries. Attached Figure Description

[0038] Figure 1 is a schematic diagram of a secondary battery according to an embodiment of the present disclosure.

[0039] Figure 2 is an exploded view of a secondary battery according to an embodiment of the present disclosure shown in Figure 1.

[0040] Figure 3 is a schematic diagram of a battery module according to one embodiment of the present disclosure.

[0041] Figure 4 is a schematic diagram of a battery pack according to one embodiment of the present disclosure.

[0042] Figure 5 is an exploded view of a battery pack according to an embodiment of the present disclosure, as shown in Figure 4.

[0043] Figure 6 is a schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of the present disclosure.

[0044] Figure 7 is a scanning electron microscope image of the cathode material prepared in Embodiment 1 of this disclosure.

[0045] Figure 8 shows the thermogravimetric-mass spectrometry test curve of the positive electrode in Embodiment 1 of this disclosure.

[0046] Figure 9 is the XRD pattern of the positive electrode sheet in Embodiment 1 of this disclosure.

[0047] Explanation of reference numerals in the attached figures:

[0048] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Battery cell; 51 Housing; 52 Electrode assembly; 53 Cover plate. Detailed Implementation

[0049] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the lithium-ion secondary battery, power supply device, and positive electrode material of this disclosure. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this disclosure and are not intended to limit the subject matter of the claims.

[0050] The "range" disclosed in this disclosure is defined by a lower limit and an upper limit, whereby a given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and if maximum range values ​​3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this disclosure, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0051] Unless otherwise specified, all embodiments and optional embodiments of this disclosure can be combined to form new technical solutions.

[0052] Unless otherwise specified, all technical features and optional technical features of this disclosure can be combined to form new technical solutions.

[0053] Unless otherwise specified, all steps of this disclosure may be performed sequentially or randomly, preferably sequentially. For example, if a method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if it is mentioned that the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0054] In this disclosure, the term "oxygen release temperature" refers to the temperature at which the positive electrode (or positive electrode material) begins to release oxygen. Specifically, after fully charging the positive electrode, thermogravimetric-mass spectrometry (TGA) is performed on it. In the TGA results, an oxygen mass spectrum-temperature (°C) curve is plotted, and the temperature at the intersection of the tangent line and the curve with the left edge of the oxygen release peak is the oxygen release temperature. A higher oxygen release temperature of the positive electrode material reflects better thermal stability, which is more beneficial to the cycle performance and safety performance of the battery.

[0055] In this disclosure, the term "peak decomposition temperature" refers to the temperature at which the oxygen release from the positive electrode (or positive electrode material) is most intense. Specifically, after fully charging the positive electrode, thermogravimetric-mass spectrometry (TGA) is performed on it, and a differential thermogravimetric curve is plotted. The temperature corresponding to the highest peak of the oxygen release in the curve is the peak decomposition temperature. The lower the peak decomposition temperature, the better the thermal stability of the positive electrode material, which is more beneficial to the cycle performance and safety performance of the battery.

[0056] In this disclosure, the term "oxygen release" refers to the oxygen content released per unit mass of sample, which can be calculated as follows: After fully charging the positive electrode, perform thermogravimetric-mass spectrometry (TGA) testing on the positive electrode. In the TGA test results, oxygen release = (peak area of ​​released oxygen peak / standard peak area) * standard oxygen volume / sample mass. The lower the oxygen release, the better the thermal stability of the positive electrode material, which is more beneficial to the cycle performance and safety performance of the battery.

[0057] The term "secondary particle" as used in this article refers to a particle formed by multiple primary particles. Secondary particles typically have a relatively regular shape, which can be spherical or near-spherical. The size of the primary particles forming the secondary particle is usually significantly smaller than that of the primary particles existing in a dispersed form, and grain boundaries may exist between adjacent primary particles.

[0058] The term "primary particle" as used in this article refers to a particle that appears as a single, integral entity under an electron microscope. The particle has complete boundaries, and while defects may exist within it, there are no complete boundaries within the particle sufficient to divide it into two or more particles.

[0059] Ternary materials are one of the most commonly used cathode materials. As the requirements for energy density become higher and higher, the nickel content in ternary materials continues to increase. As a result, the thermal stability of ternary materials deteriorates, affecting the cycle performance and safety performance of secondary batteries.

[0060] Based on this, the present disclosure provides a new lithium-ion secondary battery, an electrical device, and a positive electrode material. The lithium-ion secondary battery of the present disclosure has improved cycle performance and safety performance.

[0061] Lithium-ion secondary batteries

[0062] The first aspect of this disclosure provides a lithium-ion secondary battery, including a positive electrode sheet, which includes a positive current collector and a positive electrode film layer located on at least one side of the positive current collector and including a positive electrode material. The positive electrode material includes a lithium transition metal oxide, which includes secondary particles formed by a plurality of primary particles with a particle size of 0.2 μm to 1 μm. The lithium transition metal oxide includes nickel, cobalt, and manganese. Based on the total molar number of nickel, cobalt, and manganese, the molar percentage of nickel is greater than or equal to 50% and less than 100%, and the molar content of manganese is greater than or equal to the molar content of cobalt. The lithium transition metal oxide also includes a modifying element, which is one or more of zirconium, yttrium, sodium, potassium, phosphorus, antimony, aluminum, titanium, boron, tungsten, and carbon. At 100% SOC, the oxygen release temperature of the positive electrode sheet in the thermogravimetric-mass spectrometry test results is 210℃ to 230℃.

[0063] In this disclosure, the lithium transition metal oxide includes secondary particles formed from primary particles. Since the structure of these secondary particles is relatively stable, it reduces microcracks and particle shedding caused by volume changes during charging and discharging, thus improving the cycle stability of the lithium-ion secondary battery. Furthermore, by setting the Mn content in the lithium transition metal oxide to be greater than or equal to the Co content and by using modifying elements to modify the cathode material, the thermal stability of the cathode material is improved, thereby enhancing the cycle and safety performance of the lithium-ion secondary battery. In addition, since the cathode material is in its most active state when the cathode is fully charged, its thermal stability in the secondary battery can be better evaluated at this time. Therefore, by ensuring that the oxygen release temperature measured by thermogravimetric-mass spectrometry (TGA) of the cathode in a fully charged state is within the aforementioned range, this disclosure further reflects the good thermal stability of the cathode material, which is beneficial to the cycle performance and safety performance of the lithium-ion secondary battery.

[0064] For example, at 100% SOC, the oxygen release temperature in the thermogravimetric-mass spectrometry test results of the positive electrode is a value between 210℃, 212℃, 213℃, 215℃, 216℃, 217℃, 218℃, 219℃, 220℃, 222℃, 223℃, 225℃, 226℃, 227℃, 228℃, 229℃, 230℃, or any combination thereof.

[0065] In some embodiments, at 100% SOC, the oxygen release temperature of the positive electrode sheet was 215℃~230℃ in thermogravimetric-mass spectrometry (TGA) tests. This further reflects the good thermal stability of the positive electrode material, which is beneficial to the cycle performance and safety performance of lithium-ion secondary batteries.

[0066] In some embodiments, at 100% SOC, the peak decomposition temperature in the thermogravimetric-mass spectrometry (TGA) test results of the positive electrode is 215°C to 235°C. In this disclosure, the peak decomposition temperature of the positive electrode measured by TGA under full charge is within the above range, indicating a relatively low peak decomposition temperature. This further reflects the good thermal stability of the positive electrode material, which is beneficial to the cycle performance and safety performance of the lithium-ion secondary battery. For example, at 100% SOC, the peak decomposition temperature in the TGA test results of the positive electrode is a value between 215°C, 216°C, 217°C, 218°C, 219°C, 220°C, 221°C, 222°C, 223°C, 224°C, 225°C, 226°C, 227°C, 228°C, 229°C, 230°C, 232°C, 233°C, 235°C, or any combination thereof.

[0067] In some embodiments, at 100% SOC, the oxygen release of the positive electrode sheet measured by thermogravimetric-mass spectrometry (TGA-MS) is 80 μL / mg to 115 μL / mg. The oxygen release of the positive electrode sheet in this disclosure, measured by TGA-MS under full charge, falls within the above range, indicating a low oxygen release. This further reflects the good thermal stability of the positive electrode material, which is beneficial to the cycle performance and safety of lithium-ion secondary batteries. For example, at 100% SOC, the oxygen release in the thermogravimetric-mass spectrometry test results of the positive electrode sheet is a value between 80 uL / mg, 82 uL / mg, 85 uL / mg, 88 uL / mg, 90 uL / mg, 92 uL / mg, 95 uL / mg, 98 uL / mg, 100 uL / mg, 102 uL / mg, 105 uL / mg, 108 uL / mg, 110 uL / mg, 112 uL / mg, 115 uL / mg, or any combination thereof.

[0068] In this disclosure, the oxygen release temperature, peak decomposition temperature, and oxygen release amount of the positive electrode sheet can be tested in the following manner. Specifically, the positive electrode sheet obtained after disassembling a secondary battery charged to 100% SOC is cleaned with a solvent, and the binder is removed by burning ash. After drying, approximately 50 mg of the positive electrode material is weighed into a high-footed Al2O3 crucible, leveled, and placed in a STA (Simultaneous Thermal Analyzer) for heating and decomposition to release oxygen under an argon atmosphere. The purge gas flow rate is set to 50 mL / min, the protective gas flow rate to 20 mL / min, the heating rate to 10 °C / min, and the temperature range to 35 °C–1400 °C. After the oxygen enters a QMS (Quadrupole Mass Spectrometer), an MS curve with an ion concentration of 32 is obtained. By peak labeling and integration of the MS curve, the oxygen release temperature, peak decomposition temperature, and peak area of ​​the positive electrode material can be obtained, and the oxygen release amount can be calculated.

[0069] In some embodiments, based on the total molar number of nickel, cobalt, and manganese, the molar content of manganese is M1, the molar content of cobalt is M2, and 0 ≤ M1 - M2 ≤ 8%. By controlling M1-M2 within the above range, the manganese content in the cathode material is further increased, which is beneficial to further improving the stability of the cathode material, thereby improving the cycle performance and safety performance of the lithium-ion secondary battery. For example, M1-M2 is a value within a range of 0, 1, 3, 5, 8, or any two of these.

[0070] In some embodiments, the molar content of manganese in the lithium transition metal oxide is 4% to 13% based on the total molar number of nickel, cobalt, and manganese; optionally, it is 6% to 10%. Controlling the molar content of manganese in the lithium transition metal oxide within this range is beneficial for improving the thermal stability of the cathode material, thereby enhancing the cycle life and safety performance of the lithium-ion secondary battery. Furthermore, reducing the cobalt content in the lithium transition metal oxide helps lower costs. Exemplarily, the molar content of manganese is 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, or a value within a range consisting of any two of these values.

[0071] In some embodiments, the molar content of cobalt in the lithium transition metal oxide is 4% to 10% based on the total molar number of nickel, cobalt, and manganese. Optionally, the molar content of cobalt is 6% to 9%. By keeping the molar content of cobalt in the lithium transition metal oxide within the above range, costs can be reduced while ensuring the conductivity of the cathode material, which is beneficial to the electrical performance of the secondary battery. Exemplarily, the molar content of cobalt is 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a value within a range of any two of these values.

[0072] In some embodiments, the content of the modifying element is less than or equal to 1% based on the total mass of the lithium transition metal oxide. This is beneficial for improving the structural stability of the cathode material, increasing the oxygen vacancy formation energy, and improving the material's safety performance. For example, the content of the modifying element based on the total weight of the lithium transition metal oxide can be 0, 0.2%, 0.5%, 0.8%, 1.0%, or a value within a range of any two of these values.

[0073] In some embodiments, the zirconium, yttrium, sodium, potassium, phosphorus, and antimony elements in the modified elements are uniformly distributed in the bulk phase of the lithium transition metal oxide. By ensuring uniform distribution of the modified elements in the bulk phase of the lithium transition metal oxide, the phase transition suppression effects of zirconium, yttrium, sodium, potassium, phosphorus, and antimony are enhanced, thereby improving the stability of the cathode material and ultimately improving the safety performance of the secondary battery.

[0074] In some embodiments, the aluminum, titanium, boron, tungsten, and carbon elements in the modification are distributed on the surface of the lithium transition metal oxide. This allows the aluminum, titanium, boron, tungsten, and carbon elements to isolate side reactions between the lithium transition metal and the electrolyte, thereby improving the stability of the cathode material and reducing lithium-ion consumption during cycling, thus enhancing the cycle stability of the lithium-ion secondary battery. In some embodiments, the modification elements include aluminum and / or zirconium.

[0075] In this disclosure, the types of modified elements and their mass percentage in lithium transition metal oxides can be determined by inductively coupled plasma optical emission spectrometry (ICP). Specifically, 0.2 g of cathode material powder is weighed into a 100 mL beaker, 10 mL of 10% w / w nitric acid solution is added, and the mixture is heated and digested at 120 °C for 0.5 hours. The solution is then diluted to volume with a 100 mL volumetric flask. Another 1 mL of the solution is pipetted into the 100 mL volumetric flask and diluted to volume to obtain the test solution. The mass fraction of each element in the test solution is then determined using inductively coupled plasma optical emission spectrometry.

[0076] In some embodiments, the molar percentage of nickel is 80% to 92% based on the total molar number of nickel, cobalt, and manganese; alternatively, it is 80% to 86%. Exemplarily, the molar percentage of nickel is a value within a range of 80%, 83%, 85%, 88%, 90%, 92%, or any combination thereof. Therefore, a higher nickel content in the cathode material is beneficial for improving the energy density of the secondary battery.

[0077] In some embodiments, the chemical formula of the lithium transition metal oxide includes: Li a Ni b Co c Mn d N e O fN includes one or more of Zr, Y, Na, K, P, Sb, Al, Ti, B, W, and C, with 0.8≤a≤1.1, 0.5≤b<1, 0.04≤c<1, 0.05≤d<1, 0.001≤e<1, 1.8≤f≤2.2, and b+c+d+e=1. Optionally, 0.8≤b≤0.92, 0.04≤c≤0.12, 0.05≤d≤0.15, and 0.001≤e≤0.005. More alternatively, 0.8≤b≤0.86, 0.04≤c≤0.09, 0.09≤d≤0.12, and 0.002≤e≤0.005.

[0078] In some implementations, the cathode material satisfies one or more of the following characteristics:

[0079] (1) 2μm≤Dv2≤4μm, where, for example, Dv2 is a value within a range of 2μm, 2.2μm, 2.4μm, 2.5μm, 2.6μm, 2.8μm, 3μm, 4μm, or any two of these; (2) 3μm≤Dv10≤7μm, where, for example, Dv10 is a value within a range of 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 6μm, 7μm, or any two of these; (3) 7μm≤Dv50≤13μm, where, for example, Dv50 is 7μm. (3) Values ​​between the ranges of 7.5μm, 8μm, 8.5m, 9μm, 9.5μm, 10μm, 11μm, 12μm, 13μm, or any two of these; (4) 16μm≤Dv90≤24μm, where, for example, Dv90 is a value between the ranges of 16μm, 20μm, 24μm, or any two of these; (5) 20μm≤Dv99≤35μm, where, for example, Dv99 is a value between the ranges of 10μm, 20μm, 30μm, 35μm, or any two of these. Dv99 reflects the maximum value of the cathode material particle size, Dv50 reflects the overall level of the cathode material particle size, Dv2 reflects the minimum value of the cathode material particle size, Dv10 reflects the smaller value of the cathode material particle size, and Dv90 reflects the larger value of the cathode material particle size. The volume distribution particle size of the cathode material is within the above range, which reflects that most of the particles of the cathode material have a small particle size. On the one hand, this is beneficial to improving the specific capacity of the cathode material. On the other hand, smaller particles have less volume change during cycling, which is beneficial to the cathode material having good structural stability, thereby improving the cycle performance of the secondary battery.

[0080] In this disclosure, the volume distribution particle sizes Dv2, Dv10, Dv50, Dv90, and Dv99 of the cathode material represent the particle sizes corresponding to a cumulative volume distribution percentage of 2%, 10%, 50%, 90%, and 99%, respectively, and can be determined using instruments and methods known in the art. For example, they can be determined using a laser particle size analyzer, referring to standard GB / T 19077-2016. The testing instrument can be a Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.

[0081] In some embodiments, the tap density of the cathode material is 2.4 g / cm³. 3 ~3.0g / cm 3 For example, the tap density of the positive electrode material is 2.4 g / cm³. 3 2.5g / cm 3 2.6g / cm 3 2.7g / cm 3 2.8g / cm 3 2.9g / cm 3 3.0g / cm 3 Or the values ​​within the range formed by any two of these values. A tap density of the cathode material within the above range is beneficial for improving the compactness of the cathode material, making the contact between secondary particles closer, thereby improving the compaction density of the cathode material, and consequently, improving the energy density of the battery.

[0082] In this disclosure, the tap density of the material has a meaning known in the art and can be determined using instruments and methods known in the art. For example, it can be determined using a powder tap density tester according to GB / T 5162-2006. The testing instrument can be Dandong Baite BT-301, with the following test parameters: vibration frequency 250±15 times / minute, amplitude 3±0.2mm, number of vibrations 5000 times, and a measuring cylinder of 25mL.

[0083] The term "secondary battery" used in this article refers to a single battery cell, a battery module, or a battery pack. These will be explained separately below.

[0084] Typically, a battery cell includes a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0085] Negative electrode sheet

[0086] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0087] As an example, the negative electrode current collector has two surfaces opposite each other in its own 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.

[0088] 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 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.).

[0089] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this disclosure 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.

[0090] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from at least one 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).

[0091] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0092] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0093] 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 (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0094] Positive electrode sheet

[0095] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including the positive electrode material of this disclosure.

[0096] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector. In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (aluminum, aluminum 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.).

[0097] During the charging and discharging process of a battery, Li undergoes insertion / extraction and consumption, resulting in varying molar Li content at different discharge states. In the examples of positive electrode active materials in this disclosure, the molar Li content refers to the initial state of the material, i.e., the state before feeding. When the positive electrode active material is applied to the battery system, the molar Li content changes after charge-discharge cycles.

[0098] In the examples of positive electrode active materials in this disclosure, the molar content of O is only a theoretical value. Oxygen release from the crystal lattice will cause changes in the molar content of oxygen, and the actual molar content of O will fluctuate.

[0099] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0100] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0101] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0102] electrolytes

[0103] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This disclosure does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel-like, or entirely solid.

[0104] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0105] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0106] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0107] 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.

[0108] Separating membrane

[0109] In some embodiments, the battery cell also includes a separator. This disclosure does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0110] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0111] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0112] In some embodiments, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0113] In some embodiments, the outer packaging of the battery cell can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the battery cell can also be a flexible package, such as a pouch. The material of the flexible package can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0114] This disclosure does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 shows a square battery cell 5 as an example.

[0115] In some embodiments, referring to FIG2, the outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be placed over the opening to close the receiving cavity. The positive electrode sheet, negative electrode sheet, and separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 may be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0116] In some implementations, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0117] Figure 3 shows a battery module 4 as an example. Referring to Figure 3, in the battery module 4, multiple battery cells 5 can be arranged sequentially along the length of the battery module 4. Of course, they can also be arranged in any other manner. Furthermore, the multiple battery cells 5 can be fixed in place using fasteners.

[0118] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0119] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0120] Figures 4 and 5 show a battery pack 1 as an example. Referring to Figures 4 and 5, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper box 2 and a lower box 3, with the upper box 2 covering the lower box 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0121] Electrical appliances

[0122] This disclosure also provides an electrical device, which includes the secondary battery provided in the first aspect of this disclosure. The secondary battery may include at least one of a battery cell, a battery module, or a battery pack. The secondary 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 (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0123] As an electrical device, you can choose individual battery cells, battery modules, or battery packs according to your usage requirements.

[0124] Figure 6 shows an example of an electrical device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0125] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0126] cathode materials

[0127] The third aspect of this disclosure provides a cathode material comprising a lithium transition metal oxide, the lithium transition metal oxide comprising secondary particles formed by a plurality of primary particles with a particle size of 0.2 μm to 1 μm; the lithium transition metal oxide comprising nickel, cobalt, and manganese, wherein, based on the total molar number of nickel, cobalt, and manganese, the molar percentage of nickel is greater than or equal to 50% and less than 100%, and the molar content of manganese is greater than or equal to the molar content of cobalt; the lithium transition metal oxide further comprises a modifying element, which is one or more of zirconium, yttrium, sodium, potassium, phosphorus, antimony, aluminum, titanium, boron, tungsten, and carbon; and, at 100% SOC, the oxygen release temperature of the cathode material, as determined by thermogravimetric-mass spectrometry, is 210℃ to 230℃.

[0128] In this disclosure, since the lithium transition metal oxide includes secondary particles formed from primary particles with a particle size of 0.2 μm to 1 μm, the structure of the secondary particles is relatively stable. This reduces microcracks and particle shedding caused by volume changes during charging and discharging, thus improving the cycle stability of the lithium-ion secondary battery. Furthermore, by setting the Mn content in the lithium transition metal oxide to be greater than or equal to the Co content and by modifying the cathode material with modifying elements, the thermal stability of the cathode material is improved, thereby enhancing the cycle and safety performance of the lithium-ion secondary battery. In addition, since the cathode material is in its most active state when the cathode is fully charged, its thermal stability in the secondary battery can be better evaluated at this time. Therefore, by ensuring that the oxygen release temperature measured by thermogravimetric-mass spectrometry (TGA) of the cathode in a fully charged state is within the aforementioned range, this disclosure further reflects the good thermal stability of the cathode material, which is beneficial to the cycle performance and safety performance of the lithium-ion secondary battery.

[0129] In some embodiments, at 100% SOC, the oxygen release temperature of the positive electrode sheet was 215℃~230℃ in thermogravimetric-mass spectrometry (TGA) tests. This further reflects the good thermal stability of the positive electrode material, which is beneficial to the cycle performance and safety performance of lithium-ion secondary batteries.

[0130] In some embodiments, at 100% SOC, the peak decomposition temperature of the cathode material measured by thermogravimetric-mass spectrometry (TGA-MS) is 215°C to 235°C. In this disclosure, the peak decomposition temperature of the cathode material measured by TGA-MS under full charge is within the above range, indicating a relatively low peak decomposition temperature. This further reflects the good thermal stability of the cathode material, which is beneficial to the cycle performance and safety performance of lithium-ion secondary batteries.

[0131] In some embodiments, at 100% SOC, the oxygen release of the cathode material measured by thermogravimetric-mass spectrometry (TGA-MS) is 80 μL / mg to 115 μL / mg. The oxygen release of the cathode material in this disclosure, measured by TGA-MS under full charge, falls within the above range, indicating a low oxygen release. This further reflects the good thermal stability of the cathode material, which is beneficial to the cycle performance and safety of lithium-ion secondary batteries.

[0132] In some embodiments, based on the total molar number of nickel, cobalt, and manganese, the molar content of manganese is M1, the molar content of cobalt is M2, and 0 ≤ M1 - M2 ≤ 8%. By controlling M1-M2 within the above range, the manganese content in the cathode material is further increased, which is beneficial to further improving the stability of the cathode material, thereby improving the cycle performance and safety performance of the lithium-ion secondary battery.

[0133] In some embodiments, the molar content of manganese in the lithium transition metal oxide is 4% to 13% based on the total molar number of nickel, cobalt, and manganese; optionally, it is 6% to 10%. By controlling the molar content of manganese in the lithium transition metal oxide within the above range, it is beneficial to improve the thermal stability of the cathode material, thereby improving the cycle and safety performance of the lithium-ion secondary battery. On the other hand, it reduces the content of cobalt in the lithium transition metal oxide, which helps to reduce costs.

[0134] In some embodiments, the molar content of cobalt in the lithium transition metal oxide is 4% to 10% based on the total molar number of nickel, cobalt, and manganese. Optionally, the molar content of cobalt is 6% to 9%. By keeping the molar content of cobalt in the lithium transition metal oxide within the above range, costs can be reduced while ensuring the conductivity of the cathode material, which is beneficial to the electrical performance of the secondary battery.

[0135] In some embodiments, the content of the modifying element is less than or equal to 1% based on the total mass of the lithium transition metal oxide. This is beneficial for improving the structural stability of the cathode material, increasing the oxygen vacancy formation energy, and improving the material's safety performance.

[0136] In some embodiments, the zirconium, yttrium, sodium, potassium, phosphorus, and antimony elements in the modified elements are uniformly distributed in the bulk phase of the lithium transition metal oxide. By ensuring uniform distribution of the modified elements in the bulk phase of the lithium transition metal oxide, the phase transition suppression effects of zirconium, yttrium, sodium, potassium, phosphorus, and antimony are enhanced, thereby improving the stability of the cathode material and ultimately improving the safety performance of the secondary battery.

[0137] In some embodiments, the aluminum, titanium, boron, tungsten, and carbon elements in the modification are distributed on the surface of the lithium transition metal oxide. This allows the aluminum, titanium, boron, tungsten, and carbon elements to isolate side reactions between the lithium transition metal and the electrolyte, thereby improving the stability of the cathode material and reducing lithium-ion consumption during cycling, thus enhancing the cycle stability of the lithium-ion secondary battery. In some embodiments, the modification elements include aluminum and / or zirconium.

[0138] In some embodiments, the molar percentage of nickel is 80% to 92% based on the total molar number of nickel, cobalt, and manganese; alternatively, it is 80% to 86%. Therefore, a higher nickel content in the cathode material is beneficial for improving the energy density of the secondary battery.

[0139] In some embodiments, the chemical formula of the lithium transition metal oxide includes: Li a Ni b Co c Mn d N e O f N includes one or more of Zr, Y, Na, K, P, Sb, Al, Ti, B, W, and C, with 0.8≤a≤1.1, 0.5≤b<1, 0.04≤c<1, 0.05≤d<1, c<d, 0.001≤e<1, 1.8≤f≤2.2, b+c+d+e=1. Optionally, 0.8≤b≤0.92, 0.04≤c≤0.12, 0.05≤d≤0.15, 0.001≤e≤0.005. More alternatively, 0.8≤b≤0.86, 0.04≤c≤0.09, 0.09≤d≤0.12, 0.002≤e≤0.005.

[0140] In some implementations, the volumetric particle size Dv2 of the cathode material satisfies: 2μm≤Dv2≤4μm.

[0141] In some implementations, the volumetric particle size Dv10 of the cathode material satisfies: 3μm≤Dv10≤7μm.

[0142] In some implementations, the cathode material satisfies one or more of the following characteristics:

[0143] (1) 2μm≤Dv2≤4μm; (2) 3μm≤Dv10≤7μm; (3) 7μm≤Dv50≤13μm; (4) 16μm≤Dv90≤24μm; (5) 20μm≤Dv99≤35μm. This improves the specific capacity and cycle performance of the cathode material.

[0144] In some embodiments, the tap density of the cathode material is 2.4 g / cm³.3 ~3.0g / cm 3 This is beneficial for improving the energy density of secondary batteries.

[0145] In some embodiments, the above-mentioned cathode material can be prepared, for example, by the following steps: S1, preparing a nickel-cobalt-manganese precursor; the chemical formula of the nickel-cobalt-manganese precursor includes: Ni b Co c Mn d (OH)2, wherein 0.5≤b<1, 0.04≤c<1, 0.05≤d<1, c<d, optionally, 0.8≤b≤0.92, 0.04≤c≤0.12, 0.05≤d≤0.15, more preferably, 0.8≤b≤0.86, 0.04≤c≤0.09, 0.09≤d≤0.12; the volumetric particle size distribution Dv50 of the nickel-cobalt-manganese precursor is 8μm~16μm; S2, the nickel-cobalt-manganese precursor, lithium source, and first doping source are mixed evenly and then subjected to a first sintering treatment to obtain an intermediate product; S3, the intermediate product obtained in step S2 is washed with deionized water for 3min~8min and then centrifuged and dried to obtain a lithium transition metal oxide; S4, the washed lithium transition metal oxide is mixed evenly with a second doping source and then subjected to a second sintering treatment to obtain a cathode material. The oxygen release temperature of the prepared cathode material, as determined by thermogravimetric-mass spectrometry at 100% SOC, ranged from 210℃ to 230℃.

[0146] In the method disclosed herein, by controlling the molar ratio of nickel, cobalt, and manganese sources in step S1, the Mn content in the prepared lithium transition metal oxide is greater than or equal to the Co content. Furthermore, by introducing modifying elements in steps S2 and S4, the oxygen release temperature of the prepared cathode material, as measured by thermogravimetric-mass spectrometry at 100% SOC, is 210℃–230℃. This improves the thermal stability of the lithium transition metal oxide, thereby enhancing the cycle life and safety performance of lithium-ion secondary batteries.

[0147] In some embodiments, step S2 includes one or more of the following features: (1) the first modification source includes one or more of zirconium source, yttrium source, sodium source, potassium source, phosphorus source, and antimony source; (2) the molar ratio of nickel cobalt manganese precursor, lithium source, and first modification source is 1:(1.0~1.1):(0.001%~0.1%); (3) the first sintering treatment is carried out at 750℃~850℃ for 15h~25h with oxygen as the carrier gas.

[0148] In some embodiments, the lithium source includes one or more of lithium hydroxide, lithium carbonate, lithium sulfate, lithium nitrate, lithium oxide, lithium phosphate, lithium oxalate, lithium acetate, and lithium peroxide, and optionally, lithium hydroxide.

[0149] In some embodiments, since a lot of residual alkali remains at the grain boundaries of the intermediate product, a water washing step S3 is needed to remove the residual alkali in order to improve the capacity of the final lithium transition metal oxide. The role of lithium hydroxide in step S3 is to adjust the pH of the cathode material during the water washing process. Because high-nickel materials are strongly alkaline, if they come into direct contact with deionized water during the water washing process, the pH value of the high-nickel material will drop significantly, causing a large amount of lithium ions to be released. Therefore, lithium hydroxide is usually added during the water washing process to maintain the pH of the high-nickel material.

[0150] In some embodiments, step S4 includes one or more of the following features: (1) the second modification source includes one or more of aluminum, titanium, boron, tungsten, and carbon sources; (2) the molar ratio of the intermediate product to the second modification source is greater than 0 and less than or equal to 1000; (3) the second sintering treatment is carried out at 300°C to 500°C for 10 to 20 hours with oxygen as the carrier gas.

[0151] In some embodiments, the preparation process of the precursor in step S1 includes: mixing a nickel source, a cobalt source and a manganese source to form a metal salt solution, adding a precipitant and / or a complexing agent to the metal salt solution, controlling the pH value of the solution and the reaction temperature to carry out a co-precipitation reaction, and obtaining the precursor.

[0152] In some embodiments, the coprecipitation reaction satisfies one or more of the following characteristics: (1) the reaction temperature is 60℃~70℃; (2) the reaction time is 30h~35h; (3) the reaction pH is 10~11; (4) the concentration of the complexing agent is 4g / L~6g / L.

[0153] In some embodiments, the precipitant includes one or more of sodium hydroxide, sodium carbonate, potassium hydroxide, and lithium hydroxide, and optionally, sodium hydroxide.

[0154] In some embodiments, the complexing agent includes one or more of ammonia, ammonium chloride, ammonium sulfate, urea, citric acid, and ethylenediaminetetraacetic acid (EDTA), optionally ammonia.

[0155] Example

[0156] The following describes embodiments of this disclosure. The embodiments described below are exemplary and are only used to explain this disclosure, and should not be construed as limiting this disclosure. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0157] Example 1

[0158] Preparation of cathode materials:

[0159] S1, nickel sulfate, cobalt sulfate, and manganese sulfate were mixed in a molar ratio of 0.82:0.08:0.10 to prepare a metal salt solution. Under a nitrogen atmosphere, sodium hydroxide solution was added to adjust the pH of the first metal salt solution to 10.5. Then, 5 g / L ammonia water was added as the first precipitant. The reaction was carried out at 60°C for 35 h to prepare the precursor seed crystal Ni. 0.82 Co 0.08 Mn 0.10 (OH)2, the volume distribution particle size Dv50 of the precursor seed crystals is 3μm;

[0160] The aforementioned precursor seed crystals were added to a reaction vessel, maintaining a constant molar ratio of nickel sulfate, cobalt manganese sulfate, and manganese sulfate, and a pH of 10.5. 5 g / L ammonia was added, and the reaction was carried out at 200 rpm and 60°C for 48 h to prepare the nickel-cobalt-manganese precursor Ni. 0.82 Co 0.08 Mn 0.10 (OH)2, Ni, a nickel-cobalt-manganese precursor 0.82 Co 0.08 Mn 0.10 The Dv50 of (OH)2 is 11 μm.

[0161] S2, the above nickel-cobalt-manganese precursor Ni 0.82 Co 0.08 Mn 0.10 (OH)2, lithium source LiOH·H2O, and first modified source ZrO2 are mixed in a molar ratio of 1:1.02:0.01%, and then reacted at 800℃ under pure oxygen conditions for 15 h to obtain an intermediate product;

[0162] S3. The intermediate product and deionized water were mixed evenly at a mass ratio of 1:1, reacted for 5 minutes, and then centrifuged and dried to obtain lithium transition metal oxide, which was used as the cathode material. In the cathode material, based on the total molar number of nickel, cobalt, and manganese, the molar content of manganese, M1, was 10%, and the molar content of cobalt, M2, was 8%.

[0163] Cathode material parameter testing:

[0164] (1) Scanning electron microscopy (SEM) test

[0165] The cathode material was tested using SEM to obtain its microstructure.

[0166] Figure 7 is a scanning electron microscope image of the cathode material in Example 1. As shown in Figure 7, the cathode material includes multiple secondary particles formed by primary particles with a particle size of 0.3 μm to 0.9 μm. The secondary particles are spherical in shape.

[0167] (2) Thermogravimetric-mass spectrometry (TGA) test

[0168] Approximately 50 mg of the positive electrode material was weighed into a high-footed Al₂O₃ crucible, leveled, and placed in a STA (Simultaneous Thermal Analyzer) for heating under an argon atmosphere to decompose and release oxygen. The purge gas flow rate was set to 50 mL / min, the protective gas flow rate to 20 mL / min, the heating rate to 10 °C / min, and the temperature range to 35 °C–1400 °C. Thermogravimetric curves were obtained. After the oxygen entered a QMS (quadrupole mass spectrometer), an MS curve with an ion concentration of 32 was obtained.

[0169] Figure 8 shows the thermogravimetric-mass spectrometry test curve of the positive electrode in Example 1. As shown in Figure 8, the oxygen release temperature of the positive electrode material in Example 1 was measured to be 220℃, and the peak oxygen release temperature was 228℃.

[0170] In addition, according to the formula of oxygen release amount = (peak area of ​​oxygen release peak / standard peak area) * standard oxygen volume / sample mass, the oxygen release amount of the cathode material in Example 1 was calculated to be 98 μL / mg.

[0171] (3) Modified element content test

[0172] The cathode material in Example 1 was tested by inductively coupled plasma atomic emission spectrometry (ICP). The ICP test results showed that the Zr content in the cathode material of Example 1 was 0.5%.

[0173] (4) Lithium-nickel mixing rate test

[0174] The cathode material from Example 1 was placed in a sample well with a depth of 0.5 mm and a diameter of 25 mm, and the sample was prepared using a flat plate. A copper target was selected, and the test parameters were 10° to 80°, with a scanning speed of 1° / min to process the material and obtain its X-ray diffraction (XRD) pattern.

[0175] Figure 9 shows the XRD pattern of the positive electrode in Example 1. The lithium-nickel mixing ratio of the positive electrode material in Example 1 was found to be 2.2% by GSAS / Fullprof fine fitting.

[0176] (5) Volume distribution particle size test

[0177] The volumetric particle size distribution of the cathode material was tested using a Malvern 3000 (MasterSizer 3000) laser particle size analyzer, following the standard procedure GB / T19077-2016 / ISO 13320:2009. The test results showed that the volumetric particle size distribution of the cathode material in Example 1 was 3.1 μm for Dv2, 5.5 μm for Dv10, 10.9 μm for Dv50, 22 μm for Dv90, and 32 μm for Dv99.

[0178] (6) Tap density test

[0179] Using a Dandong BT-300 measuring cylinder and a 25ml graduated cylinder, the positive electrode material was filled to 20ml. The cylinder was then vibrated 5000 times at a frequency of 250 times / min to measure the tap density of the positive electrode material. In Example 1, the tap density of the positive electrode material was 2.8 g / cm³. 3 .

[0180] Preparation of lithium-ion secondary batteries:

[0181] (1) Preparation of the positive electrode sheet:

[0182] The above-prepared positive electrode material, binder polyvinylidene fluoride, conductive agent conductive carbon, and dispersant sodium carboxymethyl cellulose are mixed in a weight ratio of 95:1.5:2.5:1 and then added to the solvent N-methylpyrrolidone. The mixture is stirred evenly to form a positive electrode slurry. The positive electrode slurry is coated onto the positive electrode current collector aluminum foil to form a positive electrode film layer. After drying and cold pressing, a positive electrode sheet is obtained.

[0183] (2) Preparation of negative electrode sheet:

[0184] The negative electrode material, binder styrene-polybutadiene rubber, conductive agent conductive carbon black, and dispersant sodium carboxymethyl cellulose are dispersed in an appropriate amount of deionized water at a weight ratio of 95:2:0.5:2.5 and thoroughly mixed to form a negative electrode slurry. This slurry is then coated onto a copper foil current collector to form a negative electrode film. After drying and cold pressing, the negative electrode sheet is obtained. The negative electrode material comprises a graphite and silicon-carbon composite material with a mass ratio of 95:5; in the silicon-carbon composite material, silicon accounts for 5% of the total mass relative to the mass of the silicon-carbon composite material.

[0185] (3) Preparation of electrolyte:

[0186] An organic solvent is formed by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7. LiPF6 is then dissolved in the organic solvent to obtain an electrolyte with a LiPF6 concentration of 1 mol / L.

[0187] (4) Separating membrane:

[0188] A polyethylene base film with a thickness of 7 μm is used. Both sides of the base film are coated with a boehmite coating membrane with a single-sided thickness of 2 μm and a polymer coating with a single-sided thickness of 2 μm. The boehmite coating is located between the polymer coating and the base film. The thickness of the separator membrane is 15 μm.

[0189] (5) Preparation of lithium-ion secondary batteries:

[0190] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide insulation. The electrode assembly is then formed by bending and winding. The electrode assembly is placed in outer packaging, dried, and then injected with the prepared electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion secondary battery is obtained.

[0191] Lithium-ion secondary battery performance testing:

[0192] (1) Cyclic performance test

[0193] ① Let stand for 5 minutes;

[0194] ② Charge at a constant current of 1 / 3C to 4.25V, then charge at a constant voltage of 4.25V to a current of 0.05C;

[0195] ③ Let stand for 5 minutes;

[0196] ④ Discharge at a constant current of 1 / 3C to 2.8V, and record the discharge capacity D1 of the first cycle;

[0197] ⑤ Repeat steps ① to ④ above 400 times, and record the discharge capacity Dn on the 400th cycle;

[0198] 400-cycle capacity retention rate (%) = discharge capacity Dn of the 400th cycle / discharge capacity D1 of the first cycle * 100%. The test results are shown in Table 2.

[0199] (2) Safety performance test

[0200] ① Let stand for 5 minutes;

[0201] ② Charge at a constant current of 1 / 3C to 4.25V, then charge at a constant voltage of 4.25V to a current of 0.05C;

[0202] ③ Heat the secondary battery to 55℃ and maintain it for 2 hours; increase the temperature at a rate of 5℃ / min, and maintain it for 30 minutes for every 5℃ increase, until the secondary battery runs out of control. Record the temperature at which the secondary battery runs out of control. The higher the temperature, the better the safety performance of the secondary battery.

[0203] Examples 2 to 6

[0204] The lithium-ion secondary battery was prepared using the same method as in Example 1, except that the molar amount and type of the first modification source added in step S2 were adjusted so that the type and content of the modifying elements in the cathode material were adjusted according to Table 1 below.

[0205] Comparative Example 1

[0206] The lithium-ion secondary battery was prepared using the same method as in Example 1, except that the molar ratio of the metal salt solution in step S1 was adjusted to 82:12:6 for nickel sulfate:cobalt sulfate:manganese sulfate, so that in the prepared cathode material, the molar content of manganese was less than the molar content of cobalt based on the total molar number of nickel, cobalt, and manganese. In addition, the first modification source in step S2 was adjusted to NaOH.

[0207] Comparative Example 2

[0208] The lithium-ion secondary battery was prepared using the same method as in Example 1, except that the first modification source in step S2 was changed to SiO2.

[0209] Comparative Example 3

[0210] The lithium-ion secondary battery was prepared using the same method as in Example 1, except that the molar ratio of the metal salt solution in step S1 was adjusted to 82:12:6 for nickel sulfate:cobalt sulfate:manganese sulfate, so that in the prepared cathode material, the molar content of manganese was less than that of cobalt based on the total molar number of nickel, cobalt, and manganese. In addition, the molar amount and type of the first modification source added in step S2 were adjusted so that the types and contents of the modification elements in the cathode material were adjusted according to Table 1 below.

[0211] Table 1 below shows the relevant parameters of the cathode materials prepared in Examples 1 to 6 and Comparative Examples 1 to 3. Table 2 below shows the performance test results of the lithium-ion secondary batteries prepared in Examples 1 to 6 and Comparative Examples 1 to 3.

[0212] Table 1

[0213] Table 2

[0214] As can be seen from Tables 1 and 2, in Examples 1-6, by setting the Mn content in the lithium transition metal oxide to be greater than the Co content and including the modified elements, the oxygen release temperature of the positive electrode sheet was 210℃~230℃ in thermogravimetric-mass spectrometry tests at 100% SOC. The prepared lithium-ion secondary batteries achieved both good cycle stability and safety performance. In contrast, in Comparative Example 1, the Mn content in the lithium transition metal oxide was less than the Co content, resulting in a lithium-ion secondary battery with better cycle performance but poor safety performance. In Comparative Examples 2 and 3, the lithium transition metal oxides did not include the modified elements disclosed herein, and in Comparative Example 3, the Co content in the lithium transition metal oxide was greater than the Mn content; therefore, the capacity retention and safety performance of the prepared lithium-ion secondary batteries were both poor.

[0215] Example 7

[0216] The lithium-ion secondary battery was prepared using the same method as in Example 1, except that after step S3, step S4 was further included: mixing the above-washed lithium transition metal oxide with the second modified source Al2O3 at a molar ratio of 1:0.00006, and then performing a second sintering treatment to obtain the positive electrode material. The second sintering treatment was carried out at 400°C for 15 hours with oxygen as the carrier gas.

[0217] Example 8

[0218] The lithium-ion secondary battery was prepared using the same method as in Example 1, except that the first modifying source was not added in step S2, and the process after step S3 included: S4, mixing the above-washed lithium transition metal oxide with the second modifying source Al2O3 at a molar ratio of 1:0.00006, and then performing a second sintering treatment to obtain the positive electrode material. The second sintering treatment was carried out at 400°C for 15 hours with oxygen as the carrier gas.

[0219] Examples 9-12

[0220] The lithium-ion secondary battery was prepared using the same method as in Example 8, except that the types of modifying elements were adjusted according to Table 3 below.

[0221] The cathode materials and lithium-ion secondary batteries prepared in Examples 7 to 12 were tested using the same test method as in Example 1. The test results are recorded in Tables 3 and 4 below.

[0222] Table 3 below shows the relevant parameters of the cathode materials prepared in Examples 7 to 12, and Table 4 below shows the performance test results of the lithium-ion secondary batteries prepared in Examples 7 to 13.

[0223] Table 3

[0224] Table 4

[0225] As can be seen from Tables 3 and 4, in Examples 7-12, by setting the Mn content in the lithium transition metal oxide to be greater than the Co content and including the modified elements disclosed herein, the oxygen release temperature of the positive electrode sheet was 210℃~230℃ in the thermogravimetric-mass spectrometry test results at 100% SOC. The prepared lithium-ion secondary battery can achieve both good cycle stability and safety performance.

[0226] Examples 13-15

[0227] The lithium-ion secondary battery was prepared using the same method as in Example 1, except that the molar ratio of nickel sulfate, cobalt sulfate, and manganese sulfate in the metal salt solution in step S1 was adjusted so that the molar content of manganese M1 and the molar content of cobalt M2 in the final prepared cathode material were adjusted according to Table 5 below, based on the total number of moles of nickel, cobalt, and manganese.

[0228] The cathode materials and lithium-ion secondary batteries prepared in Examples 13 to 15 were tested using the same test method as in Example 1, and the test results are recorded in Tables 5 and 6 below.

[0229] Table 5 below shows the relevant parameters of the cathode materials prepared in Examples 13 to 15, and Table 6 below shows the performance test results of the lithium-ion secondary batteries prepared in Examples 13 to 15.

[0230] Table 5

[0231] Table 6

[0232] As can be seen from Tables 5 and 6, by setting the content of Mn element M1 and the content of Co element M2 in the lithium transition metal oxide to satisfy: 0≤M1-M2≤8%, the prepared lithium-ion secondary batteries can achieve both good cycle capacity retention and safety performance.

[0233] It should be noted that this disclosure is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same essential structure and achieving the same effect as the technical concept within the scope of this disclosure are included in the technical scope of this disclosure. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, are also included in the scope of this disclosure without departing from the spirit of this disclosure.

Claims

1. A lithium-ion secondary battery, comprising a positive electrode sheet, the positive electrode sheet including a positive current collector and a positive electrode film layer located on at least one side of the positive current collector and comprising a positive electrode material. The cathode material includes a lithium transition metal oxide, which comprises secondary particles formed by a plurality of primary particles with a particle size of 0.2 μm to 1 μm. The lithium transition metal oxide comprises nickel, cobalt, and manganese. Based on the total molar number of nickel, cobalt, and manganese, the molar percentage of nickel is greater than or equal to 50% and less than 100%, and the molar percentage of manganese is greater than or equal to the molar percentage of cobalt. The lithium transition metal oxide further includes a modifying element, which is one or more of zirconium, yttrium, sodium, potassium, phosphorus, antimony, aluminum, titanium, boron, tungsten, and carbon. At 100% SOC, the oxygen release temperature of the positive electrode sheet was 210℃~230℃ according to the thermogravimetric-mass spectrometry test results.

2. The lithium-ion secondary battery according to claim 1, wherein, At 100% SOC, the oxygen release temperature of the positive electrode sheet was 215℃~230℃ according to the thermogravimetric-mass spectrometry test results.

3. The lithium-ion secondary battery according to claim 1 or 2, wherein, At 100% SOC, the peak decomposition temperature of the positive electrode sheet was 215℃~235℃ in the thermogravimetric-mass spectrometry test results.

4. The lithium-ion secondary battery according to any one of claims 1 to 3, wherein, At 100% SOC, the oxygen release of the positive electrode sheet was 80 μL / mg to 115 μL / mg according to thermogravimetric-mass spectrometry (TGA) tests.

5. The lithium-ion secondary battery according to any one of claims 1 to 4, wherein, Based on the total number of moles of nickel, cobalt, and manganese, the molar content of manganese is M1, the molar content of cobalt is M2, and 0 ≤ M1 - M2 ≤ 8%.

6. The lithium-ion secondary battery according to any one of claims 1 to 5, wherein, In the lithium transition metal oxide, the molar content of manganese is 4% to 13% based on the total molar number of nickel, cobalt, and manganese.

7. The lithium-ion secondary battery according to any one of claims 1 to 6, wherein, In the lithium transition metal oxide, the molar content of cobalt is 4% to 10% based on the total molar number of nickel, cobalt, and manganese.

8. The lithium-ion secondary battery according to any one of claims 1 to 7, wherein, Based on the total mass of the lithium transition metal oxide, the content of the modifying element is less than or equal to 1%.

9. The lithium-ion secondary battery according to any one of claims 1 to 8, wherein, The zirconium, yttrium, sodium, potassium, phosphorus, and antimony elements in the modified elements are uniformly distributed in the bulk phase of the lithium transition metal oxide.

10. The lithium-ion secondary battery according to any one of claims 1 to 9, wherein, The modified elements, aluminum, titanium, boron, tungsten, and carbon, are distributed on the surface of the lithium transition metal oxide.

11. The lithium-ion secondary battery according to any one of claims 1 to 10, wherein, The modifying elements include aluminum and / or zirconium.

12. The lithium-ion secondary battery according to any one of claims 1 to 11, wherein, The lithium-nickel mixing rate of the cathode material is 2% to 3%.

13. The lithium-ion secondary battery according to any one of claims 1 to 12, wherein, Based on the total molar number of nickel, cobalt, and manganese, the molar percentage of nickel is 80% to 92%.

14. The lithium-ion secondary battery according to any one of claims 1 to 13, wherein, The cathode material satisfies one or more of the following characteristics: (1) 2μm≤Dv2≤4μm; (2) 3μm≤Dv10≤7μm; (3) 7μm≤Dv50≤13μm; (4) 16μm≤Dv90≤24μm; (5) 20μm≤Dv99≤35μm.

15. The lithium-ion secondary battery according to any one of claims 1 to 14, wherein, The tap density of the positive electrode material is 2.4 g / cm³. 3 ~3.0g / cm 3 .

16. An electrical device comprising a lithium-ion secondary battery as claimed in any one of claims 1 to 15.

17. A cathode material comprising a lithium transition metal oxide, wherein the lithium transition metal oxide comprises secondary particles formed by a plurality of primary particles having a particle size of 0.2 μm to 1 μm; The lithium transition metal oxide comprises nickel, cobalt, and manganese. Based on the total molar number of nickel, cobalt, and manganese, the molar percentage of nickel is greater than or equal to 50% and less than 100%, and the molar percentage of manganese is greater than or equal to the molar percentage of cobalt. The lithium transition metal oxide further includes a modifying element, which is one or more of zirconium, yttrium, sodium, potassium, phosphorus, antimony, aluminum, titanium, boron, tungsten, and carbon. The oxygen release temperature of the cathode material was found to be 210℃~230℃ in thermogravimetric-mass spectrometry tests at 100% SOC.

18. The cathode material according to claim 17, wherein, At 100% SOC, the oxygen release temperature of the cathode material, as determined by thermogravimetric-mass spectrometry, is 215℃~230℃.

19. The cathode material according to claim 17 or 18, wherein, At 100% SOC, the peak decomposition temperature of the cathode material, as determined by thermogravimetric-mass spectrometry (TGA), is 215℃~235℃.

20. The cathode material of any one of claims 17-19, wherein, At 100% SOC, the oxygen release of the cathode material, as determined by thermogravimetric-mass spectrometry, ranged from 80 μL / mg to 115 μL / mg.

21. The cathode material according to any one of claims 17 to 20, wherein, Based on the total number of moles of nickel, cobalt, and manganese, the molar content of manganese is M1, the molar content of cobalt is M2, and 0 ≤ M1 - M2 ≤ 8%.

22. The cathode material according to any one of claims 17 to 21, wherein, In the lithium transition metal oxide, the molar content of manganese is 4% to 13% based on the total molar number of nickel, cobalt, and manganese.

23. The cathode material according to any one of claims 17 to 22, wherein, In the lithium transition metal oxide, the molar content of cobalt is 4% to 10% based on the total molar number of nickel, cobalt, and manganese.

24. The cathode material according to any one of claims 17 to 23, wherein, Based on the total mass of the lithium transition metal oxide, the content of the modifying element is less than or equal to 1%.

25. The cathode material according to any one of claims 17 to 24, wherein, The zirconium, yttrium, sodium, potassium, phosphorus, and antimony elements in the modified elements are uniformly distributed in the bulk phase of the lithium transition metal oxide.

26. The cathode material according to any one of claims 17 to 25, wherein, The modified elements, aluminum, titanium, boron, tungsten, and carbon, are distributed on the surface of the lithium transition metal oxide.

27. The cathode material according to any one of claims 17 to 26, wherein, The modifying elements include aluminum and / or zirconium.

28. The cathode material according to any one of claims 17 to 27, wherein, The lithium-nickel mixing rate of the cathode material is 2% to 3%.

29. The cathode material according to any one of claims 17 to 28, wherein, Based on the total molar number of nickel, cobalt, and manganese, the molar percentage of nickel is 80% to 92%.

30. The cathode material according to any one of claims 17 to 29, wherein, The cathode material satisfies one or more of the following characteristics: (1) 2μm≤Dv2≤4μm; (2) 3μm≤Dv10≤7μm; (3) 7μm≤Dv50≤13μm; (4) 16μm≤Dv90≤24μm; (5) 20μm≤Dv99≤35μm.

31. The cathode material according to any one of claims 17 to 30, wherein, The tap density of the positive electrode material is 2.4 g / cm³. 3 ~3.0g / cm 3 .

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