Positive electrode active material, method for preparing the same, positive electrode sheet comprising the same, battery, and electric device

Abstract

This application provides a positive electrode active material and its preparation method, a positive electrode sheet containing the same, a battery, and a power device. The positive electrode active material includes ternary positive electrode material particles with a core-shell structure, the ternary positive electrode material particles containing the dopant element M. 1 and dopant element M 2 Furthermore, based on the total molar amount of transition metal elements in the ternary cathode material particles, the molar percentage of Ni element in the ternary cathode material particles is greater than or equal to 0.6; wherein, M 1 ionic radius r M1 With lithium ion radius r Li Satisfy: |r M1 -r Li |≤80pm, and M 1 Distributed in the core of the ternary cathode material particles; M 2 Including one or more of Zr, Nb, Ta, W, Mo, Ti, and Ir, and M 2 Distributed in the shell of the ternary cathode material particles.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a positive electrode active material and its preparation method, a positive electrode sheet containing the same, a battery, and an electrical device. Background Technology

[0002] Secondary batteries rely on the repeated insertion and extraction of active ions between the positive and negative electrodes for charging and discharging. Lithium-ion batteries, in particular, possess outstanding characteristics such as high energy density, long cycle life, and the absence of pollution and memory effect. Therefore, as a clean energy source, secondary batteries have gradually expanded from electronic products to large-scale devices such as electric vehicles, in line with sustainable development strategies for the environment and energy. This, in turn, places higher demands on the energy density of secondary batteries. Summary of the Invention

[0003] To achieve the above objectives, this application provides a positive electrode active material that can improve the energy density, rate performance, and cycle performance of a battery containing the material; this application also provides a method for preparing the positive electrode active material, a positive electrode sheet containing the positive electrode active material, a battery, and an electrical device.

[0004] In a first aspect, embodiments of this application provide a positive electrode active material, comprising ternary positive electrode material particles having a core-shell structure. The ternary positive electrode material particles contain a dopant element M. 1 and dopant element M 2 Furthermore, based on the total molar amount of transition metal elements in the ternary cathode material particles, the molar percentage of Ni element in the ternary cathode material particles is greater than or equal to 0.6; among which, M 1 ionic radius r M1 With lithium ion radius r Li Satisfy: |r M1 -r Li |≤80pm, and M 1 Distributed in the core of ternary cathode material particles; M 2 Including one or more of Zr, Nb, Ta, W, Mo, Ti, and Ir, and M 2 Distributed in the shell of ternary cathode material particles.

[0005] Not intended to be limited to any theory or interpretation, in the embodiments of this application, the above-mentioned M 1 The ionic radius of the element is relatively close to that of the lithium ion, allowing it to be doped into the lithium sites of high-nickel ternary cathode material particles. This helps to widen the interlayer spacing of lithium layers in the high-nickel ternary cathode material particle crystal, improve the lithium-ion diffusion kinetics at the core of the particle, and reduce the energy barrier for lithium-ion migration at the core. The aforementioned M... 2The element is mainly doped into the transition metal sites of the shell of the high-nickel ternary cathode material particles, thereby improving the structural stability of the surface layer of the high-nickel ternary cathode material particles and suppressing structural changes in the surface layer of the high-nickel ternary cathode material particles during excessive lithium delithiation or lithium intercalation. Therefore, the cathode active material of the embodiments of this application can be obtained through M 1 Element and M 2 Hierarchical doping of elements reduces the differences in charge state within the high-nickel ternary cathode material particles during charge-discharge cycles. This improves the structural stability of the high-nickel ternary cathode material particles, reduces internal stress, and thus enhances capacity utilization and cycle stability.

[0006] Therefore, the positive electrode active material of this application embodiment can be applied to a secondary battery to effectively improve the battery's energy density, rate performance, and cycle performance.

[0007] In any embodiment of this application, M 1 Includes one or more of Na, Mg, K, and Ca. M is selected from the above categories. 1 The ionic radius of the element is relatively close to that of lithium ions, allowing it to be readily doped into the lithium sites of high-nickel ternary cathode material particles, thus widening the interlayer spacing of lithium layers within the high-nickel ternary cathode material particle crystal. This helps to further reduce the difference in charge state within the high-nickel ternary cathode material particles during charge-discharge cycles.

[0008] In any embodiment of this application, the ternary cathode material particles have the general formula [Li 1+a M 1 b ][Ni x Co y Mn z M 2 c O2, where 0.6≤x<1, 0≤y≤0.4, 0≤z≤0.4, 0.05≤a+b≤0.1, 0 <b≤0.05,0<c≤0.1,x+y+z+c=1。

[0009] Alternatively, 0.01 ≤ b ≤ 0.03, 0 <c≤0.08。

[0010] The application of nickel-cobalt-manganese ternary materials with the above general formula in secondary batteries can significantly improve the energy density and cycle performance of the batteries.

[0011] In any embodiment of this application, the radius R of the core and the thickness D of the shell satisfy: 0.1 ≤ R / D ≤ 0.9, optionally, 0.4 ≤ R / D ≤ 0.7. When R / D satisfies the above relationship, the cell parameter c of different regions inside the high-nickel ternary cathode material particles can be adjusted within a suitable range, thereby reducing the difference in charge state and stress accumulation inside the high-nickel ternary cathode material particles. This further improves the rate performance and cycle performance of the battery.

[0012] In any embodiment of this application, the cell parameter c of the positive electrode active material is Optional This can reduce the difference in charge state and stress accumulation inside the high-nickel ternary cathode material particles, thereby further improving the rate performance and cycle performance of the battery.

[0013] In any embodiment of this application, the volume distribution particle size span SPAN of the positive electrode active material is (Dv90-Dv10) / Dv50, then SPAN ≥ 1.1, and optionally, SPAN ≥ 1.2. This allows the positive electrode active material to have a higher powder compaction density, thereby increasing the volumetric energy density of the positive electrode active material, and consequently increasing the energy density of the battery.

[0014] In any embodiment of this application, the volume distribution particle size Dv90 of the positive electrode active material is 15μm-25μm, and can be selected as 18μm-22μm.

[0015] In any embodiment of this application, the volume distribution particle size Dv50 of the positive electrode active material is 6μm-14μm, and can be selected as 8μm-12μm.

[0016] In any embodiment of this application, the volume distribution particle size Dv10 of the positive electrode active material is 1μm-5μm, and can be selected as 2μm-4μm.

[0017] This allows the positive electrode active material to have a higher powder compaction density, thereby increasing the volumetric energy density of the positive electrode active material and consequently increasing the energy density of the battery.

[0018] In any embodiment of this application, the powder compaction density of the positive electrode active material under 5 tons of pressure is greater than or equal to 3.5 g / cc, and can be selected as 3.5 g / cc-3.7 g / cc. Therefore, the positive electrode active material of this application, when applied to a secondary battery, can further improve the battery's energy density.

[0019] Secondly, embodiments of this application provide a method for preparing a positive electrode active material, comprising: providing a precursor solution, the precursor solution including a nickel salt, a cobalt salt, a manganese salt, and an M-containing... 1A mixed solution of salts, wherein M 1 ionic radius r M1 With lithium ion radius r Li Satisfy: |r M1 -r Li |≤80pm; Preparation of seed slurry includes uniformly mixing the precursor solution with a first precipitant and a first complexing agent to ensure that nickel salt, cobalt salt, manganese salt, and M-containing... 1 The salt undergoes a co-precipitation reaction in the presence of the first precipitant and the first complexing agent to obtain a product containing M. 1 The precursor seed slurry; the preparation of a ternary cathode material precursor, including mixing the seed slurry with a nickel-cobalt-manganese mixed metal solution, a second precipitant, and a second complexing agent and reacting them to obtain the ternary cathode material precursor; the preparation of the cathode active material, including reacting the ternary cathode material precursor with a lithium source, M... 2 After the source is mixed evenly, it is calcined to obtain the positive electrode active material, M. 2 It includes one or more of Zr, Nb, Ta, W, Mo, Ti, and Ir.

[0020] The positive electrode active material includes ternary positive electrode material particles with a core-shell structure, and the ternary positive electrode material particles contain the doping element M. 1 and dopant element M 2 Based on the total molar amount of transition metal elements in the ternary cathode material particles, the molar percentage of Ni element in the ternary cathode material particles is greater than or equal to 0.6; among which, M 1 Distributed in the core of ternary cathode material particles, and M 2 Distributed in the shell of ternary cathode material particles.

[0021] Not intended to be limited to any theory or explanation, the above-mentioned high-nickel ternary cathode material particles can be prepared according to the method of the embodiments of this application. In the above-mentioned high-nickel ternary cathode material particles, M... 1 Doping elements into the lithium sites of high-nickel ternary cathode material particles helps to widen the interlayer spacing of lithium layers in the high-nickel ternary cathode material particle crystal, thereby improving the lithium-ion diffusion kinetics at the core of the high-nickel ternary cathode material particle and reducing the energy barrier for lithium-ion migration at the core; M 2 The elements are mainly doped into the transition metal sites of the shell of high-nickel ternary cathode material particles, thereby improving the structural stability of the surface layer of the high-nickel ternary cathode material particles and suppressing structural changes in the surface layer of the high-nickel ternary cathode material particles during excessive lithium delithiation or lithium intercalation. Therefore, the method according to the embodiments of this application can be achieved through M 1 Element and M 2Hierarchical doping of elements reduces the differences in charge state within the high-nickel ternary cathode material particles during charge-discharge cycles. This improves the structural stability of the high-nickel ternary cathode material particles, reduces internal stress, and thus enhances capacity utilization and cycle stability.

[0022] In any embodiment of this application, M is included. 1 Salts containing M 1 One or more of the following: sulfates, nitrates, carbonates, oxalates, and chlorides of the element. Selected from the above categories containing M. 1 The salt can undergo a co-precipitation reaction, allowing M to... 1 Elements are uniformly distributed in the M-containing area. 1 In the precursor seed crystal. Therefore, it is beneficial to M. 1 During the calcination process, the elements are successfully doped into the lithium sites in the core of the ternary cathode material particles, which is beneficial to the large lithium ion diffusion rate inside the high-nickel ternary cathode material particles.

[0023] In any embodiment of this application, the first precipitant and the second precipitant each independently include one or more of sodium hydroxide, sodium carbonate, potassium carbonate, and potassium hydroxide.

[0024] In any embodiment of this application, the first complexing agent and the second complexing agent each independently include one or more of ammonia, ammonium chloride, ammonium sulfate, urea, citric acid, and EDTA.

[0025] In any embodiment of this application, the pH of the coprecipitation reaction is 11.5-14, and the reaction temperature is 50℃-80℃.

[0026] By adjusting at least one of the precipitant, complexing agent, pH of the coprecipitation reaction, and reaction temperature to meet the above conditions, the content of M can be controlled. 1 The composition and structure of the precursor seed crystals. Therefore, it is permissible to include M... 1 The precursor seed crystals have a high nickel content and a suitable particle size, which is beneficial to improving the theoretical specific capacity of high-nickel ternary cathode material particles and the structural stability of the core.

[0027] In any embodiment of this application, M is included. 1 Precursor seed volume distribution and grain size Dv 1 50 represents 1μm-5μm.

[0028] When containing M 1 Precursor seed volume distribution and grain size Dv 1When 50 meets the given range, the core of the high-nickel ternary cathode material particles can have an appropriate radius. This is beneficial for further reducing the difference in charge state within the high-nickel ternary cathode material particles, thereby improving the cycle performance and rate performance of the battery.

[0029] In any embodiment of this application, M 2 The source includes M 2 One or more of the following: sulfates, carbonates, oxides, hydroxides, nitrates, silicates, acetates, and oxalates of the element. This is beneficial to M. 2 During the calcination process, the elements are successfully doped into the transition metal sites on the surface of the high-nickel ternary cathode material particles, which helps to improve the structural stability of the surface of the high-nickel ternary cathode material particles.

[0030] In any embodiment of this application, in the step of preparing the ternary cathode material precursor, the pH of the reaction is 10-12 and the reaction temperature is 30℃-60℃.

[0031] By controlling the pH and temperature of the reaction within the appropriate range during the preparation of the ternary cathode material precursor, it is beneficial for nickel ions, cobalt ions, and manganese ions to be uniformly co-precipitated on the substrate containing M. 1 The surface of the precursor seed crystals is used to obtain a structurally complete ternary cathode material precursor.

[0032] In any embodiment of this application, the volume distribution particle size Dv of the ternary cathode material precursor 2 50 is 5μm-15μm.

[0033] Therefore, it is beneficial to M 2 During the calcination process, the elements are successfully doped into the surface of the high-nickel ternary cathode material particles, giving the shell of the high-nickel ternary cathode material particles a suitable thickness. This helps to further reduce the difference in charge state inside the high-nickel ternary cathode material particles and improve the cycle performance and rate performance of the battery.

[0034] In any embodiment of this application, the lithium source includes one or more of LiOH·H2O, Li2CO3, Li2SO4, LiNO3, LiC2O4, and CH3COOLi.

[0035] Optionally, the molar amount n of Li in the lithium source Li It can satisfy 1.0≤n Li / n Me ≤1.2, where n Me This represents the total molar amount of Ni, Co, and Mn elements in the ternary cathode material precursor.

[0036] Therefore, the structure of ternary cathode material particles can be controlled to prepare high-nickel ternary cathode material particles with excellent electrochemical performance.

[0037] In any embodiment of this application, the ternary cathode material precursor is combined with a lithium source and M 2 After the source and source are mixed evenly, calcination is performed to obtain the positive electrode active material, including: a ternary positive electrode material precursor and a lithium source, M 2 After the source material is uniformly mixed, it is calcined at 500℃-700℃ for 8-12 hours, followed by calcination at 600℃-900℃ for 4-8 hours to obtain the positive electrode active material. The calcination atmosphere is oxygen-containing. This helps M... 1 Element and M 2 The hierarchical doping of elements within the high-nickel ternary cathode material particles enables M... 1 The element is distributed in the core of the high-nickel ternary material particles, M 2 The elements are distributed in the shell of the high-nickel ternary material particles, which helps to improve the cycle performance and rate performance of the battery.

[0038] Thirdly, embodiments of this application provide a 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. The positive electrode film layer includes the positive electrode active material of the first aspect, or the positive electrode active material prepared according to the method of the second aspect.

[0039] The fourth aspect of this application provides a battery, including the positive electrode sheet of the third aspect.

[0040] The fifth aspect of this application provides an electrical device, including the battery of the fourth aspect.

[0041] The electrical device in this application embodiment includes a battery of the fourth aspect, and thus has at least the same advantages as the battery. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the structure of ternary cathode material particles in one embodiment of this application.

[0043] Figure 2 This is a schematic diagram illustrating an embodiment of the battery cell of this application.

[0044] Figure 3 yes Figure 2 An exploded view of an embodiment of the battery cell of this application is shown.

[0045] Figure 4 This is a schematic diagram of one embodiment of the battery module of this application.

[0046] Figure 5 This is a schematic diagram of one embodiment of the battery pack of this application.

[0047] Figure 6 yes Figure 5 The diagram shown is an exploded view of an embodiment of the battery pack of this application.

[0048] Figure 7 This is a schematic diagram of one embodiment of the power supply device of this application, which may include a battery pack or battery module as a power source according to the embodiments of this application.

[0049] 10 Ternary cathode material particles; 11 Core; 12 Shell; 1 Battery pack; 2 Upper casing; 3 Lower casing; 4 Battery module; 5 Battery cell; 51 Casing; 52 Electrode assembly; 53 Cover plate. Detailed Implementation

[0050] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the positive electrode active material, its preparation method, the positive electrode sheet comprising the same, the battery, and the power supply device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0051] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints 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 included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 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 application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" 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.

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

[0053] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0054] Unless otherwise specified, all steps in this 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 it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0055] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0056] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: 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).

[0057] Unless otherwise stated, all ratio parameters involved in this application are compared under the condition that the units are the same. For example, the thickness ratio of A to B is 1.2:1, in which case the thickness units of A and B are the same.

[0058] With the application and promotion of secondary batteries in various electronic products and new energy vehicles, higher requirements have been placed on the energy density of secondary batteries.

[0059] Increasing the charging cutoff voltage of a battery is considered an effective way to improve its energy density. Currently, the cathode materials for commercially available high-capacity lithium-ion batteries mainly include ternary cathode materials (such as nickel-cobalt-manganese ternary cathode materials or nickel-cobalt-aluminum ternary cathode materials).

[0060] Studies have shown that using high-nickel ternary cathode materials—that is, ternary cathode materials where the molar ratio of Ni in the transition metal elements is greater than or equal to 0.6—can further improve the energy density of batteries. However, high-nickel ternary cathode materials exhibit severe cation mixing during charge-discharge cycles, leading to irreversible phase transitions. In particular, during high-voltage charge-discharge cycles, the internal crystal structure changes of high-nickel ternary cathode material particles intensify, causing particle cracking, pulverization, and deactivation. This not only limits the capacity utilization of the high-nickel ternary cathode material but also deteriorates the battery's rate performance and cycle performance.

[0061] In view of this, embodiments of this application provide a positive electrode active material that can improve the energy density, rate performance and cycle performance of a battery containing the material; this application also provides a method for preparing a positive electrode active material, a positive electrode sheet containing the positive electrode active material, a battery and an electrical device.

[0062] Positive electrode active material

[0063] The first aspect of this application provides a positive electrode active material comprising ternary positive electrode material particles having a core-shell structure.

[0064] The ternary cathode material particles contain the dopant element M. 1 and dopant element M 2 Furthermore, based on the total molar amount of transition metal elements in the ternary cathode material particles, the molar percentage of Ni element in the ternary cathode material particles is greater than or equal to 0.6. Among them, M... 1 ionic radius r M1 With lithium ion radius r Li Satisfy: |r M1 -r Li |≤80pm, and M 1 Distributed in the core of ternary cathode material particles. M 2 Including one or more of Zr, Nb, Ta, W, Mo, Ti, and Ir, and M 2 Distributed in the shell of ternary cathode material particles.

[0065] The “core-shell” structure described above has a meaning known in the art. Figure 1 A schematic diagram of ternary cathode material particles according to an embodiment of this application is shown. Figure 1 As shown, the ternary cathode material particle 10 may include a core 11 and a shell 12. The core 11 is located in the central region of the ternary cathode material particle 10 and is doped with element M. 1 The core 11 (not shown in the figure) is distributed therein. The shell 12 is located in the outer periphery of the core 11 and is doped with element M. 2Distributed in the shell 12 (not shown in the figure). The "core-shell" structure can be determined using equipment and methods known in the art. For example, the EDS elemental distribution map of the cross-section of the ternary cathode material particles can be determined using an EDS spectrometer; the EDS elemental distribution map of the cross-section of the ternary cathode material particles is processed, and a circle is drawn with the geometric center of the cross-section of the ternary cathode material particles as the center, and the radius of the circle is adjusted so that M is within the area of ​​the circle. 1 The pixels corresponding to the element occupy 90% of the entire cross-section. The area below this radius is the core, and the remaining area is the shell.

[0066] The “M” mentioned above 1 The phrase "distributed in the core of ternary cathode material particles" has a well-known meaning in the art, and can represent M. 1 The element is mainly distributed in the core of the ternary cathode material particles. Specifically, in the EDS elemental distribution map of the cross-section of the ternary cathode material particles, more than 10 core test areas and more than 10 shell test areas are randomly selected. In the core test area, M... 1 The average molar concentration of the element c1 and M in the shell region 2 The average molar concentration c2 of the element satisfies: [(c1-c2) / c2]×100%≥90%.

[0067] The “M” mentioned above 2 "Distributed in the shell of ternary cathode material particles" can represent M 2 The element is mainly distributed in the shell of the ternary cathode material particles. That is, in the EDS elemental distribution map of the cross-section of the ternary cathode material particles, more than 10 shell test areas and more than 10 core test areas are randomly selected. In the shell test area, M 2 The average molar concentration of the element c3 and M in the core region 2 The average molar concentration c4 of the element satisfies: [(c3-c4) / c4]×100%≥90%.

[0068] Research has revealed that due to limitations in lithium-ion diffusion kinetics, high-nickel ternary cathode material particles exhibit significant differences in charge state within their interiors. The charge state at the surface of these particles is higher than that in the central region, leading to uneven cell volume changes and stress generation, which in turn causes structural changes in the high-nickel ternary cathode material particles. Related technologies involve doping the ternary cathode material particles to ensure uniform distribution of dopant elements within the crystal structure. While these technologies can improve the structural stability of the ternary cathode material particles to some extent, they are insufficient to address the charge state differences caused by variations in lithium-ion diffusion kinetics during charge-discharge cycling. Therefore, their improvement on the cycle performance of the ternary cathode material particles is very limited.

[0069] Not intended to be limited to any theory or interpretation, in the embodiments of this application, the above-mentioned M 1 The ionic radius of the element is relatively close to that of the lithium ion, allowing it to be doped into the lithium sites of high-nickel ternary cathode material particles. This helps to widen the interlayer spacing of lithium layers in the high-nickel ternary cathode material particle crystal, improve the lithium-ion diffusion kinetics at the core of the particle, and reduce the energy barrier for lithium-ion migration at the core. The aforementioned M... 2 The element is mainly doped into the transition metal sites of the shell of the high-nickel ternary cathode material particles, thereby improving the structural stability of the surface layer of the high-nickel ternary cathode material particles and suppressing structural changes in the surface layer of the high-nickel ternary cathode material particles during excessive lithium delithiation or lithium intercalation. Therefore, the cathode active material of the embodiments of this application can be obtained through M 1 Element and M 2 Hierarchical doping of elements reduces the differences in charge state within the high-nickel ternary cathode material particles during charge-discharge cycles. This improves the structural stability of the high-nickel ternary cathode material particles, reduces internal stress, and thus enhances capacity utilization and cycle stability.

[0070] Therefore, the positive electrode active material of this application embodiment can be applied to a secondary battery to effectively improve the battery's energy density, rate performance, and cycle performance.

[0071] In some implementations, M 1 It can include one or more of Na, Mg, K, and Ca.

[0072] Not intended to be limited to any theory or explanation, but selected from the above-mentioned types of M 1 The ionic radius of the element is relatively close to that of the lithium ion, allowing it to be readily doped into the lithium sites of high-nickel ternary cathode material particles. This widens the interlayer spacing of lithium layers within the high-nickel ternary cathode material particle crystal, thereby further improving the lithium-ion diffusion kinetics at the core of the particle and reducing the energy barrier for lithium-ion migration. Consequently, this helps to further reduce the difference in charge state within the high-nickel ternary cathode material particles during charge-discharge cycles. Therefore, the cathode active material of this application, when applied to a secondary battery, can further improve the battery's energy density, rate performance, and cycle performance.

[0073] In some embodiments, the ternary cathode material particles may have the general formula [Li 1+a M 1 b ][Ni x Co y Mn z M 2 cO2, where 0.6≤x<1, 0≤y≤0.4, 0≤z≤0.4, 0.05≤a+b≤0.1, 0 <b≤0.05,0<c≤0.1,x+y+z+c=1。

[0074] Alternatively, in some implementations, 0.01 ≤ b ≤ 0.03, 0 <c≤0.08。

[0075] Optionally, in some implementations, x can be greater than or equal to 0.8, for example, it can be 0.8, 0.9, 0.95, etc.

[0076] Not intended to be limited to any theory or explanation, nickel-cobalt-manganese ternary materials with the above general formula have a high nickel content, and therefore a high theoretical specific capacity. Furthermore, nickel-cobalt-manganese ternary materials with the above general formula also possess suitable M... 1 Element doping amount and appropriate M 2 The amount of elemental doping results in higher structural stability. Therefore, the application of nickel-cobalt-manganese ternary materials with the above general formula in secondary batteries can significantly improve the energy density and cycle performance of the batteries.

[0077] In some embodiments, the radius R of the core and the thickness D of the shell can satisfy: 0.1 ≤ R / D ≤ 0.9. For example, R / D can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or a range consisting of any two of the above values.

[0078] Optionally, in some embodiments, the radius R of the core and the thickness D of the shell can also satisfy: 0.4 ≤ R / D ≤ 0.7. For example, R / D can be 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, or any range of two of the above values.

[0079] By adjusting the radius of the core and the thickness of the shell in high-nickel ternary cathode material particles, the cell parameter c in different regions within the particles can be adjusted. When R / D satisfies the above relationship, the cell parameter c in different regions within the high-nickel ternary cathode material particles can be adjusted within a suitable range, thereby enabling the high-nickel ternary cathode material particles to exhibit a higher lithium-ion migration rate, thus reducing the charge state differences and stress accumulation within the particles. This further improves the rate performance and cycle performance of the battery.

[0080] In some embodiments, the cell parameter c of the positive electrode active material can be...

[0081] Optionally, in some embodiments, the cell parameter c of the positive electrode active material can also be...

[0082] This is not intended to be limited by any theory or explanation. When the cell parameter c of the positive electrode active material is within the aforementioned suitable range, it can result in a higher lithium-ion migration rate within the high-nickel ternary positive electrode material particles, thereby reducing the difference in charge state and stress accumulation within the particles. This can further improve the rate performance and cycle performance of the battery.

[0083] The cell parameter c of the positive electrode active material has a meaning known in the art and can be determined by equipment and methods known in the art. For example, it can be determined by X-ray powder diffraction.

[0084] In some embodiments, the volume distribution particle size span of the positive electrode active material is SPAN = (Dv90 - Dv10) / Dv50. For example, SPAN can be 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, or any range of two of the above values.

[0085] Optionally, in some implementations, SPAN ≥ 1.2. For example, SPAN can be 1.2-2.0, 1.3-2.0, 1.4-2.0, 1.5-2.0, 1.6-2.0, 1.7-2.0, 1.8-2.0, 1.9-2.0, 1.2-1.9, 1.3-1.8, 1.4-1.7, 1.5-1.6, etc.

[0086] Not intended to be limited by any theory or explanation, when the positive electrode active material has the aforementioned large volumetric particle size distribution span (SPAN) value, it indicates that the positive electrode active material has a wide particle size distribution. This allows the positive electrode active material to have a higher powder compaction density, thereby increasing its volumetric energy density. Therefore, the positive electrode active material of this application, when applied to a secondary battery, can further improve the battery's energy density.

[0087] In some embodiments, the volume distribution particle size Dv90 of the positive electrode active material can be 15 μm-25 μm. For example, Dv90 can be 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, or any range of two of the above values.

[0088] Optionally, in some embodiments, the volume distribution particle size D of the positive electrode active material is... v90 can also be 18μm-22μm. For example, Dv90 can be 18μm, 18.5μm, 19μm, 19.5μm, 20μm, 20.5μm, 21μm, 21.5μm, 22μm, or any range of two of the above values.

[0089] In some embodiments, the volumetric particle size distribution Dv50 of the positive electrode active material can be 6 μm-14 μm. For example, Dv50 can be 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, or any range of two of the above values.

[0090] Optionally, in some embodiments, the volume distribution particle size Dv50 of the positive electrode active material can also be 8μm-12μm. For example, Dv50 can be 8μm, 8.5μm, 9μm, 9.5μm, 10μm, 10.5μm, 11μm, 11.5μm, 12μm, or any range of two of the above values.

[0091] In some embodiments, the volumetric particle size Dv10 of the positive electrode active material can be 1 μm-5 μm. For example, Dv10 can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, or any range of two of the above values.

[0092] Optionally, in some embodiments, the volume distribution particle size D of the positive electrode active material is... v 10 can also be 2μm-4μm. For example, Dv10 can be 2μm, 2.2μm, 2.5μm, 2.8μm, 3μm, 3.2μm, 3.5μm, 3.8μm, 4μm, or any range of two of the above values.

[0093] Not intended to be limited by any theory or explanation, when one or more of the volume distribution particle sizes Dv90, Dv50, and Dv10 of the positive electrode active material meet the given range, a wider particle size distribution is permissible. This allows the positive electrode active material to have a higher powder compaction density, thereby increasing the volumetric energy density of the positive electrode active material and consequently, the energy density of the battery.

[0094] The volume distribution particle size of the positive electrode active material has a meaning known in the art and can be determined using equipment and methods known in the art. Specifically, the volume distribution particle size Dv50 refers to the particle size corresponding to a cumulative volume distribution percentage of 50%; the volume distribution particle size Dv10 refers to the particle size corresponding to a cumulative volume distribution percentage of 10%; and the volume distribution particle size Dv90 refers to the particle size corresponding to a cumulative volume distribution percentage of 90%. The volume distribution particle sizes Dv50, Dv10, and Dv90 of the positive electrode active material can all be determined using laser diffraction particle size analysis. For example, referring to standard GB / T19077-2016, a laser particle size analyzer (e.g., Malvern Master Size 3000) can be used for determination.

[0095] In some embodiments, the powder compaction density of the positive electrode active material at a pressure of 5 tons is greater than or equal to 3.5 g / cc, and can be selected as 3.5 g / cc-3.7 g / cc. When the powder compaction density of the positive electrode active material at a pressure of 5 tons meets the given range, the positive electrode active material can have a high volumetric energy density. Therefore, the positive electrode active material of this application embodiment, when applied to a secondary battery, can further improve the energy density of the battery.

[0096] The compaction density of positive electrode active material powder under 5 tons of pressure has a well-known meaning in the art and can be determined by equipment and methods known in the art. As an example, the compaction density of positive electrode active material under 5 tons of pressure (i.e., 5T pressure) can be determined with reference to GB / T 24533-2009. Specifically, a certain amount of positive electrode active material powder can be placed in a compaction mold, and then the mold can be placed on a compaction density instrument. A pressure of 5T is applied, and the thickness of the powder under 5T pressure (the thickness after depressurization) is read on the instrument. The compaction density ρ of the positive electrode active material powder is calculated using ρ = m / v.

[0097] Preparation method

[0098] Secondly, embodiments of this application provide a method for preparing a positive electrode active material, comprising the following steps S10 to S40.

[0099] S10 provides a precursor solution, the precursor solution comprising nickel salt, cobalt salt, manganese salt, and M-containing salt. 1 A mixed solution of salts, wherein M 1 ionic radius r M1 With lithium ion radius r Li Satisfy: |r M1 -r Li ≤80pm.

[0100] In step S10, providing the precursor solution may include a nickel salt solution, a cobalt salt solution, a manganese salt solution, and a solution containing M.1 The salt solutions are mixed to obtain a mixed solution; it may also include nickel salts, cobalt salts, manganese salts, and salts containing M. 1 The salts are mixed and dissolved in deionized water to obtain a mixed solution, which is not limited here.

[0101] Nickel salts, cobalt salts, manganese salts and salts containing M 1 The salt can be selected from soluble nickel salts, cobalt salts, manganese salts, and salts containing M known in the art. 1 Salts. Examples of soluble nickel salts may include one or more of nickel-containing sulfates, nitrates, acetates, carbonates, oxalates, citrates, chlorides, etc. Examples of soluble cobalt salts may include one or more of cobalt-containing sulfates, nitrates, acetates, carbonates, oxalates, citrates, chlorides, etc. Examples of soluble manganese salts may include one or more of manganese-containing sulfates, nitrates, acetates, carbonates, oxalates, citrates, chlorides, etc. Those skilled in the art can select according to actual needs, and no limitation is made herein. Nickel salts, cobalt salts, manganese salts, and salts containing M... 1 The salt ratio can be adjusted according to actual needs. For example, it can be adjusted based on the proportions of Ni, Co, Mn, and Mn in the ternary cathode material particles to be prepared. 1 The molar ratio of elements was adjusted to control the nickel, cobalt, and manganese salts used in preparing the precursor solution, as well as the M-containing salts. 1 The proportion of salts. The concentration of the precursor solution is not specifically limited and can be adjusted as needed by those skilled in the art. As an example, the precursor solution contains Ni, Co, Mn, and M... 1 The total concentration of elements can range from 0.1 mol / L to 10 mol / L.

[0102] S20, preparing seed slurry, includes uniformly mixing the precursor solution with a first precipitant and a first complexing agent to ensure that nickel salt, cobalt salt, manganese salt, and M-containing... 1 The salt undergoes a co-precipitation reaction in the presence of the first precipitant and the first complexing agent to obtain a product containing M. 1 Precursor seed slurry.

[0103] In step S20, examples of the first precipitant and the first complexing agent may include one or more precipitants and complexing agents known in the art. Those skilled in the art can select them according to actual needs, and no limitation is made herein. In one embodiment, 10L-50L of pure water can be added to a 100L reactor, and a certain amount of the first precipitant solution is added under stirring until the concentration is 0.2mol / L to 0.6mol / L, optionally 0.3mol / L to 0.5mol / L. The precursor solution, the first precipitant solution, and the first complexing agent solution are added to the reactor at a certain rate, keeping the pH of the solution in the reactor and the concentration of the complexing agent essentially constant, so that the nickel salt, cobalt salt, manganese salt, and M-containing... 1 The salt underwent a co-precipitation reaction in the presence of the first precipitant and the first complexing agent, followed by centrifugation, washing, filtration, and drying to obtain a product containing M. 1 The precursor seed slurry. The concentration of the first precipitant solution can be from 0.1 mol / L to 20 mol / L; the concentration of the first complexing agent solution can be from 0.1 mol / L to 10 mol / L.

[0104] S30, preparing a ternary cathode material precursor, includes mixing seed slurry with a nickel-cobalt-manganese mixed metal solution, a second precipitant, and a second complexing agent, and reacting them to obtain a ternary cathode material precursor.

[0105] In step S30, the second precipitant and the second complexing agent can be the same as or different from the first precipitant and the first complexing agent. Examples of the second precipitant and the second complexing agent may include one or more precipitants and complexing agents known in the art, and those skilled in the art can select them according to actual needs, without limitation. The nickel-cobalt-manganese mixed metal solution may be a solution including nickel ions, cobalt ions, and manganese ions, for example, it may be a mixed solution of nickel salts, cobalt salts, and manganese salts. The ratio of nickel ions, cobalt ions, and manganese ions can be adjusted according to actual needs, for example, according to the Ni, Co, Mn, and M elements in the ternary cathode material particles to be prepared. 1 The molar ratio of the elements is adjusted to control the proportions of nickel ions, cobalt ions, and manganese ions in the preparation of the nickel-cobalt-manganese mixed metal solution.

[0106] In some embodiments, step S30 may include: taking a portion of the M-containing material synthesized in step S10. 1 The precursor seed slurry was used as the base solution, and the pH was adjusted to a certain value; then, a nickel-cobalt-manganese mixed metal solution, a second precipitant solution, a second complexing agent solution, and the remaining M-containing solution were added. 1The precursor seed slurry is added to the reactor in parallel flow at a certain flow rate, while maintaining the concentration and pH of the second complexing agent in the reactor. After the reaction is complete, the ternary cathode material precursor is obtained. As an example, 10L-50L of pure water can be added to a 100L reactor, along with 1kg-20kg of a solution containing M... 1 Using the precursor seed slurry as the base liquid, a certain amount of the second precipitant solution is added under stirring to a concentration of 0.2 mol / L to 0.6 mol / L, optionally 0.3 mol / L to 0.5 mol / L; then, the nickel-cobalt-manganese mixed metal solution, the second precipitant solution, the second complexing agent solution, and the remaining M-containing... 1 The precursor seed slurry is added to the reactor at a certain rate. The concentration of the second precipitant solution can be from 0.1 mol / L to 20 mol / L; the concentration of the second complexing agent solution can be from 0.1 mol / L to 10 mol / L.

[0107] S40, Preparation of positive electrode active material, including combining ternary positive electrode material precursor with lithium source, M 2 After the source is mixed evenly, it is calcined to obtain the positive electrode active material, M. 2 It includes one or more of Zr, Nb, Ta, W, Mo, Ti, and Ir.

[0108] In step S40, the ternary cathode material precursor and the lithium source, M 2 After the source is mixed evenly, during the calcination process, M 1 Elements can be doped into the lithium sites of ternary cathode material particles in the central region, thus distributing within the core of the ternary cathode material particles. M 2 Elements can penetrate from the surface of the ternary cathode material precursor into the interior, thus distributing in the shell of the ternary cathode material particles.

[0109] The positive electrode active material prepared according to steps S10 to S40 includes ternary positive electrode material particles with a core-shell structure, and the ternary positive electrode material particles contain dopant element M. 1 and dopant element M 2 Based on the total molar amount of transition metal elements in the ternary cathode material particles, the molar percentage of Ni element in the ternary cathode material particles is greater than or equal to 0.6. Among them, M... 1 Distributed in the core of ternary cathode material particles, and M 2 Distributed in the shell of ternary cathode material particles.

[0110] Not intended to be limited to any theory or explanation, the above-mentioned high-nickel ternary cathode material particles can be prepared according to the method of the embodiments of this application. In the above-mentioned high-nickel ternary cathode material particles, M... 1Doping elements into the lithium sites of high-nickel ternary cathode material particles helps to widen the interlayer spacing of lithium layers in the high-nickel ternary cathode material particle crystal, thereby improving the lithium-ion diffusion kinetics at the core of the high-nickel ternary cathode material particle and reducing the energy barrier for lithium-ion migration at the core; M 2 The elements are mainly doped into the transition metal sites of the shell of high-nickel ternary cathode material particles, thereby improving the structural stability of the surface layer of the high-nickel ternary cathode material particles and suppressing structural changes in the surface layer of the high-nickel ternary cathode material particles during excessive lithium delithiation or lithium intercalation. Therefore, the method according to the embodiments of this application can be achieved through M 1 Element and M 2 Hierarchical doping of elements reduces the differences in charge state within the high-nickel ternary cathode material particles during charge-discharge cycles. This improves the structural stability of the high-nickel ternary cathode material particles, reduces internal stress, and thus enhances capacity utilization and cycle stability.

[0111] Therefore, the positive electrode active material prepared according to the method of this application embodiment can be applied to a secondary battery to effectively improve the battery's energy density, rate performance, and cycle performance.

[0112] In some implementations, M 1 Salts may include those containing M 1 One or more of the elements' sulfates, nitrates, carbonates, oxalates, and chlorides.

[0113] Not intended to be limited to any theory or explanation, but selected from the above-mentioned categories containing M 1 The salt can undergo a co-precipitation reaction, allowing M to... 1 Elements are uniformly distributed in the M-containing area. 1 In the precursor seed crystal. Therefore, it is beneficial to M. 1 During the calcination process, the elements are successfully doped into the lithium sites at the core of the ternary cathode material particles, which is beneficial for the high lithium-ion diffusion rate inside the high-nickel ternary cathode material particles. Therefore, the cathode active material prepared in this embodiment can be applied to a secondary battery to reduce the difference in charge state inside the high-nickel ternary cathode material particles during charge-discharge cycles, thereby further improving the battery's energy density, rate performance, and cycle performance.

[0114] In some embodiments, the first precipitant and the second precipitant may each independently include one or more of sodium hydroxide, sodium carbonate, potassium carbonate, and potassium hydroxide.

[0115] In some embodiments, the first complexing agent and the second complexing agent may each independently include one or more of ammonia, ammonium chloride, ammonium sulfate, urea, citric acid, and EDTA.

[0116] In some embodiments, the pH of the coprecipitation reaction can be 11.5-14, optionally 12-13. The reaction temperature of the coprecipitation reaction can be 50℃-80℃.

[0117] Not intended to be limited to any theory or explanation, but by controlling at least one of the following conditions—the precipitant, complexing agent, pH of the coprecipitation reaction, and reaction temperature—the content of M can be controlled. 1 The composition and structure of the precursor seed crystals. Therefore, it is permissible to include M... 1 The precursor seed crystals have a high nickel content and a suitable particle size, which is beneficial to improving the theoretical specific capacity of high-nickel ternary cathode material particles and the structural stability of the core.

[0118] In some implementations, M 1 Precursor seed volume distribution and grain size Dv 1 50 can be 1μm-5μm.

[0119] It is not intended to be limited to any theory or explanation, when M is included 1 Precursor seed volume distribution and grain size Dv 1 When 50 meets the given range, the structure of high-nickel ternary cathode material particles can be controlled, so that the core of the high-nickel ternary cathode material particles has an appropriate radius. This is beneficial to further reduce the difference in charge state inside the high-nickel ternary cathode material particles, thereby improving the structural stability of the cathode active material, and thus improving the cycle performance and rate performance of the battery.

[0120] In some implementations, M 2 The source may include M 2 One or more of the following: sulfate, carbonate, oxide, hydroxide, nitrate, silicate, acetate, and oxalate of an element.

[0121] It is not intended to be limited to any theory or explanation, when M 2 When the source is selected from the above substances, it is beneficial to M. 2 During calcination, elements are successfully doped into the transition metal sites on the surface of high-nickel ternary cathode material particles, thereby improving the structural stability of the particle surface and suppressing structural changes during excessive delithiation or lithiation. This, in turn, helps to further improve the rate performance and cycle performance of the battery.

[0122] In some embodiments, the pH of the reaction in the step of preparing the ternary cathode material precursor can be 10-12, and the reaction temperature can be 30℃-60℃.

[0123] By controlling the pH and temperature of the reaction within the appropriate range during the preparation of the ternary cathode material precursor, it is beneficial for nickel ions, cobalt ions, and manganese ions to be uniformly co-precipitated on the substrate containing M. 1 The surface of the precursor seed crystals is used to obtain a structurally complete ternary cathode material precursor.

[0124] In some embodiments, the volumetric particle size Dv of the ternary cathode material precursor 2 50 can be 5μm-15μm.

[0125] It is not intended to be limited by any theory or explanation, but to control the volume distribution and particle size Dv of the ternary cathode material precursor. 2 50 Within the above-mentioned suitable range, it is beneficial to M 2 During the calcination process, the elements are successfully doped into the surface layer of the high-nickel ternary cathode material particles. This allows the shell of the high-nickel ternary cathode material particles to have a suitable thickness, which helps to further reduce the difference in charge state inside the high-nickel ternary cathode material particles, thereby improving the structural stability of the cathode active material and ultimately enhancing the cycle performance and rate performance of the battery.

[0126] In some embodiments, the lithium source may include one or more of LiOH·H2O, Li2CO3, Li2SO4, LiNO3, LiC2O4, and CH3COOLi. The molar amount n of Li in the lithium source is... Li It can satisfy 1.0≤n Li / n Me ≤1.2, where n Me This represents the total molar amount of Ni, Co, and Mn elements in the ternary cathode material precursor. Therefore, the structure of the ternary cathode material particles can be controlled to prepare high-nickel ternary cathode material particles with excellent electrochemical performance.

[0127] In some embodiments, the ternary cathode material precursor is combined with a lithium source and M 2 After the source and source are mixed evenly, calcination is performed to obtain the positive electrode active material. Specifically, this may include: mixing the ternary positive electrode material precursor with a lithium source and M... 2 After the source is mixed evenly, it is calcined at 500℃-700℃ for 8h-12h, and then calcined at 600℃-900℃ for 4h-8h to obtain the positive electrode active material. The calcination atmosphere is an oxygen-containing atmosphere, such as, but not limited to, air or oxygen atmosphere.

[0128] Not intended to be limited to any theory or explanation, this embodiment employs a stepwise calcination process of low temperature followed by high temperature, which can reduce M 1 Ions and M 2 The risk of high-temperature ion diffusion. Therefore, this contributes to M. 1 Element and M2 The hierarchical doping of elements within the high-nickel ternary cathode material particles enables M... 1 The element is distributed in the core of the high-nickel ternary material particles, M 2 The elements are distributed in the shell of the high-nickel ternary material particles, which helps to improve the cycle performance and rate performance of the battery.

[0129] Positive electrode sheet

[0130] A third aspect of this application provides 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. The positive electrode film layer includes the positive electrode active material of the first aspect, or the positive electrode active material prepared according to the method of the second aspect.

[0131] The positive electrode sheet of this application embodiment includes the positive electrode active material of the first aspect, or the positive electrode active material prepared according to the method of the second aspect, and is applied to a secondary battery, which can enable the secondary battery to have high energy density, good rate performance and cycle performance.

[0132] In some embodiments, the positive electrode film may optionally include a positive electrode conductive agent. This application does not impose any particular limitation on the type of positive electrode conductive agent. As an example, the positive electrode conductive agent includes at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0133] In some embodiments, the positive electrode film layer may optionally include a positive electrode binder. This application does not impose any particular limitation on the type of positive electrode binder. As an example, the positive electrode binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0134] In some embodiments, the positive current collector may be a metal foil or a composite current collector. An example of a metal foil is aluminum foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. An example of a metal material may be at least one selected from aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. An example of a polymer substrate may be at least one selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0135] The positive electrode film is typically formed by coating a positive electrode slurry onto a positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is usually formed by dispersing the positive electrode active material, optional conductive agent, optional binder, and any other components in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP), but is not limited to it.

[0136] Battery

[0137] The battery mentioned in the embodiments of this application may be a single physical module comprising one or more battery cells to provide higher voltage and capacity. When there are multiple battery cells, the multiple battery cells are connected in series, parallel, or mixed via a busbar.

[0138] Typically, a battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode, a negative electrode, and a separator. During the charging and discharging process of the battery cell, active ions (such as lithium ions) repeatedly insert and extract between the positive and negative electrodes. The separator, located between the positive and negative electrodes, prevents short circuits while allowing active ions to pass through. The electrolyte, situated between the positive and negative electrodes, conducts the active ions.

[0139] [Positive electrode plate]

[0140] In the battery cell of this application embodiment, the positive electrode of the electrode assembly may include a positive electrode from a third aspect. The embodiments of the positive electrode have been described and illustrated in detail above, and will not be repeated here. It is understood that the battery cell of this application embodiment can achieve the beneficial effects of any of the above-described embodiments of the positive electrode of this application embodiment.

[0141] [Negative electrode plate]

[0142] The negative electrode sheet may include a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector and comprising a negative electrode active material. For example, the negative current collector has two surfaces opposite 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 current collector.

[0143] The negative electrode active material may be any negative electrode active material known in the art for use in secondary batteries. As an example, the negative electrode active material may include, but is not limited to, at least one of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. Silicon-based materials may include at least one of elemental silicon, silicon oxide, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include at least one of elemental tin, tin oxide, and tin alloys.

[0144] In some embodiments, the negative electrode film layer may optionally include a negative electrode conductive agent. This application does not impose any particular limitation on the type of negative electrode conductive agent. As an example, the negative electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0145] In some embodiments, the negative electrode film layer may optionally include a negative electrode binder. This application does not impose any particular limitation on the type of negative electrode binder. As an example, the negative electrode binder may include at least one of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0146] In some embodiments, the negative electrode film may optionally include other additives. As an example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc.

[0147] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, copper foil may be used. The composite current collector may include a polymeric material substrate and a metal material layer formed on at least one surface of the polymeric material substrate. As an example, the metal material may include at least one of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymeric material substrate may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0148] The negative electrode film is typically formed by coating a negative electrode slurry onto a negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry is usually formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional additives in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to these.

[0149] The negative electrode sheet does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode sheet also includes a conductive undercoat layer (e.g., composed of a conductive agent and an adhesive) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. In some embodiments, the negative electrode sheet of this application also includes a protective layer covering the surface of the negative electrode film layer.

[0150] [Isolation membrane]

[0151] A separator is disposed between the positive and negative electrode plates to provide isolation. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0152] In some embodiments, the material of the separator can be selected from one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0153] [Electrolytes]

[0154] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not specifically limit the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid or gel-like.

[0155] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0156] 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.

[0157] 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.

[0158] 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.

[0159] In some embodiments, the positive electrode, the separator, and the negative electrode can be fabricated into an electrode assembly using a winding process or a stacking process.

[0160] In some embodiments, the battery cell also includes a housing for containing the electrode assembly and electrolyte. The housing of the battery cell can be a rigid housing, such as a hard plastic housing, an aluminum housing, a steel housing, etc. The housing of the battery cell can also be a pouch, such as a pouch-type pouch. The pouch material can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0161] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 2 The example shown is a square-structured battery cell 5.

[0162] In some implementations, refer to Figure 3 The outer casing 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 cover the opening to close the receiving cavity. A positive electrode sheet, a negative electrode sheet, and a separator can be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in a single battery cell 5 can be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0163] The method for preparing the battery cell in this application is well known. In some embodiments, the electrode assembly can be placed in a housing, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, the battery cell is obtained.

[0164] In some embodiments, the battery mentioned in this application refers to a single physical module comprising one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in this application may be a battery module or a battery pack. A battery generally includes a housing for encapsulating one or more battery cells. The housing prevents liquids or other foreign matter from affecting the charging or discharging of the battery cells.

[0165] In some implementations, there can be multiple battery cells in the battery, which can be connected in series, parallel, or a combination thereof. A combination thereof means that multiple battery cells are connected in both series and parallel. Multiple battery cells can be directly connected in series, parallel, or a combination thereof, and then the whole assembly of multiple battery cells is housed in a housing. Alternatively, multiple battery cells can first be connected in series, parallel, or a combination thereof to form a battery module, and then multiple battery modules can be connected in series, parallel, or a combination thereof to form a whole assembly, which is then housed in a housing.

[0166] Figure 4 This is a schematic diagram of battery module 4 as an example. Figure 4As shown, there are multiple battery cells 5, which are connected in series, parallel, or a combination thereof to form a battery module 4. The multiple battery cells 5 in the battery module 4 can be electrically connected through a busbar to achieve the series, parallel, or combination connection. In the battery module 4, the 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 arbitrary manner. Furthermore, the multiple battery cells 5 can be fixed in place using fasteners.

[0167] 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 adjusted according to the application and capacity of the battery pack.

[0168] Figure 5 and Figure 6 This is a schematic diagram of battery pack 1 as an example. Figure 5 and Figure 6 As shown, the battery pack 1 may include a housing and multiple battery modules 4 disposed within the housing. The multiple battery modules 4 in the battery pack 1 can be electrically connected via a busbar component to achieve series, parallel, or mixed connection. The housing includes an upper housing 2 and a lower housing 3. The upper housing 2 covers the lower housing 3, forming a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery housing.

[0169] Electrical appliances

[0170] This application also provides an electrical device, which includes a battery cell provided in this application embodiment. The battery cell is used to provide electrical energy. The battery cell can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0171] As the electrical device, a single battery cell, a battery module containing multiple battery cells, or a battery pack can be selected according to its usage requirements.

[0172] Figure 7 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the device's requirements for high power and high energy density, a battery pack or battery module can be used.

[0173] Another example of an electrical 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.

[0174] Example

[0175] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. 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 this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0176] Example 1

[0177] Preparation of positive electrode active materials

[0178] (1) Nickel sulfate hexahydrate, cobalt sulfate heptahydrate, manganese sulfate monohydrate, and M-containing compounds are added. 1 The salt NaCl was mixed and dissolved in pure water to obtain a precursor solution with a total concentration of 2 mol / L of nickel, cobalt, manganese and M1.

[0179] (2) Add 20L of pure water to a 100L reactor, turn on the stirrer, keep the temperature at 50℃, add an appropriate amount of the first precipitant solution (4mol / L NaOH solution), and adjust the pH of the solution in the reactor to 10-13.

[0180] (3) Under stirring conditions, the precursor solution, the first precipitant solution (4 mol / L NaOH solution), and the first complexing agent solution (2 mol / L ammonia solution) are added to the reactor at a certain rate to allow the nickel salt, cobalt salt, manganese salt, and M-containing... 1 The salt underwent a co-precipitation reaction in the presence of the precipitant and complexing agent, while maintaining the ammonia concentration and pH in the reaction vessel constant during the reaction. After centrifugation, washing, filtration, and drying, a solution containing M was prepared. 1 Precursor seed slurry containing M 1 Precursor seed volume distribution and grain size Dv 1 50 is 3.8μm.

[0181] (4) Add 20L of pure water to a 100L reactor, followed by 10kg of a solution containing M. 1 Add the precursor seed slurry, start stirring, maintain the temperature at 40℃, add an appropriate amount of the second precipitant solution (4mol / L NaOH solution), and adjust the pH of the solution in the reactor to 10-12.

[0182] (5) Under stirring conditions, add M-containing substances to the reactor at a certain rate. 1The precursor seed slurry, the second precipitant solution (1 mol / L NaOH solution), the second complexing agent solution (2 mol / L ammonia solution), and the nickel-cobalt-manganese mixed metal solution (2 mol / L nickel-cobalt-manganese sulfate mixed solution) were prepared. During the reaction, the ammonia concentration and pH in the reactor were kept constant. After a period of reaction, the mixture was centrifuged, washed, filtered, and dried to obtain the ternary cathode material precursor. The chemical formula of the ternary cathode material precursor is [Na...]. 0.02 Ni 0.9 Co 0.06 Mn 0.02 [(OH)2, and the volume distribution particle size Dv of the ternary cathode material precursor] 2 50 is 11.4 μm.

[0183] (6) The ternary cathode material precursor is combined with lithium source Li2CO3 and M 2 After thorough mixing with Zr(SO4)2, the mixture was calcined at 600℃ for 10 h in air, followed by calcination at 800℃ for 6 h to obtain the positive electrode active material. The molar ratio w1 of Li in the lithium source to the total molar ratio of Ni, Co, and Mn in the ternary positive electrode precursor was 1.04:0.98. 2 Source M 2 The ratio w2 of the molar amount of the element to the total molar amount of Ni, Co and Mn elements in the ternary cathode material precursor is 0.02:0.98.

[0184] Preparation of positive electrode sheet

[0185] The positive electrode active material [Li 1.04 Na 0.02 ][Ni 0.9 Co 0.06 Mn 0.02 Zr 0.02 O2, conductive carbon black (Super P), and binder polyvinylidene fluoride (PVDF) are mixed evenly in an appropriate amount of solvent N-methylpyrrolidone (NMP) at a mass ratio of 98:1:1 to obtain a positive electrode slurry. The positive electrode slurry is coated onto the positive electrode current collector aluminum foil, and the positive electrode sheet is obtained through processes such as drying, cold pressing, slitting, and cutting.

[0186] Preparation of negative electrode sheet

[0187] Artificial graphite (anode active material), carbon black (Super P) (conductive agent), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC) (batch ratio 97:1:1:1) are mixed evenly in an appropriate amount of deionized water to obtain a cathode slurry. The cathode slurry is coated onto copper foil (anode current collector), and the cathode sheet is obtained through drying, cold pressing, slitting, and cutting processes.

[0188] Preparation of the separating membrane

[0189] Polypropylene film is used as the separator.

[0190] Preparation of electrolyte

[0191] LiPF6 was dissolved in a solvent prepared by mixing ethylene carbonate, methyl ethyl carbonate, and diethyl carbonate in a volume ratio of 1:1:1 to obtain an electrolyte with a LiPF6 concentration of 1 mol / L.

[0192] Preparation of secondary batteries

[0193] The positive electrode, separator, and negative electrode are stacked and wound in sequence to obtain an electrode assembly. The electrode assembly is placed in an outer packaging, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a secondary battery is obtained.

[0194] Example 2-18

[0195] Based on the preparation process of the positive electrode active material in Example 1, the content of M was adjusted. 1 salt, M 2 Source, w1 to w2, Dv P 50 and Dv 2 At least one of the 50 is used to prepare a positive electrode active material with a predetermined composition and structure, resulting in the positive electrode active materials of Examples 2-18. The preparation of the positive electrode sheet, negative electrode sheet, separator, electrolyte, and secondary battery of Examples 2-18 is the same as that of Example 1.

[0196] Examples 2-4 are based on Example 1, respectively, containing M 1 The salts were replaced with equimolar amounts of MaCl2, KCl, and CaCl2.

[0197] Examples 5-8 are based on Example 1, respectively, containing M 2 Source replaced with M 2 The molar amounts of niobium pentoxide (Nb₂O₅), tantalum pentoxide (Ta₂O₅), tungsten oxide (WO₃), molybdenum oxide (MoO₃), and titanium dioxide (TiO₂).

[0198] Example 10, based on Example 1, respectively, involves Dv 1 50 and Dv 2 50 was adjusted to 1.20μm and 13.2μm.

[0199] Example 11, based on Example 1, respectively, Dv 1 50 and Dv 250 was adjusted to 2.43μm and 10.53μm.

[0200] Example 12, based on Example 1, respectively, Dv 1 50 and Dv 2 50 was adjusted to 3.25μm and 9.75μm.

[0201] Example 13 is based on Example 1, with Dv respectively 1 50 and Dv 2 The value of 50 was adjusted to 3.78μm and 9.18μm.

[0202] Example 14, based on Example 1, involves Dv... 1 50 and Dv 2 50 was adjusted to 4.05μm and 8.55μm.

[0203] In Example 15, the chemical formula of the ternary cathode material precursor is [Na 0.01 Ni 0.6 Co 0.2 Mn 0.15 [(OH)2, w1 is 1.05∶0.95, w2 is 0.05∶0.95.]

[0204] In Example 16, the chemical formula of the ternary cathode material precursor is [Na 0.01 Ni 0.77 Co 0.12 Mn 0.08 [(OH)2, w1 is 1.06∶0.97, w2 is 0.03∶0.97.]

[0205] In Example 17, the chemical formula of the ternary cathode material precursor is [Na] 0.005 Ni 0.82 Co 0.1 Mn 0.06 [(OH)2, w1 is 1.05∶0.98, w2 is 0.02∶0.98.]

[0206] In Example 18, the chemical formula of the ternary cathode material precursor is [Na 0.015 Ni 0.92 Co 0.05 Mn 0.02 (OH)2, w1 is 1.04∶0.99, w2 is 0.01∶0.99.

[0207] The secondary batteries of Comparative Examples 1-5 are similar to those of Example 1, except that Comparative Examples 1-5 use conventional nickel-cobalt-manganese ternary cathode material particles as the cathode active material.

[0208] The chemical formulas, core radii R, shell thickness D, and cell parameters c of the positive electrode active materials of Examples 1-18 and Comparative Examples 1-5 were characterized, and the characterization results are shown in Table 1. The chemical formulas of the positive electrode active materials were characterized by the following steps: the positive electrode active material was dissolved in aqua regia, and elemental analysis was performed by inductively coupled plasma optical emission spectrometry (ICP, Ametek, model: SPECTROARCOSICP-OES) to obtain the proportions of each element. The chemical formula of the positive electrode active material was determined based on the proportions of each element. The core radius R, shell thickness D, and cell parameter c were determined according to the methods described in this application specification.

[0209] Test section

[0210] ambient temperature cycling performance test

[0211] At 25°C, the secondary battery was charged at a constant current of 0.5C to 4.25V, then charged at a constant voltage of 4.25V to the cutoff current of 0.05C, left to rest for 10 minutes, and then discharged at a constant current of 0.5C to 2.8V, left to rest for 5 minutes. This constitutes one charge-discharge cycle. The discharge capacity at this point is recorded as C0. This charge-discharge cycle process is repeated for the same secondary battery, and the discharge capacity C1 of the 300th cycle is recorded. The cycle capacity retention rate P of the battery is recorded. 300 =C1 / C0 × 100%.

[0212] The test results are detailed in Table 1.

[0213]

[0214]

[0215] As can be seen from the test results in Table 1, the positive electrode active material of this application embodiment has a specific structure and elemental composition. Therefore, the positive electrode active material can have high structural stability and can effectively improve the cycle performance of the battery when applied to a secondary battery.

[0216] In contrast, the positive electrode active materials in Comparative Examples 1-5 do not have a core-shell structure, and the positive electrode active material particles do not contain M... 1 Element and M 2 With graded doping of elements, the cycle performance of the battery deteriorates significantly as the nickel content in the positive electrode active material increases. Consequently, the cycle performance of the secondary batteries in Comparative Examples 1-5 is far inferior to that in Examples 1-18.

[0217] For the compounds given but not listed in the examples, since their chemical properties and electrochemical reaction properties are similar to those of the compounds listed in the examples, they are all applicable to the technical solutions of the present invention, and therefore will not be listed here.

[0218] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A positive electrode active material, characterized in that, Including ternary cathode material particles with a core-shell structure, The ternary cathode material particles contain doping element M. 1 and dopant element M 2 Furthermore, based on the total molar amount of transition metal elements in the ternary cathode material particles, the molar percentage of Ni element in the ternary cathode material particles is greater than or equal to 0.

6. Among them, M 1 ionic radius r M1 With lithium ion radius r Li Satisfy: |r M1 -r Li |≤80pm, and M 1 Distributed in the core of the ternary cathode material particles; M 2 Including one or more of Zr, Nb, Ta, W, Mo, Ti, and Ir, and M 2 Distributed in the shell of the ternary cathode material particles; The powder compaction density of the positive electrode active material under 5 tons of pressure is greater than or equal to 3.5 g / cc.

2. The positive electrode active material according to claim 1, characterized in that, The M 1 It includes one or more of Na, Mg, K, and Ca.

3. The positive electrode active material according to claim 1 or 2, characterized in that, The ternary cathode material particles have the general formula [Li 1+a M 1 b ][Ni x Co y Mn z M 2 c O2, where 0.6≤x<1, 0≤y≤0.4, 0≤z≤0.4, 0.05≤a+b≤0.1, 0 <b≤0.05,0<c≤0.1,x+y+z+c=1。 4. The positive electrode active material according to claim 3, characterized in that, 0.01≤b≤0.03,0 <c≤0.08。 5. The positive electrode active material according to any one of claims 1-4, characterized in that, The radius R of the core and the thickness D of the shell satisfy the condition: 0.1 ≤ R / D ≤ 0.

9.

6. The positive electrode active material according to claim 5, characterized in that, 0.4≤R / D≤0.

7.

7. The positive electrode active material according to any one of claims 1-6, characterized in that, The cell parameter c of the positive electrode active material is 14.26 Å-14.32 Å.

8. The positive electrode active material according to claim 7, characterized in that, The cell parameter c of the positive electrode active material is 14.27 Å-14.30 Å.

9. The positive electrode active material according to any one of claims 1-8, characterized in that, If the volume distribution particle size span of the positive electrode active material is SPAN = (Dv90 - Dv10) / Dv50, then SPAN ≥ 1.

1.

10. The positive electrode active material according to claim 9, characterized in that, SPAN ≥ 1.

2.

11. The positive electrode active material according to any one of claims 1-10, characterized in that, The volume distribution particle size Dv90 of the positive electrode active material is 15μm-25μm; and / or The volume distribution particle size Dv50 of the positive electrode active material is 6μm-14μm; and / or The volume distribution particle size Dv10 of the positive electrode active material is 1μm-5μm.

12. The positive electrode active material according to claim 11, characterized in that, The volume distribution particle size Dv90 of the positive electrode active material is 18μm-22μm; and / or The volume distribution particle size Dv50 of the positive electrode active material is 8μm-12μm; and / or The volume distribution particle size Dv10 of the positive electrode active material is 2μm-4μm.

13. The positive electrode active material according to any one of claims 1-12, characterized in that, The powder compaction density of the positive electrode active material under 5 tons of pressure is 3.5 g / cc-3.7 g / cc.

14. A method for preparing a positive electrode active material, characterized in that, include: A precursor solution is provided, the precursor solution comprising a nickel salt, a cobalt salt, a manganese salt, and an M-containing salt. 1 A mixed solution of salts, wherein M 1 ionic radius r M1 With lithium ion radius r Li Satisfy: |r M1 -r Li ≤80pm; The preparation of seed crystal slurry includes uniformly mixing the precursor solution with a first precipitant and a first complexing agent to make the nickel salt, cobalt salt, manganese salt, and M-containing... 1 The salt undergoes a co-precipitation reaction in the presence of the first precipitant and the first complexing agent to obtain a salt containing M. 1 Precursor seed slurry; The preparation of a ternary cathode material precursor includes mixing the seed slurry with a nickel-cobalt-manganese mixed metal solution, a second precipitant, and a second complexing agent, and reacting them to obtain the ternary cathode material precursor. The preparation of positive electrode active materials includes reacting the ternary positive electrode material precursor with a lithium source and M... 2 After the source is mixed evenly, it is calcined to obtain the positive electrode active material, wherein M 2 Including one or more of Zr, Nb, Ta, W, Mo, Ti, and Ir, The positive electrode active material includes ternary positive electrode material particles with a core-shell structure, and the ternary positive electrode material particles contain dopant element M. 1 and dopant element M 2 Based on the total molar amount of transition metal elements in the ternary cathode material particles, the molar percentage of Ni element in the ternary cathode material particles is greater than or equal to 0.6; wherein, M 1 Distributed in the core of the ternary cathode material particles, and M 2 Distributed in the shell of the ternary cathode material particles; the compacted density of the cathode active material powder under 5 tons of pressure is greater than or equal to 3.5 g / cc.

15. The method according to claim 14, characterized in that, The M-containing 1 Salts containing M 1 One or more of the elements' sulfates, nitrates, carbonates, oxalates, and chlorides.

16. The method according to claim 14 or 15, characterized in that, The first precipitant and the second precipitant each independently comprise one or more of sodium hydroxide, sodium carbonate, potassium carbonate, and potassium hydroxide; and / or The first complexing agent and the second complexing agent each independently comprise one or more of ammonia, ammonium chloride, ammonium sulfate, urea, citric acid, and EDTA; and / or The pH of the coprecipitation reaction is 11.5-14, and the reaction temperature is 50℃-80℃; and / or The M-containing 1 Precursor seed volume distribution and grain size Dv 1 50 represents 1μm-5μm.

17. The method according to any one of claims 14-16, characterized in that, The M 2 The source includes M 2 One or more of the following: sulfate, carbonate, oxide, hydroxide, nitrate, silicate, acetate, and oxalate of an element.

18. The method according to any one of claims 14-17, characterized in that, In the step of preparing the ternary cathode material precursor, the pH of the reaction is 10-12, and the reaction temperature is 30℃-60℃; and / or Volume distribution and particle size Dv of ternary cathode material precursor 2 50 is 5μm-15μm.

19. The method according to any one of claims 14-18, characterized in that, The lithium source includes one or more of LiOH·H2O, Li2CO3, Li2SO4, LiNO3, LiC2O4, and CH3COOLi.

20. The method according to claim 19, characterized in that, The molar amount n of Li element contained in the lithium source Li It can satisfy 1.0≤n Li / n Me ≤1.2, where n Me This indicates the total molar amount of Ni, Co, and Mn elements in the ternary cathode material precursor.

21. The method according to any one of claims 14-20, characterized in that, The ternary cathode material precursor is combined with a lithium source and M. 2 After the source is mixed evenly, calcination is performed to obtain the positive electrode active material, including: The ternary cathode material precursor is combined with a lithium source and M 2 After the source is mixed evenly, it is calcined at 500℃-700℃ for 8h-12h, and then calcined at 600℃-900℃ for 4h-8h to obtain the positive electrode active material. The calcination atmosphere is an oxygen-containing atmosphere.

22. A positive electrode sheet, comprising a positive current collector and a positive electrode film layer located on at least one side of the positive current collector, the positive electrode film layer comprising a positive electrode active material according to any one of claims 1-13, or a positive electrode active material prepared by the method according to any one of claims 14-21.

23. A battery comprising a positive electrode according to claim 22.

24. An electrical device comprising the battery according to claim 23.

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