Positive electrode active material, method for manufacturing the same, positive electrode plate containing the same, battery, and power consumption device

Abstract

This application provides a positive electrode active material, a method for producing the same, a positive electrode plate containing the same, a battery, and a power consumption device, wherein the positive electrode active material comprises a layered transition metal oxide represented by formula (I), each parameter being as defined herein, and the positive electrode active material contains element K, with the content of element K gradually decreasing from the particle surface to the interior of the particle. [Case 1] JPEG2026513161000021.jpg5170

Description

[Technical Field]

[0001] This application relates to a positive electrode active material, a method for producing the same, a positive electrode plate containing the same, a battery, and a power consumption device. [Background technology]

[0002] In recent years, batteries have been widely used in energy storage and power systems such as hydroelectric, thermal, wind, and solar power plants, as well as in multiple fields such as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. Currently, lithium-ion batteries still occupy a core position in the battery market, but at the same time, lithium-ion batteries also face significant challenges, such as the increasing scarcity of lithium resources. Sodium resources are far more abundant and widely distributed than lithium resources, and their cost is much lower than lithium, making sodium-ion batteries a new generation of electrochemical systems with a high potential to replace lithium-ion batteries. The positive electrode active material is a crucial element that affects the performance of sodium-ion batteries, and due to constraints in the manufacturing process, relatively high levels of free alkaline substances are often present on the surface of the positive electrode active material, which affects the performance of sodium-ion batteries. Therefore, effective technical means to improve the performance of the positive electrode active material are needed. The above description is for the purpose of providing background art information related to this application and does not necessarily constitute prior art. [Overview of the Initiative]

[0003] This application provides a positive electrode active material, a method for producing the same, a positive electrode plate containing the same, a battery, and a power consumption device, which can stabilize the crystal structure of the positive electrode active material and provide the positive electrode active material with good cycle performance and rate performance.

[0004] A first aspect of this application provides a positive electrode active material comprising a layered transition metal oxide represented by formula (I), [ka] x > 0.5, 0 < y < 0.5, 0 < a ≤ 1, 0 ≤ b ≤ 1 / 3, 0 ≤ c ≤ 1 / 3, 1.9 ≤ m ≤ 2, 0 ≤ n ≤ 0.1, M contains one or more of Mn, Fe, Co, Ni, Cu, A contains one or more metallic elements of Group IA, IIA, IIIA, IVA, VA, IIB, IVB, VB, VIB, B contains one or more non-metallic elements of Group IIIA, IVA, VA, VIA, Q contains one or more non-metallic elements of Group VA, VIIA, the positive electrode active material contains K element, and the content of K element decreases gradually from the particle surface to the particle interior of the positive electrode active material.

[0005] By introducing a K element having a feature that the content decreases gradually from the particle surface to the particle interior in the positive electrode active material, not only can the crystal structure of the positive electrode active material be stabilized, but also the positive electrode active material can be provided with good cycle performance and rate performance.

[0006] In any embodiment, a region formed by extending 0.05 L from the particle surface to the particle interior of the positive electrode active material is referred to as the surface layer region of the positive electrode active material, L refers to the length of the long axis of the positive electrode active material particles, and the mass of K element in the surface layer region of the positive electrode active material is 50% to 95%, and optionally 70% to 90% of the total mass of K element in the positive electrode active material.

[0007] The content of K element in the positive electrode active material exhibits a feature of gradually decreasing from the particle surface to the particle interior, and K element is mainly distributed in the surface layer region of the positive electrode active material, thereby effectively reducing the stress in the cycle process of the battery, thereby reducing the generation of microcracks, and furthermore, + the supporting effect of K can be better exerted, thereby stabilizing the crystal structure of the positive electrode active material, improving the interfacial stability, improving the stability of the crystal structure, reducing the probability of crystal structure collapse or irreversible conversion after a large amount of sodium desorption from the positive electrode active material in the later stage of charging, and furthermore improving the cycle performance and / or rate performance of the battery.

[0008] In any of these embodiments, the positive electrode active material comprises one or more of the O3 phase, P2 phase, and P3 phase.

[0009] In any embodiment, the positive electrode active material contains an O3 phase, and in the peak separation pattern of the X-ray diffraction pattern of the positive electrode active material, there are two diffraction peaks within the range of 2θ from 16.0° to 16.7°, with the diffraction peak located between 2θ from 16.0° to 16.3° being designated as the first peak, and the diffraction peak located between 2θ from 16.3° to 16.7° being designated as the second peak, and the ratio of the peak intensity of the first peak to the peak intensity of the second peak is 0.1:1 or less, and selectively 0.076:1 or less. This indicates that the main structure of the O3 phase of the positive electrode active material is well maintained, and the positive electrode active material contains only an O3 phase with a small amount of lattice strain.

[0010] In any embodiment, the positive electrode active material includes an O3 phase, and the X-ray diffraction pattern of the positive electrode active material includes diffraction peaks on the (104) crystal plane where 2θ is between 41.5° and 42.5° and diffraction peaks on the (015) crystal plane where 2θ is between 44.5° and 45.5°, and the ratio of the peak intensity of the diffraction peak on the (104) crystal plane to the peak intensity of the diffraction peak on the (015) crystal plane is greater than 10:1. This indicates that the layered structure of the positive electrode active material is relatively stable, crystal plane slippage is unlikely to occur, and aggregation of transition metal elements is unlikely to occur.

[0011] In any of the embodiments, A comprises one or more elements from among Li, Ti, Zr, Sb, Nb, Mg, Ca, Mo, Zn, Cr, W, Bi, Sn, Ge, Al, Ba, Sr, and V.

[0012] In any embodiment, B comprises one or more elements from Si, P, B, S, and Se.

[0013] In any embodiment, Q comprises one or more elements selected from F, Cl, and N.

[0014] In any of the embodiments, x ≥ 2 / 3.

[0015] In any of the embodiments, 0.012 ≤ y ≤ 0.05. When the content of K element in the positive electrode active material is within the above range, the surface structure of the positive electrode active material can be more stabilized, and the probability of crystal structure collapse or irreversible conversion after a large amount of sodium desorption from the positive electrode active material in the later stage of charging can be reduced. At the same time, the positive electrode active material can have a relatively high gram capacity, good cycle performance and rate performance.

[0016] In any of the embodiments, 0 ≤ b ≤ 1 / 3, 0 ≤ c ≤ 1 / 3, and 0 < b + c ≤ 1 / 3.

[0017] In any of the embodiments, the positive electrode active material includes a layered transition metal oxide represented by formula (I-1),

Chemical formula

[0018] In any of the embodiments, 0 < p ≤ 2 / 3.

[0019] In any of the embodiments, 0 < q ≤ 1 / 3.

[0020] In any of the embodiments, 0 < a - p - q ≤ 1 / 3.

[0021] In any of the embodiments, the content of the free alkaline substance on the surface of the positive electrode active material is 0.2 - 20 wt%, and optionally 0.5 - 1.4 wt%. Since the content of the free alkaline substance on the surface of the positive electrode active material is relatively low, the positive electrode active material can have relatively high interfacial stability, which is advantageous for improving the cycle performance and / or rate performance of the battery, and is also advantageous for improving the processing performance of the positive electrode slurry and the battery.

[0022] In any of the embodiments, the pH of the positive electrode active material is 11.5-13.5, and selectively 11.8-12.6. Because the pH of the positive electrode active material is relatively low, it can be given relatively high interfacial stability, which is advantageous in improving the battery's cycle performance and / or rate performance, and further advantageous in improving the processing performance of the positive electrode slurry and the battery.

[0023] In any of the embodiments, the form of the positive electrode active material includes one or more of spherical single crystals, sheet-like single crystals, and spherical polycrystalline materials.

[0024] In any of the embodiments, the volume-distributed particle size Dv50 of the positive electrode active material is 3-15 μm, and selectively 4-9 μm. When the volume-distributed particle size Dv50 of the positive electrode active material is within the above range, it can have a relatively high gram capacity and a relatively high compaction density, and furthermore, it can have good ion transport capacity and rate performance.

[0025] A second aspect of this application provides a method for producing a positive electrode active material, the method comprising the steps of providing an initial positive electrode active material comprising a sodium-containing layered transition metal oxide, and cleaning the initial positive electrode active material using an alkaline cleaning solution, wherein the alkaline cleaning solution is K + The steps include a step of including and a step of drying after the cleaning is completed to obtain a positive electrode active material, wherein the positive electrode active material comprises a layered transition metal oxide represented by formula (I), [ka] x > 0.5, 0 < y < 0.5, 0 < a ≤ 1, 0 ≤ b ≤ 1 / 3, 0 ≤ c ≤ 1 / 3, 1.9 ≤ m ≤ 2, 0 ≤ n ≤ 0.1, M contains one or more of Mn, Fe, Co, Ni, Cu, A contains one or more metal elements of Group IA, IIA, IIIA, IVA, VA, IIB, IVB, VB, VIB, B contains one or more non-metal elements of Group IIIA, IVA, VA, VIA, Q contains one or more non-metal elements of Group VA, VIIA, the positive electrode active material contains K element, and the content of K element gradually decreases from the particle surface to the particle interior of the positive electrode active material.

[0026] The positive electrode active material obtained by the manufacturing method of this application has a relatively low pH, a relatively low content of surface-free alkaline substances, and further has a K element whose content gradually decreases from the particle surface to the particle interior. Thereby, not only can the crystal structure of the positive electrode active material be stabilized, but also the positive electrode active material can be given good cycle performance and rate performance.

[0027] In any embodiment, in the step of washing the initial positive electrode active material using an alkaline cleaning solution, the washing temperature is 35°C or lower, and optionally 20°C - 30°C. When the washing temperature is within the above range, the Na + / H + exchange rate can be further reduced, and interlayer sodium elution can be decreased.

[0028] In any embodiment, in the step of washing the initial positive electrode active material using an alkaline cleaning solution, the washing time is 60 min or less, and optionally 5 - 20 min. When the washing time is within the above range, the Na + / H + exchange can be further reduced, and interlayer sodium elution can be decreased.

[0029] In any embodiment, the pH of the alkaline cleaning solution is 12 or higher, and optionally 13 - 14. When the pH of the alkaline cleaning solution is within the above range, the Na+ / H + The exchange can be further reduced, and the interlayer sodium elution can be decreased.

[0030] In any of the embodiments, the solute in the alkaline cleaning solution contains one or more of potassium hydroxide, potassium carbonate, and potassium hydrogen carbonate.

[0031] In any of the embodiments, the solvent in the alkaline cleaning solution contains one or more of water, alcohol solvents, and ester solvents, and selectively contains water.

[0032] In any of the embodiments, the alkaline cleaning solution further contains Na + By including Na + in the alkaline cleaning solution, it is possible to replenish Na + and improve the capacity, and further reduce the Na + / H + exchange, reduce the interlayer sodium elution, and enable the cathode active material to better retain its original layered structure.

[0033] In any of the embodiments, the molar ratio of Na + to K + is 1:(0.1 - 10), and selectively 1:(0.2 - 2).

[0034] In any of the embodiments, the manufacturing method further includes a step of performing a sintering process on the initial cathode active material after the cleaning is completed, and obtaining the cathode active material after completion.

[0035] Sintering can stabilize the surface of the material, re-stabilize the surface that has become unstable due to cleaning, thereby repairing surface defects and reducing pores. Sintering further replaces the surface layer of K + with Na +By stably positioning the support, it can better perform its function as a pillar, improve rate performance, and reduce the probability of crystal structure collapse or irreversible transformation occurring after a large amount of sodium desorption of the positive electrode active material in the later stages of charging. Sintering further removes K remaining on the material surface. + Further diffusion into the particle interior allows the K element content to exhibit a more pronounced characteristic of gradual decrease from the particle surface to the interior.

[0036] In any of the embodiments, the sintering temperature is 300°C–600°C, and selectively 450°C–550°C.

[0037] In any of the embodiments, the sintering time is 10 hours or less, and selectively between 3 and 8 hours.

[0038] In any of the embodiments, the sintering atmosphere is an oxygen-containing atmosphere, and more selectively, the volume fraction of oxygen gas in the sintering atmosphere is 15%-40%. Sintering in an oxygen-containing atmosphere can stabilize the surface structure of the material, re-reacting surface sodium that has become unstable due to cleaning with oxygen to stabilize it, thereby repairing surface defects and reducing pores, which is advantageous in improving the cycle performance and / or rate performance of the battery.

[0039] By adjusting one or more parameters such as sintering temperature, sintering time, concentration of alkaline cleaning solution, cleaning temperature, and cleaning time within the above range, the content of element K can be gradually reduced from the particle surface to the interior of the positive electrode active material, and the uniform distribution characteristics of element K in the positive electrode active material can be avoided, while also allowing adjustment of the distribution region of element K.

[0040] A third aspect of this application provides a positive electrode plate comprising a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, wherein the positive electrode film layer comprises a positive electrode active material of the first aspect of this application or a positive electrode active material manufactured by the manufacturing method of the second aspect of this application.

[0041] In any of the embodiments, the content of the positive electrode active material in the positive electrode film layer is 50 wt% to 99 wt%, and more selectively 85 wt% to 99 wt%, based on the total weight of the positive electrode film layer.

[0042] A fourth aspect of this application provides a battery including the positive electrode plate of the third aspect of this application.

[0043] A fifth aspect of this application provides a power consumption device which includes a battery according to the fourth aspect of this application.

[0044] The power consumption device of this application includes a battery according to this application and therefore has at least the same advantages as the aforementioned battery. [Brief explanation of the drawing]

[0045] To more clearly explain the technical concept of the embodiments of this application, the following is a brief introduction to the drawings that may be used in the embodiments of this application. Obviously, the drawings described below represent only a few embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without expending any creative effort. [Figure 1] This is a schematic diagram of one embodiment of the battery cell of this application. [Figure 2] Figure 1 is a schematic exploded view of an embodiment of the battery cell. [Figure 3] This is a schematic diagram of one embodiment of the battery module of this application. [Figure 4] This is a schematic diagram of one embodiment of the battery pack of this application. [Figure 5] Figure 4 is a schematic exploded view of an embodiment of the battery pack shown. [Figure 6] This is a schematic diagram of one embodiment including a power consumption device that uses the battery of the present application as a power source. [Figure 7] These are the X-ray diffraction patterns of the positive electrode active materials produced in Example 1, Comparative Example 1, and Comparative Example 3. [Figure 8]These are cycle curve diagrams of the button-type batteries manufactured in Example 1, Comparative Example 1, and Comparative Example 3.

[0046] In drawings, the drawings are not always drawn to the actual scale. [Modes for carrying out the invention]

[0047] Hereinafter, embodiments specifically disclosing the positive electrode active material, its manufacturing method, and positive electrode plate, battery, and power consumption device contained herein will be described in detail with appropriate reference to the drawings. However, unnecessary detailed explanations may be omitted. For example, detailed explanations of well-known matters and repeated explanations of structures that are actually the same may be omitted. This is to avoid the following explanation becoming unnecessarily redundant and to make it easily understandable to those skilled in the art. The drawings and the following explanation are provided to enable those skilled in the art to fully understand this application and are not intended to limit the topics described in the claims.

[0048] The “range” disclosed in this application is limited in the form of a lower limit and an upper limit, and a given range is limited by selecting one lower limit and one upper limit, which define the boundary of a particular range. The range thus limited may or may not include the limit value, and any combination is possible, that is, any lower limit may be combined with any upper limit to form a range. For example, if the ranges 60-120 and 80-110 are listed for a particular parameter, it is understood that the ranges 60-110 and 80-120 are also conceivable. Furthermore, if the minimum range values ​​are listed as 1 and 2, and the maximum range values ​​are listed as 3, 4 and 5, then the ranges 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5 are all conceivable. In this application, unless otherwise specified, the numerical range “ab” represents an abbreviated expression for any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have already been listed in this specification, and "0-5" is simply a shortened representation of combinations of these numbers. Also, expressing a parameter as an integer ≥ 2 is equivalent to disclosing that this parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0049] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions, and such technical solutions should be considered to be included in the disclosures of this application.

[0050] Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical concepts, and such technical concepts should be considered to be included in the disclosures of this application.

[0051] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, the fact that the method includes steps (a) and (b) means that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, the fact that the method mentioned above may further include step (c) means that step (c) may be added to the method in any order, for example the method may include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), and so on.

[0052] Unless otherwise specified, the terms “includes” and “inclusion” as used in this application may represent an open or closed configuration. For example, the terms “includes” and “inclusion” may mean that other components not listed may be included or inclusion, or that only the listed components may be included or inclusion.

[0053] 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, any of the following conditions satisfy "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) but B is true (or exists); and both A and B are true (or exist).

[0054] In this application, the terms "multiple" and "multiple types" refer to two or more.

[0055] Unless otherwise specified, terms used in this application have the meanings commonly understood by those skilled in the art.

[0056] Unless otherwise specified, the numerical values ​​of each parameter referred to in this application can be measured using various commonly used test methods in the art, for example, according to the test methods given in the embodiments of this application. Unless otherwise specified, the test temperature for each parameter is 25°C.

[0057] The batteries referred to in the embodiments of this application may be a single physical module comprising one or more battery cells to provide higher voltage and capacity. For example, the batteries referred to in this application may include battery cells, battery modules, or battery packs.

[0058] A battery cell is the smallest unit that makes up a battery and can independently realize the functions of charging and discharging. A battery cell may have a cylindrical, flattened, rectangular parallelepiped, or other shape, and the embodiments of this application are not limited to these. Figure 1 shows a rectangular parallelepiped battery cell 5 as an example.

[0059] When there are multiple battery cells, the multiple battery cells are connected in series, parallel, or series-parallel via busbar members. In some embodiments, the battery may be a battery module, and when there are multiple battery cells, the multiple battery cells are arranged and fixed to form a single battery module. In some embodiments, the battery may be a battery pack, which includes a housing and battery cells, and the battery cells or battery modules are housed within the housing. In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least part of the vehicle's bottom plate, or a portion of the housing may be at least part of the vehicle's cross members and side members.

[0060] In some embodiments, the battery may be an energy storage device. The energy storage device may include an energy storage container, an energy storage electrical cabinet, and the like.

[0061] The battery cells according to the embodiments of this application include, but are not limited to, sodium-ion battery cells, sodium metal battery cells, and sodium metal battery cells without a negative electrode.

[0062] A battery cell generally includes an electrode assembly. The electrode assembly generally includes a positive electrode plate, a negative electrode plate, and a separator located between the positive and negative electrode plates. The electrode assembly may have a wound structure or a laminated structure, and the embodiments of this application are not limited thereto.

[0063] The battery cell may further include an outer casing, which may be used to package the electrode assembly and electrolyte. The outer casing may be a rigid case, such as a rigid plastic case, an aluminum case, or a steel case. The outer casing may be a pouch, such as a bag-shaped pouch. The material of the pouch may be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), or polybutylene succinate (PBS).

[0064] In some embodiments, as shown in Figure 2, the casing may include a case 51 and a cover plate 53. The case 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and side plates surround and form a housing cavity. The case 51 has an opening that communicates with the housing cavity, and the cover plate 53 is used to cover the opening and seal the housing cavity. The electrode assembly 52 is packaged in the housing cavity. The number of electrode assemblies 52 included in the battery cell 5 may be one or more and can be adjusted according to the requirements.

[0065] In some embodiments, battery cells may be assembled into battery modules, and the number of battery cells included in a battery module may be multiple, with the specific number being adjusted according to the application and capacity of the battery module. Figure 3 is a schematic diagram of an example battery module 4. As shown in Figure 3, in the battery module 4, multiple battery cells 5 may be arranged sequentially along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, these multiple battery cells 5 may be fixed by fasteners.

[0066] Selectively, the battery module 4 may further include a housing having a housing space, in which a plurality of battery cells 5 are housed.

[0067] In some embodiments, the battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0068] Figures 4 and 5 are schematic diagrams of an example battery pack 1. As shown in Figures 4 and 5, the battery pack 1 may include a housing and a plurality of battery modules 4 installed inside the housing. The housing includes an upper housing 2 and a lower housing 3, and the upper housing 2 is used to cover the lower housing 3 and to form a sealed space for housing the battery modules 4. The plurality of battery modules 4 may be arranged in the housing in any manner.

[0069] Sodium batteries generally employ sodium-containing layered transition metal oxides as the positive electrode active material. These materials have relatively poor interfacial stability, and a high-temperature sintering process is generally required when manufacturing the positive electrode active material. In order to improve yield and compensate for the volatilization of high-temperature sintered sodium during the manufacturing process, the amount of sodium source added is generally excessive. As a result, after the high-temperature sintering process is completed, some of the sodium source remains on the surface of the positive electrode active material and reacts with moisture and CO2 in the air to form free alkaline substances such as NaOH and Na2CO3. These free alkaline substances make the positive electrode slurry more prone to gelling or hardening, affecting the coating performance of the positive electrode slurry and the performance of the battery. Alkaline substances such as Na2CO3 have relatively poor thermal stability, are prone to decomposition and gas generation under high pressure, and do not possess electrochemical activity. If the content is too high, it inhibits the transport of sodium ions. Furthermore, after the high-temperature sintering process is completed, free alkaline substances such as NaOH and Na2CO3 inevitably form on the surface of the positive electrode active material. If these free alkaline substances are not removed, they will continue to react with moisture and CO2 in the air as well as the electrolyte, further inhibiting the transport of sodium ions and causing the desorption of some sodium from the crystal structure of the positive electrode active material. This leads to poor stability of the crystal structure, making irreversible changes to the crystal structure more likely, which in turn affects the capacity of the positive electrode active material, the manufacturing process of the battery, and the performance of the battery.

[0070] The surface modification technologies currently in use mainly include coating modification and cleaning modification.

[0071] Coating modification generally involves coating the surface of the positive electrode active material with a non-active material. This often leads to a decrease in the gram capacity of the positive electrode active material, a deterioration in its ion transport capacity, and further deterioration of its cycle performance and rate performance.

[0072] The cleaning process mainly involves two types: one is cleaning with water or an acidic solution, and the other is cleaning with an organic solvent. Cleaning with water or an acidic solution has good application effects in lithium batteries and can effectively reduce the content of free alkaline substances (mainly LiOH, Li2CO3, etc.) on the surface of lithium-containing positive electrode active materials, especially ternary materials (e.g., NCM). However, the positive electrode active materials of sodium batteries, especially sodium-containing layered transition metal oxides, are very sensitive to both water and acid, and in the process of cleaning with water or an acidic solution, Na + / H + Exchange occurs very easily, which reduces the amount of sodium in the lattice, worsening the stability of the crystal structure and making it more susceptible to irreversible transformations. Even when washed with organic solvents, Na + / H + Exchange occurs, which reduces the lattice sodium of the positive electrode active material, worsening the stability of the crystal structure, making it more susceptible to irreversible changes in the crystal structure, and the cleaning process with organic solvents is complex and relatively expensive.

[0073] In view of the above problems, the inventors of this application have, through research, provided a potassium ion-doped cathode active material that has high crystal structure stability and good cycle performance and rate performance.

[0074] The positive electrode active material according to the embodiments of this application comprises a layered transition metal oxide represented by formula (I), [ka] x > 0.5, 0 < y < 0.5, 0 < a ≤ 1, 0 ≤ b ≤ 1 / 3, 0 ≤ c ≤ 1 / 3, 1.9 ≤ m ≤ 2, 0 ≤ n ≤ 0.1, M contains one or more of Mn, Fe, Co, Ni, Cu, A contains one or more metal elements of Group IA, IIA, IIIA, IVA, VA, IIB, IVB, VB, VIB, B contains one or more non-metal elements of Group IIIA, IVA, VA, VIA, Q contains one or more non-metal elements of Group VA, VIIA, the positive electrode active material contains K element, and the content of K element gradually decreases from the particle surface to the particle interior of the positive electrode active material.

[0075] K + has a relatively large ionic radius (about 0.138 nm), after it occupies a part of the Na position on the surface layer of the positive electrode active material, it can increase the interlayer spacing of the positive electrode active material, thereby enabling the positive electrode active material to have good rate performance. + After a large amount of sodium desorption occurs in the positive electrode active material in the later stage of charging, the stability of the crystal structure deteriorates, and an irreversible conversion from a layered structure to a rock salt phase structure is likely to occur. After introducing K into the positive electrode active material, K can play a supporting role, stabilize the crystal structure of the positive electrode active material, improve the interface stability, and can also improve the stability of the crystal structure, reduce the probability of crystal structure collapse or irreversible conversion after a large amount of sodium desorption occurs in the positive electrode active material in the later stage of charging, and further improve the cycle stability of the positive electrode active material.

[0076] After a large amount of sodium desorption occurs in the positive electrode active material in the later stage of charging, the stability of the crystal structure deteriorates, and an irreversible conversion from a layered structure to a rock salt phase structure is likely to occur. K + After introducing it into the positive electrode active material, K + can play a supporting role, stabilize the crystal structure of the positive electrode active material, improve the interface stability, and can also improve the stability of the crystal structure, reduce the probability of crystal structure collapse or irreversible conversion after a large amount of sodium desorption occurs in the positive electrode active material in the later stage of charging, and further improve the cycle stability of the positive electrode active material.

[0077] The content of K element in the positive electrode active material exhibits the characteristic of gradually decreasing from the particle surface to the particle interior, thereby effectively reducing the stress in the cycle process of the battery, reducing the generation of microcracks, and enabling the battery using this positive electrode active material to have a long cycle life.

[0078] Therefore, by introducing K element which has the feature that the content gradually decreases from the particle surface to the particle interior in the positive electrode active material, not only can the crystal structure of the positive electrode active material be stabilized, but also the positive electrode active material can be provided with good cycle performance and rate performance.

[0079] Unless otherwise specified, in the chemical formula of the positive electrode active material, when M is two or more elements, the limitation of the above a numerical range is not only the limitation of the stoichiometric number for each type of element that becomes M, but also the limitation of the sum of the stoichiometric numbers of each element that becomes M. For example, when M is two or more elements M1, M2... Mn, the stoichiometric numbers a1, a2... an of M1, M2... Mn respectively need to be within the numerical range limited for a of this application, and the sum of a1, a2... an also needs to be within this numerical range. Similarly, in the examples of this application, when other elements are two or more elements, the limitation of the numerical range of their stoichiometric numbers also has the above meaning.

[0080] M contains one or more elements selected from Mn, Fe, Co, Ni, and Cu.

[0081] The layered transition metal oxide may be a single-component material or a multi-component material. The "single-component material" refers to a material containing only one transition metal M. For example, the transition metal M contains one of Mn, Fe, Co, Ni, and Cu. The "multi-component material" refers to a material containing at least two transition metals M. For example, the transition metal M contains at least two of Mn, Fe, Co, Ni, and Cu, such as a combination of Mn and Fe, a combination of Mn, Fe, and Ni, a combination of Mn, Fe, and Cu, etc.

[0082] In some embodiments, the positive electrode active material may include a layered transition metal oxide represented by formula (I-1).

Chemical formula

[0083] In some embodiments, 0 <p≦2 / 3である。

[0084] In some embodiments, 0 <q≦1 / 3である。

[0085] In some embodiments, 0 ≤ apq ≤ 1 / 3, and selectively, 0 <a-p-q≦1 / 3である。

[0086] In some embodiments, x may be ≥ 2 / 3, ≥ 0.7, ≥ 0.8, ≥ 0.9, ≥ 0.92, ≥ 0.94, or ≥ 0.96.

[0087] In some embodiments, 0.001≦y<0.5, and selectively, 0.001≦y≦0.4, 0.001≦y≦0.3, 0.001≦y≦0.2, 0.001≦y≦0.1, 0.001≦y≦0.05, 0.005≦y≦0.05, 0.008≦y≦0.05, and 0.012≦y≦0.05. When the K element content in the positive electrode active material is within the above range, the surface structure of the positive electrode active material can be better stabilized, reducing the probability of crystal structure collapse or irreversible transformation occurring after a large amount of sodium desorption of the positive electrode active material in the later stages of charging, and at the same time, the positive electrode active material can be given a relatively high gram capacity and good cycle performance and rate performance. If the K element content is too high, the K element does not provide capacity, thus reducing the gram capacity of the positive electrode active material, and too much K + Na + After occupying the position, further Na + This hinders the movement of the battery and affects its cycle performance and rate performance.

[0088] In some embodiments, b is 0.

[0089] In some embodiments, 0 <b≦1 / 3である。

[0090] In some embodiments, c is 0.

[0091] In some embodiments, 0 < c ≤ 1 / 3.

[0092] In some embodiments, b is 0 and c is 0.

[0093] In some embodiments, 0 < b ≤ 1 / 3 and 0 < c ≤ 1 / 3.

[0094] In some embodiments, 0 ≤ b ≤ 1 / 3, 0 ≤ c ≤ 1 / 3, and 0 < b + c ≤ 1 / 3. For example, b is 0 and 0 < c ≤ 1 / 3, or c is 0 and 0 < b ≤ 1 / 3, or 0 < b < 1 / 3, 0 < c < 1 / 3, and 0 < b + c ≤ 1 / 3.

[0095] When the total content of element A and element B is within an appropriate range, it contributes to further improving the cycle performance and / or rate performance of the battery.

[0096] In some embodiments, A may include one or more elements selected from Li, Ti, Zr, Sb, Nb, Mg, Ca, Mo, Zn, Cr, W, Bi, Sn, Ge, Al, Ba, Sr, V.

[0097] In some embodiments, B may include one or more elements selected from Si, P, B, S, Se.

[0098] In some embodiments, n is 0.

[0099] In some embodiments, 0 < n ≤ 0.1. When the content of element Q is within an appropriate range, it contributes to further improving the cycle performance and / or rate performance of the battery.

[0100] In some embodiments, Q may include one or more elements selected from F, Cl, N.

[0101] The content of each element in the positive electrode active material can be detected by inductively coupled plasma optical emission spectrometry (ICP) referring to EPA 6010D - 2014.

[0102] In some embodiments, the region extending 0.05 L from the particle surface to the interior of the positive electrode active material is referred to as the surface region of the positive electrode active material, where L is the length of the long axis of the positive electrode active material particle, and the mass of element K in the surface region of the positive electrode active material is 50% to 95% of the total mass of element K in the positive electrode active material, selectively 70% to 95%, 75% to 95%, 80% to 95%, 83% to 95%, 70% to 92%, 75% to 92%, 80% to 92%, 83% to 92%, 70% to 90%, 75% to 90%, 80% to 90%, and 83% to 90%.

[0103] The K element content in the positive electrode active material exhibits a characteristic of gradually decreasing from the particle surface towards the interior of the particle, and the K element is mainly distributed in the surface region of the positive electrode active material, thereby effectively reducing stress during the battery cycle process, and thereby reducing the occurrence of microcracks, and furthermore, K + This allows the support function to be better utilized, thereby stabilizing the crystal structure of the positive electrode active material, improving interfacial stability, enhancing the stability of the crystal structure, reducing the probability of crystal structure collapse or irreversible transformation occurring after a large amount of sodium is removed from the positive electrode active material in the later stages of charging, and further improving the battery's cycle performance and / or rate performance.

[0104] The ratio of the mass of K elements in the surface region of the positive electrode active material to the total mass of K elements in the positive electrode active material can be obtained by examining cross-sectional images of the positive electrode active material.

[0105] The cross-sectional image of the positive electrode active material includes a cross-sectional image passing through the center of the positive electrode active material particle. The "center of the particle" refers to the area within a radius extending 0.1 μm from the geometric center of the particle toward the particle surface.

[0106] The length of the long axis of a positive electrode active material particle refers to the maximum value at which a line connecting two points on the particle surface passes through the geometric center of the particle.

[0107] A cross-section of the positive electrode active material can be prepared using a cross-sectional polishing machine (e.g., the IB-09010 CP type argon ion cross-sectional polishing machine from JEOL Japan), then the cross-section of the positive electrode active material can be scanned using a scanning electron microscope (e.g., the Sigma 300 type scanning electron microscope from ZEISS Germany) referring to JY / T010-1996, and then detected using inductively coupled plasma emission spectroscopy (ICP).

[0108] The ratio of the mass of K element in the surface region (a region extending 0.05 L inward from the edge of the particle in the cross-sectional image, where L is the length of the long axis of the positive electrode active material particle) in the obtained cross-sectional image of the positive electrode active material to the total mass of K element in the obtained cross-sectional image of the positive electrode active material was defined as the ratio of the mass of K element in the surface region of the positive electrode active material to the total mass of K element in the positive electrode active material.

[0109] In some embodiments, the volume-distributed particle size Dv50 of the positive electrode active material is 3-15 μm, and selectively 4-9 μm. When the volume-distributed particle size Dv50 of the positive electrode active material is within the above range, it can have a relatively high gram capacity and a relatively high compaction density, and furthermore, it can have good ion transport capacity and rate performance.

[0110] The volume distribution particle size Dv50 of the positive electrode active material has a known meaning in this art, representing the particle size corresponding to the point when the cumulative volume distribution percentage of the material reaches 50%, and can be measured using instruments and methods known in this art. For example, it can be easily measured using a laser particle size analyzer, referring to GB / T 19077-2016. The test instrument may be a Mastersizer 2000E laser particle size analyzer from Malvern, UK.

[0111] In some embodiments, the form of the positive electrode active material may include one or more of spherical single crystals, sheet-like single crystals, and spherical polycrystalline materials.

[0112] The term "single crystal" further includes pseudo-single crystals, which refer to particles formed by the aggregation of several or more than ten crystal grains.

[0113] The term "spherical" further includes subspherical, which refers to a shape that is basically spherical or has a length-to-shortness ratio close to 1. For example, the length-to-shortness ratio is 1.3 or less, and selectively 1.2 or less.

[0114] The morphology of the positive electrode active material can be tested using a scanning electron microscope, for example, by referring to JY / T010-1996. The test equipment may be a Sigma300 scanning electron microscope from ZEISS GmbH, Germany.

[0115] In some embodiments, the positive electrode active material may include one or more of the O3 phase, P2 phase, and P3 phase.

[0116] In some embodiments, the positive electrode active material contains an O3 phase, and in the peak separation pattern of the X-ray diffraction pattern of the positive electrode active material, there are two diffraction peaks within the range of 2θ from 16.0° to 16.7°, with the diffraction peak located between 2θ from 16.0° to 16.3° being designated as the first peak, and the diffraction peak located between 2θ from 16.3° to 16.7° being designated as the second peak, and the ratio of the peak intensity of the first peak to the peak intensity of the second peak is 0.1:1 or less, and selectively 0.076:1 or less.

[0117] The X-ray diffraction pattern of the positive electrode active material is obtained by testing with an X-ray diffractometer. The test can be performed under the following conditions: CuK α The radiation source is a beam with a radiation wavelength λ = 1.5406 Å, the scanning angle range of 2θ is 10°-70°, and the scanning speed is 4° / min. The test equipment may be a Bruker D8A_A25 X-ray powder diffractometer from Bruker AxS GmbH, Germany.

[0118] The peak separation pattern of the X-ray diffraction pattern of the positive electrode active material was obtained by refining the X-ray diffraction pattern of the positive electrode active material using the Rietveld whole-spectrum fitting refinement method with Topas software. The range where 2θ is 16.0° to 16.7° corresponds to the diffraction peak appearance position corresponding to the (003) crystal plane of the positive electrode active material.

[0119] The first peak's 2θ is located between 16.0° and 16.3°, indicating the O3 phase of lattice strain.

[0120] The second peak's 2θ is located between 16.3° and 16.7°, indicating the main O3 phase.

[0121] The ratio of the peak intensity of the first peak to the peak intensity of the second peak represents the ratio of the O3 phase content of the lattice strain to the bulk O3 phase content.

[0122] The ratio of the peak intensity of the first peak to the peak intensity of the second peak is the ratio of the integral area of ​​the first peak to the integral area of ​​the second peak.

[0123] In the peak separation pattern of the X-ray diffraction pattern of the positive electrode active material according to the embodiment of this application, the ratio of the peak intensity of the first peak to the peak intensity of the second peak being 0.1:1 or less indicates that the main body structure of the O3 phase of the positive electrode active material according to the embodiment of this application is well maintained, and the positive electrode active material contains only a small amount of lattice-strained O3 phase.

[0124] In some embodiments, the positive electrode active material comprises an O3 phase, and the X-ray diffraction pattern of the positive electrode active material includes diffraction peaks of the (104) crystal plane where 2θ is between 41.5° and 42.5° and diffraction peaks of the (015) crystal plane where 2θ is between 44.5° and 45.5°, and the ratio of the peak intensity of the diffraction peak of the (104) crystal plane to the peak intensity of the diffraction peak of the (015) crystal plane is greater than 10:1.

[0125] The ratio of the peak intensity of the diffraction peak of the (104) crystal plane to the peak intensity of the diffraction peak of the (015) crystal plane is the ratio of the integral area of ​​the diffraction peak of the (104) crystal plane to the integral area of ​​the diffraction peak of the (015) crystal plane.

[0126] In the X-ray diffraction pattern of the positive electrode active material according to the embodiment of this application, the ratio of the peak intensity of the diffraction peak of the (104) crystal plane to the peak intensity of the diffraction peak of the (015) crystal plane is greater than 10:1, which indicates that the layered structure of the positive electrode active material according to the embodiment of this application is relatively stable, crystal plane slippage is less likely to occur, and aggregation of transition metal elements is less likely to occur.

[0127] In some embodiments, the interlayer spacing d of the (003) crystal plane of the positive electrode active material is 003 The Å value is 16-16.3 Å. At this value, the positive electrode active material can have good rate performance and relatively high stability.

[0128] The interlayer spacing d of the (003) crystal plane of the positive electrode active material. 003 This is a known meaning in this field, and the X-ray diffraction pattern is measured using an X-ray diffractometer in accordance with JIS K0131-1996 General Rules for X-ray Diffraction Analysis, and the interlayer spacing d of the (003) crystal plane is measured. 003 It can be obtained. The test can be conducted under the following conditions: CuK α The radiation source is a beam with a radiation wavelength λ = 1.5406 Å, the scanning angle range of 2θ is 10°-70°, and the scanning speed is 4° / min. The test equipment may be a Bruker D8A_A25 X-ray powder diffractometer from Bruker AxS GmbH, Germany.

[0129] In some embodiments, the content of free alkaline substances on the surface of the positive electrode active material may be 0.2-20 wt%, and selectively 0.2-15 wt%, 0.2-10 wt%, 0.2-5 wt%, 0.2-2.5 wt%, 0.2-2 wt%, 0.5-1.5 wt%, and 0.5-1.4 wt%. Because the content of free alkaline substances on the surface of the positive electrode active material is relatively low, the positive electrode active material can be given relatively high interfacial stability, which is advantageous in improving the cycle performance and / or rate performance of the battery, and further advantageous in improving the processing performance of the positive electrode slurry and the battery.

[0130] The free alkaline substances on the surface of the positive electrode active material mainly consist of NaOH and Na2CO3, and the amount of free alkaline substances can be detected by chemical titration or potentiometric titration. The amount of free alkaline substances on the surface differs depending on the type of positive electrode active material.

[0131] In some embodiments, the pH of the positive electrode active material may be 11.5–13.5, and selectively 11.8–12.6. The relatively low pH of the positive electrode active material allows for relatively high interfacial stability, which is advantageous for improving the battery's cycle performance and / or rate performance, and further advantageous for improving the processing performance of the positive electrode slurry and the battery.

[0132] The pH of the positive electrode active material is a known value in the art and can be measured using instruments and methods known in the art. For example, it may be tested by referring to GB / T 9724-2007. In some embodiments, the test can be performed according to the following steps: A solution of the positive electrode active material sample and deionized water is prepared at 25°C in a mass ratio of 1:9, sealed and placed in a magnetic stirrer and stirred for 30 minutes, then allowed to stand for 90 minutes and filtered, and the pH of the filtrate is tested with a pH meter (e.g., pHS-3C), which is the pH of the positive electrode active material.

[0133] [Manufacturing method] Embodiments of the present application further provide a method for manufacturing a positive electrode active material, the method comprising the steps of providing an initial positive electrode active material containing a sodium-containing layered transition metal oxide, and performing a washing treatment on the initial positive electrode active material using an alkaline washing solution, wherein the alkaline washing solution contains K + including the step of, and after the washing is completed, drying to obtain the positive electrode active material.

[0134] The positive electrode active material contains a layered transition metal oxide represented by formula (I),

Chemical formula

[0135] The manufacturing method according to the embodiments of the present application uses an alkaline washing solution containing K + to wash the sodium-containing layered transition metal oxide. During the washing process, free alkaline substances (such as NaOH, Na2CO3, etc.) on the material surface are washed away, so the content of free alkaline substances on the surface of the obtained positive electrode active material is relatively low and the pH is also relatively low. During the washing process, the high concentration of K + in the alkaline washing solution causes ion exchange between Na + and K + / Na + in the material, thereby doping K + into the material. At the same time, the washing solution exhibits alkalinity and contains a large amount of OH - thereby causing Na + / H+ It is also possible to suppress the exchange.

[0136] During the later stages of charging, after a large amount of sodium is removed from the positive electrode active material, the stability of the crystal structure deteriorates, making it prone to irreversible transformation from a layered structure to a rock salt phase structure. + After introducing it into the positive electrode active material, K + This can act as a support, stabilizing the crystal structure of the positive electrode active material, improving interfacial stability, and further improving the stability of the crystal structure, thereby reducing the probability of crystal structure collapse or irreversible transformation occurring after a large amount of sodium is removed from the positive electrode active material in the later stages of charging.

[0137] The relatively large ionic radius of K+ (approximately 0.138 nm) allows it to occupy some of the Na+ positions on the surface of the positive electrode active material, thereby increasing the interlayer spacing of the positive electrode active material and giving the positive electrode active material good rate performance.

[0138] The K element content in the positive electrode active material exhibits a characteristic of gradually decreasing from the particle surface to the interior of the particle. This effectively reduces stress during the battery cycle process, thereby decreasing the occurrence of microcracks and allowing batteries using this positive electrode active material to have a long cycle life.

[0139] Therefore, the positive electrode active material obtained by the manufacturing method of the embodiment of this application has a relatively low pH, a relatively low content of surface-free alkaline substances, and further contains K element, which has the characteristic of gradually decreasing in content from the particle surface to the interior of the particle. This not only stabilizes the crystal structure of the positive electrode active material but also gives the positive electrode active material good cycle performance and rate performance.

[0140] Sodium-containing layered transition metal oxides are extremely sensitive to moisture, and during the washing process with water or acidic solutions, Na + / H +Sodium desorption is likely to occur due to exchange and moisture entering the material's crystal structure. Furthermore, after a large amount of sodium ions are desorbed, crystal plane slip occurs in sodium-containing layered transition metal oxides, causing a relatively large change in the material's X-ray diffraction pattern. Taking O3-phase layered transition metal oxides as an example, after washing the material with water or an acid solution, the diffraction peak of the (003) crystal plane in the X-ray diffraction pattern tends to shift to a lower angle, and at the same time, the diffraction peak of the (015) crystal plane is strengthened, while the diffraction peak of the (104) crystal plane is weakened.

[0141] The positive electrode active material obtained using the manufacturing method according to the embodiments of this application shows almost no change in its crystal structure compared to the initial positive electrode active material before washing, and the intensity and position of each characteristic peak in the material's X-ray diffraction pattern also show almost no change. Taking an O3-phase layered transition metal oxide as an example, the positive electrode active material obtained using the manufacturing method according to the embodiment of this application has a ratio of the peak intensity of the diffraction peak of the (104) crystal plane to the peak intensity of the diffraction peak of the (015) crystal plane greater than 10:1, and in the peak separation pattern of the X-ray diffraction pattern of the positive electrode active material, there are two diffraction peaks in the range of 2θ from 16.0° to 16.7°, with the diffraction peak located between 2θ from 16.0° to 16.3° being designated as the first peak, and the diffraction peak located between 2θ from 16.3° to 16.7° being designated as the second peak, and the ratio of the peak intensity of the first peak to the peak intensity of the second peak being 0.1:1 or less, and at the same time, the amount of shift of the diffraction peak of the (003) crystal plane to a lower angle compared to the X-ray diffraction pattern of the material before cleaning being 0.2° or less.

[0142] In some embodiments, the initial positive electrode active material refers to the positive electrode active material to be cleaned. The initial positive electrode active material comprises a sodium-containing layered transition metal oxide, which may be a material known in the art, and the embodiments of this application are not limited thereto. The initial positive electrode active material can be manufactured using methods known in the art, for example, by solid-phase sintering, or it may be commercially available. In some embodiments, the initial positive electrode active material is Na x1 M a A b Bc O m Q n It may include x1 > 0.5, and the other parameters are defined as above and will not be explained further here.

[0143] In some embodiments, the manufacturing method further includes the step of performing a sintering treatment on the initial positive electrode active material after cleaning, thereby obtaining the positive electrode active material.

[0144] Washing does not sufficiently stabilize the surface properties of the material. Sintering can stabilize the surface of the material, restoring the surface that has become unstable due to washing, thereby repairing surface defects and reducing voids. Sintering also further stabilizes the surface layer K + Na + By stably positioning the support structure, it can better perform its function and improve rate performance, and it can also reduce the probability of crystal structure collapse or irreversible transformation occurring after a large amount of sodium is removed from the positive electrode active material in the later stages of charging.

[0145] During the washing process, K + This is due to ion exchange, which removes the Na from the shallow surface layer. + It occupies a large number of positions, but some K + K remains on the material surface, and through sintering, K remains further on the material surface. + Further diffusion into the particle interior allows the K element content to exhibit a more pronounced gradual decrease characteristic from the particle surface to the interior. Compared to a positive electrode active material uniformly doped with the K element, a positive electrode active material exhibiting a gradual decrease characteristic of the K element can effectively relieve stress during the battery cycle process, thereby reducing the occurrence of microcracks and improving the cycle performance of both the positive electrode active material and the battery.

[0146] In some embodiments, the sintering temperature may be 200°C-700°C, selectively 300°C-600°C, and even more selectively 450°C-550°C.

[0147] In some embodiments, the sintering time may be 20 hours or less, selectively 10 hours or less, and even more selectively 3-8 hours or 3-5 hours.

[0148] In some embodiments, the sintering atmosphere may be an oxygen-containing atmosphere. Sintering in an oxygen-containing atmosphere can stabilize the surface structure of the material, allowing surface sodium that has become unstable due to cleaning to re-react with oxygen and stabilize, thereby repairing surface defects and reducing voids, which is advantageous in improving the cycle performance and / or rate performance of the battery.

[0149] In some embodiments, the volume fraction of oxygen gas in the sintering atmosphere may be 15%-40% or 17%-30%.

[0150] In some embodiments, the sintering atmosphere may contain one or more inert gases, such as nitrogen gas, helium gas, and argon gas.

[0151] In some embodiments, the sintering atmosphere may be an air atmosphere. This can reduce production costs.

[0152] In some embodiments, the initial cathode active material may be in the form of one or more of spherical single crystals, sheet-like single crystals, or spherical polycrystalline materials.

[0153] K + It can be diffused to an appropriate depth by ion exchange and sintering treatment. In the case of spherical single crystals or polycrystalline crystals, its Na + Since the moving channel may be along each direction, K + / Na + Ion exchange and K + Diffusion can also occur along all directions, K + Doping is also formed along each direction. In the case of a sheet-like single crystal, the plane with a relatively large surface area is the ab plane, and the direction perpendicular to this plane is the c axis direction, Na +Since movement generally occurs along the ab plane, K + Doping is generally performed along a direction perpendicular to the c-axis.

[0154] In some embodiments, in the step of cleaning the initial positive electrode active material using an alkaline cleaning solution, the cleaning temperature may be 35°C or lower, and selectively 20°C-30°C. When the cleaning temperature is within the above range, Na + / H + This can further reduce the exchange rate and decrease intercalation sodium elution.

[0155] In some embodiments, in the step of cleaning the initial positive electrode active material using an alkaline cleaning solution, the cleaning time may be 60 min or less, selectively 20 min or less, and more selectively 5-20 min. When the cleaning time is within the above range, Na + / H + This can further reduce exchange and decrease intercalation sodium elution.

[0156] In some embodiments, in the step of cleaning the initial positive electrode active material using an alkaline cleaning solution, the pH of the alkaline cleaning solution may be 11 or higher, selectively 12 or higher, and more selectively 12.5-14, 13-14. When the pH of the alkaline cleaning solution is within the above range, Na + / H + This can further reduce exchange and decrease intercalation sodium elution.

[0157] In some embodiments, the solute in the alkaline cleaning solution may include a soluble potassium salt, and may include, but is not limited to, one or more of potassium hydroxide, potassium carbonate, and potassium bicarbonate.

[0158] In some embodiments, the solvent in the alkaline cleaning solution may include one or more of water, alcohol-based solvents, and ester-based solvents, and selectively includes water.

[0159] In some embodiments, the solvent in the alkaline cleaning solution may consist only of water, for example, deionized water.

[0160] In some embodiments, the alkaline cleaning solution is Na + It may further contain the following. For example, the solute in the alkaline cleaning solution may further contain a soluble sodium salt, which may include, but is not limited to, one or more of sodium hydroxide, sodium carbonate, and sodium bicarbonate.

[0161] When cleaning with an alkaline cleaning solution, some of the sodium is washed away, which can cause defects and voids on the material surface. + By including Na + It can replenish and improve capacity, and also, during the sintering process, it can remove Na remaining on the material surface. + It can further react with oxygen, playing a role in repairing surface defects and reducing vacancies.

[0162] Alkaline cleaning solution contains Na + By including Na + / H + This further reduces exchange, decreases interlayer sodium elution, and allows the positive electrode active material to better retain its original layered structure.

[0163] In some examples, Na + and K + The molar ratio may be 1:(0.1-1), selectively 1:(0.2-5), and even more selectively 1:(0.2-2).

[0164] By adjusting one or more parameters such as sintering temperature, sintering time, alkaline cleaning solution concentration, cleaning temperature, and cleaning time within the above range, the content of element K can be gradually reduced from the surface of the positive electrode active material particles towards the interior of the particles, and the uniform distribution characteristics of element K in the positive electrode active material can be avoided. Furthermore, by adjusting the distribution region of element K, the mass of element K in the surface region of the positive electrode active material may be set to 50% to 95% of the total mass of element K in the positive electrode active material, and selectively to 70% to 95%, 75% to 95%, 80% to 95%, 83% to 95%, 70% to 92%, 75% to 92%, 80% to 92%, 83% to 92%, 70% to 90%, 75% to 90%, 80% to 90%, and 83% to 90%.

[0165] In some embodiments, 0.001≦y<0.5, and selectively, 0.001≦y≦0.4, 0.001≦y≦0.3, 0.001≦y≦0.2, 0.001≦y≦0.1, 0.001≦y≦0.05, 0.005≦y≦0.05, 0.008≦y≦0.05, and 0.012≦y≦0.05. When the K element content in the positive electrode active material is within the above range, the surface structure of the positive electrode active material can be better stabilized, reducing the probability of crystal structure collapse or irreversible transformation occurring after a large amount of sodium desorption of the positive electrode active material in the later stages of charging, and at the same time, the positive electrode active material can be given a relatively high gram capacity and good cycle performance and rate performance. If the K element content is too high, the K element does not provide capacity, thus reducing the gram capacity of the positive electrode active material, and too much K + Na + After occupying the position, further Na + This hinders the movement of the battery and affects its cycle performance and rate performance.

[0166] In some embodiments, a method for producing a positive electrode active material comprises the steps of providing an initial positive electrode active material containing a sodium-containing layered transition metal oxide, and performing a cleaning treatment on the initial positive electrode active material using an alkaline cleaning solution, wherein the alkaline cleaning solution is K +including and having a pH of the alkaline cleaning solution of 12 or more, selectively 13 - 14, and performing a sintering process on the initial cathode active material after the cleaning to obtain a cathode active material after completion.

[0167] Thereby, Na + / H + exchange can be further reduced, interlayer sodium elution can be decreased, and the structure of the cathode active material can be stabilized.

[0168] In some embodiments, the method for manufacturing a cathode active material includes providing an initial cathode active material containing a sodium-containing layered transition metal oxide, and performing a cleaning process on the initial cathode active material using an alkaline cleaning solution. Here, the alkaline cleaning solution contains K + and Na + and the molar ratio of Na + to K + may be 1:(0.1 - 1), selectively 1:(0.2 - 2), the pH of the alkaline cleaning solution is 12 or more, selectively 13 - 14, the cleaning temperature is 35°C or less, selectively 20°C - 30°C, the cleaning time is 60 min or less, selectively 5 - 20 min, and performing a sintering process on the initial cathode active material after the cleaning to obtain a cathode active material after completion. Here, the sintering temperature is 300°C - 600°C, selectively 450°C - 550°C, the sintering time is 10 h or less, selectively 3 h - 8 h, and the sintering atmosphere is an oxygen-containing atmosphere. Selectively, the volume fraction of oxygen gas is 15% - 40%.

[0169] Thereby, the structure of the cathode active material can be further stabilized, the original layered structure of the cathode active material can be better retained, the capacity of the cathode active material can be further improved, and the cycle performance and rate performance of the cathode active material can be improved.

[0170] Unless otherwise specified, each raw material used in the above manufacturing method can be obtained by purchasing commercially available products.

[0171] Positive electrode plate Embodiments of the present application further provide a positive electrode plate.

[0172] The positive electrode plate includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, and the positive electrode film layer includes the positive electrode active material as described above in the present application or the positive electrode active material manufactured by the manufacturing method as described above in the present application.

[0173] In some embodiments, the content of the positive electrode active material in the positive electrode film layer is 50 wt% to 99 wt%, optionally 85 wt% to 99 wt%, based on the total weight of the positive electrode film layer.

[0174] The positive electrode current collector has two opposing surfaces in its thickness direction, and the positive electrode film layer is disposed on either one or both of the two opposing surfaces of the positive electrode current collector.

[0175] The positive electrode film layer may further include other positive electrode active materials known in the art, for example, one or more of fluorides, sulfides, phosphates, pyrophosphates, metal organic frameworks / metal hexacyanides, and organic compounds, but are not limited thereto. These other positive electrode active materials may be used alone or in combination of two or more. As an example, other positive electrode active materials are NaCoO2, Na 2 / 3 [Cu 1 / 3 Mn 2 / 3 O2, Na 2 / 3 [Fe 1 / 3 Mn 2 / 3 O2, Na 2 / 3 [Li 1 / 3 Ni 2 / 3 O2, Na[Ni 0.5 Co 0.5 O2, Na 7 / 9 [Cu 2 / 9 Fe 1 / 9 Mn 2 / 3 O2, Na 2 / 3 [Li 1 / 3 Mn 1 / 2 Ti 1 / 6 O2, Na[Ni 0.5 Fe 0.5 O2, Na[Co 0.5Fe 0.5 ]O2, Na[Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 ]O2,Na[Cu 1 / 9 Ni 2 / 9 Fe 1 / 3 Mn 1 / 3 It may contain one or more of the O2 components.

[0176] In some embodiments, the positive electrode film layer further selectively comprises a positive electrode conductive agent. This application does not particularly limit the type of positive electrode conductive agent, and for example, the positive electrode conductive agent may include one or more of the following: superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0177] In some embodiments, the positive electrode film layer further selectively includes a positive electrode adhesive. This application is not particularly limited to the type of positive electrode adhesive, and as an example, the positive electrode adhesive may include one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene ternary copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene ternary copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorine-containing acrylate resin, styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic acid resin (e.g., polyacrylate PAA, polymethacrylate PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0178] In some embodiments, the positive electrode current collector may be a metal foil sheet or a composite current collector. Aluminum foil can be used as an example of a metal foil sheet. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. For example, the metal material may include one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. For example, the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0179] The positive electrode film layer is generally obtained by coating a positive electrode slurry onto a positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is generally formed by dispersing a positive electrode active material, a selective conductive agent, a selective adhesive, and any other components in a solvent and stirring them uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP).

[0180] [Negative electrode plate] The battery cell includes a negative electrode plate. The structure and composition of the negative electrode plate may be selected according to the type of battery cell, and the embodiments of this application are not limited thereto.

[0181] In some embodiments, the negative electrode plate may include a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector and containing a negative electrode active material. For example, the negative electrode current collector has two opposing surfaces in its thickness direction, and the negative electrode film layer is provided on one or both of the two opposing surfaces of the negative electrode current collector.

[0182] The negative electrode active material may be a material known in this field, for example, the negative electrode active material may include, but is not limited to, one or more of soft carbon, hard carbon, and mesocarbon microbeads.

[0183] In some embodiments, the negative electrode film layer further selectively comprises a negative electrode conductive agent. This application does not particularly limit the type of negative electrode conductive agent, and for example, the negative electrode conductive agent may include one or more of the following: superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0184] In some embodiments, the negative electrode film layer further selectively includes a negative electrode adhesive. This application is not particularly limited to the type of negative electrode adhesive, and as an example, the negative electrode adhesive may include one or more of the following: styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic acid resin (e.g., polyacrylate PAA, polymethacrylate PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0185] In some embodiments, the negative electrode film layer may further selectively include other additives. For example, the other additives may include thickeners such as sodium carboxymethylcellulose (CMC), PTC thermistor materials, etc.

[0186] The negative electrode film layer is generally obtained by coating a negative electrode slurry onto a negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry is generally formed by dispersing a negative electrode active material, a selective conductive agent, a selective adhesive, and other selective auxiliary agents in a solvent and stirring them uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0187] The negative electrode plate does not exclude any additional functional layers other than the negative electrode film layer. For example, in some embodiments, the negative electrode plate may further include a conductive undercoating (e.g., composed of a conductive agent and an adhesive) sandwiched between the negative electrode current collector and the negative electrode film layer and installed on the surface of the negative electrode current collector, and in some embodiments, the negative electrode plate may further include a protective layer covering the surface of the negative electrode film layer.

[0188] In some embodiments, the negative electrode plate may include a negative electrode current collector and a metal layer placed on at least one surface of the negative electrode current collector, wherein the metal material in the metal layer may include one or more of pure sodium and sodium alloys.

[0189] Sodium alloys may be alloys formed from metallic sodium with other metallic or nonmetallic elements. For example, the other metallic elements in a sodium alloy may include one or more of tin, zinc, aluminum, magnesium, silver, gold, gallium, indium, and platinum, and the nonmetallic elements in a sodium alloy may include one or more of boron, carbon, and silicon.

[0190] In some embodiments, the negative electrode plate may be made of a sodium sheet (foil) or a sodium alloy sheet (foil).

[0191] In some embodiments, the negative electrode plate may include a negative electrode current collector, which is then assembled to form a sodium metal battery cell without a negative electrode.

[0192] In some embodiments, the negative electrode current collector may include a metal foil sheet, a three-dimensional porous current collector, or a composite current collector. Examples of metal foil sheets may include copper foil, copper alloy foil, nickel foil, nickel alloy foil, aluminum foil, and aluminum alloy foil. Examples of three-dimensional porous current collectors may include copper mesh, nickel mesh, foamed copper, foamed nickel, and foamed aluminum. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. For example, the metal material may include one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, aluminum, aluminum alloys, silver, and silver alloys. For example, the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0193] [Electrolyte] A battery cell includes an electrolyte. This application does not specifically limit the type of electrolyte, which can be selected according to the needs. For example, the electrolyte may include one or more selected from solid electrolytes and liquid electrolytes (i.e., electrolyte solutions).

[0194] In some embodiments, the electrolyte is an electrolyte solution, which comprises an electrolyte salt and a solvent.

[0195] The type of electrolyte salt is not specifically limited and can be selected according to actual needs. In some embodiments, the electrolyte salt may include one or more of NaPF6, NaClO4, NaBCl4, NaSO3CF3, and Na(CH3)C6H4SO3.

[0196] The type of solvent is not specifically limited and can be selected according to actual needs. In some examples, the solvent may include one or more of ester solvents, sulfone solvents, and ether solvents. For example, the solvent may include, but is not limited to, one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS), and diethyl sulfone (ESE).

[0197] In some embodiments, the electrolyte further selectively includes additives. For example, the additives may include negative electrode film forming additives, positive electrode film forming additives, and further additives that can improve some of the battery's performance characteristics, such as additives that improve the battery's overcharge performance, additives that improve the battery's high-temperature performance, and additives that improve the battery's low-temperature output performance.

[0198] [Separator] Battery cells that use electrolytes, and some battery cells that use solid electrolytes, also include a separator. The separator is placed between the positive and negative electrodes and primarily serves to prevent internal short circuits.

[0199] This application does not particularly limit the type of separator, and any known porous structure separator having good chemical and mechanical stability may be selected.

[0200] In some embodiments, the separator material may include one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film. When the separator is a multilayer composite film, the materials of each layer may be the same or different.

[0201] Methods for manufacturing battery cells are known. In some embodiments, a battery cell can be formed by assembling a positive electrode plate, a separator, a negative electrode plate, and an electrolyte. For example, the positive electrode plate, separator, and negative electrode plate can be formed into an electrode assembly through a winding process and / or a lamination process, the electrode assembly is placed in an outer casing, dried, and then the electrolyte is injected. A battery cell is then obtained through processes such as packaging, settling, and chemical conversion. Multiple battery cells may further constitute a battery module by series connection, parallel connection, or series-parallel connection. Multiple battery modules may further constitute a battery pack via series connection, parallel connection, or series-parallel connection. In some embodiments, multiple battery cells may directly constitute a battery pack.

[0202] power consumption equipment Embodiments of this application further provide a power consumption device including a battery according to embodiments of this application. The battery can serve as the power source for the power consumption device, or it can serve as the energy storage unit for the power consumption device. The power consumption device may be, but is not limited to, mobile devices (e.g., mobile phones, tablet computers, laptop computers, 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.

[0203] The power consumption device may select a specific type of battery according to its usage needs, for example, a battery cell, a battery module, or a battery pack.

[0204] Figure 6 is a schematic diagram of an example power consumption device. This power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the demand for high power output and high energy density of this power consumption device, a battery pack or battery module may be used.

[0205] Other examples of power-consuming devices include mobile phones, tablet computers, and laptop computers. These power-consuming devices are generally required to be thin, and battery cells may be used as the power source.

[0206] Examples The following examples provide a more detailed description of the contents disclosed in this application, and these examples are for illustrative purposes only, as it will be obvious to those skilled in the art that various modifications and changes can be made within the scope of the contents disclosed in this application. Unless otherwise stated, all parts, percentages and ratios reported in the following examples are based on mass, and all reagents used in the examples can be obtained commercially or synthesized according to conventional methods and can be used directly without further processing, and all instruments used in the examples can be obtained commercially.

[0207] Comparative Example 1 A total of 30 g of samples were weighed, consisting of Na2CO3, Mn2O3, Fe2O3, and NiO, in a molar ratio of Na:Mn:Fe:Ni of 1:0.4:0.3:0.3. The obtained samples were pre-polished in an agate mortar and then placed in a planetary ball mill and ball-milled for 1 hour to obtain a precursor mixture. The obtained precursor mixture was uniformly placed in an open crucible and subsequently heated in a muffle furnace from 25°C to 950°C at a heating rate of 5°C / min, and then maintained at 950°C for 15 hours. The atmosphere used was dehumidified, carbon dioxide-free air. After completion, it was allowed to cool naturally, and the unmodified NaNi was obtained. 0.3 Fe 0.3 Mn 0.4 O2 layered transition metal oxide was obtained.

[0208] Comparative Example 2 A total of 30g of Na2CO3, Mn2O3, Fe2O3, and NiO in a molar ratio of Na:Mn:Fe:Ni of 1:0.4:0.3:0.3 is weighed, then KNO3 (calculated assuming a mass of 0.44 wt% of element K) is added, the resulting sample is pre-polished in an agate mortar and then placed in a planetary ball mill and ball-milled for 1 hour to obtain a precursor mixture, the resulting precursor mixture is uniformly placed in an open crucible, and then heated in a muffle furnace from 25°C to 950°C at a heating rate of 5°C / min, and maintained at 950°C for 15 hours. The atmosphere used is dehumidified, carbon dioxide-free air, and after completion, it is allowed to cool naturally. +uniformly doped NaNi 0.3 Fe 0.3 Mn 0.4 O2 layered transition metal oxide was obtained.

[0209] Comparative Example 3 10 g of layered transition metal oxide was added to 10 ml of deionized water and stirred with a magnetic stirrer at 400 rpm at 25°C for 5 min, then filtered by suction. The solid obtained by suction filtration was placed in a vacuum oven and dried at 120°C for 12 hours. The dried powder material was placed in a muffle furnace and heated to 500°C at a heating rate of 5°C / min, and then maintained at a constant temperature for 5 hours. The atmosphere used was air. After completion, it was allowed to cool naturally to obtain the cathode active material.

[0210] Comparative Example 4 NaOH was prepared in an alkaline washing solution with a concentration of 1 mol / L, and the solvent was deionized water. Unmodified NaNi prepared in Comparative Example 1 was also prepared in a solid-liquid ratio of 1:1. 0.3 Fe 0.3 Mn 0.4 10 g of O2 layered transition metal oxide and 10 ml of alkaline cleaning solution were taken. 10 g of layered transition metal oxide was added to 10 ml of alkaline cleaning solution, and the mixture was stirred with a magnetic stirrer at 400 rpm at 25°C for 5 minutes, followed by suction filtration. The solid obtained by suction filtration was placed in a vacuum oven and dried at 120°C for 12 hours. The dried powder material was placed in a muffle furnace and heated to 500°C at a heating rate of 5°C / min, and then maintained at a constant temperature for 5 hours. The atmosphere used was air. After completion, it was allowed to cool naturally to obtain the positive electrode active material.

[0211] Example 1 (1) NaOH, KOH + / K + An alkaline washing solution with a total concentration of 1 mol / L was prepared with a molar ratio of 1:0.5, and the solvent was deionized water.

[0212] (2) Unmodified NaNi produced in Comparative Example 1 with a solid-liquid ratio of 1:1 0.3 Fe 0.3 Mn 0.4Take 10 g of O2 layered transition metal oxide and 10 ml of alkaline cleaning solution. Add 10 g of the layered transition metal oxide to 10 ml of the alkaline cleaning solution, stir with a magnetic stirrer at 25 °C and 400 rpm for 5 min, and then perform suction filtration.

[0213] (3) The solid obtained by suction filtration was placed in a vacuum oven and dried at 120 °C for 12 h.

[0214] (4) The powdered material obtained by drying was placed in a muffler furnace, heated to 500 °C at a heating rate of 5 °C / min, and held at a constant temperature for 5 h. The atmosphere used was air.

[0215] (5) After completion, allow to cool naturally, and a positive electrode active material with K + doping on the surface was obtained.

[0216] Example 2 Weighed a total of 30 g of samples of Na2CO3, Mn2O3, Fe2O3, and NiO so that the molar ratio of Na:Mn:Fe:Ni was 1:0.4:0.3:0.3. The obtained samples were pre-ground in an agate mortar and then put into a planetary ball mill for ball milling for 1 h to obtain a precursor mixture. The obtained precursor mixture was uniformly placed in an open crucible, and then heated from 25 °C to 900 °C at a heating rate of 5 °C / min in a muffler furnace, and held at a constant temperature of 900 °C for 15 h. The atmosphere used was dehumidified and carbon dioxide-removed air. After completion, allow to cool naturally, and unmodified NaNi 0.3 Fe 0.3 Mn 0.4 O2 layered transition metal oxide was obtained.

[0217] Next, according to the same process as in Example 1, unmodified NaNi 0.3 Fe 0.3 Mn 0.4 O2 layered transition metal oxide was washed, and after completion, a positive electrode active material with K + doping on the surface was obtained.

[0218] Example 3 A total of 30 g of samples were weighed, consisting of Na2CO3, Mn2O3, Fe2O3, and NiO, in a molar ratio of Na:Mn:Fe:Ni of 1:0.4:0.3:0.3. The obtained samples were pre-polished in an agate mortar and then placed in a planetary ball mill and ball-milled for 1 hour to obtain a precursor mixture. The obtained precursor mixture was uniformly placed in an open crucible and subsequently heated in a muffle furnace from 25°C to 970°C at a heating rate of 5°C / min, and then maintained at 970°C for 20 hours. The atmosphere used was dehumidified, carbon dioxide-free air. After completion, it was allowed to cool naturally, and the unmodified NaNi was obtained. 0.3 Fe 0.3 Mn 0.4 O2 layered transition metal oxide was obtained.

[0219] Next, following the same process as in Example 1, the unmodified NaNi 0.3 Fe 0.3 Mn 0.4 O2 layered transition metal oxide is washed, and after completion, K is placed on the surface. + A doped positive electrode active material was obtained.

[0220] Example 4 Na2CO3 and spherical precursor Ni 0.3 Fe 0.3 Mn 0.4 A total of 30 g of sample was weighed with (OH)2 in a molar ratio of 0.5:1. The obtained sample was mixed in a high-speed mixer for 1 hour to obtain a precursor mixture. The obtained precursor mixture was uniformly placed in an open crucible and then heated in a muffle furnace from 25°C to 900°C at a heating rate of 5°C / min, and maintained at 900°C for 15 hours. The atmosphere used was dehumidified, carbon dioxide-free air. After completion, it was allowed to cool naturally, and the unmodified NaNi was obtained. 0.3 Fe 0.3 Mn 0.4 O2 layered transition metal oxide was obtained.

[0221] Next, following the same process as in Example 1, the unmodified NaNi 0.3 Fe 0.3 Mn 0.4 O2 layered transition metal oxide is washed, and after completion, K is placed on the surface. + A doped positive electrode active material was obtained.

[0222] Example 5 The manufacturing process for the positive electrode active material is the same as in Example 1, except that the alkaline cleaning solution in step (1) is a 1 mol / L KOH solution.

[0223] Examples 6-9 In step (1), Na in the alkaline cleaning solution + / K + Aside from the difference in molar ratio, the manufacturing process for the positive electrode active material is the same as in Example 1. The specific parameters are shown in Table 1.

[0224] Examples 10-12 The manufacturing process for the positive electrode active material is the same as in Example 1, except that the concentration and pH of the alkaline cleaning solution differ in step (2). The specific parameters are shown in Table 1.

[0225] Examples 13-14 The manufacturing process for the positive electrode active material is the same as in Example 1, except that the washing temperature is different in step (2). The specific parameters are as shown in Table 1.

[0226] Examples 15-17 The manufacturing process for the positive electrode active material is the same as in Example 1, except for the difference in the washing time in step (2). The specific parameters are as shown in Table 1.

[0227] Examples 18-21 The manufacturing process for the positive electrode active material is the same as in Example 1, except that the sintering temperature is different in step (2). The specific parameters are as shown in Table 1.

[0228] Examples 22-25 The manufacturing process for the positive electrode active material is the same as in Example 1, except for the sintering time in step (2). The specific parameters are as shown in Table 1.

[0229] Test section (1) Test for the content of free alkaline substances on the surface of the positive electrode active material Weigh 20.000 g of the above-prepared positive electrode active material, add it to 100 ml of deionized water, stir for 30 min, then filter. Transfer 60 ml of the filtrate to a 250 ml Erlenmeyer flask, add 10 drops of indicator (methyl orange and phenolphthalein), and shake evenly. At this time, the solution shows a purple color. Then, titrate with a 0.1103 mol / L hydrochloric acid standard solution to calculate the content of free alkaline substances (NaOH, Na2CO3) in the sample.

[0230] (2) X-ray diffraction analysis test of the positive electrode active material The above-prepared positive electrode active material was analyzed using an X-ray powder diffractometer. The test can be carried out under the following conditions: Using CuKα ray as the radiation source, the radiation wavelength λ = 1.5406 Å, the scanning 2θ angle range is 10° - 70°, and the scanning speed is 4° / min. The test equipment may adopt the Bruker D8A_A25 type X-ray powder diffractometer of Bruker AxS, Germany.

[0231] The peak separation pattern of the X-ray diffraction pattern of the positive electrode active material is obtained by using Topas software and the Rietveld whole spectrum fitting refinement method to refine the X-ray diffraction pattern of the positive electrode active material. The range where 2θ is from 16.0° to 16.7° is the position of the diffraction peak appearance corresponding to the (003) crystal plane of the positive electrode active material.

[0232] The 2θ of the first peak is located between 16.0° and 16.3°, indicating the O3 phase with lattice strain. The 2θ of the second peak is located between 16.3° and 16.7°, indicating the main body O3 phase. The ratio of the peak intensity of the first peak to the peak intensity of the second peak is the ratio of the integrated area of the first peak to the integrated area of the second peak.

[0233] (104) The 2θ of the diffraction peak of the crystal plane is located between 41.5° and 42.5°, and the 2θ of the diffraction peak of the (015) crystal plane is located between 44.5° and 45.5°. The peak intensity I of the diffraction peak of the (104) crystal plane(104) And the peak intensity I of the diffraction peak on the (015) crystal plane (015) Ratio I (104) :I (015) This is the ratio of the integral area of ​​the diffraction peak of the (104) crystal plane to the integral area of ​​the diffraction peak of the (015) crystal plane.

[0234] (3) Test of elemental content of positive electrode active material A cross-sectional image of the positive electrode active material is produced using a cross-sectional polishing machine (for example, the IB-09010 CP type argon ion cross-sectional polishing machine from JEOL Japan). The cross-sectional image passes through the center of the positive electrode active material particle, and the "particle center" refers to the area within a radius of 0.1 μm extending from the geometric center of the particle toward the particle surface.

[0235] Referring to JY / T010-1996, the cross-section of the positive electrode active material was scanned using a scanning electron microscope (e.g., a Sigma 300 scanning electron microscope from ZEISS, Germany), and then detected using inductively coupled plasma emission spectroscopy (ICP) to obtain the elemental composition of the positive electrode active material, and the molar content x of sodium and y of potassium were calculated.

[0236] The ratio of the mass of element K in the surface region of the obtained cross-sectional image of the positive electrode active material (a region extending 0.05 L inward from the edge of the particle in the cross-sectional image, where L is the length of the long axis of the positive electrode active material particle, i.e., the maximum value when the line connecting two points on the particle surface passes through the geometric center of the particle) to the total mass of element K in the obtained cross-sectional image of the positive electrode active material was defined as the ratio of the mass of element K in the surface region of the positive electrode active material to the total mass of element K in the positive electrode active material.

[0237] (4) Initial charge capacity and cycle performance test The manufactured positive electrode active material, conductive agent carbon black Super P, and adhesive polyvinylidene fluoride (PVDF) were polished and uniformly mixed in a weight ratio of 80:15:5. An appropriate amount of solvent N-methylpyrrolidone (NMP) was added and the mixture was uniformly stirred to obtain a positive electrode slurry. The positive electrode slurry was uniformly applied to the aluminum foil of the positive electrode current collector, and then dried, cold pressed, and slit to obtain a positive electrode plate.

[0238] Ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in equal volumes to obtain an organic solvent, and then NaClO4 was dissolved in the above organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0239] The manufactured positive electrode plate, separator (a polypropylene film with a thickness of 12 μm), and sodium metal sheet were cut into wafers of appropriate size and stacked in order, with the separator positioned between the positive electrode plate and the sodium metal sheet to provide isolation. The electrolyte was then impregnated into the separator, and the wafers were compacted to obtain a button-type battery.

[0240] At 25°C, a button-type battery was charged with a constant current at a current density of 10 mA / g up to 4.2V to obtain its initial charge capacity, and then discharged with a constant current at a current density of 10 mA / g up to 1.5V to obtain its initial discharge capacity.

[0241] The initial charge capacity (mAh / g) of the positive electrode active material = initial charge capacity of the button cell battery / mass of the positive electrode active material.

[0242] At 25°C, a button-type battery was charged with a constant current of 100 mA / g to 4.2V, and then discharged with a constant current of 100 mA / g to 1.5V to obtain the discharge capacity of the button-type battery after one cycle. A cycle charge-discharge test was performed on the button-type battery according to the above method, and the discharge capacity after each cycle was recorded. The 200-cycle capacity retention rate of the button-type battery was calculated as: discharge capacity at 200 cycles / discharge capacity at 1 cycle.

[0243] (5) Na +Diffusion coefficient test At 25°C, a button cell battery was charged to 4.2V with a constant current of 0.1C, then discharged to 1.5V with a constant current of 0.1C, then charged to 4.2V with a constant current of 1C, followed by constant voltage charging until the current was 0.05C or less. After standing for 6 hours, electrochemical impedance spectroscopy (EIS) testing was performed using an electrochemical workstation. Next, the impedances in the high-frequency, intermediate-frequency, and low-frequency regions of the electrochemical impedance spectroscopy were fitted using fitting software (e.g., Zview) based on the equivalent circuit curve fitting method. The test frequency may be 100kHz-0.01Hz, the voltage amplitude may be set to 10mV, and a German Zahner electrochemical workstation may be used.

[0244] Electrochemical impedance spectroscopy and equation after fitting Based on JPEG2026513161000008.jpg946, the Warburg coefficient σ (the slope corresponding to the low-frequency region) can be obtained. ct R represents the charge transfer resistance. s This represents ohm resistance.

[0245] Na + Diffusion coefficient JPEG2026513161000009.jpg976. R is the gas constant, 8.314 J / (mol·K), T is 298 K, and A is the area of ​​the electrode plate, in cm². 2 Here, n is the number of electrons transferred during the reaction, F is the Faraday constant, 96500 C / mol is the bulk concentration of sodium ions, and the unit is mol / cm³. 3 Therefore, C = ρ / M, where ρ is the density of the positive electrode film layer, and its unit is g / cm³. 3 Here, M is the molar mass of the positive electrode active material, and its unit is g / mol.

[0246] Na +A higher diffusion coefficient indicates a faster solid-phase diffusion rate of sodium ions in the positive electrode active material, resulting in better rate performance.

[0247] The test results are shown in Table 2.

[0248] Comparative Example 1 is a positive electrode active material that has not undergone any surface modification. As can be seen from the test results in Table 2, it contains a large amount of free alkaline material on its surface, has a relatively low capacity, a relatively slow solid-phase diffusion rate of sodium ions, and relatively poor cycle stability, which affects the energy density, cycle performance, and rate performance of the battery.

[0249] The positive electrode active material produced in Comparative Example 2 was a positive electrode active material uniformly doped with K ions. As can be seen from the test results in Table 2, even after uniform doping with bulk K ions, a relatively large amount of free alkaline material remained on the surface of the positive electrode active material. Furthermore, the capacity of the positive electrode active material was relatively low, the solid-phase diffusion rate of sodium ions was relatively slow, and the cycle stability was relatively poor, which affected the energy density, cycle performance, and rate performance of the battery.

[0250] The positive electrode active material of Comparative Example 3 was obtained by washing the positive electrode active material of Comparative Example 1 with water. As can be seen from the test results in Table 2, the content of free alkaline substances on the surface of the positive electrode active material decreases, but the sodium content of the positive electrode active material itself also decreases significantly (x decreases significantly), and the capacity of the positive electrode active material is relatively low, the solid-phase diffusion rate of sodium ions is relatively slow, and the cycle stability is relatively poor, which affects the energy density, cycle performance and rate performance of the battery.

[0251] As can be seen from the test results of Examples 1-25 and Comparative Examples 1 and 3, K +By cleaning with an alkaline cleaning solution containing and then undergoing a sintering process, a positive electrode active material can be obtained that exhibits the characteristic of a gradual decrease in the content of element K from the particle surface to the interior of the particle. As can be seen from the test results in Table 2, the positive electrode active materials produced in Examples 1-25 have a relatively low content of free alkaline substances, a relatively high capacity, a relatively high sodium ion solid-phase diffusion rate, and relatively high cycle stability, thereby enabling the battery to have a high energy density and good cycle performance and rate performance.

[0252] Figure 7 shows the X-ray diffraction patterns of the positive electrode active materials produced in Example 1, Comparative Example 1, and Comparative Example 3. Figure 8 shows the cycle curves of the button-type batteries produced in Example 1, Comparative Example 1, and Comparative Example 3.

[0253] As can be seen from Figure 7, compared to the positive electrode active material produced in Comparative Example 1, the diffraction peak of the (003) crystal plane of the positive electrode active material obtained using the water washing treatment in Comparative Example 3 is significantly shifted to a lower angle, and the 2θ of the diffraction peak of the (003) crystal plane of the positive electrode active material after water washing is smaller than 16.3°, indicating that the water washing treatment destroys the layered structure of the positive electrode active material. Furthermore, as can be seen from the test results in Table 2, the O3 phase of the positive electrode active material after water washing was almost completely converted into a lattice-strained O3 phase. Example 1 is K + The positive electrode active material produced in Comparative Example 1 was cleaned and sintered using an alkaline cleaning solution containing [the specified ingredient]. The resulting positive electrode active material showed a relatively small shift in the diffraction peak of the (003) crystal plane to a lower angle compared to the positive electrode active material of Comparative Example 1. Furthermore, the 2θ of the diffraction peak of the (003) crystal plane of the cleaned positive electrode active material was greater than 16.3°, indicating that the main structure of the O3 phase of the cleaned positive electrode active material was still well maintained. As can be seen from the test results in Table 2, the positive electrode active material produced in Example 1 contains a small amount of lattice-strained O3 phase.

[0254] As can be seen from Figure 7 and Table 2, compared to the positive electrode active material produced in Comparative Example 1, the diffraction peak of the (015) crystal plane and the diffraction peak of the (104) crystal plane of the positive electrode active material obtained using the water washing treatment in Comparative Example 3 are strengthened and weakened.(104) / I (015) The amount decreased significantly. Example 1 is K + The positive electrode active material produced in Comparative Example 1 was washed and sintered using an alkaline cleaning solution containing [the specified substance]. The resulting positive electrode active material showed almost no change in the intensity and position of each characteristic peak in the X-ray diffraction pattern compared to the positive electrode active material of Comparative Example 1.

[0255] As can be seen from Figure 8, the positive electrode active material produced in Example 1 has relatively high cycle stability and can improve the cycle performance of the battery.

[0256] The positive electrode active material of Comparative Example 4 was obtained by washing the positive electrode active material of Comparative Example 1 with an aqueous NaOH solution. As can be seen from the test results in Table 2, the content of free alkaline substances on the surface of the positive electrode active material decreases, but the stability of the crystal structure of the positive electrode active material is relatively poor, and irreversible conversion from a layered structure to a rock salt phase structure is likely to occur. As a result, the cycle stability of the positive electrode active material during the long-term charge-discharge process of the battery is relatively poor, and at the same time, the solid-phase diffusion rate of sodium ions in the positive electrode active material is relatively slow, further worsening the cycle performance and rate performance of the battery.

[0257] As can be seen from the test results of Examples 1-4, the performance of the positive electrode active materials obtained after processing with the same washing and sintering processes differed slightly depending on the particle morphology and / or particle size of the positive electrode active materials, and all of the obtained positive electrode active materials exhibited good performance.

[0258] As can be seen from the test results of Examples 1 and 5-9, the alkaline cleaning solution contains Na + and K + When these are included simultaneously, the performance of the positive electrode active material and the battery can be further improved.

[0259] As can be seen from the test results of Examples 1 and 10-12, the performance of the positive electrode active material and the battery can be further improved by further adjusting the pH of the alkaline cleaning solution.

[0260] As can be seen from the test results of Examples 1 and 13-25, the performance of the positive electrode active material and the battery can be further improved by further adjusting parameters such as the cleaning temperature, cleaning time, sintering temperature, and sintering time.

[0261] As can be seen from the test results of Examples 1-25, the performance of the positive electrode active material and the battery can be further improved by further adjusting the mass ratio of element K in the surface region of the positive electrode active material.

[0262] It should be noted that this application is not limited to the embodiments described above. The embodiments described above are merely illustrative, and any embodiments that have substantially the same configuration as the technical idea and produce the same effects within the scope of the technical proposal of this application are included within the scope of the technical proposal. Furthermore, other methods that are constructed by adding various modifications to the embodiments that a person skilled in the art could conceive of, and by combining some of the components of the embodiments, are also included within the scope of this application, without departing from the spirit of this application.

[0263] [Table 1] JPEG2026513161000011.jpg245170JPEG2026513161000012.jpg245170

[0264] [Table 2] JPEG2026513161000014.jpg245170JPEG2026513161000015.jpg245170JPEG2026513161000016.jpg245170JPEG2026513161000017.jpg245170 [Explanation of Symbols]

[0265] 1: Battery pack, 2: Upper casing, 3: Lower casing, 4: Battery module, 5: Battery cell, 51: Case, 52: Electrode assembly, 53: Cover plate.

Claims

1. A positive electrode active material comprising a layered transition metal oxide represented by formula (I), 【Chemistry 1】 x > 0.5, 0 < y < 0.5, 0 < a ≤ 1, 0 ≤ b ≤ 1 / 3, 0 ≤ c ≤ 1 / 3, 1.9 ≤ m ≤ 2, 0 ≤ n ≤ 0.1, M includes one or more of Mn, Fe, Co, Ni, Cu, A includes one or more metallic elements from groups IA, IIA, IIIIA, IVA, VA, IIB, IVB, VB, VIB, B includes one or more nonmetallic elements from groups IIIA, IVA, VA, VIA, Q includes one or more nonmetallic elements from groups VA and VIA, The positive electrode active material contains element K, and the amount of element K gradually decreases from the particle surface to the interior of the particle.

2. The positive electrode active material according to claim 1, wherein the region formed by extending from the particle surface of the positive electrode active material to the interior of the particle by a distance of 0.05 L is referred to as the surface region of the positive electrode active material, where L is the length of the long axis of the positive electrode active material particle, and the mass of element K in the surface region of the positive electrode active material is 50% to 95% of the total mass of element K in the positive electrode active material, and selectively 70% to 90%.

3. The positive electrode active material according to claim 1 or 2, wherein the positive electrode active material comprises one or more of the O3 phase, P2 phase, and P3 phase.

4. The positive electrode active material according to any one of claims 1 to 3, wherein the positive electrode active material contains an O3 phase, and in the peak separation pattern of the X-ray diffraction pattern of the positive electrode active material, there are two diffraction peaks in the range of 2θ from 16.0° to 16.7°, the diffraction peak located between 2θ from 16.0° to 16.3° is denoted as the first peak, the diffraction peak located between 2θ from 16.3° to 16.7° is denoted as the second peak, and the ratio of the peak intensity of the first peak to the peak intensity of the second peak is 0.1:1 or less, and selectively 0.076:1 or less.

5. The positive electrode active material according to any one of claims 1 to 4, wherein the positive electrode active material comprises an O3 phase, and the X-ray diffraction pattern of the positive electrode active material includes diffraction peaks of a (104) crystal plane located between 41.5° and 42.5° and diffraction peaks of a (015) crystal plane located between 44.5° and 45.5°, and the ratio of the peak intensity of the diffraction peak of the (104) crystal plane to the peak intensity of the diffraction peak of the (015) crystal plane is greater than 10:

1.

6. A contains one or more elements from Li, Ti, Zr, Sb, Nb, Mg, Ca, Mo, Zn, Cr, W, Bi, Sn, Ge, Al, Ba, Sr, V, and / or B contains one or more elements from Si, P, B, S, and Se, and / or Q contains one or more elements from F, Cl, and N, and / or x ≥ 2 / 3 and / or, 0.012 ≤ y ≤ 0.05, and / or, The positive electrode active material according to any one of claims 1 to 5, wherein 0 ≤ b ≤ 1 / 3, 0 ≤ c ≤ 1 / 3, and 0 < b + c ≤ 1 / 3.

7. The positive electrode active material includes a layered transition metal oxide represented by formula (I-1), 【Chemistry 2】 0 < p < 1, 0 < q < 1, a - p - q ≥ 0, and M contains one or more elements from Co, Ni, and Cu. Selectively, 0 < p ≤ 2 / 3, Selectively, 0 < q ≤ 1 / 3, The positive electrode active material according to claim 6, wherein selectively 0 < a - p - q ≤ 1 / 3.

8. The content of free alkaline substances on the surface of the positive electrode active material is 0.2–20 wt%, selectively 0.5–1.4 wt%, and / or The positive electrode active material according to any one of claims 1 to 7, wherein the pH of the positive electrode active material is 11.5-13.5, and selectively 11.8-12.

6.

9. The form of the positive electrode active material includes one or more of spherical single crystals, sheet-like single crystals, and / or spherical polycrystalline materials. The positive electrode active material according to any one of claims 1 to 8, wherein the volume distribution particle size Dv50 of the positive electrode active material is 3-15 μm, and selectively 4-9 μm.

10. A method for producing a positive electrode active material, The steps include providing an initial cathode active material containing a sodium-containing layered transition metal oxide, A step of cleaning the initial positive electrode active material using an alkaline cleaning solution, wherein the alkaline cleaning solution is K ＋ Steps including, The process includes the step of drying after the cleaning is completed to obtain a positive electrode active material, wherein the positive electrode active material comprises a layered transition metal oxide represented by formula (I), 【Transformation 3】 A method for producing a positive electrode active material, wherein x > 0.5, 0 < y < 0.5, 0 < a ≤ 1, 0 ≤ b ≤ 1 / 3, 0 ≤ c ≤ 1 / 3, 1.9 ≤ m ≤ 2, 0 ≤ n ≤ 0.1, M comprises one or more of Mn, Fe, Co, Ni, and Cu, A comprises one or more metallic elements from groups IA, IIA, IIIIA, IVA, VA, IIB, IVB, VB, and VIB, B comprises one or more nonmetallic elements from groups IIIA, IVA, VA, and VIA, Q comprises one or more nonmetallic elements from groups VA and VIA, the positive electrode active material comprises element K, and the content of element K gradually decreases from the particle surface to the interior of the particle of the positive electrode active material.

11. In the step of cleaning the initial positive electrode active material using an alkaline cleaning solution, The washing temperature is 35°C or lower, selectively 20°C-30°C, and / or The washing time is 60 min or less, selectively 5-20 min, and / or The manufacturing method according to claim 10, wherein the pH of the alkaline cleaning solution is 12 or higher, and selectively between 13 and 14.

12. The solute in the aforementioned alkaline cleaning solution includes one or more of potassium hydroxide, potassium carbonate, and / or potassium bicarbonate. The manufacturing method according to claim 10 or 11, wherein the solvent in the alkaline cleaning solution comprises one or more of water, an alcohol-based solvent, and an ester-based solvent, and selectively comprises water.

13. The aforementioned alkaline cleaning solution contains Na ＋ It further includes, Selectively, Na ＋ and K ＋ The manufacturing method according to any one of claims 10 to 12, wherein the molar ratio of is 1:(0.1-10), and selectively 1:(0.2-2).

14. The manufacturing method further includes the step of performing a sintering treatment on the initial positive electrode active material after cleaning, and obtaining a positive electrode active material after the treatment is completed. Selectively, the sintering temperature is 300°C–600°C, selectively 450°C–550°C, and / or Selectively, the sintering time is 10 hours or less, selectively 3 hours to 8 hours, and / or The manufacturing method according to any one of claims 10 to 13, wherein selectively, the sintering atmosphere is an oxygen-containing atmosphere, and more selectively, the volume fraction of oxygen gas in the sintering atmosphere is 15% to 40%.

15. A positive electrode plate comprising a positive electrode current collector and a positive electrode film layer installed on at least one surface of the positive electrode current collector, wherein the positive electrode film layer comprises a positive electrode active material according to any one of claims 1 to 9 or a positive electrode active material manufactured by the manufacturing method according to any one of claims 10 to 14. A positive electrode plate in which the content of the positive electrode active material in the positive electrode film layer is selectively 50 wt% to 99 wt%, and more selectively 85 wt% to 99 wt%, based on the total weight of the positive electrode film layer.

16. A battery comprising the positive electrode plate described in claim 15.

17. A power consumption device including the battery described in claim 16.

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