Capacity compensation additive, preparation method thereof, positive plate and battery

Abstract

The invention discloses a capacity compensation additive, a preparation method thereof, a positive plate and a battery. The capacity compensation additive comprises a core body and a coating layer coating the core body, wherein the core body comprises at least one of a regenerative lithium supplement agent and a regenerative sodium supplement agent; the coating layer includes a transition metal oxide. According to the capacity compensation additive, the capacity compensation material comprising at least one of a regenerated lithium supplement agent and a regenerated sodium supplement agent is used as a core body, so that direct regeneration and cyclic utilization of at least one of an invalid lithium supplement agent and a sodium supplement agent are realized, and lithium supplement or sodium supplement capacity can be exerted in the process of charging the battery for the first time. And the transition metal oxide-containing coating layer can improve the performance of the interface between the core body and the coating layer, plays a protection role in isolating the environment and a conductivity modification role on the core body, can play an interface synergistic role with the core body, and improves the capacity compensation role of the core body. The positive plate and the battery contain the capacity compensation additive.

Description

Technical Field

[0001] The present application belongs to the field of electrode materials, and specifically relates to a capacity compensation additive and a preparation method thereof, a positive electrode sheet, and a battery. Background Art

[0002] With the widespread application and rapid development of lithium-ion batteries, the new era places higher demands on their energy density. To improve the energy density of lithium-ion batteries, new anodes such as silicon-carbon anodes with higher specific capacity have gradually replaced graphite anodes and become a hot research topic. However, during the initial charge and discharge process of silicon-carbon anodes, a solid electrolyte interface film (SEI film) forms on their surface. This process irreversibly consumes a large amount of lithium ions (Li⁺) released from the positive electrode, resulting in a significant decrease in the battery's first cycle coulombic efficiency and loss of active lithium, thereby limiting the improvement of the battery's overall energy density.

[0003] In order to compensate for the active lithium ions consumed by the formation of solid electrolyte membrane (SEI membrane) during the first charge of lithium-ion batteries and improve the energy density of lithium-ion batteries, positive electrode lithium replenishing materials are generally added to the positive electrode of lithium-ion batteries. The positive electrode lithium replenishing materials can remove lithium from the lithium-ion battery during the first charge process, providing a large amount of irreversible capacity to compensate for the lithium ions consumed by the lithium-ion battery during the first charge process. + loss.

[0004] However, cathode lithium-supplementing materials generally suffer from poor air stability: the high amount of lithium stored in their structure makes them susceptible to reaction with oxygen, water, and carbon dioxide in the air, forming byproducts such as lithium carbonate (Li2CO3) and lithium hydroxide (LiOH). The accumulation of these byproducts leads to rapid failure of the cathode lithium-supplementing materials and an increase in residual alkalinity. The structure and morphology of these failed cathode lithium-supplementing materials are destroyed, resulting in a loss of their lithium-compensation properties. Furthermore, the high alkalinity content makes it difficult to apply the cathode slurry and increases polarization.

[0005] Currently, spent cathode lithium-replenishing materials are often considered industrial waste and require complex processes for harmless disposal, which not only increases production costs but also wastes lithium resources. Therefore, achieving efficient reuse of spent cathode lithium-replenishing materials has become a pressing technical challenge in the lithium-ion battery field. Summary of the Invention

[0006] The purpose of this application is to overcome the above-mentioned deficiencies of the prior art and provide a capacity compensation additive and a preparation method thereof and a battery containing the capacity compensation additive, so as to solve the technical problem that the existing failed positive electrode lithium supplement materials are difficult to reuse as industrial waste.

[0007] To achieve the above-mentioned application objectives, in a first aspect, the present application provides a capacity compensation additive. The capacity compensation additive of the present application comprises a core body and a coating layer coating the core body, wherein the core body comprises at least one of a regenerative lithium supplement agent and a regenerative sodium supplement agent, and the coating layer comprises a transition metal oxide, wherein the transition metal element contained in the transition metal oxide has an ionic radius of 0.6 Å or greater.

[0008] The capacity compensation additive of the present application uses a capacity compensation material including at least one of a regenerative lithium supplement agent and a regenerative sodium supplement agent as a core body, realizes the direct regeneration and recycling of at least one of the failed lithium supplement agent and the sodium supplement agent, and can play the lithium or sodium supplement capacity during the battery including the first charging process.

[0009] Furthermore, the capacity compensation additive of the embodiment of the present application is coated with a transition metal oxide coating layer containing a transition metal element with an ionic radius of 0.6 Å or more to coat the core, so that the transition metal oxide effectively improves the ionic conductivity of the coating layer, especially improves the ionic conductivity between the coating layer and the core contact interface, and improves the lithium ion migration efficiency of the coating layer; and the coating layer can improve the bulk structural stability of at least one of the regenerated lithium supplement agent and the regenerated sodium supplement agent in the core, thereby improving the compensation capacity of the core body and improving the compensation capacity of the capacity compensation additive. At the same time, the coating layer can improve the protective effect of isolating the core body from the environment, effectively alleviate the contact of the core body with adverse factors in the environment, and effectively reduce the residual alkali content of the capacity compensation additive of the embodiment of the present application.

[0010] The second aspect of the present application provides a method for preparing the capacity compensation additive of the above application. The method for preparing the capacity compensation additive of the present application comprises the following steps: In a protective atmosphere, performing a first sintering process on at least one of a spent lithium supplement agent and a spent sodium supplement agent to generate a granular material of at least one of a regenerated lithium supplement agent and a regenerated sodium supplement agent; In a protective atmosphere, mixing the material including the granular material and the transition metal oxide and then performing a second sintering process to form a coating layer on the surface of the granular material to obtain a capacity compensation additive; The ionic radius of the transition metal element contained in the transition metal oxide is greater than 0.6 Å.

[0011] The preparation method of the capacity compensation additive of the present application directly sinters and regenerates at least one of the expired lithium supplement agent and the expired sodium supplement agent to generate a regenerated lithium supplement agent and / or regenerated sodium supplement agent with lithium supplement capacity, thereby achieving the reuse of waste resources. The coating layer containing the transition metal oxide of the above-mentioned ionic radius is used to coat the granular material containing at least one of the regenerated lithium supplement agent and the regenerated sodium supplement agent, thereby improving the bulk structural stability of at least one of the regenerated lithium supplement agent and the regenerated sodium supplement agent. It can also use the transition metal element with an ionic radius of 0.6 Å or more to improve the ion migration efficiency of active ions in the coating layer, especially at the contact interface between the coating layer and the core body, and at the same time can protect the granular material from the environment.

[0012] In a third aspect, the present application provides a positive electrode sheet. The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer includes the capacity compensation additive of the above-mentioned application or the capacity compensation additive prepared by the capacity compensation additive preparation method of the present application.

[0013] Since the positive electrode sheet of the present application contains the capacity compensation additive of the above-mentioned application, the gram capacity of the positive electrode sheet of the present application and the film quality of the positive electrode active material layer contained therein are improved, thereby improving the cycle performance of the battery.

[0014] In a fourth aspect, the present application provides a battery, wherein the battery comprises a positive electrode sheet, which is the positive electrode sheet of the above-mentioned application.

[0015] Since the positive electrode sheet of the battery of the present application contains the positive electrode sheet of the above-mentioned application, the cycle performance and energy density and other properties of the battery of the present application are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the specific implementation methods or the description of the prior art. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0017] Figure 1 This is a schematic structural diagram of a capacity compensation additive according to an embodiment of the present application; Figure 2 This is a schematic diagram of a method for preparing a capacity compensation additive according to an embodiment of the present application; Figure 3These are scanning electron micrographs of the commercial lithium supplement, lithium-rich ferrite, in Examples 1 and 2 after being placed for 0 days, wherein (a) is a scanning electron micrograph of the commercial polycrystalline lithium-rich ferrite in Example 1 after being placed for 0 days, and (b) is a scanning electron micrograph of the commercial single crystal lithium-rich ferrite in Example 2 after being placed for 0 days; Figure 4 These are scanning electron microscope images of the commercial lithium-rich lithium ferrite in Examples 1 and 2 after being placed in 20% humidity air for 7 days, wherein (a) is a scanning electron microscope image of the commercial polycrystalline lithium-rich lithium ferrite in Example 1 after being placed in 20% humidity air for 7 days, and (b) is a scanning electron microscope image of the commercial single crystal lithium-rich lithium ferrite in Example 2 after being placed in 20% humidity air for 7 days; Figure 5 These are scanning electron micrographs of the commercial lithium-rich lithium ferrite in Examples 1 and 2 after being placed in 20% humidity air for 14 days, wherein (a) is a scanning electron micrograph of the commercial polycrystalline lithium-rich lithium ferrite in Example 1, and (b) is a scanning electron micrograph of the commercial single crystal lithium-rich lithium ferrite in Example 2; Figure 6 The figures are scanning electron micrographs of the capacity compensating additives in Examples 1 and 2, wherein (a) is a scanning electron micrograph of the capacity compensating additive of niobium oxide-coated regenerated polycrystalline lithium-rich ferrite in Example 1, and (b) is a scanning electron micrograph of the capacity compensating additive of niobium oxide-coated regenerated single crystal lithium-rich ferrite in Example 2; Figure 7 Figure (a) is a transmission electron micrograph of the capacity compensation additive containing a molybdenum oxide coating layer in Example 2, Figure (b) is a quantitative dispersion EDS superposition spectrum of Fe (green) and Mo (red) elements, and Figure (c) is an EDS spectrum of the Mo element; Figure 8The first cycle charging voltage-specific capacity curve of the button half-cell containing the capacity compensation additives in Example 1, Example 2 and Comparative Example 1; wherein, (a) is a first cycle charging voltage-specific capacity curve of the button half-cell containing the commercial polycrystalline lithium-rich iron oxide in Comparative Example 1 placed in 20% humidity air for 0 day, (b) is a first cycle charging voltage-specific capacity curve of the button half-cell containing the commercial polycrystalline lithium-rich iron oxide in Comparative Example 1 placed in 20% humidity air for 1 day, (c) is a first cycle charging voltage-specific capacity curve of the button half-cell containing the capacity compensation additive coated with niobium oxide in Example 1 placed in 20% humidity air for 0 day The first cycle charging voltage-specific capacity curve of the button half-cell, (d) is a first cycle charging voltage-specific capacity curve of the button half-cell containing the capacity compensation additive in Example 1 and placed in 20% humidity air for 1 day, (e) is a first cycle charging voltage-specific capacity curve of the button half-cell containing the capacity compensation additive of molybdenum oxide coated regenerated single crystal lithium-rich ferrite in Example 2 and placed in 20% humidity air for 0 day, (f) is a first cycle charging voltage-specific capacity curve of the button half-cell containing the capacity compensation additive of molybdenum oxide coated regenerated single crystal lithium-rich ferrite in Example 2 and placed in 20% humidity air for 1 day.

[0018] The accompanying drawings in the specific implementation manner are as follows: 10'-ineffective capacity compensation additive; 11'-residual alkali; 12'-ineffective capacity compensation material; 10-capacity compensation additive; 11-core; 12-coating layer. DETAILED DESCRIPTION

[0019] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application more clearly understood, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0020] In this application, the term "and / or" describes the relationship between associated objects, indicating that three possible relationships exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. A and B can be singular or plural. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0021] In this application, "at least one" means one or more, and "plurality" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" or "at least one of a, b and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can each be single or plural.

[0022] It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. Some or all of the steps can be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0023] The terms used in the embodiments of the present application are for the purpose of describing specific embodiments only and are not intended to limit the present application. The singular forms "a", "an", "the" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0024] The weights of the relevant components mentioned in the examples of this application may not only refer to the specific content of each component, but also represent the weight ratio between the components. Therefore, as long as the content of the relevant components is proportionally increased or decreased according to the examples of this application, it is within the scope disclosed in the examples of this application. Specifically, the masses described in the examples of this application may be mass units known in the chemical industry, such as μg, mg, g, and kg.

[0025] The terms "first" and "second" are used solely for descriptive purposes to distinguish objects, such as substances, from one another and should not be understood to indicate or imply relative importance or to implicitly specify the quantity of the technical features being referred to. For example, without departing from the scope of the embodiments of this application, a first XX may also be referred to as a second XX, and similarly, a second XX may also be referred to as a first XX. Thus, features defined as "first" or "second" may explicitly or implicitly include one or more of such features.

[0026] [Capacity compensation additives] In the first aspect, the present invention provides a capacity compensation additive. The capacity compensation additive of the present invention comprises a core body and a coating layer covering the core body. For example, in some embodiments, the structure of the capacity compensation additive of the present invention is as follows: Figure 1As shown, the capacity compensation additive 10 comprises a core 11 and a coating 12, which coats the core to form a core-shell structure. The core comprises at least one of a regenerative lithium supplement and a regenerative sodium supplement; the coating comprises a transition metal oxide, wherein the transition metal element contained in the transition metal oxide has an ionic radius of at least 0.6 Å.

[0027] In the capacity compensation additives of the embodiments of the present application, a regenerated lithium supplement refers to a lithium supplement that meets the battery application requirements and is formed by regenerating an expired lithium supplement, and a regenerated sodium supplement refers to a sodium supplement that meets the battery application requirements and is formed by regenerating an expired sodium supplement. The core body includes at least one of a regenerated lithium supplement and a regenerated sodium supplement, which means that the core body may contain a capacity compensation material of a regenerated lithium supplement or a capacity compensation material of a regenerated sodium supplement, or contain both a regenerated lithium supplement and a regenerated sodium supplement. The ionic radius of the transition metal element is greater than 0.6 Å, which means that the transition metal ion radius is greater than or equal to 0.6 Å, that is, as long as the transition metal element has an ionic radius of 0.6 Å or greater, it is within the scope disclosed in the embodiments of the present application.

[0028] The capacity compensation additive of the embodiment of the present application uses a capacity compensation material including at least one of a regenerative lithium supplement agent and a regenerative sodium supplement agent as a core body, realizes the direct regeneration and recycling of at least one of the failed lithium supplement agent and the sodium supplement agent, and can release at least one active ion such as active lithium ions and sodium ions during the battery, including the first charging process, to exert the lithium or sodium supplement capacity; and solves the problem of capacity loss of at least one of the sensitive lithium supplement agent and the sodium supplement agent due to destruction of the bulk structure and surface morphology, realizes the reuse of waste resources, and proposes a new technical path for the reuse of at least one of the failed lithium supplement agent and the sodium supplement agent.

[0029] Furthermore, the capacity compensation additive in the embodiment of the present application uses a transition metal oxide coating layer containing a transition metal element with an ion radius of 0.6 Å or more to coat the core. The valence state of the transition metal element is relatively high, and its high-valence metal charge is difficult to balance, thereby effectively improving the ionic conductivity of the coating layer, especially improving the ionic conductivity between the coating layer and the core contact interface, improving the lithium ion migration efficiency of the coating layer, and improving the compensation capacity of the capacity compensation additive.

[0030] In addition, a transition metal oxide having a transition metal ion radius of 0.6 Å or greater is provided in the coating layer. The ionic radius of the transition metal element is relatively large, and the corresponding valence state of the transition metal element is relatively high, which enables these transition metal oxides to be enriched on the surface of the core body and difficult to penetrate and migrate into the bulk structure of at least one of the regenerated lithium supplement agent and the regenerated sodium supplement agent contained in the core body, thereby improving the bulk structure stability of at least one of the regenerated lithium supplement agent and the regenerated sodium supplement agent, thereby improving the compensation capacity of at least one of the regenerated lithium supplement agent and the regenerated sodium supplement agent.

[0031] Secondly, the coating layer containing transition metal oxide coats the core, which can protect the core from the environment, such as isolating the air, and effectively alleviate adverse factors in the environment, such as oxygen, water, carbon dioxide, etc., from entering the core through the coating layer and contacting at least one of the regeneration lithium supplement agent and the regeneration sodium supplement agent, thereby effectively reducing the residual alkali content of the capacity compensation additive in the embodiment of the present application, improving the compensation capacity of the capacity compensation additive in the embodiment of the present application, and also improving its stability during storage, transportation and processing.

[0032] The core of the capacity compensation additive contains: Since the core body in the capacity compensation additive of the embodiment of the present application contains at least one capacity compensation material of the regenerative lithium supplement agent and the regenerative sodium supplement agent, the core body gives the capacity compensation additive of the embodiment of the present application the supplementary capacity.

[0033] In some embodiments, when the core contains a regenerated lithium replenisher, the regenerated lithium replenisher is generated by sintering an expired lithium replenisher. In the embodiment, the sintering conditions for generating the regenerated lithium replenisher from the expired lithium replenisher can be the conditions of the regenerated lithium replenisher preparation method in the capacity compensation additive preparation method of the following embodiment of the present application, such as the sintering temperature can be 300°C~900°C. The regenerated lithium replenisher obtained by sintering treatment at 300°C~900°C, optionally 500°C~800°C, can improve the lithium replenishment capacity of the regenerated lithium replenisher, and can improve the ionic conductivity between the interface of the core and the coating layer, thereby improving the lithium replenishment capacity of the capacity compensation additive.

[0034] In an exemplary embodiment, the regenerative lithium replenisher may include one or more of Li5FeO4, Li2NiO2, Li6CoO4, Li3CuO2, and Li2MnO3. These regenerative lithium replenishers have high lithium replenishment capacity and a delithiation voltage that matches the battery, enabling delithiation and replenishment during at least the initial charge of the battery.

[0035] In some embodiments, when the core contains a regenerative sodium supplement, the regenerative sodium supplement is generated by sintering an invalid sodium supplement. In the embodiment, the sintering conditions for generating the regenerative sodium supplement by sintering an invalid sodium supplement can be the conditions of the regenerative sodium supplement preparation method in the capacity compensation additive preparation method of the following embodiment of the present application, such as the sintering temperature can be 300°C~900°C. The regenerative sodium supplement obtained by sintering treatment such as 300°C~900°C, optionally 500°C~800°C, has the above-mentioned characterization characteristics, can improve the sodium supplement capacity of the regenerative sodium supplement, and can improve the ionic conductivity between the interface of the core and the coating layer, thereby improving the sodium supplement capacity of the capacity compensation additive.

[0036] In an exemplary embodiment, the regenerative sodium replenisher may include one or more of Na4FeO3, Na7Fe3O8, Na5MnO4, Na3CuO2, and Na5CoO4. These regenerative sodium replenishers have high sodium replenishment capacity and sodium removal voltages that match the battery, enabling sodium removal and replenishment during at least the initial charge of the battery.

[0037] In addition, the particle size of the core body can be a conventional particle size in the field of compensating additives, such as a conventional lithium supplement particle size or a conventional sodium supplement particle size. Of course, the particle size of the core body can also be adjusted according to the needs of the application. For example, in some embodiments, the particle size of the core body is adjusted so that, together with the coating layer, the Dv50 particle size of the capacity compensating additive in the embodiment of the present application is 1 μm~30 μm, optionally 3 μm~20 μm, and further optionally 6 μm~15 μm, which can be 1 μm, 3 μm, 5 μm, 8 μm, 10 μm, 13 μm, 15 μm, 18 μm, 20 μm, 23 μm, 25 μm, 28 μm, 30 μm, etc. Typical but non-limiting particle sizes or ranges between any two particle size values. This particle size range can increase the content ratio of at least one of the regenerated lithium supplement agent and the regenerated sodium supplement agent in the core body, thereby increasing the compensation capacity of the capacity compensation additive in the embodiment of the present application; and can also adjust the particle size range of the capacity compensation additive particles in the embodiment of the present application together with the coating layer, thereby improving the compaction density and other properties of the capacity compensation additive in the embodiment of the present application.

[0038] Capacity compensation additives contain coatings: The coating layer in the capacity compensation additive in the embodiment of the present application coats the core body, and on the basis of isolating and protecting at least one of the regenerated lithium supplement agent and the regenerated sodium supplement agent in the core body, can also play the role described above, such as having good ionic conductivity, especially the ionic conductivity between the coating layer and the core body contact interface, so that the transition metal oxide is enriched on the surface of the core body, improving the bulk structure stability of the core body compensation additive, and improving the compensation capacity of the capacity compensation additive.

[0039] In some embodiments, the valence of the transition metal element in the coating layer is greater than or equal to 5. The valence of the transition metal element can be the most stable valence state or the common valence state of the transition metal element. The ionic radius of the transition metal element in this valence range is relatively large, reaching 0.6 Å or greater, thereby enabling it to be enriched on the surface of the core to form a coating layer, thereby increasing the coverage rate of the coating layer. Furthermore, the probability of the transition metal element penetrating and migrating into the core is further reduced, thereby increasing the stability of the bulk structure of at least one of the regenerated lithium supplement agent and the regenerated sodium supplement agent in the core. Furthermore, the transition metal oxide of the transition metal element in this valence range has relatively high ionic conductivity, thereby increasing the ionic conductivity of the coating layer and further enhancing the compensation capacity of the capacity compensation additive.

[0040] In some embodiments, the transition metal element contained in the transition metal oxide in the coating layer includes one of Mo, Nb, W, and Ta. In exemplary embodiments, when the transition metal element includes Mo, the Mo oxide includes, but is not limited to, at least one of MoO3, lithium molybdenum oxide, and sodium molybdenum oxide. In exemplary embodiments, when the transition metal element includes Nb, the Nb oxide includes, but is not limited to, at least one of Nb2O5, lithium niobium oxide, and sodium niobium oxide. In exemplary embodiments, when the transition metal element includes W, the W oxide includes, but is not limited to, at least one of WO3, lithium tungsten oxide, and sodium tungsten oxide. In exemplary embodiments, when the transition metal element includes Ta, the Ta oxide includes, but is not limited to, at least one of Ta2O5, lithium tantalum oxide, and sodium tantalum oxide. The selection of these transition metal oxides, which contain transition metal elements with higher valence states and larger atomic radii, can significantly reduce the penetration and migration of these transition metal elements into the core body, and can improve the bulk structural stability of at least one of the regenerated lithium supplement agent and the regenerated sodium supplement agent in the core body. At the same time, it can effectively improve the ionic conductivity of the coating layer, thereby improving the performance and efficiency of the compensation capacity of at least one of the regenerated lithium supplement agent and the regenerated sodium supplement agent in the core body.

[0041] In some embodiments, the thickness of the coating layer is 1 nm to 1 μm, optionally 10 nm to 400 nm, and further 50 nm to 200 nm. It can be a typical but non-limiting thickness such as 10 nm, 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1 μm, or a range between any two thickness values.

[0042] In some embodiments, the coating layer accounts for 0.01% to 2% of the total mass of the capacity compensation additive in the embodiments of the present application, optionally 0.1% to 0.5%, and can be 0.01%, 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2% and other typical but non-limiting mass proportions or a range between any two mass proportion values.

[0043] On the one hand, the thickness and / or mass ratio range of the above-mentioned coating layer can effectively protect the core body from the environment, reduce the probability of contact between the core body and adverse factors in the environment including oxygen, water, carbon dioxide, etc., reduce the amount of residual alkali generated in the core body, and increase the lithium replenishment capacity of the capacity compensation additive as well as the stability of storage, transportation and processing; on the other hand, it can improve the ionic conductivity of the coating layer and improve the migration efficiency of at least one ion of lithium ions and sodium ions in the coating layer.

[0044] In some embodiments, the coating layer can be a continuous full coating layer or a non-full coating layer, wherein the non-full coating layer can include a dot-shaped or island-shaped coating layer. Relatively speaking, full coating is relatively ideal. Therefore, in some embodiments, the porosity of the coating layer can be less than 80%, optionally less than 50%, and further optionally less than 20%. In exemplary embodiments, it can be a typical but non-limiting porosity such as 0, 0.5%, 1%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or a range between any two porosity values. Controlling the porosity of the coating layer within this range can effectively improve the protective effect of the coating layer on the isolation environment of the core body, reduce the amount of residual alkali generated by the contact of the core body with air, increase the lithium replenishment capacity of the capacity compensation additive, and the stability of storage, transportation and processing; it can also improve the migration efficiency of at least one of the lithium ions and sodium ions in the coating layer.

[0045] In some embodiments, the contact interface between the coating layer and the core body further contains a lithium transition metal oxide. Since the core body generally contains residual alkali, and the transition metal oxide of the transition metal element with a large ionic radius will react with the residual alkali contained in the core body during the process of forming a coating on the core body, the above transition metal oxide will also react with the residual alkali contained in the core body, thereby generating a lithium transition metal oxide between the coating layer and the core body contact interface. The lithium transition metal oxide refers to an oxide formed by lithium and a transition metal. The lithium transition metal oxide has good ionic conductivity. On the one hand, it effectively improves the ionic conductivity of the interface between the coating layer and the core body, further improving the ionic conductivity of the coating layer; on the other hand, it enhances the bonding strength between the coating layer and the core body, improves the structural stability of the capacity compensation additive; and at the same time, it effectively reduces the residual alkali content in the core body. Therefore, the presence of the lithium transition metal oxide can effectively improve the capacity and structural stability of the capacity compensation additive, and also improve its processing performance.

[0046] In some embodiments, in the capacity compensation additive, the core includes a regeneration lithium supplement agent, and the ratio of the total molar content of lithium ions contained in the capacity compensation additive of the embodiment of the present application to the molar content of lithium ions contained in the regeneration lithium supplement agent in the core to the molar content of the transition metal element is less than 10, that is, (M 总 -M 核 ) / G<10, optionally 1-6, further optionally 2-4, in exemplary embodiments, it can be 1, 2, 3, 4, 5, 6, 7, 8, 9, etc., which are typical but non-limiting element molar ratios, or a range between any two element molar ratios. 总 is the total molar content of lithium ions contained in the capacity compensation additive of the embodiment of the present application, M 核 is the molar content of lithium ions contained in the regenerative lithium replenisher in the core of the capacity-compensating additive of this embodiment, and G is the molar content of the transition metal element contained in the capacity-compensating additive of this embodiment. When the ratio of the two is not equal to 0, it indicates that the aforementioned lithium transition metal oxide has formed in the coating layer of the capacity-compensating additive and / or at the interface between the coating layer and the core.

[0047] In some embodiments, the capacity compensating additive in each of the above embodiments can be adjusted by adjusting the core particle size and the thickness of the coating layer so that the Dv50 particle size of the capacity compensating additive is 1 μm to 30 μm, optionally 3 μm to 20 μm, and further optionally 6 μm to 15 μm. It can be 1 μm, 3 μm, 5 μm, 8 μm, 10 μm, 13 μm, 15 μm, 18 μm, 20 μm, 23 μm, 25 μm, 28 μm, 30 μm, and other typical but non-limiting particle sizes, or a range between any two particle size values. The capacity compensating additive in this particle size range has properties such as high compaction density and can, together with the positive electrode active material, improve the gram capacity and other properties of the positive electrode sheet.

[0048] [Preparation method of capacity compensation additive] In a second aspect, the present invention also provides a method for preparing the above-mentioned capacity compensation additive. The method for preparing the capacity compensation additive in the present invention comprises the following steps: S10: in a protective atmosphere, performing a first sintering process on a raw material including at least one of a spent lithium supplement agent and a spent sodium supplement agent to generate a granular material of at least one of a regenerated lithium supplement agent and a regenerated sodium supplement agent; S20: In a protective atmosphere, the granular material prepared in step S10 is mixed with a material of a transition metal oxide and then subjected to a second sintering process to form a coating layer on the surface of the granular material to obtain a capacity compensation additive.

[0049] In the method for preparing the capacity compensation additive of the embodiment of the present application, the failed lithium supplement in step S10 refers to a lithium supplement that, before being applied to the battery system, has gelled during the preparation of the electrode slurry due to various reasons including temperature and humidity, and / or is unable to effectively release lithium ions to compensate for irreversible lithium loss in the battery during the first charge of the battery. For example, the capacity of the failed lithium supplement is attenuated by more than 90% relative to the intact lithium supplement, which is a capacity attenuation of 10% relative to the intact lithium supplement. Similarly, the failed sodium supplement refers to a sodium supplement that, before being applied to the battery system, has gelled during the preparation of the electrode slurry due to various reasons including temperature and humidity, and / or is unable to effectively release sodium ions to compensate for irreversible sodium loss in the battery during the first charge of the battery, which is a capacity attenuation of 10% relative to the intact sodium supplement.

[0050] The first sintering treatment in step S10 refers to a process for regenerating at least one of the spent lithium supplement and the spent sodium supplement by subjecting the spent lithium supplement and the spent sodium supplement to a high-temperature sintering treatment, thereby causing the spent lithium supplement and the spent sodium supplement to undergo a phase change, thereby repairing structural defects and restoring the chemical activity of the spent lithium supplement and the spent sodium supplement. Therefore, the regenerated lithium supplement, as described above, refers to a lithium supplement that meets battery application requirements after a spent lithium supplement has been regenerated; the regenerated sodium supplement, as described above, refers to a sodium supplement that meets battery application requirements after a spent sodium supplement has been regenerated.

[0051] The transition metal oxide in step S20 forms the coating layer of the capacity compensation additive in the embodiment of the above application, so the ion radius of the transition metal element contained in the transition metal oxide is greater than 0.6 Å.

[0052] Therefore, the preparation method of the capacity compensation additive in the embodiment of the present application directly sinters at least one of the failed lithium supplement agent and the failed sodium supplement agent, so that the failed lithium supplement agent undergoes a phase change to generate a regenerated lithium supplement agent with a lithium supplement capacity and / or the failed sodium supplement agent undergoes a phase change to generate a regenerated sodium supplement agent with a sodium supplement capacity, thereby realizing the recycling of waste resources. A coating layer formed of a transition metal oxide containing a transition metal element with the above-mentioned ionic radius is used to coat the granular material containing at least one of the regenerated lithium supplement agent and the regenerated sodium supplement agent. The transition metal oxide in the coating layer is difficult to penetrate and migrate into the bulk structure of at least one of the regenerated lithium supplement agent and the regenerated sodium supplement agent contained in the granular material in step S10, thereby improving the bulk structural stability of at least one of the regenerated lithium supplement agent and the regenerated sodium supplement agent, thereby improving the compensation capacity of at least one of the regenerated lithium supplement agent and the regenerated sodium supplement agent. At the same time, the ionic radius of 0.6 Å or more also has a high valence. By utilizing the characteristic that high-valence metal charges are difficult to balance, the ion migration efficiency of active ions in the coating layer, especially at the contact interface between the coating layer and the core body, is improved, and the granular material is protected from the environment, thereby reducing its residual alkali content.

[0053] Step S10: The regenerative lithium supplement generated in step S10 is the regenerative lithium supplement contained in the core of the capacity compensation additive in the embodiment of the above-mentioned application. Therefore, in the embodiment, the regenerative lithium supplement can be the type of regenerative lithium supplement contained in the core of the capacity compensation additive in the embodiment of the above-mentioned application. In this case, the failed lithium supplement is also the type of failed lithium supplement corresponding to the regenerative lithium supplement contained in the core of the capacity compensation additive in the embodiment of the above-mentioned application. Similarly, the regenerative sodium supplement generated in step S10 is the regenerative sodium supplement contained in the core of the capacity compensation additive in the embodiment of the above-mentioned application. Therefore, in the embodiment, the regenerative sodium supplement can be the type of regenerative sodium supplement contained in the core of the capacity compensation additive in the embodiment of the above-mentioned application. In this case, the failed sodium supplement is also the type of failed sodium supplement corresponding to the regenerative sodium supplement contained in the core of the capacity compensation additive in the embodiment of the above-mentioned application.

[0054] In some embodiments, the raw materials in step S10 may further include a lithium source or a sodium source. In exemplary embodiments, the raw materials may include lithium metal or a lithium compound (e.g., including but not limited to lithium carbonate), sodium metal or a sodium compound (e.g., including but not limited to sodium carbonate), etc. The lithium source or sodium source is added to the raw materials in step S10 to compensate for lithium loss in the spent lithium supplement agent or sodium loss in the spent sodium supplement agent, thereby increasing the lithium replenishment capacity of the regenerated lithium supplement agent or the regenerated sodium supplement agent. In embodiments, the amount of the added lithium source or sodium source may be determined based on the type of regenerated lithium supplement agent or the regenerated sodium supplement agent and the lithium ion or sodium ion content ratio described above. For example, the amount of the added lithium source or sodium source may be, but is not limited to, approximately 5% of the weight of the spent lithium supplement agent or the spent sodium supplement agent, such as 2%, 3%, 4%, 5%, 6%, 7%, etc., to compensate for the lithium ions contained in the spent lithium supplement agent or the sodium ions contained in the spent sodium supplement agent, thereby increasing the lithium replenishment capacity of the regenerated lithium supplement agent or the regenerated sodium supplement agent.

[0055] The first sintering treatment in step S10 is to make the failed lithium supplement agent undergo phase transformation to generate a regenerated lithium supplement agent with lithium supplement capacity, and / or to make the failed sodium supplement agent undergo phase transformation to generate a regenerated sodium supplement agent with sodium supplement capacity. Figure 2As shown, the capacity compensating additive 10' contains at least one of a failed lithium-replenishing agent and a failed sodium-replenishing agent. The failed capacity compensating material 12' has failed due to changes in its bulk structure, and residual alkali 11' (e.g., hydroxide, carbonate, etc.) is generated on the surface of the failed capacity compensating material 12'. The capacity compensating additive 10 is produced during the first sintering process and the second sintering process (interface coating process) in step S20. Therefore, the temperature of the first sintering process is at least sufficient to cause a phase transition in at least one of the failed lithium-replenishing agent and the failed sodium-replenishing agent. For example, in some embodiments, the temperature of the first sintering process may be 300-900°C, optionally 500-800°C. In exemplary embodiments, the temperature may be 300°C, 400°C, 500°C, 600°C, 700°C, 800°C, 900°C, or any other typical but non-limiting temperature, or a range between any two temperatures. This temperature range can effectively cause a phase change in at least one of the raw materials of the expired lithium supplement agent and the expired sodium supplement agent, thereby increasing the compensation capacity of at least one of the regenerated lithium supplement agent and the regenerated sodium supplement agent.

[0056] In some embodiments, at a first sintering temperature of 300-900° C., the first sintering time can be 4-12 hours. In exemplary embodiments, the sintering time can be a typical but non-limiting time such as 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, or a range between any two time values. The first sintering time within this range can increase the phase transformation degree and crystal reconstruction of at least one of the spent lithium supplement and the spent sodium supplement within the first sintering temperature range, thereby increasing the purity and compensation capacity of at least one of the regenerated lithium supplement and the regenerated sodium supplement.

[0057] In some embodiments, the protective atmosphere in step S10 can be an inert atmosphere, such as at least one chemically inert atmosphere such as argon, nitrogen, or a vacuum environment, so as to reduce the adverse effects of the first sintering treatment environment on at least one of the generated regenerated lithium supplement agent and the regenerated sodium supplement agent, such as improving the purity of at least one of the regenerated lithium supplement agent and the regenerated sodium supplement agent, thereby improving the compensation capacity of at least one of the generated regenerated lithium supplement agent and the regenerated sodium supplement agent.

[0058] Step S20: The coating layer formed on the surface of the granular material in step S20 is the coating layer in the capacity compensation additive in the above-mentioned embodiment of the application. Therefore, in the embodiment, the relevant film performance parameters of the transition metal oxide raw material and the formed coating layer in step S20 can be those described in the coating layer in the capacity compensation additive in the above-mentioned embodiment of the application. In order to save space, the transition metal oxide in step S20 and the formed coating layer will not be described in detail here.

[0059] In some embodiments, the mixing ratio of the particulate material and the transition metal oxide can be adjusted and controlled according to the mass ratio of the core to the coating layer or the thickness of the coating layer in the capacity compensation additive in the above application embodiments.

[0060] In the embodiment, the mixing treatment of the granular material and the transition metal oxide may include but is not limited to ball milling and other treatments, as long as the two can be evenly dispersed, which can improve the uniformity of the surface distribution of the granular material prepared by the transition metal oxide in step S10, thereby improving the uniformity of the thickness of the coating layer and other related film layer properties, and improving the synergistic effect between the coating layer and the surface of the granular material and the isolation and protection of the core body.

[0061] The second sintering treatment in step S20 is to enable the transition metal oxide to sinter on the surface of the granular material to form a coating layer to coat the core. Therefore, in some embodiments, the temperature of the second sintering treatment in step S20 should be a temperature that enables the transition metal oxide to be sintered. For example, in the embodiment, the temperature of the second sintering treatment can be 300~500℃. In the exemplary embodiment, the temperature can be a typical but non-limiting temperature such as 300℃, 400℃, 500℃, or a range between any two temperature values. This temperature range can effectively allow the transition metal oxide to be sintered on the surface of the granular material to form a coating layer, and can improve the film quality of the formed coating layer, such as having the relevant properties of the coating layer in the capacity compensation additive in the above-mentioned application embodiment, improving the synergistic effect between the coating layer and the surface of the granular material and improving the insulation and protection effect on the granular material.

[0062] Since the regenerated lithium-supplementing agent and the regenerated sodium-supplementing agent prepared in step S10 generally still contain residual alkali, the second sintering treatment temperature can also increase the reaction between the transition metal oxide and the residual alkali contained in the granular material, especially the residual alkali contained on the surface of the granular material, to form lithium transition metal oxide, thereby effectively reducing the residual alkali content of the core of the generated capacity compensation additive. The generated lithium transition metal oxide also effectively enhances the bonding strength between the core of the prepared capacity compensation additive and the contact interface of the coating layer. The lithium transition metal oxide has good ionic conductivity, improves the lithium ion conductivity of the coating layer, and improves the lithium-supplementing capacity of the capacity compensation additive. In addition, the second sintering treatment temperature can also reduce the adverse effects on the granular material, such as reducing the infiltration and migration of transition metal elements into the granular material and improving the stability of the crystal structure of the granular material.

[0063] In the embodiment, at a second sintering temperature of 300-500°C, the second sintering time can be 1-4 hours. In exemplary embodiments, the sintering time can be a typical but non-limiting sintering time such as 1 hour, 2 hours, 3 hours, 4 hours, or a range between any two sintering time values. The second sintering time within this range can improve the film quality and uniformity of the formed coating layer within the second sintering temperature range, thereby enhancing the coating layer's role as a coating layer in the capacity compensation additive of the above-mentioned application embodiments.

[0064] In some embodiments, the protective atmosphere in step S20 can be an inert atmosphere, such as at least one chemically inert atmosphere such as argon, nitrogen, or a vacuum environment, so as to reduce the adverse effects of the second sintering treatment environment on at least one of the regenerated lithium supplement agent and the regenerated sodium supplement agent in the granular material, such as improving the purity of at least one of the regenerated lithium supplement agent and the regenerated sodium supplement agent, etc., and at the same time, it can also avoid the generation of other impurities in the coating layer, such as reacting with at least one of the regenerated lithium supplement agent and the regenerated sodium supplement agent in the granular material to generate impurities including residual alkali in the coating layer.

[0065] [Positive electrode] In a third aspect, embodiments of the present application further provide a positive electrode sheet. The positive electrode sheet of the embodiments of the present application includes a current collector and a positive electrode active material layer disposed on at least one surface of the current collector. The positive electrode active material layer includes a positive electrode active material and a lithium replenisher, and the lithium replenisher includes the capacity compensation additive of the embodiments of the present application.

[0066] Because the positive electrode sheet of the embodiment of the present application contains the capacity compensation additive of the embodiment of the present application, and because the capacity compensation additive of the embodiment of the present application has high compensation capacity and good processing properties, the gram capacity of the positive electrode sheet of the embodiment of the present application and the film quality of the positive electrode active material layer contained therein are both improved, thereby improving the cycle performance of the battery.

[0067] In some embodiments, the mass ratio of the capacity-compensating additive of the above-mentioned application embodiment contained in the positive electrode sheet to the positive electrode active material in the positive electrode sheet can be (0.1-10):100, optionally (0.1-5):100, and further optionally (0.1-3):100. In exemplary embodiments, the mass ratio can be 0.1:100, 0.5:100, 1:100, 2:100, 3:100, 4:100, 5:100, or other typical but non-limiting mass ratios, or a range between any two mass ratios. Capacity-compensating additives within this content range can effectively exert compensation capacity and improve the battery's electrical properties, such as initial coulombic efficiency and energy density.

[0068] In some embodiments, the positive electrode active material in the positive electrode active material layer of the positive electrode sheet can be a lithium battery positive electrode active material or a sodium battery positive electrode active material. In the embodiments, when a lithium battery positive electrode active material is included, the capacity compensating agent contained in the core of the capacity compensating additive in the corresponding embodiment of the above-mentioned application includes a regenerative lithium replenishing agent, and the corresponding battery can be a lithium battery; in the embodiments, when a sodium battery positive electrode active material is included, the capacity compensating agent contained in the core of the capacity compensating additive in the corresponding embodiment of the above-mentioned application includes a regenerative sodium replenishing agent, and the corresponding battery can be a sodium battery.

[0069] In some embodiments, the positive electrode current collector of the positive electrode sheet may be, but is not limited to, aluminum foil. The positive electrode active material layer of the positive electrode sheet includes components such as a positive electrode active material, a binder, and a conductive agent. The content and material types of the positive electrode active material, binder, and conductive agent may be conventional in the battery field.

[0070] For example, in the embodiment, when the positive electrode active material in the positive electrode active material layer is a lithium battery positive electrode active material, the lithium battery positive electrode active material may include one or more of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxyphosphate, lithium fluorovanadium phosphate, lithium titanate, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide. Similarly, when the positive electrode active material layer is a sodium battery positive electrode active material, the sodium battery positive electrode active material may include one or more of a sodium battery layer oxygen positive electrode material and a sodium battery polyanion positive electrode material.

[0071] In an embodiment, the content of the binder in the positive electrode active material layer can be 1 wt% to 20 wt%, optionally 1 wt% to 10 wt%, and further optionally 1 wt% to 3 wt%. In a specific embodiment, the content of the binder can be 1 wt%, 2 wt%, 3 wt%, 5 wt%, 10 wt%, 20 wt%, and other typical but non-limiting contents. In a specific embodiment, the binder includes one or more of polyvinylidene fluoride, soluble polytetrafluoroethylene, styrene-butadiene rubber, hydroxypropyl methylcellulose, methylcellulose, carboxymethyl cellulose, polyvinyl alcohol, acrylonitrile copolymer, sodium alginate, chitosan, and chitosan derivatives.

[0072] In an embodiment, the content of the conductive agent in the positive electrode active material layer can be 1 wt% to 20 wt%, optionally 1 wt% to 10 wt%, and further optionally 1 wt% to 3 wt%. In a specific embodiment, the content of the binder can be 1 wt%, 2 wt%, 3 wt%, 5 wt%, 10 wt%, 20 wt%, and other typical but non-limiting contents. In a specific embodiment, the conductive agent includes one or more of graphite, carbon black, acetylene black, graphene, carbon fiber, C60, and carbon nanotubes.

[0073] In the embodiment, the preparation process of the positive electrode sheet can be: mixing the positive electrode active material, conductive agent, binder and capacity compensation additive to obtain positive electrode slurry, coating the positive electrode slurry on the current collector, and preparing the positive electrode sheet through steps such as drying, rolling, and die cutting.

[0074] [Battery] Fourthly, the embodiments of the present application further provide a battery. The battery of the embodiments of the present application includes a positive electrode sheet, a negative electrode sheet, a separator and / or a solid electrolyte disposed between the positive and negative electrode sheets, and other necessary components and electrolytes, and of course also includes other necessary or auxiliary components. Among them, the positive electrode sheet is the positive electrode sheet of the embodiment of the above-mentioned application, that is, it includes the capacity compensation additive of the embodiment of the above-mentioned application.

[0075] Since the positive electrode sheet of the battery of the present embodiment is the same as that of the above-mentioned embodiment, and thus contains the capacity-compensating additive of the above-mentioned embodiment, the capacity-compensating additive of the above-mentioned embodiment can, at least during the initial charging process, provide at least one of active lithium ions and sodium ions, thereby improving the battery's cycle performance and energy density.

[0076] The negative electrode sheet contained in the battery of the embodiment of the present application can be a conventional negative electrode sheet. For example, when the battery is a lithium battery, the negative electrode sheet is a metal lithium foil or other electrode sheet containing a negative electrode active material; when the battery is a sodium battery, the negative electrode sheet is a metal sodium foil or other electrode sheet containing a negative electrode active material.

[0077] The battery of the embodiment of the present application can be assembled according to the existing assembly method of wound cell batteries, cylindrical batteries or laminated cell batteries.

[0078] [Example] The following uses a number of specific embodiments to illustrate the capacity compensation additive and its preparation method as well as the related properties of the capacity compensation additive in the embodiments of the present application.

[0079] 1. Capacity compensation additive and preparation method thereof: Example 1: This embodiment provides a capacity compensation additive (regeneration lithium supplement additive) and a preparation method thereof. The regeneration lithium supplement additive comprises regeneration polycrystalline lithium-rich ferrite particles and a coating layer containing niobium oxide that coats the regeneration polycrystalline lithium-rich ferrite particles.

[0080] The preparation method of the regeneration lithium supplement additive of this embodiment comprises the following steps: S1: Grind the spent polycrystalline lithium-rich iron oxide (40 g of commercial polycrystalline lithium-rich iron oxide as raw material, place it in air at room temperature and 20% humidity for 14 days) into a uniform powder, heat it in a tube furnace at 600°C in an argon atmosphere for 4 hours, cool it to room temperature, and then crush it; S2: Add 0.2 g of niobium oxide to step S1 and grind it evenly. Place the ground product in a tube furnace and heat it at 300° C. in an argon atmosphere for 4 hours. After natural cooling, take it out and crush it, and sieve it to obtain the target product, which is a regenerated lithium supplement material containing a niobium oxide coating layer coated with regenerated polycrystalline lithium-rich lithium ferrite.

[0081] Example 2: This embodiment provides a capacity compensation additive (regeneration lithium supplement additive) and a preparation method thereof. The regeneration lithium supplement additive comprises regeneration single crystal lithium-rich ferrite particles and a coating layer containing molybdenum oxide that covers the regeneration single crystal lithium-rich ferrite particles.

[0082] The preparation method of the regeneration lithium supplement additive of this embodiment comprises the following steps: S1: Grind the failed single crystal lithium-rich iron oxide (failure treatment: take 100g of commercial single crystal lithium-rich iron oxide as raw material, place it in air at room temperature and 20% humidity for 14 days) into a uniform powder, heat it in a tube furnace at 500℃ in an argon atmosphere for 12h, cool it to room temperature, and then crush it; S2: Add 1 g of molybdenum oxide to step S1 and grind it evenly. Place the ground product in a tube furnace and heat it at 450°C in an argon atmosphere for 2 hours. After natural cooling, take it out, crush it, and sieve it to obtain the target product, which is a regenerated lithium supplement material containing a molybdenum oxide coating layer coated on a regenerated single crystal lithium-rich lithium ferrite.

[0083] Example 3: This embodiment provides a capacity compensation additive (regeneration lithium supplement additive) and a preparation method thereof. The regeneration lithium supplement additive comprises regeneration single-crystal lithium-rich nickelate particles and a coating layer containing tungsten oxide that covers the regeneration single-crystal lithium-rich nickelate particles.

[0084] The preparation method of the regeneration lithium supplement additive of this embodiment comprises the following steps: S1: Grind the failed single crystal lithium-rich nickelate (failure treatment: take 50g of commercial single crystal lithium-rich nickelate as raw material, place it in air at room temperature and 20% humidity for 14 days) into a uniform powder, heat it in a tube furnace at 800℃ in an argon atmosphere for 10h, cool it to room temperature, and then crush it; S2: Add 1 g of tungsten oxide to step S1 and grind it evenly. Place the ground product in a tube furnace and heat it at 350°C in an argon atmosphere for 4 hours. After natural cooling, take it out and crush it, sieve it, and obtain the target product, which is a regenerated lithium supplement material containing a tungsten oxide coating layer coated with a regenerated single crystal lithium-rich lithium nickelate.

[0085] Example 4: This embodiment provides a capacity compensation additive (regeneration lithium supplement additive) and a preparation method thereof. The regeneration lithium supplement additive comprises regenerated polycrystalline lithium-rich nickelate particles and a coating layer containing tantalum oxide that coats the regenerated polycrystalline lithium-rich nickelate particles.

[0086] The preparation method of the regeneration lithium supplement additive of this embodiment comprises the following steps: S1: Grind the spent polycrystalline lithium-rich nickelate (80g of commercial polycrystalline lithium-rich nickelate as raw material, place it in air at room temperature and 20% humidity for 14 days) into a uniform powder, heat it in a tube furnace at 750°C in an argon atmosphere for 12 hours, cool it to room temperature, and then crush it; S2: Add 0.8 g of tantalum oxide to step S1 and grind it evenly. Place the ground product in a tube furnace at 500° C. in an argon atmosphere and heat it for 1 hour. After natural cooling, take it out, crush it, and sieve it to obtain the target product, which is a regenerated lithium supplement material containing a tantalum oxide coating layer coated with regenerated polycrystalline lithium-rich lithium nickelate.

[0087] Example 5: This embodiment provides a capacity compensation additive (regeneration lithium supplement additive) and a preparation method thereof. The regeneration lithium supplement additive comprises regenerated single-crystal lithium-rich lithium cobalt oxide particles and a coating layer containing molybdenum oxide that coats the regenerated single-crystal lithium-rich lithium cobalt oxide particles.

[0088] The preparation method of the regeneration lithium supplement additive of this embodiment comprises the following steps: S1: Grind the failed single crystal lithium-rich cobalt oxide (failure treatment: take 60g of commercial single crystal lithium-rich cobalt oxide as raw material, place it in air at room temperature and 20% humidity for 14 days) into a uniform powder, heat it in an argon atmosphere at 600℃ for 10h in a tube furnace, cool it to room temperature, and then crush it; S2: Add 1 g of molybdenum oxide to step S1 and grind it evenly. Place the ground product in a tube furnace at 450° C. in an argon atmosphere and heat it for 3 hours. After natural cooling, take it out, crush it, and sieve it to obtain the target product, which is a regenerated lithium supplement material containing a regenerated single crystal lithium-rich lithium cobalt oxide coated with a molybdenum oxide coating layer.

[0089] Example 6: This embodiment provides a capacity compensation additive (regeneration lithium supplement additive) and a preparation method thereof. The regeneration lithium supplement additive includes regenerated lithium oxalate particles and a coating layer containing molybdenum oxide that covers the regenerated lithium oxalate particles.

[0090] The preparation method of the regeneration lithium supplement additive of this embodiment comprises the following steps: S1: Grind the spent lithium oxalate (spend treatment: take 60g of commercial lithium oxalate as raw material, place it in air at room temperature and 20% humidity for 14 days) into a uniform powder, heat it in a tube furnace at 600℃ in an argon atmosphere for 10h, cool it to room temperature, and then crush it; S2: Add 1 g of molybdenum oxide to step S1 and grind it evenly. Place the ground product in a tube furnace at 450°C in an argon atmosphere and heat it for 3 hours. After natural cooling, take it out, grind it, and sieve it to obtain the target product, which is a regenerated lithium supplement material containing a molybdenum oxide coating layer coated with regenerated lithium oxalate.

[0091] Example 7: This embodiment provides a capacity compensation additive (regeneration sodium supplement additive) and a preparation method thereof. The regeneration sodium supplement additive comprises regenerated single crystal Na7Fe3O8 particles and a coating layer containing molybdenum oxide that coats the regenerated single crystal Na7Fe3O8 particles.

[0092] The preparation method of the regeneration sodium supplement additive of this embodiment comprises the following steps: S1: Grind the failed single crystal Na7Fe3O8 (failure treatment: take 50g of commercial single crystal Na7Fe3O8 as raw material, place it in air at room temperature and 20% humidity for 7 days) into a uniform powder, heat it in a tube furnace at 750℃ in an argon atmosphere for 6h, cool it to room temperature, and then crush it; S2: Add 0.5 g of molybdenum oxide to step S1 and grind it evenly. Place the ground product in a tube furnace at 500°C in an argon atmosphere and heat it for 3 hours. After natural cooling, take it out and crush it, sieve it, and obtain the target product, which is a regenerated sodium supplement material containing a molybdenum oxide coating layer coated with regenerated single crystal Na7Fe3O8.

[0093] Comparative Example 1: This comparative example provides a polycrystalline lithium-rich lithium ferrite, which is the commercial polycrystalline lithium-rich lithium nickelate in step S1 of Example 1 and has not undergone the deterioration treatment in step S1 of Example 1.

[0094] Comparative Example 2: This comparative example provides a single-crystal lithium-rich lithium ferrite, which is the commercial single-crystal lithium-rich lithium nickelate obtained in step S1 of Example 2 and has not undergone the deterioration treatment in step S1 of Example 2.

[0095] Comparative Example 3: This comparative example provides a single-crystal lithium-rich lithium cobalt oxide. The single-crystal lithium-rich lithium cobalt oxide is the commercial single-crystal lithium-rich lithium cobalt oxide in step S1 of Example 5 and has not undergone the failure treatment in step S1 of Example 5.

[0096] Comparative Example 4: This comparative example provides a lithium oxalate, which is the commercial lithium oxalate used in step S1 of Example 6 and has not undergone the invalidation treatment in step S1 of Example 6.

[0097] Comparative Example 5: This comparative example provides a capacity compensation additive (regenerative lithium-replenishing additive) and its preparation method. The regenerative lithium-replenishing additive differs from the capacity compensation additive in Example 1 in that the niobium oxide in the coating layer of the capacity compensation additive in Example 1 is replaced with aluminum oxide.

[0098] Comparative Example 6: This comparative example provides a capacity compensation additive and a preparation method thereof. The capacity compensation additive differs from the capacity compensation additive in Example 1 in that the regenerated polycrystalline lithium-rich ferrite particles contained in the regenerated capacity compensation additive in Example 1 are replaced with commercial polycrystalline lithium-rich ferrite particles in step S1 of Example 1. In other words, a non-regenerated lithium compensation material comprising commercial polycrystalline lithium-rich ferrite coated with a niobium oxide-containing coating layer is used.

[0099] The characterization data related to the capacity compensation additives in the above-mentioned embodiments and comparative examples are shown in Table 1 below.

[0100] 2. Testing of performance related to capacity compensation additives: 2.1 Scanning electron microscopy analysis of capacity compensation additives: The commercial lithium supplement agents and the prepared capacity compensation additives in Examples 1 to 7 were analyzed by scanning electron microscopy. The scanning electron microscopy images of the commercial polycrystalline lithium-rich lithium ferrite in Example 1 after 0 days of storage are shown in FIG. Figure 3 As shown in Figure (a), the scanning electron microscope image of the commercial polycrystalline lithium-rich ferrite in Example 1 placed in 20% humidity air for 7 days is as follows Figure 4 As shown in Figure (a), the scanning electron microscope image of the commercial polycrystalline lithium-rich lithium ferrite in Example 1 after being placed in 20% humidity air for 14 days is as follows: Figure 5 As shown in Figure (a), the scanning electron microscope image of the capacity compensation additive in Example 1 is as follows Figure 6 As shown in Figure (a); the scanning electron microscope image of the commercial single crystal lithium-rich lithium ferrite in Example 2 after 0 days is as shown in Figure Figure 3 As shown in Figure (b), the scanning electron microscope image of the commercial single crystal lithium-rich ferrite in Example 2 placed in 20% humidity air for 7 days is as follows Figure 4 As shown in Figure (b), the scanning electron microscope image of the commercial single crystal lithium-rich lithium ferrite in Example 2 was placed in 20% humidity air for 14 days. Figure 5 As shown in Figure (b), the scanning electron microscope image of the capacity compensation additive in Example 2 is as follows Figure 6 As shown in Figure (b). Figures 3 to 5It can be seen that as the time of commercial polycrystalline lithium-rich iron oxide and commercial single crystal lithium-rich iron oxide in the air increases, the surface of both gradually becomes rough and the morphology is destroyed, indicating that the existing commercial lithium supplement additives gradually degrade in the air, eventually leading to a decrease in the first cycle charge capacity of the material and even agglomeration of the slurry. Figure 6 is Figure 5 The regenerated lithium-replenishing additive in Example 1 obtained by regenerating and coating the failed commercial polycrystalline lithium-rich ferrite that has been completely degraded for 14 days, and the regenerated lithium-replenishing additive in Example 2 obtained by regenerating and coating the commercial single crystal lithium-rich ferrite, can be seen that the surfaces of the regenerated lithium-replenishing additives in Example 1 and Example 2 have become clean and smooth, and the morphology and structure of the materials have been repaired.

[0101] 2.2 Transmission electron microscopy and X-ray spectroscopy analysis of capacity compensation additives: The capacity compensation additives in Examples 1 to 7 were analyzed by transmission electron microscopy and X-ray spectroscopy (EDS). The EDS image of the capacity compensation additive containing the molybdenum oxide coating layer in Example 2 is as follows: Figure 7 As shown in Figure (a), the EDS superposition of Fe (green) and Mo (red) elements is as follows Figure 7 As shown in Figure (b), the EDS spectrum of Mo element is as follows Figure 7 As shown in Figure (c). Figure 7 As can be seen in Figure (a), molybdenum oxide forms a continuous, uniform coating with a thickness of about 30 nm on the surface of the regenerated single crystal lithium iron oxide; combined with Figure 7 As can be seen in Figures (b) and (c), the red color representing the Mo element is distributed around the green area representing the Fe element, which means that the Mo element is distributed in the surface layer of the capacity compensation additive. This proves that the Mo element is only distributed in the coating layer and is evenly distributed in the coating layer, and has not diffused into the bulk structure of the core-regenerated single crystal lithium ferrite-rich lithium ion battery. Therefore, the transmission electron microscopy and X-ray spectroscopy (EDS) images show that the coating material of the capacity compensation additive in the embodiment of the present application is enriched on the surface, which can achieve continuous and uniform coating. This is beneficial to improve the ionic conductivity of the material, while isolating it from air and improving air stability.

[0102] Furthermore, the XPS test results of the capacity compensation additive in Example 2 showed that the molar ratio of Li:Fe:Mo:O in the capacity compensation additive in Example 2 was 41:7.5:1:35, which proved that, except for the regenerated single crystal lithium ferrite-rich particles LFO, the remaining Li and Mo molar ratio in the capacity compensation additive was Li:Mo=3.5:1, indicating that MO3 and Li4MoO5 existed in the coating layer of the capacity compensation additive in Example 2 at the same time, and also proved that Li4MoO5 was generated in the coating layer and / or at the interface between the coating layer and the core body.

[0103] 2.3: The capacity-compensating additives provided in each of Examples 1 to 7 and Comparative Examples 1 to 6 were divided into four groups. The color changes of the capacity-compensating additives in each group were observed under an electron microscope at room temperature and 20% humidity for 0 days, 1 day, 7 days, and 14 days. The color change results for each group of capacity-compensating additives are shown in Table 1 below.

[0104] 2.4 Specific capacity test of capacity compensation additive related performance: The capacity compensation additives provided in Examples 1 to 7 and Comparative Examples 1 to 6 were used as positive electrode materials to prepare positive electrode sheets, and lithium ion button half-cells were assembled according to the following methods: 1) Positive electrode: The capacity compensation additives provided in Examples 1 to 7 and Comparative Examples 1 to 6 were respectively used as positive electrode active materials for lithium-ion button half-cells. Under the same conditions, the capacity compensation additives provided in each example were divided into 4 groups, and placed in air at room temperature and a humidity of 20% for 0 days, 1 day, 7 days, and 14 days respectively; then each group of capacity compensation additives was homogenized at room temperature and in air with a humidity of 20% in a mass ratio of 8:1:1 to prepare positive electrode slurries, and the four groups of prepared positive electrode slurries were respectively coated on aluminum foil, dried under vacuum at 120°C for 2 hours, rolled, and cut to obtain four groups of positive electrode sheets. Among them, the capacity compensating additive provided in Example 1 was respectively assembled into four groups of button half-cells (such as a button half-cell containing the capacity compensating additive after standing in air for 0 days, a button half-cell containing the capacity compensating additive after standing in air for 1 day, a button half-cell containing the capacity compensating additive after standing in air for 7 days, and a button half-cell containing the capacity compensating additive after standing in air for 14 days), the capacity compensating additive provided in Example 2 was respectively assembled into another four groups of button half-cells, and so on. The capacity compensating additive provided in Comparative Example 7 was assembled into one and four groups of button half-cells.

[0105] 2) Negative electrode: The negative electrode uses metallic lithium sheet.

[0106] 3) Diaphragm: The diaphragm uses PP (polypropylene) diaphragm.

[0107] 4) Electrolyte: The electrolyte is a 1 mol / L LiPF6 solution, and the solvent is composed of EC (ethylene carbonate) and DEC (diethyl carbonate) in a volume ratio of 1:1.

[0108] 5) Assembly of secondary batteries: Four sets of positive electrode sheets, negative electrode sheets, electrolytes, and separators containing the capacity-compensating additives of each of the above embodiments were assembled into four sets of button half-cells in an argon atmosphere in a glove box. For example, four sets of button half-cells assembled from four sets of positive electrode sheets containing the capacity-compensating additive of Example 1 were used as an example. The four sets included button half-cells containing the capacity-compensating additive of Example 1 after standing in air for 0 days, a button half-cell containing the capacity-compensating additive of Example 1 after standing in air for 1 day, a button half-cell containing the capacity-compensating additive of Example 1 after standing in air for 7 days, and a button half-cell containing the capacity-compensating additive of Example 1 after standing in air for 14 days.

[0109] 2.4.1: The four groups of positive electrode sheets coated with the capacity compensation additive in each of the above embodiments were observed to determine whether the positive electrode sheets were in normal condition according to industry quality requirements. The results of the observations of the positive electrode sheets are shown in Table 2 below.

[0110] 2.4.2: Test the voltage-capacity curve of the first charge cycle for each group of button-type half-cells. Test the voltage-capacity curve of the first charge cycle for each group of button-type half-cells under the following conditions: Figure 8 The first cycle charging voltage-specific capacity curve of the button half-cell containing the commercial polycrystalline lithium-rich iron oxide in Comparative Example 1 placed in 20% humidity air for 0 days is shown in FIG. Figure 8 As shown in Figure (a), the first cycle charging voltage-specific capacity curve of the button half-cell containing the commercial polycrystalline lithium-rich iron oxide in comparative example 1 placed in 20% humidity air for 1 day is shown in Figure (b) of 8; the first cycle charging voltage-specific capacity curve of the button half-cell containing the capacity compensation additive of the niobium oxide-coated regenerated polycrystalline lithium-rich iron oxide in Example 1 placed in 20% humidity air for 0 day is shown in Figure 8 As shown in Figure (c), the first cycle charging voltage-specific capacity curve of the button half-cell containing the capacity compensation additive in Example 1 placed in 20% humidity air for 1 day is as follows Figure 8 As shown in Figure (d); the first cycle charging voltage-specific capacity curve of the button half-cell containing the capacity compensation additive of the molybdenum oxide-coated regenerated single crystal lithium-rich lithium ferrite in Example 2 placed in 20% humidity air for 0 days is as shown in Figure (d); Figure 8 As shown in Figure (e), the first cycle charging voltage-specific capacity curve of the button half-cell containing the capacity compensation additive of the molybdenum oxide-coated regenerated single crystal lithium-rich ferrite in Example 2 placed in 20% humidity air for 1 day is as follows Figure 8 As shown in Figure (f). Figure 8 As can be seen from Figures (a) and (b), for ordinary commercial capacity compensation additives, after only one day of exposure to 20% humidity air, the specific capacity dropped significantly due to the destruction of the morphology and structure. Further testing found that the capacity compensation additive had lost its lithium replenishment effect after being placed for 14 days. Figure 8As can be seen in Figures (a) and (b) and (c) through (f), the specific capacity of the core-shell capacity compensator provided in the examples of this application has been restored and even exceeds that of commercial capacity compensating additives, demonstrating that the capacity compensating additive in the examples of this application effectively restores the morphology and structure of the failed lithium-replenishing additive, facilitating capacity utilization. After being placed in 20% humidity air for one day, the specific capacity of the capacity compensating additive in the examples of this application remained essentially unchanged, demonstrating its improved air stability.

[0111] Table 1

[0112] Table 2

[0113] Combined with Table 1 above, the test results in Table 2 show that for common commercial capacity-compensating additives, after only one day of exposure to 20% humidity, the specific capacity drops significantly due to structural damage. Further exposure leads to material failure, resulting in residual alkali, color changes, and gelation of the coating slurry, leading to poor processing performance. Capacity-compensating additives that have been exposed for more than seven days lose their lithium-replenishing function and are therefore ineffective.

[0114] The capacity compensator of the embodiment of the present application is treated by coating the regenerated compensating additive with a transition metal oxide in a specific ionic radius range. The specific capacity of the capacity compensator has been restored, even higher than that of the commercial capacity compensating additive. This shows that the capacity compensator of the embodiment of the present application has restored the morphology and structure of the failed capacity compensating additive, which is conducive to the performance of the capacity of the capacity compensator. After being placed in 20% humidity air for 1 day, the specific capacity of the capacity compensator of the embodiment of the present application has basically no loss. After being placed in 20% humidity air for 14 days, the specific capacity of the capacity compensator of the embodiment of the present application is basically stable and unchanged, indicating that the coating layer of the capacity compensator of the embodiment of the present application has played a protective role in isolating the regenerated capacity compensating additive in the core from air, significantly improving the air stability of the capacity compensator.

[0115] The above embodiments merely illustrate several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A capacity compensation additive, characterized in that: The invention comprises a core body and a coating layer coating the core body, wherein the core body comprises at least one of a regenerated lithium supplement agent and a regenerated sodium supplement agent, and the coating layer comprises a transition metal oxide, and the ionic radius of the transition metal element contained in the transition metal oxide is greater than 0.6 Å.

2. The capacity compensation additive according to claim 1, characterized in that: The valence of the transition metal element is greater than or equal to 5; and / or The transition metal element includes one of Mo, Nb, W and Ta.

3. The capacity compensation additive according to claim 1 or 2, characterized in that: The coating layer includes at least one of the following (1) to (4): (1) The thickness of the coating layer is 1 nm to 1 μm; (2) The coating layer accounts for 0.01% to 2% of the total mass of the capacity compensation additive; (3) The porosity of the coating layer is less than 80%; (4) The contact interface between the coating layer and the core further contains lithium transition metal oxide.

4. The capacity compensation additive according to claim 1, wherein: The regenerated lithium supplement agent is generated by sintering the failed lithium supplement agent; and / or The regenerated sodium supplement agent is generated by sintering the failed sodium supplement agent.

5. The capacity compensation additive according to any one of claims 1, 2 and 4, characterized in that: The regeneration lithium supplement agent includes one or more of Li5FeO4, Li2NiO2, Li6CoO4, Li3CuO2, Li2MnO3; and / or The regeneration sodium supplement includes one or more of Na4FeO3, Na7Fe3O8, Na5MnO4, Na3CuO2, and Na5CoO4.

6. The capacity compensation additive according to any one of claims 1, 2 and 4, characterized in that: The particle size of the capacity compensation additive is 1 μm to 30 μm; and / or The core body includes a regenerative lithium supplement agent, and the ratio of the difference between the total molar content of lithium ions contained in the capacity compensation additive and the molar content of lithium ions contained in the regenerative lithium supplement agent to the molar content of the transition metal element is less than 10.

7. A method for preparing a capacity compensation additive, characterized in that: The steps include: In a protective atmosphere, performing a first sintering process on at least one of a spent lithium supplement agent and a spent sodium supplement agent to generate a granular material of at least one of a regenerated lithium supplement agent and a regenerated sodium supplement agent; In a protective atmosphere, mixing the material including the granular material and the transition metal oxide and then performing a second sintering process to form a coating layer on the surface of the granular material to obtain a capacity compensation additive; The ionic radius of the transition metal element contained in the transition metal oxide is greater than 0.6 Å.

8. The preparation method according to claim 7, wherein The temperature of the first sintering treatment is 300-900°C and the time is 4-12 hours; and / or The second sintering treatment is performed at a temperature of 300-500°C for a time of 1-4 hours; and / or The valence of the transition metal element is greater than or equal to 5.

9. A positive electrode sheet comprising a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, characterized in that: The positive electrode active material layer includes the capacity compensation additive according to any one of claims 1 to 6 or the capacity compensation additive prepared by the preparation method according to any one of claims 7 to 8.

10. A battery comprising a positive electrode, characterized in that: The positive electrode sheet is the positive electrode sheet according to claim 9.

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