Composite lithium-rich material, preparation method thereof and battery

Abstract

The invention discloses a composite lithium-rich material, a preparation method thereof and a battery. The composite lithium-rich material comprises a first lithium-rich material, a second lithium-rich material and a linking group, wherein the linking group is connected between the first lithium-rich material and the second lithium-rich material. And the composite lithium-rich material is good in structural stability, good in granular performance and good in dispersity. A positive plate in the battery contains the composite lithium-rich material.

Description

Technical Field

[0001] The present application belongs to the field of batteries, and specifically relates to a composite lithium-rich material, a preparation method thereof, and a battery. Background Art

[0002] During the initial charge and discharge process of lithium-ion batteries, a series of complex chemical reactions will occur between the electrode material and the electrolyte, forming a solid electrolyte interface (SEI) film on the electrode surface. This SEI film is crucial for the stable operation of the battery, but it will also consume some active lithium ions, leading to the initial loss of battery capacity. In order to increase the initial capacity of lithium-ion batteries and maintain their long-term stability, the industry has been exploring effective solutions.

[0003] Among them, one method that has been widely studied is to add lithium-rich materials, such as lithium supplement additives, to the battery cells. These lithium-rich materials can release lithium during the first charge and discharge process of the battery, providing the lithium ions required for the formation of the SEI film, thereby compensating for the active lithium lost due to the formation of the SEI film, thereby ensuring the active lithium content in the battery cells and hopefully increasing the initial capacity of the battery.

[0004] However, although lithium-rich materials can provide abundant active lithium, existing research has revealed a key problem: most of the existing lithium-rich materials are solid-phase sintering products, which are characterized by high residual alkali content and poor particle size uniformity. These characteristics make the packing density of lithium-rich materials low, and they are prone to agglomeration and uneven distribution when preparing electrode slurry, and even poor gelation, which affects the uniformity and stability of the electrode slurry. The uniformity and stability of the electrode slurry are the cornerstones of electrochemical performance, and are of great significance for improving the performance of battery packs and extending battery life.

[0005] Therefore, how to improve the particle size uniformity of lithium-rich materials and improve their dispersibility is a difficult problem that technicians in this field have been trying to solve. Summary of the invention

[0006] The purpose of this application is to overcome the above-mentioned deficiencies of the prior art and to provide a composite lithium-rich material and a method for preparing the same, and a battery containing the composite lithium-rich material, so as to solve the technical problem that the particle size uniformity and dispersibility of the existing lithium-rich materials are not ideal, thereby making it difficult to further improve the performance of the battery, such as the energy density.

[0007] In order to achieve the above application objectives, in the first aspect, the present application provides a composite lithium-rich material. The composite lithium-rich material of the present application includes a first lithium-rich material and a second lithium-rich material, and also includes a connecting group, wherein the connecting group connects the first lithium-rich material and the second lithium-rich material.

[0008] The composite lithium-rich material of the embodiment of the present application connects the first lithium-rich material and the second lithium-rich material into a whole through a connecting group, so that the particles of the composite lithium-rich material have consistency, thereby effectively improving the packing density and dispersibility of the composite lithium-rich material, thereby improving the energy density and other performance of the battery. The connecting group can show a certain charge property, which can improve the dispersibility and dispersion stability of the composite lithium-rich material of the embodiment of the present application in the electrode slurry.

[0009] The second aspect of the present application provides a method for preparing the composite lithium-rich material of the present application. The method for preparing the composite lithium-rich material of the present application comprises the following steps:

[0010] A first lithium-rich material, a second lithium-rich material and a condensation agent are subjected to a first mixing treatment in a solvent, and a condensation reaction is performed to form a connecting group for connecting the first lithium-rich material and the second lithium-rich material between the first lithium-rich material and the second lithium-rich material, thereby obtaining a composite lithium-rich material.

[0011] In the method for preparing a composite lithium-rich material in an embodiment of the present application, the raw materials of a first lithium-rich material and a second lithium-rich material are directly subjected to a condensation reaction under the action of a condensation agent, and a connecting group for connecting the two is generated between the two, thereby allowing the first lithium-rich material and the second lithium-rich material to form a whole. On the basis of enabling the prepared composite lithium-rich material to more fully exert its lithium replenishment capacity, the composite lithium-rich material particles have good consistency and dispersibility, and can improve the uniform dispersibility and dispersion stability of the composite lithium-rich material in the electrode slurry.

[0012] The third aspect of the present application provides a battery. A positive electrode sheet of the battery of the present application, wherein the positive electrode active material layer of the positive electrode sheet comprises the composite lithium-rich material of the present application or the composite lithium-rich material prepared by the preparation method of the present application.

[0013] The positive electrode sheet of the battery of the present application contains the composite lithium-rich material of the embodiment of the present application, so the components of the positive electrode active material layer of the positive electrode sheet of the present application are evenly dispersed, the film layer quality is high, and the positive electrode sheet has high capacity and good cycle performance. Therefore, the battery of the present application has high first efficiency, energy density and good cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. 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 paying any creative work.

[0015] Figure 1 A schematic diagram of the structure of a composite lithium-rich material according to an embodiment of the present application;

[0016] Figure 2 It is the electron microscope image in Example A1 of the present application; wherein, Figure b is an enlarged view of Figure a;

[0017] The reference numerals in the specific implementation manner are as follows:

[0018] 1-composite lithium-rich material; 11-first lithium-rich material; 12-second lithium-rich material, 13-connecting group. DETAILED DESCRIPTION

[0019] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present 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 the present application and are not used to limit the present application.

[0020] In this application, the term "and / or" describes the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, 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 items 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, c can be single or multiple, respectively.

[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, and 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 only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" 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 other meanings.

[0024] The weight of the relevant components mentioned in the embodiment description of the present application can not only refer to the specific content of each component, but also represent the proportional relationship between the weights of the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the embodiment description of the present application, it is within the scope disclosed in the embodiment description of the present application. Specifically, the mass described in the embodiment description of the present application can be a mass unit known in the chemical industry such as μg, mg, g, kg, etc.

[0025] The terms "first" and "second" are used only for descriptive purposes to distinguish objects such as substances from each other, and should not be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. For example, without departing from the scope of the embodiments of the present application, the first XX may also be referred to as the second XX, and similarly, the second XX may also be referred to as the first XX. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

[0026] Since existing lithium-rich materials generally have high residual alkali content and poor particle size uniformity, the bulk density of lithium-rich materials is low and the dispersion is poor, which leads to agglomeration and uneven distribution when preparing electrode slurry, and even poor gelation, which affects the uniformity and stability of electrode slurry. The uniformity and stability of electrode slurry are the cornerstones of electrochemical performance and are of great significance to improving the efficiency of battery packs and extending battery life.

[0027] Furthermore, although lithium-rich materials can provide abundant active lithium, existing research has revealed a key problem: lithium-rich materials are often difficult to fully de-lithium during the battery charging process. This is mainly because lithium-rich materials have a specific lithium de-lithiation voltage range. When this range does not match the charging voltage of the battery, the lithium-rich material may not be able to fully de-lithium within the charging range of the battery, making it difficult to fully exert its lithium replenishment effect. This will not only affect the initial capacity of the battery, but may also have an adverse effect on the cycle performance of the battery. In order to improve the lithium replenishment effect, although there are reports of mixing different types of lithium-rich materials, as stated in the previous paragraph, lithium-rich materials have the disadvantages of poor particle size uniformity and dispersibility; at the same time, they are also affected by the defects of different types of lithium-rich materials, such as the large particle size and residual alkali problems of high-capacity and low-voltage platform lithium replenishers (LFO, LCO), such as the low-capacity and high-voltage platform lithium replenishers (lithium oxalate, lithium carbonate) slurry is prone to uneven distribution, and it also needs to be additionally compounded with catalysts and conductive carbon materials. These reasons result in different types of lithium-rich materials being unevenly dispersed in the electrode, which also leads to a low probability of different types of lithium-rich materials contacting each other, making it difficult for the synergistic or synergistic effect of lithium replenishment to occur.

[0028] In order to effectively improve the particle size uniformity and dispersibility of lithium-rich materials, or to further improve the synergistic effect or synergy of lithium replenishment between different types of lithium-rich materials, the embodiments of the present application propose the following scheme.

[0029] [Composite lithium-rich materials]

[0030] In a first aspect, the embodiments of the present application provide a composite lithium-rich material. In some embodiments, the composite lithium-rich material of the embodiments of the present application includes a first lithium-rich material, a second lithium-rich material, and a connecting group. The connecting group connects the first lithium-rich material and the second lithium-rich material.

[0031] In the composite lithium-rich material of the embodiment of the present application, the first lithium-rich material and the second lithium-rich material refer to materials rich in lithium ions, which can release active lithium ions during the battery charging process. The released lithium ions can form an SEI film with the electrolyte at the electrode interface, or migrate and embed into the negative electrode material. In addition, the first lithium-rich material and the second lithium-rich material can represent two types of particles of the same type of lithium-rich material, and the particles of the lithium-rich materials of the two types of particles are connected with the connecting group; the particles can be primary particles or secondary particles. The first lithium-rich material and the second lithium-rich material can also represent two types of lithium-rich materials of different material types, and the particles of the two types of lithium-rich materials are connected with the connecting group; of course, it can also include more than three types of lithium-rich materials, and the particles of two types of lithium-rich materials are connected with the connecting group.

[0032] The connecting group connects the first lithium-rich material and the second lithium-rich material, which means that one end of the connecting group is connected to the first lithium-rich material, and the other end is connected to the second lithium-rich material, and acts as a connecting bridge between the first lithium-rich material and the second lithium-rich material, connecting the first lithium-rich material and the second lithium-rich material into a whole. For example, in some embodiments, the structure of the composite lithium-rich material can be as follows Figure 1 As shown, the connecting group 13 contained in the composite lithium-rich material 1 is connected between the first lithium-rich material 11 and the second lithium-rich material 12, connecting the first lithium-rich material 11 and the second lithium-rich material 12 into a whole.

[0033] In this way, since the first lithium-rich material and the second lithium-rich material contained in the composite lithium-rich material of the embodiment of the present application are connected as a whole through a connecting group, the particle size of the composite lithium-rich material of the embodiment of the present application is consistent, thereby effectively improving the packing density and dispersibility of the composite lithium-rich material, improving its dispersibility and dispersion stability in the electrode slurry, effectively alleviating the phenomenon of agglomeration of the composite particle material in the electrode slurry, avoiding the phenomenon that the first lithium-rich material and the second lithium-rich material are each agglomerated in the electrode slurry and cannot achieve good uniformity, and at the same time making the capacity density of the electrode active material layer high, thereby improving the energy density and other performance of the battery. The connecting group can show a certain charge property, which can cooperate with the uniformity of the particle size of the composite lithium-rich material, and further improve the dispersibility of the composite lithium-rich material of the embodiment of the present application in the electrode slurry. The connecting group can also make the composite lithium-rich material of the embodiment of the present application have good structural stability, improve the lithium replenishment capacity of the composite lithium-rich material and the cycle performance of the battery.

[0034] Linking group:

[0035] In some embodiments, the molar fraction of the linker group in the composite lithium-rich material is 2% to 5%, optionally 2.5% to 3.5%. In the exemplary embodiment, it can be 2.0%, 2.3%, 2.5%, 2.8%, 3.0%, 3.2%, 3.5%, 3.8%, 4.0%, 4.3%, 4.5%, 4.8%, 5.0% and other typical but non-limiting contents or the range between any two content values. On the one hand, the content range of the linker group can effectively improve the connection strength between the first lithium-rich material and the second lithium-rich material, and improve the structural stability of the composite lithium-rich material; on the other hand, the content of the linker group can be used to adjust the total charge state and pH of the composite lithium-rich material and the compatibility with the solvent or other components in the electrode slurry, thereby improving the dispersibility and dispersion stability of the composite lithium-rich material in the electrode slurry.

[0036] In some embodiments, the above-mentioned connecting group may be an organic group, such as in the embodiments, it may include at least one group of an ester group, an ether group, an amide group, etc. These types of groups can effectively improve the connection strength to the first lithium-rich material and the second lithium-rich material, improve the structural stability of the composite lithium-rich material, and at the same time can adjust the total charge state and pH of the composite lithium-rich material and the compatibility with other components in the electrode slurry, thereby further improving the dispersibility and dispersion stability of the composite lithium-rich material in the electrode slurry. In addition, the connecting group may be different according to the type of the first lithium-rich material and the second lithium-rich material, such as the first lithium-rich material and the second lithium-rich material each contain different residual alkali, functional groups and components contained, and the type of the connecting group may also be different. That is, the type of the connecting group may be different according to the type of the first lithium-rich material and the second lithium-rich material.

[0037] The first lithium-rich material and the second lithium-rich material:

[0038] In the composite lithium-rich material of the embodiment of the present application, as described above, the first lithium-rich material and the second lithium-rich material can be different particles of the same type of lithium-rich material, or can be two different types of lithium-rich materials. Regardless of the situation of the first lithium-rich material and the second lithium-rich material, in some embodiments, the surface of the first lithium-rich material contains a first functional group, the surface of the second lithium-rich material contains a second functional group, and the first functional group and the second functional group are bonded to form the above-mentioned connecting group; or there is a molecular force between the first functional group and the second functional group; or there is a molecular force between the first functional group and the second functional group, and the two functional groups are bonded to form the above-mentioned connecting group. Among them, the second functional group can include a hydroxyl group, then the first functional group can include a group that is bonded and / or has a molecular force with the second functional group, such as at least one group including a carboxyl group, a hydroxyl group, an amino group, an aldehyde group, a ketone group, etc. At this time, the connecting group formed by the bond between the first functional group and the second functional group can be the above-mentioned connecting group, or further, there is a molecular force between the two functional groups. The linking group can effectively connect the first lithium-rich material and the second lithium-rich material, or / and the molecular force can enhance the molecular bonding force between the first lithium-rich material and the second lithium-rich material, improve the stability of the composite lithium-rich material structure, and improve the dispersibility and dispersion stability of the composite lithium-rich material in the electrode slurry. The molecular force refers to the force between the first lithium-rich material and the second lithium-rich material, such as van der Waals force, hydrogen bond, etc.

[0039] In some embodiments, the first lithium-rich material and the second lithium-rich material in the above embodiments are two different types of lithium-rich materials, such as the first lithium-rich material and the second lithium-rich material. There is a difference in the decomposition voltage (or delithiation voltage) interval between the two. For example, in the embodiment, the decomposition voltage of the first lithium-rich material is higher than the decomposition voltage of the second lithium-rich material. At this time, since the second lithium-rich material with a relatively low decomposition voltage contained in the composite lithium-rich material of the embodiment of the present application can be first delithiated in a relatively low voltage interval during the battery charging process, the first lithium-rich material can be delithiated in a relatively high voltage interval. In this way, the composite lithium-rich material of the embodiment of the present application is compounded by the high and low voltage platforms of the first lithium-rich material and the second lithium-rich material, so that the first lithium-rich material and the second lithium-rich material can achieve synergistic delithiation in different voltage intervals during the battery charging process, improve the balance of lithium replenishment, and can more fully exert the lithium replenishment capacity. Furthermore, the type of the second lithium-rich material can also be selected and controlled so that its decomposition product after delithiation in a relatively low voltage interval can act as a catalyst for the first lithium-rich material with a relatively high decomposition voltage, thereby reducing the delithiation potential of the first lithium-rich material and improving the lithium replenishment capacity of the first lithium-rich material.

[0040] In some embodiments, when the first lithium-rich material and the second lithium-rich material in the above embodiments are two different types of lithium-rich materials, the decomposition voltage of the first lithium-rich material is 0.4 to 1.7 V higher than the decomposition voltage of the second lithium-rich material, and optionally 0.4 to 0.8 V. In the exemplary embodiment, it can be a typical but non-limiting voltage difference such as 0.4 V, 0.5 V, 0.6 V, 0.7 V, 0.8 V, 0.9 V, 1 V, 1.2 V, 1.5 V, 1.7 V, or a range between any two voltage differences. The decomposition voltage difference range of the two lithium-rich materials can form a gradient lithium replenishment in the charging interval of the battery, further improve the balance of lithium replenishment of the composite lithium-rich material in the charging interval of the battery, and further exert the lithium replenishment capacity.

[0041] In some embodiments, the decomposition voltage of the first lithium-rich material is a lithium supplement of 4 to 4.7V, and the decomposition voltage of the lithium supplement is optionally 4.1 to 4.4V. In the exemplary embodiment, it can be a typical but non-limiting particle size of 4.0V, 4.1V, 4.2V, 4.3V, 4.4V, 4.5V, 4.6V, 4.7V, or a range between any two particle sizes. The lithium supplement of the decomposition voltage range can make the first lithium-rich material delithiate in a relatively high voltage range during the battery charging process, and fully delithiate under the catalytic effect of the product after the second lithium-rich material is delithiated; and it can also improve the synergistic effect with the second lithium-rich material, and improve the balance of the lithium supplement effect of the composite lithium-rich material during the battery charging process.

[0042] In some embodiments, when the first lithium-rich material and the second lithium-rich material in the above embodiments are two different types of lithium-rich materials, the first lithium-rich material includes a lithium-rich core and a coating layer coating the lithium-rich core, and the coating layer includes at least one of a carbon conductive agent, a single atom catalyst, and a metal organic framework; at least one of the carbon conductive agent, the single atom catalyst, and the metal organic framework contains the above-mentioned first functional group. At this time, the first functional group is bonded to the second functional group contained in the above-mentioned second lithium-rich material to form the above-mentioned connecting group or / and there is a molecular force between the two functional groups. In this embodiment, the first lithium-rich material is a core-shell structure, and the carbon conductive agent, the single atom catalyst, and the metal organic framework in the coating layer all have good electrical conductivity, which can effectively improve the electrical conductivity of the lithium-rich core; in addition, the single atom catalyst and the metal organic framework can catalyze the decomposition of the lithium-rich material contained in the lithium-rich core, reduce the decomposition voltage of the lithium-rich material, and thus improve the lithium replenishment capacity of the lithium-rich material. Secondly, at least one of the carbon conductive agent and the single atom catalyst in the coating layer contains a first functional group, and the first functional group can be the first functional group contained in the first lithium-rich material mentioned above. Then, at this time, the second functional group mentioned above is contained in the second lithium-rich material, and there is a molecular force between the bonding connecting group between the first functional group and the second functional group or / and between the two functional groups. In addition, the first functional group contained in the first lithium-rich material and the second functional group contained in the second lithium-rich material can be the types shown in the first functional group and the second functional group mentioned above.

[0043] In addition, in the exemplary embodiment, the carbon conductive agent may include at least one of carbon nanotubes, hollow carbon microspheres, and carbon quantum dots; the single atom catalyst may include at least one of CoO, NiO, and MnO. These types of carbon conductive agents and single atom catalysts not only have good electrical conductivity, but the single atom catalysts and metal organic frameworks also have good catalytic effects. Moreover, the surfaces of these types of carbon conductive agents, single atom catalysts, and metal organic frameworks are generally rich in the first functional groups described above, which can be bonded with the second functional groups contained in the second lithium-rich material, thereby improving the structural stability of the composite lithium-rich material and the uniformity of the particles.

[0044] In an embodiment, when the first lithium-rich material is the lithium-rich material of the above-mentioned core-shell structure, such as including a lithium-rich core and a coating layer coating the lithium-rich core, the decomposition voltage of the lithium-rich material contained in the lithium-rich core in the first lithium-rich material of the core-shell structure is higher than the decomposition voltage of the second lithium-rich material. At this time, the lithium-rich material contained in the lithium-rich core of the first lithium-rich material has a relatively higher decomposition voltage than the second lithium-rich material, and can be decomposed and delithiated in a relatively high decomposition voltage range. Moreover, the single-atom catalyst and metal-organic framework in the coating layer of the first lithium-rich material of the core-shell structure can catalyze the decomposition of the lithium-rich material contained in the lithium-rich core, reduce the decomposition voltage of the lithium-rich material, and thus improve the lithium replenishment capacity of the lithium-rich material.

[0045] In some embodiments, the first lithium-rich material in each of the above embodiments includes at least one lithium supplement agent of lithium oxalate, lithium carbonate, lithium squarate, and lithium oxide. These types of lithium supplement agents have a relatively high decomposition voltage range, such as a relatively higher decomposition voltage range than the second lithium-rich material, and can be delithiated in a relatively high voltage range, forming a high-low voltage platform with the second lithium-rich material to improve the balance of lithium supplementation. Moreover, these types of lithium supplement agents can make full use of the decomposition products of the second lithium-rich material after delithiation as a delithiation catalyst to improve its lithium supplement capacity. Among them, these types of lithium supplements can be conventional lithium supplement materials in the art, such as when the lithium supplement is a lithium oxalate supplement, a lithium carbonate supplement, a lithium squarate supplement, or a lithium oxide supplement, the lithium supplement is a lithium oxalate supplement, a lithium carbonate supplement, a lithium squarate supplement, or a lithium oxide supplement. The lithium supplement can be a first lithium-rich material such as the above-mentioned core-shell structure, that is, at least one lithium-rich nucleus including lithium oxalate, lithium carbonate, lithium squarate, and lithium oxide, and the coating layer covering the lithium-rich nucleus contains components such as a catalyst and a conductive agent. Among them, the catalyst can be loaded on the conductive agent. The conductive agent can be, but is not limited to, a carbon nanotube, and the conductive agent generally contains a functional group, such as the first functional group above. At this time, when the lithium supplement is a lithium oxalate supplement, a lithium carbonate supplement, a lithium squarate supplement, or a lithium oxide supplement, the above connecting group or one end of the chemical bond formed by bonding the above first functional group and the second functional group can be, but is not limited to, connected to the conductive agent, such as a carbon nanotube.

[0046] In some embodiments, the particle size Dv50 of the first lithium-rich material in the above embodiments can be 1-5 μm, optionally 2-3 μm, and in the exemplary embodiment, it can be 1 μm, 1.5 μm, 2 μm, 12.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, etc., which are typical but non-limiting particle sizes, or a range between any two particle size values. The particle size range of the first lithium-rich material can be used together with the second lithium-rich material to adjust the particle size range of the composite lithium-rich material, thereby improving the uniformity and stability of the dispersion of the composite lithium-rich material in the electrode slurry.

[0047] In some embodiments, the particle size Dv50 of the second lithium-rich material in the above embodiments can be 20-30 μm, optionally 20-25 μm, and in the exemplary embodiment, it can be 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, etc., which are typical but non-limiting particle sizes, or a range between any two particle size values. The particle size range of the second lithium-rich material can be adjusted together with the first lithium-rich material to adjust the particle size range of the composite lithium-rich material, thereby improving the uniformity and stability of the dispersion of the composite lithium-rich material in the electrode slurry.

[0048] In some embodiments, the second lithium-rich material has a decomposition voltage of 3.0 to 4.0 V. Optionally, the decomposition voltage of the lithium-rich material is 3.3 to 3.5 V. In the exemplary embodiment, the decomposition voltage may be 3 V, 3.1 V, 3.2 V, 3.3 V, 3.4 V, 3.5 V, 3.6 V, 3.7 V, 3.8 V, 3.9 V, 4.0 V, or a range between any two particle diameter values. The lithium-rich material in the decomposition voltage range can be delithiated in a relatively low voltage range during the battery charging process, and together with the first lithium-rich material, a lithium-replenishing gradient is formed during the battery charging process, thereby improving the synergistic effect with the first lithium-rich material and improving the balance of the lithium-replenishing effect of the composite lithium-rich material during the battery charging process.

[0049] In some embodiments, the second lithium-rich material in the above embodiments includes at least one lithium supplement selected from lithium iron oxide (LFO), lithium cobalt oxide (LCO), and lithium manganese oxide (LMO). These types of lithium supplements have a relatively low decomposition voltage interval, such as a relatively low decomposition voltage interval compared to the above first lithium-rich materials such as lithium oxalate and lithium carbonate, and can be fully delithiated in a relatively low voltage interval during battery charging, and the product after delithiation can be used as a catalyst for the first lithium-rich material, reducing the decomposition voltage of the first lithium-rich material and improving the lithium supplement capacity of the first lithium-rich material. Among them, these types of lithium supplements can be lithium supplements formed by condensation reaction of conventional lithium supplements in the art with the first lithium-rich material raw material through the following preparation method, such as when the lithium supplement is a lithium iron oxide lithium supplement or a lithium titanate lithium supplement, the lithium iron oxide lithium supplement and the lithium titanate lithium supplement are generally formed by condensation reaction of lithium iron oxide lithium supplement and lithium titanate lithium supplement raw materials with the first lithium-rich material raw material through the following preparation method. Moreover, raw materials such as lithium ferrite lithium supplement and lithium titanate lithium supplement generally contain residual lithium or other functional groups, so that these lithium supplements have the second functional group mentioned above. Moreover, after the second functional group contained in the second lithium-rich material is bonded with the first functional group mentioned above, the residual alkali content of the second functional group can be reduced. For example, after testing, the residual alkali content of the second lithium-rich material in the composite lithium-rich material can be 3% to 8%, thereby improving the dispersion stability of the composite lithium-rich material in the electrode slurry and reducing the viscosity of the electrode slurry.

[0050] Based on the above embodiments, the particle size of the composite lithium-rich material in the above embodiments can be adjusted by adjusting the particle size and content of the first lithium-rich material and the second lithium-rich material. For example, in some embodiments, the average particle size of the composite lithium-rich material in the above embodiments is 5 to 10 μm, optionally 5 to 8 μm. In the exemplary embodiment, it can be a typical but non-limiting particle size such as 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, or a range between any two particle size values. This particle size range of the composite lithium-rich material has relatively high particle size uniformity and compaction density, and can further improve the uniformity and stability of the dispersion of the composite lithium-rich material in the electrode slurry.

[0051] In some embodiments, the mass ratio of the first lithium-rich material to the second lithium-rich material may be (1-10):1, optionally (5-10):1, and in exemplary embodiments, may be 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, or other typical but non-limiting mass ratios or ranges between any two mass ratios. The mass ratio range of the two lithium-rich materials can adjust the gradient lithium replenishment of the composite lithium-rich material in the charging interval of the battery, further improve the balance of lithium replenishment of the composite lithium-rich material in the charging interval of the battery, and further exert the lithium replenishment capacity.

[0052] In some embodiments, the average density of the composite lithium-rich material in the above embodiments is 2-3 mg / cm 3 In the example, it can be 2mg / cm 3 , 2.2mg / cm 3 , 2.5mg / cm 3 , 2.8mg / cm 3 、3mg / cm 3 Typical but non-limiting average densities or ranges between any two average density values. The average density range of the composite lithium-rich material can further improve the uniformity and stability of the dispersion of the composite lithium-rich material in the electrode slurry.

[0053] In some embodiments, the pH of the composite lithium-rich material in the above embodiments is 9 to 11, optionally 9.5 to 10. In the exemplary embodiment, it can be a typical but non-restrictive pH such as 9, 9.5, 10, 11, or a range between any two pH values. The pH of the composite lithium-rich material can also further improve the uniformity and stability of the dispersion of the composite lithium-rich material in the electrode slurry. Among them, the pH test method of the composite lithium-rich material can use a water extraction method to test the pH of the material. The solid powder material of the quantitative composite lithium-rich material and 50 mL of ultrapure water are added to a conical flask, and the mixture is stirred and shaken at a fixed stirring rate for 5 minutes to form a stable suspension. The pH probe is immersed 3 cm below the liquid surface, and the test result is waited for to stabilize, and the pH value of the material is tested.

[0054] In a further embodiment, the composite lithium-rich material in each of the above embodiments includes a dispersant, which is at least bound to the surface of the composite lithium-rich material. The presence of the dispersant can assist the connecting group to further improve the dispersion uniformity and dispersion stability of the composite lithium-rich material in the electrode slurry of the present application embodiment. In some embodiments, the mass percentage of the dispersant in the composite lithium-rich material is 0.1% to 0.5%, optionally 0.2% to 0.3%. In the exemplary embodiment, it can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5% and other typical but non-limiting contents or a range between any two content values. This content range of the dispersant can further improve the dispersibility of the composite lithium-rich material in the electrode slurry, thereby further improving the dispersion uniformity and dispersion stability of the electrode slurry.

[0055] In an embodiment, the dispersant may include at least one of a phosphate dispersant, a titanate dispersant, and a stearic acid glyceryl dispersant. In an exemplary embodiment, when the dispersant includes a phosphate dispersant, the phosphate dispersant may include at least one of triphenyl phenol polyoxyethylene ether phosphate (600 phosphate), styrene polyether phosphate (TSP phosphate), and lauryl alcohol ether phosphate (AEO-9 phosphate). These types of dispersants are rich in hydrophilic groups and hydrophobic groups, and their hydrophobic groups can be combined with composite lithium supplement materials, such as being combined with connecting groups contained in composite lithium-rich materials or lithium-rich materials contained therein; their hydrophilic groups can act with solvents, thereby improving the dispersibility of composite lithium-rich materials in electrode slurries, thereby improving the dispersion uniformity and stability of composite lithium-rich materials in electrode slurries. For example, when the dispersant includes these phosphate dispersants, the ester groups contained therein can at least combine with the connecting groups contained in the composite lithium-rich material; the phosphate groups contained therein can be effectively dispersed into the solvent, and can also produce charge repulsion with the rich negatively charged groups on the surface of the first lithium-rich material and the second lithium-rich material, thereby reducing the agglomeration phenomenon between the composite lithium-rich material particles, thereby improving the dispersibility and dispersion stability of the composite lithium-rich material in the electrode slurry.

[0056] In a second aspect, the present invention also provides a method for preparing the composite lithium-rich material described above. The method for preparing the composite lithium-rich material described in the present invention comprises the following steps:

[0057] S10: performing a first mixing treatment in a solvent including a first lithium-rich material, a second lithium-rich material and a condensation agent, and performing a condensation reaction to form a connecting group for connecting the first lithium-rich material and the second lithium-rich material between the first lithium-rich material and the second lithium-rich material, thereby obtaining a composite lithium-rich material.

[0058] In the preparation method of the composite lithium-rich material in the embodiment of the present application, the raw materials of the first lithium-rich material and the second lithium-rich material refer to the raw materials before being reacted with the condensing agent, and are also the raw materials of the first lithium-rich material and the second lithium-rich material contained in the composite lithium-rich material above.

[0059] In some embodiments, the raw materials of the first lithium-rich material and the second lithium-rich material can be the current conventional first lithium-rich material raw material with high decomposition voltage and the second lithium-rich material raw material with relatively low decomposition voltage. In the exemplary embodiment, the raw material of the first lithium-rich material can be at least one lithium-supplementing material of the conventional lithium oxalate, lithium carbonate, lithium quartz, and lithium oxide mentioned above. When the raw material of the first lithium-rich material is a lithium-supplementing material such as lithium oxalate and lithium carbonate, the lithium-supplementing material can be a lithium-supplementing material of the core-shell structure mentioned above, such as a coating layer including a lithium-rich core body and a coating layer covering the lithium-rich core body, and the lithium-rich material of the lithium-rich core body can be lithium oxalate and lithium carbonate, and the coating layer includes at least one of a carbon conductive agent and a single-atom catalyst, and at least one of the carbon conductive agent and the single-atom catalyst contains the first functional group mentioned above, such as rich in carboxyl, amino, hydroxyl, aldehyde, ketone and other groups. The conductive agent can be but is not limited to carbon nanotubes, the catalyst is loaded on the carbon nanotubes, and the carbon nanotubes are wound around lithium oxalate or lithium carbonate, and the carbon nanotubes are rich in carboxyl groups. In the exemplary embodiment, the raw material of the second lithium-rich material can be at least one lithium-supplementing material selected from the group consisting of lithium-rich ferrite (LFO), lithium-rich cobalt oxide (LCO), and lithium-rich manganese oxide (LMO). When the raw material of the second lithium-rich material is a lithium-supplementing material such as lithium ferrite (LFO) and lithium titanate (LCO), the lithium-supplementing material generally contains residual alkali, which is rich in -OH groups. In this case, the second functional group contained in the second lithium-rich material can include -OH.

[0060] Therefore, during the condensation reaction, the condensing agent can promote the condensation reaction of the charged groups contained in the raw materials of the first lithium-rich material and the second lithium-rich material to generate the connecting group contained in the composite lithium-rich material of the above-mentioned application embodiment, and enable one end of the connecting group to be effectively connected to the first lithium-rich material, and the other end to be effectively connected to the second lithium-rich material, so that the first lithium-rich material and the second lithium-rich material form a whole under the connection action of the generated connecting group. As in the embodiment, when the raw material of the first lithium-rich material is a lithium supplement material such as lithium oxalate and lithium carbonate, and the raw material of the second lithium-rich material is a lithium supplement material such as lithium ferrite (LFO) and lithium cobaltate (LCO), the carboxyl group contained in the lithium supplement material such as lithium oxalate and lithium carbonate and the hydroxyl group contained in the lithium supplement material such as lithium ferrite (LFO) and lithium cobaltate (LCO) undergo an esterification reaction under the action of a condensation agent to generate an ester group, that is, one end of the ester group is connected to a lithium supplement such as lithium oxalate and lithium carbonate, and the other end is connected to a lithium supplement such as lithium ferrite (LFO) and lithium cobaltate (LCO) to form a whole, thereby generating a composite lithium-rich material containing lithium supplements such as lithium oxalate and lithium carbonate and lithium supplements such as lithium ferrite (LFO) and lithium cobaltate (LCO).

[0061] In this way, the composite lithium-rich material preparation method of the embodiment of the present application directly condenses the raw materials of the first lithium-rich material and the second lithium-rich material under the action of a condensing agent, and generates a connecting group for connecting the two, so that the first lithium-rich material and the second lithium-rich material form a whole, which can make the prepared composite lithium-rich material more fully play the lithium supplement capacity, and the composite lithium-rich material has structural stability and particle consistency. In addition, the composite lithium-rich material has good dispersibility, which can improve the uniform dispersibility and dispersion stability of the composite lithium-rich material in the electrode slurry.

[0062] In an embodiment, after the first lithium-rich material and the second lithium-rich material undergo a condensation reaction, molecular forces may further exist between the first functional group and the second functional group that have not completely undergone the condensation reaction, or between the first lithium-rich material and the second lithium-rich material that may contain other functional groups. This molecular force can also make the generated composite lithium-rich material structurally stable, the particles have consistency, and improve the dispersibility of the composite lithium-rich material.

[0063] In the embodiment, when the decomposition voltage of the first lithium-rich material is higher than the decomposition voltage of the second lithium-rich material, the prepared composite lithium-rich material can also replenish lithium in a balanced manner within the charging range of the battery as described above, and can more fully exert the lithium replenishment capacity.

[0064] In some embodiments, the raw materials of the first lithium-rich material, the second lithium-rich material and the condensation agent can be mixed in a mass ratio of (1-10):1:(0.02-0.11). Mixing the three within this range can control the mass ratio of the first lithium-rich material and the second lithium-rich material contained in the generated composite lithium-rich material, thereby improving the synergistic effect of the two in replenishing lithium in the battery charging range, improving the lithium replenishing capacity of the composite lithium-rich material, and also increasing the content of the generated connecting group, and increasing the connection strength of the connecting group to the two lithium-rich materials, thereby improving the structural stability of the composite material, and can also improve the uniform dispersion and dispersion stability of the composite lithium-rich material in the electrode slurry.

[0065] In an embodiment, the condensing agent may include at least one of hydroxybenzotriazole (HOBt), dicyclohexylcarbodiimide (DCC), 4-dimethylaminopyridine (DMAP), etc. These types of condensing agents can effectively cause the charge groups contained in the raw materials of the first lithium-rich material and the second lithium-rich material to undergo condensation reactions, thereby generating connecting groups and improving the structural stability of the generated composite material.

[0066] In the embodiment, the solvent in step S10 and the raw materials constitute a reaction system for the condensation reaction. In some embodiments, the solvent includes a medium and weak polar organic solvent, such as at least one of N-methylpyrrolidone (NMP), isopropanol, ethyl acetate, xylene, etc. These medium and weak polar organic solvents can effectively disperse the raw materials and can effectively improve the stability of the connecting group connected between the first lithium-rich material and the second lithium-rich material, thereby improving the structural stability of the generated composite lithium-rich material.

[0067] In some embodiments, after the condensation reaction in step S10 is completed, the following steps are further included:

[0068] S20: adding a dispersant to the mixed solution to perform a second mixing process, and then removing the solvent.

[0069] A dispersant is added to the mixed solution after the condensation reaction so that the dispersant can be bound to the surface of the composite lithium-rich material, such as at least bound to the surface of at least one of the first lithium-rich material and the second lithium-rich material, thereby achieving surface modification of the composite lithium-rich material, improving the dispersibility of the composite lithium-rich material in the mixed solution or in the subsequent preparation of the electrode slurry, and reducing its agglomeration phenomenon.

[0070] In an embodiment, the dispersant can be added in a ratio of (1-5) to the mass ratio of the first lithium-rich material to the dispersant: 1000. Optionally, the mass ratio of the first lithium-rich material to the dispersant is (2-3) to 1000. In a demonstration example, it can be a typical but non-limiting mass ratio such as 1:1000, 2:1000, 3:1000, 4:1000, 5:1000, or a range between any two mass ratios. Controlling the amount of the dispersant added within a range can further improve the surface modification effect of the composite lithium-rich material and further improve its dispersibility.

[0071] In the embodiment, the method for removing the solvent in step S20 may include vacuum drying and the like. This method can effectively remove the solvent and ensure the stability of each component, such as not destroying the connecting group and the dispersant, thereby ensuring the stability of the composite lithium-rich material structure and allowing each component to volatilize its own function.

[0072] In the embodiment, the composite lithium-rich material obtained after the solvent is removed may be further cleaned to remove impurities such as residual solvent or reactant raw materials.

[0073] In addition, the first mixing treatment in step S10 and the second mixing treatment in step S20 can independently include stirring, ultrasonic waves, ball milling or other conventional mixing methods, as long as the components can be mixed evenly, they are within the scope disclosed in the specification of this application. It should be noted that the ball milling can be controlled at 200r / min-500r / min; for materials such as Li5FeO4 (lithium-rich lithium iron oxide, LFO) and Li6CoO4 (lithium-rich lithium cobalt oxide, LCO) that are easy to gel, adding a ball mill with an appropriate speed can control the overall Dv50 of the composite lithium-rich material to a suitable particle size, and its effect is obviously different from mixing, preventing the simple mixing method from causing the particle size distribution of the composite lithium-rich material to have peaks with the two materials.

[0074] In the third aspect, the embodiment of the present application also provides a battery. The battery of the embodiment of the present application includes necessary components such as a positive electrode sheet, a negative electrode sheet, a diaphragm or a solid electrolyte, and of course other necessary or auxiliary components. Among them, the diaphragm or solid electrolyte is arranged between the positive electrode sheet and the negative electrode sheet. When the battery of the embodiment of the present application is an ion battery, it contains a diaphragm; when the battery of the embodiment of the present application is a solid-state battery, it contains a solid electrolyte.

[0075] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer combined on the surface of the positive electrode current collector. In the embodiment, the positive electrode current collector of the positive electrode can be but not limited to any one of copper foil and aluminum foil.

[0076] The positive electrode active material layer of the positive electrode includes components such as positive electrode active material, lithium supplement material, binder and conductive agent.

[0077] At least one of the positive electrode active material and the lithium supplement material in the positive electrode active material layer includes the composite lithium-rich material of the above-mentioned embodiment of the application.

[0078] Since the positive electrode sheet of the battery of the embodiment of the present application contains the composite lithium-rich material of the embodiment of the present application, the positive electrode active material and lithium supplement material contained in the positive electrode sheet of the embodiment of the present application are evenly dispersed in the positive electrode active material layer, the film layer quality is high, and the positive electrode sheet has a high capacity and good cycle performance. Thereby giving the battery of the embodiment of the present application a high energy density and good cycle performance. When the lithium supplement material is the composite lithium-rich material of the embodiment of the present application, the battery of the embodiment of the present application can also be given a high first effect.

[0079] In the embodiment, the lithium supplement material can control the mass percentage of the composite lithium-rich material in the positive electrode active material layer to be 0.1% to 6%. When the lithium supplement material includes the composite lithium-rich material of the above application embodiment, the mass percentage of the composite lithium-rich material in the positive electrode active material layer can be 0.1% to 6%.

[0080] The positive electrode active material in the positive electrode active material layer may include the composite lithium-rich material of the above-mentioned embodiment of the present application, and of course may also include other positive electrode materials in the field of lithium-ion batteries. In the exemplary embodiment, other positive electrode active materials 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 vanadium phosphate fluoride, lithium titanate, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

[0081] In the embodiment, when at least one of the positive electrode active material and the lithium supplement material includes the composite lithium-rich material of the above-mentioned embodiment of the application, the composite lithium-rich material can be a composite lithium-rich material with a dispersant bound to the surface, and of course, it can also be a composite lithium-rich material without a dispersant bound to the surface. Relatively preferably, the composite lithium-rich material is a composite lithium-rich material with a dispersant bound to the surface to improve the uniformity of the dispersion of the composite lithium-rich material in the positive electrode active material layer.

[0082] In an embodiment, the positive electrode active material layer contains a dispersant, which can be added in the process of preparing the positive electrode slurry, so that the components in the positive electrode slurry including the composite lithium-rich material can be evenly dispersed in the positive electrode slurry, thereby improving the dispersion uniformity of the positive electrode slurry solid content and the stability of the slurry, and improving the film quality of the positive electrode active material layer.

[0083] In the embodiment, the content of the binder in the positive electrode active material layer can be 1wt%-2wt%. In a specific embodiment, the content of the binder can be 1wt%, 1.5wt%, 2wt% 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.

[0084] In the embodiment, the content of the conductive agent in the positive electrode active material layer can be 0.5wt%-1.5wt%. In a specific embodiment, the content of the binder can be 0.5wt%, 1wt%, 1.5wt% 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.

[0085] In the embodiment, the positive electrode preparation process can be: positive electrode active material, lithium supplement material, conductive agent and binder are mixed to obtain positive electrode slurry, the positive electrode slurry is coated on the current collector, and the positive electrode is prepared through drying, rolling, die cutting and other steps.

[0086] The negative electrode sheet contained in the battery of the embodiment of the present application may be a conventional negative electrode sheet. When the negative electrode sheet is a metal lithium foil, the lithium battery of the embodiment of the present application may be a lithium metal battery.

[0087] 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.

[0088] The following is a description of the composite lithium-rich material and its preparation method and battery according to the embodiments of the present application through a number of specific embodiments.

[0089] 1. Composite lithium-rich material and preparation method thereof:

[0090] Embodiment A1:

[0091] This embodiment provides a composite lithium-rich material and a preparation method thereof. The composite lithium-rich material includes lithium-rich lithium ferrite (LFO) lithium-supplementing material particles and lithium carbonate lithium-supplementing material particles, and an ester bond is formed between the LFO lithium-supplementing material particles and the lithium carbonate lithium-supplementing material particles, and the ester bond connects the LFO lithium-supplementing material particles and the lithium carbonate lithium-supplementing material particles. The specific characterization data of the composite lithium-rich material are shown in Table 1 below.

[0092] The preparation method of the composite lithium-rich material of this embodiment comprises the following steps:

[0093] S1: LFO and lithium carbonate lithium supplement material (the lithium carbonate lithium supplement material includes 70% main lithium carbonate, 10% catalyst, and 20% carboxyl carbon nanotube conductive agent) are ball-milled at 250±50r / min for 2h in a ratio of 1:2 to mix evenly; 99% of the composite lithium supplement material is added with 1% hydroxybenzotriazole (HOBt) esterification condensation agent (the mass ratio of the composite lithium supplement material of LFO and lithium carbonate lithium supplement material to HOBt is 99:1) and an appropriate amount of NMP solvent, and stirred evenly for esterification reaction (the residual alkali on the surface of LFO is rich in hydroxyl groups and the carboxyl groups of carbon nanotubes are tightly esterified and condensed);

[0094] S2: Add 0.2% by mass of phosphate dispersant (600 phosphate ester) to 99.8% by mass of composite lithium supplement material, stir evenly, and vacuum dry to remove NMP solvent to obtain composite lithium-rich material. 2% composite lithium-rich material is added to 98% positive electrode slurry to form final slurry.

[0095] Embodiment A2 to Embodiment A7:

[0096] Embodiments A2 to A7 provide a composite lithium-rich material and a preparation method thereof. The composite lithium-rich materials in Embodiments A2 to A7 are different from the composite lithium-rich material in Embodiment A1 as shown in Table 1 below, and the others are the same.

[0097] The preparation methods of the composite lithium-rich materials in Examples A2 to A7 are prepared by referring to the preparation method of the composite lithium-rich materials in Example A1. Compared with the preparation method of the composite lithium-rich materials in Example A1, the difference is that the composite lithium-rich materials in Examples A2 to A7 in Table 1 are prepared by controlling the deposition conditions of the corresponding steps. Among them, the dispersant of Example A6 is added in the homogenization stage, and the phosphate dispersant contains a hydrophilic group and a hydrophobic group, and its hydrophobic group can be combined with the composite lithium-supplementing material, and its hydrophilic group can react with the solvent. The composite lithium-supplementing material is added to the 98% mass fraction of the positive electrode slurry at a mass fraction of 2%, and then a 0.2% mass fraction of the phosphate dispersant (600 phosphate ester) is added to the aforementioned slurry, and the slurry is homogenized to form the final slurry.

[0098] Comparative Example A1:

[0099] This comparative example provides a lithium-rich material, which is lithium-rich lithium ferrite (LFO) lithium-supplementing material particles, which is the LFO lithium-supplementing material in step S1 of the composite lithium-rich material preparation method in Example A1.

[0100] Comparative Example A2:

[0101] This comparative example provides a lithium-rich material, which is lithium carbonate lithium-supplementing material particles, which is the lithium carbonate lithium-supplementing material in step S1 of the composite lithium-rich material preparation method in Example A1.

[0102] Comparative Example A3:

[0103] This comparative example provides a lithium-rich material, wherein the composite lithium-rich material includes lithium-rich lithium iron oxide (LFO) lithium-supplementing material particles and lithium carbonate lithium-supplementing material particles, and the ratio thereof is the same as that in Example A1. The difference from Example A1 is that the lithium-rich lithium iron oxide (LFO) lithium-supplementing material particles and the lithium carbonate lithium-supplementing material particles are not subjected to special esterification reaction treatment, that is, the two are separated independently from each other.

[0104] Comparative Example A4:

[0105] This comparative example is a blank comparative example, and no lithium supplement material is added.

[0106] Related performance testing of composite lithium-rich materials:

[0107] Particle size detection method for composite lithium-rich materials: Use a laser particle size analyzer to test the particle size distribution of the material powder. Dv50 is the median of the particle size distribution. The diameter distance indicates the distribution width of the particles. The larger the value, the wider the distribution.

[0108] In addition, the lithium-rich materials provided in the above embodiments were subjected to scanning electron microscopy (SEM), wherein the SEM photo of the lithium-rich material in Embodiment A1 is as follows: Figure 2 As shown, Figure b is a local enlarged view of Figure a.

[0109] Table 1

[0110]

[0111]

[0112] 2. Lithium-ion battery example:

[0113] The present embodiments B1 to B7 and comparative examples B1 to B4 provide a lithium ion battery respectively. Each lithium ion battery is assembled into a lithium ion battery according to the following method:

[0114] 1) Positive electrode:

[0115] The composite lithium-rich materials provided in Examples A1 to A7 and Comparative Examples A1 to A4 are used as positive electrode lithium supplement additives for lithium ion battery Examples B1 to B7 and Comparative Examples B1 to B4, respectively. Under the same conditions, lithium iron phosphate (LFP), composite lithium-rich material: Su-P conductive agent: PVDF binder are mixed in an appropriate amount of NMP in a mass ratio of 96:2:1:1, and the mixing method is ball milling, and the ball milling time is 60 minutes; the speed is set to 30Hz to prepare a positive electrode slurry; after homogenization-coating-drying-cutting operations, a positive electrode sheet is prepared, and the positive electrode sheet is baked in a vacuum oven at 100°C to remove trace water. Specifically, the positive electrode sheet in the lithium ion battery in Example B1 contains the composite lithium-rich material in Example A1, the positive electrode sheet in the lithium ion battery in Example B2 contains the composite lithium-rich material in Example A2, and so on, the positive electrode sheet in the lithium ion battery in Comparative Example B4 contains the composite lithium-rich material in Comparative Example A4.

[0116] 2) Negative electrode sheet: The negative electrode active material graphite, conductive agent Super P, thickener carboxymethyl cellulose (CMC), and binder styrene butadiene rubber (SBR) are mixed evenly in deionized water to form a negative electrode slurry, wherein the mass ratio of graphite: Super P: CMC: SBR is 95:2:0.5:2.5. The negative electrode slurry is coated on the current collector copper foil, and after drying-rolling-secondary drying process, the negative electrode sheet is made.

[0117] 3) Diaphragm: Use polyethylene (PE) diaphragm.

[0118] 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.

[0119] 5) Assembly of secondary batteries:

[0120] The positive electrode sheet, negative electrode sheet, electrolyte and separator are assembled into a lithium-ion soft-pack battery according to the lithium-ion battery assembly requirements.

[0121] Related performance testing of lithium-ion batteries:

[0122] The positive electrode slurries and lithium-ion batteries of the embodiments and comparative examples assembled in Section 5) were subjected to relevant performance tests as shown in Table 2 below, and the measured results are shown in Table 2 below.

[0123] Among them, the relevant performance test methods in Table 2 are as follows:

[0124] Viscosity detection method of positive electrode slurry: The viscosity of the slurry is measured by testing the slurry using a rotational viscometer.

[0125] The particle size test method of positive electrode slurry: Use the scraper fineness to test the slurry particle size. During the operation, drop the slurry into the deepest part of the groove, hold the scraper with both hands, horizontally and vertically at the upper end of the polished plate, so that the scraper is in vertical contact with the surface of the polished plate; within 3 seconds, pull the scraper from the deep part of the groove to the shallow part, so that the slurry fills the groove and no excess material is left on the plate. After the scraper is pulled, immediately (no more than 5 seconds) make the line of sight at an angle of 15° to 30° with the groove plane, and observe the scale line where the particles in the groove are evenly exposed (accurate to the minimum graduation value).

[0126] Testing method for internal resistance of lithium-ion battery cells: The AC impedance method measures the impedance and phase angle of the battery cell by applying a small-amplitude AC signal to obtain the internal resistance value.

[0127] The test method for the initial efficiency of lithium-ion battery cells is: the percentage of battery discharge capacity and charge capacity during the battery's first charge and discharge process.

[0128] The test method for the cycle performance of lithium-ion battery cells is: the percentage of the charging capacity after 1000 cycles of the battery and the charging capacity in the first cycle.

[0129] Table 2

[0130]

[0131]

[0132] Combined with Table 1 above, it can be seen from the test results in Table 2 that the lithium-rich materials in Comparative Examples A1 to Comparative Examples A4 are normal high-capacity, low-voltage positive electrode lithium supplement LFO, low-capacity, high-voltage positive electrode lithium supplement lithium carbonate, mixed lithium supplement materials, and no lithium supplement agent added (Comparative Example A4 is a conventional LFP material without a lithium supplement agent). Among them, Comparative Examples A1 and A2 are LFO and lithium carbonate lithium supplement materials, respectively. Although LFO has a larger fineness, it is a single material with relatively good dispersibility and little effect on the viscosity of the slurry; while the lithium carbonate lithium supplement material also contains a conductive agent and a catalyst, and the combination of multi-phase materials leads to poor dispersion effect; the internal resistance of the battery cell is affected by the material distribution and the integrity of the conductive network. The higher the conductivity and the more uniform the dispersion, the smaller the internal resistance; the advantages of high lithium supplement capacity and low lithium supplement voltage make LFO more obvious in improving the first effect and capacity retention rate than lithium carbonate.

[0133] The difference between Comparative Example A3 and Comparative Examples A1 and A2 also lies in the different diameter distances of the materials. For example, in Comparative Example A3, the mixed lithium supplement material is only physically mixed, and there is a difference in particle size between the two materials, and the diameter distance is relatively large; since no condensing agent is added, the fineness in the slurry reaches 15 μm, which is probably the effect of large LFO particles; without the addition of a dispersant, the lithium supplement material is unevenly distributed, the initial viscosity of the slurry is relatively high, and the particles settle after 48 hours of storage, the viscosity increases, and the viscosity difference increases.

[0134] Comparative Example A4 is a blank control group, in which no lithium supplement is added. Comparative Example B4 in Table 2 is the battery performance data of conventional LFP materials.

[0135] It can be seen from Table 2 that based on the solutions of Comparative Examples A1 to A4 shown in Table 1, the battery cell performances corresponding to Comparative Examples A1 to A4 are obviously inferior to the battery cell performances of Examples A1 to A7.

[0136] Embodiments A1 to A3 use ester-bonded lithium supplement materials, and dispersants are added inside the materials. The difference lies in the different proportions of the compound materials. The proportion of the compound materials directly affects the bonding contact of the materials and the comprehensive particle size of the materials. The appropriate proportion can reduce the material diameter width, reduce the slurry viscosity, and then reduce the internal resistance of the battery cell, so that the battery cell has better performance, such as the relevant performance of the battery cells of Embodiments B1 to B3 in Table 2.

[0137] The difference between Example A4 and Example A1 is that a DCC condensing agent is used to form an amide group bond between the two lithium-supplementing materials by means of the amino groups on the carbon nanotubes, which can also effectively improve the performance of the battery cell, such as the battery cell performance of Example B4 in Table 2. The difference between Example A5 and Example A1 is that no dispersant is added. The dispersant can affect the diameter width and fineness of the composite lithium-supplementing material in the slurry to a certain extent. However, since an ester group connecting the lithium carbonate and LFO is formed between the two, although the electrode slurry and the corresponding battery cell performance in Example A5 are respectively reduced relative to Example A1, they are still significantly better than Comparative Examples A1 to Comparative Examples A4. The dispersant of Example A6 is added in the homogenization stage. The phosphate dispersant contains a hydrophilic group and a hydrophobic group. Its hydrophobic group can combine with the composite lithium-supplementing material, and its hydrophilic group can react with the solvent, thereby improving the dispersion uniformity and stability of the composite lithium-rich material in the electrode slurry. The advantages of Example A6 over Example A1 are better dispersion effect, material viscosity closer to LFP, and the corresponding battery cell is also improved relative to Example B1; the disadvantage is that the amount of dispersant added needs to be increased according to the content of the main material.

[0138] At the same time, after mixing using a certain ball milling method, Example A1 can control the overall Dv50 of the lithium-rich material to drop from 20-30um to 5-10um, which is different from simple mixing methods and avoids the appearance of two peaks of (3-5um) and (20-30um) in the particle size distribution.

[0139] In summary, by configuring the composite lithium supplement material with particle size, density, state of charge, pH value, etc. close to the positive electrode material in appropriate proportion, the slurry fineness can be reduced; by using the condensation agent and dispersant together, different lithium supplement additives can be closely combined and evenly dispersed during homogenization. At the same time, the combination of high and low voltage platform lithium supplement materials, on the one hand, makes the battery more fully and balanced in the charging range of lithium supplement, on the other hand, the decomposition products of low voltage and high capacity lithium supplement additives LFO and LCO can also catalyze the composite lithium supplement additive, so that the lithium supplement capacity can be more fully utilized.

[0140] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A composite lithium-rich material, characterized in that: The invention comprises a first lithium-rich material and a second lithium-rich material, and also comprises a connecting group, wherein the connecting group connects the first lithium-rich material and the second lithium-rich material.

2. The composite lithium-rich material according to claim 1, characterized in that: The connecting group includes at least one of an ester group, an ether group, and an amide group.

3. The composite lithium-rich material according to claim 1 or 2, characterized in that: The surface of the first lithium-rich material contains a first functional group, the surface of the second lithium-rich material contains a second functional group, and the first functional group and the second functional group are bonded to form the connecting group; or / and, there is a molecular force between the first functional group and the second functional group; wherein the second functional group includes a hydroxyl group.

4. The composite lithium-rich material according to claim 3, characterized in that: The first lithium-rich material comprises a lithium-rich core and a coating layer coating the lithium-rich core, wherein the coating layer comprises at least one of a carbon conductive agent, a single atom catalyst, and a metal organic framework; wherein at least one of the carbon conductive agent, the single atom catalyst, and the metal organic framework contains the first functional group; and / or The first functional group includes at least one of a carboxyl group, a hydroxyl group, an amino group, an aldehyde group, and a ketone group.

5. The composite lithium-rich material according to claim 4, characterized in that: The decomposition voltage of the lithium-rich material contained in the lithium-rich core is higher than the decomposition voltage of the second lithium-rich material.

6. The composite lithium-rich material according to any one of claims 1, 2, 4 and 5, characterized in that: The first lithium-rich material includes at least one of the following (1) to (3): (1) The particle size of the first lithium-rich material is 1 to 5 μm; (2) a lithium supplement having a decomposition voltage of the first lithium-rich material of 4 to 4.7 V; (3) The first lithium-rich material includes at least one lithium supplement selected from the group consisting of lithium oxalate, lithium carbonate, lithium squarate, and lithium oxide; and / or The second lithium-rich material includes at least one of the following (1) to (4): (1) The particle size of the second lithium-rich material is 20 to 30 μm; (2) a lithium supplement having a decomposition voltage of the second lithium-rich material of 3 to 4 V; (3) The second lithium-rich material includes at least one lithium supplement selected from the group consisting of lithium-rich lithium iron oxide, lithium-rich lithium cobalt oxide, and lithium-rich lithium manganese oxide; (4) The residual alkali content of the second lithium-rich material is 3% to 8%.

7. The composite lithium-rich material according to any one of claims 1, 2, 4 and 5, characterized in that: The composite lithium-rich material includes at least one of the following (1) to (4): (1) The average particle size of the composite lithium-rich material is 5 to 10 μm; (2) The average density of the composite lithium-rich material is 2 to 3 mg / cm 3 ; (3) The pH of the composite lithium-rich material is 9 to 11; (4) The mass ratio of the first lithium-rich material to the second lithium-rich material is (1-10):

1.

8. The method for preparing the composite lithium-rich material according to any one of claims 1 to 7, characterized in that: The steps include: A first lithium-rich material, a second lithium-rich material and a condensation agent are subjected to a first mixing treatment in a solvent, and a condensation reaction is performed to form a connecting group for connecting the first lithium-rich material and the second lithium-rich material between the first lithium-rich material and the second lithium-rich material, thereby obtaining a composite lithium-rich material.

9. The preparation method according to claim 8, characterized in that: The condensing agent includes at least one of hydroxybenzotriazole, dicyclohexylcarbodiimide, and 4-dimethylaminopyridine; and / or The first lithium-rich material, the second lithium-rich material and the condensing agent are mixed in a mass ratio of (1-10):1:(0.02-0.11).

10. A battery, comprising a positive electrode sheet, characterized in that: The positive electrode active material layer of the positive electrode sheet comprises the composite lithium-rich material according to any one of claims 1 to 7 or the composite lithium-rich material prepared by the preparation method according to any one of claims 8 to 9.

11. The battery according to claim 10, characterized in that: The surface of the composite lithium-rich material is further combined with a dispersant and / or a dispersant is further dispersed in the active positive electrode active material layer; wherein the dispersant includes at least one of the following (1) to (2): (1) The mass ratio of the dispersant to the composite lithium-rich material is (1-5): 1000; (2) The dispersant includes at least one of a phosphate dispersant, a titanate dispersant, and a stearic acid glyceryl dispersant.

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