Composite lithium supplement material and preparation method thereof, composite positive electrode material and battery

Abstract

The invention discloses a composite lithium supplement material and a preparation method thereof, a composite positive electrode material and a battery. The composite lithium supplementing material comprises a lithium supplementing material and a self-repairing microcapsule, a core material of the self-repairing microcapsule comprises a repairing agent, and a wall material of the self-repairing microcapsule comprises at least one of a stress deformation material and an electric deformation material. According to the composite lithium supplementing material, particle microcracks of the lithium supplementing material can be repaired under preset conditions through the contained self-repairing microcapsules, so that the integrity of the particle morphology of the lithium supplementing material and the stability of the particle structure of the lithium supplementing material are improved, and the side reaction of a contact interface of the lithium supplementing material and an electrolyte is reduced; therefore, the capacity of the lithium supplement material is improved. The composite positive electrode material comprises a positive electrode material and a self-repairing microcapsule, and a positive plate in the battery contains a composite lithium supplementing material or a composite positive electrode material.

Description

Technical Field

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

[0002] Lithium-ion batteries are widely used in new energy vehicles, energy storage systems, consumer electronics and other fields, which put forward higher requirements on the energy density, capacity retention rate and long life of batteries. Positive electrode materials are an important component of batteries. They store and release lithium ions, play a key role in the electrochemical reaction of batteries, and also determine the electrochemical properties of batteries such as capacity density and cycle performance. In order to further improve the energy density and cycle performance of batteries, lithium supplement materials are generally added to the battery to remove lithium during the charging and discharging of battery cells, especially during the first charging and discharging process, to provide the lithium ions required by the SEI membrane to ensure the active lithium in the battery.

[0003] However, during the long-term cycle of the battery, the crystal phase of the lithium supplement material will change during the lithium removal process, which will cause the volume of the lithium supplement material to change. The most common phenomenon is that the particles of the lithium supplement material are prone to cracks, which seriously affects the capacity of the lithium supplement material. At the same time, during the battery charging and discharging process, the positive electrode material is also accompanied by the phenomenon that the particles are prone to cracks. These phenomena of the lithium supplement material and the positive electrode material affect the electrochemical properties of the battery, such as the energy density and cycle. Summary of the invention

[0004] The purpose of the present application is to overcome the above-mentioned deficiencies of the prior art and to provide a composite lithium supplement material and a preparation method thereof and a battery containing the composite lithium supplement material, so as to solve the technical problem that cracks easily appear in the existing lithium supplement material and positive electrode material particles during the charge and discharge process, affecting their capacity.

[0005] In order to achieve the above application objectives, in the first aspect, the present application provides a composite lithium supplement material. The composite lithium supplement material of the present application includes a lithium supplement material and a self-repairing microcapsule, the core material of the self-repairing microcapsule includes a repairing agent, and the wall material of the self-repairing microcapsule includes at least one of a stress-deformation material and an electrodeformation material.

[0006] The composite lithium-replenishing material in the embodiment of the present application is compounded with a lithium-replenishing material and a self-healing microcapsule, which is used in an electrode and during the charge and discharge process of the battery, when the particles of the lithium-replenishing material have microcracks due to volume changes during the process of lithium ion insertion and extraction, and the self-repairing conditions of the self-repairing microcapsule are triggered, the stress-deformation material and / or the electrodeformation material in the wall material will deform, causing the wall material to rupture, thereby releasing the repair agent contained in the core material of the self-repairing microcapsule, and the released repair agent contacts the surface of the lithium-replenishing material particles and repairs the microcracks of the lithium-replenishing material particles, thereby improving the integrity of the lithium-replenishing material particle morphology and the stability of the lithium-replenishing material particle structure, and reducing the side reactions at the contact interface between the lithium-replenishing material and the electrolyte, so as to improve the capacity of the lithium-replenishing material and the cycle performance.

[0007] The second aspect of the present application provides a method for preparing the composite lithium supplement material of the present application. The method for preparing the composite lithium supplement material of the present application comprises the following steps:

[0008] The self-healing microcapsules are mixed with lithium supplement materials;

[0009] Wherein, the core material of the self-repairing microcapsule includes a repairing agent, and the wall material of the self-repairing microcapsule includes at least one of a stress-deformation material and an electrodeformation material.

[0010] The composite lithium-replenishing material preparation method of the present application embodiment is to mix the self-repairing microcapsules with stress response and / or electro-response with the lithium-replenishing material, so that the prepared composite lithium-replenishing material has the function of the composite lithium-replenishing material of the above application embodiment. When the self-repairing condition of the self-repairing microcapsule is triggered, the wall material of the self-repairing microcapsule will deform and release the repair agent of the core material, thereby repairing the particles of the lithium-replenishing material, thereby improving the integrity of the particle morphology of the lithium-replenishing material and the stability of the structure, and can improve the capacity and cycle performance of the lithium-replenishing material. At the same time, the side reactions at the contact interface between the lithium-replenishing material and the electrolyte are reduced.

[0011] In a third aspect of the present application, a battery is provided. The battery of the present application comprises a positive electrode sheet, the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, the positive electrode active material layer comprises the composite lithium supplement material of the present application or the composite lithium supplement material prepared by the preparation method of the present application;

[0012] Or / and, a repair layer is stacked on the surface of the positive electrode active material layer away from the positive electrode current collector, the repair layer includes self-repairing microcapsules, the core material of the self-repairing microcapsules includes a repairing agent, and the wall material of the self-repairing microcapsules includes at least one of a stress deformation material and an electrodeformable material.

[0013] Since the positive electrode sheet of the battery of the present application contains self-repairing microcapsules, the wall material can be triggered to deform under predetermined conditions, thereby releasing the repair agent of the core material, and repairing the microcracks generated in the positive electrode material and / or lithium supplement particles in the positive electrode sheet during the charging and discharging process, so that the capacity of the positive electrode sheet can be fully utilized and the cycle performance is good, 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 a composite lithium supplement material of the embodiment of the present application, it can also give the battery of the embodiment of the present application a high first effect. 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 supplement material according to an embodiment of the present application;

[0016] Figure 2 This is a scanning electron microscope (SEM) photograph of the composite lithium supplement material in Example A1;

[0017] Figure 3 This is a photo of the positive electrode sheet of the battery in Example B1 after 500 cycles;

[0018] Figure 4 This is a photo of the positive electrode of the battery in Comparative Example B1 after 500 cycles.

[0019] The reference numerals in the specific implementation manner are as follows:

[0020] 10-composite lithium supplement material; 11-particles of lithium supplement material; 12-coating layer. DETAILED DESCRIPTION

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] Lithium-supplementing materials, especially lithium-supplementing positive electrode materials, are regarded as an effective way to improve the energy density of lithium-ion batteries because they have higher theoretical specific capacity and reversible specific capacity than traditional materials.

[0029] However, in actual applications, it is found that the lithium supplement material and the positive electrode material will undergo crystal phase changes during the charging and discharging process, and this change often leads to changes in the volume of the lithium supplement material and the positive electrode material. Specifically, it manifests itself in problems such as capacity attenuation, increased internal resistance, and decreased cycle performance, which seriously affect the energy density and cycle life of lithium batteries. For example, during the full delithiation process of the positive electrode material, the volume of the material will shrink dramatically and the crystal form will change, and microcracks will form on the surface of the material, which will affect the structural stability and capacity of the positive electrode material. At the same time, the electrolyte will also penetrate into the microcracks and react with the residual oxide to produce a large amount of gas or cause the electrolyte to dry up. The inert substances formed by the lithium supplement material after lithium ion deintercalation are also prone to cracks, affecting the stability of the battery structure. Among them, this phenomenon is relatively obvious for lithium supplement materials. This volume change will not only cause microcracks in the particles of the lithium supplement material and the positive electrode material, but also destroy the crystal structure of the material, thereby affecting its electrochemical performance.

[0030] In order to solve this problem, some technologies have been reported to try to modify lithium supplement materials and positive electrode materials, such as improving their structural stability and electrochemical performance through doping, surface coating, nano-sizing and other means. However, although these modification methods have improved the performance of lithium supplement materials and positive electrode materials to a certain extent, there are still some shortcomings, such as high modification cost, limited modification effect, and complex process. There are also reports on the use of positive electrode materials and lithium supplement agents to compensate for the irreversible lithium loss of positive electrode materials during the first charging process, so as to improve the structural stability of positive electrode materials and alleviate the undesirable phenomenon of microcracks in positive electrode material particles. However, since the particle structure of lithium supplement materials during or after delithiation is more unstable than that of positive electrode materials, and microcracks are more likely to occur, it is still impossible to improve the energy density and cycle life of lithium batteries, and it also causes the lithium supplement materials to be unable to fully utilize the lithium supplement capacity.

[0031] Therefore, in order to alleviate the phenomenon that the lithium supplement material and the positive electrode material, especially the lithium supplement material, undergo crystal phase changes during the charge and discharge process, resulting in microcracks in the lithium supplement material particles, and to improve the capacity of the lithium supplement material and the positive electrode material, the embodiment of the present application proposes the following solution.

[0032] [Composite lithium supplement materials]

[0033] In the first aspect, the embodiments of the present application provide a composite lithium supplement material. In some embodiments, the composite lithium supplement material of the embodiments of the present application includes a lithium supplement material and a self-healing microcapsule. Among them, the self-healing microcapsule includes a core material (capsule core) and a wall material (capsule shell or shell layer) formed by coating; the core material includes a repair agent, and the wall material includes at least one of a stress-deformation material and an electrodeformation material.

[0034] In the composite lithium-replenishing material of the embodiment of the present application, the stress-deformation material contained in the wall material of the self-healing microcapsule contained therein refers to a material that can respond to stress or stress changes caused by external actions, thereby changing its shape; when the wall material contains a stress-deformation material, when the stress generated by the external action reaches a certain threshold, the stress-deformation material deforms, causing the wall material to deform and rupture, thereby releasing the repair agent in the core material. Electrodeformable material refers to a material that can respond to changes in the external voltage itself or the Joule heat caused by the voltage. When the external voltage reaches or the Joule heat caused by the voltage reaches a certain threshold, its shape changes, causing the wall material to deform and rupture, thereby releasing the repair agent in the core material. Lithium-replenishing material is a type of material used in the battery field to supplement lithium ions, offset irreversible lithium loss, and thus increase the total capacity and energy density of the battery.

[0035] Therefore, the composite lithium-replenishing material in the embodiment of the present application compounds the lithium-replenishing material with the self-healing microcapsule, and uses it in the electrode. During the charge and discharge process of the battery, when the particles of the lithium-replenishing material have microcracks due to volume changes during or after the de-lithium ion process, and the self-healing microcapsule is subjected to the stress generated by the volume expansion and / or the battery voltage or the Joule heat caused by the voltage, etc., reaching the threshold of the wall material, the stress-deformed material and / or the electrodeformed material in the wall material will deform and cause the wall material to rupture, thereby releasing the repair agent contained in the core material of the self-healing microcapsule. The released repair agent contacts the particle surface of the lithium-replenishing material and repairs the microcracks of the particles of the lithium-replenishing material, thereby improving the integrity of the particle morphology of the lithium-replenishing material, and can inhibit the further expansion of the microcracks of the particles of the lithium-replenishing material, thereby improving the stability of the particle structure of the lithium-replenishing material, and reducing the side reactions at the contact interface between the lithium-replenishing material and the electrolyte, so as to improve the capacity of the lithium-replenishing material.

[0036] In some embodiments, in the composite lithium-replenishing material, the lithium-replenishing material and the self-repairing microcapsules can be separated from each other or in contact with each other. In the embodiment, when the two are separated from each other, when the composite lithium-replenishing material is used for the pole piece, such as when preparing the electrode slurry, the two can be directly mixed in the electrode slurry so that the two are evenly distributed in the electrode slurry. Then, in the active material layer of the prepared pole piece, at least part of the lithium-replenishing material and the self-repairing microcapsules are in contact with each other. In this way, when the battery is in the process of charging and discharging, and when the self-repairing conditions of the self-repairing microcapsules are triggered, the self-repairing microcapsules will release the repair agent in the core material to repair the particles of the lithium-replenishing material, so as to maintain the stability of the particle structure of the lithium-replenishing material and improve its capacity.

[0037] In an embodiment, the self-repairing microcapsules contained in the composite lithium-replenishing material are arranged on the surface of the particles of the lithium-replenishing material. In this way, when the volume of the particles of the lithium-replenishing material changes and microcracks appear during the charging and discharging process, when the self-repairing conditions of the self-repairing microcapsules are triggered, such as the stress and / or voltage or the Joule heat caused by the voltage, etc., reach the threshold of the deformation of the wall material of the self-repairing microcapsules, the wall material of the self-repairing microcapsules deforms and ruptures, thereby releasing the repair agent in the core material. Since the self-repairing microcapsules are directly arranged on the surface of the particles of the lithium-replenishing material, the released repair agent will directly repair the microcracks of the particles of the lithium-replenishing material, thereby improving the repair effect of the self-repairing microcapsules on the particles of the lithium-replenishing material.

[0038] When the self-repairing microcapsules contained in the composite lithium supplement material are arranged on the surface of the particles of the lithium supplement material, in one embodiment, Figure 1 As shown, in the composite lithium-replenishing material 10 of the embodiment of the present application, the self-repairing microcapsule forms a coating layer 12 on the surface of the lithium-replenishing material particle 11, coating the lithium-replenishing material particle 11. The self-repairing microcapsule forms a coating layer 12 to coat the surface of the lithium-replenishing material particle 11, thereby increasing the contact area between the self-repairing microcapsule and the surface of the lithium-replenishing material particle 11, thereby further improving the repair effect and repair efficiency of the self-repairing microcapsule on the lithium-replenishing material particle 11.

[0039] In the embodiment, the thickness of the coating layer 12 can be 1% to 5% of the particle size of the lithium supplement material particle 11. In the embodiment, the thickness of the coating layer 12 can also be 10 to 100 nm, optionally 20 to 50 nm. In the exemplary embodiment, it can be 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, etc., which are typical but non-limiting thicknesses, or a range between any two thickness values. The coating layer 12 in this thickness range can effectively adjust the mass ratio of the self-repairing microcapsules to the lithium supplement material and the distribution of the self-repairing microcapsules on the surface of the lithium supplement material particles, thereby improving the repair effect of the self-repairing microcapsules on the microcracks of the lithium supplement material particles 11.

[0040] In the embodiment, Figure 1 The coating layer 12 formed by the self-repairing microcapsules can be a continuous full coating layer structure, of course, it can also be a continuous non-full coating layer structure, and it can also be an island-shaped distribution combined with coating on the surface of the lithium supplement material particles 11. Among them, the coating layer 12 is a continuous full coating layer structure or a non-full coating layer structure is preferred to the island coating layer structure. The full coating layer structure or the non-full coating layer structure has a relatively large contact surface with the lithium supplement material particles 11, and the repair rate and repair effect of the lithium supplement material particles 11 are relatively excellent.

[0041] In some embodiments, the mass ratio of the self-healing microcapsules to the lithium-replenishing material contained in the composite lithium-replenishing material is (0.05-0.3):1, optionally (0.1-0.2):1. In the exemplary embodiment, it can be a typical but non-limiting ratio such as 0.05:1, 0.1:1, 0.15:1, 0.2:1, 0.25:1, 0.3:1, or a range between any two ratios. The self-healing microcapsules and lithium-replenishing materials in this mass ratio range are compounded to improve the particle repair effect and repair efficiency of the self-healing microcapsules on the lithium-replenishing materials, and improve the structural stability and capacity of the lithium-replenishing materials. On this basis, the content of the lithium-replenishing material in the composite lithium-replenishing material can also be relatively increased, thereby increasing the capacity of the composite lithium-replenishing material.

[0042] Lithium supplement materials:

[0043] In some embodiments, the lithium-supplementing material contained in the composite lithium-supplementing material of each of the above embodiments may include at least one of a binary lithium-containing compound and a ternary lithium-containing compound. In an exemplary embodiment, the ternary lithium-containing compound may include at least one of Li5FeO4, Li6CoO4, Li2NiO2, and Li2C2O4; the binary lithium-containing compound may include at least one of Li2S and Li2O. These lithium-supplementing agents are rich in lithium and have high capacity.

[0044] In the embodiment, the lithium supplement agent can also be selected according to its lithium desorption voltage, such as materials including the following (1) or / and (2) voltage platforms:

[0045] (1) The lithium supplement material with a voltage platform of 2.0V to 4.0V may include at least one of Li5FeO4, Li6CoO4, Li2NiO2, and Li2S;

[0046] (2) The lithium supplement material with a voltage platform of 4.0V to 4.5V may include at least one of Li2C2O4 and Li2O.

[0047] In addition, there is no requirement for the particle size of the lithium supplementing material in the above embodiments, and the particle size can be a conventional particle size of the lithium supplementing material.

[0048] Self-healing microcapsules:

[0049] The self-healing microcapsules contained in the composite lithium-replenishing material of the embodiment of the present application are used for the lithium-replenishing material particles to produce microcracks and other phenomena during the battery charging and discharging process, and when the stress and / or voltage or the Joule heat caused by the voltage to which the wall material of the self-repairing microcapsule is subjected reaches the deformation threshold, the wall material deforms and ruptures to release the repair agent in the core material, thereby repairing the microcracks of the particles of the lithium-replenishing material. When the wall material of the self-repairing microcapsule includes a stress-deformable material, the self-repairing microcapsule can be defined as a stress-responsive self-repairing microcapsule, and when the wall material includes an electro-deformable material, the self-repairing microcapsule can be defined as an electro-responsive self-repairing microcapsule. When the wall material includes both a stress-deformable material and an electro-deformable material, the self-repairing microcapsule can release the repair agent in the self-repairing microcapsule in response to changes in stress and voltage or the Joule heat caused by the voltage.

[0050] In some embodiments, the Dv50 particle size of the self-repairing microcapsule is 10-100 nm, optionally 20-50 nm, and in the exemplary embodiment, it can be 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, etc., which are typical but non-limiting particle sizes, or a range between any two particle size values. This particle size range can increase the area of ​​contact with the particles of the lithium supplementing material. For example, when the self-repairing microcapsule forms a coating layer on the particles of the lithium supplementing material, the content of the self-repairing microcapsule per unit area on the surface of the particles of the lithium supplementing material can be increased, thereby improving the effect of the self-repairing microcapsule on the microcrack repair of the particles of the lithium supplementing material.

[0051] In some embodiments, the thickness of the wall material of the self-repairing microcapsule is 2 to 20 nm, optionally 5 to 10 nm, and in the exemplary embodiment, it can be 2 nm, 5 nm, 8 nm, 10 nm, 12 nm, 15 nm, 18 nm, 20 nm, etc., typical but non-limiting thicknesses or a range between any two thickness values. Wherein, the wall material as described above refers to the shell layer of the self-repairing microcapsule, and therefore, the thickness of the wall material refers to the shell thickness of the self-repairing microcapsule. The thickness of the wall material in this thickness range can effectively improve the sensitivity of the self-repairing microcapsule to self-repair.

[0052] In some embodiments, the stress-deformable material contained in the wall material of the self-healing microcapsule may include at least one of a stress-sensitive polymer, a pressure-sensitive material, and a reversible dynamic cross-linked polymer. In the embodiments of the present application, the stress-sensitive polymer refers to a type of polymer material that can sense environmental changes (such as stress or external force) and change its own shape or properties accordingly, a pressure-sensitive material refers to a type of material that will produce a resistance change phenomenon under the action of a force, and a reversible dynamic cross-linked polymer refers to a type of polymer material that forms a polymer network based on a reversible force (such as a non-covalent interaction or a dynamic covalent bond).

[0053] In the demonstration example, the stress-sensitive polymer may include at least one of polyurethane (PU), polydimethylsiloxane (PDMS), polyamide (PA), polyacrylate (PAA), etc.

[0054] In the demonstration example, the above-mentioned pressure-sensitive material may include at least one of zinc oxide, silicon carbide, barium titanate, etc.

[0055] In the demonstration example, the above-mentioned reversible dynamic cross-linked polymer may include at least one of disulfide bond polyurethane (PU-SS), boroxine ring dynamically cross-linked supramolecular thermosetting polymer, boroxane cross-linked supramolecular thermosetting polymer, etc.

[0056] When the stress generated by the volume expansion of the lithium supplement material during the charge and discharge process reaches the threshold of the deformation response of the stress deformation material, these stress deformation materials can deform, causing the wall material to rupture and release the repair agent in the core material, so as to repair the microcracks of the particles of the lithium supplement material, thereby improving the stability of the particle structure of the lithium supplement material and the utilization of the capacity of the lithium supplement material.

[0057] In some embodiments, the electro-deformation voltage of the electro-deformation material contained in the wall material of the self-healing microcapsule is 3.2 - 4.8V, optionally 3.5 - 4.5V. In the demonstration example, it can be typical but non-limiting voltages such as 3.2V, 3.5V, 3.7V, 3.9V, 4.1V, 4.3V, 4.5V, 4.8V, etc. or the range between any two voltage values. This electro-deformation voltage refers to the voltage when the electro-deformation material deforms (that is, the deformation voltage threshold of the electro-deformation material). When the voltage reaches a certain voltage threshold, the electro-deformation material begins to deform, causing the wall material of the self-healing microcapsule to rupture and release the repair agent in the core material.

[0058] In some embodiments, the phase transition temperature T of the electro-deformation material contained in the wall material of the self-healing microcapsule can be 40 ≤ T ≤ 60 and / or 60 < T ≤ 80 °C. In the demonstration example, it can be typical but non-limiting phase transition temperatures such as 40 °C, 45 °C, 50 °C, 55 °C, 60 °C, etc. or the range between any two phase transition temperature values and / or 61 °C, 61 °C, 70 °C, 75 °C, 80 °C, etc. or the range between any two phase transition temperature values. This phase transition temperature refers to the temperature when the deformation material deforms. When the phase transition temperature reaches a certain temperature threshold, the electro-deformation material begins to deform, causing the wall material of the self-healing microcapsule to rupture and release the repair agent in the core material.

[0059] The electrodeformation voltage and / or phase change temperature in the above range can deform at a predetermined voltage and / or temperature, thereby relatively accurately controlling the wall material of the self-healing microcapsule to deform and release the repair agent, thereby relatively accurately repairing the particles of the lithium-replenishing material.

[0060] In some embodiments, the electrodeformable material may include at least one of a liquid crystal polymer (LCP), a shape memory polymer (SMP), a piezoelectric material, an ionic liquid crystal polymer, and an electroactive polymer (EAP). In the embodiments of the present application, a liquid crystal polymer refers to a polymer material that can exist in a liquid crystal phase under certain conditions, an ionic liquid crystal polymer refers to a new gel material composed of a liquid crystal polymer and an ionic liquid, a shape memory polymer refers to a polymer material that changes its initial shape under certain conditions and fixes it, and then restores its initial shape through external conditions (such as heat, electricity, light, chemical induction, etc.), a piezoelectric material refers to a class of materials that generate electric charge under the action of a force, and an electroactive polymer refers to a class of polymers that can change its shape or size under the action of an electric field.

[0061] In an exemplary embodiment, the liquid crystal polymer may include at least one of a main chain liquid crystal polymer and a side chain liquid crystal polymer; wherein the main chain liquid crystal polymer may include at least one of poly(hydroquinone terephthaloyl), polyphenylquinoline (PPQ) poly(aryletherimide) (PAEI), etc.; the side chain liquid crystal polymer may include at least one of a poly(methyl methacrylate) (PMMA)-based liquid crystal polymer, a poly(paraphenylene) (PPP)-based liquid crystal material, etc.

[0062] In an exemplary embodiment, the above-mentioned shape memory polymer may include at least one of a thermally responsive shape memory polymer and an electrically responsive shape memory polymer; wherein the thermally responsive shape memory polymer may include at least one of polycaprolactone (PCL), polylactic acid (PLA), polyurethane elastomer (PU), etc.; the electrically responsive shape memory polymer may include at least one of a liquid crystal elastomer (LCE), a polypyrrole-doped shape memory material), etc.

[0063] In the exemplary embodiment, the above-mentioned piezoelectric material may include at least one of an inorganic piezoelectric material and an organic piezoelectric material; wherein the inorganic piezoelectric material may include at least one of lead zirconate titanate (PZT), barium titanate (BaTiO3), etc.; the organic piezoelectric material may include at least one of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-trifluoroethylene copolymer (PVDF-TrFE), etc.

[0064] In an exemplary embodiment, the ionic liquid crystal polymer may include at least one of polyhydroquinone terephthalamide, polyphenylquinoline (PPQ), polyaryletherimide (PAEI), polymethylmethacrylate (PMMA)-based liquid crystal polymer, polyparaphenylene (PPP), and the like.

[0065] In an exemplary embodiment, the electroactive polymer (EAP) may include at least one of polythiophene (PTh), polydioxythiophene (PEDOT), polyaniline (PANI), polypyrrole (PPy), and the like.

[0066] The above-mentioned electrodeformable materials have relatively precise voltage and / or phase change temperature, and can be selected according to the lithium delithiation voltage characteristics of at least one material in the lithium replenishing material such as the positive electrode material and the lithium replenishing agent, so that the self-repairing start of the self-repairing microcapsule is adapted to the working characteristics of the lithium replenishing material, thereby improving the particle modification effect of the self-repairing microcapsule on the lithium replenishing material.

[0067] In some embodiments, the repair agent contained in the self-repairing microcapsule accounts for 50% to 90% of the mass of the self-repairing microcapsule, and optionally 60% to 80%. In the exemplary embodiment, it can be a typical but non-limiting mass content such as 50%, 60%, 70%, 80%, 90%, or a range between any two content values. The repair agent in this mass content range can increase its mass proportion in the self-repairing microcapsule, thereby reducing the content of the self-repairing microcapsule in the composite lithium supplement material, relatively increasing the mass proportion of the lithium supplement material in the composite lithium supplement material, and increasing the capacity density of the composite lithium supplement material.

[0068] In some embodiments, the repair agent contained in the core material of the self-healing microcapsule includes at least one of a lithium conductive polymer, a conductive polymer, a metal oxide, an ion gel, a nano-carbon material, a nano-metal material, a composite material repair agent, and the like. In the exemplary embodiment, the lithium conductive polymer may include at least one of poly(ethylene oxide) (PEO), lithium ion doped polymer (such as polyethylene oxide-lithium trifluoromethanesulfonate, PEO-LiCF3SO3), and lithium ion conductive phosphate polymer; the conductive polymer may include at least one of polythiophenes, polyaniline (PANI), polypyrrole (PPy), polydiacetylene (PDA), and conductive polymer composite materials (such as PANI / carbon nanotube composites); the metal oxide may include at least one of SiO2, TiO2, and aluminum oxide (Al2O3); the ion gel may include at least one of EMIM-TFSI / PVDF gel, PEO / LiTFSI gel, ternary PEO / LiTFSI / EmimCl ion gel, etc.; the nanocarbon material may include at least one of conductive carbon nanotubes, reduced graphene oxide (rGO), etc.; the nanometal material may include but is not limited to nanosilver particles (AgNPs), etc.; the composite material repair agent may include metal-organic framework materials, such as at least one of MOF-801, MOF-5, ZIF-8, etc.

[0069] When the wall material of the self-repairing microcapsule is broken, the above-mentioned repair agent materials are released and filled and bonded to the microcracks of the lithium supplement material particles, thereby repairing the microcracks of the lithium supplement material particles, thereby improving the stability of the particle structure of the lithium supplement material, so as to improve the capacity and cycle performance of the lithium supplement material. Moreover, the repair agents also have good electrical conductivity. After completing the repair of the lithium supplement material particles, they can also effectively maintain or improve the conductivity of the lithium supplement material.

[0070] In some embodiments, on the basis of the above embodiments, the core material of the self-healing microcapsule may contain other functional components in addition to the above-mentioned repairing agent. The functional component may be an auxiliary agent that assists the above-mentioned repairing agent to fully exert its effect, or it may be a functional component that improves the lithium replenishment effect. As in the embodiment, the core material of the self-healing microcapsule includes the above-mentioned repairing agent and the lithium replenishing agent. Among them, the lithium replenishing agent can be understood as the lithium replenishing material contained in the composite lithium replenishing material of the embodiment of the present application, and the type of the lithium replenishing agent may be the same as or different from the type of the above-mentioned lithium replenishing material. In this way, adding a lithium replenishing agent to the core material can increase the capacity of the composite lithium replenishing material, and it is directly arranged in the core material and can directly contact the repairing agent, so that the repairing agent can directly repair the microcracks generated by the lithium replenishing agent particles during the delithiation process, thereby improving the structural stability of the lithium replenishing agent particles and improving the capacity.

[0071] When the core material contains other functional components, the content of other functional components should not affect the proportion of the repair agent in the self-healing microcapsule. For example, in the embodiment, when the core material contains a lithium supplement, the mass ratio of the lithium supplement to the repair agent can be (20-100):1. Optionally, it can be a typical but non-limiting mass content such as 20:1, 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, 90:1, 100:1, or a range between any two content values.

[0072] In a second aspect, the present invention also provides a method for preparing the composite lithium supplement material. The method for preparing the composite lithium supplement material in the present invention comprises the following steps:

[0073] S10: Mixing the self-repairing microcapsules with the lithium replenishing material.

[0074] In the preparation method of the composite lithium-replenishing material of the embodiment of the present application, the self-repairing microcapsule and the lithium-replenishing material in step S10 are respectively the self-repairing microcapsule and the lithium-replenishing material contained in the composite lithium-replenishing material of the embodiment of the present application. Therefore, the core material of the self-repairing microcapsule in step S10 includes a repairing agent, and the wall material of the self-repairing microcapsule includes at least one of a stress-deformation material and an electrodeformation material.

[0075] The preparation method of the composite lithium supplement material of the embodiment of the present application is to mix the self-repairing microcapsules with stress response and / or electro-response characteristics with the lithium supplement material, so that the prepared composite lithium supplement material has the function of the composite lithium supplement material of the embodiment of the present application, specifically, the composite lithium supplement material is used for the electrode and in the charging and discharging process of the battery, when the particles of the lithium supplement material have microcracks due to the volume change in the process of lithium ion insertion and extraction and the stress generated by the volume expansion of the self-repairing microcapsule reaches the stress of the wall material or / and the battery voltage or the Joule heat generated by the voltage reaches the deformation threshold of the wall material, the stress deformation material and the electro-deformation material in the wall material will deform and cause the wall material to rupture, so that the repair agent in the core material of the self-repairing microcapsule is released, contacts with the particle surface of the lithium supplement material and repairs the microcracks of the particles of the lithium supplement material, thereby improving the integrity of the particle morphology of the lithium supplement material, and can inhibit the continued expansion of the microcracks of the particles of the lithium supplement material, thereby improving the stability of the particle structure of the lithium supplement material, so as to improve the capacity of the lithium supplement material and the cycle performance. At the same time, the side reaction of the contact interface between the lithium supplement material and the electrolyte is reduced.

[0076] In some embodiments, the self-healing microcapsules in step S10 can be prepared by at least one method selected from the group consisting of an emulsification method, a spray drying method, a solvent volatilization method, and a copolymerization method.

[0077] As described in the embodiment, the self-repairing microcapsules can be prepared by an emulsification method comprising the following steps:

[0078] S11a: dispersing the core material in the oil phase to form an emulsion;

[0079] S12a: adding wall material raw materials to the emulsion prepared in step S11a, and performing emulsification treatment to form an emulsion having a core-shell structure microcapsule;

[0080] S13a: adding a crosslinking agent to the emulsion prepared in step S12a to perform a chemical crosslinking reaction to crosslink and solidify the wall material raw materials to form self-repairing microcapsules;

[0081] S14a: subjecting the self-repairing microcapsules prepared in step S13a to solid-liquid treatment and drying treatment to obtain self-repairing microcapsules.

[0082] The self-repairing microcapsules prepared by the emulsification method can cross-link and polymerize the wall material in situ to form the wall material and in situ coat the core material, so that the prepared self-repairing microcapsules have a self-repairing effect.

[0083] Among them, the oil phase in step S11a may include at least one of liquid silicone oil and organic solvent, and of course other oil phase materials. The core material in step S12a can be determined according to the type of core material of the self-repairing microcapsule mentioned above. The wall material raw material in step S12a can also be determined according to the type of wall material of the self-repairing microcapsule mentioned above, such as the wall material raw material can be a self-repairing microcapsule wall material precursor or the wall material itself. In the exemplary embodiment, the wall material raw material can be at least one of a prepolymer of polyurethane and a prepolymer of polydimethylsiloxane, which, after the cross-linking reaction in step S13a, form a wall material containing polyurethane and a wall material of polydimethylsiloxane, respectively. The emulsification treatment in step S12a can control the emulsification treatment method, emulsification rate, solution viscosity and surfactant content to adjust the size of the microdroplets of the core-shell structure microcapsule.

[0084] As described in the embodiment, the self-repairing microcapsules can be prepared by a spray drying method comprising the following steps:

[0085] S11b: dispersing the core material in water or an organic solvent to form a suspension;

[0086] S12b: dissolving the wall material raw material in a corresponding solvent, and mixing it with the suspension in step S11b to form a mixed solution;

[0087] S13b: spray drying the mixed solution in S12b to form microcapsules containing a core material coated with a wall material;

[0088] S14b: collecting the spray-dried microcapsules and further drying and processing them.

[0089] Among them, the organic solvent in step S11b is an organic solvent that cannot dissolve the core material. The raw material of the wall material in step S11b can be determined according to the type of wall material of the self-repairing microcapsule mentioned above, such as the self-repairing microcapsule wall material itself. In the exemplary embodiment, the raw material of the wall material can be at least one of polyurethane and polydimethylsiloxane. The spray drying treatment in step S13b uses a spray drying device to spray the mixed liquid in step S12b into a high-temperature air flow, and the droplets evaporate rapidly, so that the wall material dissolved in the solvent is in situ combined with the surface of the core material particles, and forms a coating layer, which is the wall material of the microcapsule.

[0090] As in the embodiment, the self-healing microcapsules can be prepared by a solvent evaporation method comprising the following steps:

[0091] S11c: dissolving or dispersing the core material in a volatile solvent to form a uniform solution or suspension;

[0092] S12c: adding the wall material to the solution or suspension in step S11c and mixing them so that the core material and the wall material form a uniform dispersion;

[0093] S13c: placing the dispersion containing the dispersion in step S12c under low temperature conditions and performing solvent volatilization treatment, so that the wall material solidifies while the solvent evaporates, and the self-healing microcapsules are in situ combined and coated on the surface of the core material;

[0094] S14c: Drying the self-repairing microcapsules in step S13c to remove residual solvent.

[0095] The volatile solvent in step S11c can be a commonly used volatile organic solvent. The core material in step S11c and the wall material in step S12c can be determined according to the core material and wall material types of the self-healing microcapsule described above. In an exemplary embodiment, the wall material can include at least one of a liquid crystal polymer or a shape memory polymer.

[0096] As described in the embodiment, the self-repairing microcapsules can be prepared by a copolymerization method comprising the following steps:

[0097] S11d: dissolving the wall material raw material in the oil phase, and dissolving or dispersing the core material in the oil phase to prepare a uniform solution.

[0098] S12d: adding the oil phase solution in step S11d to the water phase, adding a surfactant, and emulsifying to form an emulsion, so that the wall material raw materials form a microcapsule shell on the surface of the droplets;

[0099] S13d: controlling the temperature to polymerize or solidify the wall material raw materials to form wall materials and cover the core materials to form stable self-repairing microcapsules;

[0100] S14d: subjecting the self-repairing microcapsules in step S13d to solid-liquid separation and purification, and obtaining the self-repairing microcapsules after drying.

[0101] Wherein, the oil phase in step S11d may include an organic solvent that can dissolve the wall material raw material. The core material in step S11d may be determined according to the type of core material of the self-repairing microcapsule described above. The wall material raw material in step S11d may also be determined according to the type of wall material of the self-repairing microcapsule described above, such as the wall material raw material may be a self-repairing microcapsule wall material precursor or the wall material itself. In the exemplary embodiment, the wall material raw material may include at least one of a liquid crystal polymer monomer, a liquid crystal polymer, a shape memory polymer monomer, and a shape memory polymer. When it is a liquid crystal polymer monomer or a shape memory polymer monomer, after the cross-linking reaction in step S13d, it forms a wall material containing a liquid crystal polymer or a shape memory polymer, respectively. The emulsification treatment in step S12d may control the emulsification treatment method, emulsification rate, solution viscosity, and surfactant content to adjust the size of the microcapsule droplets.

[0102] In some embodiments, the method of mixing the self-healing microcapsules with the lithium supplementing material in step S10 may include at least one of a dry mixing method, a coating method, an electrostatic spraying method, a solution dispersion method, and the like.

[0103] As in the embodiment, the self-healing microcapsules and the lithium supplementing material can be mixed by a dry mixing method comprising the following steps:

[0104] S11e: dry-mixing the lithium supplement material and the self-healing microcapsules according to a certain proportion to obtain a mixture;

[0105] S12e: In a protective atmosphere, the mixture in step S11e is subjected to high-speed stirring treatment, so that at least part of the self-healing microcapsules are combined with the surface of the lithium-replenishing material to obtain the composite lithium-replenishing material of the embodiment of the present application.

[0106] In step S11e, the lithium-replenishing material and the self-healing microcapsules can be mixed in a ratio of (0.05-0.3) to the lithium-replenishing material. The protective atmosphere of step S12e can be an inert gas environment, such as but not limited to an argon environment, or a vacuum environment; the speed of the high-speed stirring process can be a speed higher than 1000 revolutions per minute (RPM).

[0107] By directly mixing the lithium-replenishing material and the self-healing microcapsules at high speed, the two can be evenly dispersed, and under mutual contact and interaction, at least part of the self-healing microcapsules are adsorbed and combined on the particle surface of the lithium-replenishing material, thereby increasing the contact between the two.

[0108] As in the embodiment, the self-repairing microcapsules and the lithium supplementing material can be mixed by a coating method comprising the following steps:

[0109] S11f: applying a first suspension containing self-repairing microcapsules to the surface of particles of the lithium supplementing material to form a first wet film containing self-repairing microcapsules on the surface of particles of the lithium supplementing material;

[0110] S12f: Drying the first wet film in step S11f to remove the solvent, thereby obtaining the composite lithium-replenishing material of the embodiment of the present application containing a self-repairing microcapsule coating layer.

[0111] The solvent of the first suspension in step S11f can be a low-volatile solvent. The thickness of the wet film in step S11f can make the thickness of the self-repairing microcapsule coating layer formed in step S12f as 10-100 nm as the coating layer contained in the composite lithium supplement material in the above text application embodiment, and can also make the mass ratio of the self-repairing microcapsule to the lithium supplement material in the composite lithium supplement material be (0.05-0.3):1. The drying process in step S12f can be vacuum drying to improve the stability of the lithium supplement material.

[0112] As in the embodiment, the self-repairing microcapsules and the lithium supplementing material can be mixed by an electrostatic spraying method comprising the following steps:

[0113] S11h: spraying a second suspension containing self-repairing microcapsules on the surface of particles of the lithium supplementing material to form a second wet film on the surface of particles of the lithium supplementing material;

[0114] S12h: Dry the second wet film in step S11h to remove the solvent, and obtain the composite lithium-replenishing material of the embodiment of the present application containing a self-repairing microcapsule coating layer.

[0115] Wherein, the solvent of the second suspension in step S11h can be an organic solvent, such as a volatile organic solvent. The thickness of the second wet film in step S11h can make the thickness of the self-repairing microcapsule coating layer formed in step S12h as 10 to 100 nm as the coating layer contained in the composite lithium supplement material in the above text application embodiment, and can also make the mass ratio of the self-repairing microcapsule to the lithium supplement material in the composite lithium supplement material be (0.05 to 0.3): 1. The drying process in step S12h can be vacuum drying to improve the stability of the lithium supplement material.

[0116] As in the embodiment, the self-healing microcapsules and the lithium supplementing material can be mixed by a solution dispersion method comprising the following steps:

[0117] S11g: ultrasonically mixing the lithium supplement material and the third suspension containing the self-repairing microcapsules to obtain a dispersed slurry;

[0118] S12g: In a protective atmosphere, the dispersed slurry in step S11g is further stirred and mixed to obtain a mixture slurry;

[0119] S13g: Dry the mixture slurry in step S11g to obtain the composite lithium supplement material of the embodiment of the present application.

[0120] Among them, the ultrasonic mixing treatment in step S11g makes at least the self-healing microcapsules distributed and combined on the surface of the lithium-replenishing material; the solvent of the third suspension in step S11g can be an organic solvent. The lithium-replenishing material and the third suspension in step S11g can be mixed in a ratio of (0.05-0.3):1 in the mass ratio of the self-healing microcapsules to the lithium-replenishing material in the composite lithium-replenishing material formed in step S13h. The protective atmosphere in step S12g can be an inert gas environment, such as but not limited to an argon environment, or a vacuum environment; the drying treatment in step S13g can be vacuum drying to improve the stability of the lithium-replenishing material.

[0121] [Composite cathode material]

[0122] In a third aspect, the present application also provides a composite positive electrode material. The composite positive electrode material of the present application includes a positive electrode material or a positive electrode material and a lithium supplement material, and also includes a self-repairing microcapsule, the core material of the self-repairing microcapsule includes a repair agent, and the wall material of the self-repairing microcapsule includes at least one of a stress-deformation material and an electrodeformation material.

[0123] In the composite positive electrode material of the embodiment of the present application, the self-repairing microcapsules contained therein are the self-repairing microcapsules contained in the composite lithium-replenishing material of the embodiment of the present application. When the composite positive electrode material contains a lithium-replenishing material, the lithium-replenishing material contained therein is also the lithium-replenishing material contained in the composite lithium-replenishing material of the embodiment of the present application. In order to save the length of the description of the embodiment of the present application, the self-repairing microcapsules contained in the composite positive electrode material or the further lithium-replenishing material contained therein will not be described in detail. The positive electrode material contained in the composite positive electrode material refers to the positive electrode material in the field of batteries.

[0124] In this way, the composite positive electrode material of the embodiment of the present application compounds the positive electrode material or the positive electrode material with the lithium supplement material with the self-healing microcapsule, and uses it in the battery. During the charging and discharging process of the battery, when the particles of the positive electrode material or the positive electrode material and the lithium supplement material have microcracks due to volume changes in the process of lithium ion insertion and extraction, and the self-healing microcapsule is subjected to the stress generated by the volume expansion and / or the battery voltage or the Joule heat caused by the voltage, etc., reaching the threshold of the wall material, the stress-deformed material and / or the electrodeformed material in the wall material will deform and cause the wall material to rupture, thereby releasing the repair agent contained in the core material of the self-healing microcapsule, and the released repair agent and The positive electrode material or the positive electrode material and the lithium-supplementing material contact the particle surface and repair the microcracks of the particles of the positive electrode material or the positive electrode material and the lithium-supplementing material, thereby improving the integrity of the particle morphology of the positive electrode material or the positive electrode material and the lithium-supplementing material, and can inhibit the continued expansion of the microcracks of the particles of the positive electrode material or the positive electrode material and the lithium-supplementing material, thereby improving the stability of the particle structure of the positive electrode material or the positive electrode material and the lithium-supplementing material, and reducing the side reactions at the contact interface between the positive electrode material or the positive electrode material and the lithium-supplementing material and the electrolyte, so as to improve the capacity of the positive electrode material or the positive electrode material and the lithium-supplementing material, and improve the cycle performance of the positive electrode material or the positive electrode material and the lithium-supplementing material.

[0125] In some embodiments, in the composite positive electrode material, the positive electrode material or the positive electrode material and the lithium supplement material and the self-repairing microcapsule can be separated from each other or in contact with each other. In the embodiment, when separated from each other, when the composite lithium supplement material is used for the pole piece, such as when preparing the electrode slurry, the positive electrode material or the positive electrode material and the lithium supplement material can be directly mixed with the self-repairing microcapsule such as in the electrode slurry, so that they are evenly distributed in the electrode slurry, then in the active material layer of the prepared pole piece, at least part of the positive electrode material or the positive electrode material and the lithium supplement material and the self-repairing microcapsule and the self-repairing microcapsule are in contact with each other. In this way, when the battery is in the process of charging and discharging, and when the self-repairing condition of the self-repairing microcapsule is triggered, the self-repairing microcapsule will release the repair agent in the core material to repair the particles of the positive electrode material or the positive electrode material and the lithium supplement material, so as to maintain the particle structure stability of the positive electrode material or the positive electrode material and the lithium supplement material and improve its capacity, thereby improving the cycle performance of the positive electrode material.

[0126] In an embodiment, the self-repairing microcapsules contained in the composite positive electrode material are arranged on the surface of the particles of the positive electrode material or the positive electrode material and the lithium supplement material. In this way, when the volume of the particles of the lithium supplement material changes and microcracks appear during the charging and discharging process, when the self-repairing conditions of the self-repairing microcapsules are triggered, such as the stress and / or voltage or the Joule heat caused by the voltage reaching the threshold of the deformation of the wall material of the self-repairing microcapsules, the wall material of the self-repairing microcapsules deforms and ruptures, thereby releasing the repair agent in the core material. Since the self-repairing microcapsules are directly arranged on the surface of the particles of the positive electrode material or the positive electrode material and the lithium supplement material, the released repair agent will directly repair the microcracks of the particles of the positive electrode material or the positive electrode material and the lithium supplement material, thereby improving the repairing effect of the self-repairing microcapsules on the particles of the positive electrode material or the positive electrode material and the lithium supplement material.

[0127] When the self-repairing microcapsules contained in the composite positive electrode material are arranged on the surface of the positive electrode material or the positive electrode material and the lithium supplement material particles, in one embodiment, the self-repairing microcapsules form a coating layer on the surface of the positive electrode material or the positive electrode material and the lithium supplement material particles, coating the positive electrode material or the positive electrode material and the lithium supplement material particles. Figure 1 The self-repairing microcapsules form a coating layer to coat the positive electrode material or the positive electrode material and the lithium supplement material particle surface, effectively increasing the contact area between the self-repairing microcapsules and the positive electrode material or the positive electrode material and the lithium supplement material particle surface, thereby further improving the self-repairing microcapsules on the positive electrode material or the positive electrode material and the lithium supplement material particle repair effect and repair efficiency, thereby further improving the capacity and cycle performance of the composite positive electrode material.

[0128] In the embodiment, when the self-healing microcapsules form a coating layer, the coating layer can be the same as the coating layer formed on the surface of the lithium supplement material particles by the self-healing microcapsules contained in the composite lithium supplement material mentioned above. As in the embodiment, the thickness can also be 1% to 5% of the particle size of the positive electrode material or the lithium supplement material. The thickness of the coating layer can also be 10 to 100 nm, optionally 20 to 50 nm.

[0129] In some embodiments, the mass ratio of the self-healing microcapsules contained in the composite positive electrode material to the positive electrode material or to the total mass ratio of the positive electrode material and the lithium supplement material is (0.02-0.2):1.

[0130] By controlling the contact mode, mass ratio, etc. between the self-repairing microcapsules and the positive electrode material or the positive electrode material and the lithium-supplementing material particles within the above range, it is possible to improve the self-repairing microcapsules' repair effect and efficiency on the positive electrode material or the positive electrode material and the lithium-supplementing material particles, and improve the structural stability, capacity utilization and cycle performance of the positive electrode material or the positive electrode material and the lithium-supplementing material.

[0131] Cathode Material:

[0132] In some embodiments, the above-mentioned positive electrode material may include at least one of a layered positive electrode material, a spinel-type positive electrode material, an olivine-type positive electrode material, etc. In an exemplary embodiment, the layered positive electrode material may include at least one of lithium cobalt oxide (LCO), ternary materials (commonly used nickel cobalt manganese oxide (NCM), nickel cobalt aluminum oxide (NCA), lithium manganese oxide (LiMnO2), lithium-rich manganese-based positive electrode materials xLi2MnO3·(1-x)LiMO2, etc.; the spinel-type positive electrode material may include at least one of lithium manganese oxide (LMO), lithium vanadium oxide (LiV2O4), lithium titanium oxide (LiTi2O4), etc.; the olivine-type positive electrode material may include at least one of lithium iron phosphate, lithium iron manganese phosphate, etc. These positive electrode materials have relatively high capacity density and good cycle performance, and can fully deintercalate lithium ions in the presence of self-healing microcapsules to give full play to the capacity.

[0133] In addition, there is no requirement for the particle size of the positive electrode material in the above embodiments, which can be a conventional particle size of the positive electrode material and can be adjusted and selected as needed.

[0134] Based on the types of positive electrode materials and lithium supplement materials and self-healing microcapsules mentioned above, in some embodiments, when the positive electrode materials mentioned above are lithium iron phosphate positive electrode materials (working voltage is 2.0-3.6V) and Li5FeO4 lithium supplement agents, the wall materials of the self-healing microcapsules are selected from electrodeformable materials, such as the electrodeformable materials including at least one of polyurethane, polycaprolactone (PCL), and polylactic acid (PLA), and the electrodeformation voltage, that is, the deformation voltage threshold, is 3.5-3.6V. At this time, when the voltage of the battery cell reaches 3.5-3.6V, the crystal phase of the lithium iron phosphate positive electrode material will undergo certain changes during the charging and discharging process, resulting in certain microcracks in the particles of the lithium iron phosphate positive electrode material; at the same time, the inert substances formed by the Li5FeO4 lithium supplement agent after the first charge completes the release of lithium are also prone to microcracks. The presence of self-healing microcapsules can trigger deformation of the wall material in the range of 3.5 to 3.6 V, causing the wall material to rupture and release the repair agent in the core material, so that the repair agent can fill the microcracks of the lithium iron phosphate positive electrode material particles and the Li5FeO4 lithium supplement agent particles in time. On the one hand, it can effectively inhibit the continued rupture of the lithium iron phosphate positive electrode material particles and the Li5FeO4 lithium supplement agent particles, and improve the stability of the particle structure of the two, thereby improving the capacity and cycle performance of the lithium iron phosphate positive electrode material; on the other hand, it can effectively alleviate the penetration of the electrolyte into the interior of the two particles through the microcracks of the two particles, thereby avoiding the side reactions between the lithium iron phosphate positive electrode material particles and the Li5FeO4 lithium supplement agent and the electrolyte, thereby improving the cycle performance and safety performance of the battery cell.

[0135] In some embodiments, when the above positive electrode material is lithium manganese iron phosphate (LMFP) (working voltage is 4.2V) and Li6CoO4 lithium supplement (decomposition voltage is 4.1-4.2V), the wall material of the self-healing microcapsule is an electrodeformable material, and the electrodeformable material includes an inorganic piezoelectric material, and its electrodeformation voltage, that is, the deformation voltage threshold, is 4.1-4.2V; wherein, the inorganic piezoelectric material may include at least one of lead zirconate titanate (PZT), barium titanate (BaTiO3), etc. At this time, when the voltage of the battery cell reaches 4.1-4.2V, the crystal phase of the lithium manganese iron phosphate positive electrode material will undergo certain changes during the charging and discharging process, resulting in certain microcracks in the particles of the lithium manganese iron phosphate positive electrode material; at the same time, the inert substance formed by the Li6CoO4 lithium supplement after the first charge completes the release of lithium is also prone to microcracks. The presence of self-healing microcapsules can trigger deformation of the wall material at 4.1-4.2V, causing the wall material to rupture and release the repair agent in the core material, so that the repair agent can fill the microcracks of the lithium iron manganese phosphate positive electrode material particles and the Li6CoO4 lithium supplement agent particles in time. On the one hand, it can effectively inhibit the continued rupture of the lithium iron manganese phosphate positive electrode material particles and the Li6CoO4 lithium supplement agent particles, and improve the stability of the particle structure of the two, thereby improving the capacity and cycle performance of the lithium iron manganese phosphate positive electrode material; on the other hand, it can effectively alleviate the penetration of the electrolyte into the interior of the two particles through the microcracks of the two particles, thereby avoiding the side reactions between the lithium iron manganese phosphate positive electrode material particles and the Li6CoO4 lithium supplement agent and the electrolyte, thereby improving the cycle performance and safety performance of the battery cell.

[0136] In some embodiments, when the above-mentioned lithium supplement material is a high-nickel ternary positive electrode material (NCM or NCA, with an operating voltage of 4.5V) and a Li6CoO4 lithium supplement (with a decomposition voltage of 4.1-4.2V), the wall material of the self-healing microcapsule is an electrodeformable material, and the electrodeformable material includes at least one of polypyrrole, polyterephthaloyl hydroquinone, polyphenylquinoline (PPQ), polyaryletherimide (PAEI), polymethyl methacrylate (PMMA)-based liquid crystal polymer, and polyparaphenylene (PPP)-based liquid crystal material, and its electrodeformation voltage, that is, the deformation voltage threshold, is 4.3-4.5V. At this time, when the voltage of the battery cell reaches 4.3-4.5V, the crystal phase of the high-nickel ternary positive electrode material will undergo certain changes during the charge and discharge process, resulting in certain microcracks in the particles of the high-nickel ternary positive electrode material; at the same time, the inert substance formed by the Li6CoO4 lithium supplement after the first charge completes the release of lithium is also prone to microcracks. The presence of self-healing microcapsules can trigger deformation of the wall material at 4.3-4.5V, causing the wall material to rupture and release the repair agent in the core material, so that the repair agent can fill the microcracks of the high-nickel ternary positive electrode material particles and the Li6CoO4 lithium supplement agent particles in time. On the one hand, it can effectively inhibit the continued rupture of the high-nickel ternary positive electrode material particles and the Li6CoO4 lithium supplement agent particles, and improve the stability of the particle structure of the two, thereby improving the capacity and cycle performance of the high-nickel ternary positive electrode material; on the other hand, it can effectively alleviate the penetration of the electrolyte into the interior of the two particles through the microcracks of the two particles, thereby avoiding the side reactions between the high-nickel ternary positive electrode material particles and the Li6CoO4 lithium supplement agent and the electrolyte, thereby improving the cycle performance and safety performance of the battery cell.

[0137] [Battery]

[0138] In a fourth aspect, the embodiments of the present application also provide 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.

[0139] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer bonded to at least one surface of the positive electrode current collector. In the embodiment, the positive electrode current collector of the positive electrode sheet can be but is not limited to any one of copper foil and aluminum foil.

[0140] 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, or further contains a lithium supplement material.

[0141] In the embodiment, the positive electrode active material in the positive electrode active material layer may include the composite positive electrode material of the above-mentioned embodiment. When the composite positive electrode material of the above-mentioned embodiment contains positive electrode material and self-repairing microcapsules, that is, does not contain lithium replenishing material, the positive electrode active material does not contain lithium replenishing material; when the composite positive electrode material of the above-mentioned embodiment contains positive electrode material, lithium replenishing material and self-repairing microcapsules, the positive electrode active material contains lithium replenishing material.

[0142] In an embodiment, when the positive electrode active material layer includes a lithium supplement material, the lithium supplement material may include the composite supplement material of the embodiment of the above application.

[0143] Since the positive electrode sheet of the battery of the embodiment of the present application contains the above-mentioned composite lithium supplement material or / and composite positive electrode material of the embodiment of the present application, the self-repairing microcapsules contained therein can be triggered to deform the wall material under predetermined conditions, thereby releasing the repair agent of the core material, and repairing the microcracks generated by the positive electrode material and / or lithium supplement agent particles in the positive electrode sheet during the charging and discharging process, so that the capacity of the positive electrode sheet of the embodiment of the present application can be fully utilized and the cycle performance is good. 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 supplement 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.

[0144] In the embodiment, the mass percentage of the lithium supplement material in the positive electrode active material layer can be 0.5% to 5%. When the lithium supplement material includes the composite lithium supplement material of the above application embodiment, the mass percentage of the composite lithium supplement material in the positive electrode active material layer can be 0.5% to 5%.

[0145] The positive electrode active material in the positive electrode active material layer may include the composite positive electrode 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 fluorinated vanadium phosphate, lithium titanate, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

[0146] In the embodiment, the content of the binder in the positive electrode active material layer can be 2wt%-4wt%. In a specific embodiment, the content of the binder can be 2wt%, 3wt%, 4wt% 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.

[0147] In the embodiment, the content of the conductive agent in the positive electrode active material layer can be 3wt%-5wt%. In a specific embodiment, the content of the binder can be 3wt%, 4wt%, 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.

[0148] In the embodiment, the preparation process of the positive electrode sheet can be: mixing the positive electrode active material, lithium supplement material, conductive agent and binder to obtain positive electrode slurry, coating the positive electrode slurry on the current collector, and preparing the positive electrode sheet through drying, rolling, die cutting and other steps.

[0149] In some other embodiments, a repair layer is stacked on the surface of the positive active material layer of the positive electrode sheet of the battery of the embodiment of the present application, that is, on the surface of the positive active material layer away from the positive current collector. The repair layer contains the self-repairing microcapsules in the composite lithium supplement material of the embodiment of the present application, specifically, the core material of the self-repairing microcapsules includes a repair agent, and the wall material of the self-repairing microcapsules includes at least one of a stress deformation material and an electrodeformable material.

[0150] By adding a repair layer on the surface of the positive electrode active material layer of the positive electrode sheet, it can also play the role of the self-repairing microcapsules in the composite lithium replenishing material of the above-mentioned application embodiment. For example, when the self-repairing microcapsule wall material reaches the deformation threshold value under stress or voltage or caused by voltage such as Joule heat, the self-repairing microcapsule wall material is deformed and ruptured, thereby releasing the repair agent in the core material. The released repair agent enters the positive electrode active material layer and contacts with the positive electrode material particles or the lithium replenishing agent particles, thereby repairing the defects such as microcracks of the positive electrode material particles or the lithium replenishing agent particles, thereby improving the cycle performance and capacity of the positive electrode sheet.

[0151] In the embodiment, the thickness of the repair layer can be 10 to 100 nm. The repair layer in this thickness range can effectively improve the compatibility with the positive electrode material or / and the lithium supplement agent in the positive electrode active material layer, and improve the capacity density of the positive electrode sheet while giving full play to the self-repairing microcapsules to repair the positive electrode material or / and the lithium supplement agent particles.

[0152] 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.

[0153] 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.

[0154] The composite lithium supplement material and its preparation method and battery of the present application are illustrated by multiple specific embodiments below.

[0155] 1. Composite positive electrode material and preparation method thereof Example:

[0156] Embodiment A1:

[0157] This embodiment provides a composite positive electrode material and a preparation method thereof. The composite positive electrode material includes lithium iron phosphate (LiFePO4) particles and Li5FeO4 particles, and the surfaces of the LiFePO4 particles and the Li5FeO4 particles are coated with a self-repairing layer, and the self-repairing layer includes a self-repairing microcapsule. Among them, the core material of the self-repairing microcapsule includes polyaniline, and the wall material includes polyurethane; the mass ratio of LiFePO4 to Li5FeO4 is 98:2.

[0158] The preparation method of the composite lithium supplement material of this embodiment comprises the following steps:

[0159] S1. Preparation of self-healing microcapsules:

[0160] S11. Preparation of polyaniline core material solution:

[0161] Preparation of polyaniline solution: Weigh an appropriate amount of polyaniline, dissolve it in dimethyl sulfoxide (DMSO), and stir it at 500 rpm for 1 hour using a stirrer to ensure the formation of a uniform polyaniline solution; the solution concentration is controlled within the range of 7wt% to ensure the formation of a uniform core structure; the polyaniline solution is ultrasonically treated for 10 minutes to ensure that the polyaniline particles are uniformly dispersed without obvious aggregated particles;

[0162] S12. Preparation of disulfide bond polyurethane wall material solution:

[0163] S121. Preparation of polyurethane solution: a polyurethane prepolymer containing disulfide bonds was dissolved in DMSO to a concentration of 13 wt %; a crosslinking agent, hexamethylene diisocyanate (HDI), was slowly added to control the degree of crosslinking, and stirred for 30 minutes to obtain a uniform prepolymer solution;

[0164] S122. Emulsification preparation: The polyurethane solution is added dropwise into deionized water and continuously stirred at 800 rpm to form a stable emulsion system; during this process, the emulsion temperature is controlled not to exceed 25° C. to avoid premature crosslinking;

[0165] S13. Preparation of microcapsule emulsion:

[0166] S131. Emulsion formation: slowly adding the polyaniline core material solution to the disulfide bond polyurethane wall material solution and stirring at 1000 rpm for 10 minutes to encapsulate the polyaniline core material in the polyurethane wall material;

[0167] S132. Preliminary crosslinking: During the stirring process of the emulsion, a crosslinking agent is gradually added to initially crosslink the polyurethane wall material and begin to form a microcapsule core-shell structure; the crosslinking process is maintained at room temperature for 30 minutes to ensure the uniformity and integrity of the microcapsule structure;

[0168] S14. Preparation of self-healing microcapsules by spray drying:

[0169] S141. Spray drying parameter settings:

[0170] Feed rate: adjusted to 1-2 mL / min;

[0171] Inlet temperature: set to 80-100°C to avoid thermal degradation of polyaniline and polyurethane;

[0172] Dry air flow rate: controlled at 20m 3 / h, ensuring the rapid drying and forming of microcapsules;

[0173] S142. Spray drying process:

[0174] The microcapsule emulsion is atomized by a spray dryer to form self-repairing microcapsules with a size of 500nm to 2μm; the self-repairing microcapsules after spray drying are collected and stored in a sealed container to avoid moisture and oxidation.

[0175] S2. Compounding of self-repairing microcapsules with positive electrode materials and lithium supplement materials:

[0176] S21. Electrostatic spraying method:

[0177] The self-healing microcapsules are dispersed in a low-volatile solvent such as isopropanol to form a uniform suspension. The suspension is evenly sprayed onto the surface of LiFePO4 particles and Li5FeO4 particles using an electrostatic spraying device to form a coating layer on the surface of the LiFePO4 particles and Li5FeO4 particles. During the spraying process, the voltage is controlled between 5 and 10 kV to ensure that the coating layer formed by the self-healing microcapsules is evenly distributed and stably attached to the surface of the particles.

[0178] S22. Drying treatment:

[0179] After spraying, the mixture was placed in a vacuum drying oven for 30 minutes with the temperature controlled at 40-50° C. to remove the solvent and obtain a composite positive electrode material.

[0180] The action mechanism of the composite positive electrode material of this embodiment is analyzed as follows:

[0181] a. Analysis of stress response characteristics and rupture conditions of the self-repairing microcapsules contained in the composite cathode material of this embodiment:

[0182] The stress response characteristics of self-healing microcapsules are mainly determined by the disulfide bond strength and cross-linking density of the wall material:

[0183] Tensile stress threshold: generally in the range of 2 to 5 MPa. When this stress is exceeded, the disulfide bond will break.

[0184] Compression stress threshold: The rupture threshold under compression is generally between 3 and 6 MPa. When the local stress accumulation exceeds this range, the self-healing microcapsules will rupture at these stress concentration points, thereby releasing the repair agent.

[0185] This stress-responsive design ensures that the self-healing microcapsules rupture preferentially at cracks or defects and release the repair agent, which can dynamically repair damage such as microcracks of the LiFePO4 particles and Li5FeO4 particles contained in the composite during battery use, thereby improving the structural stability and cycle performance of the composite positive electrode material and fully utilizing the capacity.

[0186] b. The self-repairing mechanism of the composite cathode material in this embodiment:

[0187] When the volume change of LiFePO4 particles and Li5FeO4 particles causes local stress to be transmitted to the wall material of the self-healing microcapsule, the disulfide bonds (SS bonds) in the wall material of the self-healing microcapsule are gradually stretched or compressed. Polyurethane materials containing disulfide bonds have high flexibility and reversibility within a certain range and can adapt to small stresses without breaking. However, when the stress exceeds the fracture threshold of the disulfide bond (generally in the range of 2 to 5 MPa), the disulfide bond will undergo bond exchange or dissociation, causing the wall material structure of the self-healing microcapsule to break.

[0188] When the wall material of the self-healing microcapsule is broken, the polyaniline repair agent inside will be released, enter the microcrack area of ​​the LiFePO4 particles and Li5FeO4 particles, and play the following roles:

[0189] Filling cracks: Polyaniline, as a repair agent, will fill the cracks on the electrode surface and play a physical supporting role.

[0190] Restore conductivity: Polyaniline has a certain conductivity and can restore the conductive path of LiFePO4 material, ensuring that the electrode maintains good electrochemical performance during the cycle;

[0191] Solidification and stabilization: Polyaniline gradually solidifies at the cracks or embeds into the surface of LiFePO4 to form a stable filling layer, thereby delaying the expansion of cracks and maintaining the integrity of the electrode structure.

[0192] Therefore, the composite positive electrode material in Example A1 can respond quickly when the LiFePO4 particles and Li5FeO4 particles are damaged, release the polyaniline repair agent, fill and repair the cracks of the LiFePO4 particles and Li5FeO4 particles, thereby improving the cycle life and capacity retention rate of the battery.

[0193] Through the above mechanism, the stress-responsive microcapsules on the surface of LiFePO4 particles and Li5FeO4 particles can respond quickly when the electrode is damaged, release polyaniline repair agent, fill and repair cracks, thereby improving the cycle life and capacity retention rate of the battery.

[0194] Embodiment A2:

[0195] This embodiment provides a composite positive electrode material and a preparation method thereof. The composite positive electrode material includes a high nickel ternary positive electrode (NCA, LiNi 0.8 Co 0.15 Al 0.05 O2) particles and Li6CoO4 particles, the surface of the NCA particles and the Li6CoO4 particles are coated with a self-repairing layer, and the self-repairing layer includes a self-repairing microcapsule. The core material of the self-repairing microcapsule includes polypyrrole, and the wall material includes polycarbonate-polyethylene glycol copolymer (PC-PEG, softening temperature is 50-60°C); the mass ratio of NCA to Li6CoO4 is 95:5.

[0196] The preparation method of the composite positive electrode material in this embodiment includes the following steps:

[0197] S1. Preparation of self-healing microcapsules:

[0198] S11. Preparation of polypyrrole core material solution:

[0199] A 10 wt% polypyrrole solution was prepared by dissolving polypyrrole powder in dimethyl sulfoxide (DMSO); stirring was performed at 500 rpm using a magnetic stirrer for 1 hour to ensure that the polypyrrole particles were evenly dispersed; and ultrasonic treatment was performed for 10 minutes to avoid aggregation and ensure a uniform solution;

[0200] S12. Preparation of PC-PEG wall material solution:

[0201] The polycarbonate-polyethylene glycol copolymer (PC-PEG) was dissolved in DMSO to prepare a 12 wt% solution; an appropriate amount of hexamethylene diisocyanate (HDI) was added as a cross-linking agent to control the cross-linking density; a magnetic stirrer was used to stir for 30 minutes to ensure the uniformity of the solution;

[0202] S13. Formation of microcapsule emulsion:

[0203] The polypyrrole core material solution was slowly dripped into the PC-PEG solution, and stirred at 1000 rpm for 10 minutes to ensure that the polypyrrole core material was evenly coated by the PC-PEG material; HDI was gradually added during the stirring process to promote the initial cross-linking of the PC-PEG material and form a stable core-shell structure; the room temperature was maintained for 30 minutes to complete the structural formation of the self-healing microcapsules;

[0204] S14. Preparation of self-healing microcapsules by spray drying:

[0205] S141. Set spray drying parameters:

[0206] Feed rate: 1-2 mL / min;

[0207] Inlet temperature: 80-100°C to avoid thermal degradation of polypyrrole;

[0208] Dry air flow rate: 20m 3 / h, ensuring rapid prototyping of self-repairing microcapsules;

[0209] S142. Spray drying process: atomizing the self-repairing microcapsule emulsion through a spray dryer to form self-repairing microcapsules with a size of 500 nm to 2 μm; collecting the dried self-repairing microcapsules and sealing them to prevent moisture and oxidation;

[0210] S2. Compounding of self-repairing microcapsules and positive electrode materials:

[0211] The prepared self-repairing microcapsules are mixed with Li6CoO4 particles and NCA particles by a solution dispersion method and dried, and coating layers containing the self-repairing microcapsules are formed on the surfaces of the Li6CoO4 particles and the NCA particles, respectively, to obtain a composite positive electrode material.

[0212] The action mechanism of the composite positive electrode material of this embodiment is analyzed as follows:

[0213] a. Analysis of stress response characteristics and rupture conditions of the self-repairing microcapsules contained in the composite cathode material of this embodiment:

[0214] The wall material of the self-healing microcapsule contains polycarbonate-polyethylene glycol copolymer (PC-PEG), and the core material contains polypyrrole (PPy) healing agent. The Joule heat effect is used to trigger the rupture of the wall material of the self-healing microcapsule.

[0215] b. The self-repairing mechanism of the composite cathode material in this embodiment:

[0216] Since the working voltage of NCA in the composite positive electrode material can reach 4.5V; the decomposition voltage of Li6CoO4 is 4.2V, it is suitable for stably releasing lithium ions under high-voltage conditions such as in the range of 4.4 to 4.5V.

[0217] During the charge and discharge process of the battery cell, when the battery cell voltage reaches 4.4-4.5V, the high voltage causes the Joule heating effect on the surface of the NCA electrode, causing the surface temperature of the self-healing microcapsules to rise to above 50°C. When the temperature exceeds the softening threshold of PC-PEG (about 50-60°C), the wall material of the self-healing microcapsules softens and ruptures, releasing the polypyrrole repair agent.

[0218] Embodiment A3:

[0219] This embodiment provides a composite lithium supplement material and a preparation method thereof. The composite lithium supplement material is different from that of embodiment A1 in that the wall material of the self-repairing microcapsule is replaced by polydimethylsiloxane (PDMS) instead of polyurethane, and contains only Li5Fe O 4 (LFO) lithium supplement material, does not contain LiFePO4 (LFP). Other differences are shown in Table 1.

[0220] Compared with Example A1, in S2, LFP particles are not added for spray drying. Instead, the composite lithium supplement material obtained by coating the self-repairing microcapsules with mixed LFO is slurried and coated with the positive electrode slurry during the subsequent preparation of the electrode sheet.

[0221] Embodiment A4:

[0222] This embodiment provides a composite lithium supplement material and a preparation method thereof. Compared with the composite lithium supplement material in Example A2, the difference is that the wall material of the self-healing microcapsule is replaced by polycaprolactone (PCL) instead of PC-PEG. And it only contains Li6CoO4 (LCO) lithium supplement material, and does not contain NCA. Other differences are shown in Table 1.

[0223] Compared with Example A2, in S2, NCA particles are not added for spray drying. Instead, the composite lithium supplement material after self-repairing microcapsules are coated with mixed LCO and then slurried with the positive electrode slurry during the subsequent preparation of the pole piece.

[0224] Embodiment A5:

[0225] This embodiment provides a composite lithium supplement material and a preparation method thereof. Compared with the embodiment A1, the composite lithium supplement material only contains LNO lithium supplement material, and the core material of the self-healing microcapsule includes LNO. Other differences are shown in Table 1.

[0226] Compared with Example A1, in S2, LFP particles are not added for spray drying. Instead, the composite lithium supplement material after self-repairing microcapsules are coated with mixed LNO and then slurried with the positive electrode slurry during the subsequent preparation of the electrode sheet.

[0227] Embodiment A6:

[0228] This embodiment provides a composite lithium supplement material and a preparation method thereof. Compared with the composite lithium supplement material of embodiment A3, the mass ratio of the self-healing microcapsule to the lithium supplement material is 0.3:1. Other differences are shown in Table 1.

[0229] Comparative Example A1:

[0230] This comparative example provides a lithium supplement material. LFO is directly used as a lithium supplement agent; when preparing the electrode sheet later, it is slurried with LFP positive electrode slurry and coated together.

[0231] Comparative Example A2:

[0232] This comparative example provides a lithium supplement material. LCO is directly used as a lithium supplement agent; when preparing the electrode sheet later, it is slurried with NCA positive electrode slurry and coated together.

[0233] The relevant characterization data of the composite positive electrode material or composite lithium supplement material in the above-mentioned embodiments and comparative examples are shown in Table 1 below. The lithium-containing material in Table 1 refers to the positive electrode material or the positive electrode material and the lithium supplement material. In addition, the scanning electron microscope (SEM) photo of the composite positive electrode material in Example A1 is shown in Figure 2 The SEM photographs of the composite positive electrode materials in Examples A2 to A6 are similar to the SEM photograph of the composite positive electrode material in Example A1, and both have a micro-particle layer structure formed on the surface of the lithium-containing material.

[0234] Table 1

[0235]

[0236] 2. Lithium-ion battery example:

[0237] The present embodiment B1 to embodiment B6 and comparative examples B1 to comparative examples B2 provide a lithium ion battery respectively. Each lithium ion battery is assembled into a lithium ion battery according to the following method:

[0238] 1) Positive electrode:

[0239] The composite positive electrode materials provided in Examples A1 and A2 are respectively used as positive electrode materials in Examples B1 and B2 of lithium ion batteries. Under the same conditions, the composite positive electrode material: Su-P conductive agent: PVDF binder are mixed in an appropriate amount of NMP in a mass ratio of 91:4:5 to prepare positive electrode slurry.

[0240] The composite lithium supplement materials provided in Examples A3 to A6 and Comparative Example A1 were used as lithium supplement materials in Examples B3 to B6 and Comparative Example B1 of lithium ion batteries, respectively, and LFP positive electrode materials were used to prepare positive electrode slurries according to the following methods:

[0241] Under the same conditions, the positive electrode material: the composite lithium supplement material: the Su-P conductive agent: the PVDF binder are mixed in an appropriate amount of NMP in a mass ratio of 89.18:1.82:4:5 to prepare a positive electrode slurry; wherein, in each positive electrode slurry, the mass ratio of the positive electrode material to the composite lithium supplement material is 98:2, the total mass of the two is 91, and the positive electrode material in Examples B3 to B6 and Comparative Example B1 is LFP (the ratio of the positive electrode material to the lithium supplement material and the type of the positive electrode material are the same as those in Example B1);

[0242] The composite lithium supplement material provided in Comparative Example A2 is used as the lithium supplement material of the lithium ion battery Comparative Example B2, and the positive electrode slurry is prepared with the NCA positive electrode material according to the following method:

[0243] Under the same conditions, the positive electrode material: the composite lithium supplement material: the Su-P conductive agent: the PVDF binder were mixed in an appropriate amount of NMP in a mass ratio of 86.45:4.55:4:5 to prepare a positive electrode slurry; wherein the mass ratio of the positive electrode material to the composite lithium supplement material in the positive electrode slurry was 95:5, and the total mass of the two was 91, and the positive electrode material in the comparative example B2 was NCA (the ratio of the positive electrode material to the lithium supplement material and the type of the positive electrode material were the same as those in the embodiment B2);

[0244] The positive electrode slurries prepared in Examples B1 to B6 and Comparative Examples B1 to B2 were subjected to homogenization-coating-drying-cutting operations to prepare positive electrode sheets, which were baked in a vacuum oven at 100° C. to remove trace water.

[0245] 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.

[0246] 3) Diaphragm: Use polyethylene (PE) diaphragm.

[0247] 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.

[0248] 5) Assembly of secondary batteries:

[0249] 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.

[0250] Related performance testing of lithium-ion batteries:

[0251] 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.

[0252] Among them, the relevant performance test methods in Table 2 are as follows:

[0253] The first reversible specific capacity detection method of lithium-ion battery cells: charge the battery at a current of 0.1C in the voltage range of 2.0V to 4.5V at a constant temperature of 25°C until the voltage reaches 4.5V, and then charge the battery at a constant voltage of 4.5V until the current reaches 0.01C, and record the capacity as C1; let the battery stand for 5 minutes, and then discharge the battery at a current of 0.1C until the voltage reaches 2.0V, and record the capacity of the lithium-ion battery when the discharge rate is 0.1C as D1; ​​the first cycle coulomb efficiency is calculated as: first coulomb efficiency = D1 / C1, where D1 is the first reversible specific capacity.

[0254] Capacity retention rate detection method of lithium-ion battery cells: perform the first charge and discharge cycle at a constant temperature of 25°C, charge the battery at a constant current of 1C (the current at which the nominal capacity of the battery is fully discharged within 2 hours) until the voltage reaches the upper limit of 4.5V, then charge at a constant voltage until the current reaches 0.05C, let the battery stand for 5 minutes, then discharge the battery at a constant current of 1C until the voltage finally reaches 2.0V and record the first cycle discharge capacity; then, repeat the charge and discharge cycles continuously; calculate the capacity retention rate of the fully charged battery cycled at 25°C at the end of the 2000th cycle, that is, 2000-cycle capacity retention rate = (2000th-cycle discharge capacity / first-cycle discharge capacity) × 100%.

[0255] Table 2

[0256]

[0257] Combined with Table 1 above, it can be seen from the test results in Table 2 that:

[0258] (1) By comparing Example B1 and Comparative Example B1, it can be seen that the self-repairing microcapsules in Example B1 dynamically repair cracks by releasing repair agents during the cycle, which significantly improves the cycle stability.

[0259] (1.1) Data comparison and improvement effect:

[0260] Compared with comparative example B1, the capacity retention rate of Example B1 after 500 cycles increased by 6.4%, from 90.7% of the comparative example to 98.1%. In a longer cycle test (2000 cycles), the capacity retention rate of Example B1 was further increased by 11.2%, showing excellent long-cycle stability. At the same time, the first reversible specific capacity and first coulombic efficiency of Example B1 were significantly improved.

[0261] After 500 cycles, the battery cells in Example B1 and Comparative Example B1 were disassembled, wherein the positive electrode sheet in Example B1 was Figure 3 As shown, the positive electrode sheet in Comparative Example B1 is as Figure 4 As shown. Figure 3 and Figure 4 It can be seen that after 500 cycles, the positive electrode sheet in Example B1 has no obvious cracks, while the positive electrode sheet in Comparative Example B1 has obvious cracks after 500 cycles. This shows that the lithium-containing material in Example A1 exhibits excellent structural stability, giving the positive electrode sheet good cycle stability.

[0262] (1.2) Technical advantages and mechanism analysis:

[0263] The self-healing microcapsules dynamically release the repair agent during multiple charge and discharge cycles of the electrode material through the crack repair network embedded in the active material. When microcracks initiate during the cycle, the repair agent fills the cracks, thereby preventing the cracks from expanding and causing structural damage.

[0264] In addition, the viscoelasticity and conductivity of the repair agent further optimize the mechanical stability and electronic conductivity of the electrode material, fundamentally reducing the capacity attenuation caused by the disintegration of the electrode structure.

[0265] (1.3) Summary of differences from Comparative Example B1:

[0266] In Comparative Example B1, due to the lack of a dynamic repair mechanism, cracks continued to expand during the cycle, eventually leading to pulverization of the electrode particles and breakage of the conductive network, which manifested as a rapid decrease in capacity retention.

[0267] (2) By comparing Example B2 and Comparative Example B2, it can be seen that in the compound application with the ternary material, the self-healing microcapsules of Example B2 not only improve the initial charge and discharge efficiency, but also significantly enhance the cycle stability.

[0268] (2.1) Improvement of initial charge and discharge performance:

[0269] Data comparison: Compared with comparative example B2, the first coulombic efficiency of embodiment B2 increased by 3%, from 91% of the comparative example to 94%, showing a higher initial efficiency.

[0270] Technical mechanism: The self-healing microcapsules release the repair agent during the first charge and discharge process, and combine with the surface of the active material to form a flexible protective layer. This protective layer effectively reduces the exposure of the side reaction area on the electrode surface, reduces the excessive formation of SEI film, and limits the irreversible lithium loss.

[0271] Since the electrode material of Comparative Example B2 lacks a protective layer, the surface exposure area of ​​the active material is large, and the excessive generation of SEI film leads to a large consumption of lithium ions, thereby reducing the initial efficiency.

[0272] (2.2) Improvement of reversible capacity:

[0273] Data comparison: The reversible capacity of Example B2 is increased by 9 mAh / g compared with the comparative example, from 198 mAh / g to 207 mAh / g.

[0274] Technical mechanism: The flexible protective layer not only reduces the lithium consumption in the side reaction area, but also optimizes the interface stability of the ternary material and maximizes the utilization of its reversible capacity.

[0275] (2.3) Improvement of long cycle performance:

[0276] Data comparison: In the 2000-cycle test, the capacity retention rate of Example B2 was increased by 12.6% compared with the control example, from 82.3% of the control example to 94.9%, reflecting excellent cycle stability.

[0277] Technical mechanism: During the cycle, the microcapsules dynamically release the repair agent to repair the cracks caused by cyclic stress and volume expansion, thereby maintaining the integrity of the conductive network and the stability of the electrode structure. This dynamic repair mechanism effectively delays capacity decay.

[0278] Summary comparison: The performance degradation of comparative example B2 mainly comes from the intensified side reactions between the ternary material and the electrolyte, crack expansion and interface failure during high-rate cycling. The self-healing microcapsules of Example B2 significantly improved the interface stability and material cycle performance through a dual mechanism (flexible protective layer + dynamic crack repair).

[0279] In addition, by comparing Examples B1, B3, B6 and other Examples, it can be seen that appropriately improving the self-repairing microcapsules can increase the capacity retention rate of lithium-ion battery cells and improve the cycle performance of lithium-ion battery cells.

[0280] (3) By comparing Examples B3 to B6 with Comparative Example B1, it can be seen that, under the premise of the same positive electrode material, the lithium supplement materials in Examples B3 to B6 all contain self-repairing microcapsules, and the first reversible specific capacity and capacity retention rate of the batteries in Examples B3 to B6 are also significantly improved compared with Comparative Example B1.

[0281] 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 supplement material, characterized in that: The invention comprises a lithium supplement material and a self-repairing microcapsule, wherein the core material of the self-repairing microcapsule comprises a repairing agent, and the wall material of the self-repairing microcapsule comprises at least one of a stress-deformation material and an electro-deformation material.

2. The composite lithium supplement material according to claim 1, characterized in that: The mass ratio of the self-repairing microcapsule to the lithium supplementing material is (0.05-0.3):1; and / or The self-repairing microcapsules and the lithium supplementing material form a mixture; and / or The self-repairing microcapsules are arranged on the surface of the particles of the lithium supplementing material and form a coating layer.

3. The composite lithium supplement material according to any one of claims 1 to 2, characterized in that: The self-repairing microcapsule comprises at least one of the following (1) to (7): (1) The thickness of the wall material is 2 to 20 nm; (2) The Dv50 particle size of the self-repairing microcapsule is 10 to 100 nm; (3) The stress-deformable material comprises at least one of a stress-sensitive polymer, a pressure-sensitive material, and a reversible dynamically cross-linked polymer; (4) The electrodeformation voltage of the electrodeformable material is 3.2 to 4.8 V; (5) The phase transition temperature of the electrodeformable material is 40°C≤T≤60°C and / or 60°C <T≤80℃; (6) The repair agent accounts for 50% to 90% of the mass of the self-repairing microcapsules; (7) The repair agent includes at least one of lithium conductive polymer, conductive polymer, metal oxide, and ion gel; (8) The core material also includes a lithium supplement.

4. The composite lithium supplement material according to claim 3, characterized in that: The stress-sensitive polymer includes at least one of polyurethane, polydimethylsiloxane, polyamide, and polyacrylate; and / or The pressure-sensitive material includes at least one of zinc oxide, silicon carbide, and barium titanate; and / or The reversible dynamically cross-linked polymer comprises at least one of a disulfide bond polyurethane, a boroxine dynamically cross-linked supramolecular thermosetting polymer, and a boroxane cross-linked supramolecular thermosetting polymer; and / or The electrodeformable material includes at least one of liquid crystal polymer, shape memory polymer, piezoelectric material, ionic liquid crystal polymer, and electroactive polymer.

5. A method for preparing a composite lithium supplement material, characterized in that: The steps include: The self-healing microcapsules are mixed with lithium supplement materials; Wherein, the core material of the self-repairing microcapsule includes a repairing agent, and the wall material of the self-repairing microcapsule includes at least one of a stress-deformation material and an electrodeformation material.

6. The preparation method according to claim 5, characterized in that: The method of mixing the self-healing microcapsules with the lithium supplementing material includes at least one of the following methods: dry mixing, coating, electrostatic spraying, and solution dispersion: The dry mixing method comprises the following steps: Dry-mixing the lithium supplement material and the self-repairing microcapsules according to a certain proportion to obtain a mixture; In a protective atmosphere, the mixture is subjected to high-speed stirring treatment so that at least a portion of the self-repairing microcapsules are combined with the surface of the lithium-replenishing material to obtain the composite lithium-replenishing material; The coating method comprises the following steps: Applying a first suspension containing the self-repairing microcapsules to the surface of particles of the lithium supplementing material to form a first wet film on the surface of particles of the lithium supplementing material; Drying the first wet film to remove the solvent to obtain the composite lithium supplement material; The electrostatic spraying method comprises the following steps: Spraying the second suspension of the self-repairing microcapsules on the surface of the particles of the lithium supplementing material to form a second wet film on the surface of the particles of the lithium supplementing material; Drying the second wet film to remove the solvent to obtain the composite lithium supplement material; The solution dispersion method comprises the following steps: Ultrasonic mixing of the lithium supplement material and the third suspension containing the self-repairing microcapsules to obtain a dispersed slurry; In a protective atmosphere, the dispersed slurry is continuously stirred and mixed to obtain a mixture slurry; The mixture slurry is dried to obtain the composite lithium supplement material.

7. A composite positive electrode material, comprising a positive electrode material or a positive electrode material and a lithium supplement material, and also comprising a self-repairing microcapsule, wherein the core material of the self-repairing microcapsule comprises a repairing agent, and the wall material of the self-repairing microcapsule comprises at least one of a stress-deformation material and an electrodeformation material.

8. The composite positive electrode material according to claim 7, characterized in that: The mass of the self-repairing microcapsule and the positive electrode material is (0.02-0.2):1; and / or The self-repairing microcapsules and the positive electrode material or the positive electrode material and the lithium supplement material form a mixture; and / or The self-repairing microcapsules are arranged on the surface of the positive electrode material or the particles of the positive electrode material and the lithium supplementing material to form a coating layer.

9. The composite positive electrode material according to claim 7 or 8, characterized in that: The self-repairing microcapsule comprises the positive electrode material and the lithium supplement material, wherein the positive electrode material comprises a lithium iron phosphate positive electrode material, the lithium supplement material comprises Li5FeO4, the wall material of the self-repairing microcapsule comprises an electrodeformable material, and the electrodeformable material comprises at least one of polyurethane, polycaprolactone, and polylactic acid; or The positive electrode material and the lithium supplement material are included, wherein the positive electrode material includes lithium iron manganese phosphate positive electrode material, the lithium supplement material includes Li6CoO4, the wall material of the self-repairing microcapsule includes an electrodeformable material, and the electrodeformable material includes an inorganic piezoelectric material; or The invention comprises the positive electrode material and the lithium supplement material, wherein the positive electrode material comprises a high-nickel ternary positive electrode material, the lithium supplement material comprises Li6CoO4, the wall material of the self-repairing microcapsule comprises an electrodeformable material, and the electrodeformable material comprises at least one of polypyrrole, polyhydroquinone terephthaloyl, polyphenylquinoline, polyaryletherimide, polymethyl methacrylate-based liquid crystal polymer, and polyparaphenylene-based liquid crystal material.

10. A battery comprising a positive electrode sheet, wherein the positive electrode sheet comprises 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 comprises the composite lithium supplement material according to any one of claims 1 to 4, or the composite lithium supplement material prepared by the preparation method according to any one of claims 5 to 6, or the composite positive electrode material according to any one of claims 7 to 9; Or / and, a repair layer is stacked on the surface of the positive electrode active material layer away from the positive electrode current collector, the repair layer includes self-repairing microcapsules, the core material of the self-repairing microcapsules includes a repairing agent, and the wall material of the self-repairing microcapsules includes at least one of a stress deformation material and an electrodeformable material.

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