Negative active material and preparation method thereof, negative pole piece, battery and power utilization device

Abstract

The invention relates to the technical field of batteries, in particular to a negative active material and a preparation method thereof, a negative pole piece, a battery and an electric device. The negative electrode active material includes: silicon particles having a hydroxyl group on the surface; the silane coupling agent is connected with hydroxyl groups on the surfaces of the silicon particles through Si-O-Si bonds, and the silane coupling agent has a benzene ring; the cationic polyamine polymer is connected with hydroxyl groups on the surfaces of the silicon particles through hydrogen bonds and Si-N bonds, the cationic polyamine polymer has a benzene ring, and the benzene ring of the cationic polyamine polymer is connected with the benzene ring of the silane coupling agent through a pi-pi stacking effect. According to the negative electrode active material provided by the invention, the bulk phase stability and inter-phase stability of the negative electrode active material are improved by modifying and introducing covalent interaction and non-covalent interaction on the surfaces of the silicon particles, the integrity of an electrode structure and the stability of an electrode and an electrolyte interface are kept in charging and discharging, side reactions are reduced, and the service life of the negative electrode active material is prolonged. And the cycling stability of the battery is improved.

Description

Technical Field

[0001] The present application relates to the technical field of batteries, and particularly to a negative electrode active material, a preparation method thereof, a negative electrode plate, a battery, and an electrical device. Background Art

[0002] Secondary batteries are widely used in fields such as consumer electronics, energy storage devices, and electric vehicles due to their high energy density, long cycle life, and low self-discharge rate.

[0003] Silicon-based negative electrode materials have great potential for improving energy density due to their excellent theoretical specific capacity (about 4200 mAh / g). However, silicon undergoes a large volume change (>300%) during charge and discharge, which can lead to mechanical degradation, accompanied by problems such as particle cracking and the inability to form a stable solid electrolyte interface layer (SEI) at the electrode / electrolyte interface, resulting in a direct loss of active capacity and an acceleration of harmful side reactions between the electrolyte and the newly exposed silicon surface, affecting the electrochemical performance of the battery. Moreover, the intrinsic conductivity of silicon is low, which limits its practical application.

[0004] In traditional technologies, a carbon layer is coated on the surface of silicon-based materials to inhibit the expansion of silicon-based materials, improve interface stability, and suppress side reactions.

[0005] However, in the face of the anisotropic expansion of silicon-based materials, the SEI film on the surface of the carbon coating layer is still prone to cracking. Summary of the Invention

[0006] Based on this, it is necessary to provide a negative electrode active material, a preparation method thereof, a negative electrode plate, a battery, and an electrical device, which can inhibit the expansion of silicon-based materials, improve interface stability, suppress side reactions, improve the mechanical stability of the materials, and thus improve the cycle performance of the battery.

[0007] In a first aspect of the present application, a negative electrode active material is provided. The negative electrode active material includes: silicon particles with hydroxyl groups on the surface; a silane coupling agent connected to the hydroxyl groups on the surface of the silicon particles through Si-O-Si bonds, and the silane coupling agent has a benzene ring; and a cationic polyamine polymer connected to the hydroxyl groups on the surface of the silicon particles through hydrogen bonds and Si-N bonds, the cationic polyamine polymer has a benzene ring, and the benzene ring of the cationic polyamine polymer is connected to the benzene ring of the silane coupling agent through π-π stacking interaction.

[0008] In some embodiments, the silicon particles are micron-sized silicon particles.

[0009] In some embodiments, the cationic polyamine polymer includes at least one of polyamide-amine grafted with a benzene ring, polyethyleneimine grafted with a benzene ring, and polylysine grafted with a benzene ring.

[0010] In some embodiments, the weight-average molecular weight of the cationic polyamine polymer is from 10,000 g / mol to 40,000 g / mol.

[0011] In some embodiments, the silane coupling agent includes at least one of phenyltrimethoxysilane, phenyliethoxysilane, and phenylvinyldimethoxysilane.

[0012] In some embodiments, the surface of the negative electrode active material has a solid electrolyte interface film, and the solid electrolyte interface film includes at least one of Li2S, Li2O, and LiF.

[0013] The second aspect of the present application provides a method for preparing a negative electrode active material, the preparation method including the following steps: S1. Provide silicon particles, a silane coupling agent, and a cationic polyamine polymer, wherein the silicon particles have hydroxyl groups, the silane coupling agent has a benzene ring, and the cationic polyamine polymer has a benzene ring; S2. Mix the silicon particles and the silane coupling agent and react so that the silane coupling agent is connected to the hydroxyl groups on the surface of the silicon particles through Si-O-Si bonds to obtain silane coupling agent-modified silicon particles; S3. Mix the silane coupling agent-modified silicon particles and the cationic polyamine polymer and react so that the cationic polyamine polymer is connected to the hydroxyl groups on the surface of the silicon particles through hydrogen bonds and Si-N bonds, and the benzene ring of the cationic polyamine is connected to the benzene ring of the silane coupling agent through π-π stacking to obtain the negative electrode active material.

[0014] In some embodiments, in step S2, the reaction temperature is 60°C to 90°C, and the time is 1 h to 3 h.

[0015] In some embodiments, after step S2, the preparation method further includes the following step: performing a first curing treatment on the silane coupling agent-modified silicon particles, the temperature of the first curing treatment being 130°C to 180°C, and the time being 60 min to 120 min.

[0016] In some embodiments, in step S3, the reaction temperature is 20°C to 30°C, and the time is 3 h to 6 h.

[0017] In some embodiments, after step S3, the preparation method further includes the following step: performing a second curing treatment on the negative electrode active material, the temperature of the second curing treatment being 50°C to 80°C, and the time being 90 min to 180 min.

[0018] The third aspect of the present application provides a negative electrode sheet, which includes the negative electrode active material provided in the first aspect above or the negative electrode active material prepared by the preparation method provided in the second aspect above.

[0019] The fourth aspect of the present application provides a battery, which includes the negative electrode sheet provided in the third aspect above.

[0020] The fifth aspect of the present application provides an electrical device, which includes the battery provided in the fourth aspect above.

[0021] Compared with the traditional technology, the present application has at least the following beneficial effects:

[0022] For the negative electrode active material provided by the present application, on the one hand, by introducing hydroxyl groups on the surface of silicon particles to form Si-O-Si bonds with silane coupling agents, cationic polyamine polymers bind to the hydroxyl groups on the surface of silicon particles through hydrogen bonds and Si-N bonds, and the benzene rings of silane coupling agents and cationic polyamine polymers are interconnected through π-π stacking, the binding force between silicon particles and surface modification components is enhanced. The Si-O-Si chemical bond and Si-N bond provide strong chemical anchoring through covalent interaction, while hydrogen bonds and π-π stacking further enhance the interfacial binding force through non-covalent interaction. These covalent and non-covalent interactions together improve the bulk stability of the negative electrode active material, significantly inhibiting the volume expansion and particle cracking of silicon particles during charge and discharge. At the same time, the strong interaction on the surface of silicon particles enhances its compatibility with the binder, improves the adhesion force inside the electrode, thereby enhancing the interphase stability of the negative electrode active material, maintaining the integrity of the electrode structure and the stability of the electrode-electrolyte interface during the expansion and contraction of silicon particles, reducing side reactions, and improving the cycle stability of the battery.

[0023] On the other hand, the cationic polyamine polymer is modified by a benzene ring and has a π-π stacking interaction with the benzene ring-modified silane coupling agent on the surface of silicon particles. Therefore, during the modification of silicon particles, the cationic polyamine polymer can self-assemble and adsorb on the surface of silicon particles, and its coating uniformity is good; during the subsequent formation process, due to the cationic polyamine polymer having multiple positive charges and the anions in the electrolyte carrying negative charges, the cationic polyamine polymer can selectively adsorb the anions in the electrolyte, thereby increasing the local concentration of anions on the negative electrode surface, and further promoting the participation of anions in the reaction on the electrode surface, forming a uniform and inorganic component-rich solid electrolyte interface film, which has high mechanical properties and fast Li + diffusion characteristics, which is beneficial to improving the stability of the solid electrolyte interface film, reducing side reactions of the battery, reducing capacity loss, and improving the rate performance and cycle stability of the battery. Description of the Drawings

[0024] Figure 1 It is a schematic structural diagram of the negative electrode active material in an embodiment of the present application.

[0025] Figure 2 It is a schematic flow diagram of the preparation method of the negative electrode active material in an embodiment of the present application.

[0026] Reference Signs

[0027] 1. Anode active material; 10. Silicon particles; 20. Silane coupling agent; 30. Cationic polyamine polymer. Detailed Embodiments

[0028] Reference will now be made in detail to embodiments of the present application, one or more examples of which are described below. Each example is provided by way of explanation and not limitation of the present application. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made to the present application without departing from the scope or spirit of the present application. For example, features illustrated or described as part of one embodiment can be used in another embodiment to yield a still further embodiment.

[0029] Accordingly, it is intended that the present application cover such modifications and variations that fall within the scope of the appended claims and their equivalents. Other objects, features, and aspects of the present application are disclosed in or are apparent from the following detailed description. Those of ordinary skill in the art should understand that this discussion is only a description of exemplary embodiments and is not intended to limit the broader aspects of the present application.

[0030] In the present application, among the technical features described in an open-ended manner, there are included closed technical solutions composed of the listed features, as well as open technical solutions containing the listed features.

[0031] In the present application, regarding numerical ranges, unless otherwise specified, the above numerical ranges are considered continuous and include the minimum and maximum values of the range, as well as each value between such minimum and maximum values. Further, when the range refers to integers, it includes each integer between the minimum and maximum values of the range. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0032] If there is no special indication, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

[0033] If there is no special indication, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

[0034] Unless otherwise specified, all steps of this application can be carried out sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) carried out sequentially, or may also include steps (b) and (a) carried out sequentially. For example, when it is mentioned that the method may further include step (c), it means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may also include steps (c), (a) and (b), etc.

[0035] Unless otherwise specified, the terms "comprising" and "including" mentioned in this application are open-ended and can also be closed-ended. For example, the "comprising" and "including" may mean that other components not listed may also be included or comprised, or may only include or comprise the listed components.

[0036] Unless otherwise specified, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) while B is true (or exists); or both A and B are true (or exist).

[0037] The first aspect of this application provides a negative electrode active material 1, as Figure 1 shown. The negative electrode active material 1 includes silicon particles 10, a silane coupling agent 20, and a cationic polyamine polymer 30. The surface of the silicon particles 10 has hydroxyl groups. The silane coupling agent 20 is connected to the hydroxyl groups on the surface of the silicon particles 10 through Si-O-Si bonds, and the silane coupling agent 20 has a benzene ring. The cationic polyamine polymer 30 is connected to the hydroxyl groups on the surface of the silicon particles 10 through hydrogen bonds and Si-N bonds. The cationic polyamine polymer 30 has a benzene ring, and the benzene ring of the cationic polyamine polymer 30 is connected to the benzene ring of the silane coupling agent 20 through π-π stacking interactions.

[0038] The negative electrode active material 1 provided by the present application, on the one hand, by introducing hydroxyl groups on the surface of silicon particles 10 to form Si-O-Si chemical bonds with silane coupling agents 20, cationic polyamine polymers 30 binding to the hydroxyl groups on the surface of silicon particles 10 through hydrogen bonds and Si-N bonds, and the benzene rings of silane coupling agents 20 and cationic polyamine polymers 30 being interconnected through π-π stacking interactions, enhances the binding force between silicon particles 10 and surface modification components. The Si-O-Si bond and Si-N bond provide firm chemical anchoring through covalent interactions, while hydrogen bonds and π-π stacking interactions further enhance the interfacial binding force through non-covalent interactions. These covalent and non-covalent interactions together improve the bulk stability of the negative electrode active material 1, significantly suppressing the volume expansion and particle cracking of silicon particles 10 during charge and discharge. At the same time, the strong interactions on the surface of silicon particles 10 enhance their compatibility with the binder, improving the adhesion force inside the electrode, thereby enhancing the interphase stability of the negative electrode active material 1, maintaining the integrity of the electrode structure and the stability of the electrode-electrolyte interface during the expansion and contraction of silicon particles 10, reducing side reactions, and improving the cycle stability of the battery.

[0039] On the other hand, the cationic polyamine polymer 30 is modified by a benzene ring and has a π-π stacking interaction with the benzene ring-modified silane coupling agent 20 on the surface of the silicon particles 10. Therefore, during the modification of the silicon particles 10, the cationic polyamine polymer 30 can self-assemble and adsorb on the surface of the silicon particles 10 with good coating uniformity; during the subsequent formation process, since the cationic polyamine polymer 30 has multiple positive charges and the anions in the electrolyte carry negative charges, the cationic polyamine polymer 30 can selectively adsorb the anions in the electrolyte, thereby increasing the local concentration of anions on the negative electrode surface, and further promoting the participation of anions in the reactions on the electrode surface, forming a uniform and inorganic component-rich solid electrolyte interface film, which has high mechanical properties and fast Li + diffusion characteristics, which is beneficial to improving the stability of the solid electrolyte interface film, reducing side reactions of the battery, reducing capacity loss, and improving the rate performance and cycle stability of the battery.

[0040] It can be understood that since both the silane coupling agent 20 and the cationic polyamine polymer 30 have benzene rings, as the same aromatic rings, the matching degree of the π-π stacking interaction between the benzene rings is high, and the π electron clouds form a tight non-covalent interaction during the stacking process.

[0041] In some of these embodiments, the silicon particles 10 are micron-sized silicon particles 10. Thus, the micron-sized silicon particles 10 have a high tap density and a low preparation cost, improving the volumetric energy density of the electrode and reducing the cost. At the same time, through the formation of Si-O-Si bonds between the hydroxyl groups on the surface of the micron-sized silicon particles 10 and the silane coupling agent 20, the formation of hydrogen bonds and Si-N bonds with the cationic polyamine polymer 30, and the π-π stacking interaction between the benzene rings of both, the surface of the micron-sized silicon particles 10 is modified to improve the structural stability of the material, inhibit volume expansion, and improve the cycling performance of the battery.

[0042] In this article, the "micron-sized silicon particles 10" refer to silicon particles 10 with a particle size range of 1 μm to 10 μm.

[0043] In this article, the "cationic polyamine polymer 30" refers to a polymer containing multiple amine groups (primary amine, secondary amine, tertiary amine or quaternary ammonium group) and modified by benzene rings. It forms a positive charge through protonation or quaternization of the amine groups in solution, can bind to the hydroxyl groups on the surface of the silicon particles 10 through hydrogen bonds and Si-N bonds, and forms a π-π stacking interaction through the benzene ring with the benzene ring of the silane coupling agent 20.

[0044] It can be understood that the benzene rings in the cationic polyamine polymer 30 can be introduced by grafting, copolymerization, or cross-linking.

[0045] In some of these embodiments, the cationic polyamine polymer 30 includes at least one of polyamide-amine grafted with benzene rings, polyethyleneimine grafted with benzene rings, and polylysine grafted with benzene rings.

[0046] In some of these embodiments, the weight-average molecular weight of the cationic polyamine polymer 30 is from 10,000 g / mol to 40,000 g / mol. Exemplarily, the weight-average molecular weight of the cationic polyamine polymer 30 can be, but is not limited to, 10,000 g / mol, 15,000 g / mol, 20,000 g / mol, 25,000 g / mol, 30,000 g / mol, 35,000 g / mol, 40,000 g / mol. Thus, with the weight-average molecular weight of the cationic polyamine polymer within a suitable range, the cationic polyamine polymer has a moderate molecular chain length, which not only provides sufficient amine sites to form Si-N bonds with the hydroxyl groups on the surface of the silicon particles through hydrogen bonding and high-temperature reactions, enhancing the interfacial chemical bonding force, but also realizes the π-π stacking effect with the benzene ring of the silane coupling agent through the benzene ring, forming a flexible and uniform coating layer; at the same time, this molecular weight range ensures that the polymer has good solubility and self-assembly ability, avoiding insufficient coating layer strength caused by low molecular weight or entanglement and agglomeration caused by high molecular weight, thereby improving the bulk stability and interphase stability of the negative electrode active material, significantly suppressing the volume expansion and particle cracking of the silicon particles during charge and discharge, reducing the side reactions between the electrolyte and the silicon surface, and enhancing the cycle performance and rate performance of the battery.

[0047] In some of these embodiments, the silane coupling agent 20 includes at least one of phenyltrimethoxysilane, phenyitriethoxysilane, and phenylvinyldimethoxysilane.

[0048] In some of these embodiments, the surface of the negative electrode active material 1 has a solid electrolyte interface film, and the solid electrolyte interface film includes at least one of Li2S, Li2O, and LiF. Thus, by using the positive charge of the cationic polyamine polymer 30 to selectively adsorb anions in the electrolyte, the local concentration of anions on the negative electrode surface is increased, promoting the formation of an SEI film rich in inorganic components (such as Li2S, Li2O, LiF), and these inorganic components have high mechanical strength and excellent Li + conductivity, thereby improving the stability of the SEI film and the protection effect of the electrode interface, reducing side reactions, and enhancing the cycle performance and rate performance of the battery.

[0049] The second aspect of the present application provides a method for preparing a negative electrode active material, as Figure 2 shown, the preparation method includes the following steps:

[0050] S1. Provide silicon particles, a silane coupling agent, and a cationic polyamine polymer, wherein the silicon particles have hydroxyl groups, the silane coupling agent has a benzene ring, and the cationic polyamine polymer has a benzene ring.

[0051] S2. Mix the silicon particles and the silane coupling agent and react to make the silane coupling agent connect to the hydroxyl groups on the surface of the silicon particles through Si-O-Si bonds, thereby obtaining silane coupling agent-modified silicon particles.

[0052] S3. Mix the silane coupling agent-modified silicon particles and the cationic polyamine polymer and react to make the cationic polyamine polymer connect to the hydroxyl groups on the surface of the silicon particles through hydrogen bonds and Si-N bonds, and the benzene rings of the cationic polyamine are connected to the benzene rings of the silane coupling agent through π-π stacking interactions, thereby obtaining the negative electrode active material.

[0053] The preparation method of the negative electrode active material provided by this application first mixes and reacts the silicon particles with the silane coupling agent to form Si-O-Si bonds, and then mixes and reacts the silane coupling agent-modified silicon particles with the cationic polyamine polymer to form hydrogen bonds, Si-N bonds and π-π stacking interactions, realizing the modification and self-assembly coating of the surface of the silicon particles; in step S2, the alkoxy group of the silane coupling agent and the hydroxyl group on the surface of the silicon particles form a covalent Si-O-Si bond through a hydrolysis-condensation reaction, firmly anchoring the benzene ring; in step S3, the amino group of the cationic polyamine polymer binds to the hydroxyl group on the surface of the silicon particles through hydrogen bonds and Si-N bonds, and its benzene ring forms a non-covalent connection with the benzene ring of the silane coupling agent through π-π stacking interactions; by adopting a step-by-step modification method, the uniform distribution of covalent and non-covalent interactions is ensured, thereby improving the bulk phase stability of the negative electrode active material, significantly inhibiting the volume expansion and particle cracking of the silicon particles during charge and discharge, enhancing the stability of the electrode-electrolyte interface, reducing side reactions, and improving the cycle performance of the battery.

[0054] In some embodiments, in step S2, the reaction temperature is 60°C to 90°C and the time is 1 h to 3 h. Thus, by controlling the reaction temperature and reaction time of the silicon particles and the silane coupling agent in step S2, the formation efficiency of the Si-O-Si chemical bond and the uniformity of the modified layer are improved.

[0055] In some embodiments, after step S2, the preparation method further includes the following steps: performing a first curing treatment on the silane coupling agent-modified silicon particles, where the temperature of the first curing treatment is 130°C to 180°C and the time is 60 min to 120 min. Thus, the first curing treatment enables the silane coupling agent to form a more stable chemical bond with the surface of the silicon particles, improves the modification quality and mechanical stability of the surface of the silicon particles, reduces the peeling risk of the modified layer in subsequent processes, provides uniform reaction sites for the binding of the cationic polyamine polymer in step S3, and enhances the structural stability of the negative electrode active material.

[0056] In some embodiments, in step S3, the reaction temperature is 20°C to 30°C, and the reaction time is 3 to 6 hours. Thus, by controlling the reaction temperature and reaction time of the silane coupling agent-modified silicon particles and the cationic polyamine polymer in step S3, efficient formation of hydrogen bonds, Si-N bonds, and π-π stacking interactions, as well as uniform self-assembly of the coating layer, is achieved.

[0057] In some embodiments, after step S3, the preparation method further includes the following steps: performing a second curing treatment on the negative electrode active material, wherein the second curing treatment temperature is 50°C to 80°C and the duration is 90 minutes to 180 minutes. In this way, the second curing treatment promotes cross-linking and curing between the cationic polyamine polymer molecules, improving the stability and adhesion of the film. At the same time, the higher temperature of the second curing treatment provides sufficient energy to enhance the π-π stacking effect between the benzene rings, thereby improving the flexibility and uniformity of the cationic polyamine polymer coating layer, thereby further enhancing the bulk and interphase stability of the negative electrode active material, suppressing the volume expansion of silicon particles during the charge and discharge process, reducing side reactions, and improving the cycle performance of the battery.

[0058] The third aspect of the present application provides a negative electrode plate, which includes the negative electrode active material provided by the first aspect or the negative electrode active material prepared by the preparation method provided by the second aspect.

[0059] In some embodiments, the negative electrode active material further includes graphite.

[0060] In some embodiments, the negative electrode sheet, the negative electrode current collector and the negative electrode active material layer, the negative electrode active material layer is arranged on at least one side surface of the negative electrode current collector, and the negative electrode active material layer includes the negative electrode active material provided by the first aspect above or the negative electrode active material prepared by the preparation method provided by the second aspect above.

[0061] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymer substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0062] In some embodiments, the negative electrode active material layer may further include a binder. The binder may include at least one of styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), or carboxymethyl chitosan (CMCS).

[0063] In some embodiments, the negative electrode active material layer may further include a conductive agent. The conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers.

[0064] The fourth aspect of the present application provides a battery, which includes the negative electrode plate provided by the third aspect.

[0065] In some embodiments, the battery comprises a lithium ion battery, a sodium ion battery, or a potassium ion battery.

[0066] Typically, a battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0067] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer, the positive electrode active material layer is provided on at least one side of the positive electrode current collector, and the positive electrode active material layer includes a positive electrode active material.

[0068] As an example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material layer is provided on either or both of the two facing surfaces of the positive electrode current collector.

[0069] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0070] In some of these embodiments, the positive electrode active material layer may further include a positive electrode active material, which may be a positive electrode active material for a battery known in the art.

[0071] As an example, when the positive electrode sheet is used in a lithium-ion battery, the positive electrode active material may be a positive electrode active material for a lithium-ion battery known in the art. Further, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as the positive electrode active material of the battery may also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of the lithium transition metal oxide may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (which may also be abbreviated as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (which may also be abbreviated as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (which may also be abbreviated as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (which may also be abbreviated as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (which may also be abbreviated as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi 0.8 Co 0.15 Al 0.05 O2) or at least one of its modified compounds, etc. Examples of the lithium-containing phosphates with an olivine structure may include, but are not limited to, lithium iron phosphate (such as LiFePO4 (which may also be abbreviated as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and at least one of a composite material of lithium manganese iron phosphate and carbon.

[0072] In some of these embodiments, the positive electrode active material layer may also optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0073] In some of these embodiments, based on the total mass of the positive electrode active material layer, the mass percentage of the binder is 0.5% to 3%, such as 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, etc.

[0074] In some of these embodiments, the positive electrode active material layer may also optionally include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0075] In some of these embodiments, based on the total mass of the positive electrode active material layer, the mass percentage of the conductive agent is 0.8% to 4%, such as 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, etc.

[0076] In some of these embodiments, the positive electrode plate can be prepared by the following method: dispersing the above components for preparing the positive electrode plate, such as the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on the positive electrode current collector, and after processes such as drying and cold pressing, the positive electrode plate can be obtained.

[0077] This application has no specific limitation on the type of electrolyte, which can be selected according to requirements. For example, the electrolyte can be liquid, gel-like, or all-solid-state.

[0078] In some of these embodiments, the electrolyte uses an electrolytic solution. The electrolytic solution includes an electrolyte salt and a solvent.

[0079] In some of these embodiments, when the battery is a lithium-ion battery, the electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluoro(oxalato)borate, lithium bis(oxalato)borate, lithium difluoro(bis(oxalato))phosphate, and lithium tetrafluoro(oxalato)phosphate.

[0080] In some of these embodiments, the solvent may include at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, ethylene glycol dimethyl ether, methyl ethyl sulfone, and diethyl sulfone.

[0081] In some of these embodiments, the electrolyte may also optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve the overcharge performance of the battery, additives that improve the high-temperature or low-temperature performance of the battery, and the like.

[0082] This application does not particularly limit the type of separator, and any well-known porous structure separator with good chemical stability and mechanical stability can be selected.

[0083] In some of these embodiments, the material of the separator may include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, or polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0084] In some of these embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be made into an electrode assembly by a winding process or a stacking process.

[0085] In some of these embodiments, the battery cell may include an outer package. The outer package can be used to encapsulate the above-mentioned electrode assembly and electrolyte.

[0086] In some of these embodiments, the outer package of the battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the battery cell can also be a soft package, such as a pouch-type soft package. The material of the soft package can be plastic, and as the plastic, it can be polypropylene, polybutylene terephthalate, and polybutylene succinate, etc.

[0087] The fifth aspect of this application provides an electrical device, and this electrical device includes the battery provided in the fourth aspect above.

[0088] In some of these embodiments, the battery provided by the present application can be used as a power source for an electrical device or as an energy storage unit for an electrical device. The electrical device may include, but is not limited to, a mobile device, an electric vehicle, an electric train, a ship, a satellite, an energy storage system, etc. Among them, the mobile device may be, for example, a mobile phone, a laptop computer, etc.; the electric vehicle may be, for example, a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc., but is not limited to these.

[0089] The present application will be further described below in conjunction with specific examples and comparative examples.

[0090] Example 1

[0091] Negative electrode active material:

[0092] (1) Silicon particles, a silane coupling agent, and a cationic polyamine polymer are provided. Among them, the silicon particles are micron-sized silicon particles with a particle size of 4.3 μm, and the surface of the silicon particles has hydroxyl groups; the silane coupling agent is phenyltriethoxysilane (PhSi(OEt)3); the cationic polyamine polymer is a polyamide-amine grafted with a benzene ring, with a weight average molecular weight of 11669, and the chemical structural formula of the polyamide-amine grafted with a benzene ring is:

[0093] ;

[0094] The polyamide-amine grafted with a benzene ring is prepared by the following steps:

[0095] Dissolve 0.5 g of phenol in 100 ml of DMF to obtain a phenol solution, dissolve 0.5 g of polyamide-amine in 255 ml of DMF to obtain a polyamide-amine solution with a mass fraction of 0.21%, then mix the phenol solution with the polyamide-amine solution, and then add 0.03 g of boron trifluoride diethyl ether as a catalyst to the mixed solution. React for 12 hours under a nitrogen atmosphere at 80 °C, and then pour the reaction mixture into a large amount of precipitant acetone. While removing unreacted phenol, catalyst, and other impurities, precipitate the product. Then place the product in a vacuum drying oven and dry it to constant weight at 60 °C to remove residual solvent and moisture.

[0096] (2) Dissolve the silane coupling agent phenyltriethoxysilane (PhSi(OEt)3) in an appropriate solvent ethanol to prepare a silane coupling agent solution with a mass fraction of 0.5%; then directly immerse the silicon particles in the silane coupling agent solution, with a reaction temperature of 70 °C and a time of 2 h, and then dry at room temperature for 30 min to obtain silane coupling agent-modified silicon particles.

[0097] (3) Perform a first curing treatment on the silane coupling agent-modified silicon particles at 150 °C for 90 min.

[0098] (4) Dissolve the polyamide - amine grafted with benzene rings in deionized water to prepare a polyamide - amine solution grafted with benzene rings with a mass fraction concentration of 1%; Immerse the silane coupling agent - modified silicon particles into the polyamide - amine solution modified with benzene rings, with a reaction temperature of 25 °C and a time of 4 h, so that the polyamide - amine molecules grafted with benzene rings are adsorbed and self - assembled on the surface of the silicon powder, then centrifuge to collect the lower - layer powder, and finally rinse it with deionized water multiple times to obtain the negative electrode active material.

[0099] (5) Perform a second curing treatment on the negative electrode active material at 60 °C for 120 min.

[0100] Negative electrode plate:

[0101] The negative electrode plate includes a negative electrode current collector copper foil and a negative electrode active material layer. The negative electrode active material layer (the mass ratio of the negative electrode active material, graphite, conductive carbon black, and PAA is 19:75:1:5) is provided on one side of the negative electrode current collector, and the negative electrode active material layer includes the above - mentioned negative electrode active material.

[0102] Battery:

[0103] The battery includes a positive electrode plate made of lithium iron phosphate (the mass ratio of lithium nickel cobalt manganese oxide NCM811, PVDF, conductive carbon black, and carbon nanotubes is 97.2:1.8:0.5:0.5), the above - mentioned negative electrode plate, an electrolyte solution (the electrolyte is 1.0 M LiPF6, the solvent is EC / DEC with a volume ratio of 1:1 and 5% fluoroethyl carbonate FEC by volume), and a PE separator.

[0104] Example 2

[0105] In this example, the preparation methods of the negative electrode active material, negative electrode plate, and battery are basically the same as those in Example 1, except that:

[0106] The cationic polyamine polymer is polyethyleneimine grafted with benzene rings, with a weight - average molecular weight of 26560. The chemical structural formula of the polyethyleneimine grafted with benzene rings is:

[0107] ;

[0108] The polyethyleneimine grafted with benzene rings is prepared by the following steps:

[0109] Dissolve 0.5 g of phenol in 100 ml of DMF to obtain a phenol solution. Dissolve 0.2 g of polyethyleneimine in 255 ml of isopropanol to obtain a polyethyleneimine solution with a mass fraction of 0.1%. Then mix the phenol solution and the polyethyleneimine solution, and add 0.03 g of boron trifluoride diethyl ether as a catalyst to the mixed solution. After reacting for 12 hours under a nitrogen atmosphere at 80 °C, pour the reaction mixture into a large amount of precipitant acetone to precipitate the product while removing unreacted phenol, catalyst, and other impurities. Then place the product in a vacuum drying oven and dry it to a constant weight at 60 °C to remove residual solvent and moisture.

[0110] Example 3

[0111] In this example, the preparation methods of the negative electrode active material, negative electrode sheet, and battery are basically the same as those in Example 1, except that:

[0112] The cationic polyamine polymer is polylysine grafted with a benzene ring, with a weight average molecular weight of 31,560. The chemical structural formula of polylysine grafted with a benzene ring is:

[0113] ;

[0114] Polylysine grafted with a benzoyl group is prepared by the following steps:

[0115] Dissolve 0.5 g of phenol in 100 ml of DMF to obtain a phenol solution. Dissolve 0.17 g of polylysine in 255 ml of deionized water to obtain a polylysine solution with a mass fraction of 0.085%. Then mix the phenol solution and the polylysine solution, and add 0.03 g of boron trifluoride diethyl ether as a catalyst to the mixed solution. After reacting for 12 hours under a nitrogen atmosphere at 80 °C, pour the reaction mixture into a large amount of precipitant acetone to precipitate the product while removing unreacted phenol, catalyst, and other impurities. Then place the product in a vacuum drying oven and dry it to a constant weight at 60 °C to remove residual solvent and moisture.

[0116] Example 4

[0117] In this example, the preparation methods of the negative electrode active material, negative electrode sheet, and battery are basically the same as those in Example 1, except that:

[0118] Step (3) is omitted.

[0119] Example 5

[0120] In this example, the preparation methods of the negative electrode active material, negative electrode sheet, and battery are basically the same as those in Example 1, except that:

[0121] Step (5) is omitted.

[0122] Comparative Example 1

[0123] Negative electrode active material:

[0124] Silicon particles, the same as the silicon particles provided in step (1) of Example 1.

[0125] Negative electrode sheet:

[0126] The negative electrode sheet includes a negative electrode current collector copper foil and a negative electrode active material layer. The negative electrode active material layer (the mass ratio of the negative electrode active material, graphite, conductive carbon black, and PAA is 19:75:1:5) is provided on one side of the negative electrode current collector, and the negative electrode active material layer includes the above-mentioned negative electrode active material.

[0127] Battery:

[0128] The battery includes a positive electrode sheet made of lithium iron phosphate (the mass ratio of nickel cobalt manganese oxide NCM811, PVDF, conductive carbon black, and carbon nanotubes is 97.2:1.8:0.5:0.5), the above-mentioned negative electrode sheet, an electrolyte solution (the electrolyte is 1.0 M LiPF6, the solvent is EC / DEC with a volume ratio of 1:1 and 5% fluoroethylene carbonate FEC by volume), and a PE separator.

[0129] Comparative Example 2

[0130] Negative electrode active material:

[0131] (1) Provide silicon particles, a silane coupling agent, and a cationic polyamine polymer. Among them, the silicon particles are micron-sized silicon particles with a particle size of 4.3 μm, and the surface of the silicon particles has hydroxyl groups; the silane coupling agent is triethoxysilane; the cationic polyamine polymer is polyamide-amine with a weight average molecular weight of 10109.

[0132] (2) Dissolve the silane coupling agent triethoxysilane in an appropriate solvent ethanol to prepare a silane coupling agent solution with a mass fraction of 0.5%; then directly immerse the silicon particles into the silane coupling agent solution, the reaction temperature is 70 °C, the time is 2 h, and then dry at room temperature for 30 min to obtain silane coupling agent-modified silicon particles.

[0133] (3) Perform the first curing treatment on the silane coupling agent-modified silicon particles at 150 °C for 90 min.

[0134] (4) Dissolve polyamide-amine in deionized water to prepare a polyamide-amine solution with a concentration of 1% by mass fraction; immerse the silane coupling agent-modified silicon particles into the polyamide-amine solution, the reaction temperature is 25 °C, the time is 4 h, so that polyamide-amine molecules form a coating on the surface of the silicon powder, then centrifuge to collect the lower-layer powder, and finally rinse with deionized water multiple times to obtain the negative electrode active material.

[0135] (5) The negative electrode active material is subjected to a second curing treatment at 60 °C for 120 min.

[0136] Negative electrode plate:

[0137] The negative electrode plate includes a negative electrode current collector copper foil and a negative electrode active material layer. The negative electrode active material layer (the mass ratio of negative electrode active material, graphite, conductive carbon black, and PAA is 19:75:1:5) is provided on one side of the negative electrode current collector, and the negative electrode active material layer includes the above-mentioned negative electrode active material.

[0138] Battery:

[0139] The battery includes a positive electrode plate made of lithium iron phosphate (the mass ratio of lithium nickel cobalt manganese oxide NCM811, PVDF, conductive carbon black, and carbon nanotubes is 97.2:1.8:0.5:0.5), the above-mentioned negative electrode plate, an electrolyte solution (the electrolyte is 1.0 M LiPF6, the solvent is EC / DEC with a volume ratio of 1:1 and 5% fluoroethyl carbonate FEC by volume), and a PE separator

[0140] Comparative Example 3

[0141] In this comparative example, the preparation methods of the negative electrode active material, the negative electrode plate, and the battery are basically the same as those in Example 1, except that:

[0142] The silane coupling agent is 1-naphthyltrimethoxysilane.

[0143] Negative electrode plate:

[0144] The negative electrode plate includes a negative electrode current collector copper foil and a negative electrode active material layer. The negative electrode active material layer (the mass ratio of negative electrode active material, graphite, conductive carbon black, and PAA is 19:75:1:5) is provided on one side of the negative electrode current collector, and the negative electrode active material layer includes the above-mentioned negative electrode active material.

[0145] Battery:

[0146] The battery includes a positive electrode plate made of lithium iron phosphate (the mass ratio of lithium nickel cobalt manganese oxide NCM811, PVDF, conductive carbon black, and carbon nanotubes is 97.2:1.8:0.5:0.5), the above-mentioned negative electrode plate, an electrolyte solution (the electrolyte is 1.0 M LiPF6, the solvent is EC / DEC with a volume ratio of 1:1 and 5% fluoroethyl carbonate FEC by volume), and a PE separator.

[0147] Performance test

[0148] (1) Test of the expansion rate of the electrode plate

[0149] The batteries of the above-mentioned examples and comparative examples were charged at a constant current of 0.33C to the rated charging voltage of 4.2V, and then charged at a constant voltage until the current was 0.05C. After disassembly, the negative electrode swelling rate was tested, where the negative electrode swelling rate = (full electrode sheet thickness - rolled electrode sheet thickness) / (rolled electrode sheet thickness - foil thickness). The test results are shown in Table 1.

[0150] (2)Cycle life test

[0151] The batteries prepared from the above-mentioned examples and comparative examples were charged at a constant current of 1C to the rated charging voltage, and then charged at a constant voltage until the current was 0.05C. After standing for 10 min, they were discharged at a constant current of 1C to the rated discharging voltage, and their initial capacity C0 was recorded; then they were charged at a constant current of 1C0 to the rated charging voltage, and then charged at a constant voltage until the current was 0.05C. After standing for 10 min, they were discharged at 1C0, and the discharging capacity C of each cycle was recorded. n , until the cycle capacity retention rate (C n / C0×100%) was 80%, and the number of cycles was recorded. The test results are shown in Table 1.

[0152] Table 1

[0153]

[0154] As can be seen from Table 1 by comparing Examples 1-5 and Comparative Examples 1-3, the negative electrode active material provided by the present application reduces the swelling rate of the negative electrode sheet and improves the cycle performance of the battery.

[0155] By comparing Examples 1-5 and Comparative Example 3, it can be seen that the negative electrode active material, silane coupling agent and cationic polyamine polymer provided by the present application all have benzene rings. Due to the high matching degree of the benzene ring structure, their π electron clouds can form tight non-covalent interactions during the stacking process. In addition, the steric hindrance of the benzene ring is small, which is conducive to the uniform self-assembly coating of the cationic polyamine polymer to form a dense surface modification layer, thereby effectively dispersing the mechanical stress generated by the volume expansion of silicon particles, reducing the swelling rate of the electrode sheet, and improving the cycle performance of the battery. In Comparative Example 3, the aromatic ring in the silane coupling agent is a naphthyl group. Although π-π stacking can also be formed between the naphthyl group and the benzene ring, due to the large steric hindrance, the stacking efficiency is low, resulting in insufficient uniformity of the modification layer coating and interfacial bonding force, making it difficult to effectively inhibit the volume expansion of silicon particles.

[0156] The technical features of the above examples can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above examples are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0157] The above embodiments merely represent several implementation manners of the present application. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on the patent scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the technical concept of the present application, several deformations and improvements can still be made, 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 appended claims.

Claims

1. A negative electrode active material, characterized in that, Comprising: Silicon particles with hydroxyl groups on the surface; A silane coupling agent connected to the hydroxyl groups on the surface of the silicon particles through Si - O - Si bonds, and the silane coupling agent has a benzene ring; And A cationic polyamine polymer connected to the hydroxyl groups on the surface of the silicon particles through hydrogen bonds and Si - N bonds, the cationic polyamine polymer has a benzene ring, and the benzene rings of the cationic polyamine polymer and the silane coupling agent are connected through π - π stacking interactions.

2. The negative electrode active material according to claim 1, characterized in that, The silicon particles are micron - sized silicon particles.

3. The negative electrode active material according to claim 1, characterized in that, The cationic polyamine polymer satisfies at least one of the following conditions: (1) The cationic polyamine polymer includes at least one of polyamide - amine grafted with a benzene ring, polyethyleneimine grafted with a benzene ring, and polylysine grafted with a benzene ring; (2) The weight - average molecular weight of the cationic polyamine polymer is 10000 g / mol - 40000 g / mol.

4. The negative electrode active material according to claim 1, wherein The silane coupling agent includes at least one of phenyltrimethoxysilane, phenyitriethoxysilane, and phenylvinyldimethoxysilane.

5. The negative electrode active material according to any one of claims 1 to 4, characterized in that, The surface of the negative electrode active material has a solid electrolyte interface film, and the solid electrolyte interface film includes at least one of Li2S, Li2O, and LiF.

6. A method for preparing a negative electrode active material, characterized in that, Comprising the following steps: S1. Provide silicon particles, a silane coupling agent, and a cationic polyamine polymer, wherein the silicon particles have hydroxyl groups, the silane coupling agent has a benzene ring, and the cationic polyamine polymer has a benzene ring; S2. Mix the silicon particles and the silane coupling agent and react to make the silane coupling agent connected to the hydroxyl groups on the surface of the silicon particles through Si - O - Si bonds, obtaining silane coupling agent - modified silicon particles; S3. Mix the silane coupling agent - modified silicon particles and the cationic polyamine polymer and react to make the cationic polyamine polymer connected to the hydroxyl groups on the surface of the silicon particles through hydrogen bonds and Si - N bonds, and the benzene ring of the cationic polyamine is connected to the benzene ring of the silane coupling agent through π - π stacking interactions, obtaining the negative electrode active material.

7. The method for preparing the negative electrode active material according to claim 6, wherein, Satisfy at least one of the following conditions: (1) In step S2, the reaction temperature is 60°C - 90°C and the time is 1 h - 3 h; (2) After step S2, the following step is further included: performing a first curing treatment on the silane coupling agent - modified silicon particles, the temperature of the first curing treatment is 130°C - 180°C and the time is 60 min - 120 min; (3) In step S3, the reaction temperature is 20°C - 30°C and the time is 3 h - 6 h; (4) After step S3, the following step is further included: performing a second curing treatment on the negative electrode active material, the temperature of the second curing treatment is 50°C - 80°C and the time is 90 min - 180 min.

8. A negative electrode plate, characterized in that, Comprising the negative electrode active material according to any one of claims 1 - 5 or the negative electrode active material prepared by the preparation method according to claim 6 or 7.

9. A battery, characterized in that, Comprising the negative electrode sheet according to claim 8.

10. An electrical device, characterized in that, Comprising the battery according to claim 9.

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