Secondary battery, electrode, electric device, gel-state electrolyte and preparation method

Abstract

The invention discloses a secondary battery, an electrode, an electric device, a gel-state electrolyte and a preparation method. The secondary battery comprises a positive electrode, a negative electrode and a gel-state electrolyte loaded on the positive electrode and the negative electrode, the gel-state electrolyte comprises liquid-absorbing composite particles, and the liquid-absorbing composite particles comprise a polymer and inorganic particles located on the surfaces of the liquid-absorbing composite particles. The secondary battery has the polymer imbibition composite particles containing the inorganic particles, so that the imbibition and retention functions of the gel-state electrolyte on the electrolyte can be ensured, and the gel electrolyte has small influence on the dynamics of the battery.

Description

Technical Field

[0001] This application relates to the field of batteries, specifically to secondary batteries and electrodes, electrical devices, gel electrolytes, and preparation methods. Background Technology

[0002] In recent years, semi-solid-state rechargeable batteries, especially semi-solid-state lithium-ion batteries, have received widespread attention due to their improved safety and superior lithium-ion transport kinetics. Compared to solid-state batteries, semi-solid-state rechargeable batteries not only offer better kinetic performance but also incorporate the characteristics of liquid rechargeable batteries, resulting in more mature manufacturing processes and lower production costs. Semi-solid-state rechargeable batteries typically employ a combination of gel electrolyte and liquid electrolyte to achieve lithium-ion conduction.

[0003] However, current secondary batteries and electrodes, electrical devices, gel electrolytes, and preparation methods still need improvement. Summary of the Invention

[0004] In view of the above problems, this application provides a gel electrolyte and a secondary battery using the gel electrolyte. The secondary battery has polymer liquid-absorbing composite particles containing inorganic particles, which can ensure the liquid absorption and retention functions of the gel electrolyte, and the gel electrolyte has little impact on battery kinetics.

[0005] In one aspect of this application, a gel electrolyte is provided. The gel electrolyte comprises liquid-absorbing composite particles, which include a polymer and inorganic particles located on the surface of the liquid-absorbing composite particles. This gel electrolyte exhibits good liquid absorption and retention properties.

[0006] In some embodiments, the inorganic particles have a porous structure. This can further improve the liquid absorption rate of the gel electrolyte.

[0007] In some embodiments, the polymer includes at least one of polyvinylidene fluoride, polyacrylonitrile, polyvinyl alcohol, polyacrylate, polyacrylic acid, polyisocyanate, polyurea, polycarbonate, polyether, and polyethylene ester, and their derivatives and / or copolymers. This can further improve the mechanical properties and liquid absorption rate of the gel electrolyte.

[0008] In some embodiments, the mass ratio of the inorganic particles to the polymer in the liquid-absorbing composite particles is 1:(8-20). This further improves the liquid absorption rate of the gel electrolyte.

[0009] In some embodiments, the degree of crosslinking of the polymer in the liquid-absorbing composite particles is 0.1% to 5%. This can further improve the mechanical properties of the liquid-absorbing composite particles.

[0010] In some embodiments, the Dv50 particle size of the inorganic particles is 0.01-0.5 μm. This further improves the liquid uptake rate of the gel electrolyte.

[0011] In some embodiments, the mass ratio Y of the crosslinking agent and monomer in the polymer forming the liquid-absorbing composite particles satisfies: 0 < Y ≤ 0.1. This further improves the mechanical properties of the liquid-absorbing composite particles.

[0012] In another aspect of this application, an electrode is proposed. The electrode includes a current collector and an active layer on the surface of the current collector. The active layer includes an electrode active material and a gel electrolyte. The gel electrolyte has liquid-absorbing composite particles, which include a polymer and inorganic particles on the surface of the liquid-absorbing composite particles. This electrode possesses at least one of the following advantages: good kinetic performance, high safety performance, and good liquid absorption and retention properties for the electrolyte.

[0013] In some embodiments, the gel electrolyte in the electrode may be the gel electrolyte described above.

[0014] In some embodiments, the inorganic particles have a porous structure.

[0015] In some embodiments, the polymer includes at least one of polyvinylidene fluoride, polyacrylonitrile, polyvinyl alcohol, polyacrylate, polyacrylic acid, polyisocyanate, polyurea, polycarbonate, polyether, and polyethylene ester, and their derivatives and / or copolymers.

[0016] In some embodiments, the mass ratio of the inorganic particles to the polymer in the liquid-absorbing composite particles is 1:(8-20).

[0017] In some embodiments, the degree of crosslinking of the polymer in the liquid-absorbing composite particles is 0.1% to 5%.

[0018] In some embodiments, the Dv50 particle size of the inorganic particles is 0.01-0.5 μm.

[0019] In another aspect of this application, a secondary battery is proposed. The secondary battery includes: a positive electrode, a negative electrode, and a gel-state electrolyte loaded on at least one of the positive and negative electrodes. The gel-state electrolyte includes liquid-absorbing composite particles, which comprise a polymer and inorganic particles located on the surface of the liquid-absorbing composite particles. This secondary battery possesses at least one of the following advantages: good kinetic performance, high safety performance, and good liquid absorption and retention properties for the electrolyte.

[0020] In some embodiments, the electrodes in the secondary battery may be the electrodes described above, or the gel electrolyte in the secondary battery may be the gel electrolyte described above.

[0021] In some embodiments, the polymer includes at least one of polyvinylidene fluoride, polyacrylonitrile, polyvinyl alcohol, polyacrylate, polyacrylic acid, polyisocyanate, polyurea, polycarbonate, polyether, and polyethylene ester, and their derivatives and / or copolymers.

[0022] In some embodiments, the inorganic particles have a porous structure.

[0023] In some embodiments, the material forming the inorganic particles includes at least one of alumina, silicon dioxide, and metals.

[0024] In some embodiments, the liquid-absorbing composite particles include one or more of the inorganic particles.

[0025] In some embodiments, the specific surface area of ​​the inorganic particles is 0–1500 g / m². 2 .

[0026] In some embodiments, the mass ratio of the inorganic particles to the polymer in the liquid-absorbing composite particles is 1:(8-20).

[0027] In some embodiments, the particle size of the liquid-absorbing composite particles is 0.2-10 μm.

[0028] In some embodiments, the Dv50 particle size of the inorganic particles is 0.01-0.5 μm.

[0029] In some embodiments, the degree of crosslinking of the polymer in the liquid-absorbing composite particles is 0.1% to 5%.

[0030] In some embodiments, the tensile strength of the polymer in the liquid-absorbing composite particles is 5-10 MPa.

[0031] In some embodiments, the gel electrolyte is located in the active layer of the negative electrode, and the secondary battery further includes a separator and an electrolyte.

[0032] In another aspect of this application, a method for preparing a gel electrolyte is proposed. The method includes: polymerizing a mixture containing monomers and inorganic particles via Pickering emulsion to form liquid-absorbing composite particles, wherein the liquid-absorbing composite particles have a polymer formed from the monomers, and the surface of the liquid-absorbing composite particles has the inorganic particles. Thus, a gel electrolyte with good liquid absorption and retention properties can be easily obtained.

[0033] In some embodiments, the mixture further includes an initiator and a crosslinking agent, wherein the mass ratio of the crosslinking agent to the monomer, Y, satisfies: 0 < Y ≤ 0.1.

[0034] In some embodiments, the content of the monomer in the mixture is not less than 30%.

[0035] In some embodiments, the emulsion of the Pickering emulsion polymerization contains less than 0.01% emulsifier.

[0036] In another aspect of this application, an electrical device is provided. This electrical device includes the aforementioned battery, which is used to provide electrical energy. Attached Figure Description

[0037] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0038] Figure 1 This is a schematic diagram of the liquid-absorbing composite particle structure of gel electrolyte in some embodiments of this application. Detailed Implementation

[0039] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0041] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0042] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0043] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0044] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0045] Unless otherwise stated, the terms used in this application have their common meanings as commonly understood by those skilled in the art. Unless otherwise stated, the values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this application).

[0046] As mentioned earlier, semi-solid-state batteries offer better safety and superior kinetic performance compared to all-solid-state batteries. However, current semi-solid-state batteries, especially gel electrolytes used in them, still suffer from drawbacks such as insufficient electrolyte absorption and retention capacity, complex synthesis, low monomer-polymer conversion rate, and significant impact on cell kinetics. Therefore, finding a simple way to obtain gel electrolytes with sufficient electrolyte absorption and retention properties is key to alleviating or even solving these problems.

[0047] The gel electrolyte, electrode, and secondary battery proposed in this application utilize polymer composite particles with inorganic particles on their surface. These inorganic particles help regulate and control the particle size of the liquid-absorbing composite particles, while the polymer ensures the liquid absorption and retention properties of the gel electrolyte. This inorganic-organic composite system also utilizes inorganic particles to maintain the stability of the composite particles during preparation, thereby reducing synthesis difficulty and improving the performance of the gel electrolyte.

[0048] The gel electrolyte disclosed in this application can be used, for example, in semi-solid batteries, such as by being loaded onto battery electrodes and combined with an electrolyte to form a gel-type semi-solid battery. The electrodes and batteries proposed in this application can be used in electrical devices such as vehicles, ships, or aircraft. A power system for such an electrical device can be constructed using battery cells and batteries disclosed in this application, which helps improve the safety performance of the power supply system.

[0049] refer to Figure 1 The gel electrolyte proposed in this application includes liquid-absorbing composite particles 100. The liquid-absorbing composite particles 100 include a polymer 120 and inorganic particles 110 located on the surface of the liquid-absorbing composite particles 100. The inorganic particles 110 on the surface of the liquid-absorbing composite particles 100 can regulate the overall particle size of the liquid-absorbing composite particles 100 and help maintain the stable existence of the composite particles in the system, thus allowing them to be obtained through non-in-situ polymerization.

[0050] In this application, the terms "surface" and "surface layer" should be interpreted broadly. Specifically, "surface" can refer to the surface of the liquid-absorbing composite particle, or it can refer to the inorganic particles located within a certain thickness region of the surface layer of the liquid-absorbing composite particle 100 in the inward direction. For example, the inorganic particles can be partially or completely embedded in the liquid-absorbing composite particle. The thickness of the embedded inorganic particles can range from a few nanometers to a few micrometers, specifically determined according to the thickness of the liquid-absorbing composite particle. For example, in some examples, the aforementioned embedded thickness can be 0.01-20% of the particle size of the liquid-absorbing composite particle 100, for example, 0.1-10%.

[0051] The core 100 contains a polymer and may further contain components other than polymers, such as fibers 200. The main structure of the core 100 should be composed of polymers, while other components such as fibers 200 may constitute a small portion of the core 100. For example, the core 100 may contain less than 10 wt%, less than 5 wt%, or even less than 1 wt% of fibers. The fibers 200 may be located inside the core 100, but the fiber content in the core 100 is significantly lower than the fiber content in the surface region of the composite particle.

[0052] When gel electrolytes are added in situ after electrolyte injection into the battery cell, the monomer content in the synthesis system must be low to avoid affecting the ionic conductivity and other properties of the electrolyte. Often, the monomer concentration in the system is only 3-4%, generally not exceeding 10%. Therefore, gel electrolytes synthesized in situ often suffer from low monomer conversion rates. Furthermore, pre-preparing gel electrolytes often requires cumbersome surface modification operations, and many residual small molecules in the system are difficult to remove, also affecting the performance of the battery cell. The gel electrolyte proposed in this application possesses inorganic particles 110 that play a role in maintaining stability and controlling particle size during the synthesis process. Therefore, this gel electrolyte can be obtained without in-situ synthesis after electrolyte injection, resulting in a lower production cost.

[0053] Furthermore, the gel electrolyte proposed in this application can further regulate the adsorption and liquid retention capacity of the gel electrolyte by adjusting the type of polymer and the surface morphology of inorganic particles, thus further improving the performance of the gel electrolyte.

[0054] In some embodiments, the polymer contained in the liquid-absorbing composite particles 100 may include at least one selected from polyvinylidene fluoride, polyacrylonitrile, polyvinyl alcohol, polyacrylate, polyacrylic acid, polyisocyanate, polyurea, polycarbonate, polyether, and polyethylene ester, and / or one or more selected from copolymers and derivatives of the above polymers.

[0055] derivative

[0056] Derivatives are substances containing one or more functional group segments with a parent core, with the parent core structure as the main body, through the substitution of functional groups or the replacement of segments. For example, polyvinyl alcohol derivatives are polymers with polyvinyl alcohol as the main structure, containing one or more substituted functional groups, or polymers with other monomer segments by replacing part of the vinyl alcohol monomer in the polymer.

[0057] copolymer

[0058] Copolymers are formed by the polymerization of two or more different monomers. The resulting polymer contains two or more monomer units. The arrangement of these monomers in the polymer molecular chain can be varied, resulting in random copolymers, alternating copolymers, block copolymers, graft copolymers, etc.

[0059] For example, the liquid-absorbing composite particle 100 may include one or more polymers, such as containing multiple polymers, or containing a polymer and its derivatives. Alternatively, it may contain a polymer and copolymers formed from that polymer and other polymers. In some specific examples, the core 100 may include at least one of polyacrylic acid, polyacrylate, polyisocyanate, and polyurea, or may contain copolymers formed from acrylic acid and acrylates.

[0060] The polymer significantly affects the liquid absorption and retention capacity of the liquid-absorbing composite particles 100. The liquid-absorbing composite particles 100 formed by the aforementioned polymer can exhibit good electrolyte adsorption capacity and retain the adsorbed electrolyte between the polymer chains or network structure of the composite particles, thus possessing good liquid retention capacity. For example, monomers containing ester groups can be cross-linked to obtain polymers with good swelling properties, thereby exhibiting good local liquid absorption and retention capacity. In the embodiments of this application, the specific components of the electrolyte that the gel-state electrolyte can adsorb and retain can be commonly used lithium-ion battery electrolytes, such as ethylene carbonate series electrolytes, fluorocarbonate electrolytes, etc. Specifically, the electrolyte may contain substances such as ethylene carbonate (EC), ethyl methyl carbonate (EMC), fluorocarbonate (FEC), etc.

[0061] In this application, the specific chemical composition of the inorganic particles can be selected according to the performance requirements of the gel electrolyte. For example, the materials forming the inorganic particles may include at least one of alumina, silicon dioxide, and metals. Particles with morphologies such as alumina, silicon dioxide, and metal spheres have the advantages of being relatively inexpensive and readily available from a wide range of sources. Using metal inorganic particles can further improve the conductivity of the gel electrolyte.

[0062] In some embodiments, to further improve the liquid absorption performance of the gel electrolyte, inorganic particles with a porous structure can be selected. For example, inorganic particles with macroporous, mesoporous, or microporous structures can be selected to improve the wettability of the electrolyte to the inorganic particles and to further enhance the liquid absorption and retention performance of the gel electrolyte. Specifically, the specific surface area of ​​the inorganic particles can be 0–1500 g / m². 2 In this application, the specific surface area of ​​the inorganic particles was measured using the gas adsorption method specified in GB / T19587-2017. For example, it can be 10 g / m². 2 20g / m 2 30g / m 2 50g / m 2 80g / m 2 100g / m 2 200g / m 2 300g / m 2 500g / m 2800g / m 2 1000g / m 2 1200g / m 2 Or 1500g / m 2 Specifically, it can be 1200g / m 2 .

[0063] In some embodiments, the liquid-absorbing composite particle 100 may contain one or more inorganic particles. For example, it may contain multiple inorganic particles with different chemical compositions, or it may contain multiple particles with the same chemical composition but different specific surface areas. This allows for more precise control of the liquid absorption performance of the liquid-absorbing composite particle 100, enabling it to meet the requirements of different semi-solid-state secondary batteries.

[0064] In some embodiments, the content of inorganic particles and polymer in the liquid-absorbing composite particles 100 can satisfy the following: the mass ratio of inorganic particles to polymer is 1:(8-20). For example, the content ratio of inorganic particles to polymer can be 1:(10-20), such as 1:10, 1:12, 1:15, 1:16, 1:18, 1:20, etc. When the mass ratio of the two meets the above requirements, it is beneficial to assist in the formation of liquid-absorbing composite particles with a suitable particle size and to maintain the adsorption and retention capacity of the liquid-absorbing composite particles 100 for electrolyte to meet the requirements of gel electrolyte.

[0065] In some examples, the content of inorganic particles and polymers can be determined by methods such as thermogravimetric analysis (TG). For instance, TG can be used to determine the change in mass of the liquid-absorbing composite particles as a function of temperature under programmed temperature control. Since the polymers and fibers in the liquid-absorbing composite particles decompose at different temperatures, the content of inorganic particles and polymers can be determined from the obtained thermogravimetric curve (a curve of sample weight versus temperature or time).

[0066] Those skilled in the art can also control the fiber and polymer content in the obtained liquid-absorbing composite particles by controlling the mass of the monomers used to form the polymer and the inorganic particles. For example, the mass ratio of inorganic particles to monomers used to form the polymer can be 1:10, 1:12, 1:13, 1:15, 1:16, 1:18, 1:19, etc. When the fiber and polymer content in the liquid-absorbing composite particles meets the above ranges, the inorganic particles can effectively regulate the particle size of the liquid-absorbing composite particles, and the content of inorganic particles in the formed liquid-absorbing composite particles is also moderate, without significantly affecting the mechanical properties and liquid absorption performance of the liquid-absorbing composite particles.

[0067] In some examples, the particle size of the liquid-absorbing composite particles can be 0.2-10 μm. In some embodiments, the particle size of the liquid-absorbing composite particles is 0.2-5 μm. For example, the particle size of the liquid-absorbing composite particles can be 0.2 μm, 0.25 μm, 0.5 μm, 0.8 μm, 1 μm, 3 μm, 5 μm, 8 μm, 10 μm, etc.

[0068] Those skilled in the art will understand that gel-state electrolytes achieve their liquid retention function by swelling upon adsorption of the electrolyte. Therefore, in actual use, the liquid-absorbing composite particles will also swell upon contact with the electrolyte to achieve liquid retention. The particle size of the aforementioned liquid-absorbing composite particles in this application refers to the particle size of the liquid-absorbing composite particles before swelling. This particle size will increase to a certain extent after swelling.

[0069] In this application, the particle size of the liquid-absorbing composite particles can be the particle size of the majority or most particles in the liquid-absorbing composite particles, or the average particle size of the liquid-absorbing composite particles. For example, it can be the Dv50 particle size, meaning that 50% of the particles in the composite particles have a diameter below this value. In some examples, the liquid-absorbing composite particles can be loaded onto an electrode sheet together with the electrode active material, and the particle size of the liquid-absorbing composite particles is measured after loading them onto the electrode sheet and drying them. In this case, most or most of the electrolyte adsorbed by the liquid-absorbing composite particles during use will be removed during the drying process. For example, the particle size of the liquid-absorbing composite particles can be determined by information from scanning electron microscope (SEM) images. For example, the average particle size can be determined using software such as Avizo 3D based on the SEM images, or the Dv50 particle size can be determined using particle size analysis methods. Alternatively, multiple liquid-absorbing composite particles can be selected within the field of view of one or more SEM images, and their particle sizes can be measured separately. The average value of the obtained multiple particle sizes is determined as the particle size of the liquid-absorbing composite particles. The number of selected particles can be 10 or more, specifically 20 or more, 30 or more, or 50 or more.

[0070] When the particle size of the liquid-absorbing composite particles is controlled within the above range, the ability of the liquid-absorbing composite particles to absorb electrolyte can be better improved, and the particles can maintain a reasonable particle size after swelling after liquid absorption, thereby ensuring that the electrode surface can have a sufficient load of active electrode particles.

[0071] In some embodiments, to further improve the surface properties of the obtained liquid-absorbing composite particles, inorganic particles with electronegative functional groups modified on the surface, or inorganic particles that have undergone certain surface energy adjustment treatments, can be selected. The above treatments are more conducive to the dissociation of lithium salts in the electrolyte, enhancing lithium-ion conduction capability, thereby further improving the lithium-ion transport kinetics of cells, batteries, etc., utilizing this gel-state electrolyte.

[0072] In some embodiments, the polymer forming the liquid-absorbing composite particles can be a cross-linked polymer. Specifically, a cross-linked polymer can be obtained by adding a cross-linking agent to the raw materials used to synthesize the liquid-absorbing composite particles. Cross-linked polymers have better electrolyte stability and can maintain the integrity of the particle size of the liquid-absorbing composite particles even when immersed in an electrolyte environment for a long time, thereby helping to further improve the lifespan of secondary batteries using this gel-state electrolyte. In some embodiments, the raw materials used to synthesize the liquid-absorbing composite particles may include an initiator, a cross-linking agent, and a monomer. The specific types of initiators and cross-linking agents can be selected according to the type of monomer. For example, the initiator can be azobisisobutyronitrile (AIB), and the cross-linking agent can be divinylbenzene. The degree of cross-linking of the obtained polymer can be adjusted by controlling the mass ratio of the cross-linking agent and the monomer. For example, the mass ratio Y of the cross-linking agent and the monomer can be set to: 0 < Y ≤ 0.1. In some specific embodiments, the value of Y can satisfy 0 < Y < 0.05. For example, the value of Y can be 0.02, 0.025, 0.03, 0.035, 0.04, or 0.05. Properly controlling the ratio of the cross-linking agent and the monomer can obtain a polymer with a relatively ideal degree of cross-linking. Therefore, the resulting polymer can possess good liquid absorption and retention properties. For example, a polymer with a moderate degree of crosslinking can maintain the stability of the liquid-absorbing composite particles in the electrolyte, avoiding the polymer from being dissolved in the electrolyte for a long time due to insufficient crosslinking, thus failing to maintain a stable gel state. An appropriate degree of crosslinking can also enable the polymer to have sufficient liquid retention properties.

[0073] In some embodiments, the specific chemical composition of the polymer in the liquid-absorbing composite particles can be selected according to the liquid absorption and retention performance requirements of the gel electrolyte. For example, the liquid absorption ratio, ion permeability, and liquid retention performance of the gel electrolyte can be adjusted by changing the degree of crosslinking of the polymer. Specifically, the degree of crosslinking of the polymer in the liquid-absorbing composite particles can be 0.15-5%, more specifically, it can be 0.5%-1.5%.

[0074] crosslinking degree

[0075] The degree of crosslinking can also be expressed as crosslinking density, the number-average molecular weight between two adjacent crosslinking points, or the number of moles of crosslinking points per cubic centimeter. The degree of crosslinking can be determined by various methods, such as tensile testing, swelling testing, thermogravimetric analysis, and differential scanning calorimetry. In this application, the degree of crosslinking of the polymer can be expressed as the molar percentage of the crosslinking agent in the polymer. The molar percentage of the crosslinking agent can be determined by the amount of each component added to the raw materials forming the polymer, or by performing tests on the polymer such as thermogravimetric analysis.

[0076] In some embodiments, the tensile strength of the polymer in the gel electrolyte can be 5-10 MPa. Specifically, it can be 5 MPa, 5.5 MPa, 6 MPa, 7 MPa, 7.5 MPa, 8 MPa, 8.5 MPa, 9 MPa, 9.5 MPa, or 10 MPa. In this application, the tensile strength can be determined by the method in GB1040-1992. When the above parameters of the core meet the requirements, the polymer-formed core can maintain a good semi-solid state after absorbing the electrolyte, and the composite particles can have good liquid absorption and retention properties.

[0077] In another aspect of this application, a method for preparing a gel electrolyte is proposed. The method includes: polymerizing a mixture containing monomers and inorganic particles via Pickering emulsion to form liquid-absorbing composite particles, wherein the liquid-absorbing composite particles have a polymer formed from the monomers, and the surface of the liquid-absorbing composite particles has the inorganic particles. The liquid-absorbing composite particles can be those included in the gel electrolytes described above. Specifically, the liquid-absorbing composite particles have a polymer formed from the monomers, and the particle surface has inorganic particles. This method can easily provide a gel electrolyte having all the characteristics of the aforementioned gel electrolytes, and will not be elaborated further here. This method has at least the advantages of being simple to operate and low in cost.

[0078] Pickering emulsion

[0079] Pickering emulsions are emulsion systems that use solid particles as emulsifiers and other surface-active components to maintain system stability.

[0080] In some specific embodiments, the mixture forming the liquid-absorbing composite particles may also contain an initiator and a crosslinking agent. The specific types of initiators and crosslinking agents may be as described above, or may be selected based on the specific chemical composition of the monomers.

[0081] In some examples, the mass ratio Y of the crosslinking agent to the monomer in the mixture satisfies: 0 < Y ≤ 0.1. By controlling the amount of crosslinking agent added, the degree of crosslinking of the obtained polymer can be adjusted, thereby regulating the liquid absorption and retention properties of the formed gel electrolyte.

[0082] In some examples, the monomer content in the mixture may be no less than 30%. The method proposed in this application uses in-situ synthesis to form polymers, so the monomer concentration in the mixture can be relatively high.

[0083] To obtain a more uniformly dispersed mixture, the monomer, initiator, and crosslinking agent can be mixed thoroughly first, followed by the addition of inorganic particles. In some embodiments, the inorganic particles may be pre-dispersed in the solvent, thereby further improving the homogeneity of the system. Stirring the mixture can be achieved using a high-speed shear press, for example, at 4000-5500 rpm. The above operations are beneficial for obtaining a uniformly dispersed Pickering emulsion system.

[0084] In some examples, the emulsifier content in the Pickering emulsion polymerization emulsion is less than 0.01%. Because inorganic ions are added to the system, the emulsion may contain very little or no emulsifier. Inorganic particles and other solid particles act as emulsifiers in the system, maintaining the water-oil interface balance on the surface of the emulsion microspheres, ultimately obtaining liquid-absorbing composite particles that meet the requirements of gel-state electrolytes. In some examples, the Pickering emulsion can be reacted at 50-80°C with stirring for 10-20 hours. This allows the monomers to fully polymerize, forming composite particles with good liquid absorption and retention properties.

[0085] Those skilled in the art will understand that the method proposed in this application may also include conventional post-processing operations, such as washing, separation, and drying. Alternatively, the product containing composite particles may be directly mixed with the electrode active material to form a slurry, and the residual water or other solvents in the product may be removed by the drying operation in the electrode preparation process.

[0086] In another aspect, this application proposes an electrode. The electrode includes a current collector and an active layer on the surface of the current collector. The active layer includes an electrode active material and a gel electrolyte. The gel electrolyte has liquid-absorbing composite particles, which include a polymer and inorganic particles on the surface of the liquid-absorbing composite particles. Thus, this electrode possesses all the features and advantages of the aforementioned gel electrolyte, which will not be repeated here. In summary, this electrode can be used in semi-solid-state batteries and has good liquid absorption and retention properties.

[0087] In some embodiments, the electrode is the negative electrode of a lithium-ion battery, and the content of the gel electrolyte in the electrode is 0.01 wt% to 20 wt% of the electrode loading. When the content of the gel electrolyte meets the above range, the electrode has good battery performance. The appropriate content of the gel electrolyte can ensure that there are sufficient active components in the electrode, that the active components can be fully exposed in the electrolyte, and that the electrode can have sufficient liquid retention performance.

[0088] In some examples, as previously described, the aforementioned gel electrolyte can be added to the slurry forming the electrode, and the slurry can be dried using the electrode manufacturing process to obtain an electrode loaded with liquid-absorbing composite particles. After drying and other processes, the particle size of the liquid-absorbing composite particles in the gel electrolyte on the electrode surface can be 0.2-10 μm, more specifically 0.2-5 μm. When the particle size of the liquid-absorbing composite particles is within the above range, the particles can still have a relatively suitable size after liquid absorption and swelling, and maintain good liquid absorption and retention properties.

[0089] In another aspect, this application proposes a secondary battery. The battery includes a positive electrode, a negative electrode, and a gel-state electrolyte loaded on at least one of the positive and negative electrodes. The gel-state electrolyte includes liquid-absorbing composite particles, which comprise a polymer and inorganic particles located on the surface of the liquid-absorbing composite particles. Thus, the battery possesses all the features and advantages of the aforementioned electrodes, which will not be repeated here. In general, this battery can be a gel-state and / or semi-solid-state battery and has good liquid absorption and retention properties.

[0090] In one embodiment, the gel electrolyte may be located in the active layer of at least one of the positive and negative electrodes. For example, the aforementioned gel electrolyte may be added to the active layer slurry forming the negative electrode, and an electrode containing electrode active materials and gel electrolyte may be formed through processes such as coating and drying. The secondary battery may further include a separator and an electrolyte.

[0091] In another aspect, this application proposes an electrical device. This electrical device includes the aforementioned battery for providing electrical energy. Thus, the electrical device possesses all the features and advantages of the aforementioned battery, which will not be repeated here. In general, this electrical device can utilize gel-state and / or semi-solid-state batteries to provide electrical energy, and therefore has better safety performance.

[0092] In this application, the electrical device can be such as a mobile phone, tablet, laptop, electric toy, power tool, electric vehicle, electric car, ship, spacecraft, etc. Electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0093] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0094] Example 1: Preparation of Gel Electrolytes

[0095] Mix 15 mL of butyl acrylate, 0.015 g of azobisisobutyronitrile initiator, and 0.15 g of divinylbenzene crosslinking agent evenly to prepare a solution for later use.

[0096] Take 60 mL of deionized water and add 1 g of inorganic particles (porous alumina, Dv50, particle size 50 nm, BET 1200 g / m³). 2 Disperse evenly;

[0097] A mixture containing monomers was added to an inorganic particle dispersion and mixed at 5000 rpm under a high-speed shear press to prepare a Pickering emulsion. The emulsion was then poured into a flask and stirred at 70°C for 16 h.

[0098] The raw materials for Examples 2-14 are shown in Table 1 below. Gel electrolytes were prepared using the same process as in Example 1.

[0099]

[0100] A battery was prepared using the electrolyte obtained in the examples. The battery fabrication process is as follows:

[0101] Negative electrode sheet manufacturing:

[0102] The negative electrode dispersant is uniformly dispersed in an aqueous solution. The negative electrode conductive agent, negative electrode active material, and gel electrolyte (obtained in Examples 1-14) are pre-mixed and added to the above aqueous solution. After stirring for a period of time, the negative electrode binder is added to form a slurry. The ratio of negative electrode active material, gel electrolyte, binder, dispersant, conductive agent, and plasticizer in the slurry is 94.8%:2%:1.5%:1.0%:0.5%:0.2%. After thorough stirring, the slurry is filtered through a 150-mesh screen and coated onto the negative electrode current collector according to the corresponding coating weight. The above electrode sheet is then rolled and cut to obtain negative electrode sheets for later use.

[0103] Positive electrode sheet production:

[0104] The positive electrode binder and N-methylpyrrolidone are thoroughly mixed to form a uniform and transparent adhesive. The positive electrode conductive agent is added to the adhesive and stirred thoroughly. After mixing evenly, the positive electrode active material (NCM-811) is added and stirred evenly. The slurry is then sieved and coated onto the positive electrode current collector. After rolling and slitting, the positive electrode sheet is obtained for later use.

[0105] Separator: The separator is made of PE coated with CCS (ceramic coating) on ​​both sides.

[0106] Electrolyte: Ethyl carbonate, methyl ethyl carbonate, diethyl carbonate, and fluoroethylene carbonate (FEC) are mixed evenly in a volume ratio of 1:1:1:1, and LiPF6 is added and dissolved in an organic solvent to a concentration of 1 mol / L.

[0107] Using the gel electrolytes prepared in Examples 1-14 above, battery samples 2-1 to 2-14 were prepared according to the following procedures:

[0108] Battery making:

[0109] The coated separator and the aforementioned positive and negative electrode sheets are assembled into a bare cell by stacking. Then, the cell undergoes top-side sealing, high-temperature baking, electrolyte injection, formation, and capacity testing to produce a secondary battery. The capacity testing steps are as follows:

[0110] 1. Let the lithium-ion battery stand at 25℃ for 5 minutes;

[0111] 2. Charge to 4.25V using a 1 / 3C constant current method;

[0112] 3. 4.25V constant voltage charging, cut-off current 0.05C;

[0113] 4. Let stand for 5 minutes at 25℃;

[0114] 5. Discharge at 1 / 3C constant current to 4.25V;

[0115] 6. Let stand for 5 minutes;

[0116] 7. Discharge at a constant current of 0.1C to 2.8V;

[0117] 8. Let stand for 5 minutes;

[0118] 9. Charge at a constant current of 0.5C to 3.85V;

[0119] 10. Maintain a constant voltage of 3.85V to 0.05C;

[0120] 11. Let stand for 5 minutes.

[0121] Comparative Example 1: Secondary Battery

[0122] The remaining parameters are the same as those of the secondary battery sample 2-1 prepared in Example 1. The difference is that the negative electrode sheet does not have a gel electrolyte, and battery sample 2-15 is obtained.

[0123] Comparative Example 2: Secondary Battery

[0124] The remaining parameters are the same as those of the secondary battery sample 2-1 prepared in Example 1, except that only the same specific surface area of ​​1200 g / m² was added as in Example 1. 2 Alumina particles, without the addition of monomers, initiators, or crosslinking agents, were used to prepare battery samples 2-16.

[0125] The negative electrodes of samples 2-1 to 2-16, as well as the liquid absorption and retention capacity and cell performance of the secondary batteries, were tested. The specific tests are as follows:

[0126] (1) Liquid absorption capacity test:

[0127] The negative electrode prepared from the above samples 2-1 to 2-16 is the test material, and the initial weight is recorded as N1. At a temperature of 25°C, the test material is wrapped with a diaphragm and immersed in the electrolyte solvent for 24 hours. After standing for the electrolyte on its surface to evaporate, the mass after liquid absorption is measured as N2, and the liquid absorption rate is calculated as (N2-N1) / N1*100%.

[0128] (2) Liquid retention capacity test:

[0129] After the initial negative electrode sheet is immersed in the electrolyte to fully absorb the liquid, it is centrifuged at 8000 rpm to test the mass of electrolyte lost by centrifugation.

[0130] The electrolyte solvent used in the liquid absorption and retention capacity test is the same electrolyte used in secondary batteries.

[0131] (3) Cell DCR:

[0132] 1. Let the lithium-ion battery stand at 25℃ for 30 minutes;

[0133] 2. Charge the battery at a constant current of 0.33C to 4.25V, then charge it at a constant voltage with a cutoff current of 0.05C. At this point, the battery is at 100% SOC.

[0134] 3. Let stand at 25℃ for 5 minutes;

[0135] 4. 0.33C discharge, cutoff current 0.5C;

[0136] 5. Let stand at 25℃ for 1 hour;

[0137] 6. 5C discharge for 30 seconds;

[0138] 7. Let stand at 25℃ for 40 seconds;

[0139] 8. 3.75C constant current charging for 30 seconds;

[0140] 9. Let stand at 25℃ for 1 hour;

[0141] 10. Charge at a constant current of 0.33C to 3.65V, then charge at a constant voltage with a cutoff current of 0.05C;

[0142] 11. Let stand for 5 minutes at 25℃;

[0143] 12. Discharge at 0.33C, cutoff current 0.9C;

[0144] 13. Let stand at 25℃ for 1 hour;

[0145] 14. 5C discharge for 30 seconds;

[0146] 15. Let stand for 40 seconds at 25℃;

[0147] 16. 3.75C constant current charging for 30 seconds;

[0148] 17. Let stand for 5 minutes at 25℃;

[0149] 18. Detect the DC resistance of a lithium-ion battery at 50% SOC.

[0150] The test results are shown in Table 2 below:

[0151] Table 2

[0152]

[0153]

[0154] Referring to Table 2 above, samples 2-1 to 2-14, prepared using gel electrolytes from Examples 1-14 of this application, all exhibit good liquid absorption and retention properties, the resulting polymers have moderate tensile strength, and the cell DCR can be maintained at a certain level. Compared to sample 2-15 without added gel electrolyte, the cell DCR test results of samples 2-1 to 2-14 did not show a significant increase, indicating that the added gel electrolyte did not significantly affect the electrical performance of the cell. Sample 2-16 only added a specific surface area of ​​1200 g / m². 2 The alumina particles have poor liquid absorption properties, indicating that the liquid absorption and retention properties of samples 2-1 to 2-14 are mainly provided by the synthesized gel electrolyte.

[0155] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A secondary battery, characterized in that, include: A positive electrode, a negative electrode, and a gel electrolyte loaded on at least one of the positive and negative electrodes. The gel electrolyte comprises liquid-absorbing composite particles, which include a polymer and inorganic particles located on the surface of the liquid-absorbing composite particles.

2. The secondary battery according to claim 1, characterized in that, The polymers include at least one of polyvinylidene fluoride, polyacrylonitrile, polyvinyl alcohol, polyacrylate, polyacrylic acid, polyisocyanate, polyurea, polycarbonate, polyether and polyethylene ester, and their derivatives and / or copolymers.

3. The secondary battery according to claim 1 or 2, characterized in that, The inorganic particles have a porous structure, and / or The materials that form the inorganic particles include at least one of alumina, silicon dioxide, and metals.

4. The secondary battery according to claim 3, characterized in that, The liquid-absorbing composite particles include a variety of inorganic particles.

5. The secondary battery according to claim 3 or 4, characterized in that, The specific surface area of ​​the inorganic particles is 0–1500 g / m². 2 .

6. The secondary battery according to any one of claims 1-5, characterized in that, The mass ratio of the inorganic particles to the polymer in the liquid-absorbing composite particles is 1:(8-20); and / or The liquid-absorbing composite particles have a particle size of 0.2-10 μm; and / or The inorganic particles have a Dv50 particle size of 0.01-0.5 μm.

7. The secondary battery according to any one of claims 1-6, characterized in that, The degree of crosslinking of the polymer in the liquid-absorbing composite particles is 0.1% to 5%.

8. The secondary battery according to any one of claims 1-7, characterized in that, The tensile strength of the polymer in the liquid-absorbing composite particles is 5-10 MPa.

9. The secondary battery according to any one of claims 1-8, characterized in that, The gel electrolyte is located in the active layer of the negative electrode, and the secondary battery further includes a separator and an electrolyte.

10. An electrode, characterized in that, The electrode includes: Current collector, and An active layer is located on the surface of the current collector. The active layer includes an electrode active material and a gel electrolyte. The gel electrolyte has liquid-absorbing composite particles, which include a polymer and inorganic particles located on the surface of the liquid-absorbing composite particles.

11. The electrode according to claim 10, characterized in that, The inorganic particles have a porous structure, and / or, The polymer comprises at least one of polyvinylidene fluoride, polyacrylonitrile, polyvinyl alcohol, polyacrylate, polyacrylic acid, polyisocyanate, polyurea, polycarbonate, polyether, and polyethylene ester, and their derivatives and / or copolymers, and / or, The mass ratio of the inorganic particles to the polymer in the liquid-absorbing composite particles is 1:(8-20), and / or, The degree of crosslinking of the polymer in the liquid-absorbing composite particles is 0.1% to 5%, and / or, The inorganic particles have a Dv50 particle size of 0.01-0.5 μm.

12. A gel electrolyte, characterized in that, It includes liquid-absorbing composite particles, which comprise a polymer and inorganic particles located on the surface of the liquid-absorbing composite particles.

13. The gel electrolyte according to claim 12, characterized in that, The inorganic particles have a porous structure, and / or, The polymer comprises at least one of polyvinylidene fluoride, polyacrylonitrile, polyvinyl alcohol, polyacrylate, polyacrylic acid, polyisocyanate, polyurea, polycarbonate, polyether, and polyethylene ester, and their derivatives and / or copolymers, and / or, The mass ratio of the inorganic particles to the polymer in the liquid-absorbing composite particles is 1:(8-20), and / or, The degree of crosslinking of the polymer in the liquid-absorbing composite particles is 0.1% to 5%, and / or, The inorganic particles have a Dv50 particle size of 0.01-0.5 μm.

14. The gel electrolyte according to claim 12 or 13, characterized in that, The mass ratio Y of crosslinking agent and monomer in the polymer forming the liquid-absorbing composite particles satisfies: 0 < Y ≤ 0.

1.

15. A method for preparing a gel electrolyte, characterized in that, include: A mixture containing monomers and inorganic particles is polymerized via Pickering emulsion to form liquid-absorbing composite particles, wherein the liquid-absorbing composite particles have a polymer formed from the monomers and the inorganic particles are present on the surface of the liquid-absorbing composite particles.

16. The method according to claim 15, characterized in that, The mixture further includes an initiator and a crosslinking agent, wherein the mass ratio Y of the crosslinking agent to the monomer satisfies: 0 < Y ≤ 0.1; and / or, The content of the monomer in the mixture is not less than 30%; and / or, The emulsion produced by the Pickering emulsion polymerization contains less than 0.01% emulsifier.

17. An electrical device, characterized in that, The electrical device includes a secondary battery as described in any one of claims 1-9, the secondary battery being used to provide electrical energy.

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