Gel electrolyte preparation method, electrode, battery and electric device

Abstract

The invention discloses a gel electrolyte preparation method, an electrode, a battery and an electric device. The secondary battery includes a gel electrolyte including a composite particle having a core containing a polymer, and a surface region covering at least a portion of a surface of the core, the surface region having fibers. The gel electrolyte has relatively good liquid absorption and liquid retention performance.

Description

Technical Field

[0001] This application relates to the field of batteries, specifically to a method for preparing a gel electrolyte, an electrode, a battery, and an electrical device. Background Technology

[0002] Secondary batteries such as liquid lithium-ion batteries use liquid electrolytes, thus relying on the liquid electrolyte to provide high ionic conductivity and good electrode wettability. However, liquid lithium batteries also have drawbacks such as easy leakage, flammability, and explosiveness, posing significant safety hazards. All-solid-state batteries, because they contain no liquid components, offer high safety, but suffer from drawbacks such as high interfacial impedance, low ionic conductivity, and short cycle life. Gel-type semi-solid-state batteries have electrochemical performance indicators between liquid lithium-ion batteries and all-solid-state batteries, offering relatively high safety. Furthermore, they can absorb liquid electrolytes, thus exhibiting better lithium-ion transport kinetics compared to solid-state batteries.

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

[0004] In view of the above problems, this application provides a gel electrolyte and its preparation method, electrode, battery and power device. By introducing fibers into the surface of the gel electrolyte particles, the fibers act as emulsifiers in the process of forming composite particles, which can maintain the good liquid absorption and retention properties of the polymer gel electrolyte and simplify the preparation process of the gel electrolyte.

[0005] In one aspect of this application, a gel electrolyte is provided. The gel electrolyte comprises composite particles having a core and a surface region covering at least a portion of the surface of the core, the core containing a polymer and the surface region having fibers. This gel electrolyte exhibits good liquid absorption and retention properties, and the fibers in the surface region can act as an emulsifier during the formation of the composite particles, which simplifies the preparation process and limits the size of the polymer-formed core, resulting in composite particles of suitable size.

[0006] In some embodiments, the polymer includes one or more of polyvinylidene fluoride, polyacrylonitrile, polyvinyl alcohol, polyacrylate, polyacrylic acid, polyisocyanate, polyurea, polycarbonate, polyether, polyethylene ester and its derivatives and copolymers.

[0007] In some embodiments, the composite particles satisfy at least one of the following conditions: the mass ratio of the fiber to the polymer in the composite particles is 1:(8-20); the particle size of the composite particles is 0.2-10 μm, optionally 0.2-5 μm; the diameter of the fiber is 10-600 nm; the length of the fiber is 0.1-100 μm; and the aspect ratio of the fiber is 2-2000.

[0008] In some embodiments, the fiber has a diameter of 10-500 nm and a length of 0.4-5 μm.

[0009] In some embodiments, the particle size of the composite particles is 0.2-5 μm.

[0010] In some embodiments, the fiber includes at least one of cellulose fiber, chitin fiber, chitosan fiber, aramid fiber, carbon nanotube, silk fiber, bacterial fiber, and resin fiber.

[0011] In some embodiments, the degree of crosslinking of the polymer in the core is 0.1%-5%.

[0012] In some embodiments, the tensile strength of the polymer in the core is 5-10 MPa.

[0013] In some embodiments, the raw materials forming the polymer include a crosslinking agent and a monomer, wherein the mass ratio Y of the crosslinking agent and the monomer satisfies: 0 < Y ≤ 0.1.

[0014] In some embodiments, Y satisfies: 0 < Y < 0.05.

[0015] In some embodiments, the absolute value of the difference between the fiber's Dv90 and Dv10 is 30-40 μm.

[0016] In some embodiments, the monomers forming the polymer include at least one of acrylic acid, acrylate, isocyanate, and urea compounds, and the fibers include cellulose fibers with a diameter of 10-500 nm and a length of 0.4-5 μm.

[0017] In another aspect of this application, a method for preparing a gel electrolyte is proposed. The method includes: providing a mixture comprising monomers and fibers and stirring to form a Pickering emulsion, thereby obtaining composite particles having a polymer-containing core and a surface region covering at least a portion of the surface of the core, the surface region having the fibers.

[0018] In some embodiments, the method satisfies at least one of the following conditions: the mixture includes an initiator and a crosslinking agent; the mixture contains a crosslinking agent at a mass ratio of 0.001-0.5 to the monomer; the monomer content in the mixture is not less than 30%; the fiber is pre-dispersed in water and then mixed with the monomer; the stirring is performed using a high-speed shearing machine at 4000-5500 rpm; the Pickering emulsion does not contain an emulsifier; obtaining the composite particles includes reacting the Pickering emulsion at 50-80°C with stirring for 10-20 hours.

[0019] In another aspect of this application, an electrode is provided. The electrode comprises: a current collector, an electrode active material loaded on the current collector, and the aforementioned gel electrolyte.

[0020] In some embodiments, the electrode is the negative electrode of a lithium-ion battery, the content of the gel electrolyte in the electrode is 0.01wt%-20wt% of the electrode loading, and the particle size of the composite particles in the gel electrolyte is 0.2-10μm.

[0021] In another aspect of this application, a battery is proposed. This battery includes the electrodes described above.

[0022] 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

[0023] 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:

[0024] Figure 1 This is a schematic diagram of the composite particle structure of the gel electrolyte in some embodiments of this application. Detailed Implementation

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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).

[0031] 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).

[0032] Currently, judging from market trends, the application of power batteries is becoming increasingly widespread. Power batteries are not only used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, but also extensively used in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. With the continuous expansion of power battery applications, market demand is also constantly increasing.

[0033] Gel-type semi-solid-state batteries and gel electrolytes have gained widespread attention due to their superior safety and electrical performance compared to all-solid-state batteries. However, current gel electrolytes still suffer from drawbacks such as limited liquid absorption capacity, the significant impact of in-situ synthesis on cell kinetics, and low polymer conversion efficiency. Therefore, addressing or resolving at least one of these issues would greatly improve the performance of gel electrolytes and facilitate their further application.

[0034] Gel electrolytes are electrolytes that exist between liquid and solid states. They generally include solid-phase and polymer electrolytes that coexist with a liquid phase. They consist of a polymer matrix, a solvent containing electrolyte salts, and additives. The polymer matrix can absorb a certain amount of liquid components, which are dispersed in the polymer spatial network to form a quasi-solid electrolyte that contains liquid components but is not fluid.

[0035] This application proposes a gel electrolyte comprising composite particles with a polymer core and fibers on the surface. The polymer core provides the gel electrolyte with good liquid absorption and retention properties, while the fibers on the surface help regulate and control the particle size and maintain stability in the system, acting as an emulsifier during the formation of the gel electrolyte. Therefore, this gel electrolyte can be prepared in a relatively simple manner, achieving composite particles of suitable size with little or no added emulsifier during preparation. This gel electrolyte can be composited onto electrode sheets using a non-in-situ synthesis method.

[0036] 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.

[0037] According to some embodiments of this application, reference is made to Figure 1 The gel electrolyte proposed in this application comprises composite particles having a core 100 and a surface region covering at least a portion of the surface of the core, the surface region having fibers 200. The core 100 contains a polymer. The fibers 200 in the surface region can regulate the particle size of the core 100 and help maintain the stability of the composite particles in the system, thus allowing them to be added to the battery cell via non-in-situ polymerization.

[0038] 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.

[0039] In this application, the term "surface region" should be interpreted broadly. Specifically, the surface region can be located on the surface of the particle or extend into the core, forming a surface region of a certain thickness. The thickness of the surface region can range from a few nanometers to a few micrometers, depending on the thickness of the composite particle. For example, in some examples, the thickness of the surface region can be 0.01-20% of the particle size of the composite particle, such as 0.1-10%.

[0040] 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 small molecules remaining in the system are difficult to remove, also affecting the performance of the battery cell. The gel electrolyte proposed in this application features composite particles whose stability and particle size control are achieved by the fiber 200 in the surface region. This allows the gel electrolyte to be prepared without in-situ synthesis after electrolyte injection, and its properties can be adjusted more easily to meet the requirements for liquid absorption and retention.

[0041] In some embodiments, the polymer of the core 100 may include one or more selected from polyvinylidene fluoride, polyacrylonitrile, polyvinyl alcohol, polyacrylate, polyacrylic acid, polyisocyanate, polyurea, polycarbonate, polyether, polyethylene ester and its derivatives and copolymers.

[0042] derivative

[0043] 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.

[0044] copolymer

[0045] 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.

[0046] For example, core 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 of that polymer and other polymers. In some specific examples, core 100 may include at least one of polyacrylic acid, polyacrylate, polyisocyanate, and polyurea, or may contain copolymers of, for example, acrylic acid and acrylates.

[0047] The polymer core formed by the above-mentioned polymer has a good ability to adsorb electrolyte and can retain the adsorbed electrolyte between the polymer chains or network structure of the composite particles, thus having a good liquid retention capacity. For example, monomers containing ester groups can be cross-linked to obtain polymers with good swelling properties, thus having good local liquid absorption and retention capacity. In the embodiments of this application, the specific components of the electrolyte that the gel 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 ethylene carbonate (EC), ethyl methyl carbonate (EMC), fluorocarbonate (FEC), etc.

[0048] In some embodiments, the content of fiber and polymer in the composite particles can satisfy a fiber-to-polymer mass ratio of 1:(8-20). For example, the fiber-to-polymer content ratio can be 1:(10-20), such as 1:10, 1:12, 1:15, 1:16, 1:18, 1:20, etc.

[0049] In some examples, the fiber and polymer content can be determined by methods such as thermogravimetric analysis (TG). For instance, TG can be used to determine the change in mass of the composite particles as a function of temperature under programmed temperature control. Since the polymers and fibers in the composite particles decompose at different temperatures, the fiber and polymer content can be determined from the obtained thermogravimetric curve (a curve of sample weight versus temperature or time).

[0050] Those skilled in the art can also control the fiber and polymer content in the produced composite particles by controlling the quality of the monomers used to form the polymer and the fibers. For example, the mass ratio of fibers to monomers used to form the polymer can be 1:10, 1:12, 1:13, 1:15, 1:16, 1:18, 1:19, etc.

[0051] When the content of fiber and polymer in composite particles meets the above range, the fiber can play a better role in regulating the particle size of composite particles.

[0052] In some examples, the particle size of the composite particles can be 0.2-10 μm. In some embodiments, the particle size of the composite particles is 0.2-5 μm. For example, the particle size of the 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.

[0053] In this application, the particle size of the composite particles can be the particle size of the majority or most particles in the composite particles, or the average particle size of the composite particles. For example, it can be the Dv50 particle size, that is, 50% of the particles in the composite particles have a diameter below this value. In some examples, the composite particles can be co-loaded with the negative electrode active material on the negative electrode sheet, and the particle size of the composite particles can be controlled so that after being composited on the negative electrode and dried, the Dv50 of the particles is 0.2-10 μm, more specifically 0.2-5 μm. As mentioned above, the composite particles swell due to liquid absorption during use. The adsorbed electrolyte can be removed during the drying process, and the particle size increase due to swelling of the composite particles can be reduced. Therefore, the Dv50 particle size observed by electron microscopy is basically consistent with the particle size of the composite particles before swelling.

[0054] The particles proposed in this application can be composited on the electrode surface, such as the negative electrode surface, during practical use. Therefore, the particle size affects the electrode surface morphology. In particular, the volume increases to some extent after the composite particles absorb electrolyte and swell. Therefore, controlling the particle size of the composite particles can better enhance their electrolyte absorption capacity and maintain a reasonable particle size after swelling following electrolyte absorption, thereby ensuring that the negative electrode has a sufficient loading of active electrode particles.

[0055] In this application, the fiber size can be adjusted as needed. Specifically, the fiber diameter can be 10-600 nm, the fiber length can be 0.1-100 μm, and the fiber aspect ratio can be 2-2000. The composite particles proposed in this application can have fiber sizes that meet one, two, or three of the above conditions. For example, the fiber diameter can be 10-500 nm, and the length can be 0.4-5 μm.

[0056] In some examples, the fiber diameter can be 10 nm, 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 550 nm, or 600 nm, or other integers or non-integers within the aforementioned diameter range. The fiber length can be 0.1 μm, 0.5 μm, 1 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, or 100 μm, or other integers or non-integers within the aforementioned diameter range. The fiber aspect ratio can be 4-50.

[0057] When the fiber size is within the above range, it can play a good role as an additive such as an emulsifier in the polymer polymerization process, so as to control the particle size of the composite particles and maintain the stability of the system.

[0058] In some embodiments, the specific type of fiber may be selected according to actual conditions, such as adjusting it according to the chemical composition of the polymer, the composition of the electrolyte cooperating with the gel electrolyte, etc. In some examples, the fiber may include at least one of cellulose fiber, chitin fiber, chitosan fiber, aramid fiber, carbon nanotube, silk fiber, bacterial fiber, and resin fiber, for example, one or more of the above-mentioned fibers.

[0059] For example, fibers with electronegative functional groups on their surface, such as fibers containing hydroxyl groups, can be selected. These fibers are more conducive to the dissociation of lithium salts in the electrolyte, improving lithium-ion conduction capacity, thereby further improving the lithium-ion transport kinetics of cells, batteries, etc., utilizing this gel electrolyte.

[0060] In some embodiments, the specific chemical composition of the polymer in the core 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 in the core. Specifically, the degree of crosslinking of the polymer in the core is 0.1-5%. More specifically, it can be 0.5%-1.5%, for example, the degree of crosslinking can be 0.5%, 1%, 1.5%, 2%, etc.

[0061] crosslinking degree

[0062] 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 per cubic centimeter of crosslinking points. The degree of crosslinking can be determined by various methods, such as tensile testing, swelling testing, thermogravimetric analysis, and differential scanning calorimetry.

[0063] For example, the degree of crosslinking of composite particles can be reflected by the molar ratio of crosslinking agent in the raw materials that form the composite particles.

[0064] In some embodiments, the fibers can be fibers with a relatively uniform diameter distribution. In this application, a relatively uniform diameter distribution specifically means that the diameters of fibers with different proportions are not significantly different. In other words, the difference between the largest and smallest diameter fibers in the gel electrolyte is small. When the fiber diameter distribution is relatively uniform, it is beneficial to improve the dispersion of the fibers in the system, thereby improving the control of the fibers over the core particle size, and thus facilitating the obtaining of composite particles with sizes that better meet expectations. For example, the absolute value of the difference between Dv90 and Dv10 of the fibers is 30-40 μm.

[0065] In some embodiments, the tensile strength of the polymer in the core can be 5-10 MPa. For example, the tensile strength can be 5 MPa, 6 MPa, 6.5 MPa, 7 MPa, 7.5 MPa, 8 MPa, 8.5 MPa, 9 MPa, or 10 MPa. The tensile strength can be determined according to GB1040-1992.

[0066] 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 liquid absorption and retention properties of the composite particles can be good.

[0067] In some embodiments, the raw materials forming the polymer may include a crosslinking agent and monomers, for example, an initiator, a crosslinking agent, and monomers. The specific types of initiators and crosslinking agents can be selected according to the type of monomer. For example, the initiator can be azobisisobutyronitrile (AIB), and the crosslinking agent can be divinylbenzene. The degree of crosslinking of the obtained polymer can be adjusted by controlling the mass ratio of the crosslinking agent and monomer. For example, the mass ratio Y of the crosslinking agent and 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. Proper control of the ratio of crosslinking agent and monomer can obtain a polymer with a relatively ideal degree of crosslinking. As a result, the formed core can have good liquid absorption and retention properties. For example, a core with a moderate degree of crosslinking can maintain the stability of the composite particles in the electrolyte, avoiding the polymer being dissolved in the electrolyte for a long time due to insufficient crosslinking, which cannot stably maintain the gel state, thus affecting the performance and lifespan of the battery cell using the gel electrolyte. An appropriate degree of crosslinking can also enable the polymer to have sufficient liquid retention.

[0068] In some specific embodiments, the monomers forming the polymer may include at least one of acrylic acid, acrylates, isocyanates, and urea compounds, and the fibers may include cellulose fibers with a diameter of 20-60 nm and a length of 0.4-2 μm. For example, acrylic acid and / or acrylate compounds may be selected as monomers, and an initiator and a crosslinking agent may be added. After uniform dispersion, cellulose fibers are added to form a Pickering emulsion, so as to obtain a gel electrolyte with fibers distributed on the surface and a polymer core through emulsion polymerization.

[0069] Pickering emulsion

[0070] Pickering emulsions are emulsion systems that use solid particles as emulsifiers and other surface-active components to maintain system stability.

[0071] In another aspect of this application, a method for preparing a gel electrolyte is proposed. The method includes: providing a mixture comprising monomers and fibers and stirring to form a Pickering emulsion, thereby obtaining composite particles. These composite particles can be those included in the gel electrolytes described above. Specifically, the composite particles have a core containing a polymer and a surface region covering at least a portion of the surface of the core, the surface region having the fibers. 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 advantages such as ease of operation and low cost.

[0072] In some specific embodiments, when providing a mixture comprising monomers and fibers, an initiator and a crosslinking agent may also be added to the mixture. 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.

[0073] In some examples, the mass ratio of the crosslinking agent to the monomer in the mixture can be 0.001-0.5. 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.

[0074] 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.

[0075] To obtain a more uniformly dispersed mixture, the monomer, initiator, and crosslinking agent can be mixed thoroughly first before adding the fiber material. In some embodiments, the fibers can be pre-dispersed in water before being mixed with the monomer and other components. Stirring the mixture can be achieved using a high-speed shear press, for example, at 4000-5500 rpm. These operations facilitate obtaining a uniformly dispersed Pickering emulsion system.

[0076] In some examples, the Pickering emulsion does not contain an emulsifier. Cellulose and other fibers act as emulsifiers in the system, forming on the polymer surface to maintain the balance at the water-oil interface, ultimately obtaining composite particles that meet the requirements of the gel electrolyte. 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.

[0077] 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 negative 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.

[0078] In another aspect, this application proposes an electrode. This electrode includes a current collector, an electrode active material loaded on the current collector, and the aforementioned gel electrolyte. Thus, this electrode possesses all the features and advantages of the aforementioned gel electrolyte, which will not be repeated here. In general, this electrode can be used in semi-solid-state batteries and exhibits good liquid absorption and retention properties.

[0079] 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.

[0080] 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 composite particles. After drying and other processes, the particle size of the composite particles in the gel electrolyte on the electrode surface can be 0.2-10 μm. When the particle size of the 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.

[0081] In another aspect, this application proposes a battery. This battery includes the electrodes described above. Therefore, 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] Example 1: Preparation of Gel Electrolytes

[0086] 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.

[0087] Disperse 1g of cellulose fibers (50nm in diameter and 2μm in length) evenly in 60mL of deionized water;

[0088] The monomer-containing mixture was added to the cellulose 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.

[0089] The raw materials for Examples 2-15 are shown in Table 1 below. Gel electrolytes were prepared using the same process as in Example 1.

[0090]

[0091] A battery was prepared using the electrolyte obtained in the examples. The battery fabrication process is as follows:

[0092] Negative electrode sheet manufacturing:

[0093] 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 1-15) 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%:0.5%:0.2%. After thorough stirring, the slurry is filtered through a 150-mesh screen. The slurry is coated onto the negative electrode current collector according to the corresponding coating weight. The above electrode sheet is rolled and cut to obtain negative electrode sheets for later use.

[0094] Positive electrode sheet production:

[0095] 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) 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.

[0096] Diaphragm: PE diaphragm is used.

[0097] Electrolyte:

[0098] Ethylene carbonate, methyl ethyl carbonate, diethyl carbonate, and fluoroethylene carbonate were mixed evenly in a volume ratio of 1:1:1:1, and then LiPF6 was added to prepare an electrolyte with a concentration of 1 mol / L.

[0099] Using the gel electrolytes prepared in Examples 1-15 above, battery samples 2-1 to 2-15 were prepared according to the following procedures: Battery fabrication:

[0100] 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:

[0101] 1. Let stand at 25℃ for 30 minutes;

[0102] 2. Charge at a constant current of 1 / 3C to 4.25V;

[0103] 3. Discharge at a constant voltage of 4.25V to 0.05C;

[0104] 4. Let stand for 5 minutes;

[0105] 5. Charge to 2.8V using 1 / 3C DC;

[0106] 6. Let stand for 5 minutes;

[0107] 7. Charge to 2.8V using 0.1C DC;

[0108] 8. Let stand for 5 minutes;

[0109] 9. Charge at a constant current of 0.5C to 3.85V;

[0110] 10. Discharge at a constant voltage of 3.85V to 0.05C;

[0111] 11. Let stand for 5 minutes.

[0112] Comparative Example 1: Secondary Battery

[0113] 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 2-16 is obtained.

[0114] Comparative Example 2: Secondary Battery

[0115] The remaining parameters are the same as those of the secondary battery sample 2-1 prepared in Example 1. The difference is that the raw materials for forming the gel electrolyte include: 15 mL butyl acrylate, 0.015 g azobisisobutyronitrile, and 0.15 g divinylbenzene (without fiber), to obtain battery sample 2-17.

[0116] Comparative Example 3: Secondary Battery

[0117] The remaining parameters are the same as those of the secondary battery sample 2-1 prepared in Example 1. The difference is that no gel electrolyte is added to the negative electrode, but only 1g of cellulose fiber is added to obtain battery sample 2-18.

[0118] The performance of the negative electrode and secondary battery cell of samples 2-1 to 2-18 above was tested, and the specific tests are as follows:

[0119] (1) Liquid absorption capacity test:

[0120] Weigh the negative electrode prepared in the examples and comparative examples as the test material, and record the initial weight as N1; at 25°C, cover the test material with a diaphragm and immerse it in the electrolyte solvent for 24 hours. After standing for the electrolyte on its surface to evaporate, test its mass after liquid absorption as N2, and calculate the liquid absorption rate as (N2-N1) / N1*100%.

[0121] (2) Liquid retention capacity test:

[0122] 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.

[0123] The electrolyte solvent used in the liquid absorption and retention capacity test is the same electrolyte used in secondary batteries.

[0124] (3) Cell DCR test:

[0125] 1. Let the lithium-ion battery stand at 25℃ for 30 minutes;

[0126] 2. Charge at a constant current of 0.33C to 4.25V, then charge at a constant voltage with a cutoff current of 0.05C. At this point, the battery is at 100% SOC. 3. Let stand for 5 minutes at 25℃.

[0127] 4. 0.33C discharge, cutoff current 0.5C;

[0128] 5. Let stand at 25℃ for 1 hour;

[0129] 6. 5C discharge for 30 seconds;

[0130] 7. Let stand at 25℃ for 40 seconds;

[0131] 8. 3.75C constant current charging for 30 seconds;

[0132] 9. Let stand at 25℃ for 1 hour;

[0133] 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; 11. Let stand for 5 minutes at 25℃;

[0134] 12. Discharge at 0.33C, cutoff current 0.9C;

[0135] 13. Let stand at 25℃ for 1 hour;

[0136] 14. 5C discharge for 30 seconds;

[0137] 15. Let stand for 40 seconds at 25℃;

[0138] 16. 3.75C constant current charging for 30 seconds;

[0139] 17. Let stand for 5 minutes at 25℃;

[0140] 18. Detect the DC resistance of a lithium-ion battery at 50% SOC.

[0141] The test results are shown in Table 2 below:

[0142] Table 2

[0143]

[0144]

[0145] Referring to Table 2 above, samples 2-1 to 2-15 of the gel electrolytes prepared using Examples 1-15 of this application all exhibit good liquid absorption and retention properties, and the cell DCR can be maintained at a certain level, indicating that the added gel electrolyte did not significantly affect the electrical performance of the cell. Compared with the gel electrolyte formed directly by butyl acrylate polymerization without the addition of fiber (sample 2-17), the gel electrolytes prepared using Examples 1-15 of this application, samples 2-1 to 2-15, even with a lower monomer content (sample 2-17 did not add 1g of cellulose, and the monomer mass percentage content was higher), also showed a certain degree of improvement in liquid absorption performance.

[0146] 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 and a negative electrode, both having current collectors, at least one of the current collectors of the positive and negative electrodes being loaded with a gel electrolyte, the gel electrolyte comprising composite particles having a core and a surface region covering at least a portion of the surface of the core, the core containing a polymer and the surface region having fibers.

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

3. The secondary battery according to claim 1 or 2, characterized in that, The composite particles satisfy at least one of the following conditions: The mass ratio of the fiber to the polymer in the composite particles is 1:(8-20); The particle size of the composite particles is 0.2-10 μm; The diameter of the fiber is 10-600 nm; The length of the fiber is 0.1-100 μm; The aspect ratio of the fiber is 2-2000.

4. The secondary battery according to claim 3, characterized in that, The fiber has a diameter of 10-500 nm and a length of 0.4-5 μm.

5. The secondary battery according to claim 3, characterized in that, The particle size of the composite particles is 0.2-5 μm.

6. The secondary battery according to any one of claims 1-5, characterized in that, The fiber includes at least one of cellulose fiber, chitin fiber, chitosan fiber, aramid fiber, carbon nanotube, silk fiber, bacterial fiber, and resin fiber.

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

8. The secondary battery according to any one of claims 1-6, characterized in that, The tensile strength of the polymer in the core is 5-10 MPa.

9. The secondary battery according to claim 7, characterized in that, The raw materials for forming the polymer include a crosslinking agent and a monomer, and the mass ratio Y of the crosslinking agent and the monomer satisfies: 0 < Y ≤ 0.

1.

10. The secondary battery according to claim 9, characterized in that, The condition Y satisfies: 0 < Y < 0.

05.

11. The secondary battery according to any one of 1-10, characterized in that, The absolute value of the difference between Dv90 and Dv10 of the fiber is 30-40 μm.

12. The secondary battery according to any one of claims 1-11, characterized in that, The monomers forming the polymer include at least one of acrylic acid, acrylates, isocyanates, and urea compounds. The fibers include cellulose fibers. The cellulose has a diameter of 10-500 nm and a length of 0.4-5 μm.

13. A method for preparing gel electrolytes, characterized in that, include: A mixture comprising monomers and fibers is provided and stirred to form a Pickering emulsion, thereby obtaining composite particles having a core containing a polymer and a surface region covering at least a portion of the surface of the core, the surface region having the fibers.

14. The method according to claim 13, characterized in that, The method satisfies at least one of the following conditions: The mixture includes an initiator and a crosslinking agent; The mixture contains a crosslinking agent, and the crosslinking agent accounts for 0.001-0.5% of the monomer by mass. The content of the monomer in the mixture is not less than 30%; The fibers are pre-dispersed in water and then mixed with the monomers; The mixing was carried out using a high-speed shear machine at 4000-5500 rpm; The Pickering emulsion does not contain emulsifiers; Obtaining the composite particles involves reacting the Pickering emulsion at 50-80°C with stirring for 10-20 hours.

15. An electrode, characterized in that, include: Current collector, and An electrode active material loaded on the current collector, and a gel electrolyte, wherein the gel electrolyte is any one of claims 1-12.

16. The electrode according to claim 14, characterized in that, The electrode is the negative electrode of a lithium-ion battery, and the content of the gel electrolyte in the electrode is 0.01wt%-20wt% of the electrode loading. The particle size of the composite particles in the gel electrolyte is 0.2-10μm.

17. An electrical device, characterized in that, The electrical device includes a secondary battery as described in any one of claims 1-12, the secondary battery being used to provide electrical energy.

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