Gel-state electrolyte, negative pole piece, secondary battery and electric device

Abstract

The invention discloses a gel-state electrolyte, a negative pole piece, a secondary battery and an electric device. The secondary battery comprises an outer package, the outer package comprises a shell and a cover plate, a containing cavity is formed in the shell, and the cover plate is arranged on one side of an opening of the containing cavity; the electrode assembly is located in the containing cavity, the electrode assembly comprises a positive electrode, a negative electrode and a diaphragm located between the positive electrode and the negative electrode, the negative electrode is provided with a gel-state electrolyte, and the gel-state electrolyte comprises polymer imbibition gel and mesoporous particles located in the polymer imbibition gel. The secondary battery adopting the gel-state electrolyte has relatively good dynamic performance.

Description

Technical Field

[0001] This application relates to the field of batteries, specifically to gel electrolytes, negative electrode sheets, secondary batteries, and electrical devices. Background Technology

[0002] In recent years, with the development of materials technology and the promotion of the application of power rechargeable batteries, the market's performance requirements for rechargeable batteries such as lithium-ion batteries have been continuously increasing. As battery capacity and other performance characteristics improve, the volume of the battery components housed inside the rechargeable battery packaging also increases. This makes it easier for electrolyte to leak out between the electrodes under the influence of gravity and cyclic expansion forces, resulting in poor electrolyte wetting of the electrodes. Although this problem can be alleviated to some extent by incorporating structures or materials with liquid absorption and retention capabilities, materials with liquid retention functions, such as gel electrolytes, generally have low ionic conductivity and poor kinetic performance.

[0003] Therefore, current gel electrolytes, negative electrode sheets, secondary batteries, and electrical devices still need improvement. Summary of the Invention

[0004] In view of the above problems, this application provides a solution for setting a gel electrolyte with mesoporous particles inside the battery cell. The mesoporous particles provide ion transport channels for lithium ions, thereby improving the kinetic performance of the secondary battery using the gel electrolyte.

[0005] In one aspect of this application, a secondary battery is provided. The secondary battery includes an outer packaging comprising a shell and a cover, the shell having a receiving cavity, the cover being disposed on the opening side of the receiving cavity; and an electrode assembly located within the receiving cavity, the electrode assembly including a positive electrode, a negative electrode, and a separator located between the positive and negative electrodes, the negative electrode having a gel electrolyte comprising a polymer liquid-absorbing gel and mesoporous particles located within the polymer liquid-absorbing gel. This secondary battery exhibits good kinetic performance.

[0006] According to embodiments of this application, the mesoporous particles include at least one of silica, alumina, MOF, and COF, and the specific surface area of ​​the mesoporous particles is 10–1500 g / m². 2 .

[0007] According to an embodiment of this application, the diameter of the mesoporous particles is 0.05 to 1 μm.

[0008] According to an embodiment of this application, the mass ratio of the mesoporous particles to the polymer liquid-absorbing gel is M, where 0 < M ≤ 2.

[0009] According to an embodiment of this application, the negative electrode includes an active layer, and the content of the gel electrolyte is 0.01% to 20% based on the total mass of the active layer.

[0010] According to an embodiment of this application, the gel electrolyte is located at least on the side of the negative electrode close to the negative electrode post, the active layer includes negative electrode active particles, and the gel electrolyte is located between the negative electrode active particles.

[0011] According to embodiments of this application, the polymer liquid-absorbing gel comprises at least one of acrylate compounds, styrene compounds, acrylonitrile compounds, urea compounds, isocyanate compounds, and acrylamide compounds, and the degree of crosslinking of the polymer liquid-absorbing gel is 0.1-5%.

[0012] According to embodiments of this application, the raw materials for forming the gel electrolyte include monomers, crosslinking agents, and optionally initiators, wherein the crosslinking agent includes divinylbenzene; and the initiator includes at least one of sodium persulfate, potassium persulfate, ammonium persulfate, and azobisisobutyronitrile.

[0013] According to embodiments of this application, the mass of the crosslinking agent is 0.01% to 20% of the mass of the monomer.

[0014] According to an embodiment of this application, the cover plate has a positive electrode and a negative electrode, the positive electrode and the positive electrode are electrically connected, the negative electrode and the negative electrode are electrically connected, and the gel electrolyte is located at least on the side of the negative electrode close to the negative electrode.

[0015] In another aspect, this application proposes a negative electrode sheet. The negative electrode sheet includes: a current collector, and an active layer located on the surface of the current collector. The active layer includes negative electrode active particles and a gel-like electrolyte, the gel-like electrolyte being located between the negative electrode active particles. The gel-like electrolyte includes a polymer liquid-absorbing gel and mesoporous particles located within the polymer liquid-absorbing gel. This negative electrode sheet exhibits good kinetic performance.

[0016] According to embodiments of this application, the polymeric liquid-absorbing gel comprises at least one of acrylate compounds, styrene compounds, acrylonitrile compounds, urea compounds, isocyanate compounds, and acrylamide compounds; and / or the mesoporous particles comprise at least one of silica, alumina, MOF, and COF, wherein the specific surface area of ​​the mesoporous particles is 10–1500 g / m². 2 ; and / or the diameter of the mesoporous particles is 0.05 to 1 μm; and / or the content of the gel electrolyte is 0.01% to 20% based on the total mass of the active layer.

[0017] In another aspect, this application proposes a gel electrolyte. The gel electrolyte comprises a polymeric liquid-absorbing gel and mesoporous particles located within the polymeric liquid-absorbing gel. This gel electrolyte can improve the kinetic performance of cells utilizing it.

[0018] According to embodiments of this application, the polymeric liquid-absorbing gel comprises at least one of acrylate compounds, styrene compounds, acrylonitrile compounds, urea compounds, isocyanate compounds, and acrylamide compounds; and / or the mesoporous particles comprise at least one of silica, alumina, MOF, and COF, wherein the specific surface area of ​​the mesoporous particles is 10–1500 g / m². 2 ; and / or the diameter of the mesoporous particles is 0.05 to 1 μm; and / or the raw materials forming the polymer liquid-absorbing gel include a crosslinking agent and a monomer, wherein the mass of the crosslinking agent is 0.01% to 20% of the mass of the monomer.

[0019] 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

[0020] 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:

[0021] Figure 1 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0022] Figure 2 for Figure 1 An exploded view of a secondary battery according to one embodiment of this application is shown.

[0023] Figure 3 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to an embodiment of this application.

[0024] Figure 4 This is a schematic diagram of the liquid-absorbing composite particle structure of 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 groups" refers to two or more (including two groups), 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] As mentioned earlier, with the increasing performance requirements of secondary batteries such as lithium-ion batteries, the electrode arrangement within these batteries is becoming increasingly dense. Consequently, the electrolyte is prone to leakage between the electrodes under the influence of gravity and cyclic expansion forces, leading to poor electrolyte wetting and lithium plating. These problems can be mitigated to some extent by designing the electrode and separator structures or adding gel electrolytes. However, adopting methods such as three-dimensional electrode structures or modifying the separator generally sacrifices the cell's energy density, while using gel electrolytes can easily degrade lithium-ion transport performance: gel electrolytes that swell after absorbing electrolyte often lack functional groups or structures capable of conducting lithium ions.

[0033] The gel electrolyte, electrode, and secondary battery proposed in this application utilize a gel electrolyte with mesoporous particles and polymer liquid-absorbing gel. The pores of the mesoporous particles can be used to provide transport channels for solvated lithium ions after the gel electrolyte adsorbs the electrolyte, thereby improving the kinetic performance.

[0034] The electrodes and batteries disclosed in this application can be used in electrical devices such as vehicles, ships, or aircraft. A power supply system for such an electrical device can be constructed using the battery cells and batteries disclosed in this application, which helps to improve the safety performance of the power supply system.

[0035] In a first aspect, this application discloses a secondary battery. The secondary battery includes an outer packaging and an electrode assembly located within the outer packaging. The outer packaging includes a shell and a cover, the shell having a receiving cavity, and the cover being disposed on the opening side of the receiving cavity. The electrode assembly, located within the receiving cavity, includes a positive electrode, a negative electrode, and a separator located between the positive and negative electrodes. The negative electrode has a gel-like electrolyte. The gel-like electrolyte includes a polymeric liquid-absorbing gel and mesoporous particles located within the polymeric liquid-absorbing gel. The secondary battery using this gel-like electrolyte exhibits good kinetic performance.

[0036] In some embodiments, the secondary battery may further include an electrolyte, and the outer packaging of the secondary battery may be used to encapsulate the electrode assembly and the electrolyte.

[0037] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, aluminum shell, or steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate. This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 This is an example of a square-structured secondary battery 1.

[0038] In some implementations, refer to Figure 2 The outer packaging may include a housing 11 and a cover plate 13. The housing 11 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates forming a receiving cavity. The housing 11 has an opening communicating with the receiving cavity, and the cover plate 13 can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode, and separator can be formed into an electrode assembly 12 by a winding process or a stacking process. The electrode assembly 12 is encapsulated within the receiving cavity. The electrolyte is immersed in the electrode assembly 12, and the negative electrode has a gel electrolyte. The secondary battery 1 may contain one or more electrode assemblies 12, which can be selected by those skilled in the art according to specific practical needs.

[0039] refer to Figure 4 The negative electrode of the secondary battery electrode assembly proposed in this application has a gel electrolyte. The negative electrode may include a current collector 100 and an active layer 200, wherein the active layer 200 contains negative electrode active particles 210 and a gel electrolyte. Specifically, the gel electrolyte includes a polymer liquid-absorbing gel 210 and mesoporous particles 20 located within the polymer liquid-absorbing gel 210. After the gel electrolyte adsorbs the electrolyte, the electrolyte enters the pores of the mesoporous particles 20, thereby providing a transport channel for solvated lithium ions and improving the ion transport performance of the polymer liquid-absorbing gel.

[0040] According to embodiments of this application, the polymeric liquid-absorbing gel may include at least one of acrylate compounds, styrene compounds, acrylonitrile compounds, urea compounds, isocyanate compounds, and acrylamide compounds. For example, it may include polymers, copolymers, and / or derivatives of one or more of acrylates, styrene, acrylonitrile, urea, and isocyanates.

[0041] derivative

[0042] 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, polyacrylate derivatives are polymers with polyacrylate as the main structure, containing one or more substituted functional groups, or polymers with other monomer segments by replacing some acrylate monomers in the polymer.

[0043] copolymer

[0044] 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.

[0045] Polymer-absorbing gels significantly influence the liquid absorption and retention capabilities of gel-state electrolytes. Polymer-absorbing gels formed from the aforementioned materials exhibit good electrolyte adsorption capacity and can retain the adsorbed electrolyte within the polymer chains or network structure of the gel, thus possessing excellent liquid retention capabilities. For example, monomers and polymers containing ester groups, through cross-linking, can yield polymers with good swelling properties, thereby exhibiting good localized liquid absorption and retention capabilities. 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.

[0046] The gel electrolyte proposed in this application can further regulate the adsorption and retention capacity of the gel electrolyte for electrolyte by adjusting the types of polymers and / or monomers constituting the polymer liquid-absorbing gel, as well as the surface morphology of the mesoporous particles, thus further improving the performance of the gel electrolyte. For example, according to some embodiments of this application, the degree of crosslinking of the polymer liquid-absorbing gel can be 0.1% to 5%. Polymers with the above degree of crosslinking have good stability and good liquid absorption and retention capacity. Therefore, on the one hand, they can relatively stably "lock" the electrolyte at the negative electrode, alleviating the problem of electrolyte discharge caused by gravity, cyclic expansion force, etc. On the other hand, polymer liquid-absorbing gels with the above degree of crosslinking can form an organic whole with mesoporous particles, resulting in better overall mechanical properties and stability of the gel electrolyte.

[0047] crosslinking degree

[0048] 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.

[0049] In this application, the degree of crosslinking of the polymer liquid-absorbing gel can be determined by the mass ratio of crosslinking agent added to the raw materials. Specifically, in this application, the degree of crosslinking of the gel electrolyte is 0.1-5%, that is, the mass ratio of crosslinking agent added to the raw materials forming the gel electrolyte is 0.1-5%.

[0050] In some embodiments, the polymer forming the polymeric liquid-absorbing gel can be a cross-linked polymer. Specifically, a cross-linked polymer can be obtained by adding a cross-linking agent to the raw materials for synthesizing the polymeric liquid-absorbing gel. 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 for synthesizing the polymeric liquid-absorbing gel 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 selected from at least one of sodium sulfate, potassium persulfate, ammonium persulfate, and azobisisobutyronitrile. The weight and amount of the initiator can affect the chain length of the formed polymer; polymers with appropriate chain lengths have better liquid absorption and retention properties. For example, the mass ratio of initiator to monomer can be 0.5% to 1.5%.

[0051] Crosslinking agents can be selected from divinylbenzene, etc. The degree of crosslinking of the obtained polymer can be adjusted by controlling the mass ratio of the crosslinking agent to the monomer. For example, the mass of the crosslinking agent can be 0.01% to 20% of the monomer mass, specifically 0.01%, 0.5%, 1%, 3%, 5%, 8%, 10%, 13%, 15%, 18%, or 20%. Proper control of the crosslinking agent to monomer ratio can yield a polymer with a relatively ideal degree of crosslinking. The resulting polymer can have good liquid absorption and retention properties. For example, a polymer with a moderate degree of crosslinking can maintain the stability of the polymer gel in the electrolyte, avoiding the polymer being dissolved in the electrolyte for a long time due to insufficient crosslinking, thus preventing it from maintaining a stable gel state. It can also alleviate the decrease in liquid absorption performance caused by excessive crosslinking. In other words, an appropriate degree of crosslinking can also give the polymer sufficient liquid retention.

[0052] In some embodiments, the specific chemical composition of the polymer in the polymer-absorbing gel can be selected according to the requirements of the liquid absorption and retention performance 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 0.1–5%, more specifically, it can be 0.5–1.5%.

[0053] In some embodiments, to further improve the performance of the prepared polymer liquid-absorbing gel, the raw materials forming the polymer liquid-absorbing gel may also include components such as dispersants. For example, polyvinylpyrrolidone or similar substances can be selected for auxiliary dispersion, and a gel with electrolyte adsorption and swelling function can be formed by means such as emulsion polymerization.

[0054] In some embodiments, the tensile strength of the polymer liquid-absorbing gel can be 1-5 MPa. Specifically, it can be 1 MPa, 2 MPa, 2.5 MPa, 3 MPa, 3.5 MPa, 4 MPa, 4.5 MPa, or 5 MPa. In this application, the tensile strength can be determined by the method in GB1040-1992. When the above parameters of the polymer liquid-absorbing gel meet the requirements, the polymer liquid-absorbing gel can maintain a good semi-solid state after absorbing electrolyte, and the liquid absorption and retention properties of the polymer liquid-absorbing gel can be good.

[0055] In this application, the specific chemical composition of the mesoporous particles can be selected according to the performance requirements of the gel electrolyte. For example, the material of the mesoporous particles may include at least one of silica, alumina, MOF, and COF, which have a mesoporous structure. Alumina and silica particles have the advantages of being relatively inexpensive and widely available. Using metal-rich inorganic particles such as MOF and COF can further improve the orderliness of the pore structure in the mesoporous structure and enhance the conductivity of the gel electrolyte by utilizing metal elements.

[0056] In some embodiments, to further improve the liquid absorption performance of the gel electrolyte, the mesoporous particles, in addition to having a mesoporous structure, may also possess a certain amount of macropores or micropores. This can further improve the wettability of the electrolyte to the inorganic mesoporous particles and assist in enhancing the liquid absorption and retention performance of the gel electrolyte. Specifically, the specific surface area of ​​the mesoporous particles can be 10–1500 g / m². 2 For example, 1000-1300g / m 2 For example, it can be 10g / m³. 2 20g / m 2 30g / m 2 50g / m 2 80g / m 2 100g / m 2 200g / m 2 300g / m 2 500g / m 2 800g / m 2 1000g / m 2 1200g / m 2 1300g / m 2 Or 1500g / m 2 Specifically, it can be 1200g / m 2 When the specific surface area of ​​mesoporous particles is within the above range, they can maintain good liquid absorption performance and ensure that the mechanical properties of the mesoporous particles meet the requirements of processes such as electrode cold pressing, thus mitigating the negative impacts caused by breakage of mesoporous particles during cold pressing.

[0057] In some embodiments, the particle size of the mesoporous particles can be 0.03–0.5 μm. For example, it can be 30 nm, 50 nm, 100 nm, or 500 nm. Mesoporous particles within this particle size range can form a gel electrolyte with the aforementioned polymer, and their distribution within the polymer absorbent gel can be relatively uniform. Furthermore, mesoporous particles within the above particle size range can also exhibit better conductivity: the electrolyte can adequately wet the mesoporous particles, thereby providing better transport channels for solvated ions.

[0058] In this application, the particle size of the mesoporous particles can be the particle size of the majority or most particles in the mesoporous particles, or the average particle size of the mesoporous particles. For example, it can be the Dv50 particle size, meaning that 50% of the particles in the mesoporous particles have a diameter below this value. In some examples, the mesoporous particles can be loaded onto an electrode sheet together with the electrode active material, and the particle size of the mesoporous particles is measured by observation, such as a longitudinal section, after they have been loaded onto the electrode sheet and dried. For example, the Dv50 particle size can be determined by information from scanning electron microscope (SEM) images. The average particle size can be determined using software such as Avizo 3D or by particle size analysis methods based on the SEM images. Alternatively, multiple mesoporous particles can be selected within the field of view of one or more SEM images, and their particle sizes can be measured individually. The average value of the obtained multiple particle sizes is determined as the particle size of the mesoporous particles. The number of selected particles can be 10 or more, specifically 20 or more, 30 or more, or 50 or more.

[0059] In some embodiments, the gel electrolyte may contain one or more mesoporous particles. For example, it may contain multiple mesoporous particles with different chemical compositions, or it may contain multiple mesoporous particles with the same chemical composition but different specific surface areas. This allows for more precise control of the liquid absorption performance of the gel electrolyte, enabling it to meet the requirements of different secondary batteries.

[0060] In some embodiments, the content of mesoporous particles and polymeric liquid-absorbing gel in the gel electrolyte can satisfy the following: the mass ratio of mesoporous particles to polymeric liquid-absorbing gel is M, 0 < M ≤ 2, for example, M can be 0.05, 0.1, 0.5, 1, 1.5 or 2. When the mass ratio M of the two meets the above requirements, it is beneficial to form a gel electrolyte with sufficient ion transport pathways inside, and to maintain good liquid absorption and retention properties of the gel electrolyte.

[0061] In some examples, the content of mesoporous particles and polymeric liquid-absorbing gels can be determined by methods such as thermogravimetric analysis (TG). For instance, TG can be used to determine the change in mass of the gel electrolyte as a function of temperature under programmed temperature control. Since the mesoporous particles and polymeric liquid-absorbing gels in the gel electrolyte decompose at different temperatures, their content can be determined from the obtained thermogravimetric curve (sample weight versus temperature or time).

[0062] In some embodiments, to further improve the performance of the obtained gel electrolyte, mesoporous particles with electronegative functional group modifications on their surface can be selected, or mesoporous particles that have undergone pre-lithiation / lithium salt functionalization treatment can be selected. These treatments are more conducive to the electrolyte fully wetting the mesoporous particles, enhancing their ability to conduct lithium ions as transport channels, thereby further improving the lithium-ion transport kinetics of cells, batteries, etc., utilizing this gel electrolyte.

[0063] In this application, the pre-lithiation / lithium salt functionalization treatment can be achieved by immersing mesoporous particles in a lithium salt solution. For example, lithium salt and mesoporous particles can be mixed in solution.

[0064] According to embodiments of this application, the specific content of the gel electrolyte in the active layer can be adjusted according to the specific conditions of the secondary battery. For example, based on the total mass of the active layer, the content of the gel electrolyte can be 0.01% to 20%. For example, it can be 1-5%, specifically 1%, 2%, 3%, 4%, 5%, etc. When the content of the gel electrolyte is within the above range, it can better perform the adsorption and retention function of the electrolyte.

[0065] The specific placement of the gel electrolyte in the negative electrode can be adjusted according to the volume of the electrode assembly in the secondary battery, the density of folded or wound electrodes in the assembly, and the capacity of the secondary battery. In some embodiments, the cover plate of the secondary battery may have a positive electrode post and a negative electrode, with the positive electrode and the positive electrode post electrically connected, and the negative electrode and the negative electrode post electrically connected. When the capacity of the secondary battery is in the range of 2.5Ah, the gel electrolyte can be located at least on the side of the negative electrode near the negative electrode post. For example, the gel electrolyte can be placed at the corner position on the side of the negative electrode near the negative electrode post. The above-mentioned position is more prone to the aforementioned electrolyte leakage phenomenon.

[0066] In some embodiments, the active layer includes negative electrode active particles, such as carbon materials, silicon-based negative electrode active materials, silicon-carbon negative electrode active materials, etc. The carbon materials may include natural graphite particles, artificial graphite particles, etc. A gel-state electrolyte may be located between the negative electrode active particles. This better enhances the kinetic performance.

[0067] In another aspect of this application, a negative electrode is provided. In some embodiments, the negative electrode can be the negative electrode in the aforementioned secondary battery. For example, refer to... Figure 4 The negative electrode may have a current collector 100 and an active layer 200, wherein the active layer 200 contains negative electrode active particles 210 and a gel electrolyte. The mesoporous particles 20 located in the polymer liquid-absorbing gel 210 can provide transport channels for solvated lithium ions by utilizing the pore structure of the mesoporous particles 20 after the gel electrolyte adsorbs the electrolyte, thereby improving the ion transport performance of the polymer liquid-absorbing gel.

[0068] This negative electrode can possess all the characteristics and advantages of the negative electrode of the aforementioned secondary battery. In general, this negative electrode has good stability, strong resistance to electrolyte discharge, and the gel electrolyte has good ion transport performance.

[0069] In another aspect, this application proposes a gel electrolyte. The gel electrolyte comprises a polymeric liquid-absorbing gel and mesoporous particles located within the polymeric liquid-absorbing gel. This gel electrolyte can be present in the negative electrode of the aforementioned secondary battery. This gel electrolyte exhibits good ion transport performance.

[0070] In this application, the polymeric liquid-absorbing gel and mesoporous particles in the gel electrolyte can possess all the characteristics and advantages of the corresponding components in the gel electrolyte of the aforementioned secondary battery. Therefore, this gel electrolyte can have good liquid absorption and retention properties, as well as good ion transport properties.

[0071] In another aspect, this application proposes an electrical device. This electrical device includes the aforementioned secondary battery for providing electrical energy. Therefore, this electrical device possesses all the features and advantages of the aforementioned secondary battery, which will not be repeated here.

[0072] Figure 3 Here is an example of an electrical device 2. This electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the secondary battery for this electrical device, a battery pack or battery module can be used.

[0073] 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.

[0074] 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.

[0075] Example 1 Polymer Liquid Absorption Gel

[0076] Mix 15 mL of butyl acrylate, 0.015 g of azobisisobutyronitrile initiator, and 0.5 g of divinylbenzene crosslinking agent evenly to prepare solution ①; ② Take 60 mL of deionized water and disperse 0.5 g of polyvinylpyrrolidone dispersant evenly, and record this as solution ②; At 70 °C, slowly add solution ① to solution ② using a peristaltic pump, and stop the reaction at 70 °C for 12 h under nitrogen protection.

[0077] The raw materials for Examples 2-4 are shown in Table 1 below. The gel electrolytes were prepared using the same process as in Example 1.

[0078] Table 1

[0079]

[0080] Using the negative electrode sheets and battery components prepared in Examples 1-4 above, battery samples 2-1 to 2-4 were prepared according to the following operations:

[0081] Battery making:

[0082] Negative electrode sheet manufacturing:

[0083] The dispersant for the negative electrode is uniformly dispersed in an aqueous solution. The conductive agent for the negative electrode, the active material for the negative electrode, the polymer liquid-absorbing gel obtained in Examples 1-14, and the mesoporous material are pre-mixed and added to the above aqueous solution. After stirring for a period of time, the binder for the negative electrode is added to form a slurry. The composition and amount of the polymer liquid-absorbing gel and the mesoporous material are detailed in Table 1 below. The ratio of the active material for the negative electrode, the gel electrolyte, the binder, the dispersant, the conductive agent, and the 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 and coated onto the current collector for the negative electrode according to the corresponding coating weight. The above electrode sheets are rolled and cut to obtain negative electrode sheets for later use.

[0084] Positive electrode sheet production:

[0085] 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.

[0086] Separator: The separator is made of PE coated with CCS (ceramic coating) on ​​both sides.

[0087] 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.

[0088] 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:

[0089] 1. Let the lithium-ion battery stand at 25℃ for 5 minutes;

[0090] 2. Charge to 4.25V using a 1 / 3C constant current method;

[0091] 3. 4.25V constant voltage charging, cut-off current 0.05C;

[0092] 4. Let stand for 5 minutes at 25℃;

[0093] 5. Discharge at 1 / 3C constant current to 4.25V;

[0094] 6. Let stand for 5 minutes;

[0095] 7. Discharge at a constant current of 0.1C to 2.8V;

[0096] 8. Let stand for 5 minutes;

[0097] 9. Charge at a constant current of 0.5C to 3.85V;

[0098] 10. Maintain a constant voltage of 3.85V to 0.05C;

[0099] 11. Let stand for 5 minutes.

[0100] Comparative Example 1

[0101] The remaining parameters are the same as in Example 1, except that no mesoporous particles were added to the gel electrolyte. Battery samples 2-5 were obtained.

[0102] Comparative Example 2

[0103] The remaining parameters were the same as in Example 1, except that only mesoporous particles were added to the slurry, and no polymer was added. Battery samples 2-6 were obtained.

[0104] The differences between the components and examples in Comparative Examples 1 and 2 are detailed in Table 1 above.

[0105] The negative electrodes of the above samples 2-1 to 2-4, comparative examples 1 and 2, as well as the liquid absorption and retention capacity and cell performance of the secondary batteries, were tested. The specific tests are as follows:

[0106] (1) Liquid absorption capacity test:

[0107] The negative electrode prepared from samples 2-1 to 2-4 above 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%.

[0108] (2) Liquid retention capacity test:

[0109] 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.

[0110] The electrolyte solvent used in the liquid absorption and retention capacity test is the same electrolyte used in secondary batteries.

[0111] (3) Cell DCR:

[0112] 1. Let the lithium-ion battery stand at 25℃ for 30 minutes;

[0113] 2. Charge at a constant current of 0.33C to 3.65V, 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℃.

[0114] 4. 0.33C discharge, cutoff current 0.5C;

[0115] 5. Let stand at 25℃ for 1 hour;

[0116] 6. 5C discharge for 30 seconds;

[0117] 7. Let stand at 25℃ for 40 seconds;

[0118] 8. 3.75C constant current charging for 30 seconds;

[0119] 9. Let stand at 25℃ for 1 hour;

[0120] 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;

[0121] 11. Let stand for 5 minutes at 25℃;

[0122] 12. Discharge at 0.33C, cutoff current 0.9C;

[0123] 13. Let stand at 25℃ for 1 hour;

[0124] 14. 5C discharge for 30 seconds;

[0125] 15. Let stand for 40 seconds at 25℃;

[0126] 16. 3.75C constant current charging for 30 seconds;

[0127] 17. Let stand for 5 minutes at 25℃;

[0128] 18. Detect the DC resistance of a lithium-ion battery at 50% SOC.

[0129] (4) Cyclic performance test:

[0130] At 25℃, the battery cell was charged and discharged at a charge / discharge rate of 1C / 1C, and the number of cycles was recorded when the cell's SOC decayed to 80%.

[0131] The test results are shown in Table 2 below:

[0132] Table 2

[0133]

[0134]

[0135] As shown in Table 2 above, the embodiments of this application exhibit both good liquid absorption and good liquid retention properties, indicating that the gel electrolyte of this application can maintain a certain degree of stability during long-term cycling. Furthermore, the above embodiments also demonstrate low DCR and a certain number of cycles, indicating that the gel electrolyte and the secondary battery exhibit good overall performance.

[0136] 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: The outer packaging includes a shell and a cover, the shell having a receiving cavity, and the cover being disposed on the opening side of the receiving cavity; An electrode assembly is located within the receiving cavity. The electrode assembly includes a positive electrode, a negative electrode, and a membrane located between the positive and negative electrodes. The negative electrode has a gel-like electrolyte. The gel electrolyte comprises a polymer-absorbing gel and mesoporous particles located within the polymer-absorbing gel.

2. The secondary battery according to claim 1, characterized in that, The mesoporous particles include at least one of silica, alumina, MOF, and COF. The specific surface area of ​​the mesoporous particles is 10–1500 g / m². 2 .

3. The secondary battery according to claim 2, characterized in that, The diameter of the mesoporous particles is 0.05 to 1 μm.

4. The secondary battery according to any one of claims 1-3, characterized in that, The mass ratio of the mesoporous particles to the polymer liquid-absorbing gel is M, where 0 < M ≤ 2.

5. The secondary battery according to any one of claims 1-4, characterized in that, The negative electrode includes an active layer, and the content of the gel electrolyte is 0.01% to 20% based on the total mass of the active layer.

6. The secondary battery according to claim 5, characterized in that, The active layer includes negative electrode active particles, and the gel electrolyte is located between the negative electrode active particles.

7. The secondary battery according to any one of claims 1-6, characterized in that, The polymeric liquid-absorbing gel comprises at least one of acrylate compounds, styrene compounds, acrylonitrile compounds, urea compounds, isocyanate compounds, and acrylamide compounds. The degree of crosslinking of the polymer liquid-absorbing gel is 0.1% to 5%.

8. The secondary battery according to any one of claims 1-7, characterized in that, The raw materials for forming the gel electrolyte include monomers, crosslinking agents, and optionally initiators. The crosslinking agent includes divinylbenzene; The initiator includes at least one of sodium persulfate, potassium persulfate, ammonium persulfate, and azobisisobutyronitrile.

9. The secondary battery according to claim 8, characterized in that, The mass of the crosslinking agent is 0.01% to 20% of the mass of the monomer.

10. The secondary battery according to any one of claims 1-9, characterized in that, The cover plate has a positive electrode and a negative electrode, the positive electrode and the positive electrode post are electrically connected, the negative electrode and the negative electrode post are electrically connected, and the gel electrolyte is located at least on the side of the negative electrode close to the negative electrode post.

11. A negative electrode sheet, characterized in that, include: Current collector, and An active layer is located on the surface of the current collector. The active layer includes negative electrode active particles and a gel electrolyte. The gel electrolyte is located between the negative electrode active particles. The gel electrolyte includes a polymer liquid-absorbing gel and mesoporous particles located within the polymer liquid-absorbing gel.

12. The negative electrode sheet according to claim 11, characterized in that, The polymer absorbent gel comprises at least one of acrylate compounds, styrene compounds, acrylonitrile compounds, urea compounds, isocyanate compounds, and acrylamide compounds; and / or The mesoporous particles include at least one of silica, alumina, MOF, and COF, and the specific surface area of ​​the mesoporous particles is 10–1500 g / m². 2 ; and / or The diameter of the mesoporous particles is 0.05–1 μm; and / or Based on the total mass of the active layer, the content of the gel electrolyte is 0.01% to 20%.

13. A gel electrolyte, characterized in that, It includes a polymer liquid-absorbing gel and mesoporous particles located within the polymer liquid-absorbing gel.

14. The gel electrolyte according to claim 13, characterized in that, The polymer absorbent gel comprises at least one of acrylate compounds, styrene compounds, acrylonitrile compounds, urea compounds, isocyanate compounds, and acrylamide compounds; and / or The mesoporous particles include at least one of silica, alumina, MOF, and COF, and the specific surface area of ​​the mesoporous particles is 10–1500 g / m². 2 ; and / or The diameter of the mesoporous particles is 0.05–1 μm; and / or The raw materials for forming the polymer liquid-absorbing gel include a crosslinking agent and a monomer, wherein the mass of the crosslinking agent is 0.01% to 20% of the mass of the monomer.

15. An electrical appliance, characterized in that, The electrical device includes a secondary battery as described in claims 1-10, the secondary battery being used to provide electrical energy.

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