Gel polymer electrolyte and method for producing the same, battery, method for charging and discharging battery, and electrical device

Abstract

The present application discloses a gel polymer electrolyte, a method for manufacturing the same, a battery, a method for charging and discharging the battery, and an electrical device. The gel polymer electrolyte has a first state at a first temperature and a second state at a second temperature, and the first and second states are mutually convertible. The first temperature is higher than the second temperature, and the degree of crosslinking of the gel polymer electrolyte in the second state is higher than the degree of crosslinking of the gel polymer electrolyte in the first state. As a result, by using the gel polymer electrolyte of the present application, a battery containing the gel polymer electrolyte maintains high capacity retention and rate performance even after multiple cycles.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to and benefit of patent application No. 202310424149.1, filed with the State Intellectual Property Office of China on April 19, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present application relates to the technical field of secondary batteries, and in particular to a gel polymer electrolyte and a method for producing the same, a battery, a method for charging and discharging the battery, and an electric device. [Background technology]

[0003] Currently available batteries mainly use liquid electrolytes as the ion-conducting medium, which makes them susceptible to accidents if the battery is overcharged, overheated, short-circuited, or subjected to shock.

[0004] Therefore, using a gel polymer electrolyte instead of a liquid electrolyte as an ion-conducting medium is an effective way to reduce the probability of battery failure. However, batteries using conventional gel polymer electrolytes suffer a significant decrease in capacity retention and rate performance after multiple cycles. Summary of the Invention [Problem to be solved by the invention]

[0005] In view of the technical problems existing in the background art, the present application provides a gel polymer electrolyte that aims to solve the problem that a battery containing a gel polymer electrolyte exhibits a significant decrease in capacity retention and rate performance after multiple cycles. [Means for solving the problem]

[0006] To achieve the above object, a first aspect of the present application provides a gel polymer electrolyte having a first state at a first temperature and a second state at a second temperature, wherein the first state and the second state are mutually convertible, the first temperature is higher than the second temperature, and the degree of crosslinking of the gel polymer electrolyte in the second state is higher than the degree of crosslinking of the gel polymer electrolyte in the first state.

[0007] Compared to the prior art, the present application has at least the following beneficial effects: After multiple cycles at the second temperature, gaps form between the battery sheet and the gel polymer electrolyte, causing the battery capacity to continuously deteriorate. However, when the battery is heated to the first temperature, the gel polymer electrolyte undergoes a depolymerization reaction, increasing the mobile phase in the gel polymer electrolyte, which firmly bonds the battery sheet and the gel polymer electrolyte, restoring the battery capacity. Furthermore, increasing the mobile phase in the gel polymer electrolyte improves the ionic conductivity of the gel polymer electrolyte, further improving the rate performance of the battery.

[0008] In some embodiments of the present application, the ratio of the degree of crosslinking of the gel polymer electrolyte in the first state to the degree of crosslinking in the second state is 0.2 to 0.95: 1. By keeping the ratio within the above range, the capacity retention rate and rate performance of the battery at the first temperature can be further improved.

[0009] In some embodiments of the present application, the first temperature is 40° C. or higher, and optionally 40° C. to 120° C. When the temperature is within this range, the gel polymer is in the first state, and the capacity retention rate and rate performance of the battery at the first temperature can be further improved.

[0010] In some embodiments of the present application, the degree of crosslinking of the gel polymer electrolyte in the first state is 20% to 48.5%, and by being within this range, the degree of crosslinking of the gel polymer is relatively low, which can improve the capacity retention rate and rate performance of the battery in the first state.

[0011] In some embodiments of the present application, the second temperature is between -25°C and 35°C.

[0012] In some embodiments of the present application, the degree of cross-linking of the gel polymer electrolyte in the second state is 50% to 99%.

[0013] In some embodiments of the present application, the gel polymer electrolyte further contains an electrolytic solution, and the mass ratio of the electrolytic solution in the gel polymer electrolyte is 60% to 98%. As a result, when the gel polymer electrolyte obtained within the above blending ratio range is used in a battery, the capacity retention rate and rate performance of the battery can be improved.

[0014] In some embodiments of the present application, the gel polymer electrolyte includes a first crosslinking agent and a second crosslinking agent, and the de-crosslinking temperature of the second crosslinking agent is 40° C. or higher, and optionally 40° C. to 120° C. As a result, when the battery is heated to the first temperature, i.e., when the de-crosslinking temperature of the second crosslinking agent is reached, at least a portion of the second crosslinking agent is de-crosslinked, thereby improving the capacity retention rate and rate performance of the battery at the first temperature.

[0015] In some embodiments of the present application, the first crosslinker comprises at least one of an acrylate crosslinker and a conjugated diene.

[0016] In some embodiments of the present application, the acrylate-based crosslinker includes at least one of ethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, trimethylolpropane ethoxylate triacrylate, trimethylolpropane propoxylate triacrylate, ditrimethylolpropane tetraacrylate, pentaerythritol tetraacrylate, pentaerythritol ethoxylate tetraacrylate, dipentaerythritol pentaacrylate, and dipentaerythritol hexaacrylate. This ensures that the gel polymer is not completely uncrosslinked when the battery reaches a first temperature, ensuring that the gel polymer electrolyte can function, thereby improving the capacity retention and rate performance of the battery at the first temperature.

[0017] In some embodiments of the present application, the conjugated diene comprises at least one of divinylbenzene and 1,3-butadiene.

[0018] In some embodiments of the present application, the second crosslinker includes at least one of maleimide and an N-substituted derivative of maleimide, whereby, by using the second crosslinker, at least a portion of the second crosslinker is uncrosslinked when the battery reaches the first temperature, thereby improving the capacity retention rate and rate performance of the battery at the first temperature.

[0019] In some embodiments of the present application, the molar ratio of the first crosslinking agent to the second crosslinking agent is 0.5 to 5: 1. When the ratio of the first crosslinking agent to the second crosslinking agent is within the above range, the capacity retention rate and rate performance of the battery at the first temperature can be improved.

[0020] In some embodiments of the present application, the gel polymer electrolyte further comprises a host material, and the host material monomer comprises at least one of a vinyl group, an epoxy group, an allyl group, an acryloyl group, and a methacryloyl group, so that the host material monomer can crosslink with the first crosslinker and the second crosslinker, respectively, during the process of forming the host material by polymerization, thereby improving the capacity retention rate and rate performance of the battery.

[0021] In some embodiments of the present application, the host material monomer includes at least one of furfuryl methacrylate, ethylene glycol diglycidyl ether, 1,5-hexadiene diepoxide, glycerol propoxylate triglycidyl ether, vinylcyclohexene dioxide, 1,2,7,8-diepoxyoctane, 4-vinylcyclohexene dioxide, butyl glycidyl ether, 1,2-cyclohexanedicarboxylic acid diglycidyl ester, ethylene glycol diglycidyl ether, glycerol triglycidyl ether, and glycidyl methacrylate, whereby the host material monomer can crosslink with the first crosslinker and the second crosslinker, respectively, during polymerization to form the host material, thereby improving the capacity retention and rate performance of the battery.

[0022] A second aspect of the present application is a method for producing a gel polymer electrolyte, comprising: a host material monomer, an initiator, a cross-linking agent, and an electrolyte solution are mixed and then polymerized to obtain a gel polymer electrolyte; The gel polymer electrolyte has a first state at a first temperature and a second state at a second temperature, the first state and the second state being mutually convertible, the first temperature being higher than the second temperature, and the degree of crosslinking of the gel polymer electrolyte in the second state being higher than the degree of crosslinking of the gel polymer electrolyte in the first state.

[0023] Therefore, when the gel polymer electrolyte produced in the present application is used in a battery, after the capacity of the battery has been reduced by multiple cycles, the capacity retention rate and rate performance of the battery can be improved by raising the temperature of the battery to the second temperature.

[0024] In some embodiments of the present application, the crosslinking agent includes a first crosslinking agent and a second crosslinking agent, and the decrosslinking temperature of the second crosslinking agent is 40° C. or higher, and optionally 40° C. to 120° C. As a result, when the battery is heated to the first temperature, i.e., when the decrosslinking temperature of the second crosslinking agent is reached, at least a portion of the second crosslinking agent is decrosslinked, thereby improving the capacity retention rate and rate performance of the battery at the first temperature.

[0025] In some embodiments of the present application, the molar ratio of the monomer of the host material to the crosslinking agent is 1:2 to 10. When a gel polymer electrolyte obtained within the above blending ratio range is used in a battery, the capacity retention rate and rate performance of the battery at the first temperature can be improved.

[0026] A third aspect of the present application provides a battery including the gel polymer electrolyte according to the first aspect of the present application or the gel polymer electrolyte produced by the method according to the second aspect, thereby providing the battery with good capacity retention and rate performance.

[0027] A fourth aspect of the present application is a method for charging and discharging a battery, comprising: the battery includes a gel polymer electrolyte, the gel polymer electrolyte having a first state at a first temperature and a second state at a second temperature, the first state and the second state being mutually convertible, the first temperature being higher than the second temperature, and the degree of crosslinking of the gel polymer electrolyte in the second state being higher than the degree of crosslinking of the gel polymer electrolyte in the first state; If the battery satisfies a first preset condition, charging and discharging the battery at a first temperature; If the battery satisfies a second preset condition, the method charges and discharges the battery at a second temperature.

[0028] This allows the capacity retention rate and rate performance of the battery to be improved by adjusting the temperature of the battery under different conditions.

[0029] In some embodiments of the present application, the first preset condition is that the ratio of the current internal resistance of the battery to the initial internal resistance of the battery is greater than 1.5.

[0030] In some embodiments of the present application, the second preset condition is that the ratio of the current internal resistance of the battery to the initial internal resistance of the battery is 1.5 or less.

[0031] In some embodiments of the present application, the first preset condition is that the discharge rate of the battery is greater than 2 C. In some embodiments of the present application, the second preset condition is that the discharge rate of the battery is less than or equal to 2 C.

[0032] A fifth aspect of the present application provides an electrical device comprising the battery according to the third aspect for supplying electrical energy.

[0033] Additional aspects and advantages of the present application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the present application. [Brief explanation of the drawings]

[0034] Various other benefits and advantages will become apparent to those skilled in the art upon review of the detailed description of the preferred embodiments below. The drawings are only for purposes of illustrating the preferred embodiments and should not be construed as limiting the present application. Also, like reference numerals refer to like elements throughout the drawings. A description of the drawings follows.

[0035] [Figure 1] 1 is a structural schematic diagram of a battery according to an embodiment of the present application. [Figure 2] 1 is a structural schematic diagram of a battery module according to an embodiment of the present application; [Figure 3]1 is a structural schematic diagram of a battery pack according to an embodiment of the present application; [Figure 4] FIG. 4 is an exploded view of FIG. 3. [Figure 5] 1 is a schematic diagram of an embodiment of an electrical device that uses a battery as a power source. DETAILED DESCRIPTION OF THE INVENTION

[0036] The following detailed description will be given of the examples of the technical solution of the present application. The following examples are only used to more clearly explain the technical solution of the present application, and are merely examples, which should not limit the scope of protection of the present application.

[0037] When an "embodiment" is described in this specification, it means that a particular feature, structure, or characteristic described by the embodiment may be included in at least one embodiment of the present application. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it refer to an embodiment that is exclusively independent of or alternative to other embodiments. It is explicitly or implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0038] For the sake of brevity, this specification specifically discloses only a few numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range, and any lower limit can be combined with another lower limit to form an unspecified range, and similarly, any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each point or individual numerical value disclosed individually can itself be used as a lower limit or upper limit, or can be combined with any other point or individual numerical value, or with other lower or upper limits, to form an unspecified range.

[0039] In the description of the examples of this application, the term "and / or" is merely used to explain the relationship between related objects and indicates that there may be three relationships; for example, A and / or B can represent the cases where A exists alone, A and B exist simultaneously, or B exists alone. In addition, the symbol " / " in this specification generally means that the related objects before and after it are in an "or" relationship.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. The terms used herein are only for describing specific examples and are not intended to limit the present application. The terms "comprises," "has," and any variations thereof in the specification, claims, and the above brief description of the drawings of this application are intended to cover the non-exclusive "comprises."

[0041] With technological advances and increased demand for electric vehicles and rechargeable mobile devices, research into secondary batteries, which represent a new energy field, is also progressing rapidly.

[0042] Typically, electrolytes must be dissolved in a solvent to be used as an electrolytic solution. The electrolyte is an ion-conducting medium located between the positive and negative electrodes inside the battery. Currently, most batteries on the market use liquid electrolytes, but liquid ion batteries are prone to problems such as internal short circuits, electrolyte leakage, and combustion during use. To address the above-mentioned risks of liquid ion batteries, researchers have proposed gel polymer electrolytes.

[0043] Gel polymer electrolytes have the advantages of solid electrolytes, such as being less susceptible to short circuits and electrolyte leakage, and also have ionic conductivity at room temperature that meets the requirements of actual applications. Furthermore, gel polymer electrolytes have good processability and allow for flexible and diversified battery designs, which has greatly promoted the development and large-scale application of the battery industry.

[0044] Conventional gel polymer electrolytes have rubber-like elasticity and good processability. The most widely studied gel electrolytes currently include polyethylene oxide (PEO)-based gel electrolytes, polyacrylonitrile (PAN)-based gel electrolytes, polymethyl methacrylate (PMMA)-based gel electrolytes, and polyvinylidene fluoride (PVDF) and its copolymer-based gel electrolytes.

[0045] However, after multiple cycles, batteries containing the above-mentioned gel polymer electrolytes suffer from deterioration of the interfacial contact between the battery electrodes and the gel polymer electrolyte, which reduces the ionic conductivity of the electrolyte and significantly reduces the capacity retention and rate performance of the battery.

[0046] The gel polymer electrolyte used in this application has a first state at a first temperature and a second state at a second temperature, and the first and second states are interchangeable, with the first temperature being higher than the second temperature. The battery operates normally in the second temperature range and is discharged at normal power. During this period, the battery electrolyte is semi-solid, reducing the likelihood of problems such as internal short circuits, electrolyte leakage, and combustion. After the battery capacity has deteriorated, the battery is heated to the first temperature and charged / discharged. During this period, a portion of the gel polymer electrolyte depolymerizes, increasing the fluidity of the gel polymer electrolyte, lowering the internal resistance and increasing the ionic conductivity. By adjusting the operating temperature of the battery under different conditions, a corresponding target charge / discharge temperature can be selected according to the specific battery conditions, providing high capacity retention and rate performance.

[0047] The gel polymer electrolytes disclosed in the examples of the present application can be applied to gel batteries, i.e., semi-solid batteries. The batteries disclosed in the examples of the present application can be used in various energy storage systems that use batteries as a power source or as an energy storage element. Examples of the electric devices include, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric motorcycles, electric vehicles, boats, and aircraft. Examples of the electric toys include, for example, game consoles, electric vehicle toys, electric boat toys, and electric airplane toys, and examples of the aircraft include airplanes, rockets, space shuttles, and spacecraft.

[0048] A first aspect of the present application proposes a gel polymer electrolyte having a first state at a first temperature and a second state at a second temperature, wherein the first state and the second state are mutually convertible, the first temperature is higher than the second temperature, and the degree of crosslinking of the gel polymer electrolyte in the second state is higher than the degree of crosslinking of the gel polymer electrolyte in the first state.

[0049] The degree of crosslinking is a physical quantity indicating the degree of crosslinking of a polymer, i.e., the percentage of crosslinked structural units Nc in a crosslinked chain to the total structural units N. The degree of crosslinking can be measured using a nuclear magnetic resonance crosslink density meter, and specifically, in the examples of the present application, it can be measured using an IIC XLDS-15 crosslink density spectrometer.

[0050] When a polymer is crosslinked, its fluidity deteriorates. Therefore, in the present application, since the degree of crosslinking at the second temperature is higher than the degree of crosslinking at the first temperature, the fluidity of the gel polymer electrolyte at the second temperature is worse than the fluidity at the first temperature. In other words, the gel polymer electrolyte has a higher degree of crosslinking and therefore worse fluidity at the second temperature, which is lower, than at the first temperature, which is higher.

[0051] Compared to the prior art, the present application has at least the following beneficial effects: After multiple cycles at the second temperature, gaps form between the battery sheet and the gel polymer electrolyte, resulting in continuous degradation of battery capacity; however, when the battery is heated to the first temperature, the gel polymer electrolyte undergoes a depolymerization reaction, i.e., the degree of cross-linking of the gel polymer electrolyte decreases. At this time, the mobile phase in the gel polymer electrolyte increases, firmly bonding the battery sheet and the gel polymer electrolyte, restoring the battery capacity. Furthermore, the increase in the mobile phase in the gel polymer electrolyte improves the ionic conductivity of the gel polymer electrolyte, further improving the rate performance of the battery.

[0052] In some embodiments of the present application, the ratio of the degree of crosslinking of the gel polymer electrolyte in the first state to the degree of crosslinking in the second state is 0.2 to 0.95:1, and may be, for example, 0.3 to 0.9:1, 0.4 to 0.8:1, 0.5 to 0.7:1, etc. By having the ratio within the above range, the degree of crosslinking of the gel polymer electrolyte in the first state is low and the degree of crosslinking in the second state is high, and the capacity retention rate and rate performance of the battery at the first temperature can be further improved.

[0053] In some embodiments of the present application, the first temperature is 40° C. or higher. For example, the first temperature may be 40° C. to 120° C., 45° C. to 120° C., 45° C. to 110° C., 45° C. to 100° C., 45° C. to 90° C., 50° C. to 80° C., 55° C. to 75° C., or 60° C. to 70° C. By keeping the temperature within this range, the degree of crosslinking of the gel polymer is relatively low, and the mobile phase increases, thereby further improving the capacity retention rate and rate performance of the battery at the first temperature.

[0054] In some embodiments of the present application, the degree of crosslinking of the gel polymer electrolyte in the first state is 20% to 48.5%, and may be, for example, 22% to 48.5%, 25% to 45%, 28% to 44%, 30% to 40%, 35% to 39%, etc. By keeping the degree of crosslinking within the above range, the degree of crosslinking of the gel polymer is relatively low, the mobile phase is increased, and the sheet and the gel polymer electrolyte are firmly bonded, thereby improving the capacity retention rate and rate performance of the battery at the first temperature.

[0055] In some embodiments of the present application, the second temperature is −25° C. to 35° C. For example, it may be −22° C. to 35° C., −20° C. to 30° C., −15° C. to 25° C., −10° C. to 20° C., −5° C. to 15° C., 0° C. to 10° C., or 3° C. to 8° C. By keeping the temperature within the above range, the degree of crosslinking of the gel polymer is relatively high, and the probability of an internal short circuit, electrolyte leakage, combustion, or the like occurring in the battery can be reduced.

[0056] In some embodiments of the present application, the degree of cross-linking of the gel polymer electrolyte in the second state is 50% to 99%, and may be, for example, 52% to 99%, 55% to 95%, 60% to 90%, 65% to 85%, 70% to 80%, etc. By keeping the degree of cross-linking within the above range, it is possible to reduce the probability of internal short circuits, electrolyte leakage, combustion, etc. occurring in the battery.

[0057] In some embodiments of the present application, the gel polymer electrolyte further contains an electrolytic solution, and the mass ratio of the electrolytic solution in the gel polymer electrolyte is 60% to 98%, and may be, for example, 60% to 95%, 65% to 90%, 70% to 85%, 75% to 80%, etc. As a result, when a gel polymer electrolyte obtained within the above blending ratio range is used in a battery, the capacity retention rate and rate performance of the battery can be improved.

[0058] In some embodiments of the present application, the gel polymer electrolyte includes a first crosslinker and a second crosslinker, and the decrosslinking temperature of the second crosslinker is 40°C or higher, such as 40°C to 120°C, 45°C to 120°C, 45°C to 110°C, 40°C to 100°C, 45°C to 90°C, 50°C to 80°C, 55°C to 75°C, or 60°C to 70°C.

[0059] Decrosslinking is the reverse reaction of crosslinking. Crosslinking refers to the reaction in which two or more molecules (generally linear molecules) are crosslinked to form a network structure (three-dimensional molecules), while decrosslinking refers to the reaction in which the network structure molecules are broken down into two or more molecules. For example, crosslinking is performed by the Diels-Alder reaction, and decrosslinking is performed by the reverse Diels-Alder reaction.

[0060] The temperature at which the polymer in the gel polymer electrolyte and the second crosslinker begin to decrosslink is the decrosslinking temperature, that is, the temperature at which the polymer in the gel polymer electrolyte and the second crosslinker begin to decrosslink from a crosslinked state.

[0061] In the examples of the present application, in the gel polymer electrolyte, the cross-linking and de-cross-linking of the polymer are reversible reactions, where at a first higher temperature, at least a portion of the second cross-linker undergoes a de-cross-linking reaction with the polymer host material, and at a second lower temperature, the second cross-linker undergoes a cross-linking reaction with the polymer host.

[0062] In the examples of the present application, the presence of the first crosslinker is intended to prevent the gel polymer electrolyte from being completely decrosslinked by the mobile phase at the first high temperature, so that when the decrosslinking temperature of the second crosslinker is reached, the first crosslinker remains in a crosslinked state, and at least a portion of the second crosslinker is decrosslinked with the polymer in the gel polymer electrolyte, ensuring that the gel polymer electrolyte can function and improving the capacity retention and rate performance of the battery at the first temperature.

[0063] In some embodiments of the present application, the first crosslinker may include at least one of an acrylate-based crosslinker and a conjugated diene, for example, the acrylate-based crosslinker includes at least one of ethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, trimethylolpropane ethoxylate triacrylate, trimethylolpropane propoxylate triacrylate, ditrimethylolpropane tetraacrylate, pentaerythritol tetraacrylate, pentaerythritol ethoxylate tetraacrylate, dipentaerythritol pentaacrylate, and dipentaerythritol hexaacrylate, and the conjugated diene includes at least one of divinylbenzene and 1,3-butadiene. As a result, by using the above-mentioned first crosslinking agent, all of the polymers and the second crosslinking agent in the gel polymer electrolyte are not uncrosslinked at the first temperature, ensuring that the gel polymer electrolyte can function, thereby improving the capacity retention rate and rate performance of the battery.

[0064] In some embodiments of the present application, the second cross-linker comprises at least one of maleimide and N-substituted derivatives of maleimide.

[0065] The N-substituted derivatives of maleimide refer to organic compounds in which the hydrogen atom in the imino group in maleimide is substituted with another group, such as N-phenylmaleimide (NPMI), N-butylmaleimide (BMI), etc. As long as they are N-substituted derivatives of maleimide, they fall within the scope of protection of the present application.

[0066] As a result, by using the above-mentioned second crosslinking agent, when the de-crosslinking temperature of the second crosslinking agent is reached, at least a portion of the second crosslinking agent and the polymer in the gel polymer electrolyte are de-crosslinked, thereby improving the capacity retention rate and rate performance of the battery at the first temperature.

[0067] It can be understood that the first and second crosslinkers mentioned above in this application can be purchased commercially or prepared by synthetic methods known in the art.

[0068] In some embodiments of the present application, the molar ratio of the first crosslinking agent to the second crosslinking agent is 0.5 to 5:1, and may be, for example, 0.7 to 5:1, 1 to 4.5:1, 1.5 to 4:1, 2 to 3.5:1, 2.5 to 2:1, etc. By setting the ratio of the first crosslinking agent to the second crosslinking agent within the above range, it is possible to suitably achieve partial de-crosslinking of the polymer in the gel polymer electrolyte at a higher first temperature and crosslinking at a lower second temperature, thereby improving the capacity retention rate and rate performance of the battery at the first temperature.

[0069] In some embodiments of the present application, the gel polymer electrolyte further comprises a host material, and the host material monomer comprises at least one of a vinyl group, an epoxy group, an allyl group, an acryloyl group, and a methacryloyl group. This allows the host material monomer to undergo crosslinking reactions with the first crosslinker and the second crosslinker, respectively, during the process of forming the host material by polymerization. This also allows the polymer in the gel polymer electrolyte to be partially uncrosslinked at a first higher temperature and crosslinked at a second lower temperature, thereby improving the capacity retention rate and rate performance of the battery.

[0070] In some embodiments of the present application, the host material monomer includes at least one of furfuryl methacrylate, ethylene glycol diglycidyl ether, 1,5-hexadiene diepoxide, glycerol propoxylate triglycidyl ether, vinylcyclohexene dioxide, 1,2,7,8-diepoxyoctane, 4-vinylcyclohexene dioxide, butyl glycidyl ether, 1,2-cyclohexanedicarboxylic acid diglycidyl ester, ethylene glycol diglycidyl ether, glycerol triglycidyl ether, and glycidyl methacrylate. This allows the host material monomer to crosslink with the first crosslinker and the second crosslinker, respectively, during polymerization to form the host material. This also allows the polymer in the gel polymer electrolyte to be partially uncrosslinked at a higher first temperature and crosslinked at a lower second temperature, thereby improving the capacity retention and rate performance of the battery at the first temperature.

[0071] It can be appreciated that the above host material monomers can be purchased commercially or prepared by synthetic methods known in the art.

[0072] In some embodiments of the present application, the gel polymer electrolyte may include a polymer matrix and an electrolyte solution, and the electrolyte solution may include an electrolyte salt and a solvent.

[0073] If the battery is a lithium-ion battery, by way of example, the electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium perchlorate (LiClO), lithium hexafluoroarsenate (LiAsF), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium bisoxalatoborate (LiBOB), lithium difluorophosphate (LiPOF), lithium difluorobisoxalatophosphate (LiDFOP), and lithium tetrafluorooxalatophosphate (LiTFOP).

[0074] When the battery is a sodium-ion battery, by way of example, the electrolyte sodium salt may include at least one of sodium hexafluorophosphate, sodium difluorooxalatoborate, sodium tetrafluoroborate, sodium bisoxalatoborate, sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethanesulfonate, and sodium bis(trifluoromethanesulfonyl)imide.

[0075] By way of example, the solvent may include one or more of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS), and diethyl sulfone (ESE).

[0076] In some embodiments, the electrolyte solution further includes an additive. For example, the additive may include a negative electrode film-forming additive, a positive electrode film-forming additive, or an additive that can improve some performance of the battery, such as an additive that can improve the overcharge performance of the battery, an additive that can improve the high-temperature performance of the battery, or an additive that can improve the low-temperature performance of the battery.

[0077] A second aspect of the present application is a method for producing a gel polymer electrolyte, comprising: a host material monomer, an initiator, a cross-linking agent, and an electrolyte solution are mixed and then polymerized to obtain a gel polymer electrolyte; The gel polymer electrolyte has a first state at a first temperature and a second state at a second temperature, the first state and the second state being mutually convertible, the first temperature being higher than the second temperature, and the degree of crosslinking of the gel polymer electrolyte in the second state being higher than the degree of crosslinking of the gel polymer electrolyte in the first state.

[0078] Therefore, when the gel polymer electrolyte produced in this application is used in a battery, gaps appear between the interface of the battery sheet and the gel polymer electrolyte after multiple cycles at the second temperature, resulting in continuous deterioration of the battery capacity. However, when the battery is heated to the first temperature, the gel polymer electrolyte undergoes a depolymerization reaction, increasing the mobile phase in the gel polymer electrolyte, thereby firmly bonding the battery sheet and the gel polymer electrolyte and restoring the battery capacity. Furthermore, the increase in the mobile phase in the gel polymer electrolyte improves the ionic conductivity of the gel polymer electrolyte, further improving the rate performance of the battery.

[0079] In some embodiments of the present application, the crosslinking agent includes a first crosslinking agent and a second crosslinking agent, and the decrosslinking temperature of the second crosslinking agent is 40°C or higher, and may be, for example, 40°C to 120°C, 45°C to 110°C, 40°C to 100°C, 45°C to 90°C, 50°C to 80°C, 55°C to 75°C, or 60°C to 70°C. As a result, when the battery is heated to a first temperature and the decrosslinking temperature of the second crosslinking agent is reached, at least a portion of the second crosslinking agent and the polymer in the gel polymer electrolyte are decrosslinked, the mobile phase in the gel polymer electrolyte increases, and the capacity retention and rate performance of the battery at the first temperature can be improved.

[0080] In some embodiments of the present application, the molar ratio of the monomer of the host material to the crosslinker is 1:2 to 10, and may be, for example, 1:3 to 10, 1:4 to 9, 1:5 to 8, or 1:6 to 7. As a result, when a gel polymer electrolyte obtained within the above blending ratio range is used in a battery, the gel polymer electrolyte and at least a portion of the second crosslinker are de-crosslinked at a higher first temperature and crosslinked at a lower second temperature, thereby further improving the capacity retention rate and rate performance of the battery at the first temperature.

[0081] It should be understood that when the crosslinker includes a first crosslinker and a second crosslinker, the molar ratio of the monomer to the crosslinker of the host material refers to the ratio of the molar amount of the monomer to the sum of the molar amounts of the first crosslinker and the second crosslinker. Furthermore, the temperature at which the monomer of the host material, the initiator, the crosslinker, and the electrolyte solution are polymerized after mixing is not limited in the present application. In some embodiments of the present application, the polymerization temperature is 60°C to 80°C, such as 65°C to 80°C, 65°C to 75°C, or 65°C to 70°C, so as to facilitate rapid reaction and minimize side reactions.

[0082] It should be noted that the features and advantages described above for the gel polymer electrolyte are also applicable to the method for producing the gel polymer electrolyte, and therefore will not be repeated here.

[0083] A third aspect of the present application provides a battery including the gel polymer electrolyte according to the first aspect of the present application or the gel polymer electrolyte produced by the method according to the second aspect, thereby providing the battery with good capacity retention and rate performance.

[0084] The term "battery" refers to a battery that can be used continuously after discharge by activating the active material through charging.

[0085] Alternatively, the positive electrode sheet, separator, and negative electrode sheet may be wound in this order and then enclosed in a case, after which an electrolyte solution containing a polymer monomer is injected into the case. The interior of the battery cell is impregnated with the electrolyte solution containing the polymer monomer, and external conditions such as heat treatment cause a curing reaction of the polymer monomer to form a polymer matrix, ensuring that the interior of the battery cell is filled with a gel polymer electrolyte consisting of the polymer matrix and the electrolyte solution. Alternatively, the separator may be omitted; i.e., the positive electrode sheet and negative electrode sheet may be wound and then enclosed in a case, after which the electrolyte solution containing the polymer monomer is injected into the case.

[0086] In some embodiments of the present application, the battery may be a lithium ion battery or a sodium ion battery.

[0087] [Positive electrode sheet] In a battery, the positive electrode sheet usually includes a positive electrode current collector and a positive electrode active material layer provided on the positive electrode current collector, and the positive electrode active material layer includes a positive electrode active material.

[0088] The positive electrode current collector may be a conventional metal foil or a composite current collector (a composite current collector may be formed by providing a metal material on a polymer substrate.) For example, an aluminum foil may be used as the positive electrode current collector.

[0089] The specific type of the positive electrode active material is not limited, and may be any active material known in the art that can be used for a positive electrode of a battery, and may be selected by a person skilled in the art according to actual needs.

[0090] For example, when the battery is a lithium-ion battery, the positive electrode active material may include, but is not limited to, one or more of lithium transition metal oxides, lithium-containing phosphates with an olivine structure, and modified compounds thereof. Examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and modified compounds thereof. Examples of lithium phosphates with an olivine structure may include, but are not limited to, one or more of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, lithium manganese iron phosphate and carbon composites, and modified compounds thereof. All of these materials are commercially available.

[0091] For example, if the battery is a sodium ion battery, the positive electrode active material may include, by way of example only, but not limited to, at least one of a layered transition metal oxide, a polyanionic compound, and a Prussian blue analog.

[0092] Examples of the layered transition metal oxides include the following: Na 1-x Cu h Fe k Mn l M 1 m O 2-y where M 1 is one or more of Li, Be, B, Mg, Al, K, Ca, Ti, Co, Ni, Zn, Ga, Sr, Y, Nb, Mo, In, Sn, and Ba; <x≦0.33、0<h≦0.24、0≦k≦0.32、0<l≦0.68、0≦m<0.1、h+k+l+m=1、0≦y<0.2である。 Na0.67 Mn 0.7 Ni z M 2 0.3-z O2, where M 2 is one or more of Li, Mg, Al, Ca, Ti, Fe, Cu, Zn, and Ba; <z≦0.1である。 Na a Li b Ni c Mn d Fe e O2, where 0.67 <a≦1、0<b<0.2、0<c<0.3、0.67<d+e<0.8、b+c+d+e=1である。

[0093] Examples of the polyanion compound include the following: A 1 f M 3 g (PO4) i O j X 1 3-j where A 1 is one or more of H, Li, Na, K, and NH4; M 3 is one or more of Ti, Cr, Mn, Fe, Co, Ni, V, Cu, and Zn; and X 1 is one or more of F, Cl, and Br, and 0 <f≦4、0<g≦2、1≦i≦3、0≦j≦2である。 Na n M 4 PO4X 2 where M 4 is one or more of Mn, Fe, Co, Ni, Cu, and Zn; and X 2 is one or more of F, Cl, and Br, and 0 <n≦2である。 Na p M 5 q (SO4)3, where M 5 is one or more of Mn, Fe, Co, Ni, Cu, and Zn, and 0 <p≦2、0<q≦2である。 Na s Mnt Fe 3-t (PO4)2(P2O7), where 0 < s ≤ 4, 0 ≤ t ≤ 3, for example, t is 0, 1, 1.5, 2, or 3.

[0094] Examples of the above Prussian blue analogs include, for example, the following. A u M 6 v [M 7 (CN)6] w ·xH2O, where A is H + , NH4 + , one or more of an alkali metal cation, and an alkaline earth metal cation, M 6 and M 7 are each independently one or more of transition metal cations, 0 < u ≤ 2, 0 < v ≤ 1, 0 < w ≤ 1, 0 < x < 6. For example, A is H + , Li + , Na + , K + , NH4 + , Rb + , Cs + , Fr + , Be 2+ , Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , and Ra 2+ , one or more of them, M 6 and M 7 are each independently cations of one or more transition metal elements of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sn, and W.

[0095] The modified compounds of the above materials may be those obtained by doping modification and / or surface coating modification of the materials.

[0096] The positive electrode active material layer usually further selectively contains a binder, a conductive agent, and other selective auxiliaries.

[0097] By way of example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, Super P (SP), graphene, and carbon nanofibers.

[0098] By way of example, the binder may include one or more of styrene butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB).

[0099] [Negative electrode sheet] In a battery, the negative electrode sheet usually includes a negative electrode current collector and a negative electrode active material layer provided on the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material.

[0100] The negative electrode current collector may be a conventional metal foil or a composite current collector (for example, a composite current collector may be formed by providing a metal material on a polymer substrate). For example, a copper foil may be used as the negative electrode current collector.

[0101] The specific type of the negative electrode active material is not limited, and any active material known in the art that can be used for a battery negative electrode can be used, and those skilled in the art can select one according to actual needs. For example, the negative electrode active material may include, but is not limited to, one or more of artificial graphite, natural graphite, hard carbon, soft carbon, silicon-based materials, and tin-based materials. The silicon-based material may include one or more of silicon elemental, silicon-oxygen compounds (e.g., silicon monoxide), silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may include one or more of tin elemental, tin-oxygen compounds, and tin alloys. All of these materials are commercially available.

[0102] In some embodiments, to further improve the energy density of the battery, the negative electrode active material may include a silicon-based material.

[0103] The negative electrode active material layer generally optionally further contains a binder, a conductive agent, and other optional auxiliary agents.

[0104] By way of example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0105] By way of example, the binder may include one or more of styrene butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB).

[0106] For example, other optional auxiliary agents may include thickening and dispersing agents (eg, sodium carboxymethyl cellulose CMC-Na) and PTC thermistor materials.

[0107] The separator is not particularly limited in this application, and any known porous structure separator having electrochemical stability and mechanical stability can be selected according to actual needs, and may include, for example, a single-layer or multi-layer film containing one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride.

[0108] In the embodiments of the present application, the shape of the battery is not particularly limited and may be cylindrical, rectangular, or any other shape. For example, Fig. 1 shows a battery 1 having a rectangular structure as an example.

[0109] In some embodiments, the battery may include an outer casing for enclosing the positive electrode sheet, the negative electrode sheet, and the electrolyte.

[0110] In some embodiments, the exterior body may include a case and a cover plate. Here, the case may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate surround the case to form a storage cavity. The case has an opening communicating with the storage cavity, and the cover plate can cover the opening to seal the storage cavity.

[0111] The positive electrode sheet, the negative electrode sheet, and the separator can be wound or stacked to form an electrode assembly. The electrode assembly is enclosed in the receiving cavity. The number of electrode assemblies included in the battery can be one or more, and can be adjusted as needed.

[0112] In some embodiments, the battery exterior may be a hard case, such as a hard plastic case, an aluminum case, or a steel case.

[0113] The exterior of the battery may be a soft pack such as a pouch-type soft pack, etc. The material of the soft pack may be plastic, and may include, for example, one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0114] In some embodiments, the batteries may be assembled into a battery module, and the number of batteries included in the battery module may be multiple, and the specific number can be adjusted depending on the application and capacity of the battery module.

[0115] FIG. 2 shows an example of a battery module 2. Referring to FIG. 2, in the battery module 2, the plurality of batteries 1 may be arranged in sequence along the longitudinal direction of the battery module 2. Of course, they may be arranged in any other manner. Furthermore, the plurality of batteries 1 may be fixed by fastening members.

[0116] The battery module 2 may further include a housing having an accommodation space, and the plurality of secondary batteries 1 are accommodated in the accommodation space. In some embodiments, the above battery modules may be assembled into a battery pack, and the number of battery modules included in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0117] 3 and 4 show an example of a battery pack 3. Referring to FIGS. 3 and 4, the battery pack 3 may include a battery box and a plurality of battery modules 2 provided in the battery box. The battery box includes an upper box 4 and a lower box 5, and the upper box 4 is covered by the lower box 5 to form a sealed space for accommodating the battery modules 2. The plurality of battery modules 2 may be arranged in the battery box in any manner.

[0118] A fourth aspect of the present application is a method for charging and discharging a battery, comprising: the battery includes a gel polymer electrolyte, the gel polymer electrolyte having a first state at a first temperature and a second state at a second temperature, the first state and the second state being mutually convertible, the first temperature being higher than the second temperature, and the degree of crosslinking of the gel polymer electrolyte in the second state being higher than the degree of crosslinking of the gel polymer electrolyte in the first state; If the battery satisfies a first preset condition, charging and discharging the battery at a first temperature; If the battery satisfies a second preset condition, the method charges and discharges the battery at a second temperature.

[0119] In some embodiments of the present application, the battery is normally operated in the second temperature range and charged and discharged at normal power, during which the electrolyte of the battery is in a gel state, and the battery has good safety. When the battery experiences capacity decay as it is cycled multiple times, the temperature is raised to the first temperature and the battery is charged and discharged. During this time, a portion of the gel polymer electrolyte dissociates, the mobile phase increases, and the gel polymer electrolyte has low internal resistance and high ionic conductivity, improving the capacity retention rate and rate performance of the battery.

[0120] In some embodiments of the present application, the first preset condition is a ratio of the current internal resistance of the battery to the initial internal resistance of the battery greater than 1.5. Specifically, when the ratio of the current internal resistance of the battery to the initial internal resistance of the battery is greater than 1.5, the internal resistance increases, resulting in increased polarization, which affects the rate performance of the battery and indicates a certain degree of capacity degradation. In this case, when the battery is charged and discharged at a first temperature, at least a portion of the second crosslinker in the gel polymer electrolyte is decrosslinked with the host material, increasing the fluidity of the gel polymer electrolyte, reducing the internal resistance of the battery and improving the rate performance of the battery. Furthermore, the battery sheet and the gel polymer electrolyte are in closer contact with each other, thereby improving the capacity retention rate of the battery.

[0121] The internal resistance of a battery refers to the resistance experienced by the current flowing inside the battery when the battery is in operation, and is composed of two parts: ohmic internal resistance and polarization internal resistance. The ohmic internal resistance is determined by factors such as the battery's material, structure, and contact resistance, while the polarization internal resistance is caused by electrochemical reactions and concentration differences, and is related to the battery's active materials and solid-state diffusion coefficient.

[0122] The initial internal resistance of a battery refers to the internal resistance of the battery at the time of completion of its manufacture.

[0123] In some embodiments of the present application, the second preset condition is that the ratio of the current internal resistance of the battery to the initial internal resistance of the battery is 1.5 or less.

[0124] In one embodiment of the present application, when the ratio of the current internal resistance of the battery to the initial internal resistance of the battery is 1.5 or less, the battery is not heated and is charged and discharged at a second temperature. When the ratio of the current internal resistance of the battery to the initial internal resistance of the battery is greater than 1.5, the battery is heated to a first temperature, which partially decrosslinks the gel polymer electrolyte, increases the mobile phase in the gel polymer electrolyte, repairs the interface problems between the sheet and the gel polymer electrolyte caused by the charge and discharge process, and reduces the internal resistance of the battery. When the ratio of the current internal resistance of the battery to the initial internal resistance of the battery is 1.5 or less, the battery is switched to a second temperature for charge and discharge.

[0125] In some embodiments of the present application, the first preset condition is that the discharge rate of the battery is greater than 2 C. That is, the battery needs to be charged and discharged at a high rate. In this case, by adjusting the battery to operate at a first temperature, at least a portion of the second crosslinker in the gel polymer electrolyte is uncrosslinked with the host material, increasing the fluidity of the gel polymer electrolyte and improving the rate performance of the battery.

[0126] In some embodiments of the present application, the second preset condition is that the discharge rate of the battery is 2 C or less. That is, the battery needs to be charged and discharged at a low rate. In this case, by adjusting the battery to operate at the second temperature, at least a portion of the second crosslinker in the polymer gel electrolyte crosslinks with the host material, reducing the fluidity of the gel polymer electrolyte and degrading the rate performance of the battery.

[0127] A fifth aspect of the present application provides an electric device including the battery according to the third aspect for supplying electric energy, thereby providing a long life for the electric device. Specifically, the battery may serve as a power source for the electric device or as an energy storage unit for the electric device. The electric device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks), trains, ships, satellites, and energy storage systems.

[0128] Figure 5 shows an example of an electric device, including a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.

[0129] As another example, the electrical device may include a mobile phone, a tablet computer, or a laptop computer, which are typically required to be lightweight and thin and may use a battery as a power source.

[0130] In order to clarify the technical problems, technical solutions, and beneficial effects of the embodiments of the present application, a more detailed description will be provided below with reference to the embodiments and drawings. Of course, the described embodiments are only a portion of the embodiments of the present application, and not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and does not constitute any limitation on the present application and its applications. Based on the embodiments in the present application, other embodiments that can be obtained by those skilled in the art without any creative work are all within the scope of protection of the present application.

[0131] Example 1 Fabrication of secondary batteries containing gel polymer electrolytes 1. Preparation of gel polymer electrolyte precursor solution A precursor solution was prepared by mixing a host monomer, an initiator (azobisisobutyronitrile), a first crosslinking agent, a second crosslinking agent, and an electrolyte solution. The method for preparing the electrolyte solution involves mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a mass ratio of 30:70 to obtain an organic solvent, dissolving thoroughly dried electrolyte salt LiPF6 in the mixed solvent to a concentration of 1.0 mol / L, and uniformly mixing the mixture to obtain the electrolyte solution.

[0132] 2. Secondary battery manufacturing Positive electrode sheet manufacturing LiNi, the positive electrode active material 0.8 Co 0.1 Mn 0.1O2 (NCM811), carbon black (Super P) as a conductive agent, and polyvinylidene fluoride (PVDF) as a binder were uniformly mixed in a mass ratio of 96.2:2.7:1.1 with an appropriate amount of N-methylpyrrolidone (NMP) as a solvent to obtain a positive electrode slurry. The positive electrode slurry was then applied to an aluminum foil positive electrode current collector, and a positive electrode sheet was obtained through oven drying, cold pressing, slitting, and cutting processes.

[0133] Manufacture of negative electrode sheets The negative electrode active material, artificial graphite, the conductive agent, carbon black (Super P), the binders, styrene butadiene rubber (SBR) and carboxymethyl cellulose sodium (CMC-Na), were uniformly mixed in a mass ratio of 96.4:0.7:1.8:1.1 with an appropriate amount of deionized water as a solvent to obtain a negative electrode slurry. The negative electrode slurry was then applied to copper foil as a negative electrode current collector, followed by oven drying, cold pressing, slitting, and cutting to obtain a negative electrode sheet.

[0134] A polyethylene film was used as the separator.

[0135] The positive electrode sheet, separator, and negative electrode sheet were stacked in this order and then wound to obtain an electrode assembly. The electrode assembly was placed in an outer casing, and the precursor liquid prepared above was poured into the dried secondary battery, heated to 60 to 80°C to crosslink and harden the first crosslinking agent, and then cooled to crosslink and harden the second crosslinking agent, thereby obtaining a secondary battery.

[0136] The secondary batteries containing the gel polymer electrolyte of Examples 2 to 20 and the Comparative Example were the same as Example 1 except for different parameters (see Table 1).

[0137] The compositions of the gel polymer electrolytes in the batteries of Examples 1 to 20 and Comparative Examples of the present application are as shown in Table 1.

[0138] [Table 1] TIFF2026501647000003.tif176168TIFF2026501647000004.tif204168TIFF2026501647000005.tif89168

[0139] Secondary battery performance testing 1.Capacity retention rate Using Example 1 as an example, at the second temperature, the secondary battery was charged at a constant current of 0.5 C until the charge cutoff voltage reached 4.2 V, then charged at a constant voltage of 0.05 C until the current reached 0.05 C, allowed to stand for 5 minutes, and then discharged at a constant current of 0.33 C until the discharge cutoff voltage reached 2.8 V. The battery was allowed to stand for 5 minutes, and the battery discharge capacity C0 was recorded. According to this method, the battery was charged and discharged 500 times, and the battery discharge capacity after 500 cycles was recorded as C1.

[0140] At the second temperature, the cycle capacity retention rate of the secondary battery was C1 / C0×100%.

[0141] The method for measuring the cycle capacity retention rate of the secondary battery at the first temperature was the same as the method for measuring the cycle capacity retention rate at the second temperature in terms of other conditions and steps, except that the temperature was adjusted to the first temperature.

[0142] The test process for the capacity retention rate of the secondary batteries of Examples 2 to 20 and Comparative Example was the same as above.

[0143] 2. Rate performance At the second temperature, the battery was discharged at 0.2C to 3.0V, allowed to stand for 5 minutes, charged at 0.5C to 4.4V, charged at a constant voltage of 0.05C, and then allowed to stand for 5 minutes. The discharge rate was then adjusted, and a discharge test was performed at 2C to obtain the discharge capacity. The ratio of the capacity obtained at 2C to the capacity obtained at 0.2C was the rate performance of the battery.

[0144] The method for measuring the rate performance of the secondary battery at the first temperature was the same as the method for measuring the rate performance at the second temperature in other conditions and steps, except that the temperature was adjusted to the first temperature.

[0145] The test process for the rate performance of the secondary batteries of Examples 2 to 20 and the comparative example was the same as above.

[0146] The results of the performance tests of the secondary batteries of the examples and comparative examples are shown in Table 2.

[0147] [Table 2]

[0148] As can be seen from Table 2, in Examples 1 to 20 of the present application, the capacity retention and rate performance of the secondary batteries decreased to a certain extent after 500 cycles at the second temperature. However, when the operating temperature of the secondary batteries was raised to the first temperature, the capacity retention and rate performance of the secondary batteries were restored. Therefore, when the temperature was raised to the first temperature, the gel polymer electrolyte depolymerized, i.e., the degree of crosslinking of the gel polymer electrolyte decreased. At this time, the mobile phase in the gel polymer electrolyte increased, firmly bonding the battery sheet and the gel polymer electrolyte, thereby restoring the battery's capacity. Furthermore, the increase in the mobile phase in the gel polymer electrolyte improved the ionic conductivity of the gel polymer electrolyte, further improving the rate performance of the battery.

[0149] Compared with Examples 1 to 20, the Comparative Example had a first state at the first temperature but did not have a second state at the second temperature, and the capacity retention and rate performance of the secondary battery at the corresponding first and second temperatures were both low, and the initial capacity retention and rate performance could not be restored at the first temperature. Therefore, it can be seen that by using the gel polymer electrolyte of the present application, the battery containing it still has high capacity retention and rate performance even after multiple cycles.

[0150] Finally, it should be noted that the above embodiments are used only to illustrate the technical solutions of the present application and are not intended to limit the same. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments may be modified or equivalently substituted for some or all of their technical features, and that such modifications or substitutions do not deviate from the essence of the corresponding technical solutions and the scope of the technical solutions of the embodiments of the present application, and are all within the scope of the claims and the description of the present application. In particular, as long as there is no structural contradiction, any technical features described in the embodiments may be arbitrarily combined. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions within the scope of the claims. [Explanation of symbols]

[0151] 1 Secondary battery 2 Battery Module 3 Battery pack 4 Upper Box 5 Lower Box

Claims

1. A gel polymer electrolyte having a first state at a first temperature and a second state at a second temperature, wherein the first state and the second state are mutually convertible, the first temperature being higher than the second temperature, and a degree of crosslinking of the gel polymer electrolyte in the second state being higher than a degree of crosslinking of the gel polymer electrolyte in the first state.

2. 2. The gel polymer electrolyte according to claim 1, wherein the ratio of the degree of crosslinking in the first state to the degree of crosslinking in the second state of the gel polymer electrolyte is 0.2 to 0.95:

1.

3. the first temperature is 40°C or higher, optionally between 40°C and 120°C; and / or 3. The gel polymer electrolyte according to claim 1, wherein the degree of cross-linking of the gel polymer electrolyte in the first state is 20% to 48.5%.

4. the second temperature is between −25° C. and 35° C.; and / or The degree of cross-linking of the gel polymer electrolyte in the second state is 50% to 99%; and / or The gel polymer electrolyte according to any one of claims 1 to 3, wherein the gel polymer electrolyte further contains an electrolytic solution, and the mass ratio of the electrolytic solution in the gel polymer electrolyte is 60% to 98%.

5. The gel polymer electrolyte according to any one of claims 1 to 4, wherein the gel polymer electrolyte comprises a first crosslinking agent and a second crosslinking agent, and the de-crosslinking temperature of the second crosslinking agent is 40°C or higher, and optionally 40°C to 120°C.

6. the first crosslinker comprises at least one of an acrylate crosslinker and a conjugated diene; and / or the acrylate crosslinker comprises at least one of ethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, trimethylolpropane ethoxylate triacrylate, trimethylolpropane propoxylate triacrylate, ditrimethylolpropane tetraacrylate, pentaerythritol tetraacrylate, pentaerythritol ethoxylate tetraacrylate, dipentaerythritol pentaacrylate, and dipentaerythritol hexaacrylate; and / or the conjugated diene comprises at least one of divinylbenzene and 1,3-butadiene; and / or The gel polymer electrolyte of claim 5 , wherein the second crosslinker comprises at least one of maleimide and an N-substituted derivative of maleimide.

7. 7. The gel polymer electrolyte according to claim 5, wherein the molar ratio of the first crosslinking agent to the second crosslinking agent is 0.5 to 5:

1.

8. 8. The gel polymer electrolyte according to claim 1, further comprising a host material, wherein a monomer of the host material comprises at least one of a vinyl group, an epoxy group, an allyl group, an acryloyl group, and a methacryloyl group.

9. 9. The gel polymer electrolyte of claim 8, wherein the monomer of the host material includes at least one of furfuryl methacrylate, vinylcyclohexene dioxide, 1,5-hexadiene diepoxide, glycerol propoxylate triglycidyl ether, vinylcyclohexene dioxide, 1,2,7,8-diepoxyoctane, 4-vinylcyclohexene dioxide, butyl glycidyl ether, 1,2-cyclohexanedicarboxylic acid diglycidyl ester, ethylene glycol diglycidyl ether, glycerol triglycidyl ether, and glycidyl methacrylate.

10. 1. A method for producing a gel polymer electrolyte, comprising: a host material monomer, an initiator, a cross-linking agent, and an electrolyte solution are mixed and then polymerized to obtain a gel polymer electrolyte; The method, wherein the gel polymer electrolyte has a first state at a first temperature and a second state at a second temperature, the first state and the second state being mutually convertible, the first temperature being higher than the second temperature, and the degree of crosslinking of the gel polymer electrolyte in the second state being higher than the degree of crosslinking of the gel polymer electrolyte in the first state.

11. 11. The method of claim 10, wherein the cross-linking agent comprises a first cross-linking agent and a second cross-linking agent, and the de-cross-linking temperature of the second cross-linking agent is 40°C or higher, optionally 40°C to 120°C.

12. The method according to claim 10 or 11, wherein the molar ratio of the monomer of the host material to the crosslinking agent is 1:2-10.

13. A battery comprising the gel polymer electrolyte according to any one of claims 1 to 9, or the gel polymer electrolyte produced by the method according to any one of claims 10 to 12.

14. A method for charging and discharging a battery, comprising: the battery includes a gel polymer electrolyte, the gel polymer electrolyte having a first state at a first temperature and a second state at a second temperature, the first state and the second state being mutually convertible, the first temperature being higher than the second temperature, and the degree of crosslinking of the gel polymer electrolyte in the second state being higher than the degree of crosslinking of the gel polymer electrolyte in the first state; If the battery satisfies a first preset condition, charging and discharging the battery at a first temperature; If the battery satisfies a second preset condition, the method charges and discharges the battery at a second temperature.

15. The first preset condition is that the ratio of the current internal resistance of the battery to the initial internal resistance of the battery is greater than 1.5; and / or The method of claim 14 , wherein the second preset condition is that the ratio of the current internal resistance of the battery to the initial internal resistance of the battery is less than or equal to 1.

5.

16. The first preset condition is that the discharge rate of the battery is greater than 2C; and / or 15. The method of claim 14, wherein the second preset condition is that the discharge rate of the battery is 2C or less.

17. An electrical device comprising the battery of claim 13.

Images