Secondary battery and method for manufacturing the same

Abstract

The application provides a secondary battery and a preparation method thereof. The secondary battery comprises a polymer electrolyte, a positive electrode, a negative electrode and a diaphragm, the diaphragm is located between the positive electrode and the negative electrode, and the two ends of the positive electrode, the negative electrode and the diaphragm in the secondary battery are respectively filled with the polymer electrolyte. The diaphragm is first soaked with a first electrolyte in the basic active unit, and the first electrolyte is closed by the polymer electrolyte on the end face of the basic active unit, so that the physical adhesion between the surfaces of the positive electrode, the negative electrode and the diaphragm constituting the basic active unit can be better controlled, the utilization rate of the first electrolyte can be effectively improved, and the secondary battery provided by the application has a longer service life under the premise of the same amount of electrolyte. Compared with a solid / semi-solid electrolyte battery, the main electrolyte in the basic active unit of the application is still in a liquid state, and has better kinetic characteristics, especially when working at room temperature and low temperature.

Description

Technical Field

[0001] This invention relates to the field of new energy battery technology, and in particular to a secondary battery and its preparation method. Background Technology

[0002] High safety and stability, high energy density, long lifespan, and low cost per unit energy conversion are the eternal pursuits of rechargeable batteries. Common techniques for improving energy density include increasing the size of individual cells and improving the efficiency of battery packs. However, under the premise of using the same electrochemical material system and power design principles, simply increasing the size and capacity of individual cells will inevitably increase the physical volume or planar area of ​​the electrodes. This makes the control of the physical adhesion of the basic active unit, consisting of the positive electrode, the electrolyte-containing separator, and the negative electrode, particularly important.

[0003] Taking a traditional stacked lithium iron phosphate-graphite lithium-ion battery cell as the positive and negative electrode active materials, respectively, as an example: the positive electrode area of ​​a 10Ah cell is typically no more than 0.3 square meters, while that of a 280Ah cell is typically no less than 5.6 square meters. Let T be the physical thickness of the basic active unit consisting of the positive electrode, the electrolyte-containing separator, and the negative electrode, and S be the positive electrode area. Then, T*S is the physical volume of the basic active unit, denoted as V. For every 1μm increase in T, the required free electrolyte for a 10Ah cell typically increases by 0.3 mL, while that for a 280Ah cell increases by 5.6 mL. Therefore, when two cells have different capacities, and the physical thickness of the basic active unit increases by the same 1μm, the larger the cell capacity, the greater the increase in the required free electrolyte volume. Thus, controlling the physical adhesion between the surfaces of the positive electrode, negative electrode, and separator constituting the basic active unit is crucial for the utilization rate of the electrolyte in particularly large-capacity battery cells. Summary of the Invention

[0004] This invention provides a secondary battery and its preparation method to solve the technical problem of poor control over the physical bonding of basic active units in the prior art.

[0005] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0006] In a first aspect, the present invention provides a secondary battery comprising a polymer electrolyte and a positive electrode, a negative electrode, and a separator impregnated with a first electrolyte, wherein the separator is located between the positive electrode and the negative electrode, and the polymer electrolyte is respectively filled in the gaps at both ends of the positive electrode, the negative electrode, and the separator within the secondary battery.

[0007] Furthermore, the polymer electrolyte is obtained from the second electrolyte through an in-situ polymerization reaction.

[0008] Further, the second electrolyte comprises the following components by weight percentage: 80% to 99.4% mother liquor, 0.5% to 15% monomer, and 0.01% to 5% initiator, wherein the mother liquor comprises one or both of cyclic carbonates and chain carbonates.

[0009] Furthermore, the mother liquor includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0010] Further, the monomer includes one or more of acrylamide, acrylamide homologues, acrylamide derivatives, acrylates, acrylate homologues, acrylate derivatives, intermediates formed by homopolymerization of acrylamide or acrylamide homologues or acrylamide derivatives, intermediates formed by copolymerization of acrylamide or acrylamide homologues or acrylamide derivatives, intermediates formed by homopolymerization of acrylates or acrylate homologues or acrylate derivatives, and intermediates formed by copolymerization of acrylates or acrylate homologues or acrylate derivatives.

[0011] Further, the monomers include acrylamide, methacrylamide, styrene, isooctyl acrylate, isooctyl methacrylate, dodecyl acrylate, dodecyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate, polyethylene glycol methacrylate, N-methacryloylmorpholine, N,N-dimethylacrylamide, methyl acrylate, ethyl acrylate, butyl acrylate, hexyl acrylate, cyclohexyl acrylate, N-acryloylmorpholine, polyethylene glycol acrylate, hexyl glycol diacrylate, ethylene glycol diacrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, tetraethylene glycol diacrylate, tripropylene glycol diacrylate, pentaerythritol tetraacrylate ethoxylate, pentaerythritol tetraacrylate propionate, bis-trihydroxypropane tetraacrylate, pentaerythritol triacrylate, trimethylolpropane triacrylate, and glycerol triacrylate propionate. Tris(2-hydroxyethyl) isocyanurate triacrylate, propoxylated trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, pentaerythritol tetraacrylate, ethylene glycol dimethacrylate, ethylene glycol dimethacrylate, neopentyl glycol dimethacrylate, 1,6-hexanediol dimethacrylate, tetraethylene glycol dimethacrylate, tripropylene glycol dimethacrylate, pentaerythritol tetramethacrylate ethoxylated, pentaerythritol tetramethacrylate propoxylated, bis- One or more of the following: trihydroxypropane tetramethacrylate, pentaerythritol trimethacrylate, trimethylolpropane trimethacrylate, bis-trihydroxypropane tetramethacrylate, pentaerythritol trimethacrylate, trimethylolpropane trimethacrylate, propoxylated glycerol trimethacrylate, tri(2-hydroxyethyl)isocyanurate trimethacrylate, propoxylated trimethylolpropane trimethacrylate, ethoxylated trimethylolpropane trimethacrylate, and pentaerythritol tetramethacrylate.

[0012] Furthermore, the initiator includes one or more of peroxide initiators, redox initiators, and azo initiators.

[0013] Further, the initiator includes cumene hydroperoxide, dicumene peroxide, di-tert-butyl peroxide, benzoyl peroxide, dodecyl peroxide, tert-butyl peroxide, tert-butyl pervalerate, diisopropyl peroxide, dicyclohexyl peroxide, benzoyl peroxide, lauroyl peroxide, cumene hydroperoxide, tert-butyl hydroperoxide, di-tert-butyl peroxide, methyl ethyl ketone peroxide, cyclohexanone peroxide, potassium persulfate, sodium persulfate, ammonium persulfate, benzoyl peroxide / sucrose, tert-butyl hydroperoxide / calcined mortar, tert-butyl hydroperoxide / sodium metabisulfite, and peroxide... Benzoyl / N,N-dimethylaniline, ammonium persulfate / sodium bisulfite, potassium persulfate / sodium bisulfite, hydrogen peroxide / tartaric acid, hydrogen peroxide / mortar, ammonium persulfate / ferrous sulfate, hydrogen peroxide / ferrous sulfate, benzoyl peroxide / N,N-diethylaniline, benzoyl peroxide / ferrous pyrophosphate, potassium persulfate / silver nitrate, persulfate / thiol, cumene hydrogen peroxide / ferrous chloride, potassium persulfate / ferrous chloride, hydrogen peroxide / ferrous chloride, cumene hydrogen peroxide / tetraethyleneimine, azobisisoheptanenitrile, azobisisobutyronitrile, and dimethyl azobisisobutyrate.

[0014] Furthermore, the in-situ polymerization reaction temperature of the second electrolyte is greater than or equal to 30°C.

[0015] A second aspect of the present invention provides a method for preparing a secondary battery, comprising the following steps:

[0016] S1. Assemble the bare battery cells and place them into the housing to form a battery cell;

[0017] S2. Inject the first electrolyte into the battery cell;

[0018] S3. Control the temperature at both ends of the battery cell to remain below the temperature at which the polymer electrolyte is formed or below the temperature at which the second electrolyte polymerizes. Apply the polymer electrolyte formation conditions or the polymerization conditions of the second electrolyte to the area on the battery cell that restricts the entry of the second electrolyte or at the boundary of the area. Then inject the second electrolyte into the battery cell. After 3-60 minutes, raise the temperature at both ends of the battery cell to allow the second electrolyte to undergo an in-situ polymerization reaction to obtain the polymer electrolyte. The polymer electrolyte fills the voids at both ends of the positive electrode, the negative electrode, and the separator; and / or,

[0019] An external force is applied to areas of the battery cell where the polymer electrolyte does not need to be filled or where the entry of the second electrolyte is restricted. The magnitude of the applied external force is in the range of 0.3 to 1.2 MPa. Then, the second electrolyte is injected into the battery cell. After 3 to 60 minutes, the temperature at both ends of the battery cell is raised to cause the second electrolyte to undergo an in-situ polymerization reaction to obtain the polymer electrolyte. The polymer electrolyte fills the gaps at both ends of the positive electrode, the negative electrode, and the separator.

[0020] S4. Perform the formation process to obtain the secondary battery.

[0021] Furthermore, the volume ratio of the second electrolyte injected in step S3 to the first electrolyte injected in step S2 is 1:10 to 100.

[0022] Furthermore, the secondary battery is a sodium-ion battery or a lithium-ion battery, and the first electrolyte comprises the following components by weight percentage: 5% to 29% conductive salt, 70% to 94% solvent, and 0.1% to 20% functional additives.

[0023] Furthermore, the secondary battery is a sodium-ion battery, and the conductive salt includes one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium difluorophosphate, sodium bis(oxalate)borate, sodium difluorooxalateborate, sodium difluorosulfonylimide, sodium bis(trifluoromethanesulfonyl)imide, sodium difluorodioxalate phosphate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium difluorophosphate, lithium bis(oxalate)borate, lithium difluorooxalateborate, lithium bis(trifluoromethanesulfonyl)imide, and lithium difluorodioxalate phosphate.

[0024] Furthermore, the secondary battery is a sodium-ion battery, and the solvent is water or a non-aqueous organic solvent, wherein the non-aqueous organic solvent includes one or both of cyclic carbonates and chain carbonates.

[0025] Furthermore, the non-aqueous organic solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate.

[0026] Furthermore, the secondary battery is a sodium-ion battery, and the functional additive comprises the following components in weight percentage: 0.1% to 99.7% fluoroethylene carbonate, 0.1% to 99.7% ethylene sulfate, and 0.1% to 99.7% 1-propylphosphonic anhydride.

[0027] The secondary battery provided by this invention first fully wets the separator with a first electrolyte within the basic active unit, and then seals the first electrolyte with a polymer electrolyte at the end face of the basic active unit. This allows for better control of the physical adhesion between the surfaces of the positive electrode, negative electrode, and separator constituting the basic active unit, effectively improving the utilization rate of the first electrolyte. As a result, the secondary battery provided by this invention has a longer lifespan compared to traditional liquid electrolyte batteries with the same amount of electrolyte. Compared to solid / quasi-solid electrolyte batteries, since the main electrolyte inside the basic active unit of this invention is still liquid, it obviously has better kinetic characteristics, especially when operating at room temperature and low temperature.

[0028] The method for preparing a secondary battery provided by this invention is based on the existing liquid battery preparation process. It does not require complex processes or harsh control conditions, is easy to operate, and is more economical and applicable. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the basic active unit structure of the secondary battery in an embodiment of the present invention;

[0031] Figure 2 This is a schematic diagram of the secondary battery structure in an embodiment of the present invention.

[0032] Figure label:

[0033] 1. Positive electrode; 2. Negative electrode; 3. Membrane; 4. Polymer electrolyte. Detailed Implementation

[0034] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0035] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly set on the other component; when a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to the other component.

[0036] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0037] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "a plurality of" or "several" means two or more, unless otherwise explicitly specified.

[0038] It should be noted that the structures, proportions, sizes, etc., shown in the accompanying drawings of this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the conditions under which this application can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size should still fall within the scope of the technical content disclosed in this application, provided that they do not affect the effects and purposes that this application can produce.

[0039] Reference Figure 2 In a first aspect of this application, a secondary battery is provided, including a polymer electrolyte 4 and a positive electrode 1, a negative electrode 2, and a separator 3 impregnated with a first electrolyte. The separator 3 is located between the positive electrode 1 and the negative electrode 2. The gaps at both ends of the positive electrode 1, the negative electrode 2, and the separator 3 in the secondary battery are respectively filled with polymer electrolyte 4.

[0040] To better control the physical adhesion between the surfaces of the positive electrode, negative electrode, and separator that constitute the basic active unit, an adhesive and / or ceramic layer is usually coated on the surfaces of the positive electrode, negative electrode, and separator, and physical adhesion between the surfaces is promoted by hot pressing. However, the thickness of the adhesive layer itself and the implementation of the subsequent hot pressing process can cause secondary non-uniformity in the physical thickness, pore gradient, separator permeability, stress and strain of the basic active unit in local areas of the base film. In particular, when the adhesive is coated on the separator, the uneven distribution of the adhesive on the separator surface has a significant adverse effect on the internal resistance, charge and discharge speed, and other performance characteristics of the individual cells, especially leading to poor consistency of characteristics of cells in the same batch.

[0041] The secondary battery provided in this application embodiment first fully wets the separator 3 with a first electrolyte in the basic active unit, and then seals the first electrolyte with a polymer electrolyte 4 on the end face of the basic active unit. This can better control the physical adhesion between the surfaces of the positive electrode 1, negative electrode 2, and separator 3 constituting the basic active unit, effectively improving the utilization rate of the first electrolyte. Compared with traditional liquid electrolyte batteries, the secondary battery provided by this invention has a longer lifespan with the same amount of electrolyte. Compared with solid / quasi-solid electrolyte batteries, since the main electrolyte inside the basic active unit of this invention is still liquid, it obviously has better kinetic characteristics, especially when working at room temperature and low temperature.

[0042] In this embodiment, the secondary battery includes, but is not limited to, lithium-ion batteries, sodium-ion batteries, potassium-ion batteries, magnesium-ion batteries, or aluminum-ion batteries. The formulation of the first electrolyte is determined according to the specific secondary battery.

[0043] In this embodiment, the polymer electrolyte 4 possesses gas molecule permeability and barrier properties against the first electrolyte. During the fabrication and use of the single-cell battery, when the active unit is bonded under vacuum or external force, it can prevent the free first electrolyte from overflowing to the outside of the basic active unit, ensuring that the inside of the basic active unit is in the desired "fluid-rich state" with the first electrolyte. Furthermore, it can filter trace or large amounts of gas generated during the fabrication process to the outside of the active unit through various pressure differences, thereby controlling the physical bonding between the physical surfaces within the active unit. In addition, the self-adhesive effect of the polymer electrolyte 4 at the filling location is clearly advantageous for controlling the physical bonding between the physical surfaces within the active unit, especially at the edges.

[0044] Understandably, there are various methods to achieve the sealing of the polymer electrolyte 4 against the first electrolyte. In some embodiments, the polymer electrolyte 4 is obtained from the second electrolyte through an in-situ polymerization reaction. That is, the second electrolyte can polymerize in-situ within the basic active unit, thus acting as a binder for the basic active unit. The second electrolyte is injected into the electrolytic cell in liquid form, and the electrolyte in its free state first and most easily reaches the end face of the basic active unit.

[0045] Reference Figure 1 This is a schematic diagram of the basic structural unit of the secondary battery in this application embodiment. To ensure that the polymer electrolyte 4 generated by the polymerization of the second electrolyte fills only at both ends of the basic active unit, the temperature at both ends of the single cell is kept below the temperature of the polymerization reaction of the second electrolyte before the second electrolyte is injected. The polymerization conditions of the second electrolyte are applied in areas of the single cell where the second electrolyte does not need to reach or at the boundaries of those areas. When the second electrolyte reaches the boundary of the aforementioned area in liquid form, it solidifies due to polymerization and cannot move further into the area. Then, the polymerization conditions of the second electrolyte are applied to both ends of the single cell, thereby triggering an in-situ polymerization reaction for all the second electrolytes. Alternatively, before the second electrolyte is injected, an external force can be applied to areas of the single cell where the polymer electrolyte does not need to be filled or to areas where the second electrolyte is restricted from entering, so that the surfaces of the active units corresponding to the aforementioned areas and their boundaries are tightly adhered, thus preventing or delaying the entry of the second electrolyte into those areas. The conditions for the in-situ polymerization reaction can be high temperature, high pressure, vibrational heat, or photocatalysis, etc. Under controlled physical conditions, the distance the second electrolyte enters the interior of the basic active unit can be controlled through capillary action.

[0046] Understandably, the boundary between the area where the second electrolyte needs to be restricted from entering and the end face area of ​​the basic active unit that needs to be wetted by the second electrolyte is allowed to have a transition zone, and furthermore, the area of ​​the transition zone is less than or equal to 10% of the area of ​​the electrode plane.

[0047] Furthermore, the second electrolyte comprises the following components by weight percentage: 80% to 99.4% mother liquor, 0.5% to 15% monomer, and 0.01% to 5% initiator. The mother liquor comprises one or both of cyclic carbonates and chain carbonates.

[0048] In this embodiment, the second electrolyte can exist in liquid form at room temperature for more than one hour without undergoing polymerization or gelation. However, as time progresses, polymerization begins. In some embodiments, the in-situ polymerization temperature of the second electrolyte is greater than or equal to 30°C.

[0049] Specifically, the mother liquor includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. The monomers include one or more of acrylamide, acrylamide homologues, acrylamide derivatives, acrylates, acrylate homologues, acrylate derivatives, intermediates formed by homopolymerization of acrylamide or its homologues or derivatives, intermediates formed by copolymerization of acrylamide or its homologues or derivatives, intermediates formed by homopolymerization of acrylates or its homologues or derivatives, and intermediates formed by copolymerization of acrylates or its homologues or derivatives. Monomers include acrylamide, methacrylamide, styrene, isooctyl acrylate, isooctyl methacrylate, dodecyl acrylate, dodecyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, hexyl methacrylate, cyclohexyl 2-methacrylate, polyethylene glycol methacrylate, N-methacryloylmorpholine, N,N-dimethylacrylamide, methyl acrylate, ethyl acrylate, butyl acrylate, hexyl acrylate, cyclohexyl acrylate, N-acryloylmorpholine, polyethylene glycol acrylate, hexyl glycol diacrylate, ethylene glycol diacrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, tetraethylene glycol diacrylate, tripropylene glycol diacrylate, pentaerythritol tetraacrylate ethoxylate, pentaerythritol tetraacrylate propionate, bis-trihydroxypropane tetraacrylate, pentaerythritol triacrylate, trimethylolpropane triacrylate, propionate glycerol triacrylate, tri(2) The following are some of the following: tri(2-hydroxyethyl) isocyanurate triacrylate, propoxylated trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, pentaerythritol tetraacrylate, ethylene glycol dimethacrylate, ethylene glycol dimethacrylate, neopentyl glycol dimethacrylate, 1,6-hexanediol dimethacrylate, tetraethylene glycol dimethacrylate, tripropylene glycol dimethacrylate, ethoxylated pentaerythritol tetramethacrylate, propoxylated pentaerythritol tetramethacrylate, bis-trihydroxypropane tetramethacrylate, pentaerythritol trimethacrylate, trimethylolpropane trimethacrylate, bis-trihydroxypropane tetramethacrylate, pentaerythritol trimethacrylate, trimethylolpropane trimethacrylate, propoxylated glycerol trimethacrylate, tri(2-hydroxyethyl) isocyanurate trimethacrylate, propoxylated trimethylolpropane trimethacrylate, ethoxylated trimethylolpropane trimethacrylate, and pentaerythritol tetramethacrylate.

[0050] In this application embodiment, the initiator includes one or more of peroxide initiators, redox initiators, and azo initiators. Specifically, the initiator includes cumene hydroperoxide, dicumene peroxide, di-tert-butyl peroxide, benzoyl peroxide, dodecyl peroxide, tert-butyl peroxide, tert-butyl pervalerate, diisopropyl peroxide, dicyclohexyl peroxide, benzoyl peroxide, lauroyl peroxide, cumene hydroperoxide, tert-butyl hydroperoxide, di-tert-butyl peroxide, methyl ethyl ketone peroxide, cyclohexanone peroxide, potassium persulfate, sodium persulfate, ammonium persulfate, benzoyl peroxide / sucrose, tert-butyl hydroperoxide / mortar, tert-butyl hydroperoxide / sodium metabisulfite, and benzoyl peroxide. Formicyl / N,N-dimethylaniline, ammonium persulfate / sodium bisulfite, potassium persulfate / sodium bisulfite, hydrogen peroxide / tartaric acid, hydrogen peroxide / mortar, ammonium persulfate / ferrous sulfate, hydrogen peroxide / ferrous sulfate, benzoyl peroxide / N,N-diethylaniline, benzoyl peroxide / ferrous pyrophosphate, potassium persulfate / silver nitrate, persulfate / thiol, cumene hydrogen peroxide / ferrous chloride, potassium persulfate / ferrous chloride, hydrogen peroxide / ferrous chloride, cumene hydrogen peroxide / tetraethyleneimine, azobisisoheptanenitrile, azobisisobutyronitrile, and dimethyl azobisisobutyrate.

[0051] In this embodiment, the mother liquor in the second electrolyte is an organic solvent (plasticizer). The monomer contains alkenyl unsaturated bonds. Under the action of an initiator (which can usually generate free radicals), the unsaturated bonds will open and undergo a polymerization reaction with the organic solvent to form copolymers and a small amount of homopolymers.

[0052] A second aspect of this application provides a method for preparing the aforementioned secondary battery, comprising the following steps: S1, assembling a bare battery cell and placing the bare battery cell into a casing to form a battery cell; S2, injecting a first electrolyte into the battery cell; S3, controlling the temperature at both ends of the battery cell to be maintained below the temperature at which the polymer electrolyte 4 is formed or below the temperature at which the second electrolyte polymerizes, implementing the formation conditions of the polymer electrolyte 4 or the polymerization conditions of the second electrolyte at the region or boundary of the region on the battery cell that restricts the entry of the second electrolyte, and then injecting the second electrolyte into the battery cell. After 3 to 60 minutes, the temperature at both ends of the battery cell is raised to allow the second electrolyte to polymerize. An in-situ polymerization reaction occurs to obtain a polymer electrolyte 4, which fills the gaps at both ends of the positive electrode 1, the negative electrode 2, and the separator 3; and / or, an external force is applied to areas of the cell where the polymer electrolyte 4 does not need to be filled or to areas that restrict the entry of the second electrolyte, with the applied external force ranging from 0.3 to 1.2 MPa. Then, the second electrolyte is injected into the cell. After 3 to 60 minutes, the temperature at both ends of the cell is raised to cause the second electrolyte to undergo an in-situ polymerization reaction to obtain the polymer electrolyte 4, which fills the gaps at both ends of the positive electrode 1, the negative electrode 2, and the separator 3; S4, a formation process is performed to obtain a secondary battery.

[0053] In this embodiment, by controlling the temperature at both ends of the battery cell and the temperature at the region or boundary of the region that restricts the entry of the second electrolyte, the second electrolyte can be smoothly filled at both ends of the battery cell. If the second electrolyte reaches the aforementioned region or boundary, a polymerization reaction will occur due to the increased temperature, thereby preventing or delaying the entry of the second electrolyte into the region. Furthermore, the same effect can be achieved by applying external force to areas of the battery cell where the polymer electrolyte 4 does not need to be filled, and the magnitude of the applied external force ranges from 0.3 to 1.2 MPa.

[0054] In this application embodiment, bare battery cells are assembled using selected electrochemical material systems and common assembly methods. The material systems include, but are not limited to, lithium-ion batteries, sodium-ion batteries, potassium-ion batteries, magnesium-ion batteries, or aluminum-ion batteries; as well as materials required for the preparation of anion batteries such as fluorine, chlorine, bromine, and iodine. Assembly methods include, but are not limited to, stacked, wound, and hybrid types. The casing includes, but is not limited to, flexible packaging bags, cylindrical casings, and square casings. Flexible packaging bags include, but are not limited to, aluminum-plastic film, steel-plastic film, organic polymer and / or inorganic composite film; cylindrical casings include, but are not limited to, the casings used in the following common commercial cylindrical battery models: 13430, 18650, 26650, 21700, 32650, 32700, and 4680; square casings include, but are not limited to, casings with at least one polygonal cross-sectional shape.

[0055] In this embodiment of the application, before step S2, the electrochemical material system for which the moisture content needs to be controlled to the target value is dehydrated. The dehydration methods include, but are not limited to, vacuum baking, freezing, infrared heating, high-speed centrifugation, desiccant adsorption, catalytic phase change, etc.

[0056] The secondary battery preparation method provided in this application is based on the existing liquid battery preparation process. It does not require complex processes and harsh control conditions, and is simple to operate and more economical.

[0057] In step S2, the injected first electrolyte fully wets the basic active units within the battery cell. Taking a sodium-ion battery material system as an example, the first electrolyte is preferably a low-viscosity electrolyte with low desolvation energy. After solvation, it has a small Stokes radius and high conductivity, enabling it to fully wet the electrodes and separator pores, thus forming a fully wetted positive electrode active material-electrolyte interface and a negative electrode active material-electrolyte interface. The wetting methods include, but are not limited to, vacuum breathing and settling, temperature and pressure controlled setting, mechanical vibration, ultrasonic amplification, and chromatography. In some embodiments, the secondary battery is a sodium-ion battery, and the first electrolyte comprises the following components by weight percentage: 5%–29% conductive salt, 70%–94% solvent, and 0.1%–20% functional additives.

[0058] Specifically, the secondary battery is a sodium-ion battery, and the conductive salt includes one or more of the following: sodium hexafluorophosphate, sodium tetrafluoroborate, sodium difluorophosphate, sodium bis(oxalato)borate, sodium difluorooxalatoborate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, sodium difluorodioxalatophosphate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium difluorophosphate, lithium bis(oxalato)borate, lithium difluorooxalatoborate, lithium bis(trifluoromethanesulfonyl)imide, and lithium difluorodioxalatophosphate. The solvent is water or a non-aqueous organic solvent, and the non-aqueous organic solvent includes one or two of cyclic carbonates and chain carbonates. Further, the non-aqueous organic solvent includes one or more of the following: ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate.

[0059] Specifically, the secondary battery is a sodium-ion battery, and the functional additives include the following components by weight percentage: 0.1% to 99.7% fluoroethylene carbonate, 0.1% to 99.7% ethylene sulfate, and 0.1% to 99.7% 1-propylphosphonic anhydride.

[0060] In this embodiment of the application, the volume ratio of the second electrolyte injected in step S3 to the first electrolyte injected in step S2 is 1:10 to 100.

[0061] In this embodiment, in step S3, the two ends of the battery cell are cooled to below 30°C, while in-situ polymerization of the second electrolyte is carried out in other areas of the battery cell, for example, the temperature is set at 45°C. Then, the second electrolyte is injected into the battery cell. After 30 minutes, when the second electrolyte reaches the boundary of the aforementioned area in liquid form, it solidifies due to polymerization and cannot move further into the aforementioned area. Finally, the temperature at both ends of the battery cell is raised to allow the second electrolyte to undergo an in-situ polymerization reaction to obtain a polymer electrolyte 4, which fills the gaps at both ends of the positive electrode 1, negative electrode 2, and separator 3.

[0062] All reagents used in the following examples are commercially available.

[0063] Example 1

[0064] A sodium-ion battery includes a polymer electrolyte and a positive electrode, a negative electrode, and a separator impregnated with a first electrolyte. The separator is located between the positive electrode and the negative electrode. The gaps at both ends of the positive electrode, the negative electrode, and the separator are respectively filled with polymer electrolyte.

[0065] The first electrolyte comprises the following components by weight percentage: 13% sodium hexafluorophosphate; a mixed organic solvent composed of propylene carbonate (PC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC) in a mass fraction ratio of 3:2:5, with the mixed organic solvent comprising 83.5% by weight in the first electrolyte; and 3.5% functional additives, wherein the functional additives comprise the following components by weight percentage: 2% fluoroethylene carbonate, 1% ethylene sulfate, and 0.5% 1-propylphosphonic anhydride.

[0066] The polymer electrolyte is obtained from the second electrolyte via an in-situ polymerization reaction. The second electrolyte comprises the following components by weight percentage: a mother liquor containing a mixed plasticizer, wherein propylene carbonate (PC) and ethylene carbonate (EC) are mixed uniformly in a weight ratio of 7:3, and the mixed plasticizer accounts for 95% by weight in the second electrolyte; a monomer mixture of acrylamide, dodecyl acrylate, ethyl methacrylate, and pentaerythritol triacrylate in a mass fraction of 25:5:10:60, and this monomer mixture accounts for 4.85% by weight in the second electrolyte; and an initiator containing 0.15% by weight of benzoyl peroxide. The in-situ polymerization reaction temperature of the second electrolyte is 30°C.

[0067] The above-mentioned method for preparing sodium-ion batteries includes the following steps:

[0068] 1. Assemble the bare battery cells using a stacked assembly method; then place the bare battery cells into the housing to form the battery cells. The housing is a square housing.

[0069] 2. Inject the first electrolyte into the battery cell to fully wet the basic active units in the battery cell.

[0070] 3. Cool the temperature of both ends of the battery cell to below 30°C, and keep the temperature of the area on the battery cell that restricts the entry of the second electrolyte at 30°C. Then inject the second electrolyte into the battery cell. The volume ratio of the second electrolyte to the first electrolyte is 1:10. After 60 minutes, raise the temperature of both ends of the battery cell to 30°C to allow the second electrolyte to undergo an in-situ polymerization reaction to obtain a polymer electrolyte. The polymer electrolyte fills the gaps at both ends of the positive electrode, negative electrode, and separator.

[0071] 4. Perform the formation process, and simultaneously or after the formation process, perform vacuum degassing and sealing operations, record the total amount of the first electrolyte and the second electrolyte inside the casing, and finally obtain the sodium-ion battery described above.

[0072] The sodium-ion battery obtained in Example 1 was subjected to a room-temperature cycle test. The specific method for the cycle life test was as follows: under an environment of 25℃±3℃, it was charged at a constant current of 0.3C to 4.0V, then switched to a constant voltage of 4.0V until the current decreased to 0.05C to complete the charging; under the same environment, it was left to stand for 30 minutes, then switched to discharge mode, with the following discharge parameters set: discharged at a constant current of 1C to 1.5V cutoff; left to stand for 30 minutes, then continued charging and cycling. 500 cycles were monitored, and the volume change, charge / discharge capacity, charge / discharge energy during the cycle process were recorded. The volume expansion rate, charge / discharge coulombic efficiency, energy efficiency, average charging voltage, and average discharging voltage were calculated.

[0073] Example 2

[0074] A sodium-ion battery includes a polymer electrolyte and a positive electrode, a negative electrode, and a separator impregnated with a first electrolyte. The separator is located between the positive electrode and the negative electrode. The gaps at both ends of the positive electrode, the negative electrode, and the separator are respectively filled with polymer electrolyte.

[0075] The first electrolyte comprises the following components by weight percentage: 13% sodium hexafluorophosphate; a mixed organic solvent composed of propylene carbonate (PC), ethylene carbonate (EC), and diethyl carbonate (DEC) in a mass fraction ratio of 7:1:2, with the mixed organic solvent comprising 83.5% by weight in the first electrolyte; and 3.5% functional additives, wherein the functional additives comprise the following components by weight percentage: 2% fluoroethylene carbonate, 1% ethylene sulfate, and 0.5% 1-propylphosphonic anhydride.

[0076] The polymer electrolyte is obtained from the second electrolyte via in-situ polymerization. The second electrolyte comprises the following components by weight percentage: a mother liquor containing a mixed plasticizer, wherein propylene carbonate (PC) and ethylene carbonate (EC) are mixed uniformly in a mass ratio of 9:1, and the mixed plasticizer accounts for 95% by weight in the second electrolyte; a monomer is a mixture of acrylamide, ethyl methacrylate, and pentaerythritol triacrylate in a mass ratio of 25:15:70, and this monomer mixture accounts for 4.85% by weight in the second electrolyte; and an initiator is benzoyl peroxide, accounting for 0.15% by weight. The in-situ polymerization reaction temperature of the second electrolyte is 45°C.

[0077] The above-mentioned method for preparing sodium-ion batteries includes the following steps:

[0078] 1. Assemble the bare battery cells using a stacked assembly method; then place the bare battery cells into the housing to form the battery cells. The housing is a square housing.

[0079] 2. Inject the first electrolyte into the battery cell to fully wet the basic active units in the battery cell.

[0080] 3. Cool the temperature of both ends of the battery cell to below 45°C, and keep the temperature of the area on the battery cell that restricts the entry of the second electrolyte at 45°C. Then inject the second electrolyte into the battery cell. The volume ratio of the second electrolyte to the first electrolyte is 1:10. After 30 minutes, raise the temperature of both ends of the battery cell to 45°C to allow the second electrolyte to undergo an in-situ polymerization reaction to obtain a polymer electrolyte. The polymer electrolyte fills the gaps at both ends of the positive electrode, negative electrode, and separator.

[0081] 4. Perform the formation process, and simultaneously or after the formation process, perform vacuum degassing and sealing operations, record the total amount of the first electrolyte and the second electrolyte inside the casing, and finally obtain the sodium-ion battery described above.

[0082] The sodium-ion battery obtained above was subjected to a room temperature cycle test, the same as in Example 1.

[0083] Example 3

[0084] A sodium-ion battery includes a polymer electrolyte and a positive electrode, a negative electrode, and a separator impregnated with a first electrolyte. The separator is located between the positive electrode and the negative electrode. The gaps at both ends of the positive electrode, the negative electrode, and the separator are respectively filled with polymer electrolyte.

[0085] The first electrolyte comprises the following components by weight percentage: 13% sodium hexafluorophosphate; a mixed organic solvent composed of propylene carbonate (PC), ethylene carbonate (EC), and diethyl carbonate (DEC) in a mass fraction ratio of 7:1:2, with the mixed organic solvent comprising 83.5% by weight in the first electrolyte; and 3.5% functional additives, which comprise the following components by weight percentage: 2% fluoroethylene carbonate, 1% ethylene sulfate, and 0.5% 1-propylphosphonic anhydride.

[0086] The polymer electrolyte is obtained from the second electrolyte via an in-situ polymerization reaction. The second electrolyte comprises the following components by weight percentage: a mother liquor containing a mixed plasticizer, wherein propylene carbonate (PC) and ethylene carbonate (EC) are mixed uniformly in a mass ratio of 9:1, and the mixed plasticizer accounts for 95% by weight in the second electrolyte; a monomer is a mixture of acrylamide, ethyl methacrylate, and pentaerythritol triacrylate in a mass ratio of 25:15:70, and this monomer mixture accounts for 4.85% by weight in the second electrolyte; and an initiator is benzoyl peroxide, accounting for 0.15% by weight. The in-situ polymerization reaction temperature of the second electrolyte is 60°C.

[0087] The above-mentioned method for preparing sodium-ion batteries includes the following steps:

[0088] 1. Assemble the bare battery cells using a stacked assembly method; then place the bare battery cells into the housing to form the battery cells. The housing is a square housing.

[0089] 2. Inject the first electrolyte into the battery cell to fully wet the basic active units in the battery cell.

[0090] 3. Cool the temperature of both ends of the battery cell to below 60°C. Apply an external force of 0.3 MPa to the areas of the battery cell that do not need to be filled with polymer electrolyte or the areas that restrict the entry of the second electrolyte. Then inject the second electrolyte into the battery cell. The volume ratio of the second electrolyte to the first electrolyte is 1:10. After 15 minutes, raise the temperature of both ends of the battery cell to 60°C to allow the second electrolyte to undergo an in-situ polymerization reaction to obtain a polymer electrolyte. The polymer electrolyte fills the gaps at both ends of the positive electrode, negative electrode, and separator.

[0091] 4. Perform the formation process, and simultaneously or after the formation process, perform vacuum degassing and sealing operations, record the total amount of the first electrolyte and the second electrolyte inside the casing, and finally obtain the sodium-ion battery described above.

[0092] The sodium-ion battery obtained above was subjected to a room temperature cycle test, the same as in Example 1.

[0093] Example 4

[0094] A lithium-ion battery includes a polymer electrolyte and a positive electrode, a negative electrode, and a separator impregnated with a first electrolyte. The separator is located between the positive electrode and the negative electrode. The gaps at both ends of the positive electrode, the negative electrode, and the separator are respectively filled with polymer electrolyte.

[0095] The first electrolyte comprises the following components by weight percentage: 15% lithium hexafluorophosphate; a solvent being a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) in a mass percentage ratio of 3:7, wherein the mixed solvent comprises 82% by weight in the first electrolyte; and 2% functional additives, wherein the functional additives comprise the following components by weight percentage: 1% fluoroethylene carbonate, 1% ethylene sulfate, and 1% vinylene carbonate.

[0096] The polymer electrolyte is obtained from the second electrolyte via an in-situ polymerization reaction. The second electrolyte comprises the following components by weight percentage: a mother liquor consisting of a mixed plasticizer, wherein propylene carbonate (PC), ethylene carbonate (EC), and ethyl methyl carbonate (EMC) are mixed uniformly in a mass ratio of 7:2:1, and the mixed plasticizer accounts for 96% by weight in the second electrolyte; a monomer consisting of acrylamide, methyl methacrylate, and ethylene glycol diacrylate in a mass ratio of 25:25:50, and this monomer mixture accounts for 3.8% by weight in the second electrolyte; and an initiator consisting of benzoyl peroxide, accounting for 0.2% by weight. The in-situ polymerization reaction temperature of the second electrolyte is 85°C.

[0097] The above-mentioned method for preparing lithium-ion batteries includes the following steps:

[0098] 1. Assemble the bare battery cells using a stacked assembly method; then place the bare battery cells into the housing to form the battery cells. The housing is a square housing.

[0099] 2. Inject the first electrolyte into the battery cell to fully wet the basic active units in the battery cell.

[0100] 3. Cool the temperature of both ends of the battery cell to below 85°C. Apply an external force of 1.2 MPa to the areas of the battery cell that do not need to be filled with polymer electrolyte or the areas that restrict the entry of the second electrolyte. Then inject the second electrolyte into the battery cell. The volume ratio of the second electrolyte to the first electrolyte is 1:10. After 5 minutes, raise the temperature of both ends of the battery cell to 85°C to allow the second electrolyte to undergo an in-situ polymerization reaction to obtain a polymer electrolyte. The polymer electrolyte fills the gaps at both ends of the positive electrode, negative electrode, and separator.

[0101] 4. Perform the formation process, and simultaneously or after the formation process, perform vacuum degassing and sealing operations, record the total amount of the first electrolyte and the second electrolyte inside the casing, and finally obtain the above-mentioned lithium-ion battery.

[0102] The lithium-ion battery obtained in Example 4 was subjected to a room temperature cycle test. The specific method for the cycle life test was as follows: under an environment of 25℃±3℃, it was charged at a constant current of 0.3C to 3.7V, then switched to a constant voltage of 3.7V until the current decreased to 0.05C to complete the charging; under the same environment, it was left to stand for 30 minutes, then switched to discharge mode, with the following discharge parameters set: discharged at a constant current of 1C to 2.5V cutoff; left to stand for 30 minutes, then continued charging and cycling. 1000 cycles were monitored, and the volume change, charge / discharge capacity, and charge / discharge energy were recorded during the cycle process. The volume expansion rate, charge / discharge coulombic efficiency, energy efficiency, average charging voltage, and average discharging voltage were calculated.

[0103] Example 5

[0104] A lithium-ion battery includes a polymer electrolyte and a positive electrode, a negative electrode, and a separator impregnated with a first electrolyte. The separator is located between the positive electrode and the negative electrode. The gaps at both ends of the positive electrode, the negative electrode, and the separator are respectively filled with polymer electrolyte.

[0105] The first electrolyte comprises the following components by weight percentage: 15% lithium hexafluorophosphate; a mixed solvent of ethylene carbonate (EMC) and diethyl carbonate (DEC) in a weight ratio of 4:6, wherein the mixed solvent comprises 82% by weight in the first electrolyte; and 3% functional additives, wherein the functional additives comprise the following components by weight percentage: 0.6% ethylene sulfate (DTD) and 2.4% vinylene carbonate (VC).

[0106] The polymer electrolyte is obtained from the second electrolyte via in-situ polymerization. The second electrolyte comprises the following components by weight percentage: a mother liquor containing a mixed plasticizer, wherein propylene carbonate (PC) and ethylene carbonate (EC) are mixed uniformly in a mass ratio of 7:3, and the mixed plasticizer accounts for 96.9% by weight in the second electrolyte; a monomer mixture of acrylamide, methyl methacrylate, and pentaerythritol triacrylate in a mass ratio of 25:20:55, and this monomer mixture accounts for 3.0% by weight in the second electrolyte; and an initiator containing benzoyl peroxide at a weight percentage of 0.1%. The in-situ polymerization reaction temperature of the second electrolyte is 30°C.

[0107] The above-mentioned method for preparing lithium-ion batteries includes the following steps:

[0108] 1. Assemble the bare battery cells using a stacked assembly method; then place the bare battery cells into the housing to form the battery cells. The housing is a square housing.

[0109] 2. Inject the first electrolyte into the battery cell to fully wet the basic active units in the battery cell.

[0110] 3. Cool the temperature of both ends of the battery cell to below 30°C, and keep the temperature of the area on the battery cell that restricts the entry of the second electrolyte at 30°C. Then inject the second electrolyte into the battery cell. The volume ratio of the second electrolyte to the first electrolyte is 1:10. After 30 minutes, raise the temperature of both ends of the battery cell to 45°C to allow the second electrolyte to undergo an in-situ polymerization reaction to obtain a polymer electrolyte. The polymer electrolyte fills the gaps at both ends of the positive electrode, negative electrode, and separator.

[0111] 4. Perform the formation process, and simultaneously or after the formation process, perform vacuum degassing and sealing operations, record the total amount of the first electrolyte and the second electrolyte inside the casing, and finally obtain the above-mentioned lithium-ion battery.

[0112] The lithium-ion batteries obtained above were subjected to room temperature cycling tests, as in Example 4.

[0113] Comparative Example 1

[0114] The process involves preparing the battery using traditional sodium-ion battery manufacturing methods, including the following steps:

[0115] 1) Use the same positive electrode, diaphragm, and negative electrode as in Example 1, as well as the same assembly method and housing as in steps 1 and 2 of Example 1;

[0116] 2) The first electrolyte is injected into the battery cell. The amount of the first electrolyte injected is the sum of the first electrolyte injection amount and the second electrolyte injection amount in steps 2 & 3 of the preparation method in Example 1, and the basic active units in the battery cell are fully wetted.

[0117] 3) Perform the formation process, and simultaneously or after formation, perform vacuum degassing and sealing to obtain the sodium-ion battery of Comparative Example 1. During the vacuum degassing and sealing process, record the amount of the first electrolyte retained inside the casing.

[0118] Comparative Example 1 and Example 1 underwent the same room temperature cycling test, and the comparison results are shown in Table 1:

[0119] Table 1 Comparison of Cyclic Test Results between Comparative Example 1 and Example 1

[0120]

[0121]

[0122] The results show that, under comparable conditions, although the amount of first electrolyte and total electrolyte in Example 1 is less than that in Comparative Example 1, Example 1 still has higher cycle capacity and energy retention, better kinetic performance, and smaller volume expansion rate before and after cycling. It also has higher charge and discharge energy efficiency after 500 cycles, which indicates that the physical surfaces inside the basic active cell of the single battery in this example are better bonded and the utilization rate of the first electrolyte is higher.

[0123] Comparative Example 2

[0124] The process involves preparing the battery using traditional sodium-ion battery manufacturing methods, including the following steps:

[0125] 1) Use the same positive electrode, diaphragm, and negative electrode as in Example 2, and the same assembly method and housing as in steps 1 and 2 of Example 2;

[0126] 2) The first electrolyte is injected into the battery cell. The amount of the first electrolyte injected is the sum of the first electrolyte injection amount and the second electrolyte injection amount in steps 2 & 3 of the preparation method in Example 2, and the basic active units in the battery cell are fully wetted.

[0127] 3) Perform the formation process, and simultaneously or after formation, perform vacuum degassing and sealing to obtain the sodium-ion battery of Comparative Example 2. During the vacuum degassing and sealing process, record the mass of the first electrolyte retained inside the casing.

[0128] Comparative Example 2 and Example 2 underwent the same room temperature cycling test, and the comparison results are shown in Table 2:

[0129] Table 2 Comparison of Cyclic Test Results between Comparative Example 2 and Example 2

[0130]

[0131]

[0132] The results show that, under comparable conditions, Example 2 has a higher cycle capacity and energy retention rate, better kinetic performance, and a smaller volume expansion rate before and after cycling, compared to Comparative Example 2, with the same first electrolyte content and total electrolyte content as Comparative Example 2. After 500 cycles, it has a higher charge and discharge energy efficiency, which indicates that the physical surfaces inside the basic active cell of the single battery of the present invention are better bonded and the first electrolyte utilization rate is higher.

[0133] Comparative Example 3

[0134] The process involves preparing the battery using traditional sodium-ion battery manufacturing methods, including the following steps:

[0135] 1) Use the same positive electrode, diaphragm, and negative electrode as in Example 3, and the same assembly method and housing as in steps 1 and 2 of Example 3;

[0136] 2) The first electrolyte is injected into the battery cell. The amount of the first electrolyte injected is the sum of the amount of the first electrolyte injected and the amount of the second electrolyte injected in steps 2 & 3 of the preparation method in Example 3, and the basic active units in the battery cell are fully wetted.

[0137] 3) Perform the formation process, and simultaneously or after formation, perform vacuum degassing and sealing to obtain Comparative Example 3 sodium-ion batteries. During the vacuum degassing and sealing processes, record the amount of the first electrolyte retained inside the casing.

[0138] Comparative Example 3 and Example 3 underwent the same room temperature cycling test, and the comparison results are shown in Table 3:

[0139] Table 3 Comparison of Cyclic Test Results between Comparative Example 3 and Example 3

[0140]

[0141] The results show that, under comparable conditions, even though the amount of the first electrolyte and the total amount of electrolyte in Example 3 are about 10% less than those in Comparative Example 3, the cycle capacity and energy retention of the sodium-ion battery in Example 3 are still comparable to those in Example 3, with better kinetic performance, smaller volume expansion before and after cycling, and higher charge and discharge energy efficiency after cycling. This indicates that the physical surfaces inside the basic active cell of the single cell of the present invention are better bonded, and the utilization rate of the first electrolyte is higher.

[0142] Comparative Example 4

[0143] The process involves preparing the battery using traditional lithium-ion battery manufacturing methods, including the following steps:

[0144] 1) Use the same positive electrode, diaphragm, and negative electrode as in Example 4, and the same assembly method and housing as in steps 1 and 2 of Example 4;

[0145] 2) The first electrolyte is injected into the battery cell. The amount of the first electrolyte injected is the sum of the first electrolyte injection amount and the second electrolyte injection amount in steps 2 & 3 of the preparation method in Example 4, and the basic active units in the battery cell are fully wetted.

[0146] 3) Perform formation operations, and simultaneously or after formation, perform vacuum degassing and sealing operations to obtain the lithium-ion battery of Comparative Example 4. During vacuum degassing and sealing operations, record the amount of the first electrolyte retained inside the casing.

[0147] Comparative Example 4 and Example 4 underwent the same room temperature cycling test, and the comparison results are shown in Table 4:

[0148] Table 4 Comparison of Cyclic Test Results between Comparative Example 4 and Example 4

[0149]

[0150] The results show that, under comparable conditions, the lithium-ion battery of Example 4, with a first electrolyte content and a total electrolyte content that are about 10% less than that of Comparative Example 4, still has a better cycle life and a smaller volume expansion rate than Comparative Example 4. This indicates that the physical surfaces of the basic active cells in the single-cell battery of the present invention are better bonded and the utilization rate of the first electrolyte is higher.

[0151] Comparative Example 5

[0152] The process involves preparing the battery using traditional lithium-ion battery manufacturing methods, including the following steps:

[0153] 1) Use the same positive electrode, diaphragm, and negative electrode as in Example 5, and the same assembly method and housing as in steps 1 and 2 of Example 5;

[0154] 2) The first electrolyte is injected into the battery cell. The amount of the first electrolyte injected is the sum of the first electrolyte injection amount and the second electrolyte injection amount in steps 2 & 3 of the preparation method in Example 5, and the basic active units in the battery cell are fully wetted.

[0155] 3) Perform the formation process, and simultaneously or after formation, perform vacuum degassing and sealing to obtain the lithium-ion battery of Comparative Example 5. During the vacuum degassing and sealing process, record the amount of the first electrolyte retained inside the casing.

[0156] Comparative Example 5 and Example 5 underwent the same room temperature cycling test, and the comparison results are shown in Table 5:

[0157] Table 5 Comparison of Cyclic Test Results between Comparative Example 5 and Example 5

[0158]

[0159] The results show that, under comparable conditions, the first electrolyte content and total electrolyte content of Example 5 are comparable to those of Comparative Example 5. The lithium-ion battery of Example 5 has higher cycle capacity and energy retention, lower volume expansion rate, and higher energy efficiency after 1000 cycles. This indicates that the physical surfaces inside the basic active unit of the single cell of the present invention are better bonded, and the utilization rate of the first electrolyte is higher.

[0160] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A secondary battery, characterized in that: The secondary battery includes a polymer electrolyte and a positive electrode, a negative electrode, and a separator impregnated with a first electrolyte. The separator is located between the positive electrode and the negative electrode. The gaps at both ends of the positive electrode, the negative electrode, and the separator are respectively filled with the polymer electrolyte. The polymer electrolyte is obtained from a second electrolyte through an in-situ polymerization reaction. The secondary battery includes a casing and bare cells, and the preparation of the secondary battery includes the following steps: S1. Assemble the bare battery cells and place them into the housing to form a battery cell; S2. Inject the first electrolyte into the battery cell; S3. Fill the gaps at both ends with polymer electrolyte. The filling process is as follows: control the temperature at both ends of the battery cell to be below the temperature at which the polymer electrolyte is formed or below the temperature at which the second electrolyte polymerizes. Implement the formation conditions of the polymer electrolyte or the polymerization conditions of the second electrolyte in the area of ​​the battery cell that restricts the entry of the second electrolyte or at the boundary of the area. Then inject the second electrolyte into the battery cell. After 3 to 60 minutes, raise the temperature at both ends of the battery cell to cause the second electrolyte to undergo an in-situ polymerization reaction to obtain the polymer electrolyte. The polymer electrolyte fills the gaps at both ends of the positive electrode, the negative electrode, and the separator. And / or, apply an external force to the area of ​​the battery cell that does not need to be filled with the polymer electrolyte or the area that restricts the entry of the second electrolyte. The magnitude of the applied external force is in the range of 0.3 to 1.2 MPa. Then inject the second electrolyte into the battery cell. After 3 to 60 minutes, raise the temperature at both ends of the battery cell to cause the second electrolyte to undergo an in-situ polymerization reaction to obtain the polymer electrolyte. The polymer electrolyte fills the gaps at both ends of the positive electrode, the negative electrode, and the separator. S4. Perform the formation process to obtain the secondary battery; The secondary battery is a sodium-ion battery or a lithium-ion battery, and the first electrolyte comprises the following components by weight percentage: 5% to 29% conductive salt, 70% to 94% solvent, and 0.1% to 20% functional additives.

2. The secondary battery according to claim 1, characterized in that, The second electrolyte comprises the following components by weight percentage: 80% to 99.4% mother liquor, 0.5% to 15% monomer, and 0.01% to 5% initiator. The mother liquor comprises one or both of cyclic carbonates and chain carbonates.

3. The secondary battery according to claim 2, characterized in that, The mother liquor includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate.

4. The secondary battery according to claim 2, characterized in that, The monomer includes one or more of acrylamide, acrylamide derivatives, acrylates, acrylate derivatives, intermediates formed by homopolymerization of acrylamide or acrylamide derivatives, intermediates formed by copolymerization of acrylamide or acrylamide derivatives, intermediates formed by homopolymerization of acrylates or acrylate derivatives, and intermediates formed by copolymerization of acrylates or acrylate derivatives.

5. The secondary battery according to claim 2, characterized in that, The monomers include acrylamide, methacrylamide, styrene, isooctyl acrylate, isooctyl methacrylate, dodecyl acrylate, dodecyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, hexyl methacrylate, 2-cyclohexyl methacrylate, polyethylene glycol methacrylate, N-methacryloylmorpholine, N,N-dimethylacrylamide, methyl acrylate, ethyl acrylate, butyl acrylate, hexyl acrylate, 2-cyclohexyl acrylate, N-acryloylmorpholine, polyethylene glycol acrylate, hexyl glycol diacrylate, ethylene glycol diacrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, tetraethylene glycol diacrylate, tripropylene glycol diacrylate, pentaerythritol tetraacrylate ethoxylate, pentaerythritol tetraacrylate propionate, bis-trihydroxypropane tetraacrylate, pentaerythritol triacrylate, trihydroxymethyl Propane triacrylate, propoxylated glycerol triacrylate, tri(2-hydroxyethyl) isocyanurate triacrylate, propoxylated trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, pentaerythritol tetraacrylate, ethylene glycol dimethacrylate, ethylene glycol dimethacrylate, neopentyl glycol dimethacrylate, 1,6-hexanediol dimethacrylate, tetraethylene glycol dimethacrylate, tripropylene glycol dimethacrylate, ethoxylated pentaerythritol tetramethacrylate, propoxylated pentaerythritol tetramethacrylate, bis-trihydroxypropane tetramethacrylate, pentaerythritol trimethacrylate, trimethylolpropane trimethacrylate, propoxylated glycerol trimethacrylate, tri(2-hydroxyethyl) isocyanurate trimethacrylate, propoxylated trimethylolpropane trimethacrylate, ethoxylated trimethylolpropane trimethacrylate, pentaerythritol tetramethacrylate.

6. The secondary battery according to claim 2, characterized in that, The initiator includes one or more of peroxide initiators, redox initiators, and azo initiators.

7. The secondary battery according to claim 2, characterized in that, The initiators include cumene hydroperoxide, dicumene peroxide, di-tert-butyl peroxide, benzoyl peroxide, dodecyl peroxide, tert-butyl peroxide, tert-butyl pervalerate, diisopropyl peroxide, dicyclohexyl peroxide, tert-butyl hydroperoxide, methyl ethyl ketone peroxide, cyclohexanone peroxide, potassium persulfate, sodium persulfate, ammonium persulfate, benzoyl peroxide / sucrose, tert-butyl hydroperoxide / sodium thiosulfate, tert-butyl hydroperoxide / sodium metabisulfite, benzoyl peroxide / N,N-dimethylaniline, and persulfate. Ammonium / sodium bisulfite, potassium persulfate / sodium bisulfite, hydrogen peroxide / tartaric acid, hydrogen peroxide / sodium thiosulfate, ammonium persulfate / ferrous sulfate, hydrogen peroxide / ferrous sulfate, benzoyl peroxide / N,N-diethylaniline, benzoyl peroxide / ferrous pyrophosphate, potassium persulfate / silver nitrate, persulfate / thiol, cumene hydrogen peroxide / ferrous chloride, potassium persulfate / ferrous chloride, hydrogen peroxide / ferrous chloride, cumene hydrogen peroxide / tetraethyleneimine, azobisisoheptanenitrile, azobisisobutyronitrile, dimethyl azobisisobutyrate.

8. The secondary battery according to any one of claims 1 to 7, characterized in that, The in-situ polymerization reaction temperature of the second electrolyte is greater than or equal to 30°C.

9. The secondary battery according to any one of claims 1 to 7, characterized in that, The volume ratio of the second electrolyte injected in step S3 to the first electrolyte injected in step S2 is 1:10 to 100.

10. The secondary battery according to claim 1, characterized in that, The secondary battery is a sodium-ion battery, and the conductive salt includes one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium difluorophosphate, sodium bis(oxalate)borate, sodium difluorooxalateborate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, sodium difluorodioxalate phosphate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium difluorophosphate, lithium bis(oxalate)borate, lithium difluorooxalateborate, lithium bis(trifluoromethanesulfonyl)imide, and lithium difluorodioxalate phosphate.

11. The secondary battery according to claim 1, characterized in that, The secondary battery is a sodium-ion battery, and the solvent is water or a non-aqueous organic solvent. The non-aqueous organic solvent includes one or both of cyclic carbonates and chain carbonates.

12. The secondary battery according to claim 11, characterized in that, The non-aqueous organic solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate.

13. The secondary battery according to claim 1, characterized in that, The secondary battery is a sodium-ion battery, and the functional additive includes the following components in weight percentage: 0.1% to 99.7% fluoroethylene carbonate, 0.1% to 99.7% ethylene sulfate, and 0.1% to 99.7% 1-propylphosphonic anhydride.

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