Sustained release device for a battery, secondary battery comprising the same

Abstract

The present application provides a slow-release device for a battery, a secondary battery comprising the same. The slow-release device comprises a first capsule wall and a first release, the first capsule wall forms a first closed space and at least a part of the first capsule wall is composed of a first corrodible wall, and the part of the first capsule wall other than the first corrodible wall is neither soluble in nor chemically reactive with an electrolyte of the battery; the first release is contained in the first closed space; after the first corrodible wall is corroded and broken, the first release is released from the first closed space via the first corrodible wall; wherein the electrolyte comprises a fluorine-containing electrolyte and the first corrodible wall is made of silicate and / or oxide of silicon.

Description

Technical Field

[0001] This application relates to the field of lithium battery technology, and more particularly to a slow-release device for a battery and a secondary battery comprising the same. Background Technology

[0002] In recent years, with the increasingly wide application of lithium-ion batteries, they have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power plants, as well as in many fields such as power tools, electric bicycles, electric motorcycles, electric cars, military equipment, and aerospace.

[0003] However, when lithium-ion batteries are installed in the aforementioned electrical devices, their performance degrades over time, potentially posing safety hazards. Therefore, the industry has been searching for methods to reduce battery performance degradation during long-term use. Summary of the Invention

[0004] This application is made in view of the above-mentioned problems, and its purpose is to provide a device for reducing the performance degradation of a battery during long-term use, particularly a device for improving the cycle capacity retention rate of the battery, reducing the internal pressure of the battery, and extending the thermal propagation time.

[0005] To achieve the above objectives, this application provides a slow-release device for a battery and a secondary battery comprising the same.

[0006] A first aspect of this application provides a sustained-release device for a battery, the sustained-release device comprising a first capsule wall and a first release substance, characterized in that,

[0007] The first capsule wall forms a first enclosed space and at least a portion of the first capsule wall is composed of a first corrosive wall, and the portion of the first capsule wall other than the first corrosive wall is neither soluble in the electrolyte of the battery nor chemically reacts with the electrolyte;

[0008] The first released material is contained within the first enclosed space;

[0009] When the first corrosive wall is corroded and damaged, the first release material is released from the first enclosed space through the first corrosive wall;

[0010] The electrolyte contains a fluorinated electrolyte and the first corrosive wall is made of silicate and / or silicon oxide.

[0011] Therefore, this application provides a corrosive wall on the capsule wall of the slow-release device, which can break down on its own according to the degree of battery use without affecting the original performance of the battery cell, thereby releasing the release material and thus alleviating or even overcoming the problem of performance degradation in the later stages of battery use.

[0012] In any embodiment, the silicate is selected from at least one of sodium, potassium, calcium, magnesium, aluminum, and iron salts of silica; and the silicon oxide is silicon dioxide. This arrangement better ensures that the corrosive wall reacts with electrolyte byproducts and is gradually corroded after battery aging.

[0013] In any embodiment, the first capsule wall is made of a material selected from polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), polyvinyl chloride (PVC), polycarbonate (PC), polyamide (PA), and polytetrafluoroethylene (PTFE). This arrangement ensures that the portion of the first capsule wall, excluding the first corrosive wall, is neither soluble in nor chemically reacts with the electrolyte of the battery.

[0014] In any embodiment, the ratio of the surface area of ​​the first corrosive wall to the total surface area of ​​the first capsule wall is (0.005-1):1, optionally (0.01-0.5):1, or even optionally (0.02-0.2):1. This arrangement ensures that the released material can be smoothly released from the sustained-release device.

[0015] In any embodiment, the thickness of the portion of the first capsule wall excluding the first corrosive wall is 50-1000 μm, optionally 100-800 μm, or optionally 200-600 μm. This thickness setting not only reduces the weight percentage of the capsule wall but also ensures the structural reliability of the sustained-release device itself.

[0016] In any embodiment, the thickness of the first corrosive wall is not greater than the thickness of the portion of the first capsule wall excluding the first corrosive wall, and / or the thickness of the first corrosive wall is 10-800 μm, optionally 50-500 μm, or even 100-400 μm. This better ensures that the corrosive wall can release substances during the later stages of battery aging.

[0017] In any embodiment, the outer surface of the first capsule wall, excluding the first corrosive wall, is further coated with a transition metal scavenger. Optionally, the transition metal scavenger includes nitrile additives, such as p-fluorobenzonitrile or p-methylbenzonitrile. This method can further extend the battery's lifespan.

[0018] In any embodiment, the first release agent is at least one selected from electrolyte, electrolyte solution, and electrolyte additive. This arrangement allows for the containment of different release agents within the first enclosed space as needed.

[0019] In any embodiment, the sustained-release device further includes one or more capsule walls housed within the first enclosed space and nested sequentially. This arrangement enables a tiered release effect.

[0020] In any embodiment, the sustained-release device further includes a second and a third capsule wall housed within the first enclosed space and nested sequentially; optionally, at least one connecting member is provided between the first, second, and third capsule walls to fix them relatively. Providing connecting members between the capsule walls prevents relative rotation between them.

[0021] In any embodiment, at least a portion of the second capsule wall is formed by a second corrosive wall, and optionally at least a portion of the third capsule wall is formed by a third corrosive wall; the first corrosive wall, the second corrosive wall, and optionally the third corrosive wall are correspondingly arranged on the same side of the sustained-release device. The release of the released substance can be better achieved by arranging each corrosive wall on the same side.

[0022] In any embodiment, the thicknesses of the first corrosive wall, the second corrosive wall, and optionally the third corrosive wall increase sequentially, and / or the surface areas of the first corrosive wall, the second corrosive wall, and optionally the third corrosive wall decrease sequentially. This can differentiate the time intervals at which the release substances are released.

[0023] A second aspect of this application also provides a secondary battery, wherein the slow-release device described above is included inside the cell of the secondary battery.

[0024] In any embodiment, the slow-release device may be located above the bare cell of the battery cell, with the first corrosive wall facing the bare cell. This maximizes the contact area between the released material and the bare cell. Attached Figure Description

[0025] Figure 1 a is a front view of a sustained-release device according to an embodiment of this application.

[0026] Figure 1 b is a cross-sectional view of a sustained-release device according to an embodiment of this application.

[0027] Figure 2 This is a schematic diagram of a three-layer nested sustained-release device according to an embodiment of this application.

[0028] Figure 3 This is a schematic diagram showing the location of the slow-release device according to one embodiment of the present application inside the cell of a secondary battery.

[0029] Explanation of reference numerals in the attached figures:

[0030] 1 represents the first capsule wall.

[0031] 2 indicates the first corrosive wall.

[0032] 3 represents the first enclosed space.

[0033] 4 indicates the second enclosed space.

[0034] 5 indicates the third enclosed space. Detailed Implementation

[0035] The following detailed description, with appropriate reference to the accompanying drawings, discloses the battery-releasing device and the secondary battery comprising it. However, unnecessary details may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0036] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0037] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0038] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0039] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0040] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0041] After long-term testing of the battery's performance, the inventors of this application discovered:

[0042] During long-term use of lithium batteries, electrolyte consumption leads to a decline in battery performance, affecting battery lifespan and posing safety issues. The industry typically addresses electrolyte consumption by manually adding electrolyte externally. However, this method presents safety risks, and users may not be able to accurately determine the timing of replenishment, resulting in premature addition of electrolyte and other substances that lead to power and performance losses, such as affecting electrolyte viscosity or conductivity.

[0043] Based on this, the inventors discovered through extensive experimentation that by incorporating a corrosive structure into the bladder wall of the replenishment device, this structure can spontaneously break down according to the battery's usage level, thereby releasing the contents of the bladder. This method achieves automatic replenishment and, by differentiating the thickness of the corrosive structure, can also achieve phased release.

[0044] The sustained-release device of this application is particularly suitable for prismatic or pouch batteries.

[0045] The slow-release device of this application is particularly suitable for alleviating or even solving problems such as insufficient electrolyte, loss of active lithium, large gas production and thermal runaway in the later stage of cell aging.

[0046] Therefore, this application proposes a sustained-release device for a battery, the sustained-release device comprising a first capsule wall and a first release substance, characterized in that,

[0047] The first capsule wall forms a first enclosed space and at least a portion of the first capsule wall is composed of a first corrosive wall, and the portion of the first capsule wall other than the first corrosive wall is neither soluble in the electrolyte of the battery nor chemically reacts with the electrolyte;

[0048] The first released material is contained within the first enclosed space;

[0049] When the first corrosive wall is corroded and damaged, the first release material is released from the first enclosed space through the first corrosive wall;

[0050] The electrolyte contains a fluorinated electrolyte and the first corrosive wall is made of silicate and / or silicon oxide.

[0051] During the use of lithium batteries, hydrogen fluoride is generated through a side reaction in the fluorinated electrolyte. This hydrogen fluoride then corrodes the corrosive walls of the slow-release device, ultimately releasing the electrolyte and other substances contained within, achieving an automatic replenishment effect. Without affecting the original performance of the battery cell, this process can improve cycle capacity retention, battery life, reduce internal pressure, and shorten thermal runaway time.

[0052] In some embodiments, the size of the sustained-release device can vary depending on its usage environment, and there is no particular limitation on the number of sustained-release devices used; it mainly depends on the usage environment. Typically, when used inside the cell of a secondary battery, it can be cylindrical, with a diameter of 0.5-10 mm, optionally 1-8 mm, or 2-6 mm, and a length of 0.5-18 cm, optionally 1-15 cm, or 2-10 cm. The sustained-release device of the present invention can be installed within the internal space of the cell without increasing the overall volume of the cell, thereby improving space utilization. In particular, when the sustained-release device is located in the electrolyte, it can raise the liquid level, improve initial wettability, and simultaneously address the problem of insufficient electrolyte wetting of the cell after aging.

[0053] In some embodiments, the portion of the first capsule wall, excluding the first corrosive wall, is neither soluble in the battery electrolyte nor chemically reacts with the electrolyte. For example, the first capsule wall may be made of a material selected from polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), polyvinyl chloride (PVC), polycarbonate (PC), polyamide (PA), and polytetrafluoroethylene (PTFE). The use of this capsule wall ensures that the battery performance is not affected by its presence during use, and that substances released from the capsule wall are not released at unwanted times.

[0054] In some embodiments, the first release agent may be one or more of the following substances:

[0055] The electrolyte may be selected from at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiFSA), lithium difluorophosphate (LiPO2F2), lithium difluorooxalate borate (LiODFB), lithium dioxalate borate (LiBOB), lithium difluorodioxalate phosphate (LiDODFP), and lithium tetrafluorooxalate phosphate (LiOTFP);

[0056] The solvent may be selected from one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl 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), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0057] The flame retardant can be a conventional flame retardant used in the art, and the flame retardant can be selected from halogenated flame retardants, phosphorus-based flame retardants, and inorganic flame retardants. The halogenated flame retardant can be selected from decabromodiphenyl ethane, decabromodiphenyl ether, tetrabromobisphenol A, octabromoether, decabromodiphenyl ethane, tetrabromoether, brominated polystyrene, hexabromocyclododecane, chlorinated paraffin, decanoylene, and chlorinated polyethylene. The phosphorus-based flame retardant can be selected from melamine polyphosphate, phenoxypolyphosphazene compounds, triphenylphosphonate, resorcinol bisphosphonate, bisphenol A di(diphenyl)phosphonate, bisphenol A di(dimethyl)phosphonate, tris(2,2-dibromomethyl-3-bromopropylphosphonate), and isopropylated triphenyl phosphate. The inorganic flame retardant can be selected from aluminum hydroxide, magnesium hydroxide, red phosphorus, ammonium polyphosphate, zinc borate, and antimony oxide.

[0058] Lithium replenishment agents, which can be selected from Li, LiP, Li3P, Li3As, Li2Se or lithium silicide powder, can replenish the lithium lost during use and extend the life of the battery cell.

[0059] The gas absorbent can be selected from calcium oxide, calcium hydroxide, alkaline solution (such as NaOH / KOH), etc.; the gas absorbent can reduce the gas production and internal pressure at EOL (end of battery life, the same below) and reduce the risk of valve opening.

[0060] Transition metal scavengers can be nitrile additives, such as p-fluorobenzonitrile and p-methylbenzonitrile.

[0061] The aforementioned release agent can be disposed in one or more sustained-release devices. Particularly in the case of achieving cascaded release, the thickness of the corrosive wall on the capsule wall of each release agent device can be differentiated. For example, multiple sustained-release devices may differ in that the corrosive wall has the same area but different thicknesses. This arrangement allows for the cascaded release of different release agents at different aging stages.

[0062] In some embodiments, the first release agent is at least one selected from electrolyte, electrolyte solution, and electrolyte additive. This arrangement allows for the inclusion of different release agents within the first enclosed space as needed.

[0063] In some implementations, when the first release is electrolyte, it can replenish the electrolyte in a timely manner when it is depleted in the later stages of the battery life, enhance the wettability of the electrode, and avoid lithium plating and even cell degradation caused by insufficient electrolyte return in the central area due to electrolyte depletion and expansion force. This can improve EOL capacity retention, extend battery life, power performance, fast charging capability, etc.

[0064] In some embodiments, when the first release is a solid, its particle size is not particularly limited, as long as it can be easily released from the sustained-release device. However, for solid releases, it is preferable to have a smaller particle size, preferably a smaller Dv. 50 Not larger than 1 mm, or optionally not larger than 100 micrometers. In this document, unless otherwise specified, the median particle size Dv... 50 The detection method employed was the well-known electron microscopy statistical method.

[0065] In some embodiments, the surface area of ​​the first corrosive wall can be adjusted according to the usage environment, such as the amount of fluorinated electrolyte, the thickness of the corrosive wall, the number of sustained-release devices used, the cell size, available space, the area of ​​the corrosive wall, and its shape. Furthermore, if the area of ​​the corrosive wall is too small, it may affect the release of the released substance. Therefore, optionally, the ratio of the surface area of ​​the first corrosive wall to the total surface area of ​​the first capsule wall can be (0.005-1):1, optionally (0.01-0.5):1, or even optionally (0.02-0.2):1. This setting ensures that the released substance can be smoothly released from the sustained-release device.

[0066] In this application, the surface area of ​​the first corrosive wall should be understood as the surface area of ​​the side of the first corrosive wall away from the first enclosed space, that is, the surface area of ​​the side of the first corrosive wall exposed to the internal space of the battery cell or the electrolyte. Similarly, the total surface area of ​​the first capsule wall should be understood as the total surface area of ​​the side of the first capsule wall away from the first enclosed space.

[0067] In some embodiments, the thickness of the first capsule wall can vary within a wide range. When the thickness of the portion of the first capsule wall excluding the first corrosive wall is too large, the capsule wall will account for an excessively large proportion of the weight of the entire sustained-release device, which is detrimental to the utilization of space within the battery cell. When the thickness of the portion of the first capsule wall excluding the first corrosive wall is too small, there is a risk of unnecessary accidental rupture. Therefore, the thickness of the portion of the first capsule wall excluding the first corrosive wall can be, for example, 50-1000 μm, optionally 100-800 μm, or optionally 200-600 μm. This thickness setting not only reduces the weight proportion of the capsule wall but also ensures the structural reliability of the sustained-release device itself.

[0068] In some embodiments, the first corrosive wall is made of silicates and / or silicon oxides. Optionally, the first corrosive wall may also contain 1-20% by weight, optionally 5-15% by weight, of calcium oxide, based on the total weight of the first corrosive wall. The term "made of silicates and / or silicon oxides" as used herein should be understood to mean that the first corrosive wall not only contains silicates and / or silicon oxides but may also contain other substances, but the main component is silicates and / or silicon oxides. For example, the content of silicates and / or silicon oxides may be not less than 70% by weight, optionally not less than 80% by weight, based on the total weight of the first corrosive wall.

[0069] In some embodiments, the first etchable wall of this application can be formed by shaping particles of silicates and / or silicon oxides into a sheet with a certain rigidity in any manner. For example, if desired, the following raw materials are mixed in weight ratios and melted in a crucible (1320–1460 °C): 60–80% SiO2, 1–10% Na2O, 0.5–5% CaO, 0.5–5% NaCl, 0.01–0.5% MgO, 1–5% SrO, 1–3% B2O3, 0.5–2% Yb2O3, 0.001–0.01% lanthanum oxide / neodymium oxide / cerium oxide as additives respectively, 0.5–5% mica, 0.5–5% fumed silica, and the balance being silica sol (whose solid content may be 20–40% by weight), the sum of the weight percentages of all raw materials being 100% by weight. After degassing and degassing, the temperature is raised to 1520–1590°C and held to obtain a clear glass melt. This melt is then poured into a tin bath, spread, thinned, and polished to form a glass sheet. Following this, based on the desired thickness, it is tin-removed using an edge-drawing machine, annealed at 1000–1200°C, and finally ground, polished, cut, and chemically tempered before being slit into thin sheets. The thickness and shape can be adjusted as needed. Using the capsule wall material (e.g., polyethylene with a melting point of 130°C) used according to this invention, the capsule wall edges are finally bonded to silicate sheets and heat-fused together.

[0070] In some embodiments, the first etchable wall of this application is a common silicate glass, for example, whose composition is approximately Na2O·CaO·6SiO2.

[0071] In some embodiments, the first corrosive wall may be arranged along the outer circumference of the first capsule wall, that is, the corrosive wall is strip-shaped and arranged around the surface of the capsule wall and connected end to end. Optionally, the first corrosive wall is located at the center of the capsule wall of the sustained-release device. For example, when the sustained-release device is columnar, the first corrosive wall is located in the middle of the column. When the first corrosive wall is corroded and damaged, the capsule wall of the sustained-release device is divided into two parts that are not connected to each other, which makes it easier for the release substance to be released.

[0072] In some embodiments, the thickness of the first corrosive wall may not be greater than the thickness of the portion of the first capsule wall excluding the first corrosive wall. This is primarily to ensure that the corrosive wall can release substances during the later stages of battery aging. Optionally, the thickness of the first corrosive wall may be 10-800 μm, 50-500 μm, or 100-400 μm.

[0073] Although the aforementioned thickness is optional, those skilled in the art will know that the thickness of the first corrosive wall can also be determined based on factors such as the specific material used, the water content in the electrolyte, and the area of ​​the first corrosive wall.

[0074] In some embodiments, the silicate may be selected from at least one of sodium, potassium, calcium, magnesium, aluminum, and iron salts of silica; and the silicon oxide may be silicon dioxide. The corrosive wall material of this application can gradually corrode the corrosive wall by chemically reacting with HF, a byproduct of the battery electrolyte, after battery aging, thereby achieving the effects of identifying aging conditions and self-regulating the battery cell.

[0075] In some embodiments, the outer surface area and local roughness of the capsule wall can be increased by methods such as laser, die-cutting, and acid etching, followed by spraying a functional agent, such as a transition metal trapping agent, which can better extend the battery's lifespan. Therefore, the outer surface of the first capsule wall, excluding the first corrosive wall, can be sprayed with a transition metal trapping agent. Optionally, the transition metal trapping agent is a nitrile additive such as p-fluorobenzonitrile or p-methylbenzonitrile. Optionally, the trapping agent accounts for 0.01-8% by weight of the capsule wall, optionally 0.05-6% by weight, optionally 0.1-1% by weight. Optionally, the area of ​​the roughened region accounts for 0.1-10% of the total surface area of ​​the capsule wall, optionally 0.2-8%, optionally 0.5-5%. There are no particular restrictions on the size and shape of the depressions in the roughened region, but it is necessary to ensure that the roughened region has a certain strength, for example, the pressure threshold of the region is greater than 0.3 MPa, to prevent undesirable rupture in the roughened region. This method can further extend the battery's lifespan.

[0076] In some embodiments, the sustained-release device further includes one or more nested capsule walls housed within the first enclosed space, for example, two or three capsule walls may be nested within the first enclosed space. This multi-layered nested structure allows for the phased release of various substances from the battery at different aging stages. Figure 2 As shown.

[0077] In some embodiments, the sustained-release device further includes a second capsule wall housed within the first enclosed space, the second capsule wall forming a second enclosed space and at least a portion of the second capsule wall being composed of a second corrosive wall, and the portion of the second capsule wall other than the second corrosive wall being neither soluble in the electrolyte of the battery nor chemically reacting with the electrolyte;

[0078] The second enclosed space contains the second released material;

[0079] When the second corrosive wall is corroded and damaged, the second release material is released from the second enclosed space through the second corrosive wall;

[0080] The second corrosive wall is made of silicates and / or oxides of silicon.

[0081] With the aforementioned structural arrangement, even when the first and second corrosive walls have the same thickness and area, tiered release can be achieved. Specifically, compared to multiple independent slow-release devices, this nested structure can achieve the same tiered release effect using fewer corrosive walls. For example, with multiple independent identical slow-release devices, where each corrosive wall has the same surface area and thickness, tiered release requires differentiating the thickness of each corrosive wall. However, with the nested structure, it is not necessary to differentiate the thickness of each corrosive wall. Furthermore, this arrangement can improve the space utilization of the battery cell.

[0082] In some embodiments, the sustained-release device further includes a second and a third capsule wall housed within the first enclosed space and nested sequentially; optionally, at least one connecting member is provided between the first, second, and third capsule walls to fix them relatively. The connecting member can be a rigid plastic connector with its two ends connected to different capsule walls. Providing connecting members between the capsule walls prevents relative rotation between them.

[0083] In some embodiments, where two additional capsule walls are nested sequentially within the capsule wall of the sustained-release device, at least a portion of the second capsule wall is composed of a second corrosive wall, and optionally at least a portion of the third capsule wall is composed of a third corrosive wall; the first corrosive wall, the second corrosive wall, and optionally the third corrosive wall are correspondingly arranged on the same side of the sustained-release device. Arranging the corrosive walls on the same side allows for better release of the released substance.

[0084] In some embodiments, the thicknesses of the first corrosive wall, the second corrosive wall, and optionally the third corrosive wall increase sequentially, and / or the surface areas of the first corrosive wall, the second corrosive wall, and optionally the third corrosive wall decrease sequentially. By differentiating the thicknesses of each corrosive wall, the time intervals for the release of each release substance can be differentiated, thereby achieving a tiered release effect. Furthermore, setting the surface area of ​​the outermost first corrosive wall to be the largest among all corrosive walls can facilitate the release of the second release substance or optionally the third release substance.

[0085] In some embodiments, where two additional capsule walls are nested within the capsule wall of the sustained-release device, the first release agent is disposed between the first and second capsule walls; the second release agent is disposed between the second and third capsule walls. If the third release agent in the third enclosed space of the third capsule wall is a flame retardant, the third capsule wall may not contain a corrosive wall, but the material used to prepare the third capsule wall should have a relatively low melting or softening point, for example, below 150°C, preferably below 130°C, at which temperature the capsule wall will rupture and release the flame retardant.

[0086] In some embodiments, the third capsule wall is made of the same material as the second capsule wall and the first capsule wall.

[0087] In some embodiments, the first capsule wall of the slow-release device is further nested with two other capsule walls—a second capsule wall and a third capsule wall. The third enclosed space formed between the first and second capsule walls, between the second and third capsule walls, and by the third capsule wall contains electrolyte. The specific composition of the electrolyte may be the same as or different from the electrolyte used in the battery cell. During the initial stage of the battery's lifespan, the electrolyte is sufficient, and the slow-release device occupies a portion of the volume, raising the liquid level and improving initial wettability. However, with continued cycling and / or storage, battery aging intensifies, and the electrolyte is continuously consumed. The byproduct HF gradually accumulates and reacts with the corrosive walls. The slow-release device completely dissolves the corrosive walls layer by layer from the outside in, achieving a gradual and slow release of the electrolyte. This solves the problem of lithium plating and even cell degradation caused by insufficient electrolyte return in the central region due to electrolyte depletion and expansion forces in the later stages of the battery's lifespan, thereby extending battery life.

[0088] In some embodiments, the first capsule wall of the sustained-release device is further nested with two other capsule walls—a second capsule wall and a third capsule wall. The first release product between the first and second capsule walls is electrolyte, and the second release product between the second and third capsule walls is a gas absorbent or lithium replenishing agent. The third enclosed space formed by the third capsule wall contains a flame retardant. In the early stages of the battery's life, when the electrolyte is plentiful, the sustained-release device occupies a portion of the volume, raising the electrolyte level in the battery and resulting in good initial wettability. As cycling and / or storage continue, the battery ages rapidly, and the electrolyte is continuously consumed. The by-reaction product HF gradually accumulates and continuously reacts with silicates or silicon oxides that can corrode the battery walls. The outermost corrosive wall preferentially dissolves completely with HF and ruptures, releasing the electrolyte and replenishing the consumed electrolyte. As by-reaction products continue to accumulate, the next outermost corrosive wall gradually reacts completely with HF and ruptures, releasing the gas absorbent and effectively absorbing internal gases. This alleviates internal pressure and reduces the risk of valve opening, or releases lithium replenishing agent to compensate for lithium loss in the later stages of use. When battery abuse or cell defects or lithium dendrite accumulation at the end of the battery's lifespan cause lithium dendrites to pierce the separator and eventually lead to thermal runaway, the temperature instantly increases to the melting point of the capsule wall material, and the internal pressure increases sharply, causing the capsule wall to rupture. The innermost flame retardant is released, achieving rapid cooling and controlling the degree of thermal runaway, thus improving safety.

[0089] The capsule-shaped sustained-release device of this application can be prepared by methods known in the art, such as by melt casting to prepare a capsule-shaped structure with notches. After the release agent is placed inside, a sheet made of silicate and / or oxide is connected and sealed at the notch by heat fusion. In the case of preparing a multi-layered nested structure, it can be prepared layer by layer from the inside out. For example, the third capsule wall is prepared first, and then the second capsule wall and the first capsule wall are prepared in sequence.

[0090] In this application, unless otherwise stated, the descriptions of the first capsule wall and the first corrosive wall also apply to the second capsule wall, the third capsule wall, and the second and third corrosive walls. Those skilled in the art will also understand that, due to the nested structure of this application, the main difference between the first, second, and third capsule walls lies in their dimensions; that is, the first enclosed space formed by the first capsule wall is larger than the second enclosed space formed by the second capsule wall, and the second enclosed space is larger than the third enclosed space formed by the third capsule wall. In particular, the materials, thicknesses, and proportions of the corrosive wall area to the total surface area of ​​the capsule walls, as well as the materials and thicknesses of the corrosive walls, can all be configured similarly for the three types of capsule walls.

[0091] Another aspect of this application provides a secondary battery in which the aforementioned slow-release device is included inside the battery cell.

[0092] In some embodiments, the sustained-release device can be located in any space inside the cell of the secondary battery, as long as it achieves the purpose of the invention. For example, the sustained-release device can be located around, above, and in other spaces of the bare cell. For example, one side of the capsule-shaped sustained-release device can be attached to the inner wall of the cell housing or the explosion-proof valve by, for example, an adhesive. In this application, for clarity, "above" should be understood as the side of the bare cell closest to the safety valve.

[0093] In some embodiments, the slow-release device may be located above the bare cell of the secondary battery cell, with the first corrosive wall facing the bare cell. When the first corrosive wall is damaged, the released material can maximize its contact area with the bare cell under the influence of gravity. In this application, the term "bare cell" should be understood as a device comprising a positive electrode, a negative electrode, a separator, a positive electrode tab, and a negative electrode tab, the separator being disposed between the positive and negative electrode, the positive electrode, the separator, and the negative electrode being formed by winding, stacking, or folding. The bare cell is further processed, such as through encapsulation, electrolyte injection, formation, and degassing processes, to form a battery cell. The resulting battery cell can be used directly after installing elements such as protection circuitry and a casing.

[0094] Typically, during the charging and discharging process of a secondary battery, active ions repeatedly insert and extract between the positive and negative electrode plates. The electrolyte acts as a conductor of ions between the positive and negative electrode plates. The separator, positioned between the positive and negative electrode plates, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through. In this application, unless otherwise stated, the positive electrode plate, negative electrode plate, electrolyte, and separator in the secondary battery are those conventionally used in the art.

[0095] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0096] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0097] Example

[0098] The following embodiments are used to illustrate this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0099] Example 1

[0100] Example 1a

[0101] The structure of the slow-release device for secondary batteries is as follows: Figure 1 a and Figure 1 As shown in b, the sustained-release device is capsule-shaped, with a polyethylene film wall material of 400 μm thickness. The device has a diameter of 3 mm and a height of 6 cm. At the center is a 4 mm * 20 mm corrosive wall (approximately 14% of the total surface area of ​​the capsule wall), with a thickness of 100 μm. The corrosive wall is prepared by the following method (all corrosive walls in the following examples are prepared using this method):

[0102] The following raw materials were mixed in the following weight ratios and melted in a crucible (1450℃): 70% SiO2, 5% Na2O, 1% CaO, 1% NaCl, 0.1% MgO, 5% SrO, 3% B2O3, 1% Yb2O3, 0.005% lanthanum oxide as an additive, 2% mica, 1% fumed silica, and the balance being silica sol (purchased from Maclean, model S888350, silica content 30% ± 1%). The total weight percentage of all raw materials was 100% by weight. After degassing, the temperature was raised to 1550℃ and held to obtain a clear glass melt. This melt was then poured into a tin bath, spread, thinned, and polished to form a glass plate. Following this, the glass was tin-removed using an edge-drawing machine to achieve the desired thickness, then annealed at 1000℃. Finally, it was ground, polished, cut, chemically tempered, and slit into thin sheets. The thickness and shape can be adjusted as needed; finally, the corrosive wall is heat-fused to the polyethylene film at the edges (at a temperature of 140°C) to form a bond.

[0103] The total amount of ethylene carbonate released within the enclosed spaces of the 10 capsule-shaped sustained-release devices in the secondary battery is 2.4 g.

[0104] Example 1b

[0105] Except that the aforementioned capsule-shaped slow-release device was placed in the two side gaps inside the cell, the battery was prepared in the same manner as in Example 1a.

[0106] Example 2

[0107] The structure of the sustained-release device is similar to that of Example 1, wherein the sustained-release device is capsule-shaped, and the capsule wall material is a polyethylene film with a thickness of 400 μm. The device has a diameter of 3 mm, a height of 5 cm, and a 2 mm * 10 mm corrosive wall (accounting for approximately 4% of the total surface area of ​​the capsule wall) with a thickness of 150 μm in the center.

[0108] The total amount of calcium oxide released within the enclosed spaces of the 12 capsule-shaped sustained-release devices in the secondary battery is 45 mg.

[0109] Example 3

[0110] The structure of the sustained-release device is the same as that in Example 2, wherein the thickness of the corrosive wall is 300 μm, and the total amount of released material contained in the closed space of the 15 capsule-shaped sustained-release devices is 150 mg of tributyl phosphate.

[0111] Example 4

[0112] Structure as Figure 2 As shown, the sustained-release device has a three-layer nested structure, wherein the sustained-release device is capsule-shaped, the capsule wall material is polyethylene film, and the thickness of each layer is 400μm.

[0113] The outermost layer has a diameter of 4mm and a height of 8cm. In the center, there is a 4mm*20mm corrosive wall (accounting for about 8% of the total surface area of ​​the capsule wall) with a thickness of 100μm.

[0114] The outermost layer has a diameter of 2mm and a height of 5cm, with a 2mm*10mm corroded wall in the center and a thickness of 150μm.

[0115] The innermost layer has a diameter of 1mm and a height of 3cm, with a 1mm*5mm corroded wall in the center and a thickness of 200μm.

[0116] In the five capsule-shaped sustained-release devices in the secondary battery, the first release material between the first capsule wall and the second capsule wall totals 2.2g of electrolyte (1M LiPF6+EC / DEC / EMC (weight ratio of 5:2:3)).

[0117] The second release between the second and third capsule walls totaled 80 mg of calcium oxide.

[0118] The total amount of the third release within the enclosed space of the third capsule wall was 50 mg of tributyl phosphate.

[0119] The corrosive walls of each layer are all on the same side of the slow-release device.

[0120] Example 5

[0121] The structure of the sustained-release device is similar to that of Example 4, except that the total amount of the first release product in the eight capsule-shaped sustained-release devices is 3.5g of electrolyte; the total amount of the second release product is 120mg of calcium oxide; and the total amount of the third release product is 80mg of tributyl phosphate.

[0122] Example 6

[0123] This embodiment uses a total of 10 sustained-release devices with structures similar to those in Embodiment 1b. The difference is that the outermost part of the capsule wall of each sustained-release device, excluding the corrosive wall, is roughened by laser etching, and then a layer of p-fluorobenzonitrile (0.4% by weight of the capsule wall) is sprayed on. The area of ​​the roughened area accounts for 7% of the total surface area of ​​the capsule wall.

[0124] The arrangement of the aforementioned capsule-shaped sustained-release device inside the battery cell is shown in Table 1 below.

[0125] Performance testing

[0126] Cyclic capacity retention rate at 1000cls is determined according to the following method:

[0127] Under a constant temperature environment of 25℃, the test voltage range is 2.5-4.3V. The cells are fully charged at 0.5C and then charged at a constant voltage until the current is ≤0.05mA. After resting for 5 minutes, they are discharged at 0.5C to 2.5V. The capacity is recorded as Dn (n=1,2,3……). This process is repeated for 1000 cycles (i.e., 1000cls). The capacity decay value is measured in each cycle. The capacity decay is expressed as the ratio of Dn / D3 as the cell's State of Health (SOH), which serves as an indicator of cycle performance.

[0128] Internal pressure (gas production) @ 200 days, 60℃ storage should be carried out according to the following method:

[0129] An internal pressure detection device is installed on the battery cell. Specifically, the liquid injection port on the battery cell is connected to the pressure detection device through a conduit to detect the internal air pressure of the battery cell. The battery cell is stored at 60°C for 200 days, and the internal pressure (i.e., internal pressure) is recorded after 200 days.

[0130] Thermal propagation @ thermal runaway time of adjacent cells is determined using the following method:

[0131] Under a constant temperature of 25℃, the battery cells are fully charged and a heating device is installed, with the battery cells placed side by side. One of the battery cells is heated until it experiences thermal runaway. The time it takes for the other adjacent battery cell to experience thermal runaway is observed; this is the thermal propagation time.

[0132] The square-shaped secondary battery used in the performance test has a size of 30*15*100mm.

[0133] Table 1: Performance test results of Examples 1-6 and Comparative Example 1

[0134]

[0135] As can be seen from the above results, Examples 1-6 all achieved good results. Specifically, compared with Comparative Example 1, which did not use the sustained-release device of the present invention, Examples 1-6, which used the sustained-release device of the present invention, show that the use of the sustained-release device significantly improved the cycle capacity retention rate of the battery, reduced the internal pressure of the battery, and extended the heat spread time.

[0136] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A sustained-release device for a battery, the sustained-release device comprising a first capsule wall and a first release substance, characterized in that, The first capsule wall forms a first enclosed space and at least a portion of the first capsule wall is composed of a first corrosive wall, and the portion of the first capsule wall other than the first corrosive wall is neither soluble in the electrolyte of the battery nor chemically reacts with the electrolyte; The first released material is contained within the first enclosed space; When the first corrosive wall is corroded and damaged, the first release material is released from the first enclosed space through the first corrosive wall; The electrolyte contains a fluorinated electrolyte and the first corrosive wall is made of silicate and / or silicon oxide.

2. The sustained-release device according to claim 1, characterized in that, The silicate is selected from at least one of sodium, potassium, calcium, magnesium, aluminum and iron salts of silicic acid; and the oxide of silicon is silicon dioxide.

3. The sustained-release device according to claim 1, characterized in that, The first capsule wall is made of a material selected from the following: polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), polyvinyl chloride (PVC), polycarbonate (PC), polyamide (PA), and polytetrafluoroethylene (PTFE).

4. The sustained-release device according to any one of claims 1 to 3, characterized in that, The ratio of the surface area of ​​the first corrosive wall to the total surface area of ​​the first capsule wall is (0.005-1):

1.

5. The sustained-release device according to any one of claims 1 to 3, characterized in that, The ratio of the surface area of ​​the first corrosive wall to the total surface area of ​​the first capsule wall is (0.01-0.5):

1.

6. The sustained-release device according to any one of claims 1 to 3, characterized in that, The ratio of the surface area of ​​the first corrosive wall to the total surface area of ​​the first capsule wall is (0.02-0.2):

1.

7. The sustained-release device according to any one of claims 1 to 3, characterized in that, The thickness of the portion of the first capsule wall excluding the first corrosive wall is 50-1000 μm.

8. The sustained-release device according to any one of claims 1 to 3, characterized in that, The thickness of the portion of the first capsule wall excluding the first corrosive wall is 100-800 μm.

9. The sustained-release device according to any one of claims 1 to 3, characterized in that, The thickness of the portion of the first capsule wall excluding the first corrosive wall is 200-600 μm.

10. The sustained-release device according to any one of claims 1 to 3, characterized in that, The thickness of the first corrosive wall is not greater than the thickness of the portion of the first capsule wall excluding the first corrosive wall, and / or the thickness of the first corrosive wall is 10-800 μm.

11. The sustained-release device according to any one of claims 1 to 3, characterized in that, The thickness of the first corrosive wall is not greater than the thickness of the portion of the first capsule wall excluding the first corrosive wall, and / or the thickness of the first corrosive wall is 50-500 μm.

12. The sustained-release device according to any one of claims 1 to 3, characterized in that, The thickness of the first corrosive wall is not greater than the thickness of the portion of the first capsule wall excluding the first corrosive wall, and / or the thickness of the first corrosive wall is 100-400 μm.

13. The sustained-release device according to any one of claims 1 to 3, characterized in that, The outer surface of the first capsule wall, excluding the first corrosive wall, is also coated with a transition metal trapping agent.

14. The sustained-release device according to claim 13, characterized in that, The transition metal scavenger includes nitrile additives.

15. The sustained-release device according to claim 13 or 14, characterized in that, The transition metal scavenger is p-fluorobenzonitrile or p-methylbenzonitrile.

16. The sustained-release device according to any one of claims 1 to 3, characterized in that, The first release is at least one of electrolyte, electrolyte, and electrolyte additive.

17. The sustained-release device according to any one of claims 1 to 3, characterized in that, The sustained-release device also includes one or more capsule walls that are nested within the first enclosed space.

18. The sustained-release device according to claim 17, characterized in that, The sustained-release device further includes a second capsule wall and a third capsule wall that are nested within the first enclosed space.

19. The sustained-release device according to claim 18, characterized in that, At least one connecting member is provided between the first capsule wall, the second capsule wall and the third capsule wall to fix them relative to each other.

20. The sustained-release device according to claim 18, characterized in that, At least a portion of the second capsule wall is composed of a second corrosive wall; the first corrosive wall and the second corrosive wall are respectively disposed on the same side of the sustained-release device.

21. The sustained-release device according to claim 18, characterized in that, At least a portion of the second capsule wall is formed by a second corrosive wall and at least a portion of the third capsule wall is formed by a third corrosive wall; the first corrosive wall, the second corrosive wall and the third corrosive wall are respectively disposed on the same side of the sustained-release device.

22. The sustained-release device according to claim 20 or 21, characterized in that, The thickness of the first corrosive wall and the second corrosive wall increases sequentially, and / or the surface area of ​​the first corrosive wall and the second corrosive wall decreases sequentially.

23. The sustained-release device according to claim 20 or 21, characterized in that, The thicknesses of the first corrosive wall, the second corrosive wall, and the third corrosive wall increase sequentially, and / or the surface areas of the first corrosive wall, the second corrosive wall, and the third corrosive wall decrease sequentially.

24. A secondary battery, characterized in that, The secondary battery cell includes a slow-release device as described in any one of claims 1 to 23.

25. The secondary battery according to claim 24, characterized in that, The slow-release device is located above the bare cell of the battery cell, with the first corrosive wall facing the bare cell.

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