A secondary battery

Abstract

The present invention discloses a secondary battery, which relates to the field of battery technology. The secondary battery includes: m first battery cell units and n second battery cell units, each of the first battery cell units includes a first positive electrode current collector, a first positive electrode active material layer arranged on the first positive electrode current collector, a first negative electrode active material layer and a barrier film arranged between the first positive electrode active material layer and the first negative electrode active material layer, each of the second battery cell units includes a protective film and a second negative electrode active material layer, the protective film and the second negative electrode active material layer are arranged relatively, and n≥1. The present invention can improve the ability of the secondary battery to resist the impact of heavy objects, effectively alleviate the instantaneous short circuit caused by the rupture of the barrier film, and avoid the phenomenon of the secondary battery catching fire or even exploding in a short time.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a secondary battery. Background Art

[0002] Secondary batteries have developed rapidly and are widely used in energy storage fields, such as portable electronic devices and mobile devices. At the same time, the safety of secondary batteries has attracted widespread attention. During transportation and use, secondary batteries are very prone to fire and explosion when hit by heavy objects, causing serious safety problems.

[0003] For square-shell batteries, such problems mainly occur at the tabs due to the protection of the external shell, while for soft-pack batteries, since there is only a layer of aluminum-plastic film on the outside, they are particularly susceptible to impact or puncture.

[0004] In this regard, there are some solutions in the prior art. For example, the Chinese patent with publication number CN106207087A covers the positive and negative pole pieces with a layer of nanofilm to solve the problem of short circuits in secondary batteries under extreme conditions such as needle puncture, falling, and heavy object impact; the Chinese patent with publication number CN108346816A covers the outside of the battery cell with a high-temperature resistant film to effectively isolate the positive and negative pole pieces to avoid large-area short circuits and thermal runaway. Although the above solutions can solve the problem of short circuits and fires in batteries due to impacts to a certain extent, they generally bring new problems, such as affecting the transmission efficiency of lithium ions, complex processes, and excessive costs.

[0005] Therefore, there is an urgent need to provide a new secondary battery to solve the above problems. Summary of the invention

[0006] The present invention provides a secondary battery, which can improve the ability of the secondary battery to resist the impact of heavy objects, effectively alleviate the instantaneous short circuit caused by the rupture of the barrier film, and avoid the phenomenon of the secondary battery catching fire or even exploding in a short time.

[0007] The present invention provides the following scheme:

[0008] A secondary battery comprises: m first battery cell units and n second battery cell units, each of the first battery cell units comprises a first positive electrode current collector, a first positive electrode active material layer arranged on the first positive electrode current collector, a first negative electrode active material layer and a barrier film arranged between the first positive electrode active material layer and the first negative electrode active material layer, each of the second battery cell units comprises a protective film and a second negative electrode active material layer, the protective film and the second negative electrode active material layer are arranged relative to each other, and n≥1.

[0009] Preferably, the protective film comprises a polymer matrix material;

[0010] Preferably, the polymer matrix material in the protective film includes at least one of polyolefin, polyamide, epoxy resin, polystyrene, polyurethane, polyvinyl chloride, polycarbonate, polyvinyl alcohol, polymethyl methacrylate, polyethylene terephthalate, poly(p-phenylene benzobisazole), and polyimide;

[0011] Preferably, the protective film further comprises a flame retardant;

[0012] Preferably, the flame retardant includes an additive flame retardant and a reactive flame retardant;

[0013] Preferably, the protective film comprises a polymer film formed by the polymer matrix material and a flame retardant layer arranged on the surface of the polymer film.

[0014] Preferably, the thickness of the protective film is 10-5000 μm, preferably, the thickness of the protective film is 100-500 μm.

[0015] Preferably, the protective film and the first positive electrode active material layer are arranged on both sides of the same current collector, and the protective film covers the current collector.

[0016] Preferably, the second battery cell unit comprises two second negative electrode active material layers arranged opposite to each other, and the protective film is located between the two second negative electrode active material layers.

[0017] Preferably, the protective film is formed by a polymer film stack formed by two or more polymer matrix materials;

[0018] Preferably, in the protective film, each polymer film is made of the same material.

[0019] Preferably, in at least one of the protective films, at least two polymer films are made of different materials.

[0020] Preferably, in the secondary battery, the structure of the protective film of each second battery cell unit is completely the same; or

[0021] In the secondary battery, at least two protection films in each second battery cell unit have different structures.

[0022] Preferably, the second battery cell unit is arranged between any two first battery cell units or is located at the outermost side of the secondary battery;

[0023] Preferably, two or more second battery core units are arranged between any two first battery core units or are located at the outermost side of the secondary battery.

[0024] Preferably, the relationship between the number m of the first battery cell units and the number n of the second battery cell units is, m>n;

[0025] Preferably, the second battery cell unit is arranged between two groups of first battery cell unit stacks consisting of a plurality of first battery cell units, and the difference in the number of first battery cell units in the two groups of first battery cell unit stacks is m1, wherein m1≤1;

[0026] Preferably, the number of the first battery cell units in the first battery cell unit stack is m2, and 10≤m2≤15, preferably, 12≤m2≤14.

[0027] Preferably, the numbers of first battery cell units in the first battery cell unit stacks on both sides of the second battery cell unit are not the same;

[0028] Preferably, the first battery cell unit stacks on both sides of the second battery cell unit include m3 first battery cell units, wherein 1≤m3≤20, preferably, 1≤m3≤15.

[0029] Optionally, the first battery cell unit and the second battery cell unit are stacked and connected in parallel to obtain the secondary battery.

[0030] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0031] The present invention obtains a secondary battery by combining two battery cell units, and the positive electrode plate in the second battery cell unit is replaced with a protective film. The protective film provides protection for the secondary battery, which can effectively improve the ability of the secondary battery to resist the impact of heavy objects, play a role in shock absorption and pressure prevention, effectively alleviate the instantaneous short circuit caused by diaphragm rupture, and avoid short-term fire or even explosion. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 is a schematic cross-sectional structure diagram of a secondary battery provided by one embodiment of the present invention;

[0034] Figure 2 It is a schematic cross-sectional structure diagram of a secondary battery provided by another embodiment of the present invention. DETAILED DESCRIPTION

[0035] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0036] It should be noted that the descriptions of the present invention regarding directions such as "left", "right", "left side", "right side", "upper", "lower", "top", "bottom", etc. are all defined based on the relationship between the orientations or positions shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the structure described must be constructed and operated in a specific orientation, and therefore, cannot be understood as a limitation on the present invention. In the description of the present invention, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0037] In the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0038] In response to the technical problems raised by the above background technology, the present application provides a secondary battery. Figure 1 FIG. 1 is a schematic cross-sectional view of a secondary battery provided by an embodiment of the present invention. Figure 1 As shown, the secondary battery includes m first battery cell units 100 and n second battery cell units 200, each of the first battery cell units 100 includes a first positive electrode current collector 111, a first positive electrode active material layer 112 arranged on the first positive electrode current collector 111, a first negative electrode active material layer 122 and a barrier film 130 arranged between the first positive electrode active material layer 112 and the first negative electrode active material layer 122, each of the second battery cell units 200 includes a protective film 210 and a second negative electrode active material layer 222, the protective film 210 and the second negative electrode active material layer 222 are arranged opposite to each other, and n≥1.

[0039] It is understood that in the present application, each of the first battery cell units 100 includes a positive electrode sheet 110, a first negative electrode sheet 120 and the barrier film 130, the positive electrode sheet 110 includes the first positive current collector 111 and the first positive active material layer 112 disposed on the first positive current collector 111, and the first negative electrode sheet 120 includes the first negative current collector 121 and the first negative active material layer 122 disposed on the first negative current collector 121; each of the second battery cell units 200 includes a protective film 210 and a second negative electrode sheet 220, and the second negative electrode sheet 220 includes a negative current collector and the second negative active material layer 222 disposed on the negative current collector. It is understood that due to the use of a laminated or wound design inside the battery, the second negative active material layer 222 of the second battery cell unit 200 and the first active material layer 122 of the first battery cell unit 100 share the same current collector, that is, double-sided coating on both sides of the same current collector.

[0040] In some embodiments, the protective film 210 includes a polymer matrix material.

[0041] Further preferably, the protective film 210 further includes a flame retardant.

[0042] It is understandable that, due to the use of a polymer matrix material, the protective film 210 is in the shape of a polymer film and has a certain toughness, and after the flame retardant is added, the protective film 210 has flame retardant properties.

[0043] It is understandable that the protective film 210 should be chemically inert to the electrolyte and the battery, that is, it will not chemically or physically interact with the relevant components in the battery in the electrochemical environment.

[0044] As an example only, and not any limitation to the scope of protection, in the present invention, the polymer matrix material in the protective film 210 includes at least one of polyolefin, polyamide, epoxy resin, polystyrene, polyurethane, polyvinyl chloride, polycarbonate, polyvinyl alcohol, polymethyl methacrylate, polyethylene terephthalate, poly(p-phenylene benzobisoxazole), and polyimide.

[0045] Furthermore, the polyolefin includes at least one of polypropylene and polyethylene, and the polymer film includes a film made of polypropylene or polyethylene or a mixture of the two.

[0046] Furthermore, the polyamide includes meta-aramid.

[0047] In the present invention, there is no limitation on the method of adding the flame retardant to the protective film 210. Without violating the inventive concept of the present application, any known method of adding the flame retardant to the polymer film can be used in the present invention, including but not limited to directly mixing the polymer matrix material with the flame retardant.

[0048] As a preferred example of the present application, the protective film includes a polymer film formed by the polymer matrix material and a flame retardant layer is arranged on the surface of the polymer film formed by the polymer matrix material.

[0049] The present application does not specifically limit the type of flame retardant, and any known type of flame retardant can be used in the present invention. It is only used as an illustrative example rather than a limitation on the scope of protection. The flame retardant is one or both of an additive flame retardant and a reactive flame retardant.

[0050] Exemplarily, the flame retardant may be a phosphorus-containing flame retardant, including at least one of melamine polyphosphate, melamine cyanurate, decabromodiphenylethane, trichloropropyl phosphate, polyphosphoric acid amine, and dimethyl methyl phosphate.

[0051] Optionally, the flame retardant can be directly doped into the raw materials during the preparation of the polymer film, and the polymer material reacts with the flame retardant to form a protective film 210, that is, the components of the polymer film also include the flame retardant. The flame retardant can also be doped in the coating of the polymer film, and can also be directly coated on the surface of the polymer film. The flame retardant can also be located in the voids of the porous polymer film.

[0052] The surface of the polymer film is coated with a coating, such as a ceramic coating. As mentioned above, the coating may also be doped with a flame retardant.

[0053] In one embodiment, the protective film 210 has a thickness of 10-5000 μm.

[0054] In a preferred embodiment, the thickness of the protective film 210 is 100-500 μm.

[0055] Figure 2 FIG. 1 is a schematic cross-sectional view of a secondary battery provided by another embodiment of the present invention. Figure 2 As shown, as an implementation mode, the protective film 210 and the first positive electrode active material layer 112 are arranged on both sides of the same current collector, and the protective film 210 covers the current collector.

[0056] More preferably, the second negative electrode active material layer 222 is the same as the first negative electrode active material layer 122 .

[0057] It can be understood that the first negative electrode active material layer 122 and the second negative electrode active material layer 222 are the same in that they have the same structure and composition, that is, their physical, chemical, and electrochemical properties are consistent at the industrial manufacturing level, and they have the same capacity, surface density and other related parameters.

[0058] As an embodiment, the second negative electrode active material layer 222 is different from the first negative electrode active material layer 122 .

[0059] As an embodiment, the second battery cell unit 200 includes two second negative electrode active material layers that are arranged opposite to each other, and the protection film 210 is located between the two second negative electrode active material layers.

[0060] contrast Figure 1 and Figure 2 It can be found that the present application provides two solutions. When the battery safety requirement is not high, the protective film 210 can be directly attached to the positive electrode current collector so that the protective film 210 replaces a positive electrode active material layer (such as Figure 2 When the battery safety requirement is high, the protective film 210 can be a separate structure, directly replacing the positive electrode composed of the second positive electrode active material layer and the second positive electrode current collector (as shown in FIG. Figure 1 shown).

[0061] As an implementation manner, the protection film 210 is formed by a polymer film stack formed by two or more polymer matrix materials.

[0062] Further preferably, in the protective film 210 , each polymer film is made of the same material.

[0063] Further preferably, in at least one of the protective films 210 , at least two polymer films are made of different materials.

[0064] As an implementation manner, in the secondary battery, the structure of the protection film 210 of each second battery cell unit 200 is completely the same.

[0065] As an implementation manner, in the secondary battery, at least two protection films 210 in each second battery cell unit 200 have different structures.

[0066] It can be understood that the structure of the protective film 210 and the polymer film can include multiple aspects, such as thickness, number, method of adding flame retardants, whether coated with a ceramic layer, composition of the ceramic layer, etc. Any factors that change the flame retardancy, safety, electrochemical properties, etc. of the protective film and polymer film can be understood as the structure here.

[0067] In actual use, there are different heat distributions and heat accumulations inside the battery. Therefore, setting protective films with different performances according to the heat distribution phenomenon inside the battery is beneficial to the overall performance of the battery. For example, a protective film with higher safety performance is set for areas with more serious heat accumulation, and a protective film with lower safety performance is set for areas with less heat accumulation.

[0068] Preferably, the protection film structure corresponds to the internal safety distribution of the battery.

[0069] It can be understood that the internal safety distribution of the battery refers to the distribution points of risks at different locations within the battery, that is, where risks are likely to occur, a protective film structure with better safety performance is set. Correspondingly, where the risk points are low, a protective film with low safety performance is set to meet the requirements of other battery performance.

[0070] As an embodiment, in the second battery, the thickness of the protective film 210 of each second battery cell unit 200 is the same.

[0071] As an implementation manner, in the secondary battery, the thickness of the protective film 210 of each second battery cell unit 200 is different.

[0072] It is understood that the thickness here refers to the overall thickness of a single-layer protective film. When the protective film is composed of multiple polymer films, the thickness should be the sum of the thicknesses of all polymer films constituting the protective film and related structures on the polymer film layer.

[0073] It is understandable that, under the premise of a certain number of battery cells, the more the number of second battery cells 200 is, the more conducive it is to improving the impact resistance, but the battery capacity loss will increase accordingly, which is not conducive to the performance of the battery capacity. Therefore, it is necessary to control the number of second battery cells 200 to be within a reasonable range, so as to ensure that the battery capacity loss is minimized and a good heavy object impact resistance effect can be achieved.

[0074] Preferably, the second battery cell unit 200 is disposed between any two first battery cell units 100 or is located at the outermost side of the secondary battery.

[0075] Preferably, two or more second battery cell units 200 are disposed between any two first battery cell units 100 or are located at the outermost side of the secondary battery.

[0076] In one embodiment, the first battery cell units 100 and the second battery cell units 200 are evenly and spaced apart in the secondary battery. In this way, the best impact resistance can be achieved with the least number of protective films 210. In one embodiment, in the secondary battery, the second battery cell units 200 are located between the first battery cell units 100, and the relationship between the number m of the first battery cell units 100 and the number n of the second battery cell units 200 is m>n.

[0077] In one embodiment, the second battery cell unit 200 is disposed between two groups of a plurality of first battery cell unit stacks, the number difference between the two groups of first battery cell unit stacks is m1≤1, and the first battery cell unit stack includes m2 first battery cell units 100, wherein 10≤m2≤15.

[0078] In a preferred embodiment, 12≤m2≤14.

[0079] Furthermore, the n second battery cell units 200 are evenly arranged in n+1 groups of first battery cell unit stacks consisting of m2 first battery cell units 100 .

[0080] In one embodiment, the number of first battery cell units 100 in the first battery cell unit stacks on both sides of the second battery cell unit 200 is not the same, wherein the first battery cell unit stacks on both sides of the second battery cell unit 200 include m3 first battery cell units 100, wherein 1≤m3≤20.

[0081] In a preferred embodiment, m3≤15.

[0082] The first battery cell unit 100 and the second battery cell unit 200 in another example of the present application, the first battery cell unit 100 and the second battery cell unit 200 are spaced apart and unevenly arranged in the secondary battery.

[0083] As an optional example of the present application, the first battery cell unit 100 and the second battery cell unit 200 are stacked and connected in parallel to obtain the secondary battery.

[0084] As a preferred example of the present application, the positive electrode sheet 110 , the first negative electrode sheet 120 and the second negative electrode sheet 220 are all coated on both sides, that is, the positive electrode sheet 110 , the first negative electrode sheet 120 and the second negative electrode sheet 220 are all coated with active material layers on both sides.

[0085] It should be noted that the reason why the present application chooses to replace the positive electrode plate in the second battery cell unit with a protective film is that when the positive electrode plate of the second battery cell unit is replaced, the first negative electrode plates of the first battery cell unit are on both sides. Due to the interface effect, no reaction will occur between the two adjacent first negative electrode plates, and lithium ions can still be exchanged with the positive electrode plates of the remaining first battery cell units to contribute capacity. However, if the second negative electrode plate is replaced, the lithium ions on the positive electrode plate facing the second negative electrode plate will be transferred to the second negative electrode plate and then deposited on the protective film, which is prone to lithium precipitation problems, causing the battery performance to decline, the cycle life to be greatly shortened, and the fast charging capacity of the battery will be limited, and it may also cause consequences such as battery combustion or explosion.

[0086] The present application obtains a secondary battery by combining two battery cell units, and the positive electrode plate in the second battery cell unit is replaced with a protective film 210. The protective film 210 provides protection for the secondary battery, which can effectively improve the ability of the secondary battery to resist the impact of heavy objects, play a role in shock absorption and pressure prevention, and effectively alleviate the instantaneous short circuit caused by the rupture of the barrier film, avoiding short-term fire or even explosion.

[0087] As an embodiment, a barrier film is disposed between the second negative electrode active material layer and the protective film.

[0088] The present application does not specifically limit the barrier membrane. Without violating the inventive concept of the present application, any known type of barrier membrane can be used in the present application, such as a membrane suitable for liquid batteries and a solid electrolyte membrane in a solid-state battery.

[0089] The present application has no particular restriction on the type of barrier membrane. When a liquid battery system is used, the barrier membrane may be one or more of polyolefin microporous membrane, polypropylene, polyethylene felt, glass fiber felt or ultrafine glass fiber paper.

[0090] When the battery is a liquid battery, the electrolyte at least includes a non-aqueous liquid electrolyte solution. As an embodiment, the electrolyte is composed only of a non-aqueous electrolyte solution, and the non-aqueous electrolyte solution includes an organic solvent and a lithium salt dissolved in the organic solvent. The present application does not particularly limit the types of lithium salts and solvents for dissolving lithium salts. Without violating the inventive concept of the present application, any known lithium salts and solvents can be used in the present application. As an illustrative example, the lithium salts that can be used include: lithium hexafluorophosphate (LiPF6); lithium perchlorate (LiClO4), lithium tetrachloroaluminate (LiAlCl4), lithium iodide (LiI), lithium bromide (LiBr), lithium thiocyanate (LiSCN), lithium tetrafluoroborate (LiBF4), lithium difluorooxalatoborate (LiBF2(C2O4))(LiODFB), lithium tetraphenylborate (LiB(C6H5)4), bis(oxalate) Lithium borate (LiB(C2O4)2) (LiBOB), lithium tetrafluorooxalophosphate (LiPF4(C2O4)) (LiFOP), lithium nitrate (LiNO3), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(trifluoromethanesulfonyl imide) (LITFSI) (LiN(CF3SO2)2), lithium bis(fluorosulfonyl imide) (LiN(FSO2)2) (LIFSI) and combinations thereof. In certain variations, the lithium salt is selected from lithium hexafluorophosphate (LiPF6), lithium bis(trifluoromethanesulfonyl imide) (LiTFSI) (LiN(CF3SO2)2), lithium bis(fluorosulfonyl imide) (LiN(FSO2)2) (LiFSI), lithium fluoroalkyl phosphonate (LiFAP), lithium phosphate (Li3PO4) and combinations thereof. Solvents that can be used include, but are not limited to, various alkyl carbonates, such as cyclic carbonates (e.g., ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), fluoroethylene carbonate (FEC)), linear carbonates (e.g., dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC)), aliphatic carboxylates (e.g., methyl formate, methyl acetate, methyl propionate), γ-lactones (e.g., γ-butyrolactone, γ-valerolactone), chain structure ethers (e.g., 1,2-dimethoxyethane (DME), 1-2-diethoxyethane, ethoxymethoxyethane), cyclic ethers (e.g., tetrahydrofuran, 2-methyltetrahydrofuran), 1,3-dioxolane (DOL), sulfur compounds (e.g., sulfolane), and combinations thereof. In a complete non-aqueous electrolyte system, the electrolyte may include the lithium salt in a concentration greater than or equal to 1 M to less than or equal to about 2 M. In certain embodiments, such as when the electrolyte has a lithium concentration greater than about 2 M or has an ionic liquid, the electrolyte may include one or more diluents, such as fluoroethylene carbonate (FEC) and / or hydrofluoroether (HFE).

[0091] Particularly preferably, the electrolyte is a solid electrolyte or a combination of a non-aqueous liquid electrolyte solution and a solid electrolyte.

[0092] When the battery is a solid-state battery or a solid-liquid hybrid battery and a solid electrolyte membrane is required, the solid electrolyte membrane may be one or a combination of oxide solid electrolyte membrane, sulfide solid electrolyte membrane, halide solid electrolyte membrane, polymer solid electrolyte membrane;

[0093] As an embodiment, the component based on the polymer solid electrolyte membrane may include one or more polymer materials selected from the group including the following: polyethylene glycol, polyethylene oxide (PEO), poly (p-phenylene oxide) (PPO), poly (methyl methacrylate) (PMMA), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polyvinylidene fluoride co-hexafluoropropylene (PVDF-HFP), polyvinyl chloride (PVC) and combinations thereof. In one variation, the one or more polymer materials may have an ionic conductivity equal to about 10-4 S / cm.

[0094] As an embodiment, the oxide solid electrolyte membrane is composed of oxide solid electrolyte particles, which may include one or more garnet ceramics, LISICON type oxides, NASICON type oxides and perovskite type ceramics. For example, the one or more garnet ceramics may be selected from the group consisting of: Li 6.5 LqCy 1.75 Te 0.25 O 12 、Li7La3Zr2O 12 , Li 6.2 Ga 0.3 La 2.95 R 0.05 Zr2O 12 , Li 6.85 La 2.9 Ca 0.1 Zr 1.75 Nb 0.25 O 12 , Li 6.25 Al 0.25 La3Zr2O 12 , Li 6.75 LqCy 1.75 Nb 0.25 O 12 , Li 6.75 LqCy 1.75 Nb 0.25 O 12 And combinations thereof. One or more LISICON-type oxides may be selected from the group consisting of: Li 14Zn(GeO4)4, Li 3+x (P1-xSix)O4 (where 0 < x < 1), Li3+xGexV 1-x O4 (where 0 < x < 1) and combinations thereof. One or more NASICON-type oxides can be defined by LiMM′(PO4)3, where M and M′ are independently selected from Al, Ge, Ti, Sn, Hf, Zr, and La. For example, in certain variations, one or more NASICON-type oxides can be selected from the group consisting of the following: Li1+xAl x Ge 2-x (PO4)3 (LAGP) (where 0 ≤ x ≤ 2), Li1+xAl x Ti 2-x (PO4)3 (LATP) (where 0 ≤ x ≤ 2), Li1+xY x Zr 2-x (PO4)3 (LYZP) (where 0 ≤ x ≤ 2), Li 1.3 Al 0.3 Ti 1.7 (PO4)3, LiTi2(PO4)3, LiGeTi(PO4)3, LiGe2(PO4)3, LiHf2(PO4)3, and combinations thereof. One or more perovskite-type ceramics can be selected from the group consisting of the following: Li 3.3 La 0.53 TiO3, LiSr 1.65 Zr 1.3 Ta 1.7 O9, Li 2x-y Sr 1-x TayZr 1-y O3 (where x = 0.75y and 0.60 < y < 0.75), Li 3 / 8 Sr 7 / 16 Nb 3 / 4Zr 1 / 4 O3, Li 3x La (2 / 3-x) TiO3 (where 0 < x < 0.25) and combinations thereof. In one variation, one or more oxide-based materials can have an ionic conductivity greater than or equal to about 10-5 S / cm to less than or equal to about 10-1 S / cm.

[0095] As an implementation, the sulfide solid electrolyte membrane is composed of sulfide solid electrolyte particles and can include one or more sulfide-based materials selected from the group consisting of the following: Li2S-P2S5, Li2S-P2S5-MS x (where M is Si, Ge, and Sn and 0 ≤ x ≤ 2), Li 3.4 Si 0.4P 0.6 S4, Li 10 GeP2S 11.7 O 0.3 , Li 9.6 P3S 12 、Li7P3S 11 、Li9P3S9O3、Li 10.35 Si 1.35 P 1.65 S 12 , Li 9.81 Sn 0.81 P 2.19 S 12 , Li 10 (Si 0.5 Ge 0.5 )P2S 12 、Li(Ge 0.5 Sn 0.5 )P2S 12 、Li(Si 0.5 Sn 0.5 )PsS 12 , Li 10 GeP2S 12 (LGPS), Li6PS5X (where X is Cl, Br or I), Li7P2S8I, Li 10.35 Ge 1.35 P 1.65 S 12 , Li 3.25 Ge 0.25 P 0.75 S4, Li 10 SnP2S 12 , Li 10 SiP2S 12 , Li 9.54 Si 1.74 P 1.44 S 11.7 C l0.3 、(1-x)P2S 5-x Li2S (wherein 0.5≤x≤0.7) and combinations thereof. In one variation, the one or more sulfide-based materials may have an ionic conductivity of greater than or equal to about 10-7 S / cm to less than or equal to about 1 S / cm.

[0096] As an embodiment, the halide solid electrolyte membrane may be composed of halide solid electrolyte particles, including Li2CdC l4 、Li2MgC l4 , Li2CdI4, Li2ZnI4, Li3OCl, LiI, Li5ZnI4, Li3OCl 1-x Brx (where 0 < x < 1) and combinations thereof. In one variant, one or more halide-based materials may have an ionic conductivity greater than or equal to about 10−8 S / cm to less than or equal to about 10−1 S / cm.

[0097] As one embodiment, the borate solid electrolyte membrane is composed of borate solid electrolyte particles, including one or more borate-based materials of the group consisting of: Li2B4O7, Li2O-(B2O3)-(P2O5), and combinations thereof. In one variant, one or more borate-based materials may have an ionic conductivity greater than or equal to about 10−7 S / cm to less than or equal to about 10−2 S / cm.

[0098] As one embodiment, the nitride solid electrolyte membrane is composed of nitride solid electrolyte particles, including Li3N, Li7PN4, LiSi2N3, LiPON, and combinations thereof. In one variant, one or more nitride-based materials may have an ionic conductivity greater than or equal to about 10−9 S / cm to less than or equal to about 1 S / cm.

[0099] As one embodiment, the hydride solid electrolyte membrane is composed of hydride solid electrolyte particles, and the hydride-based particles may include one or more hydride-based materials selected from the group consisting of: Li3AlH6, LiBH4, LiBH4-Li X (where X is one of Cl, Br, and I), LiNH2, Li2NH, LiBH4-LiNH2, and combinations thereof. In one variant, one or more hydride-based materials may have an ionic conductivity greater than or equal to about 10−7 S / cm to less than or equal to about 10−2 S / cm.

[0100] In yet another variant, the solid electrolyte particles may be quasi-solid electrolytes, which comprise a mixture of the non-aqueous liquid electrolyte solution and the solid electrolyte system detailed above, for example, including one or more ionic liquids and one or more metal oxide particles (such as alumina (Al2O3) and / or silica (SiO2)).

[0101] This application has no particular requirements for the composition and structure of the positive electrode and the negative electrode. On the basis of not violating the inventive concept of this application, any known positive electrode active material, negative electrode active material, current collector, and corresponding auxiliary structures and compositions can be used in this application.

[0102] Merely as a schematic example, rather than imposing any limitation on the scope of protection, the positive electrode and negative electrode materials and structures are briefly described below.

[0103] The negative electrode is formed of a lithium-based material that can be used as a negative electrode of a lithium-ion battery. For example, the negative electrode may include a negative electrode active material that can be used as a negative electrode of a battery. The negative electrode active material layer may be composed of a variety of negative electrode active materials. In certain embodiments, the negative electrode may also include an electrolyte, such as the oxide, sulfide, halide electrolyte particles (not shown) indicated above.

[0104] The present application does not particularly limit the type of negative electrode active material. Without violating the inventive concept of the present application, any known negative electrode active material can be used in the present application; in one embodiment, the negative electrode active material comprises lithium metal and / or lithium alloy. In other embodiments, the negative electrode is a silicon-based negative electrode active material, which comprises silicon, such as silicon alloys, silicon oxides, or combinations thereof, which may also be mixed with graphite in some cases. In other embodiments, the negative electrode may include a carbonaceous-based negative electrode active material, which comprises one or more of graphite, graphene, carbon nanotubes (CNTs), and combinations thereof. In yet another embodiment, the negative electrode includes one or more negative electrode active materials that accept lithium, such as lithium titanium oxide (Li4Ti5O 12 ), one or more transition metals (e.g., tin (Sn)), one or more metal oxides (e.g., vanadium oxide (V2O5), tin oxide (SnO), titanium dioxide (TiO2)), titanium niobium oxide (Ti x Nb y O z , where 0≤x≤2, 0≤y≤24 and 0≤z≤64), a metal alloy such as copper tin alloy (Cu6Sn5) and one or more metal sulfides such as iron sulfide (FeS).

[0105] Alternatively, the negative electrode active material in the negative electrode may be doped with one or more conductive agents providing an electronic conduction path and / or at least one polymer binder material that improves the structural integrity of the negative electrode. For example, alternatively, the binder may be: poly (tetrafluoroethylene) (PTFE), sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), nitrile rubber (NBR), styrene ethylene butylene styrene copolymer (SEBS), styrene butadiene styrene copolymer (SBS), lithium polyacrylate (LiPAA), sodium polyacrylate (NaPAA), sodium alginate, lithium alginate and combinations thereof. The conductive agent may include carbon-based materials, powdered nickel or other metal particles or conductive polymers. Carbon-based materials may include particles such as carbon black, graphite, superP, acetylene black (such as, KETCHENTM black or DENKATM black), carbon fibers and nanotubes, graphene, and the like. Examples of conductive polymers include polyaniline, polythiophene, polyacetylene, polypyrrole, poly (3,4-ethylenedioxythiophene) polystyrene sulfonate, and the like.

[0106] The negative electrode may include greater than or equal to about 50wt% to less than or equal to about 97wt% of a negative electrode active material, optionally greater than or equal to about 0wt% to less than or equal to about 60wt% of a solid electrolyte, optionally greater than or equal to about 0wt% to less than or equal to about 15wt% of a conductive material, and optionally greater than or equal to about 0wt% to less than or equal to about 10wt% of a binder.

[0107] The positive electrode is formed of a plurality of positive active particles comprising one or more transition metal cations, such as manganese (Mn), nickel (Ni), cobalt (Co), chromium (Cr), iron (Fe), vanadium (V) and combinations thereof. In some embodiments, the positive electrode electroactive material layer further comprises an electrolyte, such as a plurality of electrolyte particles. The positive electrode active material layer has a thickness of greater than or equal to about 1 μm to less than or equal to about 1,000 μm.

[0108] The positive electrode electroactive material layer is one of a layered oxide cathode, a spinel cathode and a polyanion cathode. For example, the layered oxide cathode (e.g., a rock salt layered oxide) comprises one or more lithium-based positive electrode active materials selected from the following: LiCoO2 (LCO), LiNi x Mn y Co 1-x-y O2 (where 0≤x ≤1 and 0≤y≤1), LiNi 1-x-y Co x Al y O2 (where 0≤x≤1 and 0≤y≤1), LiNi x Mn 1-x O2 (where 0≤x≤1), and Li 1+x MO2 (wherein M is one of Mn, Ni, Co and Al and 0≤x≤1). The spinel cathode comprises one or more lithium-based positive active materials selected from the group consisting of LiMn2O4 (LMO) and LiNi x Mn 1.5 O4. The olivine-type cathode comprises one or more lithium-based positive electrode electroactive materials LiMPO4 (wherein M is at least one of Fe, Ni, Co and Mn). The polyanion cation comprises, for example, a phosphate such as LiV2(PO4)3 and / or a silicate such as LiFeSiO4.

[0109] In one embodiment, one or more lithium-based positive electrode electroactive materials may optionally be coated (e.g., by LiNbO3 and / or Al2O3) and / or may be doped (e.g., by magnesium (Mg)). In addition, in certain embodiments, one or more lithium-based positive electrode active materials may optionally be mixed with one or more conductive materials that provide an electron conduction path and / or at least one polymer binder material that improves the structural integrity of the positive electrode. For example, the positive electrode active material layer may include greater than or equal to about 30 wt% to less than or equal to about 98 wt% of one or more lithium-based positive electrode active materials; greater than or equal to about 0 wt% to less than or equal to about 30 wt% of a conductive agent; and greater than or equal to about 0 wt% to less than or equal to about 20 wt% of a binder, and in some aspects, optionally greater than or equal to about 1 wt% to less than or equal to about 20 wt% of a binder.

[0110] The positive electrode active material layer may be optionally mixed with a binder such as polytetrafluoroethylene (PTFE), sodium carboxymethylcellulose (CMC), styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), nitrile rubber (NBR), styrene-ethylene-butylene-styrene copolymer (SEBS), styrene-butadiene-styrene copolymer (SBS), lithium polyacrylate (LiPAA), sodium polyacrylate (NaPAA), sodium alginate, lithium alginate and combinations thereof. The conductive agent may include carbon-based materials, powdered nickel or other metal particles, or conductive polymers. Carbon-based materials may include particles such as carbon black, graphite, acetylene black (such as KETCHENTM black or DENKATM black), carbon fibers and nanotubes, graphene, and the like. Examples of conductive polymers include polyaniline, polythiophene, polyacetylene, polypyrrole, and the like.

[0111] The positive electrode current collector can facilitate the flow of electrons between the positive electrode and the external circuit. The positive electrode current collector may include a metal, such as a metal foil, a metal grid or screen, or a metal mesh. For example, the positive electrode current collector may be formed of aluminum, stainless steel and / or nickel or any other suitable conductive agent known to those skilled in the art.

[0112] The present application is further described below with reference to embodiments and comparative examples.

[0113] Example 1

[0114] A secondary battery is obtained by stacking 40 first battery cell units and 2 second battery cell units, and a second battery cell unit is placed between the 13th and 14th first battery cell units and between the 27th and 28th first battery cell units, respectively.

[0115] The first battery cell unit includes a positive electrode plate, a first negative electrode plate and a barrier film, and the second battery cell unit includes a protective film, a second negative electrode plate and a barrier film. The positive electrode active materials are all NCM523, the negative electrode active materials are all graphite, and the barrier film is a polypropylene separator.

[0116] The protective film comprises a polymer film and a flame retardant, wherein the polymer film is made of polypropylene, and the flame retardant is melamine polyphosphate, and the polymer film and the flame retardant react to form the protective film. The thickness of the protective film is 300 μm.

[0117] Example 2

[0118] The difference between this embodiment and embodiment 1 is that the polypropylene polymer film is coated with a ceramic coating, the ceramic coating is a SiO2 coating containing a flame retardant, and the flame retardant is melamine polyphosphate. The remaining technical features are the same as those of embodiment 1.

[0119] Example 3

[0120] The difference between this embodiment and embodiment 1 is that the polymer film is composed of polyethylene terephthalate and a flame retardant formed in the pores thereof, and the remaining technical features are the same as those of embodiment 1.

[0121] Example 4

[0122] The difference between this embodiment and Embodiment 1 is that the second battery cell unit is respectively located between the 5th and 6th first battery cell units, between the 15th and 16th first battery cell units, and between the 29th and 30th first battery cell units, and the remaining technical features are the same as those in Embodiment 1.

[0123] Example 5

[0124] The difference between this embodiment and Embodiment 1 is that the number of the second battery cell units is 4, which are respectively located between the 8th and 9th first battery cell units, between the 16th and 17th first battery cell units, between the 24th and 25th first battery cell units, and between the 32nd and 33rd first battery cell units. The remaining technical features are the same as those in Embodiment 1.

[0125] Example 6

[0126] Compared with Example 1, the second battery cell unit includes a second negative electrode plate, a barrier film and a second positive electrode current collector, and a protective film and a second positive electrode active material layer are respectively arranged on both sides of the second positive electrode current collector.

[0127] Comparative Example 1

[0128] The difference from Example 1 is that only the first battery cell units are stacked to obtain the secondary battery.

[0129] Comparative Example 2

[0130] The difference from Example 1 is that the second battery cell unit between the 27th and 28th first battery cell units is removed.

[0131] The impact resistance and battery capacity of the secondary batteries in the above embodiments and comparative examples were tested.

[0132] The test method for impact resistance is: after the secondary battery is fully charged, it is placed on the platform surface, and a metal rod with a radius of 8mm and a mass of 10kg is dropped vertically from a height of 610mm just above the center of the secondary battery to act on the surface of the secondary battery. The secondary battery is observed for 6 hours to see if it catches fire or explodes.

[0133] The battery capacity test method is: charge at 0.5C at room temperature. When the terminal voltage of the secondary battery reaches the charging limit voltage, leave the secondary battery for 10 minutes and then discharge at 0.5C until the termination voltage.

[0134] The test results are shown in Table 1 below.

[0135] Table 1

[0136]

[0137]

[0138] As can be seen from Table 1, the secondary batteries of Examples 1-5 did not catch fire or explode after being hit by a heavy object, while all the secondary batteries of Comparative Example 1 caught fire and exploded after being hit by a heavy object. It can be seen that the present application can improve the ability of the secondary battery to resist the impact of heavy objects to a certain extent by replacing the positive electrode plates of some of the battery cells constituting the secondary battery with protective films, but the battery capacity of the secondary battery will be lost accordingly. However, according to the test, in the solution provided by the present application, the battery capacity loss is not large. In Comparative Example 2, the number of stacked first battery cells is greater than 20, and the improvement of the ability of the secondary battery to resist the impact of heavy objects is poor, and the secondary battery will still burn. It can be seen that it is also particularly important to control the proportional relationship between the first battery cell and the second battery cell.

[0139] The technical solution provided by the present invention is described in detail above. The structure and implementation methods of the present invention are described in detail using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A secondary battery, characterized in that: include: m first battery cell units and n second battery cell units, each of the first battery cell units includes a first positive electrode current collector, a first positive electrode active material layer arranged on the first positive electrode current collector, a first negative electrode active material layer and a barrier film arranged between the first positive electrode active material layer and the first negative electrode active material layer, each of the second battery cell units includes a protective film and a second negative electrode active material layer, the protective film and the second negative electrode active material layer are arranged oppositely, n≥1, m>n; wherein, The first battery cell unit comprises a first negative electrode active material layer, a barrier film, a first positive electrode active material layer, and a first positive electrode current collector which are stacked in sequence; The second battery cell unit comprises a second negative electrode active material layer, a barrier film, a protective film, a barrier film, a second negative electrode active material layer, and a negative electrode current collector which are stacked in sequence; or, The second battery cell unit comprises a second negative electrode active material layer, a barrier film, a second positive electrode active material layer, a second positive electrode current collector, a protective film, a barrier film, a second negative electrode active material layer and a negative electrode current collector which are stacked in sequence; The second battery cell unit is arranged between any two of the first battery cell units or is located at the outermost side of the secondary battery; The protective film comprises a polymer matrix material; The protective film further comprises a flame retardant; the flame retardant comprises an additive flame retardant and a reactive flame retardant.

2. The secondary battery according to claim 1, characterized in that: The polymer matrix material in the protective film includes at least one of polyolefin, polyamide, epoxy resin, polystyrene, polyurethane, polyvinyl chloride, polycarbonate, polyvinyl alcohol, polymethyl methacrylate, polyethylene terephthalate, poly(p-phenylene benzobisazole), and polyimide.

3. The secondary battery according to claim 1, characterized in that: The protective film comprises a polymer film formed by the polymer matrix material and a flame retardant layer arranged on the surface of the polymer film.

4. The secondary battery according to claim 1, characterized in that: The thickness of the protective film is 10-5000 μm.

5. The secondary battery according to claim 1, characterized in that: The thickness of the protective film is 100-500 μm.

6. The secondary battery according to claim 1, characterized in that: The protective film and the first positive electrode active material layer are arranged on both sides of the same current collector, and the protective film covers the current collector.

7. The secondary battery according to claim 1, characterized in that: The second battery cell unit includes two second negative electrode active material layers that are arranged opposite to each other, and the protective film is located between the two second negative electrode active material layers.

8. The secondary battery according to claim 3, characterized in that: The protective film is formed by a polymer film stack formed by two or more polymer matrix materials.

9. The secondary battery according to claim 3, characterized in that: In the protective film, each polymer film is made of the same material.

10. The secondary battery according to claim 3, characterized in that: In at least one of the protective films, at least two polymer films are made of different materials.

11. The secondary battery according to claim 1, characterized in that: In the secondary battery, the structure of the protective film of each of the second battery cells is completely the same; or, In the secondary battery, at least two protective films in each of the second battery core units have different structures.

12. The secondary battery according to claim 1, characterized in that: Two or more of the second battery core units are arranged between any two first battery core units or are located at the outermost side of the secondary battery.

13. The secondary battery according to claim 1, characterized in that: The second battery cell unit is disposed between two groups of first battery cell unit stacks consisting of a plurality of first battery cell units, and the difference in the number of first battery cell units in the two groups of first battery cell unit stacks is m1, wherein m1≤1.

14. The secondary battery according to claim 1, characterized in that: The number of the first battery cell units in the first battery cell unit stack is m2, and 10≤m2≤15.

15. The secondary battery according to claim 14, characterized in that: 12≤m2≤14。 16. The secondary battery according to claim 14, characterized in that: The numbers of the first battery cell units in the first battery cell unit stacks on both sides of the second battery cell units are different.

17. The secondary battery according to claim 14, characterized in that: The first battery cell unit stacks on both sides of the second battery cell unit include m3 first battery cell units, where 1≤m3≤20.

18. The secondary battery according to claim 17, characterized in that: 1≤m3≤15。

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