Secondary battery and electrical apparatus

Abstract

The present application relates to a secondary battery and an electrical apparatus. The secondary battery comprises a positive electrode sheet and a positive tab connected thereto; the positive tab comprises a first current collector and an anti-overcharge layer, the anti-overcharge layer being arranged on the surface of the first current collector, and the anti-overcharge layer comprising an anti-overcharge additive. The cycle performance of the secondary battery can be improved while overcharge prevention is taken into account.

Description

Secondary batteries and electrical devices

[0001] Related applications

[0002] This application claims priority to the Chinese patent application filed with the China Patent Office on July 26, 2023, with application number 2023109218896 and entitled “Secondary Battery and Electrical Device,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present application belongs to the technical field of secondary batteries, and specifically relates to a secondary battery and an electrical device. Background Art

[0004] The statements herein merely provide background information related to the present application and do not necessarily constitute prior art.

[0005] Secondary batteries are widely used in various consumer electronics and electric vehicles due to their outstanding features such as light weight, pollution-free operation, and no memory effect. However, overcharging during battery use can affect the battery's cycle performance, so the problem of overcharging remains an urgent issue that needs to be addressed.

[0006] Summary of the Invention

[0007] Based on this, it is necessary to provide a secondary battery and an electrical device that can improve cycle performance while taking into account overcharge prevention.

[0008] In a first aspect of the present application, a secondary battery is provided, comprising a positive electrode sheet and a positive electrode tab connected to the positive electrode sheet, wherein the positive electrode tab comprises a first current collector and an anti-overcharge layer, wherein the anti-overcharge layer is arranged on the surface of the first current collector, and the anti-overcharge layer comprises an anti-overcharge additive.

[0009] Without wishing to be limited to any theory, the present application aims to improve the positive electrode tab connected to the positive electrode plate in a secondary battery. Specifically, an anti-overcharge layer with an anti-overcharge additive is provided on the positive electrode tab, so that when the secondary battery is overcharged, the potential increase of the positive electrode plate can induce the anti-overcharge additive in the positive electrode tab connected thereto to react slowly, thereby playing a role in preventing overcharge; at the same time, the anti-overcharge additive is not added to the positive active layer of the positive electrode plate, and basically does not affect the performance of the positive active layer. Compared with setting the anti-overcharge additive in the positive active layer, the cycle performance of the secondary battery during long-term use is greatly improved, and the risk of overcharge outage can also be reduced.

[0010] In any embodiment of the present application, the anti-overcharge additive includes at least one of Li2C2O4, Li2C4O4, Li2C3O5, Li2C4O6, Li2C6O6, Li2CO3, LiN3, LiODFB, Li2O, Li3N, LiF, LiCl, Li2S, LiBH4, CH3COOLi, LiNO3 and Li2SO4.

[0011] In any embodiment of the present application, in the anti-overcharge additive, the mass content of Li2C2O4 is 50% to 95%.

[0012] In any embodiment of the present application, the mass content of the anti-overcharging additive is 0.5% to 50% based on the total mass of the anti-overcharging layer.

[0013] In any embodiment of the present application, the binder includes at least one of polypropylene, polyacrylic acid, polystyrene, polyterephthalic acid, styrene-butadiene rubber, water-based acrylic resin, polytetrafluoroethylene, ethylene-vinyl acetate copolymer, carboxymethyl cellulose, polyvinyl alcohol, polyvinyl butyral and polyvinylidene fluoride.

[0014] In any embodiment of the present application, the positive electrode plate includes a second current collector and a positive electrode active layer provided on the second current collector;

[0015] The area ratio of the anti-overcharge layer to the positive electrode active layer is (1-10):100.

[0016] In any embodiment of the present application, the anti-overcharge additive can decompose and generate gas at a voltage of ≥4.2V.

[0017] In any embodiment of the present application, the anti-overcharging layer further comprises insulating particles;

[0018] The mass content of the insulating particles is 1% to 30% based on the total mass of the anti-overcharging layer.

[0019] In any embodiment of the present application, the thickness of the anti-overcharging layer is 10 μm to 150 μm.

[0020] In any embodiment of the present application, the positive electrode tab further includes a first tab adhesive layer, and the first tab adhesive layer is provided on a surface of the anti-overcharge layer away from the first current collector.

[0021] In any embodiment of the present application, the anti-overcharging layer further includes a conductive agent with a mass content of 0 to 5%.

[0022] In any embodiment of the present application, the thickness of the first tab glue layer is 5 μm to 100 μm.

[0023] In any embodiment of the present application, the positive electrode plate includes a second current collector and a positive electrode active layer provided on the second current collector, the second current collector and the first current collector are interconnected to form a whole, the surface of the first current collector also includes a blank area adjacent to the anti-overcharging layer, and the anti-overcharging layer is located between the blank area and the second current collector.

[0024] In any embodiment of the present application, the positive electrode tab further includes a second tab glue layer adjacent to and arranged in the same layer as the anti-overcharge layer.

[0025] In any embodiment of the present application, the thickness of the second tab glue layer is 30 μm to 150 μm.

[0026] In a second aspect of the present application, an electrical device is provided, wherein the electrical device includes the secondary battery provided in the first aspect of the present application.

[0027] The details of one or more embodiments of the present application are set forth in the following drawings and description. Other features, objects, and advantages of the present application will become apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the conventional technology, the following briefly introduces the drawings required for use in the embodiments or the conventional technology descriptions. Obviously, the drawings described below are merely embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the disclosed drawings without any creative work.

[0029] FIG1 is a schematic top view of a positive electrode sheet and a positive electrode tab of a secondary battery according to one embodiment of the present application;

[0030] FIG2 is a schematic cross-sectional view of the positive electrode tab shown in FIG1 ;

[0031] 3 is a schematic cross-sectional view of a positive electrode tab of a secondary battery according to another embodiment of the present application;

[0032] 4 is a schematic top view of a positive electrode tab of a secondary battery according to another embodiment of the present application;

[0033] 5 is a schematic top view of a positive electrode sheet and a positive electrode tab of a secondary battery according to another embodiment of the present application;

[0034] FIG6 is a schematic diagram of a battery cell according to an embodiment of the present application;

[0035] FIG7 is an exploded view of the battery cell according to an embodiment of the present application shown in FIG6 ;

[0036] FIG8 is a schematic diagram of a battery module according to an embodiment of the present application;

[0037] FIG9 is a schematic diagram of a battery pack according to an embodiment of the present application;

[0038] FIG10 is an exploded view of the battery pack according to one embodiment of the present application shown in FIG9 ;

[0039] 11 is a schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of the present application;

[0040] Explanation of the accompanying reference numerals: 1. Battery cell; 11. Shell; 12. Electrode assembly; 13. Cover plate; 121. Positive electrode tab; 1211. First current collector; 1212. Anti-overcharge layer; 1213. First tab adhesive layer; 1214. Second tab adhesive layer; 122. Positive electrode sheet; 2. Battery pack; 21. Upper case; 22. Lower case; 3. Battery module; 4. Electrical device. DETAILED DESCRIPTION

[0041] The following detailed description of the embodiments of the present application is appropriately referred to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially identical structures may be omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0042] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is merely an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0043] Unless otherwise specified, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution. Unless otherwise specified, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, it is mentioned that the method may also include step (c), indicating that step (c) can be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0044] In this application, open technical features or technical solutions described with words such as "contain," "include," and "includes" do not exclude additional members beyond the listed members unless otherwise specified, and can be regarded as providing both closed features or solutions consisting of the listed members and open features or solutions that include additional members beyond the listed members. For example, if A includes a1, a2, and a3, it may or may not include other members unless otherwise specified. This can be regarded as providing both the feature or solution of "A consists of a1, a2, and a3" and the feature or solution of "A includes not only a1, a2, and a3, but also other members."

[0045] Unless otherwise specified, the terms used in this application have the commonly understood meanings commonly understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of the various parameters mentioned in this application can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the examples of this application).

[0046] secondary batteries

[0047] A secondary battery is a battery that can be recharged to activate the active materials after discharge and continue to be used.

[0048] Typically, a secondary battery consists of a positive electrode, a negative electrode, and an electrolyte. During the battery's charge and discharge processes, active ions are embedded in and extracted from the positive and negative electrodes. It's understood that these active ions originate from the positive electrode active material in the positive electrode.

[0049] In order to facilitate the connection between the secondary battery and the external circuit, it generally also includes an electrode tab. The electrode tab connected to the positive electrode sheet is the positive electrode tab, and the electrode tab connected to the negative electrode sheet is the negative electrode tab.

[0050] The positive electrode tab includes a first current collector and an anti-overcharge layer. The anti-overcharge layer is arranged on the surface of the first current collector and includes a binder and an anti-overcharge additive.

[0051] Referring to Figures 1 and 2 , the connection between the positive electrode tab 121 and the positive electrode sheet 122 is shown. The positive electrode tab 121 includes a first current collector 1211 and an anti-overcharge layer 1212. The anti-overcharge layer 1212 is disposed on the surface of the first current collector 1211 and includes an anti-overcharge additive. Referring to Figure 1 , the area where the anti-overcharge layer 1212 is located is designated as the anti-overcharge protection zone A.

[0052] Without wishing to be limited to any theory, the present application aims to improve the positive electrode tab connected to the positive electrode plate in a secondary battery. Specifically, an anti-overcharge layer with an anti-overcharge additive is provided on the positive electrode tab, so that when the secondary battery is overcharged, the potential increase of the positive electrode plate can induce the anti-overcharge additive in the positive electrode tab connected thereto to react slowly, thereby playing a role in preventing overcharge; at the same time, the anti-overcharge additive is not added to the positive active layer of the positive electrode plate, and basically does not affect the performance of the positive active layer. Compared with setting the anti-overcharge additive in the positive active layer, the cycle performance of the secondary battery during long-term use is greatly improved, and the risk of overcharge outage can also be reduced.

[0053] In some embodiments, the anti-overcharge additive can decompose and produce gas at a voltage of 4.2 V or higher. Thus, when the secondary battery is overcharged, the anti-overcharge additive decomposes and releases gas at a voltage of 4.2 V or higher, thereby mitigating damage to the cathode. At the same time, the gas production can provide a timely response to overcharge. For example, gas production can cause an increase in the internal pressure of the secondary battery, enabling timely response to overcharge through internal pressure monitoring. Overcharge prevention interventions such as stopping charging can be implemented before the battery is damaged or exploded, thereby improving the safety of the secondary battery.

[0054] Furthermore, the gas generated by the overcharge prevention additive can be 4.25V to 6.0V. The operating voltage range of the overcharge prevention additive is wider, so the normal operating range of the applicable secondary voltage is also wider. For example, it can be applied to a low-voltage battery of 4.2V, providing timely protection in the event of overcharge, avoiding safety issues during low-voltage overcharging.

[0055] Furthermore, the gas generated by the overcharge prevention additive includes, but is not limited to, at least one of nitrogen and carbon dioxide. It is understood that due to the complexity of the gas generation mechanism, the gas types are only exemplified here. The actual gas types are not limited to these, as long as they can generate gas at the overcharge pressure.

[0056] In some embodiments, the overcharge prevention additive includes at least one of Li2C2O4, Li2C4O4, Li2C3O5, Li2C4O6, Li2C6O6, Li2CO3, LiN3, LiODFB, Li2O, Li3N, LiF, LiCl, Li2S, LiBH4, CH3COOLi, LiNO3 and Li2SO4.

[0057] Further, the overcharge prevention additive includes at least one of Li2C2O4, Li2C4O4, Li2C4O6, Li2C3O5 and LiN3.

[0058] In some examples, the anti-overcharge additive includes Li2C2O4 and Li2C4O6.

[0059] In some examples, the mass content of Li2C2O4 in the anti-overcharge additive is 50% to 95%, optionally 50% to 80%, for example, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%.

[0060] In some embodiments, the anti-overcharge layer further comprises a binder, which can effectively bind the anti-overcharge additive and the surface of the first current collector. In other examples, the anti-overcharge layer may not contain a binder.

[0061] In some embodiments, the mass content of the anti-overcharge additive is 0.5% to 50% based on the total mass of the anti-overcharge layer, optionally 2% to 20%, optionally 5% to 20%, and more optionally 5% to 15%. As an example, the mass content of the anti-overcharge additive in the anti-overcharge layer can be 0.5%, 2%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%. Within this range, the cycle performance and safety performance of the secondary battery can be better balanced.

[0062] In some embodiments, the binder in the anti-overfilling layer includes at least one of polypropylene, polyacrylic acid, polystyrene, polyterephthalic acid, styrene-butadiene rubber, water-based acrylic resin, polytetrafluoroethylene, ethylene-vinyl acetate copolymer, carboxymethyl cellulose, polyvinyl alcohol, polyvinyl butyral and polyvinylidene fluoride.

[0063] Furthermore, the binder in the anti-overfilling layer includes polypropylene.

[0064] In some embodiments, the anti-overcharging layer further comprises insulating particles. The insulating particles can serve as a particle reinforcement for the anti-overcharging layer, providing support and reinforcement, thereby increasing the structural strength of the anti-overcharging layer. Furthermore, the insulating particles can improve the heat resistance of the anti-overcharging layer.

[0065] The insulating particles include at least one of inorganic particles, organic particles, and organic-inorganic hybrid particles.

[0066] Furthermore, the inorganic particles include, but are not limited to, at least one of aluminum oxide, boehmite, zinc oxide, silicon dioxide, titanium dioxide, zirconium oxide, calcium carbonate, boron nitride, and manganese sulfide.

[0067] Furthermore, the mass content of the insulating particles is 1% to 30% based on the total mass of the anti-overcharging layer, and more preferably 5% to 20%. As an example, the mass content of the insulating particles can be 1%, 2%, 5%, 10%, 15%, 20%, 25%, or 30% based on the total mass of the anti-overcharging layer.

[0068] Furthermore, the insulating particles have a Dv50 particle size of 1 μm (micrometer) to 30 μm, and more preferably 5 μm to 15 μm. The volume average particle size Dv50 of the insulating particles is well known in the art and can be measured using methods known in the art. For example, it can be measured using a laser particle size analyzer (such as the Malvern Master Size 3000). The Dv50 particle size represents the particle size at which the cumulative volume distribution percentage of particles, starting from the smaller particle size, reaches 50% in the particle size distribution.

[0069] In some embodiments, the thickness of the anti-overcharging layer is 10 μm to 150 μm, and optionally 30 μm to 100 μm. As an example, the thickness of the anti-overcharging layer may be 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 80 μm, 90 μm, 100 μm, 120 μm, or 150 μm.

[0070] In some embodiments, the anti-overcharge layer can be prepared by mixing an anti-overcharge additive with a solvent and an optional binder to obtain an anti-overcharge slurry, coating the anti-overcharge slurry on the first current collector, and drying and solidifying the slurry. The optional binder refers to a binder that may or may not be added.

[0071] It is understood that the coating methods include but are not limited to spraying, brushing, spin coating, etc.

[0072] Furthermore, the solvent used in preparing the overcharge prevention layer may include at least one of water and an organic solvent. As an example, the organic solvent may be N-methylformamide (NMF).

[0073] In some embodiments, the positive electrode tab further includes a first tab adhesive layer. This first tab adhesive layer is disposed on the surface of the anti-overcharge layer, distal from the first current collector. This first tab adhesive layer provides insulation and protection for the underlying anti-overcharge layer. As shown in Figure 3 , the first current collector 1211 in the positive electrode tab 121 is sequentially provided with an anti-overcharge layer 1212 and a first tab adhesive layer 1213 within the anti-overcharge protection zone A.

[0074] It is understood that the first tab adhesive layer can be made of conventional tab adhesive. The first tab adhesive layer includes a binder. Furthermore, the binder in the second tab adhesive layer and the binder in the anti-overcharge layer can be selected from the same range, but the specific types in the specific examples can be the same or different.

[0075] In some embodiments, the anti-overcharging layer further comprises a conductive agent in an amount of 0-5% by weight. In other words, the conductive agent content in the anti-overcharging layer can be zero. When the first tab adhesive layer is also provided on the upper surface of the anti-overcharging layer, a conductive agent can be added to the anti-overcharging layer to enhance the rapid response of the anti-overcharging additive in the anti-overcharging layer during overcharging. Specifically, the conductive agent content in the anti-overcharging layer can be controlled to be greater than 0 and no greater than 5%.

[0076] As an example, the mass content of the conductive agent in the anti-overcharging layer is 0, 0.5%, 1%, 2%, 3%, 4%, or 5%. Alternatively, the mass content may be a range consisting of any two of the aforementioned values. Furthermore, based on the total mass of the anti-overcharging layer, the mass content of the conductive agent is greater than 0 and no greater than 3%, or is between 0.5% and 3%.

[0077] Furthermore, the thickness of the first tab adhesive layer is 5 μm to 100 μm. As an example, the thickness of the first tab adhesive layer may be 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, or 100 μm. Optionally, the thickness may be 30 μm to 100 μm.

[0078] In some embodiments, the positive electrode tab further includes a second tab adhesive layer adjacent to and arranged in the same layer as the anti-overcharging layer; the area in the positive electrode tab where the second tab adhesive layer is provided can be used as a packaging area. The packaging area where the second tab adhesive layer is located can serve as the packaging connection position of the positive electrode tab, play a sealing role, and is particularly suitable for soft-pack batteries. As shown in Figure 4, a top view of another positive electrode tab is shown, in which an anti-overcharging layer 1212 and a second tab adhesive layer 1214 are respectively formed in the areas adjacent to the surface of the first current collector 1211 (not shown), that is, an anti-overcharging protection area and a packaging area are formed. The anti-overcharging layer 1212 and the second tab adhesive layer 1214 are provided in the same layer on the first current collector 1211.

[0079] Furthermore, in addition to the binder, the first tab adhesive layer may also optionally contain insulating particles, and the selection of insulating particles may be the same as that of the insulating particles in the anti-overcharge layer, but the specific types in the specific examples may be the same or different. The second tab adhesive layer is similar to the first tab adhesive layer.

[0080] Furthermore, the first tab adhesive layer includes a binder and insulating particles. The insulating particles comprise 1% to 30% by weight of the first tab adhesive layer, and more preferably 5% to 20% by weight. For example, the insulating particles may comprise 1%, 2%, 5%, 10%, 15%, 20%, 25%, or 30% by weight of the total weight of the first tab adhesive layer. The second tab adhesive layer is similar to the first tab adhesive layer.

[0081] Furthermore, the second tab adhesive layer and the first tab adhesive layer do not contain conductive agents and overcharge prevention additives, so as to give the positive tab better insulation protection performance.

[0082] Furthermore, the thickness of the second tab adhesive layer is 30 μm to 150 μm, and can be optionally 30 μm to 100 μm. As an example, the thickness of the second tab adhesive layer can be 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, or 150 μm.

[0083] Positive electrode

[0084] In a secondary battery, the positive electrode sheet typically includes a second current collector and a positive electrode active layer disposed on the second current collector. The positive electrode active layer includes a positive electrode active material. It can be understood that the second current collector is the positive electrode current collector.

[0085] In some embodiments, the area ratio of the anti-overcharge layer in the positive electrode tab to the positive electrode active layer in the positive electrode sheet is (1-10):100. As an example, the area ratio may be 1:100, 2:100, 3:100, 4:100, 5:100, 6:100, 7:100, 8:100, 9:100, or 10:100. Furthermore, the area ratio may be (3-7):100. Controlling this area ratio can ensure that the anti-overcharge layer has a better anti-overcharge effect and the secondary battery has a better energy density.

[0086] Furthermore, the second current collector and the first current collector of the positive electrode tab are interconnected to form a whole. The surface of the first current collector of the positive electrode tab is provided with an anti-overcharge layer, and also includes a blank area adjacent to the anti-overcharge layer and not provided with a coating. The anti-overcharge protection zone where the anti-overcharge layer is located is located between the blank area and the second current collector. It can be understood that the blank area is not provided with a coating and can serve as an electrical connection end of the positive electrode tab. In the specific examples shown in Figures 1 and 5, the positive electrode tab 121 includes an anti-overcharge protection zone A and a blank area B provided adjacent to the anti-overcharge protection zone A.

[0087] Optionally, as shown in Figures 1 and 5 , in some examples, the second current collector and the first current collector are integrally formed. That is, the positive electrode tab and the positive electrode sheet are formed on the same current collector. Furthermore, on this basis, a first tab adhesive layer is formed on the overcharge prevention layer of the first current collector 1211 , which is particularly suitable for hard-pack batteries.

[0088] Specifically, as shown in FIG1 , the first current collector 1211 has one blank area B; further, the blank area B is as wide as the overcharge protection area A.

[0089] Specifically, as shown in Figure 5, in the positive electrode tab, the first current collector 1211 has multiple blank areas B, and the multiple blank areas B are located on the same side. That is, the multiple blank areas B of the first current collector 1211 are not continuous and can be used as connection sites independently.

[0090] In other examples, the positive electrode tab and the positive electrode sheet are separate structures, that is, the second current collector and the first current collector are separate. For example, the positive electrode tab as shown in FIG4 can be connected to the positive electrode sheet of the electrode assembly by means of a metal connecting piece or the like.

[0091] The second current collector can be a conventional metal foil or a composite current collector, wherein the composite current collector can be formed by placing a metal material on a polymer substrate. As an example, the second current collector can be an aluminum foil.

[0092] The specific type of the positive electrode active material can be any active material known in the art that can be used for the positive electrode of a secondary battery, and those skilled in the art can select it according to actual needs.

[0093] As an example, the positive electrode active material may include a sodium ion active material, and the sodium ion active material may adopt a positive electrode active material for a sodium ion battery known in the art. As an example, the sodium ion active material may include at least one of the following materials: Prussian blue (PBA) type, chemical formula (NaxMA[MB(CN)6]·zH2O, wherein MA and MB are transition metal ions, which are compounds composed of sodium, transition metal and cyanide, such as Na4Fe2(CN)6, Na4Fe(CN)6, Na 1.72MnFe2(CN)6, NaMnMn(CN)6, NaNiFe(CN)6, etc.; oxide type, with the chemical formula NaxMO2, where 0 < x ≤ 1 and M is a transition metal element, which is composed of transition metal oxides. The variable-valence transition metals involved mainly include vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), and copper (Cu). Among them, manganese and iron, which are relatively abundant in resources, are the most commonly used. For example, NaCrO2, NaMnO2, NaMnO2, Na 0.61 Ti 0.48 Mn 0.52 O2, Na[Fe 0.5 Co 0.5 O2, NaMnO2, Na[Ni 0.25 Fe 0.5 Mn 0.25 O2, etc.; and polyanion compound type, with the chemical formula Na x M y [[(XO m ) n- z , where M is a metal ion with variable valence states, X is an element such as P, S, and V, and it is composed of sodium, transition metals, and anions. The transition metals mainly include iron, vanadium, cobalt, etc., and the anions mainly include phosphate, pyrophosphate, fluorophosphate, and sulfate, such as NaMnFe2(PO4)6, Na2MnP2O7, Na3V2(PO4)3, Na2Fe2(SO4)3, NaFePO4, Na3V2(PO4)2F3, Na4Co3(PO4)2(P2O7).

[0094] As an example, the positive electrode active material may include a lithium ion active material, and the lithium ion active material includes, but is not limited to, one or more of lithium transition metal oxides, lithium-containing phosphates with olivine structure, and their respective modified compounds. Examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their modified compounds. Examples of lithium-containing phosphates with olivine structure may include, but are not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite material of lithium manganese iron phosphate and carbon, and their modified compounds. These materials can all be obtained through commercial channels.

[0095] In some embodiments, the modified compounds of the above materials may be doping modification and / or surface coating modification of the materials.

[0096] ​​​​It is understandable that the battery will be accompanied by the deintercalation and consumption of active ions such as lithium (Li) during the charge and discharge process, and the content of active ions such as Li in the positive electrode plate is different when the battery is discharged to different states. Taking lithium ion active materials as an example, in the list of positive electrode active materials in this application, unless otherwise specified, the content of Li is the initial state of the material. The positive electrode active material is applied to the positive electrode plate in the battery system, and after the charge and discharge cycle, the content of Li in the positive electrode active material contained in the plate will usually change. Among them, the content of Li can be measured by molar content, but is not limited to this. Regarding "the content of Li is the initial state of the material", the initial state of the material refers to the state before the material is added to the positive electrode slurry. It is understandable that the materials obtained by appropriate modification on the basis of the listed positive electrode active materials are also within the scope of positive electrode materials. The aforementioned appropriate modification refers to the acceptable modification method for the positive electrode active material, and non-limiting examples include coating modification.

[0097] In the examples of positive electrode active materials in this application, the oxygen (O) content is only a theoretical value. Lattice oxygen release will cause the molar content of oxygen to change, and the actual oxygen atomic content will fluctuate. The oxygen atomic content can be measured by molar content, but is not limited to this.

[0098] The positive electrode active layer may also optionally include a binder, a conductive agent, and other optional additives.

[0099] As an example, the conductive agent may be one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, Super P (SP), graphene, and carbon nanofibers.

[0100] As an example, the binder can be one or more of styrene-butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA) and polyvinyl butyral (PVB).

[0101] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the second current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0102] Negative electrode

[0103] The negative electrode plate generally includes a negative electrode current collector and a negative electrode film layer disposed on the negative electrode current collector. It is understood that in some examples, the negative electrode film layer may also be omitted.

[0104] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0105] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material on a polymer substrate. The metal material includes, but is not limited to, at least one of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys; the polymer substrate includes, but is not limited to, at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0106] Furthermore, the negative electrode film layer includes a negative electrode active material. It is understood that in some examples, the negative electrode film layer may not contain a negative electrode active material.

[0107] In some embodiments, the negative electrode active material may be a negative electrode active material for batteries known in the art. For example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxides, and tin alloys.

[0108] In some embodiments, the negative electrode film layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0109] In some embodiments, the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0110] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener. For example, the thickener may be sodium carboxymethyl cellulose (CMC-Na).

[0111] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent such as water to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0112] electrolytes

[0113] The electrolyte conducts ions between the positive and negative electrodes. For example, the electrolyte can be liquid, gel, or solid.

[0114] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0115] In some embodiments, the electrolyte salt includes at least one of a sodium salt, a lithium salt, and a potassium salt.

[0116] As an example, the sodium salt in the electrolyte salt can be selected from one or more of sodium perchlorate (NaClO4), sodium tetrafluoroborate (NaBF4), sodium hexafluorophosphate (NaPF6), sodium hexafluoroarsenate (NaAsF6), sodium trifluoroacetate (CF3COONa), sodium tetraphenylborate (NaB(C6H5)4), sodium trifluoromethanesulfonate (NaSO3CF3), sodium bis(fluorosulfonyl)imide (Na[(FSO2)2N]) or sodium bis(trifluoromethylsulfonyl)imide (Na[(CF3SO2)2N]).

[0117] As an example, the lithium salt in the electrolyte salt can be selected from one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobis(oxalatophosphate) (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).

[0118] In some embodiments, the solvent includes at least one of an ether solvent, an ester solvent, and a sulfone solvent.

[0119] As an example, the ether solvent may include at least one of ethylene glycol dimethyl ether (DME), diethylene glycol dimethyl ether (DEGDME), triethylene glycol dimethyl ether (TRGDME), tetraethylene glycol dimethyl ether (TEGDME), and 1,3-dioxolane (DOL);

[0120] As an example, the ester solvent may include at least one of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), fluoroethylene carbonate (FEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), γ-butyrolactone (BL), 1,3-propane sultone (1,3-PS), methyl propionate (MP), methyl butyrate (MB), ethyl acetate (EA), ethyl propionate (EP), propyl propionate (PP) and ethyl butyrate (EB).

[0121] As an example, the sulfone-based solvent includes dimethyl sulfoxide (DMSO).

[0122] In some embodiments, the electrolyte may further include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0123] Isolation film

[0124] In some embodiments, the secondary battery further includes a separator, which is disposed between the positive electrode sheet and the negative electrode sheet to serve as an isolation layer.

[0125] In some embodiments, the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride.

[0126] The isolation film can be a single-layer film or a multi-layer composite film. When the isolation film is a multi-layer composite film, the materials of each layer can be the same or different.

[0127] Unless otherwise specified, the above raw materials can be obtained commercially.

[0128] The shape of the secondary battery in the embodiment of the present application can be cylindrical, square or any other shape. As shown in FIG6 , a square-structured battery cell 1 is shown as an example.

[0129] In some embodiments, referring to Figure 7, the outer packaging may include a shell 11 and a cover plate 13. The shell 11 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 11 has an opening connected to the receiving cavity, and the cover plate 13 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 12 through a winding process or a lamination process. The electrode assembly 12 is encapsulated in the receiving cavity. The above-mentioned electrolyte is impregnated in the electrode assembly 12. The number of electrode assemblies 12 contained in the battery cell 1 can be one or more, and those skilled in the art can select according to specific actual needs.

[0130] The secondary battery may be a battery cell, a battery module, or a battery pack.

[0131] Figure 8 shows an example battery module 3. Referring to Figure 8 , within the battery module 3, multiple battery cells 1 may be arranged sequentially along the length of the battery module 3. Of course, they may also be arranged in any other manner. Furthermore, the multiple battery cells 1 may be secured together using fasteners.

[0132] Optionally, the battery module 3 may further include a housing having an accommodation space, and the plurality of battery cells 1 are accommodated in the accommodation space.

[0133] In some embodiments, the battery modules may be assembled into a battery pack. The battery pack may contain one or more battery modules. Those skilled in the art may select an appropriate number based on the application and capacity of the battery pack.

[0134] Figures 9 and 10 illustrate an example battery pack 2. Referring to Figures 9 and 10 , the battery pack 2 may include a battery box and multiple battery modules 3 disposed within the battery box. The battery box comprises an upper case 21 and a lower case 22. The upper case 21 can be positioned over the lower case 22 to form an enclosed space for accommodating the battery modules 3. The multiple battery modules 3 can be arranged in any manner within the battery box.

[0135] In addition, the present invention further provides an electrical device comprising the secondary battery provided by the present invention. The secondary battery can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices, electric vehicles, electric trains, ships, satellites, energy storage systems, and the like. Examples of mobile devices include, but are not limited to, mobile phones and laptop computers; examples of electric vehicles include, but are not limited to, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, and electric trucks.

[0136] As the electrical device, a secondary battery can be selected according to its usage requirements.

[0137] Fig. 11 shows an example of an electric device 4. The electric device 4 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.

[0138] As another example, the device may be a mobile phone, a tablet computer, a laptop computer, etc.

[0139] In order to make the purpose, technical solutions and advantages of the present invention more concise and clear, the present invention is illustrated by the following specific embodiments, but the present invention is by no means limited to these embodiments. The embodiments described below are only preferred embodiments of the present invention and can be used to describe the present invention. They should not be understood as limiting the scope of the present invention. It should be pointed out that any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

[0140] In order to better illustrate the present invention, the present invention will be further described below with reference to the following embodiments.

[0141] Example 1

[0142] (1) Preparation of positive electrode sheet and positive electrode tab

[0143] Nickel-cobalt-manganese (NCM111) ternary material, conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) were added in a mass ratio of 97:1:2, and N-methylpyrrolidone was added and mixed and stirred for 2 hours to obtain a positive electrode slurry;

[0144] Insulating particles (Al2O3 particles, Dv50 particle size of 5 μm), overcharge additive Li2C2O4, and binder (polypropylene) in a mass ratio of 15:15:70 were mixed, and solvent water was added to mix to obtain an anti-overcharge slurry;

[0145] The positive electrode slurry is evenly coated on the main area of ​​the 6μm thick aluminum foil of the positive electrode current collector, and the anti-overcharge slurry is evenly coated on the edge of one side of the main area of ​​the positive electrode current collector (i.e., the anti-overcharge protection area A), and the edge is left blank and uncoated as a blank area. After drying, cold pressing, and slitting, the positive electrode slurry forms a positive electrode active layer and the anti-overcharge slurry forms an anti-overcharge layer. Accordingly, the positive electrode sheet, the anti-overcharge layer of the positive electrode tab, and the blank area of ​​the positive electrode tab are formed from the main area to the edge. The structure of the positive electrode sheet and the positive electrode tab is shown in Figure 1, and the blank area is continuous. The thickness of the positive electrode active layer is 150μm.

[0146] (2) Preparation of negative electrode sheet

[0147] Graphite, binder styrene-butadiene rubber (SBR), dispersant (CMC-Na), and conductive carbon black (Super-P, SP) were thoroughly stirred in a suitable amount of deionized water at a weight ratio of 96:2:1:1 to prepare a negative electrode slurry. The negative electrode active slurry was then coated onto a 6μm-thick copper foil, dried, and cold-pressed to form a negative electrode active material layer, which was then cut into negative electrode sheets; the thickness of the negative electrode active layer was 150μm.

[0148] (3) Isolation film

[0149] Polypropylene film is used as the isolation film.

[0150] (4) Electrolyte

[0151] LiPF6 was dissolved in a solvent of ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate in a volume ratio of 1:1:1 to prepare an electrolyte with a concentration of 1 mol / L.

[0152] (5) Production of lithium-ion batteries

[0153] The positive electrode sheet with the positive electrode tab, the separator, and the negative electrode sheet are stacked and wound in order to obtain a bare cell; the bare cell is placed in a packaging shell, dried, and then injected with electrolyte. After vacuum packaging, standing, forming, shaping and other processes, a lithium-ion battery is obtained.

[0154] Other Examples 1 to 26

[0155] It is basically the same as Example 1, except that some parameters (type and content of anti-overcharge additives, type and content of insulating particles, thickness of anti-overcharge layer, area ratio of anti-overcharge layer to positive electrode active layer) are different, as shown in Table 1.

[0156] Examples 27 to 29

[0157] It is basically the same as Example 1, except that: a first tab glue layer is further coated on the surface of the anti-overcharge layer of the positive electrode tab, and the first tab glue layer is a polypropylene layer; the difference between Examples 27 to 29 is that the thickness of the first tab glue layer is different.

[0158] Example 30

[0159] It is basically the same as Example 1, except that the positive electrode tab and the positive electrode sheet in Example 30 are separate structures, as specifically shown in Figure 4.

[0160] The steps for preparing the positive electrode sheet and the positive electrode ear are as follows:

[0161] A nickel-cobalt-manganese (NCM111) ternary material, conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) were prepared in a mass ratio of 97:1:2, and N-methylpyrrolidone was added and mixed and stirred for 2 hours to obtain a positive electrode slurry; the positive electrode slurry was evenly coated on a 6 μm thick aluminum foil of the positive electrode current collector, and the positive electrode sheets were formed by drying, cold pressing, and slitting.

[0162] Insulating particles (Al2O3 particles, Dv50 particle size of 5 μm), overcharge additive Li2C2O4, and binder (polypropylene) in a mass ratio of 15:15:70 were mixed, and solvent water was added to mix to obtain an anti-overcharge slurry;

[0163] The anti-overcharge slurry is evenly coated on an area of ​​the 6μm thick aluminum foil of the current collector to form an anti-overcharge layer, and polypropylene glue is coated on the packaging area adjacent to the anti-overcharge layer. After drying, cold pressing, and slitting, the positive electrode tab is formed. The structure is shown in Figure 4, in which the anti-overcharge layer 1212 and the second tab glue layer 1214 (polypropylene layer) arranged in the same layer are respectively formed in the adjacent areas on the surface of the first current collector 1211 (not shown).

[0164] Comparative Example 1

[0165] The process is basically the same as Example 1, except that the positive electrode tab and the positive electrode sheet are prepared as follows:

[0166] A nickel-cobalt-manganese (NCM111) ternary material, conductive carbon black, and binder polyvinylidene fluoride (PVDF) were prepared in a mass ratio of 97:1:2, and N-methyl pyrrolidone was added. The mixture was mixed and stirred for 2 hours, and then an overcharge additive Li2C2O4 (whose mass was 15% of the total mass of the nickel-cobalt-manganese (NCM111) ternary material, conductive carbon black, and binder polyvinylidene fluoride) was added to obtain a positive electrode slurry.

[0167] Insulating particles (Al2O3 particles) and a binder (polypropylene) in a mass ratio of 15:85 were mixed, and solvent water was added to mix to obtain a tab rubber material;

[0168] The positive electrode slurry is evenly coated on the main area of ​​the positive electrode current collector, and the tab rubber is evenly coated on one edge of the main area of ​​the positive electrode current collector (i.e., the overcharge protection zone A). The outermost edge is left uncoated as a blank area. After drying, cold pressing, and slitting, the positive electrode slurry forms the positive electrode active layer and the tab rubber forms the tab rubber layer. Accordingly, the positive electrode sheet, the positive tab anti-overcharge layer, and the blank area of ​​the positive tab are formed from the main area to the outermost edge. As shown in Figure 1, the blank area is continuous.

[0169] The following is the battery performance test

[0170] (1) Cyclic performance test

[0171] Cycle capacity retention rate

[0172] Taking Example 1 as an example, five samples of the sodium battery of Example 1 were taken as a group. One group of sodium batteries was charged to 3.7V at a constant current of 1C at 25°C, then charged at a constant voltage of 3.7V until the current dropped to 0.05C, and then discharged to 2.5V at a constant current of 1C to obtain the first cycle discharge capacity (Cd1). This charge and discharge process was repeated until the nth cycle, and the discharge capacity of the sodium battery after n cycles was obtained, which was recorded as Cdn. The capacity retention rate of each sodium battery was calculated according to the following formula, and then the average value was taken. The results are shown in Table 1:

[0173] Capacity retention rate = discharge capacity after n cycles (Cdn) / first cycle discharge capacity (Cd1).

[0174] (2) Anti-overcharge test

[0175] Taking Example 1 as an example, 20 sodium battery samples from Example 1 were collected as a group. Each group of sodium batteries was discharged at a constant current of 0.5C at 25±5°C to 3.0V, allowed to rest for 12-24 hours, and then charged at a constant current of 3C to 10V for 7 hours. The results were observed. The overcharge test was considered passed if there was no fire or explosion. The overcharge pass rate was calculated based on the number of samples that passed the test and the total number of samples.

[0176] Some parameters and performance test results of the secondary batteries of various embodiments and comparative examples are shown in Table 1.

[0177] Table 1

[0178] “ / ” means that this parameter is not involved.

[0179] As can be seen from Table 1 above, Comparative Example 1 adds the anti-overcharge additive to the positive electrode active layer; compared with Comparative Example 1, each embodiment can effectively improve the cycle performance of the secondary battery while also having good anti-overcharge performance.

[0180] Examples 1 to 8 are essentially the same, differing in the type of overcharge prevention additive. As can be seen from Examples 1 to 5, the batteries produced in Examples 1 and 5 exhibit better cycle performance, while the batteries produced in Examples 2 to 4 exhibit better overcharge prevention performance. Examples 6 to 8 further utilize a combination of two overcharge prevention additives, achieving both better cycle performance and overcharge prevention performance.

[0181] Examples 1 and 9 to 14 are basically the same, except that the content of the anti-overcharge additive is different. The mass content of the anti-overcharge additive in the anti-overcharge layer is 0.5% to 50%, which can effectively improve the cycle performance of the secondary battery on the basis of having good anti-overcharge performance; further, the mass content of the anti-overcharge additive in the anti-overcharge layer is 2% to 20%, which can have both good anti-overcharge performance and cycle performance.

[0182] Examples 1 and 15 to 18 are basically the same, except that at least one of the type and content of the insulating particles is different. The mass content of the insulating particles in the anti-overcharge layer is further 5% to 20%, which can have both good anti-overcharge performance and cycle performance.

[0183] Examples 1 and 19 to 22 are basically the same, except that the thickness of the anti-overcharge layer is different. When the thickness of the anti-overcharge layer is within 30 to 100 μm, it can have both good anti-overcharge performance and cycle performance.

[0184] Examples 1 and 23 to 26 are basically the same, except that the area ratio of the anti-overcharge layer to the positive electrode active layer is different. When the area ratio of the anti-overcharge layer to the positive electrode active layer is in the range of (3 to 7): 100, it can have both good anti-overcharge performance and cycle performance.

[0185] Examples 27 to 29 are basically the same as Example 1, except that a first tab glue layer is further coated on the surface of the anti-overcharge layer of the positive electrode tab; the difference between Examples 27 to 29 is that the thickness of the first tab glue layer is different, which can provide better insulation protection performance and further improve its cycle performance.

[0186] Example 30 is basically the same as Example 1, except that the positive electrode tab and the positive electrode sheet in Example 30 are separate structures, and the cycle performance and overcharge protection performance of the battery prepared therefrom are equivalent to those in Example 1.

[0187] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0188] The above-described embodiments merely represent several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art may make several modifications and improvements without departing from the concept of the present invention, and these modifications and improvements fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be based on the appended claims, and the description and drawings may be used to interpret the content of the claims.

Claims

1. A secondary battery, comprising a positive electrode plate and a positive electrode tab connected to the positive electrode plate, wherein the positive electrode tab comprises a first current collector and an anti-overcharge layer, wherein the anti-overcharge layer is disposed on a surface of the first current collector, and the anti-overcharge layer comprises an anti-overcharge additive.

2. The secondary battery according to claim 1, wherein The anti-overcharge additive includes at least one of Li2C2O4, Li2C4O4, Li2C3O5, Li2C4O6, Li2C6O6, Li2CO3, LiN3, LiODFB, Li2O, Li3N, LiF, LiCl, Li2S, LiBH4, CH3COOLi, LiNO3 and Li2SO4.

3. The secondary battery according to claim 2, wherein: In the anti-overcharge additive, the mass content of Li2C2O4 is 50% to 95%.

4. The secondary battery according to any one of claims 1 to 3, wherein: The anti-overcharging layer also includes a binder; The mass content of the anti-overcharging additive is 0.5% to 50% based on the total mass of the anti-overcharging layer.

5. The secondary battery according to claim 4, wherein: The binder includes at least one of polypropylene, polyacrylic acid, polystyrene, polyterephthalic acid, styrene-butadiene rubber, water-based acrylic resin, polytetrafluoroethylene, ethylene-vinyl acetate copolymer, carboxymethyl cellulose, polyvinyl alcohol, polyvinyl butyral and polyvinylidene fluoride.

6. The secondary battery according to any one of claims 1 to 5, wherein: The positive electrode plate includes a second current collector and a positive electrode active layer disposed on the second current collector; The area ratio of the anti-overcharge layer to the positive electrode active layer is (1-10):

100.

7. The secondary battery according to any one of claims 1 to 6, wherein: The anti-overcharge additive can decompose and generate gas at a voltage of ≥4.2V.

8. The secondary battery according to any one of claims 1 to 7, wherein: The anti-overcharge layer also includes insulating particles; The mass content of the insulating particles is 1% to 30% based on the total mass of the anti-overcharging layer.

9. The secondary battery according to any one of claims 1 to 8, wherein: The thickness of the anti-overcharging layer is 10 μm to 150 μm.

10. The secondary battery according to any one of claims 1 to 9, wherein: The positive electrode tab further includes a first tab adhesive layer, and the first tab adhesive layer is disposed on a surface of the anti-overcharge layer away from the first current collector.

11. The secondary battery according to claim 10, wherein The anti-overcharging layer also includes a conductive agent with a mass content of 0 to 5%.

12. The secondary battery according to claim 10 or 11, wherein: The thickness of the first tab glue layer is 5 μm to 100 μm.

13. The secondary battery according to any one of claims 1 to 12, wherein: The positive electrode plate includes a second current collector and a positive active layer arranged on the second current collector, the second current collector and the first current collector are interconnected to form a whole, the surface of the first current collector also includes a blank area adjacent to the anti-overcharging layer, and the anti-overcharging layer is located between the blank area and the second current collector.

14. The secondary battery according to any one of claims 1 to 13, wherein: The positive electrode tab also includes a second tab glue layer adjacent to and arranged in the same layer as the anti-overcharge layer.

15. The secondary battery according to claim 14, wherein The thickness of the second tab glue layer is 30 μm to 150 μm.

16. An electric device comprising the secondary battery according to any one of claims 1 to 15.

Images