Safety battery

Abstract

The invention relates to a safety battery, and belongs to the technical field of batteries. In the safety battery, the surface of the single cell is covered with the thermosensitive response inert gas generation layer, and when the single cell is subjected to thermal runaway or suffers from external thermal shock to reach a response temperature, a thermosensitive response inert gas generation material begins to absorb heat and decompose, and inert gases such as carbon dioxide or nitrogen are continuously generated. And along with the continuous increase of the inert gas, the sealing layer is broken through, so that an inert gas atmosphere is formed in the closed battery box body, and comburent is effectively reduced. The thermosensitive response inert gas generating material absorbs heat and continuously releases inert gas at the same time, so that the inert atmosphere in the battery box body is ensured, and the safety problems of battery thermal runaway, fire and combustion and the like caused by abnormal electrical connection, poor battery cell consistency, battery abuse and the like are effectively avoided. The safety battery can be used in the field of commercial vehicles such as pure electric mining trucks and pure electric dump trucks.

Description

Technical Field

[0001] The present invention relates to a safety battery, belonging to the technical field of batteries. Background Art

[0002] In recent years, due to excellent electrochemical performance, no memory effect, environmental friendliness and other advantages, lithium-ion batteries have achieved large-scale commercial applications. With the wide popularization of new energy vehicles, safety accidents of new energy vehicles equipped with lithium-ion batteries occur frequently, and the safety of lithium-ion batteries has gradually become the focus of people's attention. Vehicle collisions, abnormal electrical connections, poor cell consistency, and battery abuse are the main reasons for battery failure and subsequent thermal runaway. At present, the solutions for improving battery safety mainly focus on aspects such as battery material modification, electrode and cell structure optimization, and introduction of external safety components.

[0003] Regarding the process in which battery failure leads to an increase in thermal runaway temperature and subsequent safety accidents such as ablation and fire, Chinese patent document CN114872563B discloses a nitrogen protection system for power batteries. The nitrogen protection system for power batteries disclosed in this patent document includes an air compressor or a gas pump for generating high-pressure air, and also includes a nitrogen generation module connected to the air compressor or the gas pump. The nitrogen generation module includes a nitrogen generation device for separating nitrogen and oxygen from high-pressure air. The nitrogen generation device has a nitrogen outlet and an oxygen outlet. The nitrogen protection system for power batteries also includes a battery box, in which a power battery is installed. A nitrogen pipeline is connected between the battery box and the nitrogen outlet; an oxygen pipeline for supplying oxygen to the passenger area is provided on the oxygen outlet. Nitrogen enters the battery box, controlling the oxygen concentration in the battery box within a range far from combustion and explosion, preventing accidents such as combustion and explosion. Oxygen enters the passenger area, increasing the oxygen concentration in the passenger area and improving the comfort of passengers. However, the nitrogen protection system for power batteries disclosed in this patent document cannot initiate a flame retardant measure when the thermal runaway temperature rises, and cannot effectively improve the battery safety performance.

[0004] Since the current solutions for improving battery safety mainly focus on aspects such as battery material modification, electrode and cell structure optimization, and introduction of external safety components, and cannot initiate a flame retardant measure when the thermal runaway temperature rises, the technical solution of the present invention can directly trigger the release of inert gas when the thermal runaway temperature of the battery rises by introducing a thermally responsive protection measure inside the battery, playing a role in flame retardancy. Summary of the Invention

[0005] The purpose of the present invention is to provide a safety battery, which can solve the problem that the current power battery protection system cannot initiate a flame retardant measure when the thermal runaway temperature rises.

[0006] To achieve the above purpose, the technical solution adopted by the safety battery of the present invention is as follows:

[0007] A safety battery includes single-cell battery cores. A thermally responsive inert gas generating layer and a sealing layer are sequentially attached to the surface of not less than 95% of the single-cell battery cores. The thermally responsive inert gas generating layer is composed of azobisisobutyronitrile and a binder, the mass fraction of azobisisobutyronitrile is 95% - 98%, and the thickness of the thermally responsive inert gas generating layer is 50 - 100 μm.

[0008] In the safety battery of the present invention, the surface of the single-cell battery core is covered with a thermally responsive inert gas generating layer. When the single-cell battery core undergoes thermal runaway or is subjected to external thermal shock and reaches the response temperature, the thermally responsive inert gas generating material begins to absorb heat and decompose, continuously generating inert gases such as carbon dioxide or nitrogen. As the inert gas continuously increases, the sealing layer is broken through, thereby forming an inert gas atmosphere in the sealed battery box, effectively reducing the combustibles. While absorbing heat, the thermally responsive inert gas generating material continuously releases inert gases, thus ensuring an inert atmosphere in the battery box and effectively avoiding safety problems such as battery thermal runaway, fire, and combustion caused by abnormal electrical connections, poor cell consistency, and battery abuse. The safety battery of the present invention can be used in commercial vehicle fields such as pure electric mining vehicles and pure electric dump trucks.

[0009] By introducing a thermally responsive inert gas releasing material inside the battery, the present invention can release a protective gas when the temperature reaches a specific value, form an inert gas atmosphere in the battery box, effectively inhibit the harm of battery thermal runaway, prevent fire accidents from occurring, and improve battery safety.

[0010] The thermally responsive inert gas generating material in the safety battery of the present invention will not affect the electrochemical performance of the battery during normal use of the battery. When the battery undergoes thermal runaway and reaches the response temperature, the thermally responsive inert gas generating material begins to absorb heat and decompose, and the decomposition products are inert gases such as carbon dioxide or nitrogen. For the safety battery of the present invention, when the temperature rises due to abnormal electrical connections, poor cell consistency, and battery abuse, etc., resulting in battery thermal runaway, an inert gas atmosphere can be formed in the sealed battery box, effectively reducing the combustibles and avoiding the occurrence of fire and combustion safety problems.

[0011] In the present invention, the inert gas generating material refers to a material that will react with the change of temperature and release a protective gas when the temperature reaches a certain level; the protective gas refers to an inert gas that can isolate oxygen in the air and play a flame retardant role. If the thickness of the thermally responsive inert gas generating layer is too large, it will affect the battery energy density and lead to a decline in electrical performance.

[0012] Preferably, the binder is polyvinylidene fluoride.

[0013] Preferably, the weight-average molecular weight of polyvinylidene fluoride is 400,000 - 700,000.

[0014] Preferably, the sealing layer is an aluminum-plastic film.

[0015] Preferably, the single cell includes a plurality of positive electrode sheets and a plurality of negative electrode sheets, and a separator is disposed between adjacent positive electrode sheets and negative electrode sheets.

[0016] Preferably, the positive electrode sheet includes a positive electrode current collector and an active material layer disposed on the positive electrode current collector. The active material layer is composed of a positive electrode active material, a conductive agent, and a binder. The mass fraction of the positive electrode active material is 85% - 97%, the mass fraction of the conductive agent is 1% - 5%, and the mass fraction of the binder is 2% - 10%. The positive electrode active material is lithium iron phosphate, and the conductive agent is carbon black and / or carbon nanotubes. The negative electrode sheet is a graphite negative electrode or a silicon-carbon negative electrode, and the thickness of the negative electrode sheet is 8 - 20 μm. The separator is a polypropylene film coated with an alumina ceramic coating, and the thickness of the alumina ceramic coating is 20 - 30 μm.

[0017] Preferably, the safety battery further includes a battery housing for placing the single cell, and there is also an electrolyte in the battery housing.

[0018] Preferably, the electrolyte is a lithium hexafluorophosphate electrolyte. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic structural diagram of the safety battery according to Embodiment 1 of the present invention;

[0020] Figure 2 It is a schematic structural diagram of the safety battery according to Embodiment 2 of the present invention;

[0021] Figure 3 It is a schematic structural diagram of the safety battery according to Embodiment 6 of the present invention;

[0022] Figure 4 It is a schematic structural diagram of the safety battery according to Embodiment 7 of the present invention;

[0023] Figure 5 It is a schematic structural diagram of the safety battery according to Embodiment 8 of the present invention;

[0024] The reference numerals are as follows: 1 - single cell; 2 - thermally responsive inert gas generating layer; 3 - sealing layer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] The safety battery of the present invention is a pioneering invention. The safety battery of the present invention includes a single cell, and a thermally responsive inert gas generating layer and a sealing layer are sequentially attached to the surface of not less than 95% of the single cell. The thermally responsive inert gas generating layer is composed of azobisisobutyronitrile and a binder, and the mass fraction of azobisisobutyronitrile is 95% - 98%. The thickness of the thermally responsive inert gas generating layer is 50 - 100 μm.

[0026] In some preferred embodiments, the monomer cell includes a plurality of positive electrode plates and a plurality of negative electrode plates, and a separator is disposed between adjacent positive electrode plates and negative electrode plates; the positive electrode plate includes a positive electrode current collector and an active material layer disposed on the positive electrode current collector, and the active material layer is composed of a positive electrode active material, a conductive agent, and a binder.

[0027] In some preferred embodiments, the positive electrode active material is LiFePO 4 、LiCoO 2 、LiMn 2 O 4 、LiFe x Mn 1-x PO 4 (0 ≤ x ≤ 1), LiNi x Co y Mn z O 2 (0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1, and x + y + z = 1), LiNi x Co y Al z O 2 (0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1, and x + y + z = 1).

[0028] In some preferred embodiments, the positive electrode active material is LiFePO 4 。

[0029] In some preferred embodiments, the conductive agent is artificial graphite, carbon nanotubes, carbon black, carbon nanofibers, graphene, activated carbon.

[0030] In some preferred embodiments, the conductive agent is composed of carbon black and carbon nanotubes.

[0031] In some preferred embodiments, the binder in the active material layer is hydroxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), vinylidene fluoride copolymer, polytetrafluoroethylene (PTFE), polyacrylate.

[0032] In some preferred embodiments, the binder in the active material layer is polyvinylidene fluoride (PVDF).

[0033] In some preferred embodiments, the positive electrode current collector is aluminum foil or copper foil.

[0034] In some preferred embodiments, the positive electrode current collector is aluminum foil.

[0035] In some preferred embodiments, the negative electrode plate is one of a commercial graphite negative electrode and a silicon-carbon negative electrode; the separator is a commercial conventional separator; the electrolyte is a commercial electrolyte; the encapsulation shell is one of a commercial steel shell, an aluminum shell, or a plastic shell.

[0036] In some preferred embodiments, the single cell is manufactured by a cell stacking or winding process; specifically, it includes the following steps: placing a separator between the positive and negative electrode plates, stacking or winding the negative electrode plate and the positive electrode plate in sequence, and then performing baking, liquid injection, encapsulation, formation, aging, secondary encapsulation, and grading processes.

[0037] In some preferred embodiments, the single cell is one of commercial cells such as square cells, soft-pack cells, and cylindrical cells.

[0038] In some preferred embodiments, the single cell is a square cell.

[0039] In some preferred embodiments, a thermally responsive inert gas generating layer and a sealing layer are sequentially attached to both sides of the single cell in the length and width directions.

[0040] In some preferred embodiments, the thickness of the thermally responsive inert gas generating layer is 50 - 100 μm.

[0041] In some preferred embodiments, the binder is polyvinylidene fluoride, vinylidene fluoride copolymer, or polytetrafluoroethylene.

[0042] In some preferred embodiments, the binder is polyvinylidene fluoride.

[0043] In some preferred embodiments, the thermally responsive inert gas generating layer is obtained by molding a mixture composed of an inert gas generating material, a binder, and a solvent. The mold used for molding is a commercial mold made of rectangular stainless steel or other corrosion-resistant materials with a certain depth and a smooth surface, which can be used to prepare thermally responsive inert gas generating layers with different thicknesses.

[0044] In some preferred embodiments, the sealing layer is an aluminum-plastic film, a polyvinyl chloride film, a polypropylene film, a polyvinyl alcohol film, a polyethylene terephthalate film, or a nylon film.

[0045] In some preferred embodiments, the sealing layer is an aluminum-plastic film.

[0046] When manufacturing and encapsulating a safety battery, the structure can be improved according to the situation. In some preferred embodiments, the thermally responsive inert gas generating layer has the same shape and size as the surface of the single cell it covers, and is sealed by the sealing layer to improve the durability of the thermally responsive inert gas generating layer.

[0047] The present invention provides a highly safe power battery with thermally responsive self-releasing protective gas, and a thermally responsive inert gas generating layer is covered on the surface of the single cell. When the single cell undergoes thermal runaway or is subjected to external thermal shock to reach the response temperature, the thermally responsive inert gas generating material begins to absorb heat and decompose, continuously generating inert gases such as carbon dioxide or nitrogen. As the inert gas continuously increases, the sealing layer is broken through, thereby forming an inert gas atmosphere in the closed battery box, effectively reducing the combustibles. The thermally responsive inert gas generating material continuously releases inert gas while absorbing heat, thereby ensuring the inert atmosphere in the battery box and effectively avoiding safety problems such as battery thermal runaway, fire and combustion caused by abnormal electrical connection, poor cell consistency and battery abuse.

[0048] The technical solution of the present invention will be further described below in conjunction with specific embodiments.

[0049] Example 1

[0050] The safety battery of this embodiment includes a single cell. The single cell is square. A thermally responsive inert gas generating layer and a sealing layer are sequentially attached to the bottom surface in the length and width directions of the single cell (as Figure 1 shown, Figure 1 in which, 1 represents the single cell; 2 represents the thermally responsive inert gas generating layer; 3 represents the sealing layer);

[0051] The single cell in the safety battery of this embodiment includes a plurality of positive electrode plates and a plurality of negative electrode plates. A separator is arranged between adjacent positive electrode plates and negative electrode plates. The positive electrode plate includes a positive current collector and an active material layer arranged on the positive current collector. The positive current collector is aluminum foil. The active material layer is composed of a positive active material, a conductive agent and a binder with a mass ratio of 95:3:3. The positive active material is lithium iron phosphate (LiFePO 4 ), the average particle size of lithium iron phosphate is 5μm; the conductive agent is composed of conductive carbon black and carbon nanotubes with a mass ratio of 2:1. The average particle size of the conductive carbon black is 30nm, the average length of the carbon nanotubes is 6nm, the average inner diameter is 2nm, and the average outer diameter is 3nm; the binder is polyvinylidene fluoride (PVDF), and the weight average molecular weight of polyvinylidene fluoride is 400,000 to 700,000; the negative electrode plate is a commercial graphite negative electrode, the thickness of the negative electrode plate is 20μm, the separator is a polypropylene film coated with an alumina ceramic coating, and the thickness of the alumina ceramic coating is 20 - 30μm.

[0052] The safety battery of this embodiment further includes a battery housing for placing the single cell, and there is also an electrolyte in the battery housing. The electrolyte is a lithium hexafluorophosphate electrolyte.

[0053] The preparation method of the single cell is as follows: 95 parts by weight of LiFePO 4, 2 parts by weight of conductive carbon black, 1 part by weight of carbon nanotubes, 2 parts by weight of PVDF and 150 parts by weight of NMP solvent are blended, and after being uniformly dispersed, they are coated on an aluminum foil. After baking, drying and rolling, a positive electrode sheet is obtained; using the cell stacking process, a separator is placed between the positive and negative electrode sheets, and the negative electrode sheet and the positive electrode sheet are stacked in sequence (that is, the negative electrode sheet, the separator and the positive electrode sheet are stacked in sequence according to the conventional stacking process), and then baking, liquid injection, encapsulation, formation, aging, secondary encapsulation and grading processes are carried out to obtain a single cell.

[0054] In the safety battery of this embodiment, the thermally responsive inert gas generating layer is composed of an azo compound and polyvinylidene fluoride. The mass ratio of the azo compound to polyvinylidene fluoride is 95:5. The azo compound is azodiisobutyronitrile, and the weight-average molecular weight of polyvinylidene fluoride is 400,000 to 700,000. The thickness of the thermally responsive inert gas generating layer is 50 μm; the sealing layer is an aluminum-plastic film, and the thickness of the sealing layer is 150 μm.

[0055] The preparation method of the thermally responsive inert gas generating layer is as follows: 95 parts by weight of an azo compound, 5 parts by weight of PVDF and 100 parts by weight of NMP solvent are blended, and after being uniformly dispersed, they are coated on a mold. After low-temperature drying and separation, a thermally responsive inert gas generating layer with a thickness of 50 μm is obtained. The shape and size of the thermally responsive inert gas generating layer are the same as those of the bottom surface of the single cell in the length and width directions.

[0056] The preparation method of the safety battery of this embodiment is as follows: the thermally responsive inert gas generating layer is covered on the bottom surface of the single cell in the length and width directions, and then the sealing layer is covered on the surface of the thermally responsive inert gas generating layer. Then, a blue film tape is used to tightly bond the single cell, the thermally responsive inert gas generating layer and the sealing layer together by winding. Then, the single cell with the thermally responsive inert gas generating layer and the sealing layer attached is placed in a battery case, and then electrolyte is added and sealed to obtain a safety battery.

[0057] Example 2

[0058] The difference between the safety battery of this embodiment and the safety battery of Example 1 is only that on the bottom surface and the top surface of the single cell of the safety battery of this embodiment, a thermally responsive inert gas generating layer and a sealing layer are sequentially attached (as Figure 2 shown, Figure 2 in, 1 represents a single cell; 2 represents a thermally responsive inert gas generating layer; 3 represents a sealing layer). In this embodiment, on the surface of the single cell with an area ratio of 95%, a thermally responsive inert gas generating layer and a sealing layer are sequentially attached.

[0059] Example 3

[0060] The difference between the safety battery of this embodiment and the safety battery of Embodiment 2 is only that the mass ratio of azo compound to polyvinylidene fluoride in the thermosensitive-responsive inert gas generating layer of the safety battery of this embodiment is 97:3. The preparation method of the thermosensitive-responsive inert gas generating layer in the safety battery of this embodiment includes the following steps: Blend 97 parts by weight of azo compound, 3 parts by weight of PVDF, and 100 parts by weight of NMP solvent, disperse evenly and coat onto a mold, and obtain a thermosensitive-responsive inert gas generating layer with a thickness of 50 μm after low-temperature drying and separation.

[0061] Embodiment 4

[0062] The difference between the safety battery of this embodiment and the safety battery of Embodiment 2 is only that the mass ratio of azo compound to polyvinylidene fluoride in the thermosensitive-responsive inert gas generating layer of the safety battery of this embodiment is 98:2. The preparation method of the thermosensitive-responsive inert gas generating layer in the safety battery of this embodiment includes the following steps: Blend 98 parts by weight of azo compound, 2 parts by weight of PVDF, and 100 parts by weight of NMP solvent, disperse evenly and coat onto a mold, and obtain a thermosensitive-responsive inert gas generating layer with a thickness of 50 μm after low-temperature drying and separation.

[0063] Embodiment 5

[0064] The difference between the safety battery of this embodiment and the safety battery of Embodiment 2 is only that the mass ratio of azo compound to polyvinylidene fluoride in the thermosensitive-responsive inert gas generating layer of the safety battery of this embodiment is 90:10. The preparation method of the thermosensitive-responsive inert gas generating layer in the safety battery of this embodiment includes the following steps: Blend 90 parts by weight of azo compound, 10 parts by weight of PVDF, and 100 parts by weight of NMP solvent, disperse evenly and coat onto a mold, and obtain a thermosensitive-responsive inert gas generating layer with a thickness of 50 μm after low-temperature drying and separation.

[0065] Embodiment 6

[0066] The difference between the safety battery of this embodiment and the safety battery of Embodiment 2 is only that the thickness of the thermosensitive-responsive inert gas generating layer of the safety battery of this embodiment is 75 μm. The monomer cell in the safety battery of this embodiment with the thermosensitive-responsive inert gas generating layer and the sealing layer attached is as Figure 3 shown ( Figure 3 in which, 1 represents the monomer cell; 2 represents the thermosensitive-responsive inert gas generating layer; 3 represents the sealing layer).

[0067] Embodiment 7

[0068] The difference between the safety battery of this embodiment and the safety battery of Embodiment 2 is only that the thickness of the thermally responsive inert gas generating layer of the safety battery of this embodiment is 100 μm. The monomer cell in the safety battery of this embodiment with the thermally responsive inert gas generating layer and the sealing layer attached is as Figure 4 shown ( Figure 4 in which, 1 represents the monomer cell; 2 represents the thermally responsive inert gas generating layer; 3 represents the sealing layer).

[0069] Embodiment 8

[0070] The difference between the safety battery of this embodiment and the safety battery of Embodiment 2 is only that the thickness of the thermally responsive inert gas generating layer of the safety battery of this embodiment is 25 μm. The monomer cell in the safety battery of this embodiment with the thermally responsive inert gas generating layer and the sealing layer attached is as Figure 5 shown ( Figure 5 in which, 1 represents the monomer cell; 2 represents the thermally responsive inert gas generating layer; 3 represents the sealing layer).

[0071] Embodiment 9

[0072] The difference between the safety battery of this embodiment and the safety battery of Embodiment 2 is that in the safety battery of this embodiment, the weight fraction of LiFePO 4 used in preparing the positive electrode sheet is 97 parts, the weight fraction of conductive carbon black is 0.7 parts, the weight fraction of carbon nanotubes is 0.3 parts, and the weight fraction of PVDF is 2 parts.

[0073] Embodiment 10

[0074] The difference between the safety battery of this embodiment and the safety battery of Embodiment 2 is that in the safety battery of this embodiment, the weight fraction of LiFePO 4 used in preparing the positive electrode sheet is 85 parts, the weight fraction of conductive carbon black is 3 parts, the weight fraction of carbon nanotubes is 2 parts, and the weight fraction of PVDF is 10 parts.

[0075] Embodiment 11

[0076] The difference between the safety battery of this embodiment and the safety battery of Embodiment 2 is only that the conductive agent in the safety battery of this embodiment is conductive carbon black.

[0077] Embodiment 12

[0078] The difference between the safety battery of this embodiment and the safety battery of Embodiment 2 is only that the conductive agent in the safety battery of this embodiment is carbon nanotubes.

[0079] The difference between the safety battery of other embodiments and the safety battery of Embodiment 2 is only that a thermally responsive inert gas generating layer and a sealing layer are sequentially attached to the surface of the single cell with an area ratio of 100%; or the negative electrode sheet is a silicon-carbon negative electrode, and the thickness of the negative electrode sheet is 8-20 μm.

[0080] Comparative Example 1

[0081] The difference between the safety battery of this comparative example and the safety battery of Embodiment 2 is only that the azo compound in the thermally responsive inert gas generating layer of the safety battery of this comparative example is 2,2'-Azobis(2-methylbutyronitrile).

[0082] Comparative Example 2

[0083] The difference between the safety battery of this comparative example and the safety battery of Embodiment 2 is only that the azo compound in the thermally responsive inert gas generating layer of the safety battery of this comparative example is Dimethyl 2,2'-azobis(2-methylpropionate).

[0084] Comparative Example 3

[0085] The difference between the safety battery of this comparative example and the safety battery of Embodiment 2 is only that the azo compound in the thermally responsive inert gas generating layer of the safety battery of this comparative example is prepared by mixing 2,2'-Azobis(2-methylpropionitrile), 2,2'-Azobis(2-methylbutyronitrile), and Dimethyl 2,2'-azobis(2-methylpropionate) in a mass ratio of 1:1:1.

[0086] Comparative Example 4

[0087] The difference between the safety battery of this comparative example and the safety battery of Embodiment 2 is only that the azo compound in the thermally responsive inert gas generating layer of the safety battery of this comparative example is replaced with calcium carbonate.

[0088] Comparative Example 5

[0089] The difference between the safety battery of this comparative example and the safety battery of Embodiment 2 is only that the azo compound in the thermally responsive inert gas generating layer of the safety battery of this comparative example is replaced with an alkane (the alkane is isoparaffin).

[0090] Comparative Example 6

[0091] The difference between the safety battery of this comparative example and the safety battery of Embodiment 2 is only that the azo compound in the thermally responsive inert gas generating layer of the safety battery of this comparative example is replaced with a fluorocarbon compound (the fluorocarbon compound is carbon tetrafluoride).

[0092] Comparative Example 7

[0093] The difference between the safety battery of this comparative example and the safety battery of Embodiment 2 is only that the polyvinylidene fluoride in the thermally responsive inert gas generating layer of the safety battery of this comparative example is replaced with a vinylidene fluoride copolymer.

[0094] Comparative Example 8

[0095] The difference between the safety battery of this comparative example and the safety battery of Example 2 is only that in the thermally responsive inert gas generating layer of the safety battery of this comparative example, the azo compound is replaced by metronidazole.

[0096] Comparative Example 9

[0097] The difference between the safety battery of this comparative example and the safety battery of Example 2 is only that in the thermally responsive inert gas generating layer of the safety battery of this comparative example, the azo compound is replaced by the flame retardant in Example 4 of the prior art CN115732816A, that is, a mixture composed of aluminum hydroxide, magnesium hydroxide and barium azodicarboxylate with a mass ratio of 40:40:20.

[0098] Experimental Example

[0099] In order to investigate the safety performance of the batteries of each example and comparative example, the batteries of each example and comparative example were charged at a constant current and constant voltage of 1C to 3.65V, and the charging cut-off current was 0.05C. In a sealed simulated battery box, the fully charged battery cells were left to stand for 1 h and then fixed on a heating plate with a power of 300W to be heated until the battery thermal runaway occurred, and the battery state was observed. The results are shown in Table 1.

[0100] Table 1 Safety performance of the batteries of each example and comparative example

[0101] Battery Thermal runaway state of battery cell Energy density (kWh / kg) Example 1 Emit thick smoke and spray sparks - Example 2 Emit thick smoke and do not catch fire 163.1 Example 3 Emit thick smoke and do not catch fire 163.0 Example 4 Emit thick smoke and do not catch fire 162.8 Example 5 Emit thick smoke and have small sparks - Example 6 Emit thick smoke and do not catch fire 160.7 Example 7 Emit thick smoke and do not catch fire 154.3 Example 8 Emit thick smoke and catch a small fire - Example 9 Emit thick smoke and do not catch fire 165.7 Example 10 Emit thick smoke and do not catch fire 145.8 Example 11 Emit thick smoke and do not catch fire 163.0 Example 12 Emit thick smoke and do not catch fire 163.1 Comparative Example 1 Emit thick smoke and have sparks 163.1 Comparative Example 2 Emit thick smoke and have small sparks 163.0 Comparative Example 3 Emit thick smoke and have tiny sparks 163.0 Comparative Example 4 Emit thick smoke and catch a small fire 163.1 Comparative Example 5 Emit thick smoke and catch a small fire 162.8 Comparative Example 6 Emit thick smoke and spray sparks 163.1 Comparative Example 7 Emit thick smoke and spray sparks 162.6 Comparative Example 8 Emit thick smoke and spray sparks 162.3 Comparative Example 9 Emit thick smoke and spray sparks 162.1

[0102] As can be seen from Table 1, the battery performances of Examples 2-4, Examples 6-7, and Examples 9-12 are all superior to those of the batteries of the comparative examples, indicating that by using the thermally responsive inert gas generating layer of the present invention and controlling its thickness and coverage area within a certain range, the safety performance of the battery can be improved.

Claims

1. A safe battery, characterized in that: The invention comprises a single cell, wherein a thermosensitive responsive inert gas generating layer and a sealing layer are sequentially laminated on no less than 95% of the surface of the single cell, the thermosensitive responsive inert gas generating layer is composed of azobisisobutyronitrile and a binder, the mass fraction of azobisisobutyronitrile is 95% to 98%, and the thickness of the thermosensitive responsive inert gas generating layer is 50 to 100 μm.

2. The safety battery according to claim 1, characterized in that: The binder is polyvinylidene fluoride.

3. The safety battery according to claim 2, characterized in that: The weight average molecular weight of polyvinylidene fluoride is 400,000 to 700,000.

4. The safety battery according to claim 1, characterized in that: The sealing layer is aluminum-plastic film.

5. The safety battery according to any one of claims 1 to 4, characterized in that: The single battery cell comprises a plurality of positive electrode sheets and a plurality of negative electrode sheets, and a separator is arranged between adjacent positive electrode sheets and negative electrode sheets.

6. The safety battery according to claim 5, characterized in that: The positive electrode sheet includes a positive electrode collector and an active material layer arranged on the positive electrode collector, the active material layer is composed of a positive electrode active material, a conductive agent and a binder, the mass fraction of the positive electrode active material is 85% to 97%, the mass fraction of the conductive agent is 1% to 5%, and the mass fraction of the binder is 2% to 10%; the positive electrode active material is lithium iron phosphate, and the conductive agent is carbon black and / or carbon nanotubes; the negative electrode sheet is a graphite negative electrode or a silicon-carbon negative electrode, and the thickness of the negative electrode sheet is 8 to 20 μm; the diaphragm is a polypropylene film coated with an alumina ceramic coating, and the thickness of the alumina ceramic coating is 20 to 30 μm.

7. The safety battery according to any one of claims 1 to 4, characterized in that: The safety battery also includes a battery casing for placing a single battery cell, and the battery casing contains electrolyte.

8. The safety battery according to claim 7, characterized in that: The electrolyte is lithium hexafluorophosphate electrolyte.

Images