Tin dioxide nanomaterial, preparation method thereof, gas sensor, secondary battery, and electric device

Abstract

This application relates to a tin dioxide nanomaterial and its preparation method, a gas-sensitive sensor, a secondary battery, and an electrical device. The tin dioxide nanomaterial is a hollow nanobox comprising N planar polygons, where N ≤ 10. The aforementioned tin dioxide nanomaterial exhibits high sensitivity and selectivity to EMC (electrochemical compatibility) gases in the electrolyte, enabling monitoring of electrolyte leakage with rapid early warning. It can be assembled with a battery for in-situ detection.

Description

Technical Field

[0001] This application relates to the field of gas-sensitive materials technology, and in particular to a tin dioxide nanomaterial and its preparation method, as well as a gas-sensitive sensor, a secondary battery and an electrical device containing the same. Background Technology

[0002] As people's pursuit of green production and lifestyles gradually increases, the new energy vehicle industry is developing rapidly. Among them, electric vehicles, as a typical new energy vehicle, have seen their ownership increase year by year, greatly alleviating energy shortages and environmental pollution problems. However, during the use of electric vehicles, the cumulative effect of time, changes in ambient temperature, and the increase in charge and discharge cycles often lead to the degradation of battery pack performance. In extreme conditions such as overcharging, over-discharging, overheating, and mechanical impact, the flammable and explosive electrolyte inside may leak. If timely warnings and repairs are not received, it may pose a huge safety hazard to people, roads, and society.

[0003] The solvent in the electrolyte is primarily a non-aqueous organic solvent, such as ethyl methyl carbonate (EMC), which transforms into organic gas molecules upon leakage. A gas sensor is a converter that uses gas-sensitive materials to transform the volume fraction of a gas into a corresponding electrical signal, enabling the detection of gas concentrations. However, traditional gas-sensitive materials struggle to achieve high sensitivity and selectivity for detecting electrolyte solvents. Summary of the Invention

[0004] This application provides a tin dioxide nanomaterial that exhibits high sensitivity and selectivity to EMC (Electromagnetic Compatibility) of characteristic gases in an electrolyte.

[0005] In a first aspect, this application provides a tin dioxide nanomaterial, wherein the tin dioxide nanomaterial is a hollow nanobox comprising N planar polygons, where N≤10.

[0006] In some embodiments, 5 ≤ N ≤ 9; alternatively, 5 ≤ N ≤ 7.

[0007] In some embodiments, the side length of any planar polygon of the nanobox is 200 nm to 450 nm.

[0008] In some embodiments, the wall thickness of any planar polygon of the nanobox is 5 nm to 30 nm.

[0009] In some embodiments, the tin dioxide nanomaterial has a specific surface area of ​​50–60 m². 2 / g.

[0010] In some embodiments, the grain size of the tin dioxide nanomaterial is 3 nm to 8 nm.

[0011] A second aspect of this application provides a method for preparing tin dioxide nanomaterials, comprising the following steps:

[0012] Preparation of cuprous oxide template;

[0013] The cuprous oxide template, tin tetrachloride, and an aqueous solvent are mixed and reacted. The resulting reaction solution is subjected to solid-liquid separation, and the solid is collected, washed, and annealed to prepare the tin dioxide nanomaterial.

[0014] In some embodiments, the preparation of the cuprous oxide template includes:

[0015] A phase-separated dispersion is prepared by mixing water, a copper salt, and oleic acid, wherein the copper salt is located in the aqueous phase.

[0016] The phase-separated dispersion is heated to extract the divalent copper salt into the oleic acid phase and form a complex of divalent copper salt and oleic acid, thus preparing the first reaction solution;

[0017] An alkali is added to the first reaction solution to adjust the pH to 9-11.5, and then a reducing agent is added to carry out a reduction reaction to prepare the second reaction solution;

[0018] The second reaction solution is subjected to solid-liquid separation, the solid is collected and washed to prepare the cuprous oxide template.

[0019] In some of these embodiments, at least one of the following features (1) to (5) is also satisfied when preparing the cuprous oxide template:

[0020] (1) The divalent copper salts include one or more of copper sulfate, copper chloride and copper nitrate;

[0021] (2) The heating temperature of the phase-separated dispersion is 50℃~60℃;

[0022] (3) The alkali includes one or more of sodium hydroxide, potassium hydroxide, barium hydroxide, lithium hydroxide and strontium hydroxide;

[0023] (4) The reducing agent includes one or more of sodium ascorbate, formaldehyde, sodium bisulfite and ferrous sulfate;

[0024] (5) The molar ratio of the reducing agent to the divalent copper salt is (0.8 to 1.2):1.

[0025] In some embodiments, the molar ratio of the cuprous oxide template to the tin tetrachloride is 1:(0.5 to 0.9).

[0026] In some embodiments, the aqueous solvent includes a mixture of ethanol and an aqueous sodium chloride solution.

[0027] In some embodiments, the annealing conditions include: annealing at 450°C to 500°C for more than 3 hours;

[0028] Alternatively, annealing can be performed in air.

[0029] Optionally, the heating rate to 450℃~500℃ is 0.3~0.7℃ / min.

[0030] In a third aspect, this application provides a gas sensor, including a substrate and a sensing material disposed on the surface of the substrate, wherein the sensing material includes the tin dioxide nanomaterial described in the first aspect or the tin dioxide nanomaterial prepared by the preparation method described in the second aspect.

[0031] In some embodiments, the gas sensor is used for monitoring electrolyte leakage in secondary batteries; optionally, the solvent of the electrolyte includes ethyl methyl carbonate.

[0032] In some embodiments, the gas sensor further includes a heating device for heating the sensing material.

[0033] A fourth aspect of this application provides a secondary battery, including a battery module and a sensor, wherein the sensor includes the gas sensor described in the third aspect.

[0034] In some embodiments, the battery module includes an electrolyte; optionally, the solvent of the electrolyte includes ethyl methyl carbonate.

[0035] A fifth aspect of this application provides an electrical device comprising the secondary battery described in the fourth aspect.

[0036] Invention Effects

[0037] The aforementioned tin dioxide nanomaterials exhibit high sensitivity and selectivity to EMC (Electromagnetic Complex) characteristic gases in electrolytes, enabling them to monitor electrolyte leaks and provide rapid early warning responses. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of a secondary battery according to one embodiment of this application;

[0039] Figure 2 for Figure 1 An exploded view of a secondary battery according to an embodiment of this application is shown.

[0040] Figure 3 This is a schematic diagram of a battery module according to one embodiment of this application;

[0041] Figure 4This is a schematic diagram of a battery pack according to one embodiment of this application;

[0042] Figure 5 for Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown;

[0043] Figure 6 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to an embodiment of this application.

[0044] Figure 7 This is a schematic diagram of the reaction process for preparing the cuprous oxide template according to one embodiment of this application;

[0045] Figure 8 Scanning electron microscope (SEM) images of the Cu2O templates prepared in Examples 1-2 and Comparative Example 1, and the tin dioxide cubic nanocrystals prepared in Example 1;

[0046] Figure 9 Transmission electron microscopy images of the tin dioxide nanoboxes prepared in Examples 1-2;

[0047] Figure 10 (a) XRD pattern and (b) N2 adsorption / desorption isotherm of the SnO2 cubic nanocrystal prepared in Example 1;

[0048] Figure 11 The following are gas-sensitive tests of the SnO2 cubic nanocrystals prepared in Example 1, including (a) response value test to 20 ppm EMC; (b) response value test to 10 ppb EMC; (c) response stability test; (d) response time test; (e) characteristic gas selectivity test; and (f) performance degradation test.

[0049] Figure 12 Gas-sensitive tests were performed on the SnO2 nanoboxes prepared in Example 2 and Comparative Example 1, where (a) was a characteristic gas selectivity test of the concave octahedral nanobox of Example 2; and (b) was a characteristic gas selectivity test of the dodecahedral nanobox of Comparative Example 1.

[0050] Explanation of reference numerals in the attached figures:

[0051] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Secondary battery; 51 Housing; 52 Electrode assembly; 53 Cover plate; 6 Electrical device. Detailed Implementation

[0052] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the tin dioxide nanomaterials, their preparation methods, gas sensors, secondary batteries, and power devices of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0053] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0054] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0055] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0056] Unless otherwise specified, all steps in this application may 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 it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0057] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0058] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0059] Compared to other types of sensors, gas sensors have advantages such as the ability to respond to changes in gas concentration, low cost, and small size. However, traditional gas sensors have poor selectivity in their gas response, and the battery pack or vehicle interior environment is complex with many interfering gases. How to achieve a highly selective response to the electrolyte still requires further research.

[0060] Some examples of this application provide a tin dioxide nanomaterial, characterized in that the tin dioxide nanomaterial is a hollow nanobox, the nanobox comprising N planar polygons, where N≤10.

[0061] The aforementioned tin dioxide nanomaterials in this specific form exhibit highly selective and sensitive responses to characteristic gases in battery electrolytes, such as EMC. Furthermore, the required temperature for the response is low. In addition, these tin dioxide nanomaterials demonstrate excellent long-term stability, better meeting the demands of application production.

[0062] Understandably, the number N of planar polygons contained in the nanobox is a positive integer, including but not limited to: 4, 5, 6, 7, 8, 9, and 10. Further, 5 ≤ N ≤ 9. Even further, 5 ≤ N ≤ 7. Reasonably controlling the number of planar polygons N can optimize the material's selectivity and response sensitivity. Additionally, it is understood that the nanobox may contain curved surfaces, such as irregular planes or curved surfaces with concave or convex shapes on a hexahedron (cube), octahedron, or similar polyhedron.

[0063] In some examples, the nanoboxes are hexahedral in shape. Understandably, a hexahedron is a spatial shape with six faces, and is generally classified into three types: cuboid, parallelepiped, and irregular hexahedron. A cuboid, also known as a rectangular prism, is a right quadrangular prism with a rectangular base, consisting of six faces with opposite faces having equal areas. A cube, also known as a cubic prism, is a special type of cuboid where all six faces are squares.

[0064] In some of these examples, the side length of any planar polygon of the nanobox is 200 nm to 450 nm.

[0065] In some of these examples, the wall thickness of any planar polygon of the nanobox is 5 nm to 30 nm.

[0066] In some of these examples, the tin dioxide nanomaterial has a specific surface area of ​​50–60 m². 2 / g. Specifically, the specific surface area of ​​the tin dioxide nanomaterial includes, but is not limited to, 50m². 2 / g、51m 2 / g、52m 2 / g、53m 2 / g、54m 2 / g, 54.49m 2 / g、55m 2 / g、56m 2 / g、57m 2 / g、58m 2 / g、59m 2 / g、60m 2 / g.

[0067] In some examples, the grain size of the tin dioxide nanomaterial is 3nm to 8nm. Specifically, the grain size of the tin dioxide nanomaterial includes, but is not limited to: 3nm, 4nm, 5nm, 5.2nm, 5.5nm, 6nm, 7nm, and 8nm.

[0068] Other examples of this application provide methods for preparing tin dioxide nanomaterials as described above, comprising the following steps:

[0069] Preparation of cuprous oxide template;

[0070] The cuprous oxide template, tin tetrachloride, and an aqueous solvent are mixed and reacted. The resulting reaction solution is subjected to solid-liquid separation, and the solid is collected, washed, and annealed to prepare the tin dioxide nanomaterial.

[0071] The above preparation method utilizes cuprous oxide templates to prepare tin dioxide nanomaterials, which facilitates the morphology control of the materials. The preparation process is simple, low-cost, and has low requirements for production conditions, making it easy to promote and apply.

[0072] In some of these examples, the preparation of the cuprous oxide template includes:

[0073] A phase-separated dispersion is prepared by mixing water, a copper salt, and oleic acid, wherein the copper salt is located in the aqueous phase.

[0074] The phase-separated dispersion is heated to extract the divalent copper salt into the oleic acid phase and form a complex of divalent copper salt and oleic acid, thus preparing the first reaction solution;

[0075] An alkali is added to the first reaction solution to adjust the pH to 9-11.5, and then a reducing agent is added to carry out a reduction reaction to prepare the second reaction solution;

[0076] The second reaction solution is subjected to solid-liquid separation, the solid is collected and washed to prepare the cuprous oxide template.

[0077] The above-mentioned method for preparing cuprous oxide templates, by using oleic acid as the organic phase and adjusting the pH accordingly, is beneficial to the morphological structure of the cuprous oxide template. Specifically, the pH adjusted by adding alkali includes, but is not limited to: 9, 9.5, 10, 10.5, 11, 11.3, and 11.5.

[0078] Without limitation, the reaction equations for preparing the cuprous oxide template are as follows:

[0079] Cu 2+ +2C 17 H 33 COOH (oleic acid) = Cu (C 17 H 33 COO)2+2H +

[0080]

[0081] In this process, the pH value of the reaction system is adjusted by controlling the amount of alkali. When the pH is 9 to 11.5, the generated cuprous oxide nanoparticles exhibit the desired polyhedral morphology.

[0082] Understandably, the reaction involving the cuprous oxide template, tin tetrachloride, and aqueous solvent is a coordination dissolution reaction. Tin tetrachloride reacts with the cuprous oxide template to form cuprous chloride on its surface. The cuprous chloride further reacts with chloride ions in the solution to form a soluble complex. This reaction allows tin dioxide to effectively replicate the size of the cuprous oxide template and completely dissolve the cuprous oxide, generating a hollow tin dioxide nanocrystal structure. Without limitation, the reaction equations for this process are shown below:

[0083] SnCl4+xH2O+2Cu2O=SnO2.xH2O+4CuCl

[0084] CuCl+(x-1)Cl - =[CuCl x ] 1-x .

[0085] In some of these examples, during the preparation of the cuprous oxide template, the divalent copper salt includes one or more of copper sulfate, copper chloride, and copper nitrate.

[0086] In some of these examples, during the preparation of the cuprous oxide template, the heating temperature of the phase-separated dispersion is 50°C to 60°C.

[0087] In some of these examples, the base used in the preparation of the cuprous oxide template includes one or more of sodium hydroxide, potassium hydroxide, barium hydroxide, lithium hydroxide, and strontium hydroxide.

[0088] In some of these examples, the reducing agent used in the preparation of the cuprous oxide template includes one or more of sodium ascorbate, formaldehyde, sodium bisulfite, and ferrous sulfate.

[0089] In some examples, during the preparation of the cuprous oxide template, the molar ratio of the reducing agent to the divalent copper salt is (0.8–1.2):1. Specifically, the molar ratio of the reducing agent to the divalent copper salt includes, but is not limited to: 0.8:1, 0.9:1, 1:1, 1.1:1, and 1.2:1.

[0090] In some examples, the molar ratio of the cuprous oxide template to the tin tetrachloride is 1:(0.5 to 0.9). Specifically, the molar ratio of the cuprous oxide template to the tin tetrachloride includes, but is not limited to: 1:0.5, 1:0.6, 1:0.7, 1:0.8, and 1:0.9.

[0091] In some of these examples, the aqueous solvent includes a mixture of ethanol and an aqueous solution of sodium chloride.

[0092] In some examples, the annealing conditions include heating to 450°C–500°C and annealing for at least 3 hours. Without limitation, the annealing time includes, but is not limited to, 3 hours, 5 hours, 10 hours, 15 hours, and 20 hours.

[0093] In some of these examples, annealing is performed in air.

[0094] In some of these examples, the heating rate to 450°C–500°C is 0.3–0.7°C / min.

[0095] Other examples of this application provide a gas sensor, including a substrate and a sensing material disposed on the surface of the substrate, the sensing material including tin dioxide nanomaterials as described above or tin dioxide nanomaterials prepared by the preparation method described above.

[0096] The aforementioned gas sensor, using tin dioxide nanomaterials as the sensing material, can achieve highly selective and sensitive detection of organic gas molecules, especially EMC, generated when organic solvents leak from the electrolyte. This enables monitoring of electrolyte leaks and provides rapid early warning. Furthermore, compared to other traditional methods for identifying organic gas molecules, such as flame ionization detectors (FID), which ionize VOCs molecules with a hydrogen flame and then detect them using electrodes, or photoionization detectors (PID), which ionize gas molecules using a high-energy electrodeless ultraviolet lamp, this gas sensor can be integrated with the battery for in-situ detection, simplifying the detection process, improving detection efficiency, and providing timely and rapid early warning at the first sign of an electrolyte leak, reducing the probability of accidents.

[0097] In some examples, the gas sensor is used for monitoring electrolyte leakage in secondary batteries. Further, the solvent for the electrolyte includes ethyl methyl carbonate.

[0098] Furthermore, the sensing material requires a specific temperature to achieve a response; therefore, in some examples, the gas sensor further includes a heating device for heating the sensing material. Without limitation, the substrate includes opposing first and second surfaces, with the sensing material disposed on the first surface and the heating device disposed on the second surface. The sensing material has a low response temperature. Without limitation, the response temperature is approximately 130°C. The heating device can be, for example, a ruthenium oxide heating coating; ruthenium oxide is an electronically heating material that generates heat through lattice vibrations caused by electron transport. The substrate can be, for example, an electrode sheet, an alumina ceramic sheet, etc.

[0099] Without limitation, the sensing material can be dispersed into a paste using a solvent, coated onto the surface of a substrate, and then aged to improve the bonding performance between the sensing material and the substrate. Finally, it can be soldered and encapsulated to obtain a gas sensor. The aging temperature can be, for example, 200°C to 500°C, and the solvent can be, for example, one or both of ethanol and water.

[0100] Another example of this application provides the application of the gas sensor described above in the monitoring of electrolyte leakage in secondary batteries.

[0101] In one example, the solvent for the electrolyte includes ethyl methyl carbonate.

[0102] Another example of this application provides a secondary battery, including a battery module and a sensor, the sensor including a gas sensor as described above.

[0103] In one example, the battery module includes an electrolyte. Further, the solvent of the electrolyte includes ethyl methyl carbonate.

[0104] The secondary battery, battery module, battery pack, and power-consuming device of this application will be described below with appropriate reference to the accompanying drawings.

[0105] In one embodiment of this application, a secondary battery is provided.

[0106] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0107] Positive electrode sheet

[0108] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including the positive electrode active material of the first aspect of this application.

[0109] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0110] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material on the polymer material substrate. The metal material includes, but is not limited to, aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. The polymer material substrate may be (e.g., polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0111] In some embodiments, the positive electrode active material may comprise positive electrode active materials known in the art for use in batteries. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites. The positive electrode active material accounts for 80-100% by weight in the positive electrode film, based on the total weight of the positive electrode film.

[0112] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a terpolymer of PVDF-tetrafluoroethylene-propylene, a terpolymer of PVDF-hexafluoropropylene-tetrafluoroethylene, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorinated acrylate resin. The binder constitutes 0-20% by weight of the positive electrode film layer, based on the total weight of the positive electrode film layer.

[0113] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The conductive agent accounts for 0-20% by weight of the positive electrode film, based on the total weight of the positive electrode film.

[0114] In some embodiments, the positive electrode sheet can be prepared by dispersing the components used to prepare the positive electrode sheet, such as the positive electrode active material, conductive agent, binder, and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry, wherein the solid content of the positive electrode slurry is 40-80 wt%, and the viscosity at room temperature is adjusted to 5000-25000 mPa·s. The positive electrode slurry is coated on the surface of the positive electrode current collector, dried, and then cold-pressed using a cold rolling mill to form the positive electrode sheet; the areal density of the positive electrode powder coating is 150-350 mg / m³. 2 The compaction density of the positive electrode sheet is 3.0-3.6 g / cm³. 3 The concentration can be selected as 3.3-3.5 g / cm³. 3 The formula for calculating the compaction density is as follows:

[0115] Compacted density = Coated surface density / (Extreme electrode thickness after extrusion - Current collector thickness).

[0116] Negative electrode sheet

[0117] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0118] As an example, the negative electrode current collector has two surfaces opposite each other in its own 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.

[0119] 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 material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material on the polymer material substrate. The metal material includes, but is not limited to, copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc., and the polymer material substrate includes, but is not limited to, polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0120] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an 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, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more. The weight percentage of the negative electrode active material in the negative electrode film layer is 70-100% by weight, based on the total weight of the negative electrode film layer.

[0121] In some embodiments, the negative electrode film layer may optionally 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). The binder accounts for 0-30% by weight of the negative electrode film layer, based on the total weight of the negative electrode film layer.

[0122] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The conductive agent accounts for 0-20% by weight of the negative electrode film, based on the total weight of the negative electrode film.

[0123] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)). The other additives constitute 0-15% by weight of the negative electrode film, based on the total weight of the negative electrode film.

[0124] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder, and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry, wherein the solid content of the negative electrode slurry is 30-70 wt%, and the viscosity at room temperature is adjusted to 2000-10000 mPa·s; the obtained negative electrode slurry is coated onto a negative electrode current collector, and after a drying process, it is cold-pressed, for example, by rollers, to obtain the negative electrode sheet. The areal density of the negative electrode powder coating is 75-220 mg / m³. 2 The compacted density of the negative electrode sheet is 1.2-2.0 g / m³. 3 .

[0125] electrolytes

[0126] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0127] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0128] In some embodiments, the electrolyte salt may 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 difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP). The concentration of the electrolyte salt is typically 0.5-5 mol / L.

[0129] In some embodiments, the solvent of the electrolyte includes ethyl methyl carbonate (EMC). Without limitation, the solvent of the electrolyte may also include one or more of the following: fluoroethylene carbonate (FEC), ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl carbonate (BC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), and 1,4-butyrolactone (GBL). Additionally, the solvent of the electrolyte may also include one or more of the following: sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0130] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0131] Separating membrane

[0132] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0133] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0134] In some embodiments, the thickness of the isolation membrane is 6-40 μm, optionally 12-20 μm.

[0135] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0136] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0137] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0138] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 This is an example of a square-structured secondary battery 5.

[0139] In some implementations, refer to Figure 2 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator can be formed into an electrode assembly 52 using a winding or stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0140] In some implementations, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0141] Figure 3 This is battery module 4, used as an example. (See reference...) Figure 3 In battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0142] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0143] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0144] Figure 4 and Figure 5 This is battery pack 1 as an example. (See reference...) Figure 4 and Figure 5The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0145] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack 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 (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0146] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0147] Figure 6 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0148] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0149] Example

[0150] To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the application will be further described in detail below with reference to embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its applications. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0151] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0152] Example 1

[0153] This embodiment provides a method for preparing cubic tin dioxide nanomaterials, and the reaction process is illustrated in the schematic diagram below. Figure 7 As shown, the steps are as follows:

[0154] (1) Preparation of Cu2O cubic template:

[0155] A 250 mL round-bottom flask was used to collect approximately 70 mL of deionized water, 10 mL of 0.1 M copper sulfate aqueous solution, and 5 mL of oleic acid. It was clearly observed that the solution separated into two parts: the oleic acid phase on top and the aqueous phase on the bottom. The mixture was heated and stirred until the temperature reached approximately 50°C–60°C. When the aqueous phase became colorless and the oil phase turned blue, 18.5 mL of 1 M NaOH aqueous solution was quickly added to the mixture in the flask to adjust the pH to 11.3. After stirring for 15 minutes, the solution turned deep blue, exhibiting a water-in-oil emulsion state. 10 mL of 0.1 M sodium ascorbate aqueous solution was added, and the solution quickly turned yellow. After stirring for another hour, the mixture was removed and centrifuged (10000 rpm). The resulting solid was washed three times each with deionized water, ethanol, and n-hexane to prepare a Cu₂O cubic template.

[0156] (2) Preparation of SnO2 cubic nanoboxes:

[0157] 0.02 g (0.14 mmol) of Cu₂O cubic template was weighed and dispersed in 40 mL of ethanol and 1.2 mL of sodium chloride aqueous solution (1 g / mL). 2 mM SnCl₄ ethanol solution (40 mL) was added dropwise to the dispersion. The mixture was stirred at room temperature, and the suspension was observed to gradually change from orange-red to milky white. After centrifugation, the resulting solid was washed three times each with deionized water and ethanol. The prepared powder was slowly heated to 500 °C at a heating rate of 0.5 °C / min and annealed in air for 3 hours to finally obtain SnO₂ cubic nanocrystals.

[0158] The main difference between the tin dioxide nanomaterials of Example 2 and Comparative Example 1 and the cubic tin dioxide nanomaterials of Example 1 lies in the morphology of the nanoboxes. In Example 2, the preparation process was the same as in Example 1, except that the amount of 1M NaOH aqueous solution added in step (1) was adjusted to 13 mL to achieve a pH of 9.0, resulting in tin dioxide nanoboxes with a concave octahedral shape. In Comparative Example 1, the preparation process was the same as in Example 1, except that the amount of 1M NaOH aqueous solution added in step (1) was adjusted to 10.5 mL to achieve a pH of 8.2, resulting in tin dioxide nanomaterials with a dodecahedral shape. A schematic diagram of the reaction process is shown below. Figure 7 As shown.

[0159] Test example:

[0160] (1) Morphology testing of SnO2 nanomaterials

[0161] Figure 8 Scanning electron microscope (SEM) images of the Cu₂O templates prepared in Examples 1-2 and Comparative Example 1, and the tin dioxide cubic nanocrystal prepared in Example 1, wherein (a) is the Cu₂O cubic template prepared in Example 1, (b) is the Cu₂O concave octahedral template prepared in Example 2, (c) is the Cu₂O dodecahedral template prepared in Comparative Example 1, and (d) is the SEM image of the SnO₂ cubic nanocrystal prepared in Example 1. Figure 8 It is evident that the Cu₂O cubic template can be dissolved in the form of a complex via a coordination dissolution reaction, while its morphology is completely preserved to generate SnO₂ cubic nanoboxes. Specifically, the SnO₂ cubic nanoboxes prepared in Example 1 are cubic, the SnO₂ nanoboxes prepared in Example 2 are concave octahedral, and the SnO₂ nanoboxes prepared in Comparative Example 1 are dodecahedral. Furthermore, the side lengths of the SnO₂ cubic nanoboxes prepared in Example 1 are concentrated in the range of 200 nm to 450 nm, and the wall thickness is approximately 5 nm to 30 nm.

[0162] Figure 9 Transmission electron microscopy (TEM) images of the SnO2 nanoboxes prepared in Examples 1-2, wherein (a) is the SnO2 cubic nanobox prepared in Example 1, and (b) is the SnO2 concave octahedral box prepared in Example 2.

[0163] Figure 10 The images show (a) XRD pattern and (b) N2 adsorption / desorption isotherm of the SnO2 cubic nanocrystals prepared in Example 1. Figure 10 It can be seen that the prepared SnO2 cubic nanocrystals exist in a polycrystalline form and have a small grain size (approximately). (Calculated from XRD patterns using Jade software), the nanobox structure gives it a rich specific surface area (approximately 54.49 m²). 2 / g), which is beneficial for gas adsorption-desorption.

[0164] (2) Gas Sensitivity Test

[0165] Response value, response speed, selectivity, and stability are important parameters for evaluating gas sensors.

[0166] The SnO2 cubic nanocrystals prepared in Example 1 were dispersed in ethanol and uniformly coated onto one side of an alumina ceramic sheet by repeated dropwise addition. A ruthenium oxide heating material was printed onto the opposite side of the alumina ceramic sheet to obtain a preform. The preform was aged at 300°C to improve the bonding performance between the material and the electrode sheet. The aged electrode sheet was then welded and encapsulated to obtain a gas-sensitive sensing element.

[0167] Testing Procedure: First, the packaged device underwent an aging process. Test gas of appropriate concentration and dry air as background gas were purchased and connected to the gas testing platform (Wuhan Platinum Sensing Technology Co., Ltd., BN2914 high-throughput gas-sensitive performance testing platform). A suitable voltage was adjusted (approximately 150℃ at 4V in this experiment) to obtain the appropriate device operating temperature. Dry air was introduced to maintain the total gas flow rate in the test chamber at 500mL / min. After the material current stabilized, the flow rates of the test gas and background gas were adjusted to change the concentration of the test gas in the chamber. The changes in the current signal were then observed and acquired using a semiconductor analyzer. The test gas was introduced for a certain period and then disconnected, while dry air was introduced again until the device recovered. The waste gas in the chamber was post-treated through a dedicated waste treatment pipeline.

[0168] Test results are as follows Figure 11 As shown, the gas-sensitive sensing element described above has an EMC response value of 13.9 for 20 ppm, and exhibits good linear correlation in the range of 1-20 ppm. Figure 11 (a)). The EMC response value for values ​​as low as 10 ppb is 0.2946 ( Figure 11 (b) This response value far exceeds the test requirements for battery pack electrolyte leakage, demonstrating the sensor's sensitivity to EMC, i.e., a lower detection limit. The response speed represents the gas adsorption / desorption capacity of the material surface; the faster the response, the stronger the gas adsorption capacity, and the faster the gas sensor can provide early warning. The aforementioned gas-sensitive sensing element exhibited high stability during five sets of 10ppm EMC tests. Figure 11 (c)) and it only takes 180 seconds to complete 90% of the response, providing ample time to prevent further electrolyte leakage and combustion. Figure 11 (d) Selectivity represents the sensor's ability to detect the target gas in the presence of interfering gases. At the optimal operating temperature of the tin dioxide nanobox, tests were conducted on other typical gases commonly found in battery packs (DMC, ethanol, acetone, methane, carbon monoxide, carbon dioxide; except for carbon dioxide at 20 ppm, the other gases were all 10 ppm). It was found that the sensor's response to these other gases was significantly lower than that to the characteristic gas EMC. Figure 11 (e) confirms that this gas-sensitive material has good anti-interference ability during leakage detection and can effectively cope with the complex gas environment inside the lithium battery during detection. Stability refers to whether the sensor's response to the target gas can be maintained at a high level over a considerable period of time. Good long-term stability is a key performance indicator for EMC sensors. Under laboratory test conditions, the device showed almost no performance degradation within six weeks. Figure 11 (f)) and the material is tightly bonded to the electrode sheet and is not easy to fall off.

[0169] The material properties of Example 2 and Comparative Example 1 were tested using the same gas-sensitive testing procedure as in Example 1. The selectivity test results of the concave octahedral nanobox of Example 2 and the dodecahedral nanobox of Comparative Example 1 are as follows: Figure 12 As shown in (a) and (b), the test results show that the dodecahedral nanobox of Comparative Example 1 has no selectivity for EMC, and the response value is reduced to 3.12109. Although the selectivity and response value of the concave octahedral nanobox of Example 2 are lower than those of Example 1, it still has a certain selectivity for EMC compared with Comparative Example 1, and the response value is higher than that of Comparative Example 1.

[0170] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A secondary battery, characterized in that, The device includes a battery module and a sensor, the sensor including a gas sensor, the gas sensor including a substrate and a sensing material disposed on the surface of the substrate, the sensing material including tin dioxide nanomaterials; the battery module including an electrolyte; the solvent of the electrolyte including methyl ethyl carbonate; The tin dioxide nanomaterial is a hollow nanobox, which comprises N planar polygons, where N≤10.

2. The secondary battery according to claim 1, characterized in that, 5≤N≤9。 3. The secondary battery according to claim 2, characterized in that, 5≤N≤7。 4. The secondary battery according to any one of claims 1 to 3, characterized in that, The side length of any planar polygon of the nanobox is 200nm~450nm.

5. The secondary battery according to any one of claims 1 to 3, characterized in that, The wall thickness of any planar polygon of the nanobox is 5nm~30nm.

6. The secondary battery according to any one of claims 1 to 3, characterized in that, The specific surface area of ​​the tin dioxide nanomaterial is 50~60m². 2 / g.

7. The secondary battery according to any one of claims 1 to 3, characterized in that, The tin dioxide nanomaterial has a grain size of 3nm to 8nm.

8. The secondary battery according to any one of claims 1 to 3, characterized in that, The preparation method of the tin dioxide nanomaterial includes the following steps: Preparation of cuprous oxide template; The cuprous oxide template, tin tetrachloride, and an aqueous solvent are mixed and reacted. The resulting reaction solution is subjected to solid-liquid separation, and the solid is collected, washed, and annealed to prepare the tin dioxide nanomaterial.

9. The secondary battery according to claim 8, characterized in that, The preparation of the cuprous oxide template includes: A phase-separated dispersion was prepared by mixing water, a copper salt, and oleic acid, wherein the copper salt was located in the aqueous phase. The phase-separated dispersion is heated to extract the divalent copper salt into the oleic acid phase and form a complex of divalent copper salt and oleic acid, thus preparing the first reaction solution. An alkali is added to the first reaction solution to adjust the pH to 9-11.5, and then a reducing agent is added to carry out a reduction reaction to prepare the second reaction solution. The second reaction solution was subjected to solid-liquid separation, the solid was collected and washed to prepare the cuprous oxide template.

10. The secondary battery according to claim 9, characterized in that, When preparing the cuprous oxide template, at least one of the following characteristics (1) to (5) must also be satisfied: (1) The divalent copper salt includes one or more of copper sulfate, copper chloride and copper nitrate; (2) The heating temperature of the phase-separated dispersion is 50℃~60℃; (3) The alkali includes one or more of sodium hydroxide, potassium hydroxide, barium hydroxide, lithium hydroxide and strontium hydroxide; (4) The reducing agent includes one or more of sodium ascorbate, formaldehyde, sodium bisulfite and ferrous sulfate; (5) The molar ratio of the reducing agent to the divalent copper salt is (0.8~1.2):

1.

11. The secondary battery according to claim 9 or 10, characterized in that, The molar ratio of the cuprous oxide template to the tin tetrachloride is 1:(0.5~0.9).

12. The secondary battery according to claim 9 or 10, characterized in that, The aqueous solvent includes a mixture of ethanol and an aqueous solution of sodium chloride.

13. The secondary battery according to claim 9 or 10, characterized in that, The annealing conditions include: heating to 450℃~500℃ and annealing for more than 3 hours.

14. The secondary battery according to claim 13, characterized in that, Annealing is carried out in air.

15. The secondary battery according to claim 13, characterized in that, The heating rate to 450℃~500℃ is 0.3~0.7℃ / min.

16. The secondary battery according to any one of claims 1 to 3, characterized in that, The gas sensor also includes a heating device for heating the sensing material.

17. An electrical device, characterized in that, Includes the secondary battery as described in any one of claims 1 to 16.

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