Electrolyte, secondary battery, and electrical apparatus

Abstract

An electrolyte, a secondary battery, and an electrical apparatus. The electrolyte comprises an organic solvent and inorganic nanoparticles. The inorganic nanoparticles are suspended and dispersed in the organic solvent. The electrolyte has short sustainable combustion time and high oxidation voltage. The battery has a long thermal runaway time and excellent cycling stability.

Description

Electrolyte, secondary battery and electrical device

[0001] Cross-references

[0002] This application claims priority to Chinese Patent Application No. 202311413065.4, filed on October 27, 2023, entitled “Electrolyte, Secondary Battery and Electrical Device,” which is incorporated herein by reference in its entirety. Technical Field

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

[0004] In recent years, secondary batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.

[0005] Secondary batteries in the prior art often use non-aqueous solvents as electrolyte solvents, which are prone to fire, explosion and other safety accidents caused by electrolyte combustion. Therefore, the existing electrolytes still need to be improved.

[0006] Summary of the Invention

[0007] The present application is made in view of the above-mentioned problems, and its purpose is to provide an electrolyte that has reduced flammability at high temperatures and strong oxidation resistance, which can effectively prolong the thermal runaway time of the battery and improve the safety performance of the battery.

[0008] A first aspect of the present application provides an electrolyte solution comprising: an organic solvent and inorganic nanoparticles, wherein the inorganic nanoparticles are suspended and dispersed in the organic solvent.

[0009] Electrolytes using organic molecules as solvents often offer superior electrochemical performance in secondary batteries and are currently the mainstream electrolyte system for secondary batteries. However, organic solvents in these electrolytes have poor thermal and chemical stability, are prone to combustion under overheating conditions, and are susceptible to oxidative decomposition at the positive electrode, thus affecting the battery's safety and cycling stability. When inorganic nanoparticles are included in the electrolyte, their nanoscale size, large specific surface area and surface energy, and their surface charge often allow for adsorption and charge interactions between the nanoparticles and the organic solvent. This allows the inorganic nanoparticles to overcome gravity and become suspended and dispersed in the electrolyte, acting as a "binding" for the organic solvent, reducing the solvent's volatility. This improves the electrolyte's thermal stability, reduces its sustained combustion time, and thus prolongs the battery's thermal runaway time. Furthermore, the presence of inorganic nanoparticles in the electrolyte can reduce the free solvent content, improve the electrolyte's antioxidant capacity, mitigate oxidative decomposition at the positive electrode, and increase the oxidation voltage of the secondary battery, thereby improving the battery's electrochemical performance. Inorganic nanoparticles have good thermal stability and electrochemical stability. The inorganic nanoparticles in the electrolyte can exist stably during the cycle and will not undergo redox decomposition reactions. They can reduce the flammability of the electrolyte at high temperatures throughout the life cycle of the battery and improve the safety performance and cycle stability of the battery.

[0010] In any embodiment, the Dv50 of the inorganic nanoparticles is 50 nm to 500 nm, optionally 100 nm to 250 nm.

[0011] When the Dv50 of inorganic nanoparticles is 50nm~500nm, they can be suspended and dispersed in the electrolyte, and can play the role of "binding" organic solvents, greatly reducing the free solvent content in the electrolyte, thereby reducing the sustainable combustion time of the electrolyte, extending the thermal runaway time of the battery, increasing the oxidation voltage of the battery, and improving the battery's safety performance and cycle stability.

[0012] In any embodiment, the inorganic nanoparticles include at least one of metal silicates, metal nitrides, metal fluorides, and metal oxides.

[0013] In any embodiment, the inorganic nanoparticles include at least one of lithium silicate, lithium nitride, lithium fluoride, and aluminum oxide.

[0014] In any embodiment, in the electrolyte, the mass ratio of the inorganic nanoparticles to the organic solvent is 1:1.5 to 1:9, and can be optionally 1:3 to 1:6.

[0015] When the mass ratio of inorganic nanoparticles to organic solvents is 1:1.5 to 1:9, the inorganic nanoparticles can be suspended and dispersed in the electrolyte, and can also play a "binding" role on the organic solvent, so that the free solvent content in the electrolyte is greatly reduced, thereby reducing the sustainable combustion time of the electrolyte, prolonging the thermal runaway time of the battery, increasing the oxidation voltage of the battery, and improving the battery's safety performance and cycle stability.

[0016] In any embodiment, the organic solvent includes at least one of a carbonate solvent, an ether solvent, and a carboxylate solvent.

[0017] In any embodiment, the carbonate solvent includes one or more of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, and butylene carbonate; the ether solvent includes one or more of 1,2-dimethoxypropane, dimethoxymethane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, and dioxolane; the carboxylate solvent includes one or more of methyl formate, ethyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, and methyl butyrate.

[0018] In any embodiment, the electrolyte further includes a stabilizer, and the stabilizer includes a surfactant.

[0019] In organic solvents, surfactants can combine with inorganic nanoparticles through hydrogen bonds, ionic bonds, etc. through their own polar hydrophilic groups, while non-polar hydrocarbon chains extend into the organic solvent, thereby reducing the aggregation of inorganic nanoparticles and making the inorganic nanoparticles stably suspended and dispersed in the organic solvent, thereby reducing the sustainable combustion time of the electrolyte, extending the thermal runaway time of the battery, increasing the oxidation voltage of the battery, and improving the battery's safety performance and cycle stability.

[0020] In any embodiment, the surfactant includes one or more of sodium carboxymethyl cellulose, polysorbate, sodium fatty alcohol polyoxyethylene ether sulfate, sodium dodecyl sulfonate, sodium lauryl sulfate, and sodium dodecylbenzene sulfonate.

[0021] In any embodiment, in the electrolyte, the mass ratio of the stabilizer to the inorganic nanoparticles is 1:100 to 3:100, and can be optionally 2:100 to 3:100.

[0022] When the mass ratio of the stabilizer to the inorganic nanoparticles is 1:100 to 3:100, the stabilizer has a good dispersing effect on the inorganic nanoparticles, so that the inorganic nanoparticles can be stably suspended and dispersed in the electrolyte, thereby reducing the sustainable combustion time of the electrolyte, extending the thermal runaway time of the battery, increasing the oxidation voltage of the battery, and improving the safety performance and cycle stability of the battery.

[0023] A second aspect of the present application provides a secondary battery comprising the electrolyte according to any embodiment.

[0024] The third aspect of the present application further provides an electrical device comprising the secondary battery of the second aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG1 is a schematic diagram of a secondary battery according to an embodiment of the present application;

[0026] FIG2 is an exploded view of the secondary battery according to one embodiment of the present application shown in FIG1 ;

[0027] FIG3 is a schematic diagram of a battery module according to an embodiment of the present application;

[0028] FIG4 is a schematic diagram of a battery pack according to an embodiment of the present application;

[0029] FIG5 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG4 ;

[0030] FIG6 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.

[0031] Explanation of reference numerals: 1 battery pack; 2 upper case; 3 lower case; 4 battery module; 5 secondary battery; 51 housing; 52 electrode assembly; 53 cover plate. DETAILED DESCRIPTION

[0032] Below, the embodiments of the electrolyte, secondary battery and electrical device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0033] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0034] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0035] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0036] Unless otherwise specified, all steps of the present 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 may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0037] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0038] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: 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).

[0039] Non-aqueous electrolytes are generally composed of electrolyte salts and organic solvents, which significantly impact battery safety, cycle life, and high- and low-temperature performance. Organic solvents in existing electrolyte compositions often suffer from low boiling points, high volatility, and flammability. When the battery is exposed to high temperatures or short circuits, they are prone to fires, explosions, and other safety incidents caused by electrolyte combustion. Furthermore, organic solvents in electrolytes are relatively unstable and easily oxidized and decomposed at the positive electrode, consuming lithium salts and subsequently deteriorating the battery's impedance and cycle performance.

[0040] [Electrolyte]

[0041] Based on this, the present application proposes an electrolyte, comprising: an organic solvent, and inorganic nanoparticles, wherein the inorganic nanoparticles are suspended and dispersed in the organic solvent.

[0042] As used herein, the term "inorganic nanoparticles" refers to particles including inorganic salts and inorganic non-metallic materials, wherein the particles are nanometer-sized in at least one dimension.

[0043] In some embodiments, inorganic nanoparticles refer to particles whose sizes in three dimensions are all within 1000 nm.

[0044] Electrolytes using organic molecules as solvents often result in superior electrochemical performance in secondary batteries and are currently the mainstream electrolyte system for secondary batteries. However, the organic solvents in these electrolytes suffer from poor thermal and chemical stability, are prone to combustion under overheating conditions, and are susceptible to oxidative decomposition at the positive electrode, thus affecting the battery's safety and cycling performance. When inorganic nanoparticles are included in the electrolyte, their nanoscale size, large specific surface area and surface energy, and their surface charge often enable adsorption and charge interactions between the nanoparticles and the organic solvent. Furthermore, the inorganic nanoparticles are lightweight, enabling them to overcome gravity through interactions with the solvent, allowing them to remain suspended and dispersed in the electrolyte. The large specific surface area of ​​the inorganic nanoparticles effectively "binds" the organic solvent, significantly reducing the free solvent content in the electrolyte and raising the energy barrier required for solvent combustion. This improves the electrolyte's thermal stability, reduces the sustained combustion time, and thus prolongs the battery's thermal runaway time.

[0045] At the same time, inorganic nanoparticles suspended in the electrolyte can also reduce the free solvent content, improve the electrolyte's antioxidant capacity, reduce the electrolyte's oxidative decomposition at the positive electrode, increase the secondary battery's oxidation voltage, and improve the battery's electrochemical performance. Inorganic nanoparticles have excellent thermal and electrochemical stability. Inorganic nanoparticles in the electrolyte can remain stable during the cycle and will not undergo redox decomposition reactions. They can reduce the electrolyte's flammability at high temperatures throughout the battery's life cycle, improving the battery's safety and cycling stability.

[0046] In some embodiments, the organic solvent includes at least one of a carbonate solvent, an ether solvent, and a carboxylate solvent.

[0047] In some embodiments, the carbonate solvent includes one or more of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, and butylene carbonate; the ether solvent includes one or more of 1,2-dimethoxypropane, dimethoxymethane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, and dioxolane; the carboxylate solvent includes one or more of methyl formate, ethyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, and methyl butyrate.

[0048] In some embodiments, the Dv50 of the inorganic nanoparticles is 50 nm to 500 nm. In some embodiments, the Dv50 of the inorganic nanoparticles is 100 nm to 250 nm.

[0049] As used herein, the term "Dv50" refers to the particle size corresponding to the cumulative volume distribution number of particles reaching 50% in a particle size distribution curve.

[0050] In this application, the Dv50 of the inorganic nanoparticles can be tested by methods known in the art. As an example, referring to GB / T 19077-2016 particle size distribution laser diffraction method, 0.1g to 0.13g of inorganic nanoparticles are weighed in a 50ml beaker, and 5g of anhydrous ethanol is weighed and added to the beaker containing the inorganic nanoparticles. A stirring rod with a length of about 2.5mm is placed and sealed with plastic wrap. The sample is placed in an ultrasonic machine for 5 minutes, transferred to a magnetic stirrer and stirred at a speed of 500r / min for more than 20 minutes. Two samples are taken from each batch of products for testing. The measurement is performed using a laser particle size analyzer, such as the Mastersizer 2000E laser particle size analyzer of Malvern Instruments Co., Ltd. in the UK.

[0051] In some embodiments, the Dv50 of the inorganic nanoparticles is 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, or any range therebetween.

[0052] When the Dv50 of inorganic nanoparticles is within the above range, they can be stably suspended and dispersed in the electrolyte, playing the role of "binding" the organic solvent, significantly reducing the free solvent content in the electrolyte, thereby reducing the sustainable combustion time of the electrolyte, extending the thermal runaway time of the battery, increasing the oxidation voltage of the battery, and improving the battery's safety performance and cycle stability.

[0053] In some embodiments, the inorganic nanoparticles include at least one of metal silicates, metal nitrides, metal fluorides, and metal oxides.

[0054] In some embodiments, the inorganic nanoparticles include at least one of lithium silicate, lithium nitride, lithium fluoride, and aluminum oxide.

[0055] These inorganic nanoparticles can be stably suspended in the electrolyte and, through their interaction with the organic solvent, significantly improve the electrolyte's flame retardancy and safety. Furthermore, these inorganic nanoparticles exhibit strong electrochemical stability and can persist stably during cycling, reducing the oxidative decomposition of the organic solvent in the electrolyte under high voltage and improving the battery's cycling stability.

[0056] In some embodiments, the mass ratio of the inorganic nanoparticles to the organic solvent in the electrolyte is 1:1.5 to 1:9. In some embodiments, the mass ratio of the inorganic nanoparticles to the organic solvent in the electrolyte is 1:3 to 1:6.

[0057] In some embodiments, in the electrolyte, the mass ratio of the inorganic nanoparticles to the organic solvent is 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:8.5, 1:9 or any range therebetween.

[0058] When the mass ratio of inorganic nanoparticles to organic solvents is within the above range, the inorganic nanoparticles can not only be stably suspended and dispersed in the electrolyte, but also fully exert the "binding" effect of the inorganic nanoparticles on the organic solvent, so that the free solvent content in the electrolyte is greatly reduced, thereby reducing the sustainable combustion time of the electrolyte, extending the thermal runaway time of the battery, increasing the oxidation voltage of the battery, and improving the battery's safety performance and cycle stability.

[0059] In some embodiments, the electrolyte further includes a stabilizer, and the stabilizer includes a surfactant.

[0060] As used herein, the term "surfactant" refers to a substance having a molecular structure with a hydrophilic polar group at one end and a hydrophobic non-polar group at the other end.

[0061] In organic solvents, surfactants can combine with inorganic nanoparticles through hydrogen bonds, ionic bonds, etc. through their own polar hydrophilic groups, while non-polar groups extend into the organic solvent, thereby improving the dispersion stability of inorganic nanoparticles in organic solvents, thereby reducing the aggregation of inorganic nanoparticles, and increasing the content and dispersion stability of inorganic nanoparticles in organic solvents, thereby reducing the sustainable combustion time of the electrolyte, extending the thermal runaway time of the battery, increasing the oxidation voltage of the battery, and improving the safety performance and cycle stability of the battery.

[0062] In some embodiments, the surfactant includes one or more of sodium carboxymethyl cellulose, polysorbate, sodium fatty alcohol polyoxyethylene ether sulfate, sodium dodecyl sulfonate, sodium lauryl sulfate, and sodium dodecylbenzene sulfonate.

[0063] In some embodiments, in the electrolyte, the mass ratio of the stabilizer to the inorganic nanoparticles is 1:100 to 3:100. In some embodiments, in the electrolyte, the mass ratio of the stabilizer to the inorganic nanoparticles is 2:100 to 3:100.

[0064] In some embodiments, in the electrolyte, the mass ratio of the stabilizer to the inorganic nanoparticles is 1:100, 1.5:100, 2:100, 2.5:100, 3:100, or any range therebetween.

[0065] When the mass ratio of the stabilizer to the inorganic nanoparticles is within the above range, the stabilizer has a good dispersing effect on the inorganic nanoparticles, so that the inorganic nanoparticles can be stably suspended and dispersed in the electrolyte, thereby reducing the sustainable combustion time of the electrolyte, extending the thermal runaway time of the battery, increasing the oxidation voltage of the battery, and improving the safety performance and cycle stability of the battery.

[0066] In some embodiments, the electrolyte includes an electrolyte salt. In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0067] In some embodiments, the electrolyte may further include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0068] [Positive electrode]

[0069] The positive electrode sheet generally includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes a positive electrode active material.

[0070] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0071] In some embodiments, the positive electrode 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 base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0072] In some embodiments, the positive electrode active material may adopt the positive electrode active material for batteries that is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional 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 may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and its modified compounds. Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0073] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0074] In some embodiments, the positive electrode film layer may further include a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0075] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0076] [Negative electrode]

[0077] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0078] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0079] 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 base layer and a metal layer formed on at least one surface of the polymer base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0080] In some embodiments, the negative electrode active material may be a negative electrode active material for a battery that is well known in the art. 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, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional 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.

[0081] In some embodiments, the negative electrode film layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0082] In some embodiments, the negative electrode film layer may further include a conductive agent. For example, 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.

[0083] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0084] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0085] [Isolation film]

[0086] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0087] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven 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.

[0088] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0089] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0090] 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. Alternatively, the outer packaging of the secondary battery can be a soft shell, such as a pouch-type soft shell. The soft shell can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0091] In this application, the shape of the secondary battery includes but is not limited to cylindrical, square or any other shape. For example, FIG1 shows a secondary battery 5 with a square structure as an example.

[0092] In some embodiments, referring to FIG2 , the outer package may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0093] In some embodiments, secondary batteries can be assembled into a battery module. The number of secondary batteries contained in the battery module can be one or more. The specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0094] Figure 3 shows an example battery module 4. Referring to Figure 3 , within the battery module 4, multiple secondary batteries 5 may be arranged sequentially along the length of the battery module 4. Of course, any other arrangement is also possible. Furthermore, the multiple secondary batteries 5 may be secured together using fasteners.

[0095] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of secondary batteries 5 are received in the receiving space.

[0096] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0097] Figures 4 and 5 illustrate an example battery pack 1. Referring to Figures 4 and 5 , the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 can be placed over the lower case 3 to form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0098] The present application also provides an electric device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application. The secondary battery, battery module, or battery pack can be used as a power source for the electric device, and can also be used as an energy storage unit for the electric device. The electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as 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., but is not limited thereto.

[0099] As an electrical device, a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.

[0100] Figure 6 shows an example of an electric device. This device is 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, a battery pack or battery module can be used.

[0101] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is generally required to be lightweight and thin, and may use a secondary battery as a power source.

[0102] Example

[0103] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0104] 1. Preparation method

[0105] Example 1:

[0106] 1) Preparation of negative electrode sheet

[0107] (1) The negative electrode active material graphite, conductive carbon black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC-Na) are fully stirred and mixed in a deionized water solvent system according to a mass ratio of 95:2:2:1 to obtain a negative electrode slurry; the negative electrode slurry is evenly coated on a negative electrode current collector copper foil with a thickness of 13 μm at a coating speed of 25 m / min and a coating oven temperature of 110°C-130°C; and then the negative electrode sheet is obtained by cold pressing and slitting;

[0108] 2) Preparation of positive electrode sheet

[0109] The positive electrode active material Li(Ni 0.8 Co 0.1 Mn 0.1 )O2, conductive carbon black, and binder polyvinylidene fluoride (PVDF) are fully stirred and mixed in an N-methylpyrrolidone solvent system in a weight ratio of 96:2:2 to obtain a positive electrode slurry; the above positive electrode slurry is evenly coated on a positive electrode current collector aluminum foil with a thickness of 13 μm at a coating speed of 30 m / min; the temperature of the coating oven is 110°C-130°C, and then the positive electrode sheets are obtained through cold pressing and slitting.

[0110] 3) Preparation of electrolyte

[0111] In an argon atmosphere glove box (H2O content <0.1ppm, O2 content <0.1ppm), lithium salt lithium hexafluorophosphate LiPF6 was dissolved in a mixed system of organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (EC:EMC volume ratio of 3:7), and the concentration of lithium hexafluorophosphate LiPF6 was 1 mol / L; then inorganic nanoparticles aluminum oxide and stabilizer sodium dodecylbenzenesulfonate were added, wherein the ratio of the mass of aluminum oxide to the total mass of EC and EMC was 1:4; the ratio of the mass of the stabilizer sodium dodecylbenzenesulfonate to the mass of the inorganic nanoparticles aluminum oxide was 1:50, and the mixture was stirred evenly so that the inorganic nanoparticles aluminum oxide were stably suspended and dispersed in the electrolyte to obtain an electrolyte.

[0112] 4) Isolation film

[0113] A 9 μm polyethylene (PE) film was used as the separator.

[0114] 5) Preparation of batteries

[0115] The positive electrode sheet, the isolation film, and the composite negative electrode sheet are stacked in order, so that the isolation film is placed between the positive and negative electrode sheets to isolate the positive and negative electrode sheets. The bare battery cell is wound and the tabs are welded. The bare battery cell is placed in an outer packaging aluminum shell, dried at 85°C for 6 hours, and then vacuum packaged, allowed to stand, formed, and shaped to obtain the secondary battery product of Example 1.

[0116] The preparation methods of the batteries of Examples 2-4 are similar to those of the battery of Example 1, but the types of inorganic nanoparticles are adjusted, and Dv50 changes accordingly. The specific parameters are shown in Table 1.

[0117] The preparation methods of the batteries of Examples 5-7 are similar to those of the battery of Example 1, but the Dv50 of the inorganic nanoparticles is adjusted. The specific parameters are shown in Table 1.

[0118] The preparation methods of the batteries of Examples 8-11 are similar to those of the battery of Example 1, but the mass ratio of the inorganic nanoparticles to the organic solvent is adjusted. The specific parameters are shown in Table 1.

[0119] The preparation methods of the batteries of Examples 12-13 are similar to those of the batteries of Example 1, but the type of stabilizer is adjusted. The specific parameters are shown in Table 1.

[0120] The preparation method of the battery of Example 14 is similar to that of the battery of Example 1, but the electrolyte does not contain a stabilizer. The specific parameters are shown in Table 1.

[0121] The preparation methods of the batteries of Examples 15-16 are similar to those of the battery of Example 1, but the mass ratio of the stabilizer to the inorganic nanoparticles is adjusted. The specific parameters are shown in Table 1.

[0122] The battery of Comparative Example 1 was prepared in a similar manner to that of Example 1, but without the addition of inorganic nanoparticles and stabilizer. Specific parameters are shown in Table 1.

[0123] The battery of Comparative Example 2 was prepared in a similar manner to that of Example 1, but the size of the inorganic nanoparticles was 800 nm, and the inorganic nanoparticles could not be suspended and dispersed in the electrolyte. The specific parameters are shown in Table 1.

[0124] The battery of Comparative Example 3 is prepared in a similar manner to the battery of Example 1, but the inorganic nanoparticles are sodium fluoride, which dissolves in the electrolyte when added thereto. Specific parameters are shown in Table 1.

[0125] 2. Test Method

[0126] 1. Dv50 of inorganic nanoparticles

[0127] Refer to the particle size distribution laser diffraction method in GB / T 19077-2016. Weigh 0.1g–0.13g of inorganic nanoparticles into a 50ml beaker. Then, weigh 5g of anhydrous ethanol and add it to the beaker containing the inorganic nanoparticles. Place a stirring bar approximately 2.5mm in length in the beaker, and seal with plastic wrap. Ultrasonicate the sample for 5 minutes, then transfer it to a magnetic stirrer and stir at 500 rpm for at least 20 minutes. Two samples from each batch are tested. Laser particle size analyzers, such as the Mastersizer 2000E from Malvern Instruments Ltd., UK, are conveniently used for measurement.

[0128] 2. Electrolyte flammability test

[0129] The self-extinguishing time (SET) method is used to evaluate the flammability of electrolytes. Specifically, non-combustible glass fiber wool is formed into a ball with a diameter of approximately 5 mm. A predetermined amount of electrolyte is then dripped onto the ball, and the mass of the electrolyte dripped is recorded. In still air, the glass fiber wool is ignited using an igniter. The time from the start to the end of the electrolyte combustion is recorded. The self-extinguishing time per unit mass of electrolyte is used as the sustainable combustion time of the electrolyte.

[0130] 3. Battery thermal runaway time

[0131] Thermal runaway judgment conditions: ① The voltage drop exceeds 25% of the initial voltage, ② The temperature rise rate dT / dt ≥ 1℃ / s. When ① and ② are met at the same time, the battery is judged to have thermal runaway.

[0132] Experimental steps: After charging the battery to 100% SOC (State of Charge), heat the cell using a flat or rod-shaped heating device and record the changes in the cell's temperature and voltage. If thermal runaway occurs, deactivate the trigger, turn off the heating device, and record the time from the start of heating to this point, which is the battery's thermal runaway duration.

[0133] 4. Oxidation decomposition voltage of electrolyte

[0134] Testing equipment: electrochemical workstation

[0135] Linear sweep voltammetry (LSV) was used to measure the oxidative decomposition voltage of the electrolyte over the open-circuit voltage (OCV) to 6V, with a sweep rate of 0.1mV / s. A platinum electrode served as the working electrode, and a lithium foil served as the reference and counter electrodes. Important: During each test, the electrodes were completely immersed in the electrolyte, and the platinum electrode was polished with sandpaper before use. The oxidative decomposition voltage of the electrolyte was determined as the voltage at an oxidation current of 0.2mA.

[0136] 5. Battery cycle number

[0137] At 25°C, charge the battery at a constant current of 1 / 3C to 4.5V, then charge at a constant voltage of 4.5V until the current is less than 0.05C, let it sit for 5 minutes, and then discharge it at a constant current of 1 / 3C to 2.5V. The discharge capacity at 1 / 3C is recorded as the initial capacity C0. Repeat the above steps for the same battery and record the discharge capacity Cn of the battery after the nth cycle. The battery capacity retention rate after each cycle is Pn = Cn / C0*100%. When Pn≦80%, stop the test and record the number of cycles.

[0138] 3. Analysis of test results of various embodiments and comparative examples

[0139] Batteries of various examples and comparative examples were prepared according to the above methods, and various performance parameters were measured. The results are shown in Table 1 below.

[0140] Table 1

[0141] As can be seen from Table 1, the electrolytes in Examples 1-16 all include an organic solvent and inorganic nanoparticles, and the inorganic nanoparticles are suspended and dispersed in the organic solvent.

[0142] It can be seen from Examples 1-16 that when the electrolyte includes inorganic nanoparticles suspended and dispersed in an organic solvent, the electrolyte has a short sustainable combustion time and a high oxidation voltage, and the secondary battery has a long thermal runaway time, excellent safety performance and cycle stability.

[0143] From the comparison between Examples 1-16 and Comparative Examples 1-3, it can be seen that when the electrolyte includes inorganic nanoparticles suspended and dispersed in an organic solvent, the sustainable combustion time of the electrolyte can be shortened, the oxidation voltage of the electrolyte can be increased, the thermal runaway time of the battery can be extended, and the cycle stability of the battery can be optimized.

[0144] It can be seen from Examples 1 and 5-7 that when the particle size of the inorganic nanoparticles is 50nm-500nm, the electrolyte has a short sustainable combustion time and a high oxidation voltage, and the secondary battery has a long thermal runaway time and excellent cycle stability. When the particle size of the inorganic nanoparticles is 100nm-250nm, the battery has both high cycle stability and safety performance.

[0145] As shown in Examples 1 and 8-11, when the mass ratio of inorganic nanoparticles to organic solvent is 1:1.5-1:9, the electrolyte has a short sustained combustion time and a high oxidation voltage, and the battery has a long thermal runaway time and excellent cycling stability. When the mass ratio of inorganic nanoparticles to organic solvent is 1:3-1:6, the battery has both cycling stability and safety performance.

[0146] From the comparison of Example 1, Examples 12-13 and Example 14, it can be seen that when the electrolyte also includes a stabilizer, the sustainable combustion time of the electrolyte can be further shortened, the oxidation voltage of the electrolyte can be increased, the thermal runaway time of the battery can be further extended, and the safety performance and cycle stability of the battery can be optimized.

[0147] As shown in Examples 1 and 15-16, when the mass ratio of stabilizer to inorganic nanoparticles is 1:100-3:100, the electrolyte has a short sustainable combustion time and a high oxidation voltage, and the battery has a long thermal runaway time and excellent safety performance. When the mass ratio of stabilizer to inorganic nanoparticles is 2:100-3:100, the battery's safety performance and cycle stability are further improved.

[0148] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and within the scope of the technical solution of the present application, embodiments having substantially the same structure as the technical concept and exerting the same effects are all included in the technical scope of the present application. In addition, within the scope of the subject matter of the present application, various modifications that can be conceived by those skilled in the art to the embodiments, and other methods constructed by combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. An electrolyte, characterized in that: include: Organic solvents, and Inorganic nanoparticles are suspended and dispersed in the organic solvent.

2. The electrolyte according to claim 1, characterized in that The Dv50 of the inorganic nanoparticles is 50nm to 500nm, and can be optionally 100nm to 250nm.

3. The electrolyte according to claim 1 or 2, characterized in that The inorganic nanoparticles include at least one of metal silicates, metal nitrides, metal fluorides, and metal oxides.

4. The electrolyte according to any one of claims 1 to 3, characterized in that The inorganic nanoparticles include at least one of lithium silicate, lithium nitride, lithium fluoride and aluminum oxide.

5. The electrolyte according to any one of claims 1 to 4, characterized in that In the electrolyte, the mass ratio of the inorganic nanoparticles to the organic solvent is 1:1.5 to 1:9, and can be optionally 1:3 to 1:

6.

6. The electrolyte according to any one of claims 1 to 5, characterized in that The organic solvent includes at least one of a carbonate solvent, an ether solvent, and a carboxylate solvent.

7. The electrolyte according to claim 6, characterized in that The carbonate solvent includes one or more of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, and butylene carbonate; The ether solvents include 1,2-dimethoxypropane, dimethoxymethane, ethylene glycol dimethoxy One or more of ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, and dioxolane; The carboxylic acid ester solvent includes one or more of methyl formate, ethyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, and methyl butyrate.

8. The electrolyte according to any one of claims 1 to 7, characterized in that The electrolyte also includes a stabilizer, and the stabilizer includes a surfactant.

9. The electrolyte according to claim 8, characterized in that The surfactant includes one or more of sodium carboxymethyl cellulose, polysorbate, sodium polyoxyethylene fatty alcohol ether sulfate, sodium dodecyl sulfonate, sodium dodecyl sulfate, and sodium dodecylbenzene sulfonate.

10. The electrolyte according to claim 8 or 9, characterized in that: In the electrolyte, the mass ratio of the stabilizer to the inorganic nanoparticles is 1:100 to 3:100, and can be optionally 2:100 to 3:

100.

11. A secondary battery, characterized in that: The electrolyte comprising the electrolyte according to any one of claims 1 to 10.

12. An electrical device, characterized in that: The secondary battery according to claim 11 is included.

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