Electrolyte, secondary battery, and electric device

Abstract

The invention provides an electrolyte, a secondary battery and an electric device. The electrolyte comprises an organic solvent and inorganic nanoparticles, and the inorganic nanoparticles are suspended and dispersed in the organic solvent. The electrolyte has short sustainable combustion time and high oxidation voltage, and the battery has long thermal runaway time and excellent cycle stability.

Description

Technical Field

[0001] 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

[0002] In recent years, secondary batteries have been widely used in energy storage power systems such as hydropower, thermal, wind and solar power stations, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.

[0003] The secondary batteries of the prior art often use non-aqueous solvents as electrolyte solvents, which are prone to fire, explosion and other safety accidents caused by the combustion of the electrolyte. Therefore, the existing electrolytes still need to be improved. Summary of the invention

[0004] The present application is made in view of the above-mentioned problems, and its purpose is to provide an electrolyte which 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.

[0005] 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.

[0006] Electrolytes with organic molecules as solvents often make secondary batteries have better electrochemical performance and are the mainstream electrolyte system for secondary batteries now. However, the organic solvents therein have poor thermal and chemical stability, are easy to burn under overheating conditions, and are easy to oxidize and decompose at the positive electrode, thus affecting the safety performance and cycle stability of the battery. When the electrolyte includes inorganic nanoparticles, since the size of the inorganic particles is at the nanometer level, they have a large specific surface area and surface energy, and the surface is usually charged, which makes the surface of the nano inorganic particles and the organic solvent have a certain adsorption effect and charge interaction, so that the inorganic nanoparticles can overcome gravity, suspend and disperse in the electrolyte, and can play a role in "binding" the organic solvent, reducing the volatility of the solvent in the electrolyte, thereby improving the thermal stability of the electrolyte, reducing the sustainable combustion time of the electrolyte, and thus prolonging the thermal runaway time of the battery. At the same time, the inorganic nanoparticles suspended and dispersed in the electrolyte can also reduce the oxidation and decomposition of the electrolyte at the positive electrode by reducing the free solvent content and improving the antioxidant level of the electrolyte, thereby increasing the oxidation voltage of the secondary battery and improving the electrochemical performance of the battery. Inorganic nanoparticles have good thermal stability and electrochemical stability. The inorganic nanoparticles in the electrolyte can exist stably during the cycle process 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.

[0007] In any embodiment, the Dv50 of the inorganic nanoparticles is 50 nm to 500 nm, and can be optionally 100 nm to 250 nm.

[0008] 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, 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.

[0009] In any embodiment, the inorganic nanoparticles include at least one of metal silicates, metal nitrides, metal fluorides, and metal oxides.

[0010] In any embodiment, the inorganic nanoparticles include at least one of lithium silicate, lithium nitride, lithium fluoride, and aluminum oxide.

[0011] 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.

[0012] 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.

[0013] In any embodiment, the organic solvent includes at least one of a carbonate solvent, an ether solvent, and a carboxylate solvent.

[0014] 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.

[0015] In any embodiment, the electrolyte further includes a stabilizer, and the stabilizer includes a surfactant.

[0016] 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 solvents, thereby reducing the aggregation of inorganic nanoparticles and making the inorganic nanoparticles stably suspended and dispersed in the 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 battery's safety performance and cycle stability.

[0017] In any embodiment, 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.

[0018] 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.

[0019] 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.

[0020] A second aspect of the present application provides a secondary battery, comprising the electrolyte in any embodiment.

[0021] 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

[0022] Figure 1 is a schematic diagram of a secondary battery according to an embodiment of the present application;

[0023] Figure 2 yes Figure 1 An exploded view of a secondary battery according to an embodiment of the present application is shown;

[0024] Figure 3 is a schematic diagram of a battery module according to an embodiment of the present application;

[0025] Figure 4 is a schematic diagram of a battery pack according to an embodiment of the present application;

[0026] Figure 5 yes Figure 4 An exploded view of a battery pack according to an embodiment of the present application is shown;

[0027] Figure 6FIG. 1 is a schematic diagram of an electric device using a secondary battery according to an embodiment of the present application as a power source.

[0028] Description of reference numerals:

[0029] 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 secondary battery; 51 shell; 52 electrode assembly; 53 cover plate. DETAILED DESCRIPTION

[0030] Hereinafter, the embodiments of the electrolyte, secondary battery and electrical device of the present application are specifically disclosed in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are 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 descriptions 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.

[0031] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a 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 a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present 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 real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it 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.

[0032] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0033] 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.

[0034] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means 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), which means 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.

[0035] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0036] If not specifically stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": 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).

[0037] Non-aqueous electrolytes are generally composed of electrolyte salts and organic solvents, which have a significant impact on battery safety, cycle life, high and low temperature performance and other properties. The organic solvents in the existing electrolyte composition usually have problems such as low boiling point, high volatility, and high flammability. When the battery is at high temperature or short-circuited, it is easy to cause safety accidents such as fire and explosion caused by electrolyte combustion. On the other hand, the organic solvents in the electrolyte have poor stability and are easily oxidized and decomposed at the positive electrode, while consuming lithium salts, which in turn deteriorates the impedance and cycle performance of the battery.

[0038] [Electrolyte]

[0039] 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.

[0040] As used herein, the term "inorganic nanoparticles" refers to particles including inorganic salts, inorganic non-metallic materials, and the particles are nanometer-sized in at least one dimension.

[0041] In some embodiments, inorganic nanoparticles refer to particles whose sizes in three dimensions are within 1000 nm.

[0042] Electrolytes with organic molecules as solvents often make secondary batteries have better electrochemical performance and are the mainstream electrolyte system for secondary batteries now. However, the organic solvents in them have poor thermal and chemical stability, are easy to burn under overheating conditions, and are easy to oxidize and decompose at the positive electrode, thus affecting the safety and cycle performance of the battery. When the electrolyte includes inorganic nanoparticles, since the size of the inorganic particles is at the nanometer level, they have a large specific surface area and surface energy, and the surface is usually charged, which makes the surface of the nano inorganic particles and the organic solvent have a certain adsorption effect and charge interaction; and the inorganic nanoparticles have a small mass, and can overcome the gravity by means of the interaction force with the solvent, and are suspended and dispersed in the electrolyte. The inorganic nanoparticles suspended and dispersed in the electrolyte can effectively "bind" the organic solvent through their large specific surface area, greatly reduce the free solvent content in the electrolyte, and increase the energy barrier required for the combustion of the solvent in the electrolyte, thereby improving the thermal stability of the electrolyte, reducing the sustainable combustion time of the electrolyte, and thus prolonging the thermal runaway time of the battery.

[0043] At the same time, the inorganic nanoparticles suspended and dispersed in the electrolyte can also reduce the free solvent content, improve the antioxidant level of the electrolyte, reduce the oxidative decomposition of the electrolyte at the positive electrode, increase the oxidation voltage of the secondary battery, and improve the electrochemical performance of the battery. Inorganic nanoparticles have good thermal stability and electrochemical stability. The inorganic nanoparticles in the electrolyte can exist stably during the cycle process without 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.

[0044] In some embodiments, the organic solvent includes at least one of a carbonate solvent, an ether solvent, and a carboxylate solvent.

[0045] 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.

[0046] In some embodiments, the Dv50 of the inorganic nanoparticles is 50 nm to 500 nm, and can be optionally 100 nm to 250 nm.

[0047] 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.

[0048] In this application, the Dv50 of the inorganic nanoparticles can be tested by methods known in the art. As an example, referring to the particle size distribution laser diffraction method of GB / T 19077-2016, 0.1g to 0.13g of inorganic nanoparticles are weighed in a 50ml beaker, and 5g of anhydrous ethanol is weighed, added to the beaker containing the inorganic nanoparticles, and a stirring bar with a length of about 2.5mm is placed, and sealed with plastic wrap. The sample is placed in an ultrasonic machine for 5min, transferred to a magnetic stirrer and stirred at a speed of 500r / min for more than 20min, and 2 samples are taken from each batch of products for testing. The laser particle size analyzer is used for determination, such as the Mastersizer 2000E laser particle size analyzer of Malvern Instruments Co., Ltd., UK.

[0049] 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.

[0050] 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, 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.

[0051] In some embodiments, the inorganic nanoparticles include at least one of metal silicates, metal nitrides, metal fluorides, and metal oxides.

[0052] In some embodiments, the inorganic nanoparticles include at least one of lithium silicate, lithium nitride, lithium fluoride, and aluminum oxide.

[0053] The inorganic nanoparticles can be stably suspended in the electrolyte, and through their interaction with the organic solvent, they can greatly improve the flame retardancy and safety of the electrolyte. Furthermore, the inorganic nanoparticles have strong electrochemical stability and can stably exist during the cycle process, reducing the oxidative decomposition of the organic solvent in the electrolyte under high pressure and improving the cycle stability of the battery.

[0054] In some embodiments, 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.

[0055] 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.

[0056] 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, 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.

[0057] In some embodiments, the electrolyte further includes a stabilizer, and the stabilizer includes a surfactant.

[0058] 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.

[0059] 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 improving 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 battery's safety performance and cycle stability.

[0060] In some embodiments, the surfactant includes one or more of sodium carboxymethyl cellulose, polysorbate, sodium polyoxyethylene fatty alcohol sulfate, sodium dodecyl sulfonate, sodium dodecyl sulfate, and sodium dodecylbenzene sulfonate.

[0061] In some embodiments, 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.

[0062] 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.

[0063] 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.

[0064] 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 bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0065] In some embodiments, the electrolyte may further include additives, such as 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, additives that improve battery high or low temperature performance, etc.

[0066] [Positive electrode]

[0067] 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.

[0068] 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 any one or both of the two opposite surfaces of the positive electrode current collector.

[0069] 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.).

[0070] In some embodiments, the positive electrode active material may adopt a positive electrode active material for a battery that is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: a lithium-containing phosphate with an olivine structure, a lithium transition metal oxide, 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. Among them, 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 Mn 0.25 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, etc. Examples of lithium-containing phosphates with an olivine structure 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.

[0071] In some embodiments, the positive electrode film layer may also optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0072] 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.

[0073] In some embodiments, the positive electrode sheet can be prepared in the following manner: 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 collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0074] [Negative electrode]

[0075] The negative electrode plate includes a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material.

[0076] 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 any one or both of the two opposite surfaces of the negative electrode current collector.

[0077] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, a copper foil may be used. The composite current collector may include a polymer material base layer 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 (copper, copper 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.).

[0078] In some embodiments, the negative electrode active material may adopt the negative electrode active material for the battery 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 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, 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.

[0079] 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).

[0080] In some embodiments, the negative electrode film layer may further include a conductive agent. As an 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.

[0081] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0082] In some embodiments, the negative electrode sheet can be prepared in the following manner: 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 collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0083] [Isolation film]

[0084] 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 stability and mechanical stability can be selected.

[0085] In some embodiments, the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0086] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.

[0087] In some embodiments, the secondary battery may include an outer package, which may be used to encapsulate the electrode assembly and the electrolyte.

[0088] In some embodiments, the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0089] In the present application, the shape of the secondary battery includes but is not limited to cylindrical, square or other arbitrary shapes. For example, Figure 1 The secondary battery 5 is a square structure as an example.

[0090] In some embodiments, reference Figure 2 , the outer package may include a shell 51 and a cover plate 53. Among them, 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 form 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.

[0091] In some embodiments, secondary batteries may be assembled into a battery module. The number of secondary batteries contained in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.

[0092] Figure 3 4 is an example of a battery module. Figure 3 In the battery module 4, the plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of secondary batteries 5 may be fixed by fasteners.

[0093] 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.

[0094] 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 according to the application and capacity of the battery pack.

[0095] Figure 4 and Figure 5 1 is a battery pack 1 as an example. Figure 4 and Figure 5 The battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0096] The present application also provides an electrical 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 electrical device, and can also be used as an energy storage unit for the electrical device. The electrical 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 are not limited thereto.

[0097] As an electrical device, a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.

[0098] Figure 6 The power consumption device is taken as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the high power and high energy density requirements of the power consumption device for the secondary battery, a battery pack or a battery module can be used.

[0099] Another example of a device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be thin and light, and a secondary battery may be used as a power source.

[0100] Example

[0101] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0102] 1. Preparation method

[0103] Embodiment 1:

[0104] 1) Preparation of negative electrode sheet

[0105] (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, the coating speed is 25 m / min, and the temperature of the coating oven is 110° C.-130° C.; and then the negative electrode sheet is obtained by cold pressing and slitting;

[0106] 2) Preparation of positive electrode

[0107] 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 positive electrode slurry is uniformly 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.

[0108] 3) Preparation of electrolyte

[0109] In an argon atmosphere glove box (H2O content <0.1ppm, O2 content <0.1ppm), lithium salt lithium hexafluorophosphate LiPF6 is dissolved in a mixed system of organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (EC:EMC volume ratio is 3:7), and the concentration of lithium hexafluorophosphate LiPF6 is 1 mol / L; then inorganic nanoparticles aluminum oxide and stabilizer sodium dodecylbenzene sulfonate are added, wherein the ratio of the mass of aluminum oxide to the total mass of EC and EMC is 1:4; the ratio of the mass of stabilizer sodium dodecylbenzene sulfonate to the mass of inorganic nanoparticles aluminum oxide is 1:50, and the mixture is stirred evenly so that the inorganic nanoparticles aluminum oxide are stably suspended and dispersed in the electrolyte to obtain an electrolyte.

[0110] 4) Isolation film

[0111] A 9 μm polyethylene (PE) film was used as the isolation membrane.

[0112] 5) Preparation of batteries

[0113] 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, and 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 subjected to vacuum packaging, standing, forming, shaping and other processes to obtain the secondary battery product of Example 1.

[0114] The preparation methods of the batteries of Examples 2-4 are similar to those of the batteries of Example 1, but the types of inorganic nanoparticles are adjusted, and Dv50 changes accordingly. The specific parameters are shown in Table 1.

[0115] The preparation methods of the batteries of Examples 5-7 are similar to those of the batteries of Example 1, but the Dv50 of the inorganic nanoparticles is adjusted. The specific parameters are shown in Table 1.

[0116] 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.

[0117] The preparation method of the battery of Examples 12-13 is similar to that of the battery of Example 1, but the type of stabilizer is adjusted. The specific parameters are shown in Table 1.

[0118] 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.

[0119] The preparation method of the battery of Examples 15-16 is similar to that 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.

[0120] The preparation method of the battery of Comparative Example 1 is similar to that of the battery of Example 1, but inorganic nanoparticles and stabilizer are not added. The specific parameters are shown in Table 1.

[0121] The preparation method of the battery of Comparative Example 2 is similar to that of the battery of Example 1, but the size of the inorganic nanoparticles is 800 nm, and the inorganic nanoparticles cannot be suspended and dispersed in the electrolyte. The specific parameters are shown in Table 1.

[0122] 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 will dissolve in the electrolyte when added to the electrolyte. The specific parameters are shown in Table 1.

[0123] 2. Test Method

[0124] 1. Dv50 of inorganic nanoparticles

[0125] Referring to the particle size distribution laser diffraction method of GB / T 19077-2016, weigh 0.1g to 0.13g of inorganic nanoparticles in a 50ml beaker, then weigh 5g of anhydrous ethanol, add it to the beaker containing inorganic nanoparticles, put in a stirring bar with a length of about 2.5mm, and seal it with plastic wrap. Put the sample into an ultrasonic machine for 5min, transfer it to a magnetic stirrer and stir it at a speed of 500r / min for more than 20min. Take 2 samples from each batch of products for testing. It is convenient to use a laser particle size analyzer, such as the Mastersizer 2000E laser particle size analyzer of Malvern Instruments Co., Ltd. in the UK.

[0126] 2. Electrolyte flammability test

[0127] The self-extinguishing time method (SET) is used to evaluate the flammability of the electrolyte. The specific steps are to make the non-combustible glass fiber wool into a ball with a diameter of about 5 mm, then drip a certain amount of electrolyte on the glass fiber wool, and record the mass of the dripped electrolyte. Under windless conditions, the glass fiber wool is ignited with an igniter, and the time from the start to the end of the combustion of the electrolyte in the glass fiber wool is recorded. The self-extinguishing time of the unit mass of the electrolyte is used as the sustainable combustion time of the electrolyte.

[0128] 3. Battery thermal runaway time

[0129] 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.

[0130] Experimental steps: After the battery is charged to 100% SOC (State of Charge), use a flat or rod-shaped heating device to heat the battery cell and record the temperature and voltage changes of the battery cell. When thermal runaway occurs, stop triggering, turn off the heating device, and record the time from the start of heating to this point, which is the thermal runaway time of the battery.

[0131] 4. Oxidation decomposition voltage of electrolyte

[0132] Test equipment: Electrochemical workstation

[0133] Linear sweep voltammetry (LSV) was used to measure the oxidation decomposition voltage of the electrolyte, with a voltage range of open circuit voltage to 6V and a scan rate of 0.1mV / s. During the test, a platinum electrode was used as the working electrode, and a lithium sheet was used as the reference electrode and counter electrode. Note: For each test, the electrolyte completely submerged the electrode, and the platinum electrode was polished with sandpaper before use. The voltage when the oxidation current was 0.2mA was used as the oxidation decomposition voltage of the electrolyte.

[0134] 5. Battery cycle number

[0135] 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 to a current less than 0.05C, leave it 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 at the same time. 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.

[0136] III. Analysis of test results of various embodiments and comparative examples

[0137] The batteries of the embodiments and comparative examples were prepared according to the above method, and various performance parameters were measured. The results are shown in Table 1 below.

[0138] Table 1

[0139]

[0140] 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.

[0141] 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.

[0142] 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.

[0143] It can be seen from Examples 1 and 5 to 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, the secondary battery has a long thermal runaway time and excellent cycle stability, and when the particle size of the inorganic nanoparticles is 100nm-250nm, the battery has both high cycle stability and safety performance.

[0144] It can be seen from Examples 1 and 8-11 that when the mass ratio of inorganic nanoparticles to organic solvent is 1:1.5-1:9, the electrolyte has a short sustainable combustion time and a high oxidation voltage, and the battery has a long thermal runaway time and excellent cycle stability. When the mass ratio of inorganic nanoparticles to organic solvent is 1:3-1:6, the battery has both cycle stability and safety performance.

[0145] From the comparison between 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.

[0146] It can be seen from Examples 1 and 15-16 that when the mass ratio of the stabilizer to the 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 the stabilizer to the inorganic nanoparticles is 2:100-3:100, the safety performance and cycle stability of the battery are further improved.

[0147] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of 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 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 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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