CN119315106A - Electrolyte, secondary battery and device - Google Patents

Abstract

The application provides an electrolyte, a secondary battery and a device. The electrolyte comprises lithium salt, a nonaqueous solvent, a first additive shown as a formula 1, a second additive shown as a formula 2 and a third additive shown as a formula 3;

Description

Electrolyte, secondary battery and device

Technical Field

The application relates to the field of energy storage, in particular to electrolyte, a secondary battery and a device.

Background

Among commercial rechargeable batteries, lithium ion batteries have higher energy density and wider operating voltage, and are widely applied to the fields of electric automobiles, digital 3C, energy storage and the like. The cost, lifetime, safety, etc. characteristics of lithium ion batteries have been the focus of attention of researchers. Safety performance, cycle performance and calendar life are key to whether the lithium ion battery can be applied to an electric automobile.

It is well known that upon excessive abuse, serious exothermic reactions (e.g., oxidative decomposition and combustion of electrolyte) occur inside lithium ion batteries, which are highly susceptible to swelling and even explosion fires. Overcharging is one of abuse of the battery, the heating problem of the battery can be caused in the early stage of overcharging, the reaction activity of the electrode pole piece and the electrolyte can be improved by the rise of the temperature of the battery, the decomposition of the electrolyte and the occurrence of side reactions are accelerated, and therefore the heat release quantity is improved, and the safety of the battery can be further deteriorated by the accumulation of the heat release quantity. Further increases in temperature can also directly affect the structural integrity of the separator and the binder in the positive and negative electrode sheets, thereby directly causing the battery to run away, and eventually possibly causing serious hazards such as fire and explosion.

Disclosure of Invention

In view of the above-described problems of the prior art, the present application provides an electrolyte, a secondary battery, and an apparatus. The first additive, the second additive and the third additive are added into the electrolyte, so that the electrode plate can be protected, side reactions between the electrode plate and the electrolyte are reduced, gas production is reduced, the safety performance and the cycle performance of the secondary battery are improved, and further, the first additive and the second additive can be oxidized and polymerized when the secondary battery is overcharged, so that thermal runaway is avoided.

A first aspect of the present application provides an electrolyte comprising a lithium salt, a nonaqueous solvent, a first additive shown in formula 1, a second additive shown in formula 2, and a third additive shown in formula 3;

In formula 1, R ₁ and R ₂ are each independently selected from hydrogen, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C1-C6 alkoxy, cyano or halogen;

in formula 2, R ₃、R₄、R₅、R₆、R₇、R₈ is each independently selected from hydrogen, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C1-C6 alkoxy, cyano, or halogen;

In formula 3, R ₉、R₁₀、R₁₁ and R ₁₂ are each independently selected from substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C2-C6 alkenyl, or substituted or unsubstituted C2-C6 alkynyl, wherein at least one of R ₉、R₁₀、R₁₁ and R ₁₂ is selected from substituted or unsubstituted C2-C6 alkenyl, or substituted or unsubstituted C2-C6 alkynyl;

the substituted substituents are each independently selected from cyano and/or halogen.

A second aspect of the present application provides a secondary battery comprising a first electrode tab, a second electrode tab, and the aforementioned electrolyte.

A third aspect of the present application provides an apparatus comprising the aforementioned secondary battery.

The technical scheme of the application can realize the following beneficial effects:

The first additive provided by the application is a benzene ring compound, the second additive is a biphenyl compound, and the third additive is an organosilicon compound. The first additive and the second additive are added into electrolyte in a combined mode, when the battery is overcharged, one with lower oxidation potential is subjected to oxidation polymerization by an electron dehydrogenation method preferentially, a layer of meshed polymer film is formed on the surface of an electrode plate, the layer of film has insulativity, a large amount of charges are consumed in the oxidation polymerization reaction process, and finally voltage rising is restrained, if the potential is continuously raised to the higher oxidation potential, one with higher oxidation potential is subjected to oxidation polymerization, a denser polymer film is formed, the finally formed polymer film has higher insulativity, voltage rising is restrained further, and accordingly, gradient polymerization effect is achieved along with voltage rising, voltage rising is restrained more effectively, electrolyte decomposition under high pressure is avoided, heat accumulation in the battery due to high pressure is avoided, damage to the electrode plate is avoided, and safety characteristics of the battery are improved. In addition, the oxidation potential of the first additive and the second additive is higher, so that oxidation polymerization can not occur in the normal formation and circulation processes of the lithium battery, and the negative effect on the performance of the battery can not be caused. In addition, in the early stage of overcharging and abuse of the battery, heat generated at the electrode plate can be increased suddenly, but the voltage does not reach the oxidation potential of the first additive or the second additive, at the moment, the first additive and the second additive can not play roles, the third additive can form a compact and uniform three-dimensional interface film on the surface of the positive electrode plate, can effectively isolate the contact between the electrode plate and the electrolyte, reduce side reaction, further improve the high temperature performance of the battery core and slow down the occurrence of thermal runaway phenomenon and thermal runaway hazard. In summary, the above materials are added into the electrolyte system in a combined manner, and the first additive, the second additive and the third additive can form a synergistic effect, so that on one hand, a compact solid electrolyte interface film can be formed on the surface of the electrode plate in the formation stage of the lithium battery, and the contact between the electrolyte and the electrode plate is reduced, so that the electrolyte is prevented from being decomposed under high voltage, on the other hand, oxidation polymerization can be performed when the lithium battery is overcharged, a layer of insulating film is formed on the surface of the electrode plate, and meanwhile, redundant charges are consumed, the voltage rise and the oxidation decomposition of the electrolyte are inhibited, and the safety performance of the battery is improved. Based on the above improvement, the electrolyte of the present application has excellent cycle performance, storage performance and safety performance at high temperature when used in a secondary battery.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the present application more apparent, the technical solutions of the present application will be clearly and completely described below with reference to the embodiments, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments. The related embodiments described herein are of illustrative nature and are intended to provide a basic understanding of the application. The embodiments of the present application should not be construed as limiting the application.

For simplicity, only a few numerical ranges are specifically disclosed herein. However, any lower limit may be combined with any upper limit to form a range not explicitly recited, and any lower limit may be combined with any other lower limit to form a range not explicitly recited, as may any upper limit combined with any other upper limit. Furthermore, each separately disclosed point or individual value may itself be combined as a lower limit or upper limit with any other point or individual value or with other lower limit or upper limit to form a range not explicitly recited.

In the description herein, unless otherwise indicated, "above", "below" includes this number.

Unless otherwise indicated, terms used in the present application have well-known meanings commonly understood by those skilled in the art. Unless otherwise indicated, the numerical values of the parameters set forth in the present application may be measured by various measurement methods commonly used in the art (e.g., may be tested according to the methods set forth in the examples of the present application).

The list of items to which the term "at least one of," "at least one of," or other similar terms are connected may mean any combination of the listed items. For example, if items A and B are listed, the phrase "at least one of A and B" means A alone, B alone, or A and B. In another example, if items A, B and C are listed, then the phrase "at least one of A, B and C" means either only A, or only B, only C, A and B (excluding C), A and C (excluding B), B and C (excluding A), or A, B and C all. Item a may comprise a single component or multiple components. Item B may comprise a single component or multiple components. Item C may comprise a single component or multiple components.

The term "silicon-based material" is not particularly limited as long as silicon is contained in the material. In the present application, the "silicon-based material" may be silicon, silicon alloy, silicon oxygen compound, silicon carbon compound, or any mixture of the above silicon-based materials.

The term "carbon-based material" is not particularly limited and may be graphite, soft carbon, hard carbon, carbon nanotubes, graphene, and any mixture of the foregoing carbon-based materials. Wherein the term "graphite" is not particularly limited, and may be artificial graphite and/or natural graphite.

The term "C1-C6 alkyl" includes, but is not limited to, methyl, ethyl, n-propyl, isopropyl, cyclopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, cyclobutyl, n-pentyl, isopentyl, neopentyl, cyclopentyl, methylcyclopentyl, n-hexyl, isohexyl, cyclohexyl and the like.

The term "C1-C6 alkoxy" includes, but is not limited to, methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, tert-butoxy, n-pentoxy, isopentoxy, n-hexoxy, and the like.

The term "C2-C6 alkenyl" includes, but is not limited to, ethenyl, propenyl, butenyl, pentenyl, hexenyl, and the like.

The term "C2-C6 alkynyl" includes, but is not limited to, ethynyl, propynyl, butynyl, pentynyl, hexynyl, and the like.

The term "substituted or unsubstituted" means that the functional group recited after the term may or may not have a substituent. For example, "substituted or unsubstituted C1-C6 alkyl" refers to C1-C6 alkyl having a substituent or unsubstituted C1-C6 alkyl. Wherein the number of the substituents can be 1 or more than 2, and the substituents comprise at least one of halogen, alkyl, aryl, heteroaryl or cyano. It will be appreciated that when the number of substituents is greater than 1, the substituents may be the same or different.

The application is further described below in conjunction with the detailed description. It should be understood that the detailed description is intended by way of illustration only and is not intended to limit the scope of the application.

1. Electrolyte solution

One or more embodiments of the present application provide an electrolyte including a lithium salt, a nonaqueous solvent, a first additive shown in formula 1, a second additive shown in formula 2, and a third additive shown in formula 3;

In formula 1, R ₁ and R ₃ are each independently selected from hydrogen, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C1-C6 alkoxy, cyano or halogen, in formula 2, R ₃、R₄、R₅、R₆、R₇、R₈ is each independently selected from hydrogen, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C1-C6 alkoxy, cyano or halogen, wherein at least one of R ₉、R₁₀、R₁₁ and R ₁₂ is selected from substituted or unsubstituted C2-C6 alkenyl or substituted or unsubstituted C2-C6 alkynyl, and in formula 3, R ₉、R₁₀、R₁₁ and R ₁₂ are each independently selected from substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C2-C6 alkenyl, substituted or unsubstituted C2-C6 alkynyl, and the substituted substituents are each independently selected from cyano and/or halogen.

The first additive provided by the application is a benzene ring compound, the second additive is a biphenyl compound, and the third additive is an organosilicon compound. The first additive and the second additive are added into electrolyte in a combined mode, when the battery is overcharged, one with lower oxidation potential is subjected to oxidation polymerization by an electron dehydrogenation method preferentially, a layer of meshed polymer film is formed on the surface of an electrode plate, the layer of film has insulativity, a large amount of charges are consumed in the oxidation polymerization reaction process, and finally voltage rising is restrained, if the potential is continuously raised to the higher oxidation potential, one with higher oxidation potential is subjected to oxidation polymerization, a denser polymer film is formed, the finally formed polymer film has higher insulativity, voltage rising is restrained further, and accordingly, gradient polymerization effect is achieved along with voltage rising, voltage rising is restrained more effectively, electrolyte decomposition under high pressure is avoided, heat accumulation in the battery due to high pressure is avoided, damage to the electrode plate is avoided, and safety characteristics of the battery are improved. In addition, the oxidation potential of the first additive and the second additive is higher, so that oxidation polymerization can not occur in the normal formation and circulation processes of the lithium battery, and the negative effect on the performance of the battery can not be caused. In addition, in the early stage of the overcharge abuse of the battery, heat generated at the electrode plate can be increased suddenly, but the voltage does not reach the oxidation potential of the first additive or the second additive, at the moment, the first additive and the second additive can not play roles, and the rest of the third additive can form a compact and uniform three-dimensional interface film on the surface of the positive electrode plate, so that the contact between the electrode plate and the electrolyte can be effectively isolated, the side reaction is reduced, the high temperature performance of the battery core is improved, and the occurrence of thermal runaway phenomenon and thermal runaway hazard of the battery are alleviated. In summary, the above materials are added into the electrolyte system in a combined manner, and the first additive, the second additive and the third additive can form a synergistic effect, so that on one hand, a compact solid electrolyte interface film can be formed on the surface of the electrode plate in the formation and composition stage of the lithium battery, and the contact between the electrolyte and the electrode plate is reduced, so that the electrolyte is prevented from being decomposed under high pressure, on the other hand, oxidation polymerization can be performed when the lithium battery is overcharged, an insulating film is formed on the surface of the electrode plate, and meanwhile, redundant charges are consumed, the voltage rise and the oxidative decomposition of the electrolyte are inhibited, and the safety performance of the battery is improved.

In some embodiments, in formula 1, R ₁ is selected from substituted or unsubstituted C1-C4 alkyl, cyano, or fluoro, and R ₂ is selected from substituted or unsubstituted C1-C4 alkyl. Wherein the substituted substituents are each independently selected from fluorine.

In some embodiments, in formula 2, R ₃、R₄ and R ₅ are each independently selected from hydrogen, substituted or unsubstituted C1-C4 alkyl, cyano, or fluoro, and R ₆、R₇ and R ₈ are each independently selected from hydrogen, substituted or unsubstituted C1-C4 alkyl, or fluoro. Wherein the substituted substituents are each independently selected from fluorine.

In some embodiments, in formula 3, R ₉、R₁₀ and R ₁₁ are each independently selected from substituted or unsubstituted C2-C3 alkenyl, substituted or unsubstituted C2-C3 alkynyl, and R ₁₂ is selected from substituted or unsubstituted C1-C3 alkyl, substituted or unsubstituted C2-C3 alkenyl, or substituted or unsubstituted C2-C3 alkynyl. Wherein the substituted substituents are each independently selected from fluorine.

In some embodiments, the first additive is selected from at least one of the following compounds:

In some embodiments, the second additive is selected from at least one of the following compounds:

In some embodiments, the third additive contains an unsaturated bond that enables its ability to copolymerize, and thus each molecular chain, to crosslink into a film. Therefore, the third additive can form a compact and uniform three-dimensional interface film on the surface of the positive electrode plate, can effectively isolate the contact between the electrode plate and electrolyte, and reduces side reactions, thereby improving the high-temperature performance of the battery cell and slowing down the occurrence of thermal runaway phenomenon and thermal runaway hazard. In some embodiments, the third additive is selected from at least one of the following compounds:

(tetravinyl silane, TVS),

In some embodiments, the first additive is

In some embodiments, the second additive is

In some embodiments, the third additive is

In some embodiments, the first additive isThe second additive isThe third additive is

In some embodiments, the first additive isThe second additive isThe third additive is

In some embodiments, the first additive isThe second additive isThe third additive is

In some embodiments, the first additive isThe second additive isThe third additive is

In some embodiments, the first additive is present in an amount of 1% to 5% by mass based on the mass of the electrolyte. Illustratively, the first additive comprises 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% by mass or a range of any two of the foregoing values. In some embodiments, the first additive is present in an amount of 2% to 4% by mass based on the mass of the electrolyte.

In some embodiments, the second additive is present in an amount of 1% to 5% by mass based on the mass of the electrolyte. Illustratively, the second additive comprises 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% by mass or a range of any two of the foregoing values. In some embodiments, the second additive is present in an amount of 2% to 4% by mass based on the mass of the electrolyte.

In some embodiments, the third additive is present in an amount of 0.5% to 3% by mass based on the mass of the electrolyte. Illustratively, the third additive comprises 0.5%, 0.7%, 1%, 1.3%, 1.5%, 1.7%, 2%, 2.3%, 2.5%, 2.7%, 3% or a range of any two of the foregoing values by mass. In some embodiments, the third additive is present in an amount of 1% to 2% by mass based on the mass of the electrolyte.

In some embodiments, the lithium salt comprises at least one of lithium hexafluorophosphate (LiPF ₆), lithium tetrafluoroborate (LiBF ₄), lithium bis (fluorosulfonyl) imide (LiFSI), (trifluoromethylsulfonyl) (perfluorobutylsulfonyl) imide (LiFNFSI), lithium bis (trifluoromethylsulfonyl) imide (LiTFSI), lithium bis (oxalato) borate (LiBOB), lithium bis (fluoromalonic acid) borate (LiBFMB), lithium 4, 5-dicyano-2- (trifluoromethyl) imidazole (LiTDI i), lithium difluorooxalato borate (lidaob).

In some embodiments, the concentration of lithium salt is 0.5mol/L to 1.5mol/L. The concentration of the lithium salt is 0.5mol/L, 0.6mol/L, 0.7mol/L, 0.8mol/L, 0.9mol/L, 1.0mol/L, 1.1mol/L, 1.2mol/L, 1.3mol/L, 1.4mol/L, 1.5mol/L or a range composed of any two of the above values.

In some embodiments, the nonaqueous solvent comprises at least one of a chain carbonate, a cyclic carbonate or a carboxylic acid ester, wherein the chain carbonate is selected from at least one of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methylethyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, the cyclic carbonate is selected from at least one of ethylene carbonate, propylene carbonate, butylene carbonate, and the carboxylic acid ester is selected from at least one of methyl formate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, butyl propionate.

In some embodiments, the non-aqueous solvent is present in an amount of 50% to 90% by mass based on the mass of the electrolyte. Illustratively, the nonaqueous solvent is present in a mass percent amount of 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90% or a range of any two values recited above, based on the mass of the electrolyte.

2. Secondary battery

One or more embodiments of the present application also provide a secondary battery including the electrolyte in the foregoing embodiments.

In some embodiments, the secondary battery of the present application further comprises a first electrode tab and a second electrode tab. The first electrode sheet may be a positive electrode sheet or a negative electrode sheet. The second electrode sheet may be a positive electrode sheet or a negative electrode sheet. The first electrode sheet and the second electrode sheet may be the same or different, and the present application is not particularly limited thereto.

Hereinafter, the secondary battery of the present application will be further explained by taking the first electrode tab as the positive electrode tab and the second electrode tab as the negative electrode tab as examples.

In some embodiments, the first electrode tab includes a first current collector and a first active material layer on a surface of the first current collector.

In some embodiments, the first current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel alloy, titanium alloy, silver alloy, or the like) on a polymer substrate.

In some embodiments, the first active material layer comprises a first active material.

In some embodiments, the first active material includes at least one of a nickel cobalt-based ternary material and a phosphate-based material.

In some embodiments, the nickel cobalt-based ternary material includes at least one of the LiNi _xCo_yM_(1-x-y)O₂ materials, M includes at least one of manganese, aluminum, magnesium, chromium, calcium, zirconium, molybdenum, silver, or niobium, 0.5.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.0.5, and x+y.ltoreq.1. In some embodiments, x is 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, or a range of any two of the foregoing values, and y is 0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, or a range of any two of the foregoing values. In particular, the method comprises the steps of, x is more than or equal to 0.8 and less than or equal to 1, and 0 is more than or equal to 0 y is less than or equal to 0.2, and x+y is less than or equal to 1. In some embodiments, the nickel cobalt-based ternary material includes at least one of NCA, NCM111, NCM523, NCM622, NCM811, ni90, ni92, or Ni 95.

In some embodiments, the phosphate-based material includes at least one of LiMn _kB_(1-k)PO₄, wherein 0.ltoreq.k.ltoreq.1, and the B element is selected from at least one of iron, cobalt, magnesium, calcium, zinc, chromium, or lead. In some embodiments, k is 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, or a range of any two of the foregoing values. In some embodiments, the phosphate-based material includes at least one of lithium iron phosphate, liMn _0.6Fe_0.4PO₄, or LiMn _0.8Fe_0.2PO₄.

In some embodiments, the first active material comprises at least one of lithium nickel oxide, lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese oxide, lithium nickel manganese cobalt magnesium oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium iron phosphate, lithium manganese iron phosphate.

In some embodiments, the first active material layer may further include a binder, and optionally a conductive agent. The binder enhances the bonding of the first active material particles to each other and also enhances the bonding of the first active material to the first current collector.

In some embodiments, the binder includes, but is not limited to, polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, an ethyleneoxy-containing polymer, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene 1, 1-difluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy or nylon, and the like.

In some embodiments, the conductive agent includes, but is not limited to, carbon-based materials, metal-based materials, conductive polymers, and mixtures thereof. In some embodiments, the carbon-based material comprises natural graphite, synthetic graphite, carbon black, acetylene black, ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metal-based material comprises metal powder, metal fibers, copper, nickel, aluminum, or silver. In some embodiments, the conductive polymer is a polyphenylene derivative.

In a specific example of the application, the first active material, the conductive agent and the adhesive are fully and uniformly stirred and mixed in an N-methyl pyrrolidone solvent system according to a certain proportion, and then are coated on an aluminum current collector, dried and rolled to obtain the first electrode plate. It is to be understood that the foregoing solvent system and current collector materials are illustrative only and are not intended to limit the application. The solvent system and current collector materials of the present application may be any combination conventionally selected in the art.

In some embodiments, the second electrode tab includes a second current collector and a second active material layer on a surface of the second current collector.

In some embodiments, the second current collector may include copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, or any combination thereof.

In some embodiments, the second active material layer includes a second active material.

In some embodiments, the second active material comprises a silicon-based material, or a mixture comprising a silicon-based material and at least one material selected from a carbon-based material, a tin-based material, a phosphorus-based material, and metallic lithium. The silicon-based material includes at least one of silicon, a silicon alloy, a silicon oxygen compound, and a silicon carbon compound. The carbon-based material includes at least one of graphite, soft carbon, hard carbon, carbon nanotubes, and graphene. The tin-based material includes at least one of tin, tin oxide, and tin alloy. The phosphorus-based material includes phosphorus and/or a phosphorus-carbon composite.

In some embodiments, the mass percent of the silicon-based material is 10% to 100% based on the mass of the second active material. Illustratively, the silicon-based material comprises 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100% by mass or a range of any two of the foregoing values.

In some embodiments, the second active material layer may further include a binder and a conductive agent.

In some embodiments, the binder includes, but is not limited to, polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, an ethyleneoxy-containing polymer, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene 1, 1-difluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy or nylon, and the like.

In some embodiments, the conductive agent includes, but is not limited to, carbon-based materials, metal-based materials, conductive polymers, and mixtures thereof. In some embodiments, the carbon-based material is selected from natural graphite, synthetic graphite, carbon black, acetylene black, ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metal-based material is selected from metal powder, metal fiber, copper, nickel, aluminum, or silver. In some embodiments, the conductive polymer is a polyphenylene derivative.

In a specific example of the application, the second active material, the conductive agent and the adhesive are fully and uniformly stirred and mixed in an N-methyl pyrrolidone solvent system according to a certain proportion, and then are coated on an aluminum current collector to be dried and rolled to obtain the second electrode plate. It is to be understood that the foregoing solvent system and current collector materials are illustrative only and are not intended to limit the application. The solvent system and current collector materials of the present application may be any combination conventionally selected in the art.

In some embodiments of the present application, the secondary battery further includes a separator between the first electrode tab and the second electrode tab to prevent a short circuit. The material and shape of the separator are not particularly limited in the embodiments of the present application, and may be any of the techniques disclosed in the prior art.

In some embodiments, the separator comprises a polymer or inorganic, etc., formed from a material that is stable to the electrolyte of the present application. For example, the separator may include a substrate layer and a surface treatment layer. The substrate layer is a non-woven fabric, a film or a composite film with a porous structure, and the material of the substrate layer comprises at least one of polyethylene, polypropylene, polyethylene terephthalate or polyimide. Specifically, a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric or a polypropylene-polyethylene-polypropylene porous composite membrane can be selected. The surface treatment layer is provided on at least one surface of the base material layer, and the surface treatment layer may be a polymer layer or an inorganic layer, or may be a layer formed by mixing a polymer and an inorganic substance.

In some implementations, the inorganic layer includes inorganic particles including at least one of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium oxide, tin oxide, cerium oxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate, and a binder. The binder comprises at least one of polyvinylidene fluoride, copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene or polyhexafluoropropylene. The polymer layer contains a polymer, and the material of the polymer comprises at least one of polyamide, polyacrylonitrile, acrylic polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride or poly (vinylidene fluoride-hexafluoropropylene).

In some embodiments, the secondary battery is a lithium secondary battery or a sodium secondary battery. In some embodiments, the lithium secondary battery includes, but is not limited to, a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

3. Battery module

One or more embodiments of the present application also provide a battery module including the aforementioned secondary battery.

The battery module of the present application employs the above-described secondary battery, and thus has at least the same advantages as the secondary battery. The number of secondary batteries contained in the battery module of the present application may be one or more, and the specific number may be adjusted according to the application and capacity of the battery module.

4. Battery pack

One or more embodiments of the present application also provide a battery pack including the aforementioned battery module.

The number of battery modules included in the battery pack may be one or more, and the specific number may be adjusted according to the application and capacity of the battery pack.

5. Device and method for controlling the same

One or more embodiments of the present application also provide an apparatus including at least one of the aforementioned secondary battery, battery module, and battery pack.

In some embodiments, the devices of the present application include, but are not limited to, notebook computers, pen-input computers, mobile computers, electronic book players, portable telephones, portable fax machines, portable copiers, portable printers, headsets, video recorders, liquid crystal televisions, hand-held cleaners, portable CDs, mini-compact discs, transceivers, electronic notepads, calculators, memory cards, portable audio recorders, radios, backup power supplies, motors, electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, motorcycles, mopeds, bicycles, lighting fixtures, toys, game consoles, clocks, electric tools, flashlights, cameras, household large-scale batteries or lithium-ion capacitors, and the like.

The technical scheme of the present application will be further described with reference to specific examples and comparative examples.

Examples and comparative examples

Example 1

Preparation of electrolyte in an argon-protected glove box (moisture <1ppm, oxygen content <1 ppm), ethylene Carbonate (EC) and Ethyl Methyl Carbonate (EMC) were mixed in a mass ratio of 30:70. Adding a first additive 1-1 accounting for 4 percent of the total mass of the electrolyte, a second additive 2-1 accounting for 4 percent of the total mass of the electrolyte and a third additive 3-1 accounting for 3 percent of the total mass of the electrolyte. Then, lithium hexafluorophosphate (LiPF ₆) was added to the mixture to a molar concentration of 1.2mol/L, and the mixture was stirred uniformly to obtain an electrolyte of example 1.

The preparation of the positive electrode plate comprises the steps of fully homogenizing a positive electrode active material LiNi _0.9Co_0.05Mn_0.05O₂, a conductive agent carbon nano tube/acetylene black and a binder polyvinylidene fluoride PVDF (PVDF) in a weight ratio of LiNi _0.9Co_0.05Mn_o.05O₂ (CNT/acetylene black) to PVDF=95 to (2/1) to 2 in an N-methylpyrrolidone solvent system, coating the mixture on an aluminum-coated current collector with the thickness of 12 mu m, drying and rolling to obtain the positive electrode plate.

The preparation of the negative electrode plate comprises the steps of fully homogenizing negative electrode active materials, namely artificial graphite, silicon-oxygen (SiO _x), conductive agent acetylene black, binder styrene-butadiene rubber, thickener sodium carboxymethyl cellulose and polyacrylic acid in a deionized water solvent according to the weight ratio of 85:10:2:1.5:1:0.5, coating the mixture on a copper current collector with the thickness of 8 mu m, drying, and rolling to obtain the negative electrode plate.

The diaphragm is a polyethylene diaphragm.

And (3) preparing the lithium ion battery, namely sequentially adopting Z-shaped lamination for the positive electrode plate, the diaphragm and the negative electrode plate, placing the obtained bare cell in a punched aluminum plastic film soft package shell, drying, injecting nonaqueous electrolyte, and finally obtaining the lithium ion battery through the procedures of standing, formation, aging, degassing, shaping and the like.

Examples 2 to 22 and comparative examples 1 to 11

Examples 2 to 22 and comparative examples 1 to 11 were achieved by adjusting the kinds and contents of additives and the like in the electrolyte based on example 1, and specific adjustment measures and detailed data are shown in table 1.

Test method

1. Oxidation potential test

And assembling the positive electrode plate half battery for LSV (Linear volt-ampere scanning test), wherein the positive electrode plate is made of a high-nickel ternary material, the negative electrode plate is made of lithium metal, the scanning voltage range is 0-6V, and the scanning speed is 1mV/s. The oxidation potential window of the electrolytes containing different combinations of additives obtained in the different examples and comparative examples was tested for the high nickel positive electrode sheet.

2. Cycle capacity retention rate

The lithium ion battery is placed in an environment of 25 ℃, is charged to 4.25V by constant current and constant voltage, the cut-off current is 0.01C, and is discharged to 3V by constant current, and the capacity retention rate is calculated after 500 circles of circulation. The calculation formula is as follows:

Capacity retention (%) =discharge capacity after N cycles/first discharge capacity×100%.

3. Overcharge test

Placing the battery after the formation and capacity division in a constant temperature box at 25 ℃, charging to 200% SOC at a constant current of 1 ℃, ending the test if the process is in thermal runaway, and continuing the test if the process is not in runaway.

4. Thickness rate of change test

In the overcharge test process, the change of the thickness of the battery is marked by a micrometer at the moment, and the thickness change rate is calculated. The calculation formula is as follows:

thickness change rate (%) = lithium ion battery thickness before thermal runaway/lithium ion battery thickness before overcharge.

5. Impedance (DCR) growth rate test

The lithium ion battery involved in the cycle capacity retention test was subjected to a 50% soc DCR test before and after cycling. In the 50% SOC state, the DCR in this state was recorded by discharging at 2C current for 10 s.

Post-cycle impedance increase rate (%) = 50% soc DCR after cycle/50% soc DCR before cycle x 100%.

Referring to table 1, examples 1 to 22 each added different combinations of the first additive, the second additive, and the third additive to the electrolyte, the oxidation potential, the thickness variation, and the impedance variation of the lithium ion batteries of examples 1 to 22 were all significantly improved, the overcharge gain effect was significantly improved, and the capacity retention rate was not deteriorated, as compared to comparative example 1 in which no any of the above-described compounds was added. In combination with comparative examples 2 to 4, it can be seen that the overcharge gain effect was not significant in the case where only any one of the first additive, the second additive and the third additive was added. As can be seen in connection with comparative example 5, in the case where the first additive and the second additive were used, but the third additive was not used, the overcharge gain effect was rather lowered, the impedance change was insignificant, and the thickness change was more significant. In the case of using only the first additive and the third additive, or the second additive and the third additive in combination with comparative examples 7 and 8, the overcharge gain effect was also not significant. In combination with comparative example 10, the thickness variation significantly deteriorated when the content of the third additive was low. It can be seen that the synergy between the three compounds is evident. Further, in combination with comparative examples 8, 9 and 11, when any one of the first additive, the second additive and the third additive is excessive, the overcharge gain effect thereof is improved, but the capacity retention after cycling, the impedance change, and the thickness change thereof are markedly deteriorated. This is because all three additives are non-lithium conducting materials, and consumption of the additives after polymerization during circulation causes a significant change in impedance. Therefore, the dosage needs to be reasonably matched and controlled.

While certain exemplary embodiments of the application have been illustrated and described, the application is not limited to the disclosed embodiments. Rather, one of ordinary skill in the art will recognize that certain modifications and changes may be made to the described embodiments without departing from the spirit and scope of the present application as described in the appended claims.

Claims (11)

1. An electrolyte solution, which is used for the electrolytic solution, characterized by comprising the following steps:

A lithium salt, a nonaqueous solvent, a first additive shown in formula 1, a second additive shown in formula 2, and a third additive shown in formula 3;

In formula 1, R ₁ and R ₂ are each independently selected from hydrogen, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C1-C6 alkoxy, cyano or halogen;

in formula 2, R ₃、R₄、R₅、R₆、R₇、R₈ is each independently selected from hydrogen, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C1-C6 alkoxy, cyano, or halogen;

In formula 3, R ₉、R₁₀、R₁₁ and R ₁₂ are each independently selected from substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C2-C6 alkenyl, or substituted or unsubstituted C2-C6 alkynyl, wherein at least one of R ₉、R₁₀、R₁₁ and R ₁₂ is selected from substituted or unsubstituted C2-C6 alkenyl, or substituted or unsubstituted C2-C6 alkynyl;

the substituted substituents are each independently selected from cyano and/or halogen.

2. The electrolyte of claim 1, wherein the electrolyte meets at least one of the following conditions:

(a) In formula 1, R ₁ is selected from substituted or unsubstituted C1-C4 alkyl, cyano or fluoro, and R ₂ is selected from substituted or unsubstituted C1-C4 alkyl;

(b) In formula 2, R ₃、R₄ and R ₅ are each independently selected from hydrogen, substituted or unsubstituted C1-C4 alkyl, cyano, or fluoro, and R ₆、R₇ and R ₈ are each independently selected from hydrogen, substituted or unsubstituted C1-C4 alkyl, or fluoro;

(c) In formula 3, R ₉、R₁₀ and R ₁₁ are each independently selected from substituted or unsubstituted C2-C3 alkenyl, substituted or unsubstituted C2-C3 alkynyl, R ₁₂ is selected from substituted or unsubstituted C1-C3 alkyl, substituted or unsubstituted C2-C3 alkenyl, or substituted or unsubstituted C2-C3 alkynyl;

(d) The substituted substituents are each independently selected from fluorine.

3. The electrolyte of claim 2, wherein the electrolyte further satisfies at least one of the following conditions:

(e) The first additive is selected from at least one of the following compounds:

(f) The second additive is selected from at least one of the following compounds:

(g) The third additive is selected from at least one of the following compounds:

4. the electrolyte according to any one of claims 1 to 3, wherein the electrolyte further satisfies at least one of the following conditions:

(h) The first additive is 1-3 or 1-7;

(i) The second additive is

(J) The third additive is

5. The electrolyte according to claim 4, characterized in that the first additive isThe second additive isThe third additive is

6. The electrolyte according to any one of claims 1 to 3, wherein the electrolyte further satisfies at least one of the following conditions:

(k) The first additive is 1 to 5% by mass based on the mass of the electrolyte;

(l) The mass percentage content of the second additive is 1 to 5 percent based on the mass of the electrolyte;

(m) the third additive is 0.5 to 3% by mass based on the mass of the electrolyte.

7. The electrolyte of claim 6, wherein the electrolyte further satisfies at least one of the following conditions:

(n) the first additive is 2 to 4% by mass based on the mass of the electrolyte;

(o) the second additive is present in an amount of 2 to 4% by mass based on the mass of the electrolyte;

(p) the third additive is present in an amount of 1 to 2% by mass based on the mass of the electrolyte.

8. The electrolyte according to any one of claims 1 to 3, wherein the electrolyte further satisfies at least one of the following conditions:

(q) the lithium salt comprises at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis (fluorosulfonyl) imide, (trifluoromethylsulfonyl) (perfluorobutylsulfonyl) imide, lithium bistrifluoromethylsulfonyl imide, lithium bisoxalato borate, lithium 4, 5-dicyano-2- (trifluoromethyl) imidazole or lithium difluorooxalato borate, and the concentration of the lithium salt is 0.5mol/L to 1.5mol/L;

The nonaqueous solvent comprises at least one of chain carbonate, cyclic carbonate or carboxylic ester, wherein the chain carbonate is at least one of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, methyl propyl carbonate and ethyl propyl carbonate, the cyclic carbonate is at least one of ethylene carbonate, propylene carbonate and butylene carbonate, the carboxylic ester is at least one of methyl formate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate and butyl propionate, and the mass percentage of the nonaqueous solvent is 50-90% based on the mass of the electrolyte.

9. A secondary battery comprising a first electrode sheet, a second electrode sheet and the electrolyte according to any one of claims 1 to 8.

10. The secondary battery according to claim 9, wherein the secondary battery satisfies at least one of the following conditions:

(s) the first electrode sheet comprises a first active material layer, wherein the first active material of the first active material layer comprises at least one of a nickel-cobalt ternary material and a phosphate material, the nickel-cobalt ternary material comprises at least one of LiNi _xCo_yM_(1-x-y)O₂ material, M comprises at least one of manganese, aluminum, magnesium, chromium, calcium, zirconium, molybdenum, silver or niobium, x is more than or equal to 0.5 and less than or equal to 1, y is more than or equal to 0 and less than or equal to 0.5, x+y is less than or equal to 1, the phosphate material comprises at least one of LiMn _kB_(1-k)PO₄, k is more than or equal to 0 and less than or equal to 1, and B element comprises at least one of iron, cobalt, magnesium, calcium, zinc, chromium or lead;

(t) the second electrode tab comprises a second active material layer comprising a silicon-based material comprising at least one of graphite, soft carbon, hard carbon, carbon nanotubes and graphene, or a mixture of a silicon-based material comprising at least one of graphite, soft carbon, hard carbon, carbon nanotubes and graphene and at least one material selected from the group consisting of carbon-based materials comprising at least one of tin, tin oxide and tin alloy, phosphorus-based materials comprising phosphorus and/or phosphorus-carbon composites, and a mass percentage of the silicon-based material based on the mass of the second active material of 10% to 100%.

11. An apparatus comprising the secondary battery according to claim 9 or 10.