Battery

Abstract

The present disclosure relates to the technical field of batteries. Specifically, the present disclosure relates to a battery, comprising an electrolyte and a negative electrode sheet, wherein the electrolyte comprises a first additive and a second additive, and the first additive has a structure as represented by formula 1; the second additive comprises at least one of tripropargyl phosphate, propyl bis(2-propynyl) phosphate, and ethyl bis(2-propynyl) phosphate; and the negative electrode sheet comprises a negative electrode active material, and the negative electrode active material comprises a silicon element. The battery containing the above additives has high interface flatness and good cycling performance.

Description

A type of battery

[0001] Priority information

[0002] This disclosure claims priority and benefits to patent application 202510094491.9, filed with the China National Intellectual Property Administration on January 21, 2025, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to the field of battery technology, and more specifically, to a battery. Background Technology

[0004] Silicon possesses extremely high theoretical specific capacity (4200 mAh / g), low lithium intercalation potential, and can provide Li in multiple directions. + While silicon-based lithium-ion batteries possess intercalation / deintercalation channels, they suffer from poor conductivity, brittle particles, unstable SEI growth, and volume expansion. These issues ultimately lead to reduced coulombic efficiency and cycle life, as well as poor fast-charge cycle capability. Therefore, regulating electrolyte composition and improving SEI film stability are crucial for enhancing the electrochemical performance of silicon-containing lithium-ion batteries. Summary of the Invention

[0005] This disclosure aims to at least partially address one of the technical problems in the related art. Therefore, one object of this disclosure is to provide a battery with good interface flatness and excellent fast-charge cycle performance.

[0006] Therefore, this disclosure provides a battery, including an electrolyte and a negative electrode sheet. The electrolyte includes a first additive and a second additive. The first additive has the structure shown in Formula 1. The second additive includes at least one of triargyl phosphate, propyl bis(2-propynyl) phosphate, and ethyl bis(2-propynyl) phosphate. The negative electrode sheet includes a negative electrode active material, and the negative electrode active material includes silicon.

[0007] In view of the fact that the electrode interface of existing secondary batteries is easily damaged during cycling, this disclosure provides a battery including a first additive and a second additive. The two additives undergo electropolymerization during battery operation and jointly adhere to the positive and negative electrode surfaces to maintain their interface smoothness, thereby promoting battery cycle stability.

[0008] Specifically, the first additive (compound of formula 1) undergoes esterification to generate a long-chain hydrocarbon polymer and byproducts Li₂SO₄ and Li₂CO₃. Li₂SO₄ possesses the ability to oxidize other unsaturated groups (e.g., carbon-carbon triple bonds C≡C), thus promoting the polymerization reaction of other additives. Li₂CO₃ effectively weakens the reductive decomposition of ethylene carbonate EC in the electrolyte at 0.75V and inhibits the formation of alkyl lithium carbonate at 0.6V, maintaining electrolyte stability and reducing Li₂O₃ concentration. + This reduces losses and improves the cycle stability of lithium-ion batteries.

[0009] Specifically, the second additive contains unsaturated alkynes at both ends of its structure. During polymerization, these unsaturated alkynes serve as polymerization sites to form a long-chain polymer. In actual charge and discharge processes, the second additive can be tightly anchored to the positive and negative electrode surfaces via C≡C without decomposition, maintaining interface flatness and mitigating the volume expansion and breakage issues of the silicon anode, thereby promoting battery cycle stability. However, when the concentration of the second additive reaches a certain level, its adsorption mode changes from horizontal to vertical, hindering lithium-ion migration, reducing the uniformity of the interfacial film, and resulting in increased impedance.

[0010] The Li2SO4 produced by the polymerization reaction of the first additive oxidizes the C≡C in the structure of the second additive, promoting its bond-breaking polymerization. At the same time, the reaction products are adsorbed on the interface, reducing the probability of vertical adsorption of the second additive. This improves the adverse effects of the second additive on the negative electrode structure, maintains interface flatness, improves the volume expansion and breakage problems of the silicon negative electrode, and enhances the fast charging cycle stability of the battery.

[0011] According to embodiments of this disclosure, the mass ratio of the first additive to the second additive is 1:(0.1-2), preferably 1:(0.1-1. This improves the smoothness of the battery interface, thereby enhancing the battery's fast-charging cycle performance.

[0012] According to embodiments of this disclosure, the battery further includes a third additive having the structure shown in Formula 2;

[0013] Among them, R 12 R 13 R 14 Each is independently selected from H, C1-C6 alkyl, and C2-C4 alkenyl, and R 12 R 13 R 14 Not simultaneously H, R 12 R 13 R 14 At least one of them contains a carbon-carbon double bond;

[0014] Or, R 12and R 12 The connected atoms together form a C2-C4 alkenyl group, R 13 R 14 Each is independently selected from H, C1-C6 alkyl, and C2-C4 alkenyl groups;

[0015] Or, R 12 and R 13 Together with the atoms bonded to them, they form C3-C8 cycloalkenyl groups, R 14 For H.

[0016] Specifically, R in the structure of the third additive 12 R 13 R 14 At least one of the additives contains a carbon-carbon double bond, which can undergo electropolymerization during battery operation and adhere to the negative electrode surface, maintaining the interface flatness of the negative electrode and thus promoting battery cycle stability. There are two main polymerization pathways: one is the breaking and repolymerization of the olefin group, with cyclic esters distributed at both ends of the polymer chain; the other is a low-degree polymerization method, where the CO bond preferentially breaks, followed by C=C parallel polymerization, resulting in a high molecular weight long-chain polymer. The second pathway is more stable than the first. However, excessive use of the third additive can generate a large amount of long-chain polymer, hindering lithium-ion transport and significantly increasing the interfacial charge transfer impedance. The first additive in this application can mitigate the adverse effects of the third additive on lithium-ion transport, ultimately ensuring stable long-cycle and high-temperature storage performance of the battery. That is, the third additive, combined with the first and second additives, can further maintain the battery interface flatness, achieving the effect of improving the battery's fast-charge cycle stability.

[0017] According to embodiments of this disclosure, R 12 R 13 R 14 Each is independently selected from H, C1-C4 alkyl, and C2-C4 alkenyl, and R 12 R 13 R 14 Not simultaneously H, R 12 R 13 R 14 At least one of them contains a carbon-carbon double bond;

[0018] Or, R 12 and R 12 The connected atoms together form a C2-C4 alkenyl group, R 13 R 14 Each is independently selected from C1-C4 alkyl and C2-C4 alkenyl groups;

[0019] Or, R 12 and R 13 Together with the atoms attached to them, they form C7-C8 cycloalkenyl groups, R14 H represents the surface smoothness of the battery interface, thereby improving the battery's fast-charging cycle performance.

[0020] According to embodiments of this disclosure, R 12 R 13 R 14 Each is independently selected from H, C1 alkyl, and C2 alkenyl, and R 12 R 13 R 14 Not simultaneously H, R 12 R 13 R 14 At least one of them contains a carbon-carbon double bond;

[0021] Or, R 12 and R 12 The connected atoms together form a C2 alkenyl group, R 13 R 14 Each is independently selected from C1 alkyl and C2 alkenyl groups;

[0022] Or, R 12 and R 13 Together with the atoms attached to them, they form C7 cycloalkenyl groups, R 14 H represents the surface smoothness of the battery interface, thereby improving the battery's fast-charging cycle performance.

[0023] According to embodiments of this disclosure, the third additive comprises at least one of the following compounds:

[0024] This can improve the flatness of the battery interface, thereby enhancing the battery's fast-charging cycle performance.

[0025] According to embodiments of this disclosure, the mass ratio of the first additive, the second additive, and the third additive is 1:(0.1-2):(0.1-1), preferably 1:(0.1-1):(0.1-0.2). This improves the smoothness of the battery interface, thereby enhancing the battery's fast-charging cycle performance.

[0026] According to embodiments of this disclosure, the battery includes an electrolyte, and the first additive accounts for 0.05-5% of the total mass of the electrolyte, preferably 0.1-1%. This improves the smoothness of the battery interface, thereby enhancing the battery's fast-charging cycle performance.

[0027] According to embodiments of this disclosure, the second additive accounts for 0.05-1% of the total mass of the electrolyte, preferably 0.1-0.4%. This improves the smoothness of the battery interface, thereby enhancing the battery's fast-charging cycle performance.

[0028] According to embodiments of this disclosure, based on the total mass of the electrolyte, the mass percentage of the third additive is 0.01-0.5%, preferably 0.05-0.1%. This improves the smoothness of the battery interface, thereby enhancing the battery's fast-charging cycle performance.

[0029] According to embodiments of this disclosure, the electrolyte further includes a lithium salt, which includes at least one selected from lithium hexafluorophosphate and lithium bisfluorosulfonylimide. This can reduce battery gas production and improve battery cycle performance.

[0030] According to embodiments of this disclosure, the lithium salt comprises lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide, wherein the mass ratio of lithium hexafluorophosphate to lithium bis(fluorosulfonyl)imide is (2-5):1. This can reduce battery gas production and improve battery cycle performance.

[0031] According to embodiments of this disclosure, the battery further includes a positive electrode active material, which includes lithium iron phosphate material, LiCoO2 material, lithium-rich manganese-based material (aLi2MnO3·(1-a)LiMO2), and LiNi x Co y Mn z O2 materials, lithium nickel manganese oxide (LiNi) 0.5 Mn 1.5 O4) materials, lithium manganese iron phosphate materials (LiFe) b Mn 1-b PO4), wherein 0≤a≤1, 0≤b≤1, x+y+z=1, and M includes at least one of Ni, Co, and Mn. This improves the cycle performance of the battery.

[0032] According to embodiments of this disclosure, the battery is a cylindrical battery.

[0033] According to embodiments of this disclosure, the cylindrical battery is an 18650 cylindrical battery with an energy density of 230-250Wh / kg;

[0034] The positive electrode active material of the cylindrical battery is LiNi. x M 1-x O2, wherein M includes at least one of Co and Mn, and 0.8 ≤ x ≤ 0.9;

[0035] The negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one side surface of the negative current collector, wherein the mass percentage of silicon in the negative active material layer is 5%-8%.

[0036] Additional aspects and advantages of this disclosure will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this disclosure. Attached Figure Description

[0037] The above and / or additional aspects and advantages of this disclosure will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0038] Figure 1 shows SEM images of the negative electrode interface with different degrees of flatness according to this disclosure.

[0039] Detailed description of the invention

[0040] The embodiments of this disclosure are described in detail below. The embodiments described below are exemplary and are only used to explain this disclosure, and should not be construed as limiting this disclosure.

[0041] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this disclosure, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0042] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0043] To facilitate understanding of this disclosure, certain technical and scientific terms are specifically defined below. Unless otherwise expressly defined elsewhere in this document, all other technical and scientific terms used herein have the meanings commonly understood by one of ordinary skill in the art to which this disclosure pertains.

[0044] In this document, the terms “comprising” or “including” are open-ended expressions, meaning that they include the contents specified in this disclosure but do not exclude other contents.

[0045] The amount of electrolyte additives used is only a small part of the electrolyte in lithium-ion batteries, but an appropriate amount of additives can form an SEI on the surface of the negative electrode active material, referred to as an interface film in this application, which can reduce the problem of side reactions occurring after the negative electrode material comes into direct contact with the electrolyte.

[0046] However, silicon-based anodes suffer from poor conductivity, easy particle breakage, unstable SEI growth, and volume expansion. These problems ultimately lead to reduced coulombic efficiency and cycle life in silicon-based lithium-ion batteries, as well as poor fast-charge cycle capability. Therefore, regulating the electrolyte composition and improving the stability of the SEI film are crucial for enhancing the electrochemical performance of silicon-containing lithium-ion batteries.

[0047] In view of this, the present disclosure proposes a battery, including an electrolyte and a negative electrode, wherein the electrolyte includes a first additive and a second additive, the first additive having a structure shown in Formula 1; the second additive includes at least one selected from triargyl phosphate (CAS: 1779-34-6), (2-propynyl)dibutyl phosphate (CAS: 18687-46-2), and ethyl dipropion-2-alkynyl phosphate (CAS: 69695-73-4); the negative electrode includes a negative electrode active material, the negative electrode active material including silicon.

[0048] (CAS number: 2520352-90-1)

[0049] The battery disclosed herein includes an electrolyte and a silicon-containing negative electrode. The electrolyte includes a first additive and a second additive, which can undergo electropolymerization during battery operation and adhere to the surface of the negative electrode, maintaining the interface flatness of the negative electrode, improving the volume expansion and breakage problems of the silicon negative electrode, thereby promoting battery cycle stability.

[0050] Specifically, the second additive contains unsaturated alkynes at both ends of its structure. During polymerization, these unsaturated alkynes act as polymerization sites to form long-chain polymers. In actual charge and discharge processes, the C≡C at one end of the second additive is tightly anchored to the positive and negative electrode surfaces before polymerization occurs. This maintains interface flatness, improves the volume expansion and breakage issues of the silicon negative electrode, and thus promotes battery cycle stability. However, when the concentration of the second additive reaches a certain level, its adsorption mode changes from horizontal to vertical, hindering lithium ion migration and reducing the uniformity of the interface film, resulting in increased impedance and easy breakage of the negative electrode surface. The byproduct Li₂SO₄ of the first additive has the ability to oxidize other unsaturated groups (e.g., C=C, C≡C), thereby further promoting the polymerization reaction. For example, Li₂SO₄ oxidizes the C≡C in the structure of the second additive, promoting bond-breaking polymerization and reducing the probability of vertical adsorption. This mitigates the adverse effects of the second additive on the negative electrode interface, ensuring stable long-cycle and high-temperature storage performance of the battery.

[0051] According to specific embodiments of this disclosure, the mass ratio of the first additive to the second additive is 1:(0.1-2). Excessive use of the first additive results in a relatively high lithium carbonate content inside the battery, leading to CO2 shuttling back and forth and severe gas generation in the system. Excessive use of the second additive significantly increases the probability of its direct vertical adsorption at the interface, thereby affecting the desolvation and migration of lithium ions and negatively impacting the stability of the negative electrode surface structure. The ratio can be selected according to actual needs. As some specific examples, the mass ratio of the first additive to the second additive can be 1:0.1, 1:0.5, 1:1, 1:2, etc., preferably 1:(0.1-1). This can improve the flatness of the battery interface, thereby enhancing the battery's fast-charging cycle performance.

[0052] The electropolymerization process of compound 1 during battery operation is as follows:

[0053] Compound of Formula 1 undergoes the removal of its ester group to generate a long-chain hydrocarbon polymer and byproducts Li₂SO₄ and Li₂CO₃. Li₂SO₄ possesses the ability to oxidize other unsaturated groups (e.g., C≡C), which can promote the polymerization reaction of other additives. Li₂CO₃ can effectively reduce the reductive decomposition of ethylene carbonate in the electrolyte at 0.75V and inhibit the formation of alkyl lithium carbonate at 0.6V, maintaining electrolyte stability, reducing lithium-ion loss, and improving the cycle stability of lithium-ion batteries.

[0054] Specifically, the second additive includes at least one of triargyl phosphate, (2-propynyl)dibutyl phosphate, and ethyl diprop-2-ynyl phosphate.

[0055] According to specific embodiments of this disclosure, the second additive comprises triargyl phosphate (TPP). TPP is oxidized (loses electrons) before contact with the main solvent. The acidic corrosive substance F in the electrolyte has strong electronegativity and attacks the carbon nucleus of TPP, causing the π bond in C≡C to break, thereby forming a CF covalent bond, which undergoes a chain addition reaction at the positive electrode. When TPP gains electrons, the H protons in the electrolyte, due to their strong electrophilicity, approach the alkynyl electron cloud of the p orbital, forming a CH covalent bond, which then undergoes a chain addition reaction at the negative electrode.

[0056] According to a specific embodiment of this disclosure, the battery further includes a third additive having the structure shown in Formula 2;

[0057] Among them, R 12 R 13 R 14 Each is independently selected from H, C1-C6 alkyl, and C2-C4 alkenyl, and R 12 R 13 R14 Not simultaneously H, R 12 R 13 R 14 At least one of them contains a carbon-carbon double bond; or, R 12 and R 12 The connected atoms together form a C2-C4 alkenyl group, R 13 R 14 Each is independently selected from H, C1-C6 alkyl, C2-C4 alkenyl; or, R 12 and R 13 Together with the atoms bonded to them, they form C3-C8 cycloalkenyl groups, R 14 For H.

[0058] Specifically, the polymerization reaction of the third additive can be divided into two types: (1) R in the structure of the third additive 12 and R 13 At least one of the atoms contains a carbon-carbon double bond, which can serve as a polymerization site, i.e., the olefin bond breaks before polymerization. Cyclic esters are distributed at both ends of the polymer chain. This pathway can be detected by FTIR spectroscopy (Fourier Transform Infrared Spectroscopy) at 1795 cm⁻¹. -1 (C=O) and 1063cm -1 (CO) showed stable peaks, which was verified; (2) The C=O bond in the structure of the third additive was broken, and then the carbon-carbon double bond was polymerized side by side to obtain a large amount of long-chain polymer. Compared with the first polymerization method, the degree of polymerization of the polymer obtained by this polymerization method is lower, but the polymerization reaction is more stable. The polymer obtained after the reaction will adhere to the surface of the positive and negative electrodes, protect the interface between the positive and negative electrodes to maintain flatness, thereby promoting the stability of battery cycle.

[0059] According to specific embodiments of this disclosure, R 12 R 13 R 14 Each is independently selected from H, C1-C4 alkyl, and C2-C4 alkenyl, and R 12 R 13 R 14 Not simultaneously H, R 12 R 13 R 14 At least one of them contains a carbon-carbon double bond; or, R 12 and R 12 The connected atoms together form a C2-C4 alkenyl group, R 13 R 14 Each is independently selected from C1-C4 alkyl or C2-C4 alkenyl; or, R 12 and R 13 Together with the atoms attached to them, they form C7-C8 cycloalkenyl groups, R 14The additive is H. This reduces the steric hindrance caused by excessively long carbon chains, thus mitigating the problem of low film formation efficiency at the material-electrolyte interface. Simultaneously, this additive can undergo polymerization reactions in two different ways to obtain long-chain polymers, which then adhere to the positive and negative electrode surfaces, protecting the interface between the positive and negative electrodes and maintaining its smoothness, thereby promoting battery cycle stability.

[0060] According to specific embodiments of this disclosure, R 12 R 13 R 14 Each is independently selected from H, C1 alkyl, and C2 alkenyl, and R 12 R 13 R 14 Not simultaneously H, R 12 R 13 R 14 At least one of them contains a carbon-carbon double bond; or, R 12 and R 12 The connected atoms together form a C2 alkenyl group, R 13 R 14 Each is independently selected from C1 alkyl, C2 alkenyl; or, R 12 and R 13 Together with the atoms attached to them, they form C7 cycloalkenyl groups, R 14 The additive is H. This further reduces the steric hindrance effect caused by excessively long carbon chains, thus mitigating the problem of low film formation efficiency at the material-electrolyte interface. Simultaneously, this additive can undergo polymerization reactions in two different ways to obtain long-chain polymers, which then adhere to the surfaces of the positive and negative electrodes, protecting the interface and maintaining its smoothness, thereby promoting battery cycle stability.

[0061] According to specific embodiments of this disclosure, the third additive includes at least one of the following compounds:

[0062] Specifically, the CAS number for Equation 3-1 is 142429-71-8, the CAS number for Equation 3-2 is 96548-13-9, the CAS number for Equation 3-3 is 25326-19-6, and the CAS number for Equation 3-4 is 4427-96-7.

[0063] Taking compound 3-4 as an example, its electropolymerization process during battery operation is as follows:

[0064] According to specific embodiments of this disclosure, the mass ratio of the first additive, the second additive, and the third additive is 1:(0.1-2):(0.1-1). Different additive ratios affect the adsorption of the actual polymerization product on the interfacial film surface. When there is too much of the first additive, the lithium carbonate content inside the battery is relatively high, which leads to CO2 shuttling back and forth and severe gas production in the system. When there is too much of the second additive, the probability of it being directly and vertically adsorbed at the interface is greatly increased, thereby affecting the desolvation and migration of lithium ions. When there is too much of the third additive, the excess molecules are difficult to polymerize and adsorb normally at the interface, the number of free molecules in the electrolyte increases, and the reaction mechanism may be mainly based on common redox reactions, producing gases such as CO2 and O2. The ratio can be selected according to actual needs. As some specific examples, the mass ratio of the first additive, the second additive, and the third additive can be 1:0.1:1, 1:1:0.2, 1:1:1, 1:0.1:0.1, 1:2:0.1, 1:2:1, etc., preferably 1:(0.1-1):(0.1-0.2). This can improve the smoothness of the interface and enhance the fast charging cycle performance of the battery.

[0065] According to specific embodiments of this disclosure, the battery includes an electrolyte, and the mass percentage of the first additive is 0.05-5% based on the total mass of the electrolyte, for example, 0.05%, 0.1%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc. When the content of the first additive is within the above range, electropolymerization can occur more effectively during battery operation, forming long-chain polymers that adhere to the positive and negative electrode surfaces, maintaining interface flatness, and achieving the effect of improving the fast-charging cycle stability of the battery. In some embodiments of this disclosure, the mass percentage of the first additive is 0.1-1% based on the total mass of the electrolyte.

[0066] According to specific embodiments of this disclosure, based on the total mass of the electrolyte, the mass percentage of the second additive is 0.05-1%, for example, 0.05%, 0.1%, 0.5%, 1%, etc. When the content of the second additive is within the above range, it can better undergo electropolymerization during battery operation, adhere to the positive and negative electrode surfaces, maintain interface flatness, and achieve the effect of improving the fast-charging cycle stability of the battery. Simultaneously, its combined use with the first additive can also mitigate the adverse effects of the second additive on battery interface stability, ensuring stable long-cycle and high-temperature storage performance of the battery. In some embodiments of this disclosure, based on the total mass of the electrolyte, the mass percentage of the second additive is 0.1-0.4%.

[0067] According to specific embodiments of this disclosure, based on the total mass of the electrolyte, the mass percentage of the third additive is 0.01-0.5%, for example, 0.01%, 0.05%, 0.1%, 0.5%, etc. When the content of the third additive is within the above range, it can better undergo electropolymerization during battery operation, forming long-chain polymers that adhere to the positive and negative electrode surfaces, maintaining interface flatness, and achieving the effect of improving the fast-charging cycle stability of the battery. Simultaneously, its combined use with the first and second additives can also ensure stable long-cycle and high-temperature storage performance of the battery. In some embodiments of this disclosure, based on the total mass of the electrolyte, the mass percentage of the third additive is 0.05-0.1%.

[0068] According to specific embodiments of this disclosure, the electrolyte further includes a lithium salt, which includes at least one selected from lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide. Therefore, adding this electrolyte to a lithium-ion battery can reduce battery gas production and improve the battery's cycle performance.

[0069] According to specific embodiments of this disclosure, the lithium salt includes lithium hexafluorophosphate and lithium difluorosulfonylimide, with a mass ratio of lithium hexafluorophosphate to lithium difluorosulfonylimide of (2-5):1. Therefore, simultaneously adding both lithium salts to the electrolyte can further reduce battery gas production and improve battery cycle performance. The mass ratio of lithium hexafluorophosphate to lithium difluorosulfonylimide can be 2:1, 3:1, 4:1, 5:1, etc. Thus, by controlling the ratio of the two lithium salts within the above range, adding this electrolyte to a lithium-ion battery can reduce battery gas production and improve battery cycle performance.

[0070] According to specific embodiments of this disclosure, the electrolyte further includes a solvent, which includes cyclic organic solvents and / or chain organic solvents.

[0071] Specifically, the cyclic organic solvent may include one or more of cyclic carbonates such as ethylene carbonate (EC) and propylene carbonate (PC), one or more of cyclic carboxylic acid esters such as γ-butyrolactone, γ-valerolactone, and ε-caprolactone, one or more of cyclic ethers such as tetrahydrofuran, 3-methyltetrahydrofuran, 1,3-dioxapentane, and 1,4-dioxapentane, and one or more of chain sulfone compounds such as dimethyl sulfone, monofluoromethylmethyl sulfone, and trifluoromethyl isopropyl sulfone.

[0072] Specifically, the chain organic solvent may include one or more linear carbonates such as dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and methyl propyl carbonate (MPC); one or more linear carboxylic acid esters such as methyl acetate, ethyl acetate, methyl propionate, and ethyl propionate; and one or more chain ethers such as diethyl ether, di(2-fluoroethyl) ether, and di(2,2-difluoroethyl) ether.

[0073] According to specific embodiments of this disclosure, the electrolyte may further include other additives selected from at least one of vinylene carbonate (VC), fluoroethylene carbonate (FEC), ethylene sulfate (DTD), 1,3-propanesulfonyl lactone (PS), vinyl sulfite (ES), and lithium difluorodioxanol phosphate (LiODFP). The conventional additives account for 0.5-5% of the electrolyte by mass, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc.

[0074] It should be noted that the conventional additives are the types of additives commonly used in the art, and those skilled in the art can select them according to actual needs, which will not be elaborated here. Furthermore, the features and advantages described for the electrolyte additives above also apply to this electrolyte, which will not be elaborated here.

[0075] According to specific embodiments of this disclosure, the battery further includes a positive electrode active material, which includes lithium iron phosphate material, LiCoO2 material, lithium-rich manganese-based material (aLi2MnO3·(1-a)LiMO2), and LiNi x Co y Mn z O2 materials, lithium nickel manganese oxide (LiNi) 0.5 Mn 1.5 O4) materials, lithium manganese iron phosphate (LiFe) b Mn 1-b PO4), wherein 0≤a≤1, 0≤b≤1, x+y+z=1, and M includes at least one of Ni, Co, and Mn. This improves the cycle performance of the battery.

[0076] According to specific embodiments of this disclosure, the positive electrode active material includes LiNi. x M 1-x O2 (M is selected from at least one of Co and Mn, 0.8≤x≤0.9). This high-nickel ternary material is the preferred cathode material for current and future automotive power batteries due to its advantages such as low cost, high energy density, high reversible capacity, and environmental friendliness. Furthermore, the high-nickel ternary material, combined with the electrolyte disclosed herein, can further improve the battery's cycle stability under high voltage and reduce gas production. Specifically, x can be selected from 0.8, 0.85, 0.9, etc.

[0077] Typically, a battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0078] The positive electrode sheet includes a positive current collector and a positive active material layer disposed on at least one side surface of the positive current collector, wherein the positive active material layer includes the aforementioned positive active material.

[0079] In some embodiments of this disclosure, the positive current collector may include a metal foil or a composite positive current collector. For example, the metal foil may be aluminum foil. The composite positive current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. For example, the composite negative current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, etc.) on a polymer substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc.).

[0080] In some embodiments of this disclosure, the positive electrode active material layer may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0081] In some embodiments of this disclosure, the positive electrode active material layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0082] In some embodiments of this disclosure, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, and binder, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto a positive current collector, and then obtaining the positive electrode sheet after drying, cold pressing, and other processes.

[0083] The negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one side surface of the negative current collector, wherein the negative active material layer includes a negative active material.

[0084] In some embodiments of this disclosure, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc.).

[0085] In some embodiments of this disclosure, the negative electrode active material may be a silicon-containing active material known in the art for use in batteries. As an example, it may include at least one of the following materials: elemental silicon, silicon oxides, silicon-carbon composites, CVD silicon, combined with at least one carbon material such as natural graphite, artificial graphite, soft carbon, hard carbon, mesophase carbon microspheres, or nanocarbon, wherein the mass percentage of silicon in the negative electrode active material layer is 5%-8%.

[0086] In some embodiments of this disclosure, the negative electrode active material layer may optionally include a binder. The binder may include 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).

[0087] In some embodiments of this disclosure, the negative electrode active material layer may optionally include a conductive agent. The conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0088] In some embodiments of this disclosure, the negative electrode active material layer may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0089] In some embodiments of this disclosure, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto a negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0090] This disclosure does not impose any particular restrictions on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0091] In some embodiments of this disclosure, the material of the separator may include at least one of glass fiber, nonwoven fabric, polyolefin film, aromatic polyamide film, polytetrafluoroethylene film, and polyethersulfone film. In some embodiments of this disclosure, the thickness of the separator may be 10 μm-12 μm, for example, 10 μm, 11 μm, 12 μm, etc.

[0092] In some embodiments of this disclosure, the battery is a cylindrical battery, which includes the electrolyte, positive electrode active material and negative electrode active material described above.

[0093] In some embodiments of this disclosure, the cylindrical battery is an 18650 cylindrical battery with an energy density of 230-250 Wh / kg;

[0094] The positive electrode active material of the cylindrical battery is LiNi. x M 1-x O2, wherein M includes at least one of Co and Mn, and 0.8 ≤ x ≤ 0.9;

[0095] The negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one side surface of the negative current collector, wherein the mass percentage of silicon in the negative active material layer is 5%-8%.

[0096] The aforementioned electrolyte and the positive and negative electrode active materials have good compatibility, which is beneficial to improving the electrochemical performance of the battery.

[0097] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0098] Example 1

[0099] 1. Electrolyte preparation: EC and DMC in a mass ratio of 3:7 were used as solvents. After mixing, lithium salt (LiPF6 and LiFSI), electrolyte additives, vinylene carbonate (VC) and 1,3-propanesulfonate lactone (PS) were added according to the mass fraction of each component. After mixing evenly, the electrolyte was obtained.

[0100] 2. Preparation of positive electrode sheet: LiNi 0.8 Co 0.1 Mn 0.1O2 positive electrode active material, conductive agent SuperP (conductive carbon black), carbon nanotubes, and binder PVDF (polyvinylidene fluoride) are mixed evenly in a mass ratio of 94:2.5:1.5:2 and vacuum stirred until a certain viscosity and uniform flowability are achieved. This slurry is then evenly coated onto both sides of an aluminum foil, and subsequently dried at 85℃, cold-pressed, trimmed, cut into sheets, slit, and vacuum-dried at 85℃ for 10 hours. After welding the electrode tabs, a product with an areal density of 30 mg / cm³ is produced. 2 Positive electrode plate;

[0101] 3. Negative electrode preparation: CVD silicon, graphite material, conductive agent SuperP (conductive carbon black, SP), thickener CMC (sodium carboxymethyl cellulose), and binder SBR (styrene-butadiene rubber latex) are thoroughly mixed in a mass ratio of 7.5:87:2:1.5:2 to form a uniform slurry. After coating both sides of copper foil, it is dried at 85℃, followed by cold pressing, edge trimming, cutting, and slitting. Finally, it is dried under vacuum at 85℃ for 12 hours, and the electrode tabs are welded to obtain a sheet with an areal density of 12 mg / cm³. 2 The negative electrode plate;

[0102] 4. Separator: A 9μm thick porous polyethylene polymer film is used as the substrate, and a 2μm adhesive coating is applied to both sides of the substrate.

[0103] 5. Battery Fabrication: The positive electrode, separator, and negative electrode are wound together to form a core. The separator is positioned between the positive and negative electrodes to provide insulation. The core is then placed in a casing (made of nickel-plated stainless steel), and the negative current collector is welded to the casing using laser welding. After drying, electrolyte is injected. Following a settling process, the cell is charged to 4.2V at 0.1C at 45°C to complete formation (forming a passivation layer), capacity testing, and other steps, thus completing the battery fabrication.

[0104] The lithium-ion battery preparation methods of Examples 2-28 and all comparative examples are the same as those of Example 1, except that the electrolyte composition is different, as shown in Table 1. Among them, additive 2-1 is propargyl phosphate, 2-2 is propyl bis(2-propynyl) phosphate, and 2-3 is ethyl bis(2-propynyl) phosphate.

[0105] The difference between Example 29 and Example 1 is that the positive electrode active material is different. The positive electrode active material of Example 29 is lithium iron phosphate (LiFePO4, LFP), and the actual slurry mixing ratio is LFP:SP:PVDF=95:2.5:2.5. The battery charge and discharge voltage range is 2-3.65V.

[0106] Table 1

[0107] In this context, " / " represents that it was not added.

[0108] The cycle performance and negative electrode interface of the lithium-ion batteries obtained in the examples and comparative examples were characterized, and the characterization results are shown in Table 2.

[0109] 1. Cyclic test: Charge the battery at 25℃ with a constant current of 1.5C to 4.3V, charge it at a constant voltage of 4.3V to the cutoff current of 0.05C, and then discharge the battery with a constant current of 1.0C. Repeat the charge and discharge cycle for 500 cycles. Record the discharge capacity of the 500th cycle and the 1st cycle. Divide the two values ​​to obtain the capacity retention rate.

[0110] 2. Interface Characterization: The battery was charged at 25℃ with a constant current of 1.5C to 4.3V, then charged at a constant voltage of 4.3V to a cutoff current of 0.05C. It was then discharged with a constant current of 1.0C. This charge-discharge cycle was repeated 100 times. The discharge capacity of the 100th cycle and the 1st cycle were recorded, and the capacity retention rate was obtained by dividing the two values. The battery was disassembled after 100 cycles, and a portion of the negative electrode was selected for SEM testing. Based on the smoothness of the interface, it was ultimately classified into four levels: L1, L2, L3, and L4, as detailed below:

[0111] L1 (Superior): The electrode sheet remains flat overall, with uniform particle size and no obvious large cracks;

[0112] L2 (Good): The electrode sheet has good overall flatness and no obvious particle separation boundary, but there are obvious large cracks in some areas;

[0113] L3 (Medium): Particle boundaries are distinct but not dense;

[0114] L4 (Poor): The lithium plating on the electrode surface is obvious, and it is severely fragmented. Large-scale delamination and powdering occur during disassembly.

[0115] Table 2

[0116] Analysis of experimental results:

[0117] As shown in Examples 1-19 and 30, the present disclosure combines the first additive and the second additive and adds them to the lithium-ion battery, resulting in a higher degree of interface smoothness and improved cycle performance. Compared to Examples 1-19, Example 30 increases the amount of the second additive, making the ratio of the first additive to the second additive exceed 1:(0.1-2). This causes the adsorption mode of the second additive to change from horizontal to vertical, hindering lithium-ion migration and reducing the uniformity of the interface film. Consequently, it leads to increased impedance and a more fragile negative electrode surface. Therefore, the test results of this example are worse than those of Examples 1-19, a conclusion also verified by the test results in Table 2. However, it is still better than Comparative Examples 1-6, indicating that the present disclosure, by combining the first additive and the second additive and adding them to the lithium-ion battery, still has significant advantages in terms of battery interface smoothness and cycle performance.

[0118] As shown in Examples 20-28 and 31-32, the addition of a third additive to the electrolyte further improves the interface smoothness and cycle performance of the battery. Compared to Examples 20-28, Example 31 increased the amount of the third additive, resulting in a ratio of first, second, and third additives exceeding 1:(0.1-2):(0.1-1). This makes it difficult for excess molecules to polymerize and adsorb properly at the interface, leading to an increase in free molecules in the electrolyte. The reaction mechanism is likely to be primarily a common redox reaction, producing gases such as CO2 and O2. Therefore, the test results of this example are worse than those of Examples 20-28, a conclusion also verified by the test results in Table 2. Example 32 simultaneously increased the amounts of both the second and third additives. Based on the aforementioned analysis, the test results of this example should also be worse than those of Examples 20-28, a conclusion also verified by the test results in Table 2. Meanwhile, the test results of Examples 31-32 are still better than those of Comparative Examples 1-6, indicating that the present disclosure of adding the first additive, the second additive and the third additive in combination to lithium-ion batteries still has significant advantages in terms of battery interface flatness and cycle performance.

[0119] As can be seen from Examples 1 and 29, under different cathode material systems, the combination of the first additive and the second additive results in a higher degree of flatness of the negative electrode interface of the battery, thus improving the cycle performance of the battery.

[0120] Compared to the embodiments, none of the solutions in Comparative Examples 1-6 improved the battery interface smoothness or battery cycle life. Among them, Comparative Example 6 was the solution without additives. Compared with Comparative Examples 1-5, it showed some improvement in battery cycle life, but it was still worse than the embodiments.

[0121] The embodiments and comparative examples disclosed herein tested the effects of different additive types and contents on battery performance, and the specific analysis is as follows:

[0122] (1) Compared with Comparative Example 1 and Examples 15-21, the first additive is missing, and only the second and third additives are contained. The second additive is more likely to undergo vertical adsorption, which hinders the migration of lithium ions and reduces the uniformity of the interface film, resulting in increased impedance. The third additive will be affected by this, with fewer sites for polymerization and adsorption, and a large amount of it will be free in the electrolyte, increasing the probability of side reactions at the interface, thereby damaging the flatness of the battery interface and reducing the cycle life of the battery.

[0123] Similarly, compared with Comparative Example 4 and Examples 1-28, adding only the second additive will also damage the smoothness of the battery interface and affect the battery cycle life.

[0124] (2) Compared with Comparative Example 2 and Examples 20-28, the second additive is missing and only the first additive and the third additive are present. The mechanism of obtaining LiF and interfacial adsorption film by HF attack on carbon-carbon triple bond cannot occur. The acidity will rise rapidly, affecting the stability of positive and negative electrodes and reducing the cycle life of battery.

[0125] Similarly, compared with Comparative Example 3 and Examples 1-20 and 22-24, adding only the first additive will also damage the smoothness of the battery interface and affect the battery cycle life.

[0126] Similarly, compared with Comparative Example 5 and Examples 15-21, adding only the third additive also disrupts the smoothness of the battery interface and reduces the cycle life of the battery.

[0127] In summary, combining the first and second additives disclosed herein can achieve better battery performance improvement than not adding the first additive or not adding the second additive. Furthermore, the addition of the third additive can further enhance the technical effect.

[0128] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this disclosure. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0129] Although embodiments of the present disclosure have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present disclosure. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present disclosure.

Claims

1. A battery, characterized in that, The device includes an electrolyte and a negative electrode sheet. The electrolyte includes a first additive and a second additive. The first additive has the structure shown in Formula 1. The second additive includes at least one of triargyl phosphate, propyl bis(2-propynyl) phosphate, and ethyl bis(2-propynyl) phosphate. The negative electrode sheet includes a negative electrode active material, which includes silicon.

2. The battery according to claim 1, characterized in that, The mass ratio of the first additive to the second additive is 1:(0.1-2), preferably 1:(0.1-1).

3. The battery according to claim 1, characterized in that, It also includes a third additive having the structure shown in Formula 2; Among them, R 12 R 13 R 14 Each is independently selected from H, C1-C6 alkyl, and C2-C4 alkenyl, and R 12 R 13 R 14 Not simultaneously H, R 12 R 13 R 14 At least one of them contains a carbon-carbon double bond; Or, R 12 and R 12 The connected atoms together form a C2-C4 alkenyl group, R 13 R 14 Each is independently selected from H, C1-C6 alkyl, and C2-C4 alkenyl groups; Or, R 12 and R 13 Together with the atoms bonded to them, they form C3-C8 cycloalkenyl groups, R 14 For H.

4. The battery according to claim 3, characterized in that, R 12 R 13 R 14 Each is independently selected from H, C1-C4 alkyl, and C2-C4 alkenyl, and R 12 R 13 R 14 Not simultaneously H, R 12 R 13 R 14 At least one of them contains a carbon-carbon double bond; Or, R 12 and R 12 The connected atoms together form a C2-C4 alkenyl group, R 13 R 14 Each is independently selected from C1-C4 alkyl and C2-C4 alkenyl groups; Or, R 12 and R 13 Together with the atoms attached to them, they form C7-C8 cycloalkenyl groups, R 14 For H.

5. The battery according to claim 3, characterized in that, R 12 R 13 R 14 Each is independently selected from H, C1 alkyl, and C2 alkenyl, and R 12 R 13 R 14 Not simultaneously H, R 12 R 13 R 14 At least one of them contains a carbon-carbon double bond; Or, R 12 and R 12 The connected atoms together form a C2 alkenyl group, R 13 R 14 Each is independently selected from C1 alkyl and C2 alkenyl groups; Or, R 12 and R 13 Together with the atoms attached to them, they form C7 cycloalkenyl groups, R 14 For H.

6. The battery according to claim 3, characterized in that, The third additive includes at least one of the following compounds:

7. The battery according to any one of claims 3-6, characterized in that, The mass ratio of the first additive, the second additive, and the third additive is 1:(0.1-2):(0.1-1), preferably 1:(0.1-1):(0.1-0.2).

8. The battery according to any one of claims 1-7, characterized in that, The battery includes an electrolyte, and the first additive accounts for 0.05-5% of the total mass of the electrolyte, preferably 0.1-1%.

9. The battery according to claim 8, characterized in that, Based on the total mass of the electrolyte, the mass percentage of the second additive is 0.05-1%, preferably 0.1-0.4%.

10. The battery according to claim 8, characterized in that, Based on the total mass of the electrolyte, the mass percentage of the third additive is 0.01-0.5%, preferably 0.05-0.1%.

11. The battery according to claim 8, characterized in that, The electrolyte also includes a lithium salt, which includes at least one of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide.

12. The battery according to claim 11, characterized in that, The lithium salt includes lithium hexafluorophosphate and lithium difluorosulfonylimide, wherein the mass ratio of lithium hexafluorophosphate to lithium difluorosulfonylimide is (2-5):

1.

13. The battery according to any one of claims 1-12, characterized in that, The battery also includes a positive electrode active material, which includes lithium iron phosphate material, LiCoO2 material, aLi2MnO3·(1-a)LiMO2 material, and LiNi. x Co y Mn z O2 materials, LiNi 0.5 Mn 1.5 O4 materials, LiFe b Mn 1-b At least one of the PO4 materials; Wherein, 0≤a≤1, 0≤b≤1, x+y+z=1, and M includes at least one of Ni, Co, and Mn.

14. The battery according to any one of claims 1-13, characterized in that, The battery is a cylindrical battery.

15. The battery according to claim 14, characterized in that, The cylindrical battery is an 18650 cylindrical battery with an energy density of 230-250Wh / kg; The positive electrode active material of the cylindrical battery is LiNi. x M 1-x O2, wherein M includes at least one of Co and Mn, and 0.8 ≤ x ≤ 0.9; The negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one side surface of the negative current collector, wherein the mass percentage of silicon element in the negative active material layer is 5%-8%.

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