Lithium ion battery and application thereof

Abstract

The invention belongs to the technical field of batteries, and particularly discloses a lithium ion battery and application thereof. The lithium ion battery comprises a positive pole piece, a negative pole piece and an electrolyte, the positive pole piece comprises a nickel-containing positive pole material, the negative pole piece comprises a negative pole active material, the negative pole active material comprises a silicon element, the mass percentage content of the silicon element is 2-30% based on the total mass of the negative pole active material, and the electrolyte comprises a first additive and a second additive. The lithium ion battery provided by the invention is beneficial to improving the cycle performance and improving the high-temperature storage performance.

Description

Technical Field

[0001] The present application relates to the field of batteries, and in particular to a lithium-ion battery and its applications. Background Art

[0002] With the development of new energy technologies, batteries are being used in more and more applications, such as in mobile phones, laptops, electric vehicles, electric cars, energy storage devices, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes, and power tools. This places increasingly higher demands on battery performance. Summary of the Invention

[0003] The present application provides a lithium-ion battery and its application. The battery generates a solid electrolyte interface film with stable properties and appropriate thickness on the surface of nickel-containing positive electrode materials and silicon-based negative electrode materials. The interface film can effectively inhibit the decomposition of the electrolyte and improve the high-temperature storage performance and cycle performance of the battery.

[0004] To achieve the above technical objectives, the first aspect of the present application is to disclose a lithium-ion battery, which includes a positive electrode sheet, a negative electrode sheet and an electrolyte;

[0005] The positive electrode sheet comprises a nickel-containing positive electrode material;

[0006] The negative electrode plate includes a negative electrode active material, wherein the negative electrode active material includes silicon, and the mass percentage content of silicon is 2% to 30% based on the total mass of the negative electrode active material;

[0007] The electrolyte includes a first additive and a second additive;

[0008] The structural formula of the first additive is as follows:

[0009]

[0010] In formula I and formula II, X is independently selected from substituted or unsubstituted C1-C10 alkylene,

[0011] Any one of; the substituted substituent is selected from halogen;

[0012] wherein R1 and R2 are independently selected from any one or more of halogen, substituted or unsubstituted C1-C5 alkoxy, substituted or unsubstituted C1-C5 alkyl; and the substituted substituent is selected from halogen;

[0013] The structural formula of the second additive is any one or more of the following formulas III and IV, or a fluorinated sulfonyl imide salt:

[0014]

[0015] In formula III, m represents a positive integer from 1 to 3, R 11 、R 12 Each independently selected from any one or more of hydrogen, halogen, C1-C4 alkyl, cyclic carbonate group, cyclic sulfate group, and cyclic sulfate-substituted cyclic carbonate group;

[0016] In Formula IV, R 21 、R 22 Each is independently selected from any one or more of hydrogen, halogen, and C1-C4 alkyl.

[0017] In some embodiments, the above formula I includes any one or more of the following compounds:

[0018]

[0019]

[0020] And / or, the above formula II includes any one or more of the following compounds;

[0021]

[0022] And / or, the above formula III includes any one or more of the following compounds;

[0023]

[0024]

[0025] And / or, the above formula IV includes any one or more of the following compounds;

[0026]

[0027] In some embodiments, based on the total mass of the electrolyte, the mass percentage content of the first additive is 0.1% to 5%;

[0028] And / or, based on the total mass of the electrolyte, the mass percentage content of the second additive is 0.1% to 5%.

[0029] In some embodiments, the fluorine-containing sulfonyl imide salt includes any one or more of lithium bis(fluorosulfonyl)imide LiFSI (LiN(SO2F)2) and lithium bis(trifluoromethanesulfonyl)imide LiTFSI (LiN(SO2CF3)2).

[0030] In some embodiments, the single-sided coating density of the negative electrode sheet is 50 g / m 2 ~200g / m 2 ;

[0031] And / or, the compaction density of the negative electrode sheet is 1.50 g / cm 3 ~1.75g / cm 3 .

[0032] In some embodiments, the negative electrode active material includes a silicon-based negative electrode material, and the silicon-based negative electrode material includes any one or more of nano-silicon, silicon-oxygen material, silicon-carbon material, and silicon alloy;

[0033] The average particle size of the silicon-based negative electrode material is 5 μm to 10 μm.

[0034] In some embodiments, the negative electrode active material includes a carbonaceous material, and the carbonaceous material includes graphite.

[0035] In some embodiments, the nickel-containing positive electrode material includes any one or more of lithium nickelate, lithium nickel manganeseate, and lithium nickel cobalt manganese oxide.

[0036] In some embodiments, the nickel-containing positive electrode material includes lithium nickel cobalt manganese oxide, and the molar percentage of the nickel element is greater than 50% and less than 95% based on the total molar number of transition metals in the lithium nickel cobalt manganese oxide.

[0037] A second aspect of the present application is to provide a battery device, which includes the lithium-ion battery described in the first aspect.

[0038] Beneficial technical effects of this application:

[0039] In order to take into account the stability of the battery during the cycle and storage process, this application chooses to add a first additive and a second additive to the electrolyte, and generates a solid electrolyte interface film with stable properties and appropriate thickness on the surface of the nickel-containing positive electrode material and the silicon-based negative electrode material. This interface film isolates the nickel-containing positive electrode material and the silicon-based negative electrode material from the electrolyte, reduces the decomposition and gas production of the electrolyte, and thus improves the cycle performance and high-temperature storage performance of the battery.

[0040] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. DETAILED DESCRIPTION

[0041] The following describes specific embodiments of the battery device and power-consuming device of the present application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially identical structures may be omitted. This is to avoid unnecessary redundancy and to facilitate understanding by those skilled in the art. Furthermore, the following description is provided to facilitate a thorough understanding of the present application by those skilled in the art and is not intended to limit the subject matter of the claims.

[0042] The "ranges" disclosed herein are defined in terms of lower and upper limits, where a given range is defined by selecting a lower limit and an upper limit, and the selected lower and upper limits define the boundaries of the particular range. Ranges defined in this manner can be inclusive or exclusive and can be combined arbitrarily, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise indicated, the numerical range "a to b" is a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0043] Unless otherwise specified, in this application, the terms "first", "second", etc. are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0044] Secondary batteries have been widely used in various products due to their advantages such as long cycle life, safety and reliability. In recent years, with the significant increase in demand for batteries as energy sources, higher requirements have been placed on battery performance such as energy density, cycle stability and storage life.

[0045] Based on the above considerations, in order to improve the energy density, cycle stability and storage life of the battery, the present application conducted relevant experimental research and obtained a lithium-ion battery, in which the positive electrode plate includes a nickel-containing positive electrode material, and the negative electrode plate includes a silicon-based negative electrode material, and the silicon-based negative electrode material includes silicon element to ensure the energy density of the battery. At the same time, in order to take into account the stability of the battery during circulation and storage, the present application selects the electrolyte to include a first additive and a second additive. These components generate a solid electrolyte interface film with stable properties and appropriate thickness on the surface of the nickel-containing positive electrode material and the silicon-based negative electrode material. The interface film isolates the nickel-containing positive electrode material and the silicon-based negative electrode material from the electrolyte, reduces the decomposition and gas production of the electrolyte, and thereby improves the electrochemical stability of the battery.

[0046] In some embodiments, the lithium-ion battery of the present application is used in electrical devices, including electric vehicles, electric ships, electric aircraft, electric tools, communication base stations, etc.

[0047] In some embodiments, a lithium-ion battery generally includes an electrode assembly. The electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a separator, which is disposed between the negative electrode sheet and the positive electrode sheet. During the charge and discharge process of the lithium-ion battery, active ions (such as lithium ions) are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet. The separator is disposed between the positive electrode sheet and the negative electrode sheet to prevent a short circuit between the positive and negative electrodes while allowing active ions to pass through.

[0048] In some embodiments, the present application discloses a lithium-ion battery comprising a positive electrode sheet, a negative electrode sheet, and an electrolyte; the positive electrode sheet comprises a nickel-containing positive electrode material, the negative electrode sheet comprises a negative electrode active material, the negative electrode active material comprises silicon, and the mass percentage of silicon is 5% to 50% based on the total mass of the negative electrode active material; the electrolyte comprises a first additive and a second additive;

[0049] The structural formula of the first additive is as follows:

[0050]

[0051] In formula I and formula II, X is independently selected from substituted or unsubstituted C1-C10 alkylene,

[0052] Any one of; the substituted substituent is selected from halogen;

[0053] wherein R1 and R2 are independently selected from any one or more of hydrogen, halogen, substituted or unsubstituted C1-C5 alkoxy, substituted or unsubstituted C1-C5 alkyl; and the substituted substituent is selected from halogen;

[0054] The structural formula of the second additive is the structural formula shown in the following formula III, IV, or any one or more of the fluorinated sulfonyl imide salts:

[0055]

[0056] In formula III, m represents a positive integer from 1 to 3, R 11 、R 12 Each independently selected from any one or more of hydrogen, halogen, C1-C4 alkyl, cyclic carbonate group, cyclic sulfate group, and cyclic sulfate-substituted cyclic carbonate group;

[0057] In Formula IV, R 21 、R 22 Each is independently selected from any one or more of hydrogen, halogen, and C1-C4 alkyl.

[0058] The nickel-containing positive electrode material of the present application is a positive electrode active material. The positive electrode material can be purchased through commercial channels, and the purchased product has its elemental composition indicated; further, the components of the positive electrode material of the present application can also be detected by chemical analysis detection methods commonly used in this field, including but not limited to: complexation titration, precipitation weight method, redox method, difference method, plasma emission spectroscopy, atomic absorption spectroscopy, etc.

[0059] The silicon-based negative electrode material of the present application is a negative electrode active material. The negative electrode active material can be purchased through commercial channels, and the purchased products have their elemental composition indicated; further, the components of the negative electrode active material of the present application can also be detected by chemical analysis detection methods commonly used in this field.

[0060] The mass percentage of silicon in the negative electrode active material of the present application is 2% to 30%. By controlling the appropriate silicon content, the battery energy density is improved while also taking into account the side reaction between silicon and the electrolyte.

[0061] The present application discloses in these embodiments that the mass percentage content of silicon element in the negative electrode active material is 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30% or any one of the values ​​satisfying any two of the above ranges.

[0062] The compounds and derivatives provided herein can be named according to the IUPAC (International Union of Pure and Applied Chemistry) or CAS (Chemical Abstracts Service, Columbus, OH) nomenclature system.

[0063] "Substitution" means that the hydrogen atoms in a molecule are replaced by other different atoms or molecules. The "substitution" is selected from halogen, which includes any one or more of fluorine, chlorine, bromine and iodine.

[0064] The minimum and maximum carbon atom content of a hydrocarbon group is indicated by a prefix. For example, the prefix C1-Cb alkyl indicates any alkyl group containing from "a" to "b" carbon atoms. Thus, for example, "C1-C10 alkylene" refers to an alkylene group containing 1 to 10 carbon atoms, and "C1-C4 alkyl" refers to an alkyl group containing 1 to 4 carbon atoms.

[0065] "Alkyl" refers to a saturated hydrocarbon chain having a specified number of member atoms. For example, C1-4 alkyl refers to a saturated hydrocarbon chain having 1 to 4 member atoms. Alkyl groups can be straight or branched. Representative branched alkyl groups have one, two, or three branches. Alkyl groups can be optionally substituted with one or more substituents as defined herein. Alkyl groups include, but are not limited to, methyl, ethyl, propyl (n-propyl and isopropyl), butyl (n-butyl, isobutyl, and tert-butyl), and the like.

[0066] "Alkylene" is compared to "alkyl". Compared with alkyl, alkylene is a group with two connection sites formed by removing two hydrogen atoms from an alkane molecule, such as methylene. Ethylene wait.

[0067] "Alkoxy" refers to a substituent relative to an alkyl group, consisting of an alkyl group and an oxygen atom, such as methoxy, ethoxy, or propoxy.

[0068] "Cyclic phosphate" refers to a compound containing a phosphate group and having one or more cyclic structures.

[0069] "Cyclic sulfate" refers to a compound containing a sulfate group and having one or more cyclic structures.

[0070] "Cyclic carbonate" refers to a compound containing a carbonate group and having one or more cyclic structures.

[0071] Refers to the attachment site, used to connect to other molecules to be connected.

[0072] The positive electrode plate in the lithium-ion battery of the present application includes a nickel-containing positive electrode material, and the negative electrode plate includes a silicon-based negative electrode material, which is used to improve the energy density of the battery. At the same time, in order to take into account the stability of the battery during cycling and storage, the present application selects the electrolyte to include a first additive and a second additive. These components form a solid electrolyte interface film with stable properties and appropriate thickness (for example, a few nanometers) on the surface of the nickel-containing positive electrode material and the silicon-based negative electrode material. This interface film isolates the nickel-containing positive electrode material and the silicon-based negative electrode material from the electrolyte, reducing the decomposition and gas production of the electrolyte, thereby improving the battery's cycling performance and high-temperature storage performance.

[0073] The first additive in the electrolyte of the present application is convenient for taking effect in the nickel-containing positive electrode material. Specifically, the first additive preferentially dissolves on the positive electrode surface to form an interface film, reducing the occurrence of positive electrode side reactions. At the same time, the first additive can combine with the Ni element in the nickel-containing positive electrode material to stabilize the material structure, slow down the occurrence of phase change, inhibit the growth of interface impedance, and improve the high-temperature storage performance and cycle performance of the battery.

[0074] The second additive of the present application preferentially dissolves on the surface of the silicon-based negative electrode material and is reduced to generate organic or inorganic lithium salts containing sulfur-containing substances such as Li2SO3 and CH3CH(OSO2Li), thereby reducing the impedance of the SEI film on the surface of the silicon-based negative electrode material, inhibiting the occurrence of side reactions and the production of gases such as CO2, and improving the cycle stability of the battery; at the same time, these lithium salts have a good coordination relationship with the silicon-based negative electrode material, which is beneficial to improving the stability of the silicon-based interface, reducing the interface impedance, and improving the cycle performance of the battery.

[0075] The solid electrolyte interface film generated on the surface of the silicon-based negative electrode material in the present application contains inorganic substances such as phosphorus and sulfur. These inorganic substances themselves have a certain conductivity, which is beneficial to improving the conductivity between adjacent silicon-based negative electrode materials; therefore, the interface impedance of the negative electrode solid electrolyte interface film is low, which is beneficial to suppress the DCR growth during the cycle process, thereby further improving the long-term cycle stability of the battery.

[0076] However, when only one of the additives is added alone, the generated interface film is not stable enough, and when a single additive is added in excessive amounts, it is easy to deteriorate the performance of the battery. The present application selects the above-mentioned types of additives in combination, which can play a synergistic role in forming a stable and low-impedance positive electrode interface film on the surface of the nickel-containing positive electrode material and the silicon-based negative electrode material, which can effectively inhibit the decomposition of the electrolyte, reduce the gas production of the electrolyte decomposition, and improve the high-temperature storage performance of the battery. At the same time, the above-mentioned additives are used in combination to facilitate the continuous film-forming reaction, adjust the film-forming components, promote the formation of a low-impedance and stable interface film on the positive and negative electrode interfaces, inhibit the increase of the DC resistance DCR during the cycle, and improve the long-term cycle stability of the battery.

[0077] In some embodiments, the above formula I includes any one or more of the compounds shown in Table 1 below;

[0078] Table 1 Structures of some compounds of formula I

[0079]

[0080]

[0081] In some embodiments, the above formula II includes any one or more of the compounds shown in Table 2 below;

[0082] Table 2 Structure list of some compounds of formula II

[0083]

[0084]

[0085] In Table 2, “-” indicates that all are not listed.

[0086] In some embodiments, the above formula III includes any one or more of the compounds shown in Table 3 below;

[0087] Table 3 Structure list of some compounds of formula III

[0088]

[0089] In some embodiments, the above formula IV includes any one or more of the compounds shown in Table 4 below;

[0090] Table 4 Structures of some compounds of formula IV

[0091]

[0092] The sources of the first additive and the second additive in the present application include but are not limited to preparation and commercial sale. The present application provides examples of the preparation methods of some specific compounds.

[0093] 1. The preparation process of I-9 (2-fluoro-1,3,2-dioxaphosphorinane 2-oxide) is as follows:

[0094] S01: Add 76.7 g of phosphorus oxychloride and 100 ml of dichloromethane to a 500 mL three-necked flask, stir and dilute, cool to 15°C, add 37.9 g of 1,3-propylene glycol dropwise, add the entire amount of 1,3-propylene glycol after 60 min, raise the temperature to 25°C, and continue the reaction for 90 min to obtain a reaction solution containing 2-chloro-1,3,2-dioxaphosphorinane 2-oxide. Transfer the reaction solution to a 500 mL single-necked flask, concentrate under reduced pressure at 30°C and a vacuum of 3 kPa, remove the solvent dichloromethane, and obtain 74.3 g of 2-chloro-1,3,2-dioxaphosphorinane 2-oxide.

[0095] S02: The 2-chloro-1,3,2-dioxaphosphorinane 2-oxide obtained in step S01 was added to a 500 mL three-necked flask, and 300 mL of dimethyl carbonate was added with stirring and diluted. The temperature was controlled to 40° C. and 38.4 g of potassium fluoride was added in batches. After the addition of the raw materials, the reaction was carried out at 40° C. for 3 hours. Quantitative detection by GCMS (gas chromatography-mass spectrometry) showed that the residual amount of 2-chloro-1,3,2-dioxaphosphorinane 2-oxide was less than 10 ppm. The fluorination reaction solution was filtered through a Buchner funnel to remove solid salts, and the filtrate was removed from dimethyl carbonate at 40° C. and a vacuum of 1 kPa to obtain a crude product of 2-fluoro-1,3,2-dioxaphosphorinane 2-oxide, which was distilled under a high vacuum of 0.2 kPa to obtain 69.6 g of 2-fluoro-1,3,2-dioxaphosphorinane 2-oxide product with a purity of 99.75%.

[0096] 2. The preparation process of I-20 (3,9-difluoro-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane-3,9-dioxide) is as follows:

[0097] S01: Add 76.7 g of phosphorus oxychloride and 100 ml of trimethyl phosphate to a 500 mL three-necked flask, stir and dilute, cool to 15 ° C, vacuum control 50 kPa, add 33.9 g of pentaerythritol dropwise, add pentaerythritol after 60 minutes, heat to 25 ° C, and continue to react for 90 minutes to obtain a reaction solution containing 3,9-dichloro-2,4,8,10-tetraoxa-3,9-dithiaspiro[5.5]undecane-3,9-dioxide. Transfer the reaction solution to a 500 mL single-necked flask, concentrate under reduced pressure at 50 ° C and vacuum 1 kPa to remove the solvent trimethyl phosphate to obtain 74.3 g of 3,9-dichloro-2,4,8,10-tetraoxa-3,9-dithiaspiro[5.5]undecane-3,9-dioxide;

[0098] S02: 3,9-dichloro-2,4,8,10-tetraoxa-3,9-dithiaspiro[5.5]undecane-3,9-dioxide obtained in step S01 was added to a 500 mL three-necked flask, and 300 mL of dimethyl carbonate was added and stirred for dilution. The temperature was controlled to 40° C. and 34.8 g of potassium fluoride was added in batches. After the addition of the raw materials, the mixture was reacted at 40° C. for 4 h. Quantitative detection by LC-MS (liquid chromatography-mass spectrometry) showed that 3,9-dichloro-2,4,8,10-tetraoxa-3,9-dithiaspiro[5.5]undecane-3,9 -The residual amount of dioxide is less than 10ppm; the fluorination reaction liquid is filtered through a Buchner funnel to remove solid salts, and the filtrate is removed from dimethyl carbonate at 40°C and a vacuum of 1kPa to obtain a crude 3,9-difluoro-2,4,8,10-tetraoxa-3,9-dithiaspiro[5.5]undecane-3,9-dioxide product, which is distilled under a high vacuum of 0.1Pa to obtain 53.6g of 3,9-difluoro-2,4,8,10-tetraoxa-3,9-dithiaspiro[5.5]undecane-3,9-dioxide product with a purity of 99.56%.

[0099] 3. The preparation process of II-9 (3,3,3,9,9,9-hexafluoro-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane) is as follows:

[0100] S01: Add 40.8g of pentaerythritol and 300mL of anhydrous dichloromethane to a 500mL three-necked flask. After nitrogen displacement, dissolve 90.6g of phosphorus trichloride in 80mL of dichloromethane and add dropwise at 15°C. After complete addition, heat and reflux at 40°C for 6 hours until gas production ceases. Cool the reaction mixture to room temperature, remove the dichloromethane using a rotary evaporator, and then distill under reduced pressure to yield 52.5g of the intermediate 3,9-dichloro-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane.

[0101] S02: To a 500 mL three-necked flask, add 25 g of the intermediate 3,9-dichloro-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane and 25 mL of anhydrous dichloromethane. Bubble chlorine at 10-0°C. Monitor the reaction progress with GC. Complete conversion is achieved in approximately 2 hours. Remove the dichloromethane by rotary evaporation to obtain 26.9 g of the intermediate 3,3,3,9,9,9-hexachloro-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane.

[0102] S03: Add 17.2 g of potassium fluoride and 100 mL of anhydrous acetonitrile to a 500 mL three-necked reaction flask. After nitrogen purge, add dropwise a mixture of 20 g of the intermediate 3,3,3,9,9,9-hexachloro-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane and 20 mL of anhydrous acetonitrile at 30°C. After addition, react at 80°C for 12 h. Monitor the reaction progress by GC until complete conversion of the starting material. Filter the reaction solution, and the filtrate is evaporated under reduced pressure to remove the acetonitrile. The residue is then distilled under reduced pressure to yield 12.11 g of the product 3,3,3,9,9,9-hexafluoro-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane.

[0103] 4. The preparation process of II-10 (2,2,2-trifluoro-1,3,2-dioxaphosphorinane) is as follows:

[0104] S01: Add 15.2g of 1,3-propylene glycol and 60mL of anhydrous dichloromethane to a 500mL three-necked flask. After nitrogen displacement, dissolve 30.21g of phosphorus trichloride in 40mL of dichloromethane and add dropwise at 15°C. After complete addition, heat and reflux at 40°C for 6 hours until gas production ceases. Cool the reaction mixture to room temperature, remove the dichloromethane using a rotary evaporator, and then distill under reduced pressure to yield 22.5g of the 2-chloro-1,3,2-dioxaphosphorinane intermediate.

[0105] S02: Add 22.5 g of the 2-chloro-1,3,2-dioxaphosphorinane intermediate and 25 mL of anhydrous dichloromethane to a 500 mL three-necked flask. Bubble chlorine gas at 10-0°C. Monitor the reaction progress with GC. Complete conversion is achieved in approximately 2 hours. Remove the dichloromethane by rotary evaporation to obtain 33.8 g of the 2,2,2-chloro-1,3,2-dioxaphosphorinane intermediate.

[0106] S03: Add 33.3 g of potassium fluoride and 100 mL of anhydrous acetonitrile to a 500 mL three-necked reaction flask. After nitrogen purge, a mixture of 33.8 g of the 2,2,2-chloro-1,3,2-dioxaphosphorinane intermediate and 20 mL of anhydrous acetonitrile was added dropwise at 30°C. After addition, the mixture was allowed to react at 80°C for 12 h. The reaction progress was monitored by GC until complete conversion of the starting material. The reaction solution was filtered, and the filtrate was evaporated under reduced pressure to remove the acetonitrile. The residue was then distilled under reduced pressure to yield 22.0 g of the 2,2,2-trifluoro-1,3,2-dioxaphosphorinane product.

[0107] This application only uses two compounds listed above as examples to describe their preparation methods. In fact, other specific compounds can be prepared or obtained commercially, and this application will not go into details here.

[0108] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the first additive is 0.1% to 5%.

[0109] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the second additive is 0.1% to 5%.

[0110] In these embodiments, the present application selects a certain mass ratio of the first additive and the second additive to facilitate the technical effect of the two synergistically enhancing the stability of the solid electrolyte interface film.

[0111] In these embodiments, the present application discloses that the mass percentage content of the above-mentioned first additive is any one of 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 2.0%, 3.0%, 4.0%, 5.0% or any one of the values ​​within any two of the above ranges.

[0112] In these embodiments, the present application discloses that the mass percentage content of the above-mentioned second additive is any one of 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 2.0%, 3.0%, 4.0%, 5.0% or any one of the values ​​within any two of the above ranges.

[0113] In some embodiments, the second additive includes a fluorine-containing sulfonyl imide salt, and the fluorine-containing sulfonyl imide salt includes any one or more of lithium bis(fluorosulfonyl)imide LiFSI (LiN(SO2F)2) and lithium bis(trifluoromethanesulfonyl)imide LiTFSI (LiN(SO2CF3)2).

[0114] The fluorinated sulfonyl imide salt of the present application has a high degree of ion dissociation and can form a large number of freely mobile lithium ions in the electrolyte, thereby improving the conductivity of the electrolyte. At the same time, the fluorinated sulfonyl imide salt also facilitates the formation of a stable solid electrolyte interface film on the surface of the silicon negative electrode material. The solid electrolyte interface film is not easy to decompose even at high temperatures, thereby improving the recycling effect of the battery by reducing the consumption of the electrolyte and the negative electrode material.

[0115] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the fluorine-containing sulfonyl imide salt is 0.1% to 20%.

[0116] The present application discloses in these embodiments that the mass percentage content of the above-mentioned fluorine-containing sulfonyl imide salt is any one of 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 2.0%, 3.0%, 4.0%, 5.0%, 6.0%, 7.0%, 8.0%, 9.0%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, or any one of the values ​​satisfying any two of the above ranges.

[0117] In some embodiments, the battery of the present application uses a liquid electrolyte, that is, an electrolyte. The electrolyte comprises an electrolyte salt and an organic solvent. The types of electrolyte salts include any conventional types in the art, for example, including but not limited to inorganic metal salts such as LiClO4, LiAsF6, LiPF6, LiBF4, LiSbF6, LiSO3F, etc.; fluorine-containing organic metal salts such as LiCF3SO3, LiN(FSO2)(CF3SO2), LiN(C2F5SO2)2, etc.

[0118] According to some embodiments of the present application, the concentration of the electrolyte salt in the electrolyte is 0.1 mol / L to 4 mol / L. In these embodiments, the present application discloses that the concentration of the electrolyte salt is any one of 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L, 2 mol / L, 2.2 mol / L, 2.5 mol / L, 2.8 mol / L, 3 mol / L, 3.2 mol / L, 3.5 mol / L, 3.8 mol / L, and 4 mol / L, or any one of the values ​​satisfying the above ranges.

[0119] In some embodiments, the organic solvent comprises any one or more of a carboxylate compound, a carbonate compound, and an ether compound. The carboxylate compound comprises one or more of ethyl acetate (EA), methyl acetate (MA), ethyl propionate (EP), propyl acetate (PA), methyl propionate (MP), methyl butyrate (MB), ethyl butyrate (EB), and 1,4-butyrolactone (GBL); the carbonate compound comprises one or more of ethylene carbonate (EC), propylene carbonate (PC), vinylene carbonate, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethyl methyl carbonate (EMC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), butylene carbonate (BC), and fluoroethylene carbonate (FEC). The ether compound comprises at least one of tetrahydrofuran, dimethyltetrahydrofuran, 1,2-dimethoxyethane, dipropylene glycol dimethyl ether, and dimethyl phthalate. The organic solvents of the present application further include one or both of nitrile solvents and sulfone solvents. Nitrile solvents include one or more of acetonitrile (AN), glutaronitrile (GLN), and adiponitrile (ADN). Sulfone solvents include at least one of sulfolane (SF), dimethyl sulfone (MSM), ethylmethyl sulfone (EMS), and diethyl sulfone (ESE), or a combination of two.

[0120] In some embodiments, the electrolyte further comprises a film-forming stabilizer, which includes one or more of vinylene carbonate (VC), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), vinyl ethylene carbonate (VEC) and dioctyl carbonate (CC).

[0121] In some embodiments, the single-sided coating density of the negative electrode sheet is 50 g / m 2 ~200g / m 2 .

[0122] In some embodiments, the compaction density of the negative electrode sheet is 1.50 g / cm 3 ~1.75g / cm 3 .

[0123] In some embodiments, the single-sided coating density of the positive electrode sheet is 100 g / m 2 ~300g / m 2 .

[0124] In some embodiments, the compaction density of the positive electrode sheet is 3.0 g / cm 3 ~3.6g / cm 3 .

[0125] The compaction density of the present application can be used to characterize the energy density of the material. The compaction density of the positive electrode film layer = the surface density of the positive electrode film layer / the thickness of the positive electrode film layer, and the compaction density of the negative electrode film layer = the surface density of the negative electrode film layer / the thickness of the negative electrode film layer. The thickness of the film layer includes the distance between the two end faces of the film layer along the thickness direction. The surface density of the positive electrode film layer = the weight of the single-sided positive electrode film layer / the area of ​​the single-sided positive electrode film layer. Similarly, the surface density of the negative electrode film layer = the weight of the single-sided negative electrode film layer / the area of ​​the single-sided negative electrode film layer. Among them, the weight of the single-sided positive electrode film layer or the weight of the single-sided negative electrode film layer can be obtained by weighing, and the area of ​​the single-sided positive electrode film layer or the area of ​​the single-sided negative electrode film layer can be obtained by using the area calculation formula according to the shape of the film layer. The present application mainly discusses the compaction density of the positive electrode film layer or the negative electrode film layer after formation and before recycling. Those skilled in the art know that the compaction density of the film layer will decrease with the use of the battery.

[0126] The present application discloses in these embodiments that the single-side coating density of the negative electrode sheet is 50 g / m 2 , 60g / m 2 , 70g / m 2 , 80g / m 2 , 90g / m 2 , 100g / m 2 , 110g / m 2 , 120g / m 2 , 130g / m 2 , 140g / m 2 , 150g / m 2 , 160g / m 2 , 170g / m 2 , 180g / m 2 , 190g / m 2 , 200g / m 2 Any one of the above two ranges or any one of the above two ranges.

[0127] The present application discloses in these embodiments that the compaction density of the negative electrode sheet is 1.50 g / cm 3 , 1.60g / cm 3 , 1.70g / cm 3 , 1.75g / cm 3 Any one of the above two ranges or any one of the above two ranges.

[0128] The present application discloses in these embodiments that the single-sided coating density of the positive electrode sheet is 100 g / m 2 , 110g / m 2 , 120g / m 2 , 130g / m 2 , 140g / m 2, 150g / m 2 , 160g / m 2 , 170g / m 2 , 180g / m 2 , 190g / m 2 , 200g / m 2 , 210g / m 2 , 220g / m 2 , 230g / m 2 , 240g / m 2 , 250g / m 2 , 260g / m 2 , 270g / m 2 , 280g / m 2 , 290g / m 2 , 300g / m 2 Any one of the above two ranges or any one of the above two ranges.

[0129] The present application discloses in these embodiments that the compacted density of the positive electrode sheet is 3.0 g / cm 3 , 3.1g / cm 3 、3.2g / cm 3 , 3.3g / cm 3 、3.4g / cm 3 , 3.5g / cm 3 、3.6g / cm 3 Any one of the above two ranges or any one of the above two ranges.

[0130] In some embodiments, the negative electrode active material includes a silicon-based negative electrode material, which includes any one or more of nano-silicon, silicon-oxygen material, silicon-carbon material, and silicon alloy; the average particle size of the silicon-based negative electrode material is 5 μm to 10 μm.

[0131] In some embodiments, the silicon-oxygen material includes, but is not limited to, any one or more of silicon oxide and silicon monoxide.

[0132] In some embodiments, the silicon-carbon material includes, but is not limited to, porous carbon and silicon grains supported in the porous carbon.

[0133] In some embodiments, silicon alloys include, but are not limited to, silicon-tin alloys.

[0134] In some embodiments, the present application discloses that the average particle size of the silicon-based negative electrode material is Dv50, and the test method for Dv50 includes any conventional determination method in the art. In these embodiments, the present application discloses that the average particle size of the above-mentioned silicon-based negative electrode material is any one of 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm, 9.5μm, and 10μm, or any one of the ranges of any two of the above.

[0135] In some embodiments, the negative electrode active material includes a carbonaceous material, and the carbonaceous material includes graphite.

[0136] The present application discloses in these embodiments that the graphite is artificial graphite, and the average particle size of the artificial graphite is 8 μm to 20 μm.

[0137] The present application also discloses in these embodiments that the artificial graphite comprises a porous structure with a pore volume of 1.0 cm 3 / g~3.0cm 3 / g.

[0138] The artificial graphite of the present applicant has a low expansion degree itself, and together with the silicon-based negative electrode material, it can easily alleviate the expansion problem of the silicon-based negative electrode material.

[0139] The present application discloses in some embodiments that a negative electrode plate includes a negative electrode film layer, the negative electrode film layer includes a negative electrode active material, the negative electrode active material includes a carbonaceous negative electrode material and a silicon-based negative electrode material, the negative electrode film layer also includes a conductive agent, the conductive agent includes one or more of a point conductive agent, a linear conductive agent, and a surface conductive agent, wherein the point conductive agent includes but is not limited to one or more of conductive carbon black (Super P or Super S), acetylene black, conductive graphite (KS-6 or KS-15 or SFG-6 or SFG-15), and Ketjen black, the linear conductive agent includes one or more of single-walled carbon nanotubes, multi-walled carbon nanotubes, and carbon nanofibers, and the surface conductive agent includes but is not limited to graphene.

[0140] In some embodiments, the present application discloses that the negative electrode film layer further comprises a binder and a dispersant, etc. The binder includes but is not limited to polyvinyl alcohol, polyethylene glycol, sodium carboxymethyl cellulose, polyethylene oxide, polyacrylic acid, polyacrylamide, sodium alginate, styrene-butadiene rubber (SBR), etc. The dispersant also includes any conventional type in the art, such as cellulose and its salts, specifically including but not limited to methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, etc.

[0141] The method for forming the negative electrode film layer of the present application includes mixing the above-mentioned raw materials with a solvent (such as deionized water) in a certain mass ratio to form a negative electrode slurry, defoaming the negative electrode slurry, and then evenly coating the negative electrode slurry on both sides of the negative electrode current collector; controlling the single-sided coating weight; drying, and compacting to a certain compaction density using a cold press to obtain a negative electrode sheet containing the negative electrode film layer.

[0142] In some embodiments, the nickel-containing positive electrode material includes any one or more of lithium nickelate, lithium nickel manganeseate, and lithium nickel cobalt manganese oxide.

[0143] In some embodiments, the nickel-containing positive electrode material includes lithium nickel cobalt manganese oxide, and the molar percentage of the nickel element is greater than 50% and less than 95% based on the total molar number of transition metals in the lithium nickel cobalt manganese oxide.

[0144] In some embodiments, the structural formula of the lithium nickel transition metal oxide is Li a Ni x Co y Mn z O2, x+y+z=1, a=0.8~1.2, x=0.50~0.95, y=0.05~0.45, z=0.05~0.45.

[0145] In some embodiments, the positive electrode sheet includes a positive electrode film layer, which includes the above-mentioned nickel-containing positive electrode material, and further includes a conductive agent, a binder, a dispersant, etc. The conductive agent includes but is not limited to any one or more of graphite, superconducting carbon, carbon black (such as acetylene black, Ketjen black, Super P, etc.), carbon dots, carbon nanotubes, graphene and carbon nanofibers. The binder includes but is not limited to polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, sodium alginate, polymethacrylic acid, carboxymethyl chitosan, etc. The dispersant includes sodium carboxymethyl cellulose, hydrogenated nitrile rubber, etc.

[0146] The positive electrode film layer of the present application is one layer or two layers or more. The present application will mainly use one layer as an example to illustrate in the subsequent specific embodiments, and will not make special emphasis or explanation in the subsequent application.

[0147] The current collector of the present application can be a metal foil or a composite current collector, wherein the metal foil can be an aluminum foil to serve as a positive electrode current collector, or the metal foil can be a copper foil to serve as a negative electrode current collector. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector can be formed by forming a metal material such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy on a polymer material substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE) and the like.

[0148] The method for forming the positive electrode film layer of the present application includes mixing the above-mentioned raw materials with a solvent (such as N-methylpyrrolidone) in a certain mass ratio to form a positive electrode slurry, and evenly coating the positive electrode slurry on both sides of the current collector; controlling a certain single-sided coating weight; after drying, using a cold press to compact to a certain compaction density, thereby obtaining a positive electrode sheet containing a positive electrode film layer.

[0149] Some embodiments of the present application disclose a lithium-ion battery including an isolation member. The present application does not particularly limit the type of isolation member, and any known porous structure isolation member with good chemical stability and mechanical stability can be selected.

[0150] In some embodiments, the spacer includes a base film layer.

[0151] In some embodiments, the isolation member includes a base film layer and an organic coating layer, wherein the organic coating layer is located on at least one side surface of the base film layer.

[0152] In some embodiments, this application discloses an organic coating disposed on both sides of a base film layer, with the organic coating facing the positive and negative electrode material layers of a lithium-ion battery. The organic coating has a saturated electrolyte absorption rate greater than that of the base film layer. This design facilitates sufficient and effective electrolyte infiltration into the active material layer.

[0153] In some embodiments, this application discloses an organic coating disposed on one surface of a base film layer and an inorganic coating disposed on the other surface, wherein the organic coating faces the negative electrode material layer of a lithium-ion battery, and the inorganic coating faces the positive electrode material layer. The organic coating of this application facilitates the effective and sufficient wetting of the negative electrode active material layer by the electrolyte, while the inorganic coating of this application provides insulation, reducing the probability of puncturing the separator and causing a short circuit.

[0154] The materials of the base film layer and the organic coating of the present application are independently selected from any one or more of polyethylene (PE), polypropylene (PP), polyparaphenylene terephthalamide (PPTA), polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), polyacrylonitrile (PAN), polyimide (PI) and polyamide (PA).

[0155] The inorganic coating of the present application includes a ceramic coating, and the ceramic particles in the ceramic coating include one or more of SiO2, Al2O3, AlOOH, CaO, TiO2, MgO, ZnO, ZrO2, Mg(OH)2 and BaSO4.

[0156] The battery of the present application will be described in detail below with reference to specific embodiments.

[0157] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0158] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0159] The present application can adopt conventional techniques of inorganic chemistry within the art. In the following examples, efforts have been made to ensure the accuracy of the numbers used (including amounts, temperatures, reaction times, etc.), but some experimental errors and deviations should be considered. The temperatures used in the following examples (in degrees Celsius) are expressed in ° C, and the pressures are atmospheric pressure or near atmospheric pressure. All pharmaceutical reagents were purchased as AR grade, and all reactions were carried out under argon protection. Unless otherwise noted, all reagents were obtained from commercial sources.

[0160] Experimental materials:

[0161] The materials of the positive electrode active material, the negative electrode active material, and various auxiliary materials and components are all commercially available.

[0162] Example 1

[0163] A method for preparing a lithium-ion battery is provided, comprising the following preparation process:

[0164] Preparation of positive electrode sheet:

[0165] Take lithium nickel cobalt manganese oxide LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), conductive carbon black (Super P), single-walled carbon nanotubes, and binder PVDF were mixed in a ratio of 96.5:1.5:0.5:1.5, and nitrogen methyl pyrrolidone solvent was added and stirred to form a positive electrode slurry. The positive electrode slurry was coated on both sides of the positive electrode current collector aluminum foil, and the single-sided coating surface density was 200g / m 2; Then roll compaction, compaction density is 3.4g / cm 3 ; Then it is divided into strips and slices. Finally, the positive electrode of the lithium-ion battery is obtained;

[0166] Preparation of negative electrode sheet:

[0167] The negative electrode active material (the negative electrode active material includes artificial graphite and silicon element, and the mass percentage content of silicon element is 9% based on the total mass of the negative electrode active material), conductive carbon black (Super P), single-walled carbon nanotubes, dispersant sodium carboxymethyl cellulose, binder polyacrylic acid (PAA), binder styrene-butadiene rubber (SBR) are dispersed in deionized water in a mass ratio of 95.1:0.5:0.1:0.3:2.8:1.2 to form a negative electrode slurry. The negative electrode slurry is evenly coated on the surface of the copper foil, and the single-sided coating density is 80g / m 2 ; Then roll compaction, compaction density is 1.55g / cm 3 Then it is divided into strips and slices to finally obtain the negative electrode of the lithium-ion battery.

[0168] Prepare the electrolyte:

[0169] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a mass ratio of 2:4:4, and lithium hexafluorophosphate (LiPF6) is added to dissolve into a 1.2M solution. Then, 0.5% by mass of vinylene carbonate (VC), 0.5% by mass of a first additive (I-9 in Table 1), and 0.5% by mass of a second additive (III-1 in Table 3) are added.

[0170] Isolators available:

[0171] A porous polyethylene (PE) film with a thickness of 13 μm was used as the separator.

[0172] Assembling lithium-ion batteries:

[0173] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, so that the separator is placed between the positive electrode sheet and the negative electrode sheet to play an isolating role, and the corresponding assembly forms a wound bare cell; the wound bare cell is placed in an outer packaging shell to make a soft-pack battery, and after drying, the electrolyte is injected, and after vacuum packaging, standing, formation, shaping and other processes, a lithium-ion battery is obtained.

[0174] The following Examples 2-1 and 2-3 mainly explore the effect of the first additive content in the electrolyte on battery performance, as follows:

[0175] Example 2-1

[0176] A method for preparing a lithium-ion battery is provided. Compared with Example 1, the preparation of the positive and negative electrode materials in Example 2-1 is the same as that in Example 1, except that the electrolyte contains an additive (I-9) with a mass percentage of 2%. Other aspects remain the same as those in Example 1.

[0177] Example 2-2

[0178] A method for preparing a lithium-ion battery is provided. Compared with Example 1, the preparation of the positive and negative electrode materials in Example 2-2 is the same as that in Example 1, except that the electrolyte contains an additive (I-9) with a mass percentage of 5%. Other aspects remain the same as those in Example 1.

[0179] Example 2-3

[0180] A method for preparing a lithium-ion battery is provided. Compared with Example 1, the preparation of the positive and negative electrode materials in Example 2-3 is the same as that in Example 1, except that the electrolyte contains an additive (I-9) with a mass percentage of 0.1%. Other aspects remain the same as those in Example 1.

[0181] The following Examples 3-1 to 3-9 mainly explore the effect on battery performance by adjusting the type of the first additive, as follows:

[0182] Example 3-1

[0183] A method for preparing a lithium-ion battery is provided. Compared with Example 1, the preparation of the positive and negative electrode materials in Example 3-1 is the same as in Example 1, except that the first additive (I-9) with a mass percentage of 0.5% in the electrolyte is replaced with I-11 with a mass percentage of 0.5%. Other aspects remain the same as in Example 1.

[0184] Example 3-2

[0185] A method for preparing a lithium-ion battery is provided. Compared with Example 1, the preparation of the positive and negative electrode materials in Example 3-2 is the same as in Example 1, except that the first additive (I-9) with a mass percentage of 0.5% in the electrolyte is replaced with I-16 with a mass percentage of 0.5%. Other aspects remain the same as in Example 1.

[0186] Example 3-3

[0187] A method for preparing a lithium-ion battery is provided. Compared with Example 1, the preparation of the positive and negative electrode materials in Example 3-3 is the same as in Example 1, except that the first additive (I-9) with a mass percentage of 0.5% in the electrolyte is replaced with I-17 with a mass percentage of 0.5%. Other aspects remain the same as in Example 1.

[0188] Examples 3-4

[0189] A method for preparing a lithium-ion battery is provided. Compared with Example 1, the preparation of the positive and negative electrode materials in Example 3-4 is the same as that in Example 1, except that the first additive (I-9) with a mass percentage of 0.5% in the electrolyte is replaced with I-4 with a mass percentage of 0.5%. Other aspects remain the same as in Example 1.

[0190] Examples 3-5

[0191] A method for preparing a lithium-ion battery is provided. Compared with Example 1, the preparation of the positive and negative electrode materials in Examples 3-5 is the same as in Example 1, except that the first additive (I-9) with a mass percentage of 0.5% in the electrolyte is replaced with I-8 with a mass percentage of 0.5%. Other aspects remain the same as in Example 1.

[0192] Examples 3-6

[0193] A method for preparing a lithium-ion battery is provided. Compared with Example 1, the preparation of positive and negative electrode materials in Examples 3-6 is the same as in Example 1, except that: the first additive (I-9) with a mass percentage of 0.5% in the electrolyte is replaced with II-1 with a mass percentage of 0.5%. Other aspects remain the same as in Example 1.

[0194] Examples 3-7

[0195] A method for preparing a lithium-ion battery is provided. Compared with Example 1, the preparation of the positive and negative electrode materials in Examples 3-7 is the same as that in Example 1, except that the first additive (I-9) with a mass percentage of 0.5% in the electrolyte is replaced with II-5 with a mass percentage of 0.5%. Other aspects remain the same as in Example 1.

[0196] Examples 3-8

[0197] A method for preparing a lithium-ion battery is provided. Compared with Example 1, the preparation of the positive and negative electrode materials in Examples 3-8 is the same as that in Example 1, except that the first additive (I-9) with a mass percentage of 0.5% in the electrolyte is replaced with II-6 with a mass percentage of 0.5%. Other aspects remain the same as in Example 1.

[0198] Examples 3-9

[0199] A method for preparing a lithium-ion battery is provided. Compared with Example 1, the preparation of the positive and negative electrode materials in Examples 3-9 is the same as in Example 1, except that the first additive (I-9) with a mass percentage of 0.5% in the electrolyte is replaced with II-8 with a mass percentage of 0.5%. Other aspects remain the same as in Example 1.

[0200] The following Examples 4-1 to 4-6 mainly explore the effects on battery performance by adjusting the type of the second additive and its content in the electrolyte, as follows:

[0201] Example 4-1

[0202] A method for preparing a lithium-ion battery is provided. The difference between Example 4-1 and Example 1 is that the preparation of the positive and negative electrode materials is the same as in Example 1, except that the second additive (III-1) with a mass percentage of 0.5% in the electrolyte is replaced with III-3 with a mass percentage of 2%, and other aspects remain the same as in Example 1.

[0203] Example 4-2

[0204] A method for preparing a lithium-ion battery is provided. The difference between Example 4-2 and Example 1 is that the preparation of the positive and negative electrode materials is the same as in Example 1, except that the second additive (III-1) with a mass percentage of 0.5% in the electrolyte is replaced with III-6 with a mass percentage of 2%, and other aspects remain the same as in Example 1.

[0205] Example 4-3

[0206] A method for preparing a lithium-ion battery is provided. The difference between Example 4-3 and Example 1 is that the preparation of the positive and negative electrode materials is the same as in Example 1, except that the second additive (III-1) with a mass percentage of 0.5% in the electrolyte is replaced with III-8 with a mass percentage of 2%, and other aspects remain the same as in Example 1.

[0207] Example 4-4

[0208] A method for preparing a lithium-ion battery is provided. The difference between Example 4-3 and Example 1 is that the preparation of the positive and negative electrode materials is the same as in Example 1, except that the second additive (III-1) with a mass percentage of 0.5% in the electrolyte is replaced with IV-1 with a mass percentage of 2%, and other aspects remain the same as in Example 1.

[0209] Examples 4-5

[0210] A lithium-ion battery is provided. The preparation of the positive and negative electrode materials of Examples 4-5 is the same as that of Example 1, except that: the second additive (III-1) with a mass percentage of 0.5% in the electrolyte is replaced with lithium bis(fluorosulfonyl)imide with a mass percentage of 5%, and other aspects remain the same as Example 1.

[0211] Examples 4-6

[0212] A lithium-ion battery is provided. The preparation of the positive and negative electrode materials of Examples 4-6 is the same as that of Example 1, except that: the second additive (III-1) with a mass percentage of 0.5% in the electrolyte is replaced with lithium bis(trifluoromethanesulfonyl)imide with a mass percentage of 5%, and other aspects remain the same as Example 1.

[0213] The following Examples 5-1 to 5-4 mainly explore the effect on battery performance by adjusting the silicon content in the negative electrode active material, as follows:

[0214] Example 5-1

[0215] A method for preparing a lithium-ion battery is provided. Compared with Example 1, Example 5-1 has the same electrolyte and the same preparation of the positive electrode material. The difference is that the mass percentage content of the silicon element is 2% based on the total mass of the negative electrode active material. Other aspects remain the same as Example 1.

[0216] Example 5-2

[0217] A method for preparing a lithium-ion battery is provided. Compared with Example 1, Example 5-2 has the same electrolyte and the same preparation of the positive electrode material. The difference is that the mass percentage content of silicon element is 15% based on the total mass of the negative electrode active material. Other aspects remain the same as Example 1.

[0218] Example 5-3

[0219] A method for preparing a lithium-ion battery is provided. Compared with Example 1, Example 5-3 has the same electrolyte and the same preparation of the positive electrode material. The difference is that the mass percentage content of the silicon element is 25% based on the total mass of the negative electrode active material. Other aspects remain the same as Example 1.

[0220] Example 5-4

[0221] A method for preparing a lithium-ion battery is provided. Compared with Example 1, Example 5-4 has the same electrolyte and the same preparation of the positive electrode material. The difference is that the mass percentage content of silicon element is 30% based on the total mass of the negative electrode active material. Other aspects remain the same as Example 1.

[0222] The following Example 6 mainly explores the effect on battery performance by adjusting the type of positive electrode material, as follows:

[0223] Example 6

[0224] A lithium-ion battery is provided. The electrolyte and negative electrode materials of Example 6 are the same as those of Example 1, except that: lithium nickel cobalt manganese oxide LiNi 0.8 Co 0.1Mn 0.1 O2 (NCM811) is replaced by lithium nickel cobalt manganese oxide LiNi 0.9 Co 0.05 Mn 0.05 O2, other aspects remain the same as in Example 1.

[0225] Comparative Example 1

[0226] A method for preparing a lithium-ion battery is provided. Compared with Example 1, the preparation of the positive and negative electrode materials in Comparative Example 1 is the same as in Example 1, except that the first additive is not added to the electrolyte, and other aspects remain the same as in Example 1.

[0227] Comparative Example 2

[0228] A method for preparing a lithium-ion battery is provided. Compared with Example 1, the preparation of the positive and negative electrode materials in Comparative Example 2 is the same as that in Example 1, except that no second additive is added to the electrolyte, and other aspects remain the same as those in Example 1.

[0229] Comparative Example 3

[0230] A method for preparing a lithium-ion battery is provided. Compared with Example 1, the preparation of the positive and negative electrode materials in Comparative Example 3 is the same as that in Example 1, except that the first additive and the second additive are not added to the electrolyte, and other aspects remain the same as those in Example 1.

[0231] Comparative Example 4-1

[0232] A method for preparing a lithium-ion battery is provided. Compared with Example 1, Comparative Example 4-1 has the same electrolyte, except that the mass percentage content of silicon element is 40% based on the total mass of the negative electrode active material.

[0233] Comparative Example 4-2

[0234] A method for preparing a lithium ion battery is provided. Compared with Example 1, the electrolyte of Comparative Example 4-2 is the same, except that: lithium nickel cobalt manganese oxide LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811) was replaced by lithium manganate (LiMn2O4), and other aspects remained the same as in Example 1.

[0235] The batteries prepared in the above examples and comparative examples of this application were tested as follows:

[0236] (1) High temperature storage test: After the divided batteries are placed in a 25°C environment and left to stand for 1 hour, the capacity is calibrated at a rate of 0.33C, and the discharge capacity C1 is recorded. Charge at 0.33C to 4.2V and cut off at 0.05C. Then place the fully charged batteries in a 60°C oven for 28 days. After 28 days, perform a 0.33C discharge test on the batteries, discharge them to 2.5V, and obtain the discharge capacity C2. Then perform a 0.33C charge and discharge test for two weeks, and take the discharge capacity C3 of the last week. The capacity retention rate is: C2 / C1×%; the capacity recovery rate is: C3 / C1×%.

[0237] (2) 25°C cycle test: The battery was charged at a constant temperature of 25°C with a constant current and constant voltage of 1C to 4.2V, with a cut-off current of 0.05C, and then discharged at 1C to 2.5V. The capacity retention rate after 800 cycles was recorded: Capacity retention rate of the battery after 800 cycles at 25°C (%) = discharge capacity after 800 cycles / discharge capacity at the first cycle × 100%.

[0238] (3) DCR growth rate test: Charge the fresh battery before cycling to 50% SOC, let it rest for 1 hour, record the voltage V1 after rest, discharge it at 2C for 30 seconds, record the termination voltage V2, and calculate the DCR of the battery: DCR1 = (V1-V2) / I 2C ; Charge the cycled battery to 50% SOC, let it rest for 1 hour, record the voltage V3 after rest, discharge it at 2C for 30 seconds, record the termination voltage V4, and calculate the DCR of the battery, DCR2 = (V3-V4) / I 2C , Cycle DCR growth rate = (DCR2-DCR1) / DCR1×100%. The test temperature is 25°C.

[0239] The specific test results are shown in Table 5 below:

[0240] Table 5 Performance test list

[0241]

[0242]

[0243] In combination with the above-mentioned Example 1, Example 2-1 to Example 2-3, and Comparative Example 1, it can be seen that the content of the first additive in the electrolyte affects the battery performance. Specifically, the content of the first additive in the electrolyte shown in Example 2-2 is too high, and the content of the first additive in the electrolyte shown in Example 2-3 is too low, both of which are not conducive to improving the cycle performance and high-temperature storage performance of the battery.

[0244] From the above-mentioned Example 1 and Example 3-1 to Example 3-9, it can be seen that different types of first additives also have an impact on battery performance. Among them, the types of first additives shown in Example 1, Example 3-3, Example 3-4, Example 3-6 and Example 3-9 have a more obvious improvement on battery performance than other types.

[0245] In combination with the above-mentioned Example 1, Example 4-5 and Example 4-6, it can be seen that by adding a fluorinated sulfonyl imide salt to the electrolyte, the fluorinated sulfonyl imide salt can facilitate the formation of a stable solid electrolyte interface film on the surface of the silicon negative electrode material. The solid electrolyte interface film is not easy to decompose even at high temperatures, thereby improving the recycling effect of the battery by reducing the consumption of the electrolyte and the negative electrode material.

[0246] In combination with the above-mentioned Example 1, Example 5-1 to Example 5-4 and Comparative Example 4-1, it can be seen that the silicon content in the negative electrode active material is within the protection scope of this application, and it is used together with the positive electrode material and additives in the electrolyte of this application to improve the cycle performance and storage performance of the battery.

[0247] In combination with the above-mentioned Example 6, Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4-2, it can be seen that the additive protected in this application is used together with the nickel-containing positive electrode material and the silicon-based negative electrode material to improve the electrochemical performance of the battery of this application.

[0248] Therefore, the design method provided in this application generates a solid electrolyte interface film with stable properties and appropriate thickness on the surface of nickel-containing positive electrode materials and silicon-based negative electrode materials. This interface film can effectively inhibit the decomposition of the electrolyte and at the same time improve the high-temperature storage performance and cycle performance of the battery.

[0249] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A lithium-ion battery, characterized in that: Including positive electrode sheet, negative electrode sheet and electrolyte; The positive electrode plate includes a nickel-containing positive electrode material; The negative electrode plate includes a negative electrode active material, the negative electrode active material includes silicon, and the mass percentage content of the silicon element is 2% to 30% based on the total mass of the negative electrode active material; The electrolyte includes a first additive and a second additive; The structural formula of the first additive is the following formula I or II: In formula I and formula II, X is independently selected from substituted or unsubstituted C1-C10 alkylene, Any one of; the substituted substituent is selected from halogen; wherein R1 and R2 are independently selected from any one or more of halogen, substituted or unsubstituted C1-C5 alkoxy, substituted or unsubstituted C1-C5 alkyl; and the substituted substituent is selected from halogen; The second additive is any one or more of the following structural formulas: III, IV, or fluorine-containing sulfonyl imide salts: In formula III, m represents a positive integer from 1 to 3, R 11 、R 12 Each independently selected from any one or more of hydrogen, halogen, C1-C4 alkyl, cyclic carbonate group, cyclic sulfate group, and cyclic sulfate-substituted cyclic carbonate group; In Formula IV, R 21 、R 22 Each is independently selected from any one or more of hydrogen, halogen, and C1-C4 alkyl.

2. The lithium-ion battery according to claim 1, wherein: The formula I includes any one or more of the following compounds: And / or, the formula II includes any one or more of the following compounds; And / or, the formula III includes any one or more of the following compounds; And / or, the formula IV comprises any one or more of the following compounds; 3. The lithium-ion battery according to any one of claims 1 to 2, characterized in that: Based on the total mass of the electrolyte, the mass percentage content of the first additive is 0.1% to 5%; And / or, based on the total mass of the electrolyte, the mass percentage content of the second additive is 0.1% to 5%.

4. The lithium-ion battery according to any one of claims 1 to 2, characterized in that: The fluorine-containing sulfonyl imide salt includes any one or more of lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethanesulfonyl)imide.

5. The lithium-ion battery according to any one of claims 1 to 2, characterized in that: The single-sided coating density of the negative electrode sheet is 50g / m 2 ~200g / m 2 ; And / or, the compaction density of the negative electrode plate is 1.50 g / cm 3 ~1.75g / cm 3 .

6. The lithium-ion battery according to any one of claims 1 to 2, characterized in that: The negative electrode active material includes a silicon-based negative electrode material, and the silicon-based negative electrode material includes any one or more of nano-silicon, silicon-oxygen material, silicon-carbon material, and silicon alloy; Preferably, the average particle size of the silicon-based negative electrode material is 5 μm to 10 μm.

7. The lithium-ion battery according to any one of claims 1 to 2, characterized in that: The negative electrode active material includes a carbonaceous material, and the carbonaceous material includes graphite.

8. The lithium-ion battery according to any one of claims 1 to 2, characterized in that: The nickel-containing positive electrode material includes any one or more of lithium nickelate, lithium nickel manganeseate, and lithium nickel cobalt manganese oxide.

9. The lithium-ion battery according to any one of claims 1 to 2, characterized in that: The nickel-containing positive electrode material includes lithium nickel cobalt manganese oxide. Based on the total molar number of transition metals in the lithium nickel cobalt manganese oxide, the molar percentage content of the nickel element is greater than 50% and less than 95%.

10. An electrical device, characterized in that: A lithium ion battery comprising the lithium ion battery according to any one of claims 1 to 9.

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