An electrochemical device based on interface functional group management and a preparation method thereof

Abstract

The application discloses an electrochemical device based on interface functional group management and a preparation method thereof. The electrochemical device is composed of an electrolyte, an electrode sheet and a diaphragm. The electrolyte contains a fluorosulfonyl compound with a main chain carbon atom number of 2 or more and 6 or less, and the mass percentage of the fluorosulfonyl compound is a, wherein 0.01% <= a <= 7%. The positive electrode sheet contains a positive electrode current collector and a positive electrode material layer on the surface of the positive electrode current collector, and the surface of the positive electrode material layer contains an interface layer. The interface layer contains C-O, C=O and CO3 2- functional groups, and the relative contents of the C-O, C=O and CO3 2- functional groups are x, y and z respectively. a, x, y and z satisfy the relationship formula: 0.1 <= a(x+y) / z <= 200. In the electrochemical device provided in the application, the electrolyte and the positive electrode satisfy the above characteristics, and the room temperature cycle performance, the rate performance and the high and low temperature performance of the electrochemical device can be improved.

Description

Technical Field

[0001] This invention belongs to the field of electrochemistry, specifically relating to an electrochemical device based on interface functional group management and its preparation method. Background Technology

[0002] Electrochemical devices (such as lithium-ion batteries and sodium-ion batteries) are widely used in various electronic devices and power systems as important energy storage devices. However, with the continuous improvement of energy density and operating voltage, the stability of the internal electrode / electrolyte interface has become a key bottleneck restricting further improvement of battery performance.

[0003] Under high-voltage operating conditions, positive electrode materials are prone to structural degradation, while the electrolyte undergoes continuous decomposition reactions at strongly oxidizing interfaces, leading to the formation of unstable interfaces, dissolution of transition metal ions, and irreversible electrolyte consumption. On the other hand, high specific surface area negative electrode materials (such as silicon-based negative electrodes and hard carbon) face significant volume changes during cycling, causing repeated rupture and reconstruction of their surface solid electrolyte interphase (SEI) film, exacerbating the loss of active materials and increasing interfacial impedance. These interfacial problems collectively contribute to the performance degradation of electrochemical devices in terms of cycle life, rate performance, and high-temperature stability, making it difficult to meet the ever-increasing demands for high performance.

[0004] Improving interfacial properties through electrolyte additives is an effective and simple strategy. Currently, various functional additives have been researched and applied, but their effects are often limited to improving a single electrode or specific properties, making it difficult to achieve synergistic stabilization of the positive and negative electrode interfaces and simultaneous improvement of overall performance. Therefore, developing novel multifunctional additive schemes that can simultaneously and efficiently stabilize the positive and negative electrode interfaces and adapt to high-voltage, high-energy-density systems has significant technical and application value. Summary of the Invention

[0005] To address the problems of rapid cycle decay, limited rate performance, and high-temperature expansion at the cathode-electrolyte interface caused by continuous electrolyte decomposition and structural stress in existing high-voltage, high-energy-density electrochemical devices, this invention constructs a solid electrolyte interphase (CEI) film with optimized chemical composition and structure on the cathode surface by quantitatively controlling the ratio between the content of fluorosulfonyl compounds in the electrolyte and the content of key functional groups in the interface layer of the cathode surface.

[0006] The technical solution of this invention is as follows.

[0007] An electrochemical device based on interface functional group management, comprising an electrolyte, a positive electrode plate, a negative electrode plate, and a separator, characterized in that...

[0008] The electrolyte contains a fluorosulfonyl compound with 2 or more but less than 6 carbon atoms in its main chain, and the mass percentage of the fluorosulfonyl compound in the electrolyte is a, wherein 0.01% ≤ a ≤ 7%;

[0009] The positive electrode sheet includes a positive current collector and a positive electrode material layer located on the surface of the positive current collector. The surface of the positive electrode material layer contains an interface layer; the interface layer contains CO, C=O, and CO3. 2- Functional groups (the introduction of additives reduces the carbonate content in the interfacial film), namely CO, C=O, and CO3. 2- The relative contents of functional groups are x, y, and z, respectively;

[0010] a and x, y, z satisfy the following relationship: 0.1 ≤ a(x+y) / z ≤ 200. The electrolyte and positive electrode in the electrochemical device provided in this application satisfy the above characteristics, which can improve the room temperature cycling performance, rate performance, and high and low temperature performance of the electrochemical device.

[0011] Preferably, the fluorosulfonyl compound has the following general formula:

[0012]

[0013] Wherein, R1 is a substituted or unsubstituted C1-C6 alkyl, a substituted or unsubstituted C2-C6 alkenyl, a substituted or unsubstituted C2-C6 alkynyl, a substituted or unsubstituted aryl, or a C1-C6 alkyl containing an ether bond, or a substituted or unsubstituted siloxane, or a nitrogen or phosphorus heteroatom functional group; when substituted, the substituent is fluorine or a C1-C4 alkyl.

[0014] Preferably, the fluorosulfonyl compound is selected from one or more of the following substances:

[0015]

[0016] 2,2-Difluoro-2-(fluorosulfonyl)acetic acid methyl ester (CAS No.: 680-15-9);

[0017]

[0018] Perfluorobutyl sulfonyl fluoride (CAS No.: 375-72-4);

[0019]

[0020] Benzyl sulfonyl fluoride (CAS No.: 329-98-6);

[0021]

[0022] 2-Fluorobenzenesulfonyl fluoride (CAS: 52200-99-4);

[0023]

[0024] 2,5-Difluorobenzenesulfonyl fluoride (CAS: 62094-86-4);

[0025]

[0026] p-Toluenesulfonyl fluoride (CAS: 455-16-3);

[0027]

[0028] 4-Chlorobenzenesulfonyl fluoride (CAS: 349-89-3);

[0029]

[0030] 4-Methoxybenzenesulfonyl fluoride (CAS: 368-91-2);

[0031]

[0032] 2-Naphthalenesulfonyl fluoride (CAS: 325-12-2)

[0033]

[0034] [1,1'-Biphenyl]-4-sulfonyl fluoride (CAS: 325-04-2)

[0035]

[0036] Trimethylsilyl 2-(fluorosulfonyl) difluoroacetate (CAS: 120801-75-4);

[0037]

[0038] Ethylenesulfonyl fluoride (CAS: 677-25-8);

[0039] Preferably, the electrolyte in this invention is solid, liquid, or gel-like. The electrolyte further includes lithium salt, linear carboxylic acid ester compound, and organic solvent;

[0040] The concentration of the lithium salt is 0.5–8 mol / L, preferably 1–6 mol / L. The lithium salt includes one or more of the following: lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrachloroaluminate (LiAlCl4), lithium iodide (LiI), lithium bromide (LiBr), lithium thiocyanate (LiSCN), lithium tetrafluoroborate (LiBF4), lithium difluorooxalate borate (LiBF2(C2O4)) (LiDFOB), lithium tetraphenylborate (LiB(C6H5)4), lithium dioxalate borate (LiB(C2O4)2) (LiBOB), lithium tetrafluorooxalate phosphate (LiPF4(C2O4)) (LiFOP), lithium nitrate (LiNO3), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(trifluoromethanesulfonylimide) (LiTFSI), and lithium bis(fluorosulfonylimide) (LiFSI).

[0041] The organic solvents include one or more of the following: ethers such as dimethyl ether, ethylene glycol dimethyl ether (DME), diethylene glycol dimethyl ether, tri(ethylene glycol) dimethyl ether, 1,2-diethoxyethane, diethoxyethane, ethoxymethoxyethane, 1,3-dimethoxypropane (DMP), tetrahydrofuran, 2-methyltetrahydrofuran, and dioxolane; carbonates such as ethylene carbonate (EC), propylene carbonate (PC), butenyl carbonate, dimethyl carbonate (DMC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC); and fluorinated organic solvents such as 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE), ethyl difluoroacetate (EDFA), ethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoropropylene carbonate (TFEC), trifluoroethyl methyl carbonate, and trifluoroethyl ethyl carbonate.

[0042] Preferably, the positive current collector is selected from aluminum foil; in this invention, the aluminum foil includes blank aluminum foil, base-coated aluminum foil, cleaned aluminum foil, corona-treated aluminum foil, perforated aluminum foil, etc.; the positive electrode material layer includes positive electrode active material, conductive agent and adhesive.

[0043] Preferably, the positive electrode active material includes ternary (nickel-cobalt-manganese ternary cathode material), high-nickel ternary, lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium nickel manganese oxide, and lithium-rich manganese oxide; the conductive agent is selected from carbon black or carbon nanotubes; the binder is a fluorocarbon binder; the fluorocarbon binder refers to a polymer material containing fluorine atoms (F) and carbon atoms (C) in its molecular structure and possessing adhesive function. It introduces unique chemical inertness, electrochemical stability, and hydrophobicity through fluorine atoms.

[0044] The fluorocarbon adhesive is selected from at least one of polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polytetrafluoroethylene (PTFE), polyvinyl fluoride (PVF), or their modified derivatives (such as carboxylated or sulfonated modified derivatives). Preferably, the fluorocarbon adhesive is polyvinylidene fluoride (PVDF).

[0045] Preferably, the negative electrode sheet is composed of a negative electrode active material and a negative electrode current collector, wherein the negative electrode current collector is a copper foil; in this invention, the copper foil includes blank copper foil, bottom-coated copper foil, polymer composite copper foil, perforated copper foil, etc.; the negative electrode active material is composed of graphite, conductive carbon black, styrene-butadiene rubber as an adhesive, and sodium carboxymethyl cellulose as a thickener.

[0046] Preferably, the diaphragm is a single-layer polyethylene (PE) porous polymer film with a thickness of 2~25μm, preferably 9μm, and a porosity of 5~80%, preferably 42%; at least one surface of the diaphragm is coated with a heat-resistant coating composed of alumina inorganic particles and polyvinylidene fluoride (PVDF) binder.

[0047] A method for preparing an electrochemical device based on interface functional group management includes the following steps:

[0048] (1) Preparation of the positive electrode sheet:

[0049] The positive electrode active material, conductive agent, and binder were thoroughly mixed in N-methylpyrrolidone solvent at a mass ratio of 96.5:1.5:2.0 to form a uniform positive electrode slurry. The positive electrode slurry was then uniformly coated onto the positive electrode current collector, and after drying and cold pressing, a positive electrode sheet was obtained. The areal density of the positive electrode active material was 20 mg / cm³. 2 The compacted density is 3.45 g / cm³. 3 ;

[0050] (2) Preparation of negative electrode sheet:

[0051] The negative electrode active material was thoroughly mixed in a deionized aqueous solvent to form a uniform negative electrode slurry. This slurry was then uniformly coated onto a negative electrode current collector, and after drying and cold pressing, a negative electrode sheet was obtained. The areal density of the negative electrode active material was 10.5 mg / cm³. 2 The compacted density is 1.65 g / cm³. 3 ;

[0052] (3) Preparation of electrolyte:

[0053] In an argon atmosphere with a dew point below 0°C, a thoroughly dried lithium salt is dissolved in an organic solvent to obtain a basic electrolyte; a linear carboxylic acid ester compound and a fluorosulfonyl compound are added to the basic electrolyte, and the mixture is stirred until homogeneous to obtain the final electrolyte.

[0054] (4) Battery assembly:

[0055] The prepared positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, with the separator positioned between the positive and negative electrode sheets, and then wound to form a battery cell. The battery cell is placed in an aluminum-plastic film outer packaging bag, vacuum baked at 80°C for 24 hours, and then a certain amount of the above-mentioned electrolyte is injected. After vacuum sealing, standing, formation (0.02C constant current charging to 3.6V), and shaping processes, the battery cell is obtained.

[0056] Explanation of the functions in this invention:

[0057] During battery formation and cycling, the active groups (-SO2F) of fluorosulfonyl compounds (such as fluorosulfonates) in the electrolyte can undergo electrochemical reduction or react with active sites on the electrode surface, contributing to the construction of a stable interface layer containing sulfur, oxygen, and fluorine on the positive electrode surface. Simultaneously, linear carboxylic acid esters, acting as co-solvents, not only adjust the viscosity and polarity of the electrolyte system, but their ester groups (-COOR) also participate in the interfacial reaction, influencing the organic composition of the interface layer. The pre-formed or in-situ generated interface layer on the positive electrode surface contains CO, C=O, and CO32-. 2- The relative content of functional groups directly reflects the chemical stability and ion conduction properties of the interface layer.

[0058] Synergistic effect mechanism:

[0059] The synergistic effect discovered in this application stems from the quantitative matching and dynamic regulation of the interfacial chemical state between the active additive in the electrolyte and the positive electrode surface. The fluorosulfonyl compound preferentially reacts at defects or highly active sites on the positive electrode surface, and its decomposition products effectively inhibit carbonate (CO3-) ions. 2- Excessive generation of CO3 2- This typically stems from the deep, irreversible decomposition of carbonate solvents; excessive amounts can lead to increased interfacial impedance and deteriorated mechanical properties. The ratio a(x+y) / z has a clear physicochemical meaning: the molecule a(x+y) represents the contribution of beneficial oxygen-containing carbon species (CO, C=O) induced by fluorosulfonyl compounds; these two functional groups contribute to the formation of a dense interfacial organic framework with appropriate ionic conductivity; the denominator z represents the harmful carbonate ions (CO3-) that need to be suppressed. 2- The content of ).

[0060] When this ratio is within the optimization range of 0.1 to 200:

[0061] 1. Interface composition optimization: The amount of fluorosulfonyl compound added is sufficient to effectively inhibit the excessive decomposition of carbonate solvent, thereby eliminating harmful, high-resistance carbonate (CO3) ions in the interface layer. 2-The content of z is controlled at a low level, while promoting the formation of more beneficial ether / carboxylate (CO, C=O) structures, thereby constructing an interface layer with lower impedance and better lithium-ion conductivity.

[0062] 2. Improved stability: The organic network rich in CO and C=O, together with the inorganic components containing sulfur and fluorine, forms a more stable composite interface layer, which can more effectively prevent the continuous oxidative decomposition of the electrolyte and the dissolution of transition metal ions, and significantly improve the cycle stability under high voltage.

[0063] 3. Improved kinetic and mechanical properties: The optimized interface layer has both good ionic conductivity and mechanical toughness, which is beneficial to improving the rate performance of the battery and can better adapt to the volume changes of the cathode material in a wide temperature range (especially at low temperatures), suppressing interface cracking, thereby simultaneously improving the high and low temperature performance of the electrochemical device.

[0064] Therefore, the relationship 0.1 ≤ a(x+y) / z ≤ 200 essentially achieves a precise balance between the active additive dosage and the composition of key functional groups in the interface layer. By regulating the nature of interface chemistry, it fundamentally improves the overall performance of the electrochemical device.

[0065] Compared with the prior art, the advantages of the present invention are:

[0066] In this invention, the interfacial membrane selectively inhibits harmful carbonate ions (CO3). 2- The formation of beneficial ether / carboxylate (CO, C=O) structures promotes the generation of these compounds, achieving high ionic conductivity and low interfacial impedance, thereby significantly improving the battery's rate performance and low-temperature discharge capability. Simultaneously, the introduction of stabilizing elements such as sulfur and fluorine enhances the chemical inertness of the interfacial film, effectively suppressing the oxidative decomposition of the electrolyte under high voltage and the dissolution of transition metal ions, ensuring capacity retention during long-cycle periods. Furthermore, this optimized interfacial film possesses better mechanical integrity, buffering lattice stress during charge and discharge, preventing the generation and propagation of microcracks in active particles, and thus suppressing abnormal battery expansion under high-temperature environments.

[0067] By precisely satisfying the key proportional relationship of 0.1≤a(x+y) / z≤200, this invention achieves directional control of the chemical composition of the cathode interface, enabling the electrochemical device to maintain high energy density while also possessing excellent long cycle life, outstanding high and low temperature performance, and significantly improved safety. Attached Figure Description

[0068] Figure 1 For XPS analysis of CC, C=O, CO3 2- C1s spectrum of XPS cathode material.

[0069] Figure 2 This is a graph showing the discharge capacity. Detailed Implementation

[0070] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto. For process parameters not specifically noted, conventional techniques can be referred to.

[0071] 1. Preparation of the positive electrode

[0072] LiNi, the positive electrode active material 0.8 Co 0.1 Mn 0.1 O2 (NCM811), conductive carbon black Super P, and fluorocarbon binder were mixed thoroughly in N-methylpyrrolidone (NMP) solvent at a mass ratio of 96.5:1.5:2.0 to form a uniform positive electrode slurry. The positive electrode slurry was then uniformly coated onto a positive electrode current collector aluminum foil, dried, and cold-pressed to obtain the positive electrode sheet. The areal density of the positive electrode active material was 20 mg / cm³. 2 The compacted density is 3.45 g / cm³. 3 .

[0073] The fluorocarbon adhesive is selected according to different embodiments, including but not limited to: polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polytetrafluoroethylene (PTFE) emulsion or mixtures thereof. In this embodiment, PVDF is used as the adhesive.

[0074] 2. Preparation of the negative electrode

[0075] Artificial graphite (anode active material), conductive carbon black, styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC) (thickener) were mixed in a deionized water solvent at a mass ratio of 96.2:1.0:1.5:1.3 to form a homogeneous negative electrode slurry. The negative electrode slurry was then uniformly coated onto copper foil (nenode current collector), dried, and cold-pressed to obtain the negative electrode sheet. The areal density of the negative electrode active material was 10.5 mg / cm³. 2 The compacted density is 1.65 g / cm³. 3 .

[0076] 3. Preparation of electrolyte

[0077] In an argon-atmosphere glove box with a dew point below 0°C, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed at a volume ratio of 3:5:2. In this embodiment, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were used as non-aqueous organic solvents. Linear carboxylic acid ester compounds, such as ethyl acetate, propyl propionate, methyl butyrate, ethyl trifluoroacetate, and methyl pentafluoropropionate, were also added. Thoroughly dried lithium salt LiPF6 was dissolved in the above solvent at a concentration of 1.0 mol / L to obtain the basic electrolyte.

[0078] Based on the substances listed in Table 1, specific types and amounts of fluorosulfonyl compounds were added to the above-mentioned basic electrolyte, and the mixture was stirred evenly to obtain the target electrolyte.

[0079] 4. Diaphragm

[0080] A single-layer porous polyethylene (PE) membrane with a thickness of 9 μm and a porosity of 42% was selected as the separator. At least one surface of the separator was coated with a heat-resistant coating composed of alumina (Al2O3) inorganic particles and polyvinylidene fluoride (PVDF) binder.

[0081] 5. Assembly of lithium-ion batteries

[0082] The prepared positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes, and then wound to form a battery cell. The battery cell is placed in an aluminum-plastic film outer packaging bag and vacuum-baked at 80°C for 24 hours, after which a measured amount of the above-mentioned electrolyte is injected. After vacuum sealing, settling, formation (0.02C constant current charging to 3.6V), and shaping processes, a soft-pack lithium-ion battery is obtained.

[0083] Figure 1 For XPS analysis of CC, C=O, CO3 2- The C1s spectrum of the XPS cathode material was used to calculate the percentage content of each functional group by fitting the peak area. After the conversion, Figure 1 In the upper part of the image, the CO content is 13%, the C=O content is 10%, and the CO3 content is... 2- The content was 6%; Figure 1 In the image below, the CO content is 16%, the C=O content is 17%, and the CO3 content is... 2- The content is 14%. Of this, CO and C=O are organic components of the interfacial membrane, and CO3... 2- It belongs to the category of inorganic lithium carbonate. When there is a higher proportion of organic components in the interfacial film, the battery's cycle retention rate is better. CO3 2- Under relatively high conditions, battery performance will decrease.

[0084] 1<x<20 1<y<20 1<z<20 Serial Number Fluorosulfonyl compounds a% CO(x%) C=O(y%) <![CDATA[CO3 2- (z%)]]> a(x+y) / z Cyclic performance % Example 1 2,2-Difluoro-2-(fluorosulfonyl)acetic acid methyl ester 1 5 7 3 4.000 66.30% Example 2 2,2-Difluoro-2-(fluorosulfonyl)acetic acid methyl ester 3 6 7 8 4.875 77.3% Example 3 2,2-Difluoro-2-(fluorosulfonyl)acetic acid methyl ester 5 13 10 6 62.500 82.20% Example 4 2,2-Difluoro-2-(fluorosulfonyl)acetic acid methyl ester 7 13 8 6 24.500 75.30% Example 5 2,2-Difluoro-2-(fluorosulfonyl)acetic acid methyl ester 0.1 4 4 8 0.100 60.30% Example 6 2,2-Difluoro-2-(fluorosulfonyl)acetic acid methyl ester 2 16 17 14 1.900 69.30% Example 7 Perfluorobutylsulfonyl fluoride 1 7 6 13 1.000 70.30% Example 8 Perfluorobutylsulfonyl fluoride 3 11 13 8 9.000 77.30% Example 9 Perfluorobutylsulfonyl fluoride 5 13 14 9 15.000 75.30% Example 10 Perfluorobutylsulfonyl fluoride 7 9 12 10 14.700 76.30% Example 11 Perfluorobutylsulfonyl fluoride 2 8 11 12 3.167 73.00% Example 12 Benzyl fluoride 1 7 5 15 0.800 63.40% Example 13 Benzyl fluoride 3 11 10 14 4.500 66.40% Example 14 Benzyl fluoride 5 19 17 6 30.000 70.30% Example 15 Benzyl fluoride 7 17 20 8 32.375 59.00% Example 16 2-Fluorobenzenesulfonyl fluoride 1 5 3 17 0.471 68.40% Example 17 2-Fluorobenzenesulfonyl fluoride 3 11 15 7 11.143 73.30% Example 18 2-Fluorobenzenesulfonyl fluoride 5 16 18 7 24.286 80.40% Example 19 2,5-Difluorobenzenesulfonyl fluoride 1 8 9 7 2.429 63.30% Example 20 2,5-Difluorobenzenesulfonyl fluoride 3 12 11 6 11.500 69.80% Example 21 2,5-Difluorobenzenesulfonyl fluoride 5 15 14 8 18.125 73.30% Example 22 p-Toluenesulfonyl fluoride 1 5 3 19 0.421 66.20% Example 23 p-Toluenesulfonyl fluoride 3 7 7 10 4.200 74.30% Example 24 p-Toluenesulfonyl fluoride 5 15 20 6 29.167 74.20% Example 25 p-Toluenesulfonyl fluoride 7 13 14 10 18.900 69.60% Example 26 4-Chlorobenzenesulfonyl fluoride 1 6 9 17 0.882 67.80% Example 27 4-Chlorobenzenesulfonyl fluoride 3 7 6 12 3.250 73.60% Example 28 4-Methoxybenzenesulfonyl fluoride 1 6 4 15 0.667 69.50% Example 29 4-Methoxybenzenesulfonyl fluoride 3 10 8 7 7.714 74.90% Example 30 4-Methoxybenzenesulfonyl fluoride 5 14 12 6 21.667 75.50% Example 31 2-Naphthalenesulfonyl fluoride 1 3 5 12 0.667 68.80% Example 32 2-Naphthalenesulfonyl fluoride 3 11 15 8 9.750 73.20% Example 33 2-Naphthalenesulfonyl fluoride 5 13 11 6 20.000 75.00% Example 34 [1,1'-Biphenyl]-4-sulfonyl fluoride 1 6 4 16 0.625 59.70% Example 35 [1,1'-Biphenyl]-4-sulfonyl fluoride 3 12 11 7 9.857 66.10% Example 36 [1,1'-Biphenyl]-4-sulfonyl fluoride 5 10 11 9 11.667 73.10% Example 37 Trimethylsilyl 2-(fluorosulfonyl)difluoroacetate 1 5 4 19 0.474 65.50% Example 38 Trimethylsilyl 2-(fluorosulfonyl)difluoroacetate 3 12 9 6 10.500 70.10% Example 39 Trimethylsilyl 2-(fluorosulfonyl)difluoroacetate 5 14 10 8 15.000 73.80% Example 40 Ethylenesulfonyl fluoride 3 13 11 6 12.000 69.00% Comparative Example 1 - 0 0 1.5 0.000 59.1%

[0085] The lithium-ion batteries produced in the above embodiments and comparative examples were subjected to corresponding performance tests according to the following methods, and the test data in Table 2 were calculated.

[0086] (1) 25℃ cycle test:

[0087] The test method is as follows: In a constant temperature chamber at 25℃±2℃, the lithium-ion battery is charged to 4.4V at a constant current and constant voltage of 1C, with a cutoff current of 0.05C, and then discharged to 3V at 1C. This charge-discharge cycle is repeated multiple times under the above conditions. The capacity retention rate of each battery after 800 cycles is calculated.

[0088] Calculation formula: Capacity retention rate (%) = Discharge capacity of corresponding cycle number (mAh) / Discharge capacity of the third cycle (mAh) • 100%.

[0089] Each example and comparative example used 5 batteries for testing. The average capacity retention rate of each group of 5 batteries after different cycles is recorded in Table 2.

[0090] (2) Battery high and low temperature discharge test

[0091] The discharge performance of lithium-ion batteries from Examples 3, 8, 18, 30, and Comparative Example 1 was tested at -20°C, -10°C, 0°C, 5°C, 45°C, and 60°C. The results are shown in Table 2. Figure 2 The test data in the middle.

[0092] Taking a -20℃ battery discharge test as an example: Under 25℃ environmental conditions, discharge the capacity-sorted battery at 0.2C to 3V and let it rest for 5 minutes; then charge it at 0.2C to 4.4V. When the cell voltage reaches 4.4V, switch to constant voltage charging at 4.4V until the charging current is less than or equal to the given cutoff current of 0.05C, and let it rest for 5 minutes. Transfer the fully charged battery to a high and low temperature chamber, set it to -20℃, and let it rest in the chamber for 120 minutes after the temperature is reached. Remove the battery, then discharge it at 0.2C to the cutoff voltage of 3V and let it rest for 5 minutes; then adjust the high and low temperature chamber temperature to 25℃±3℃, and let it rest in the chamber for 60 minutes after the temperature is reached. Remove the battery and charge it at 0.2C to 4.4V. When the cell voltage reaches 4.4V, switch to constant voltage charging at 4.4V until the charging current is less than or equal to the given cutoff current of 0.05C, and let it rest for 5 minutes. Calculate the capacity retention rate of the battery after discharging at -20℃ for 3V.

[0093] Calculation formula: -20℃ discharge 3V capacity retention rate (%) = (-20℃ discharge to 3V discharge capacity / 25℃ discharge to 3V discharge capacity) × 100%.

[0094] Table 2

[0095] -20℃ discharge -10℃ discharge 0℃ discharge 5℃ discharge 45℃ discharge 60℃ discharge Comparative Example 1 52.10% 69.20% 84.20% 90.10% 102.06% 95.78% Example 3 67.18% 77.62% 87.43% 91.51% 102.04% 102.00% Example 8 61.70% 74.72% 86.39% 90.94% 101.91% 101.48% Example 18 63.10% 75.30% 86.70% 91.00% 102.06% 101.45% Example 30 67.80% 79.73% 89.50% 93.66% 104.09% 103.36%

Claims

1. An electrochemical device based on interface functional group management, comprising an electrolyte, a positive electrode plate, a negative electrode plate, and a separator, characterized in that: The electrolyte contains a fluorosulfonyl compound with 2 or more but less than 6 carbon atoms in its main chain, and the mass percentage of the fluorosulfonyl compound in the electrolyte is a, wherein 0.01% ≤ a ≤ 7%; The positive electrode sheet includes a positive current collector and a positive electrode material layer located on the surface of the positive current collector. The surface of the positive electrode material layer contains an interface layer; the interface layer contains CO, C=O, and CO3. 2- Functional groups, specifically CO, C=O, and CO3 in the interface layer. 2- The relative contents of functional groups are x, y, and z, respectively; a and x, y, z satisfy the following relationship: 0.1≤a(x+y) / z≤200.

2. The electrochemical device based on interface functional group management as described in claim 1, characterized in that, The fluorosulfonyl compound has the following general formula: Wherein, R1 is a substituted or unsubstituted C1-C6 alkyl, a substituted or unsubstituted C2-C6 alkenyl, a substituted or unsubstituted C2-C6 alkynyl, a substituted or unsubstituted aryl, or a C1-C6 alkyl containing an ether bond, or a substituted or unsubstituted siloxane, or a nitrogen or phosphorus heteroatom functional group; when substituted, the substituent is fluorine or a C1-C4 alkyl.

3. The electrochemical device based on interface functional group management as described in claim 1, characterized in that, The fluorosulfonyl compound is selected from one or more of 2,2-difluoro-2-(fluorosulfonyl)acetic acid methyl ester, perfluorobutylsulfonyl fluoride, benzyl sulfonyl fluoride, 2-fluorobenzenesulfonyl fluoride, 2,5-difluorobenzenesulfonyl fluoride, p-toluenesulfonyl fluoride, 4-chlorobenzenesulfonyl fluoride, 4-methoxybenzenesulfonyl fluoride, 2-naphthalenesulfonyl fluoride, [1,1'-biphenyl]-4-sulfonyl fluoride, trimethylsilyl 2-(fluorosulfonyl)difluoroacetate, and ethylenesulfonyl fluoride.

4. The electrochemical device based on interface functional group management as described in claim 1, characterized in that, The electrolyte can be solid, liquid, or gel-like.

5. The electrochemical device based on interface functional group management as described in claim 1, characterized in that, The electrolyte also includes lithium salts, linear carboxylic acid ester compounds, and organic solvents; The concentration of the lithium salt is 0.5–8 mol / L; the lithium salt includes one or more of lithium hexafluorophosphate, lithium perchlorate, lithium tetrachloroaluminate, lithium iodide, lithium bromide, lithium thiocyanate, lithium tetrafluoroborate, lithium difluorooxalate borate, lithium tetraphenylborate, lithium dioxalate borate, lithium tetrafluorooxalate phosphate, lithium nitrate, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(fluorosulfonyl)imide. The organic solvents include one or more of the following: ethers such as dimethyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tri(ethylene glycol) dimethyl ether, 1-2-diethoxyethane, diethoxyethane, ethoxymethoxyethane, 1,3-dimethoxypropane, tetrahydrofuran, 2-methyltetrahydrofuran, and dioxolane; carbonates such as ethylene carbonate, propylene carbonate, butene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; and fluorinated organic solvents such as 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, ethyl difluoroacetate, ethylene carbonate, difluoroethylene carbonate, trifluoropropylene carbonate, trifluoroethyl methyl carbonate, and trifluoroethyl ethyl carbonate.

6. The electrochemical device based on interface functional group management as described in claim 1, characterized in that, The positive electrode current collector is selected from aluminum foil; the positive electrode material layer includes a positive electrode active material, a conductive agent, and a binder.

7. The electrochemical device based on interface functional group management as described in claim 6, characterized in that, The positive electrode active material is selected from ternary, high-nickel ternary, lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium nickel manganese oxide, or lithium-rich manganese oxide; the conductive agent is selected from carbon black or carbon nanotubes; the binder is a fluorocarbon binder. The fluorocarbon adhesive is selected from at least one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polytetrafluoroethylene, or polyvinyl fluoride.

8. The electrochemical device based on interface functional group management as described in claim 1, characterized in that, The negative electrode sheet is composed of a negative electrode active material and a negative electrode current collector, wherein the negative electrode current collector is copper foil; the negative electrode active material is composed of graphite, conductive carbon black, styrene-butadiene rubber as a binder, and sodium carboxymethyl cellulose as a thickener.

9. The electrochemical device based on interface functional group management as described in claim 1, characterized in that, The diaphragm is a single-layer porous polyethylene polymer film with a thickness of 2~25 μm and a porosity of 5~80%; at least one surface of the diaphragm is coated with a heat-resistant coating composed of inorganic alumina particles and polyvinylidene fluoride binder.

10. The method for preparing the electrochemical device based on interfacial functional group management according to any one of claims 1 to 9, characterized in that, Includes the following steps: (1) Preparation of electrolyte: In an argon atmosphere with a dew point below 0°C, a thoroughly dried lithium salt is dissolved in an organic solvent to obtain a basic electrolyte; a linear carboxylic acid ester compound and a fluorosulfonyl compound are added to the basic electrolyte, and the mixture is stirred until homogeneous to obtain the final electrolyte. (2) Battery assembly: The positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, with the separator positioned between the positive and negative electrode sheets, and then wound to form a battery cell. The battery cell is then placed in an aluminum-plastic film outer packaging bag and vacuum-baked at 80°C for 24 hours. A measured amount of the above-mentioned electrolyte is then injected. After vacuum sealing, settling, formation, and shaping processes, the battery cell is obtained.

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