Battery cells, batteries and electrical devices

Abstract

This application discloses a battery cell, a battery, and an electrical device. One embodiment of the battery cell includes a negative electrode and an electrolyte. The negative electrode includes a current collector stacked on top of each other and an active material film containing active material particles, the active material particles being carbonaceous materials. The electrolyte includes a lithium salt, an organic solvent, and additives. The additives include a first additive and a second additive. The first additive includes a hydrofluoroether compound. The second additive has the general formula NO3-R1, where R1 includes substituted or unsubstituted carbonaceous heterocycles. The first additive in the electrolyte can reduce lithium-ion solvation. Further combined with the second additive, it is reduced and decomposed on the surface of the carbonaceous material to generate lithium nitrogen oxides, forming a dense, stable SEI film with high inorganic content on the surface of the carbonaceous material. This forms a stable interface layer between the carbonaceous material and the organic solvent, reducing side reactions between the carbonaceous material and the electrolyte, reducing lithium consumption, and improving cycle performance.

Description

Technical Field

[0001] This application relates to the field of batteries, and in particular to a battery cell, a battery, and an electrical device. Background Technology

[0002] Battery cells possess characteristics such as high capacity and long lifespan, and are therefore widely used in electronic devices, such as mobile phones, laptops, electric vehicles, electric cars, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes, and power tools. Due to the significant advancements in battery cell technology, higher performance requirements have been placed on them.

[0003] However, the cycle performance of individual battery cells is still relatively poor. Summary of the Invention

[0004] This application provides a battery cell, a battery, and an electrical device that can improve the cycle performance of the battery cell.

[0005] In a first aspect, embodiments of this application propose a battery cell, which includes a negative electrode and an electrolyte. The negative electrode includes a current collector and an active material film containing active material particles stacked together, the active material particles including carbonaceous materials. The electrolyte includes lithium salt, organic solvent and additives. The additives include a first additive and a second additive. The first additive includes a hydrofluoroether compound. The second additive has a general structural formula including NO3-R1, wherein R1 includes substituted or unsubstituted carbon-containing heterocycles.

[0006] Therefore, lithium ions in the electrolyte are solvated to form a solvation sheath. Anions preferentially participate in the formation of the SEI film by reducing and decomposing solvent molecules on the carbonaceous material surface. When solvated lithium ions intercalate at the interface, they easily induce solvent molecule intercalation, leading to SEI film instability. The first additive in the electrolyte, hydrofluoroether compound, can reduce the lithium ion solvation ratio and generate a more stable SEI film. In addition, a second additive containing a carbon-containing heterocyclic compound with a nitrate group is further added. This compound is reduced and decomposed on the carbonaceous material surface to generate lithium oxide nitrides. These lithium oxide nitrides participate in the formation of the SEI film, filling the pores or defects of the SEI film. This further increases the inorganic content of the SEI film while improving its density and stability. As a result, a dense, stable composite SEI film with a high inorganic content is formed on the carbonaceous material surface, creating a stable interface layer between the carbonaceous material and the organic solvent. This reduces side reactions between the carbonaceous material and the electrolyte, lowers lithium consumption, and improves cycle performance. On the other hand, composite SEI films with high inorganic content can reduce the transmission impedance of lithium ions through the SEI film and increase the rate of lithium ion extraction and insertion in carbonaceous materials, thereby improving cycle performance.

[0007] In some embodiments, the volume ratio of the first additive to the organic solvent is 1:(0.6 to 0.7).

[0008] Therefore, when the volume ratio of the first additive to the organic solvent is within the above range, the electrolyte has a suitable viscosity, which enhances the interaction between lithium ions and anions, reduces the lithium ion solvation ratio, and increases the rate at which anions participate in the SEI film.

[0009] In some embodiments, the concentration of the second additive in the electrolyte is 0.33 mol / L to 0.37 mol / L.

[0010] Therefore, the second additive is a carbon-containing heterocyclic substance with a nitrate group, which has high solubility in the electrolyte. This allows for obtaining a second additive within the aforementioned concentration range. A molar concentration of the second additive within this range ensures an appropriate amount of lithium oxide nitride in the SEI film. Lithium oxide nitride has high lithium-ion conductivity, achieving good lithium-ion conductivity while forming a dense SEI film. However, excessively high concentrations of the second additive slow down lithium-ion migration, increase battery polarization, and negatively impact cycle performance.

[0011] In some embodiments, the number of carbon atoms in the carbon-containing heterocyclic ring in the general structural formula of the second additive is 3 to 8.

[0012] Therefore, the second additive with the number of carbon atoms in the carbon heterocyclic ring within the above range has high solubility in the electrolyte, so as to obtain a second additive with a concentration of 0.33 mol / L to 0.37 mol / L.

[0013] In some embodiments, the carbon-containing heterocycle in the general structural formula of the second additive includes a substituent, which includes a nitrate group.

[0014] Therefore, the second additive molecule, which includes at least two nitrate groups, can be reduced and decomposed to obtain more lithium nitrogen oxides under the same molar amount, resulting in high utilization.

[0015] In some embodiments, the hydrofluoroether compound includes one or more of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (HFE), bis(2,2,2-trifluoroethyl) ether, 1,1,2,2-tetrafluoroethyl methyl ether, 1,1,2,2-tetrafluoroethyl ethyl ether, and 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether.

[0016] In some embodiments, the organic solvent includes one or more of ester organic solvents, ether organic solvents, sulfone organic solvents, and nitrile organic solvents.

[0017] In some embodiments, the ether organic solvent includes one of ethylene glycol dimethyl ether (DME), diethylene glycol dibutyl ether, 2-trifluoromethylhexafluoropropyl methyl ether, 2-trifluoromethylhexafluoropropyl ethyl ether, 2-trifluoromethylhexafluoropropyl propyl ether, 3-trifluoromethyloctafluorobutyl methyl ether, 3-trifluoromethyloctafluorobutyl ethyl ether, 3-trifluoromethyloctafluorobutyl propyl ether, 4-trifluoromethyldecafluoropentyl methyl ether, 4-trifluoromethyldecafluoropentyl ethyl ether, 4-trifluoromethyldecafluoropentyl propyl ether, 5-trifluoromethyldodecylfluorohexyl methyl ether, 5-trifluoromethyldodecylfluorohexyl ethyl ether, 5-trifluoromethyldodecylfluorohexyl propyl ether, 6-trifluoromethyltetradecylfluoroheptyl methyl ether, 6-trifluoromethyltetradecylfluoroheptyl ethyl ether, 6-trifluoromethyltetradecylfluoroheptyl propyl ether, 7-trifluoromethylhexadecylfluorooctyl methyl ether, 7-trifluoromethylhexadecylfluorooctyl ethyl ether, and 7-trifluoromethylhexadecylfluorooctyl propyl ether.

[0018] Therefore, the weak polarity of ether-based organic solvents reduces lithium salt solvation, decreases the proportion of solvated sheath, and results in a denser SEI film.

[0019] For example, the first additive, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, can act as a diluent. Through the inductive effect between electronegative fluorine and positively charged hydrogen, a solvent-solvent dipole-dipole interaction exists between it and DME, effectively regulating the solvation structure of Li ions, adjusting the kinetics and electrochemical stability of the Li ion-solvent-anion complex, and improving cycling performance. Furthermore, the second additive, such as isosorbide dinitrate, has good solubility in ether solvents like DME. The synergistic effect of these three additives results in a stable electrolyte system.

[0020] In some embodiments, the lithium salt includes one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethyl)sulfonylimide, lithium bis(pentafluoroethylsulfonyl)imide, lithium (fluorosulfonyl)(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, and lithium hexafluorophosphate.

[0021] In some embodiments, the concentration of lithium salt in the electrolyte is 1.8 mol / L to 2.2 mol / L.

[0022] In some embodiments, the carbonaceous material comprises 96% to 97% of the active material film. Thus, the negative electrode active material is primarily carbonaceous, which not only exhibits good performance in lithium ion extraction and insertion but also shows minimal volume change and good structural stability.

[0023] In some embodiments, in the Raman spectrum of carbonaceous materials, I d / I g The value is 0.83–0.88, I d This indicates that the Raman displacement is at 1300 cm. -1 ~1400cm-1 The d-peak intensity within the range, I g This indicates that the Raman shift is at 1530 cm. -1 ~1630cm -1 The intensity of the g peak within the range.

[0024] Therefore, based on the above electrolyte, combined with I d / I g Within the aforementioned range of carbonaceous materials, the defect sites of the carbonaceous materials can provide active sites for the second additive, promoting the second additive to be uniformly reduced and decomposed on the surface of the carbonaceous materials at a faster rate, forming lithium nitrogen oxides that participate in the formation of SEI, improving the stability of the SEI film, and reducing the decomposition of the electrolyte. When the two are used together, a battery cell with better cycle performance can be obtained.

[0025] In some embodiments, the BET specific surface area of ​​the carbonaceous material is 1.5–1.7 cm². 2 / g.

[0026] Therefore, the BET specific surface area of ​​carbonaceous materials within the above range is conducive to the penetration of electrolyte into the interior of the active material, reducing the time for electrolyte to wet the active material, shortening the lithium ion transport path, increasing the initial SEI film formation rate, and building a solid interface layer between the electrolyte and the active material at a faster speed, thereby improving cycle performance.

[0027] In some embodiments, the average particle size Dv50 of the carbonaceous material is 9.8 μm to 10.7 μm. Therefore, the carbonaceous material with an average particle size within this range can achieve a higher compaction density.

[0028] In some embodiments, the carbonaceous material includes one or more of natural graphite, artificial graphite, mesophase microcarbon spheres, soft carbon, and hard carbon.

[0029] In some embodiments, the battery cell further includes a positive electrode sheet, which comprises a current collector and a positive electrode active material film layer stacked together. The positive electrode active material film layer comprises lithium iron phosphate, a conductive agent, a binder, and a dispersant in a mass ratio of (96-98):(0.5-2):(0.5-2):(0-1.0). Therefore, based on the above-mentioned electrolyte and negative electrode sheet, the addition of the above-mentioned positive electrode sheet can yield a battery cell with superior cycle performance at both room temperature (25°C) and high temperature (45°C).

[0030] Secondly, embodiments of this application provide a battery including a housing and a battery cell according to any embodiment of the first aspect of this application, wherein the battery cell is housed within the housing.

[0031] Thirdly, embodiments of this application provide an electrical device configured to receive electrical energy supplied by a battery from any embodiment of the second aspect of this application. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some implementation methods of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0033] Figure 1 This is a schematic diagram of a secondary battery cell according to one embodiment of this application;

[0034] Figure 2 This is a schematic diagram of a battery module according to one embodiment of this application;

[0035] Figure 3 This is a schematic diagram of the structure of a battery pack according to one embodiment of this application;

[0036] Figure 4 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0037] The annotations in the attached figures are explained as follows:

[0038] 1. Battery pack; 4. Battery modules; 5. Individual battery cells.

[0039] The accompanying drawings are not necessarily drawn to scale. Detailed Implementation

[0040] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the conductive paste, current collector, secondary battery, battery module, battery pack, and power supply device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for a full understanding of this application by those skilled in the art and are not intended to limit the subject matter of the claims.

[0041] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0042] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0043] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0044] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0045] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0046] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0047] Unless otherwise specified, in this disclosure, the terms "first," "second," etc., are used to distinguish different objects, rather than to describe a specific order or primary / secondary relationship.

[0048] In this disclosure, the terms "multiple" or "a variety" refer to two or more kinds.

[0049] In the description of the embodiments of this disclosure, unless otherwise specified, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0050] Unless otherwise stated, the test temperature for all parameters mentioned in this disclosure is 25°C.

[0051] The secondary battery cell mentioned in the embodiments of this disclosure can independently perform charge and discharge functions. After discharge, it can be reactivated by charging to allow for continued use. The secondary battery cell can be cylindrical, cuboid, or other shapes, and the embodiments of this disclosure are not limited in this regard. Figure 1 This is a cuboid-shaped secondary battery cell used as an example.

[0052] The secondary battery cells provided in the embodiments of this disclosure may include, but are not limited to, lithium battery cells and sodium battery cells, such as lithium-ion battery cells, sodium-ion battery cells, lithium metal battery cells, sodium metal battery cells, etc. The secondary battery cells provided in the embodiments of this disclosure include electrode assemblies.

[0053] The electrode assembly can be a wound structure or a stacked structure, and this disclosure does not limit this. The secondary battery cell also includes an outer packaging, which can be used to encapsulate the electrode assembly. The outer packaging can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging can also be a flexible package, such as a pouch. The material of the flexible package can be plastic, such as one or more of aluminum-plastic film, polypropylene, polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0054] The battery apparatus mentioned in the embodiments of this disclosure may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple secondary battery cells connected in series, parallel, or mixed connections via a busbar. In some embodiments, the battery cell assembly is typically formed by arranging multiple secondary battery cells.

[0055] As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple secondary battery cells together to form an independent module. As another example, a battery module can be formed by bundling multiple secondary battery cells together with cable ties. Figure 2 This is a schematic diagram of a battery module as an example.

[0056] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more individual battery cells housed within the housing.

[0057] As an example, the battery cell assembly can be a battery module, and the battery cell assembly can be housed in the housing by fixing the battery module in the housing.

[0058] As an example, the battery cell assembly can also be housed within a housing by directly fixing multiple secondary battery cells to the housing. As an example, the housing may include a first housing and a second housing. The first and second housings are fastened together to form a closed space inside the housing for accommodating the battery cell assembly. Here, "closed" refers to covering or shutting off; it can be sealed or not sealed. The first housing may be a top cover or a bottom plate.

[0059] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the individual battery cells.

[0060] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0061] The technical solutions described in this disclosure are applicable to various electrical devices that use secondary battery cells or battery devices, such as, but not limited to, mobile devices (e.g., mobile phones, tablets, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc. Secondary battery cells and battery devices are used to store or provide electrical energy.

[0062] During the charging and discharging process of a battery, an SEI film is formed on the surface of the negative electrode. The SEI film is a passivation layer formed by the reaction of organic solvents and electrolyte salts on the surface of the negative electrode, which reduces the direct contact between the electrolyte and the active material of the negative electrode. During the formation of the SEI film, the electrolyte salts participate in the reaction, which causes the loss of lithium ions and affects the cycle performance. Therefore, the quality of the SEI film formation affects the performance of the battery.

[0063] In view of the above problems, this application proposes a battery cell, which includes a negative electrode and an electrolyte. The negative electrode includes a current collector and an active material film layer containing active material particles stacked on top of each other. The active material particles include carbonaceous materials. The electrolyte includes lithium salt, organic solvent, and additives. The additives include a first additive and a second additive. The first additive includes a hydrofluoroether compound, which can reduce the lithium-ion solvation ratio and generate a more stable SEI film. The second additive has a general structural formula including NO3-R1, where R1 includes substituted or unsubstituted carbon-containing heterocycles, which are reduced and decomposed on the surface of the carbonaceous material to generate lithium nitrogen oxides. The lithium nitrogen oxides participate in the formation of the SEI film, filling the pores or defects of the SEI film, further increasing the inorganic content of the SEI film while improving the density and stability of the SEI film. Thus, a dense, stable composite SEI film with a high inorganic content is formed on the surface of the carbonaceous material, forming a stable interface layer between the carbonaceous material and the organic solvent, reducing side reactions between the carbonaceous material and the electrolyte, reducing lithium consumption, and improving cycle performance. On the other hand, composite SEI films with high inorganic content can reduce the transmission impedance of lithium ions through the SEI film and increase the rate of lithium ion extraction and insertion in carbonaceous materials, thereby improving cycle performance.

[0064] The technical solutions of the embodiments of this application will now be described in detail.

[0065] battery cell

[0066] In a first aspect, embodiments of this application propose a battery cell, which includes a negative electrode and an electrolyte. The negative electrode includes a current collector and an active material film containing active material particles stacked together, the active material particles including carbonaceous materials. The electrolyte includes lithium salt, organic solvent and additives. The additives include a first additive and a second additive. The first additive includes a hydrofluoroether compound. The second additive has a general structural formula including NO3-R1, wherein R1 includes substituted or unsubstituted carbon-containing heterocycles.

[0067] In electrolytes, lithium ions undergo solvation to form a solvation sheath. Anions preferentially participate in the formation of the SEI film by reducing and decomposing solvent molecules on the carbonaceous material surface. When solvated lithium ions intercalate at the interface, they easily induce solvent molecule intercalation, leading to SEI film instability. The first additive in the electrolyte, a hydrofluoroether compound, can reduce the proportion of lithium ion solvation, resulting in a more stable SEI film. Furthermore, a second additive containing a carbon-containing heterocyclic nitrate group is added. This second additive is reduced and decomposed on the carbonaceous material surface to form lithium oxide nitrides. These lithium oxide nitrides participate in SEI film formation, filling the pores or defects of the SEI film. This further increases the inorganic content of the SEI film while improving its density and stability. Thus, a dense, stable, and high-inorganic-content composite SEI film is formed on the carbonaceous material surface, creating a stable interface layer between the carbonaceous material and the organic solvent. This reduces side reactions between the carbonaceous material and the electrolyte, lowers lithium consumption, and improves cycle performance. On the other hand, composite SEI films with high inorganic content can reduce the transmission impedance of lithium ions through the SEI film and increase the rate of lithium ion extraction and insertion in carbonaceous materials, thereby improving cycle performance.

[0068] Electrolyte

[0069] In some embodiments, the battery cell includes an electrolyte comprising a lithium salt, an organic solvent, and an additive; the additive includes a first additive and a second additive, the first additive comprising a hydrofluoroether compound; the second additive has a general structural formula including NO3-R1, wherein R1 comprises a substituted or unsubstituted carbon-containing heterocycle.

[0070] In electrolytes, lithium ions undergo solvation to form a solvation sheath. Anions preferentially participate in the formation of the SEI film by reducing and decomposing solvent molecules on the carbonaceous material surface. When solvated lithium ions intercalate at the interface, they easily induce solvent molecule intercalation, leading to SEI film instability. The first additive in the electrolyte, a hydrofluoroether compound, can reduce the proportion of lithium ion solvation, resulting in a more stable SEI film. Furthermore, a second additive containing a carbon-containing heterocyclic nitrate group is added. This second additive is reduced and decomposed on the carbonaceous material surface to form lithium oxide nitrides. These lithium oxide nitrides participate in SEI film formation, filling the pores or defects of the SEI film. This further increases the inorganic content of the SEI film while improving its density and stability. Thus, a dense, stable, and high-inorganic-content composite SEI film is formed on the carbonaceous material surface, creating a stable interface layer between the carbonaceous material and the organic solvent. This reduces side reactions between the carbonaceous material and the electrolyte, lowers lithium consumption, and improves cycle performance. On the other hand, composite SEI films with high inorganic content can reduce the transmission impedance of lithium ions through the SEI film and increase the rate of lithium ion extraction and insertion in carbonaceous materials, thereby improving cycle performance.

[0071] In the embodiments of this application, the types and contents of organic components in the electrolyte are defined in the art and can be detected using equipment and methods known in the art. For example, the organic components in the electrolyte can be qualitatively and quantitatively analyzed by gas chromatography using GB / T9722-2006 "General Rules for Gas Chromatography of Chemical Reagents". In the embodiments of this application, freshly prepared electrolyte can be used as a sample, or a fully discharged battery (discharged to the lower limit cutoff voltage so that the battery's state of charge is approximately 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery can be used as a sample for detection using ion chromatography.

[0072] For example, when testing the composition of an additive in an electrolyte using liquid chromatography-nuclear magnetic resonance (NMR), taking the detection of hydrofluoroether compounds such as 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether as an example, a 7ml glass bottle is prepared in a nitrogen-filled glove box. 5ml of NMR reagent premix is ​​added to the bottle, and the mixture is left to stand at room temperature (20-25°C) for 4 hours in the nitrogen-filled glove box. This allows the electrolyte in the electrode and separator to diffuse into the NMR premix, thus obtaining the NMR test sample. The NMR premix consists of 100ml of deuterated acetonitrile with 3ml of trifluoromethylbenzene CF3ph. This NMR reagent premix is ​​pre-dried using molecular sieve 4A (100ml of NMR reagent premix is ​​added to 15g of freshly opened 4A molecular sieve and dried in a nitrogen-filled glove box at room temperature (20-25°C) for more than 30 days). Measurements were performed using 19F NMR (NMR: Bruker Avance 400HD).

[0073] In some embodiments, the volume ratio of the first additive to the organic solvent is 1:(0.6 to 0.7).

[0074] The volume ratio of the first additive to the organic solvent is within the above range, which gives the electrolyte a suitable viscosity, enhances the interaction between lithium ions and anions, and increases the rate at which anions participate in the SEI film, so as to obtain an SEI film with high inorganic salt content.

[0075] For example, the ratio of the first additive to the organic solvent can be 1:0.60, 1:0.61, 1:0.62, 1:0.63, 1:0.64, 1:0.65, 1:0.66, 1:0.67, 1:0.68, 1:0.69, 1:0.70, or any range of two of the above values.

[0076] In some embodiments, the concentration of the second additive in the electrolyte is 0.33 mol / L to 0.37 mol / L.

[0077] The second additive is a carbon-containing heterocyclic substance with a nitrate group. It has high solubility in the electrolyte, allowing for the acquisition of the second additive within the aforementioned concentration range. A molar concentration of the second additive within this range ensures an appropriate amount of lithium oxide nitride in the SEI film. Lithium oxide nitride exhibits high lithium-ion conductivity, achieving good lithium-ion conductivity while forming a dense SEI film. However, excessively high concentrations of the second additive slow down lithium-ion migration, increasing battery polarization and negatively impacting cycle performance.

[0078] For example, the concentration of the second additive in the electrolyte can be 0.330 mol / L, 0.335 mol / L, 0.340 mol / L, 0.345 mol / L, 0.350 mol / L, 0.355 mol / L, 0.360 mol / L, 0.365 mol / L, 0.370 mol / L, or any range of two of the above values.

[0079] In some embodiments, the number of carbon atoms in the carbon-containing heterocyclic ring in the general structural formula of the second additive is 3 to 8.

[0080] The second additive containing carbon heterocycles with the number of carbon atoms within the above range has high solubility in the electrolyte, so as to obtain a second additive with a concentration of 0.33 mol / L to 0.37 mol / L.

[0081] For example, the number of carbon atoms in a carbon-containing heterocycle can be 3, 4, 5, 6, 7, 8, or any range of two of the above values.

[0082] In some embodiments, the carbon-containing heterocycle in the general structural formula of the second additive includes a substituent, which includes a nitrate group.

[0083] The second additive molecule, which includes at least two nitrate groups, can be reduced and decomposed to obtain more lithium nitrogen oxides under the same molar amount. This not only has high utilization rate, but can also further increase the inorganic component content of the SEI membrane and improve cycle performance.

[0084] In some embodiments, the second additive includes one or more of isosorbide dinitrate (ISDN) and isosorbide 5-mononitrate.

[0085] In some embodiments, the hydrofluoroether compound includes one or more of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, bis(2,2,2-trifluoroethyl) ether, 1,1,2,2-tetrafluoroethyl methyl ether, 1,1,2,2-tetrafluoroethyl ethyl ether, and 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether.

[0086] For example, the first additive, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, can be used as a diluent. It has a solvent-solvent dipole-dipole interaction with DME through the inductive effect between the electronegative fluorine and the positive hydrogen, which can effectively regulate the solvation structure of Li ions, adjust the kinetics and electrochemical stability of Li ion-solvent-anion complex, and improve cycle performance.

[0087] In some embodiments, the organic solvent includes one or more of ester organic solvents, ether organic solvents, sulfone organic solvents, and nitrile organic solvents.

[0088] In some embodiments, the ether organic solvent includes one or more of the following: ethylene glycol dimethyl ether (DME), diethylene glycol dibutyl ether, 2-trifluoromethylhexafluoropropyl methyl ether, 2-trifluoromethylhexafluoropropyl ethyl ether, 2-trifluoromethylhexafluoropropyl propyl ether, 3-trifluoromethyloctafluorobutyl methyl ether, 3-trifluoromethyloctafluorobutyl ethyl ether, 3-trifluoromethyloctafluorobutyl propyl ether, 4-trifluoromethyldecafluoropentyl methyl ether, 4-trifluoromethyldecafluoropentyl ethyl ether, 4-trifluoromethyldecafluoropentyl propyl ether, 5-trifluoromethyldodecylfluorohexyl methyl ether, 5-trifluoromethyldodecylfluorohexyl ethyl ether, 5-trifluoromethyldodecylfluorohexyl propyl ether, 6-trifluoromethyltetradecylfluoroheptyl methyl ether, 6-trifluoromethyltetradecylfluoroheptyl ethyl ether, 6-trifluoromethyltetradecylfluoroheptyl propyl ether, 7-trifluoromethylhexadecylfluorooctyl methyl ether, 7-trifluoromethylhexadecylfluorooctyl ethyl ether, and 7-trifluoromethylhexadecylfluorooctyl propyl ether.

[0089] Ether-based organic solvents have weak polarity, which reduces lithium salt solvation, lowers the solvated sheath ratio, and makes the SEI film more dense.

[0090] Furthermore, the second additive, such as isosorbide dinitrate, has good solubility in ether solvents such as DME. Hydrofluoroether compounds act as diluents for the aforementioned organic solvents. The three work synergistically to obtain a stable electrolyte system.

[0091] In some embodiments, the ester organic solvent includes one or more of carbonates, phosphate esters, carboxylic esters, sulfate esters, sulfonates, etc. The carbonate may include cyclic carbonates and / or chain carbonates; optionally, the carbonate may include both cyclic and chain carbonates. Chain carbonates may include low-viscosity polar chain carbonates, aliphatic branched carbonates, etc.

[0092] In some embodiments, the ester organic solvent includes one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), butene carbonate, ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), and 1,4-butyrolactone (GBL).

[0093] In some embodiments, the lithium salt includes one or more of lithium bis(fluorosulfonyl)imide (LiFSI'), lithium bis(trifluoromethyl)sulfonylimide, lithium bis(pentafluoroethylsulfonyl)imide, lithium (fluorosulfonyl)(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, and lithium hexafluorophosphate.

[0094] In some embodiments, the concentration of lithium salt in the electrolyte is 1.8 mol / L to 2.2 mol / L.

[0095] For example, the concentration of lithium salt in the electrolyte can be 1.80 mol / L, 1.85 mol / L, 1.90 mol / L, 1.95 mol / L, 2.00 mol / L, 2.05 mol / L, 2.10 mol / L, 2.15 mol / L, 2.20 mol / L, or any range of two of the above values.

[0096] [Negative electrode plate]

[0097] A single battery cell includes a negative electrode and an electrolyte. The negative electrode includes a current collector stacked on top of a film containing active material particles, which include carbonaceous materials.

[0098] In some embodiments, the mass fraction of carbonaceous material in the active material film layer is 96% to 97%.

[0099] The main active material of the negative electrode is carbonaceous material. Carbonaceous materials not only have good performance in extracting and inserting lithium ions, but also have small volume change and good structural stability.

[0100] For example, the mass fraction of carbonaceous material in the active material film layer can be 96.00%, 96.05%, 96.10%, 96.15%, 96.20%, 96.25%, 96.30%, 96.35%, 96.40%, 96.45%, 96.50%, 96.55%, 96.60%, 96.65%, 96.70%, 96.75%, 96.80%, 96.85%, 96.90%, 96.95%, 97.00%, or a range of any two of the above values.

[0101] In some embodiments, in the Raman spectrum of carbonaceous materials, I d / I g The value is 0.83–0.88, I d This indicates that the Raman displacement is at 1300 cm. -1 ~1400cm -1 The d-peak intensity within the range, where Ig represents the Raman shift at 1530 cm⁻¹. -1 ~1630cm -1 The intensity of the g peak within the range.

[0102] Based on the above electrolyte, carbonaceous materials with Id / Ig within the above range are combined. The defect sites of the carbonaceous materials can provide active sites for the second additive, promoting the uniform reduction and decomposition of the second additive on the surface of the carbonaceous materials at a faster rate, forming lithium nitrogen oxides to participate in the formation of SEI, improving the stability of the SEI film, and reducing the decomposition of the electrolyte. The two work together to obtain battery cells with better cycle performance.

[0103] For example, I d / I g It can be 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, or a range consisting of any two of the above values.

[0104] In the embodiments of this application, I d / I gAs is known in the art, detection can be performed using equipment and methods known in the art. As a specific example, the Raman spectrum of carbonaceous materials can be tested using a Raman spectrometer. During testing, the d-peak intensity and g-peak intensity of 100 points are acquired, and the Id / Ig ratio of these 100 points is calculated. The 30 highest and 30 lowest Id / Ig values ​​are removed, and the average of the remaining 40 Id / Ig values ​​is taken as the Id / Ig ratio of the carbonaceous material. The testing instrument can be a Horiba LabRAM HR800 Raman spectrometer. The testing conditions can be: excitation wavelength 532 nm, grating 600 lines, objective lens 50x, integration time 10 s, cumulative scan 3 times, and area scan.

[0105] In some embodiments, the BET specific surface area of ​​the carbonaceous material is 1.5–1.7 cm². 2 / g.

[0106] The BET specific surface area of ​​carbonaceous materials within the above range is conducive to the penetration of electrolyte into the interior of the active material, reducing the time for electrolyte to wet the active material, shortening the lithium ion transport path, increasing the initial SEI film formation rate, and building a solid interface layer between the electrolyte and the active material at a faster speed, thereby improving cycle performance.

[0107] For example, the BET specific surface area of ​​carbonaceous materials can be 1.5 cm². 2 / g, 1.55cm 2 / g, 1.60cm 2 / g, 1.65cm 2 / g, 1.7cm 2 / g or a range consisting of any two of the above values.

[0108] In this application, specific surface area has a meaning known in the art and can be detected using equipment and methods known in the art. As a specific example, carbonaceous material is dried in a vacuum drying oven at 200°C for 2 hours; then, nitrogen or argon is used as the adsorption gas, and adsorption-desorption curves with relative pressure P / P0 of 0–0.99 are plotted using a specific surface area and porosity analyzer. The BET specific surface area of ​​the carbonaceous material is calculated using the BET method. When the test sample is a negative electrode sheet, the active material layer can be dissolved using a suitable solvent, ultrasonically dispersed, and the conductive agent particles removed by centrifugation. The resulting powder is then dried to obtain the negative electrode active material powder, and the specific surface area of ​​the negative electrode active material is tested using the above-described testing method.

[0109] In some embodiments, the average particle size Dv50 of the carbonaceous material is 9.8 μm to 10.7 μm. The carbonaceous material with an average particle size within this range can also achieve a higher compaction density.

[0110] For example, the average particle size Dv50 of the carbonaceous material can be 9.8 μm, 9.9 μm, 10.0 μm, 10.1 μm, 10.2 μm, 10.3 μm, 10.4 μm, 10.5 μm, 10.6 μm, 10.7 μm or any range of two of the above values.

[0111] In this application, Dv50 has a well-known meaning in the art and can be detected using well-known equipment and methods. Relevant detection methods can refer to domestic and international testing standards and enterprise standards. Furthermore, those skilled in the art can adapt certain detection steps / instrument parameters from the perspective of detection accuracy to obtain more accurate results. Particle size distribution can be conveniently determined using a laser particle size analyzer, such as the Mastersizer 2000E laser particle size analyzer from Malvern Instruments Ltd., UK, according to GB / T 19077-2016, laser diffraction method. The specific principle is that the particle sample is dispersed at an appropriate concentration in a suitable liquid and gas, and then passed through a monochromatic beam (usually a laser). When the light encounters the particles, it scatters at different angles. A multi-element detector measures the scattered light, stores these values ​​related to the scattering pattern, and uses them for subsequent analysis. Through appropriate optical models and mathematical processes, these quantified scattering data are converted to obtain a series of discrete particle size ranges representing the percentage of particle volume relative to the total particle volume, thus obtaining the particle size volume distribution, where Dv50 is the average particle size volume distribution.

[0112] In some embodiments, the carbonaceous material includes one or more of natural graphite, artificial graphite, mesophase microcarbon spheres, soft carbon, and hard carbon.

[0113] In some embodiments, the active material film layer further includes a negative electrode conductive agent, which may include, but is not limited to, one or more of conductive graphite (such as KS-6, SFG-6), superconducting carbon, acetylene black, carbon black (such as SP), Ketjen black (such as ECP), carbon dots, carbon nanotubes, graphene, carbon nanofibers, and vapor-grown carbon fibers (VGCF).

[0114] In some embodiments, the active material film layer further includes a negative electrode binder, which may include, but is not limited to, one or more of the following: styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, polyacrylic acid, polymethacrylic acid, sodium polyacrylate, polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), carboxymethyl chitosan (CMCS), methyl vinyl silicone rubber, nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), thermoplastic styrene-butadiene rubber (SBS), isoprene rubber, cis-butadiene rubber (BR), ethyl cellulose, fluororubber, and acrylate rubber.

[0115] In some implementations, the current collector can be a metal foil, a three-dimensional porous current collector, or a composite current collector.

[0116] Examples of metal foils include copper foil, copper alloy foil, nickel foil, nickel alloy foil, aluminum foil, and aluminum alloy foil. Examples of three-dimensional porous current collectors include copper mesh, nickel mesh, aluminum mesh, copper foam, nickel foam, and aluminum foam. Composite current collectors may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As examples, the metal material may include, but is not limited to, one or more of copper, copper alloys, aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As examples, the polymer material base layer may include, but is not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene, and polyethylene.

[0117] [Positive electrode tablets]

[0118] In some embodiments, the battery cell further includes a positive electrode sheet, which includes a current collector and a positive electrode active material film layer stacked together. The positive electrode active material film layer includes a positive electrode active material, which includes a material capable of extracting and inserting lithium.

[0119] In some embodiments, the positive electrode active material may include, but is not limited to, one or more of lithium transition metal oxides, metal chalcogenides, lithium-containing phosphates, and their respective modified compounds.

[0120] As an example, examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxides, lithium nickel oxides, lithium manganese oxides, lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides, lithium nickel cobalt aluminum oxides, lithium titanium oxides, and their respective modified compounds. Lithium transition metal oxides may include, but are not limited to, layered structures and spinel structures.

[0121] As an example, lithium phosphates may include, but are not limited to, one or more of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, lithium manganese iron phosphate and carbon composites, and their respective modified compounds.

[0122] As an example, the positive electrode active material may include, but is not limited to, LiCoO2, LiNiO2, LiMnO2, and LiNi 1 / 2 Mn 1 / 2O2, LiMn2O4, Li 4 / 3 Ti 5 / 3 O4, LiNi 1 / 2 Mn 1 / 2 O2, LiNi 1 / 3 Co1 / 3 Mn 1 / 3 O2(NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), LiNi 0.80 Co 0.15 Al 0.05 O2, LiFePO4, LiMnPO4, Li 1.13 Ti 0.57 Fe 0.3 One or more of S2

[0123] In some embodiments, the positive electrode active material may simultaneously comprise lithium transition metal oxide and lithium phosphate. This is advantageous for obtaining battery cells that balance high capacity and high reliability.

[0124] In some embodiments, the positive electrode includes a current collector and a positive electrode active material film stacked together. The positive electrode active material film comprises lithium iron phosphate, a conductive agent, a binder, and a dispersant in a mass ratio of (96-98):(0.5-2):(0.5-2):(0-1.0). Based on the above electrolyte and negative electrode, the above positive electrode can be used to obtain a battery cell with better cycle performance at both room temperature (25°C) and high temperature (45°C).

[0125] In some embodiments, the conductive agent may be one or more of the following: conductive graphite (such as KS-6, SFG-6), superconducting carbon, acetylene black, carbon black (such as SP), Ketjen black (such as ECP), carbon dots, carbon nanotubes, graphene, carbon nanofibers, and vapor-grown carbon fibers (VGCF).

[0126] In some embodiments, the adhesive may include, but is not limited to, one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene-propylene terpolymer, ethylene-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, water-soluble unsaturated resin, methyl vinyl silicone rubber, nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), styrene-butadiene rubber (SBR), thermoplastic styrene-butadiene rubber (SBS), isoprene rubber, ethyl cellulose, polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), carboxymethyl chitosan (CMCS), fluororubber, and acrylate rubber.

[0127] In some embodiments, the positive current collector can be a metal foil or a composite current collector. Examples of metal foils include stainless steel foil, carbon-coated aluminum foil, aluminum foil, nickel foil, and titanium foil. The composite current collector can include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. Examples of metal materials include, but are not limited to, one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Examples of polymer substrates include, but are not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene.

[0128] [Isolation Component]

[0129] In some embodiments, the battery cell also includes a separator disposed between the positive electrode and the negative electrode.

[0130] In some embodiments, the isolation chamber includes an isolation membrane. This application does not impose any particular limitation on the type of isolation membrane; any known porous membrane with good chemical and mechanical stability can be selected.

[0131] In some embodiments, the material of the separator may include at least one selected from glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation. The separator may be a single component located between the positive and negative electrodes, or it may be attached to the surfaces of the positive and negative electrodes. An inorganic particle coating, an organic particle coating, or an organic / inorganic composite coating may also be applied to the surface of the separator.

[0132] In some embodiments, the separator is a solid electrolyte. The solid electrolyte is disposed between the positive and negative electrodes, serving both to transport ions and to isolate the positive and negative electrodes.

[0133] Battery

[0134] Secondly, embodiments of this application provide a battery including a housing and a battery cell according to any embodiment of the first aspect of this application, wherein the battery cell is housed within the housing.

[0135] Figure 3 This is a schematic diagram illustrating the structure of a battery pack as an example. The battery pack may include a battery compartment and multiple battery modules housed within it. The battery compartment comprises an upper body and a lower body, with the upper body covering the lower body and forming a closed space for accommodating the battery modules. The multiple battery modules can be arranged in any manner within the battery compartment.

[0136] Electrical appliances

[0137] A third aspect of this application provides an electrical device, which includes at least one of the battery cell, battery module, or battery pack described in this application. The battery cell, battery module, or battery pack can be used as the power source for the electrical device or as the energy storage unit of the electrical device. The electrical device can be, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0138] Electrical devices can be equipped with individual battery cells, battery modules, or battery packs depending on their usage requirements.

[0139] Figure 4 This is a schematic diagram of an example electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the device's requirements for high power and high energy density, a battery pack or battery module can be used.

[0140] Another example of an electrical device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0141] Example

[0142] The following embodiments describe the contents disclosed in this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of the embodiments of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0143] Example 1

[0144] 1. Preparation of positive electrode sheet

[0145] Lithium iron phosphate (with a specific capacity of 145 mAh / g), acetylene black as a conductive agent, PVDF as a binder, and sodium carboxymethyl cellulose were mixed in N-methylpyrrolidone at a mass ratio of 96.5:1:2:0.5. The mixture was stirred and mixed thoroughly to obtain a positive electrode slurry, which was then coated onto an aluminum foil current collector, dried, and cold-pressed to obtain a positive electrode sheet.

[0146] 2. Preparation of negative electrode sheet

[0147] Weigh out the negative electrode active material graphite, conductive agent carbon black, and binder styrene-butadiene rubber (SBR), dissolve them in deionized water, stir evenly to prepare a negative electrode slurry, uniformly coat it on the surface of the negative electrode current collector copper foil, and form an active material layer after drying and cold pressing. The negative electrode active material layer includes negative electrode active material graphite, conductive agent carbon black (Super P), binder SBR and dispersant in a weight ratio of 97%:0.5%:2%:0.5%.

[0148] 3. Separating membrane

[0149] The separator is made of porous polypropylene (PP) (7μm).

[0150] 4. Preparation of electrolyte

[0151] In an argon-atmospheric glove box, LiFSI (lithium bisfluorosulfonylimide) was mixed in HFE (1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether) at a weight ratio of 1:2.48, and ISDN (isosorbide dinitrate) was mixed in DME (ethylene glycol dimethyl ether) at a weight ratio of 1:4.04. The HFE solution and DME solution were then mixed at a mass ratio of 3.22:1, resulting in a final LiFSI:ISDN:DME:HFE molar ratio of 1.0: The electrolyte was prepared by mixing an amount of 0.17:1.8:2.0, with ISDN mass fraction of 4.69% (molar concentration of 0.348 mol / L, abbreviated as n(ISDN)), LiFSI mass fraction of 21.92% (molar concentration of 2.04 mol / L, abbreviated as n(LiFSI)), DME mass fraction of 18.99%, and HFE mass fraction of 54.40% (molar concentration of 4.09 mol / L, abbreviated as n(HFE)). The mixture was stirred thoroughly to obtain the electrolyte. The volume ratio of HFE to DME was 1:0.62.

[0152] 5. Battery manufacturing

[0153] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. The electrode assembly is then wound up to obtain an electrode assembly. The electrode assembly is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, electrolyte injection, settling, formation, and shaping, a lithium-ion battery is obtained.

[0154] Examples 2-10

[0155] Lithium-ion batteries were prepared using a method similar to that of Example 1. The differences in preparation parameters compared to Example 1 are shown in Table 1.

[0156] The difference between Examples 2 and 3 and Example 1 is that the concentration of ISDN is different.

[0157] The difference between Example 4 and Example 1 is that ISDN is replaced with nitrobenzene.

[0158] The difference between Example 5 and Example 1 is that ISDN is replaced with sorbitol 5-mononitrate.

[0159] The difference between Example 6 and Example 1 is that the lithium salt LiFSI is replaced with LiPF6.

[0160] The difference between Example 7 and Example 1 is that HFE is replaced with ethyl methyl carbonate (EMC).

[0161] Example 8 differs from Example 1 in that the negative electrode material is replaced with a silicon-carbon composite material. d / Ig =0.857, BET specific surface area is 1.51cm² 2 / g, Dv50 is 9.3μm.

[0162] The difference between Examples 9 and 10 and Example 1 is that the specific surface area of ​​the negative electrode graphite material is different.

[0163] Comparative Example 1

[0164] Lithium-ion batteries were prepared using a method similar to that of Example 1, except that the electrolyte did not contain the second additive ISDN.

[0165] Comparative Example 2

[0166] Lithium-ion batteries were prepared using a method similar to that of Example 1, except that the electrolyte did not contain the first additive HFE.

[0167] Performance testing

[0168] 1. Cyclic test at room temperature (25℃)

[0169] At 25℃, fresh battery cells were placed on a high-temperature chamber for testing. The cells were sequentially charged to 3.65V at a power of 0.5P, allowed to rest for 30 minutes, and then charged to 3.65V at a constant power of 0.05P, and allowed to rest for another 30 minutes. After charging, the cells were discharged to 2.5V at a constant current of 0.5P. This completed one charge-discharge cycle. This process was repeated until the discharge capacity decreased to 80%, and the number of cycles was recorded.

[0170] 2. Cyclic test at high temperature (45℃)

[0171] Fresh battery cells were placed in a high-temperature chamber at 45℃ for testing. The cells were charged sequentially at 0.5P to 3.65V, allowed to rest for 30 minutes, and then charged again at a constant power of 0.05P to 3.65V, and allowed to rest for 30 minutes. After charging, the cells were discharged at a constant current of 0.5P to 2.5V, thus completing one full charge-discharge cycle. This process was repeated until the discharge capacity decreased to 80%, and the number of cycles was recorded.

[0172] The performance test results are shown in Table 1.

[0173] Table 1:

[0174]

[0175] As shown in Table 1, the battery cells of Examples 1-10 of this application exhibit superior cycle performance compared to the comparative examples. This demonstrates that the combination of the negative electrode active material and electrolyte in this application can improve the cycle performance of the battery cells. A dense, stable, and inorganic-rich composite SEI film is formed on the surface of carbonaceous materials such as graphite negative electrodes, creating a stable interface layer between the carbonaceous materials and organic solvents. This reduces side reactions between the carbonaceous materials and the electrolyte, lowers lithium consumption, and thus improves cycle performance. Comparative Example 1 did not contain ISDN in its electrolyte, and Comparative Example 2 did not contain HFE in its electrolyte; both showed inferior cycle performance compared to the examples.

[0176] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the present application, and that changes, substitutions and modifications can be made to the embodiments without departing from the spirit, principles and scope of the present application.

Claims

1. A battery cell, characterized in that, The battery cell includes a negative electrode and an electrolyte. The negative electrode includes a current collector and an active material film containing active material particles stacked on top of each other. The active material particles include carbonaceous materials. The electrolyte includes lithium salt, organic solvent and additives. The additives include a first additive and a second additive. The first additive includes a hydrofluoroether compound. The second additive has a general structural formula including NO3-R1, wherein R1 includes a substituted or unsubstituted carbon-containing heterocycle.

2. The battery cell according to claim 2, characterized in that, The electrolyte must satisfy at least one of the following characteristics: (1) The volume ratio of the first additive to the organic solvent is 1:(0.6-0.7); (2) The concentration of the second additive in the electrolyte is 0.33 mol / L to 0.37 mol / L.

3. The battery cell according to claim 1, characterized in that, In the general structural formula of the second additive, the carbon-containing heterocycle has 3 to 8 carbon atoms.

4. The battery cell according to claim 1, characterized in that, In the general structural formula of the second additive, the carbon-containing heterocycle includes substituents, and the substituents include nitrate groups.

5. The battery cell according to claim 1, characterized in that, The hydrofluoroether compound includes one or more of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, bis(2,2,2-trifluoroethyl) ether, 1,1,2,2-tetrafluoroethyl methyl ether, 1,1,2,2-tetrafluoroethyl ethyl ether, and 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether.

6. The battery cell according to any one of claims 1 to 5, characterized in that, The organic solvent includes one or more of ester organic solvents and ether organic solvents.

7. The battery cell according to claim 6, characterized in that, The ether organic solvents include one or more of the following: ethylene glycol dimethyl ether, diethylene glycol dibutyl ether, 2-trifluoromethylhexafluoropropyl methyl ether, 2-trifluoromethylhexafluoropropyl ethyl ether, 2-trifluoromethylhexafluoropropyl propyl ether, 3-trifluoromethyloctafluorobutyl methyl ether, 3-trifluoromethyloctafluorobutyl ethyl ether, 3-trifluoromethyloctafluorobutyl propyl ether, 4-trifluoromethyldecafluoropentyl methyl ether, 4-trifluoromethyldecafluoropentyl ethyl ether, 4-trifluoromethyldecafluoropentyl propyl ether, 5-trifluoromethyldodecylfluorohexyl methyl ether, 5-trifluoromethyldodecylfluorohexyl ethyl ether, 5-trifluoromethyldodecylfluorohexyl propyl ether, 6-trifluoromethyltetradecylfluoroheptyl methyl ether, 6-trifluoromethyltetradecylfluoroheptyl ethyl ether, 6-trifluoromethyltetradecylfluoroheptyl propyl ether, 7-trifluoromethylhexadecylfluorooctyl methyl ether, 7-trifluoromethylhexadecylfluorooctyl ethyl ether, and 7-trifluoromethylhexadecylfluorooctyl propyl ether.

8. The battery cell according to any one of claims 1 to 7, characterized in that, The lithium salt includes one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethyl)sulfonylimide, lithium bis(pentafluoroethylsulfonyl)imide, lithium (fluorosulfonyl)(trifluoromethanesulfonyl)imide, and lithium trifluoromethanesulfonate and lithium hexafluorophosphate.

9. The battery cell according to claim 8, characterized in that, The concentration of the lithium salt in the electrolyte is 1.8 mol / L to 2.2 mol / L.

10. The battery cell according to any one of claims 1 to 9, characterized in that, The carbonaceous material has a mass fraction of 96% to 97% in the active material film layer.

11. The battery cell according to claim 10, characterized in that, In the Raman spectrum of the carbonaceous material, I d / I g is 0.83 to 0.88, I d represents the intensity of the d-peak with a Raman shift in the range of 1300 cm -1 to 1400 cm -1 , I g represents the intensity of the g-peak with a Raman shift in the range of 1530 cm -1 to 1630 cm -1 .

12. The battery cell according to claim 11, characterized in that, The BET specific surface area of ​​the carbonaceous material is 1.5–1.7 cm². 2 / g.

13. The battery cell according to any one of claims 10 to 12, characterized in that, The average particle size Dv50 of the carbonaceous material is 9.8 μm to 10.7 μm.

14. The battery cell according to any one of claims 10 to 13, characterized in that, The carbonaceous material includes one or more of the following: natural graphite, artificial graphite, mesophase microcarbon spheres, soft carbon, and hard carbon.

15. The battery cell according to any one of claims 1 to 14, characterized in that, The battery cell further includes a positive electrode sheet, which includes a current collector and a positive electrode active material film layer stacked together. The positive electrode active material film layer includes lithium iron phosphate, a conductive agent, a binder, and a dispersant in a mass ratio of (96-98):(0.5-2):(0.5-2):(0-1.0).

16. A battery, characterized in that, It includes a housing and at least one battery cell as described in any one of claims 1 to 15, wherein the battery cell is housed within the housing.

17. An electrical device, characterized in that, The electrical device is configured to receive electrical energy supplied from the battery of claim 16.

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