A lithium-ion battery electrolyte and products comprising the same

Abstract

The present application relates to a lithium ion battery electrolyte and products containing the same, the lithium ion battery electrolyte comprising a solvent, a lithium salt and an additive; wherein the additive comprises a sulfur-containing additive, the structural formula of the sulfur-containing additive is R 1 -(S) n -R 2 (Formula I); n is an integer selected from 3-6; R 1 , R 2 are each independently selected from any one of the following group of unsubstituted or substituted groups: alkyl, alkenyl, alkynyl, aryl; and R 1 and / or R 2 comprise one or two elements selected from the following group: N, O. By applying the lithium ion battery electrolyte, a dense and stable SEI film can be formed during the formation stage, and has the advantages of fast film formation and high film formation efficiency, thereby effectively improving the performance of the battery.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery technology, specifically to a lithium-ion battery electrolyte and products containing the same. Background Technology

[0002] During the first charge of a lithium-ion battery, lithium ions are extracted from the lattice of the positive electrode active material and migrate towards the negative electrode under voltage, embedding themselves into the carbon material. During this process, the electrolyte reacts with the carbon negative electrode surface, producing substances such as Li₂CO₃, Li₂O, and LiOH, thus forming a passivation film on the carbon negative electrode surface. This passivation film is called the solid electrolyte interphase (SEI) film. Simultaneously, the electrolyte reacts with the positive electrode surface to form a passivation film thinner than the SEI film, called the CEI film. Since lithium ions must pass through both the CEI and SEI films during both charging and discharging, the composition and properties of these films determine many battery performance characteristics, such as cycle performance, high-temperature performance, and rate performance.

[0003] To improve battery performance, existing technologies have reported improvements in electrolyte film-forming additives, including boron-containing additives, organophosphorus additives, carbonate additives, sulfur-containing additives, and ionic liquid additives. Those skilled in the art desire to develop new electrolyte additives and electrolytes to further improve lithium-ion battery performance. Summary of the Invention

[0004] The purpose of this application is to provide a lithium-ion battery electrolyte and a product containing the same. By applying this lithium-ion battery electrolyte, a dense and stable SEI film can be formed during the formation stage, and it has the advantages of fast film formation and high film formation efficiency, thereby effectively improving the performance of the battery.

[0005] Therefore, in a first aspect, this application provides a lithium-ion battery electrolyte, the lithium-ion battery electrolyte comprising a solvent, a lithium salt, and an additive; wherein the additive includes a sulfur-containing additive, the sulfur-containing additive having the following structural formula:

[0006]

[0007] Where n is an integer selected from 3 to 6;

[0008] R 1 R 2 Each group is independently selected from any one of the following groups: alkyl, alkenyl, ynyl, aryl; and R 1 and / or R 2 It contains one or two elements selected from the following group: N, O.

[0009] According to the technical solution of this application, by applying the sulfur-containing additive to the electrolyte of a lithium-ion battery, it is possible to achieve efficient film formation and reduce the amount of H+ in the electrolyte. + The corrosion effect on the positive and negative electrode materials and the SEI film is beneficial to improving the performance of the battery.

[0010] In some implementations, R 1 R 2 Each is independently selected from any one of the following groups, either unsubstituted or substituted: C 1～6 Alkyl, C 1～6 alkenyl, C 1～6 alkynyl, aryl; and R 1 and / or R 2 It contains one or two elements selected from the following group: N, O.

[0011] In some implementations, the R 1 and the R 2 Each group is independently selected from one of the following groups:

[0012]

[0013] Wherein, # indicates (S) n Connected keys.

[0014] In some embodiments, the sulfur-containing additive comprises one or more combinations selected from the group consisting of:

[0015]

[0016] Where n is an integer selected from 3 to 6.

[0017] In some embodiments, the sulfur-containing additive in the lithium-ion battery electrolyte accounts for 0.01% to 10% by mass.

[0018] In some embodiments, the additive also includes lithium nitrate.

[0019] According to the technical solution of this application, by simultaneously adding the sulfur-containing additive and lithium nitrate (LiNO3) as additives to the electrolyte, a bifunctional composite additive electrolyte is formed. This not only improves the SEI film formation performance on the negative electrode surface, but also, because the added LiNO3 contains lithium ions, it can play a certain role in lithium replenishment, which helps to improve the first-cycle efficiency of the battery.

[0020] In some embodiments, the additive comprises lithium nitrate, wherein the mass ratio of lithium nitrate to the sulfur-containing additive is 1–99:1–99.

[0021] In some embodiments, the additive also includes vinylene carbonate.

[0022] According to the technical solution of this application, by simultaneously adding the sulfur-containing additive and vinylene carbonate to the electrolyte, it is not only beneficial to form an inorganic membrane, but also to increase the organic components in the SEI membrane; by forming an organic-inorganic composite SEI, the toughness of the SEI membrane and its ionic conductivity are further enhanced.

[0023] In some embodiments, the additive comprises vinylene carbonate, wherein the mass ratio of vinylene carbonate to the sulfur-containing additive is 1–99:1–99.

[0024] In some embodiments, the solvent is a carbonate solvent.

[0025] In some embodiments, the solvent includes one or more combinations selected from the group consisting of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and fluoroethylene carbonate.

[0026] In some embodiments, the lithium salt is selected from one or more combinations of the following group: lithium hexafluorophosphate, lithium perchlorate, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonyl, and lithium tetrafluoroborate.

[0027] In some embodiments, the concentration of the lithium salt in the lithium-ion battery electrolyte is 0.1M to 20M, calculated as lithium ions.

[0028] A second aspect of this application provides a lithium-ion battery comprising a positive electrode, a negative electrode, an electrolyte, and a separator located between the positive and negative electrodes; the electrolyte is the lithium-ion battery electrolyte described in the first aspect of this application.

[0029] A third aspect of this application provides a battery module comprising the lithium-ion battery described in the second aspect of this application.

[0030] A fourth aspect of this application provides a battery pack that includes the battery module described in the third aspect of this application.

[0031] A fifth aspect of this application provides an electrical device comprising at least one of the lithium-ion battery described in the second aspect of this application, the battery module described in the third aspect of this application, or the battery pack described in the fourth aspect of this application.

[0032] Compared with the prior art, the technical solution of this application has at least the following beneficial effects:

[0033] This application provides a lithium-ion battery electrolyte comprising a sulfur-containing additive as shown in Formula I. By applying this sulfur-containing additive, a dense and stable SEI film can be formed during the formation stage, exhibiting advantages such as rapid film formation and high film formation efficiency, thereby effectively improving battery performance. On one hand, the -SSS- bonds in the sulfur-containing additive are easily reduced on the negative electrode surface, forming a Li2S negative electrode protective layer. Li2S has excellent lithium-ion conductivity, thus promoting the formation of fast lithium-ion channels in the SEI film. On the other hand, because the N- or O-atom-containing groups in the sulfur-containing additive possess lone pairs of electrons, they can react with H atoms in the electrolyte. + Ion binding, thereby reducing H + Corrosion effect on positive and negative electrode materials and SEI film. Attached Figure Description

[0034] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0035] Figure 1 This is a schematic diagram of a lithium-ion battery according to one embodiment of this application;

[0036] Figure 2 yes Figure 1 An exploded view of a lithium-ion battery according to an embodiment of this application is shown.

[0037] Figure 3 This is a schematic diagram of a battery module according to one embodiment of this application;

[0038] Figure 4 This is a schematic diagram of a battery pack according to one embodiment of this application;

[0039] Figure 5 yes Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown;

[0040] Figure 6 This is a schematic diagram of an electrical device using a lithium-ion battery as a power source according to an embodiment of this application.

[0041] Explanation of reference numerals in the attached figures:

[0042] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Lithium-ion battery; 51 Housing; 52 Electrode assembly; 53 Top cover assembly. Detailed Implementation

[0043] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0044] 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 the particular range. Ranges defined in this way include endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range.

[0045] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0046] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0047] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially.

[0048] In existing technologies, improvements can be made to the film-forming additives in the electrolyte to enhance battery performance. These additives mainly include boron-containing additives, organophosphorus additives, carbonate additives, sulfur-containing additives, and ionic liquid additives. However, existing film-forming additives often suffer from drawbacks such as slow film formation, difficulty in forming a dense SEI film, and low film formation efficiency.

[0049] To address the aforementioned problems, this application proposes the following technical solutions and specific implementation methods.

[0050] A lithium-ion battery electrolyte comprising a solvent, a lithium salt, and additives; wherein the additives include a sulfur-containing additive, the structural formula of which is shown in Formula I.

[0051]

[0052] Where n is an integer selected from 3 to 6;

[0053] R 1 R 2Each group is independently selected from any one of the following groups: alkyl, alkenyl, ynyl, aryl; and R 1 and / or R 2 It contains one or two elements selected from the following group: N, O.

[0054] By applying the sulfur-containing additive to the electrolyte of a lithium-ion battery, efficient film formation can be achieved, thereby improving battery performance. During the formation stage, the -SSS- bonds in the sulfur-containing additive are easily reduced on the negative electrode surface, forming a Li2S negative electrode protective layer. Li2S has excellent lithium-ion conductivity, thus promoting the formation of fast lithium-ion channels in the SEI film. In contrast, existing sulfur-containing additives typically contain monosulfide or disulfide bonds, which, even when reduced, cannot break the CS bonds, thus failing to form a Li2S protective layer. Furthermore, groups containing N or O atoms possess lone pairs of electrons, which can interact with H atoms in the electrolyte. + Ion binding, thereby reducing H + Corrosion effect on positive and negative electrode materials and SEI film.

[0055] In some implementations, n is selected from 3, 4, 5, or 6.

[0056] In some implementations, the R 1 and the R 2 Each group is independently selected from one of the following groups:

[0057]

[0058] Wherein, # indicates (S) n Connected keys.

[0059] In some embodiments, the sulfur-containing additive comprises one or more combinations selected from the group consisting of:

[0060]

[0061] Where n is an integer from 3 to 6; for example, n can be selected from 3, 4, 5 or 6.

[0062] In some embodiments, the sulfur-containing additive comprises one or more combinations selected from the group consisting of:

[0063]

[0064]

[0065] In some embodiments, the sulfur-containing additive comprises a combination of the following:

[0066]

[0067] In some embodiments, the sulfur-containing additive comprises a combination of compounds shown in Formula I-4, Formula I-5, Formula I-6, and Formula I-7; the sulfur-containing additive is prepared by the following method: dithiodipyridine and elemental sulfur are added to an appropriate amount of DME solution at a molar ratio of 1-1.2:2-2.2, heated and stirred at 70-75°C for 4.5-5.5 h, and the solvent is dried under vacuum to obtain a mixed material comprising compounds shown in Formula I-4, Formula I-5, Formula I-6, and Formula I-7 (prepared according to the method described in Adv. Sci. 2020, 7, 1902646), which is the sulfur-containing additive.

[0068] In one embodiment, the sulfur-containing additive comprises a combination of compounds shown in Formula I-4, Formula I-5, Formula I-6, and Formula I-7; the sulfur-containing additive is prepared by the following method: disulfide dipyridine and elemental sulfur are added to an appropriate amount of DME solution at a molar ratio of 1:2, heated and stirred at 70°C for 5 hours, and the solvent is removed under vacuum to obtain a mixed material comprising compounds shown in Formula I-4, Formula I-5, Formula I-6, and Formula I-7 (prepared according to the method described in the literature Adv. Sci. 2020, 7, 1902646), which is the sulfur-containing additive.

[0069] In some embodiments, the sulfur-containing additive includes compounds represented by formulas I-8, namely bis(pentamethylene)thiuram tetrasulfide.

[0070]

[0071] In some embodiments, the sulfur-containing additive comprises a combination of the following:

[0072]

[0073] In some embodiments, the sulfur-containing additive comprises a combination of compounds shown in Formula I-9, Formula I-10, Formula I-11, and Formula I-12, and is prepared by the following method: adding ethanol to a DME solution to obtain a 0.2M ethanol solution; adding excess lithium metal to the solution to form 0.2M lithium ethanol; adding 2 mmol CS2 to 1 ml of the solution and stirring continuously for 1 h, followed by adding 2 mmol elemental sulfur and stirring overnight; removing the solvent to obtain a mixture of compounds shown in Formula I-9, Formula I-10, Formula I-11, and Formula I-12, which is the sulfur-containing additive.

[0074] In some embodiments, the sulfur-containing additive in the lithium-ion battery electrolyte has a mass percentage of 0.01% to 10%; for example, the mass percentage of the sulfur-containing additive can be selected from 0.01%, 0.1%, 0.2%, 0.5%, 0.7%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, etc.

[0075] When the amount of sulfur-containing additive is less than 0.01%, the additive cannot form a uniform film on the negative electrode surface, resulting in an unsatisfactory film formation effect and poor battery cycle performance. When the amount of sulfur-containing additive is greater than 10%, the additive cannot be completely consumed during the first formation process, causing the sulfur-containing additive to participate in oxidation at the positive electrode during subsequent charging, thereby shuttling between the positive and negative electrodes and generating a "shuttle effect", which reduces the battery coulombic efficiency.

[0076] In some embodiments, the additive also includes lithium nitrate.

[0077] By simultaneously adding the sulfur-containing additive and lithium nitrate (LiNO3) to the electrolyte, a bifunctional composite additive electrolyte is formed. This not only improves the SEI film formation performance on the negative electrode surface, but also, because the added LiNO3 contains lithium ions, it can play a certain role in lithium replenishment, which helps to improve the battery's first-cycle efficiency.

[0078] In some embodiments, the additive comprises lithium nitrate, and the mass ratio of lithium nitrate to the sulfur-containing additive is 1-99:1-99; for example, if the mass ratio of lithium nitrate to the sulfur-containing additive is a:b, then a and b can each be independently selected from 1, 2, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 99, etc.

[0079] In some embodiments, the additive also includes vinylene carbonate.

[0080] By simultaneously adding the sulfur-containing additive and vinylene carbonate to the electrolyte, the organic components in the SEI film can be increased. By forming an organic-inorganic composite SEI, the toughness and ionic conductivity of the SEI film are further enhanced.

[0081] In some embodiments, the additive comprises vinylene carbonate, and the mass ratio of vinylene carbonate to the sulfur-containing additive is 1-99:1-99; for example, if the mass ratio of vinylene carbonate to the sulfur-containing additive is c:d, then c and d can each be independently selected from 1, 2, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 99, etc.

[0082] In some embodiments, the solvent is a carbonate solvent.

[0083] By using carbonate solvents, polysulfides that do not participate in film formation can be consumed to a certain extent, thereby reducing their risk of oxidation at the positive electrode.

[0084] In some embodiments, the solvent includes one or more combinations selected from the group consisting of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and fluoroethylene carbonate.

[0085] In some embodiments, the lithium salt is selected from one or more combinations of the following group: lithium hexafluorophosphate, lithium perchlorate, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonyl, and lithium tetrafluoroborate.

[0086] In some embodiments, the concentration of the lithium salt in the lithium-ion battery electrolyte is 0.1M to 20M in terms of lithium ions; for example, the concentration of the lithium salt in terms of lithium ions can be selected from 0.1M, 0.5M, 1M, 2M, 3M, 4M, 5M, 6M, 7M, 8M, 9M, 10M, 11M, 12M, 13M, 14M, 15M, 16M, 17M, 18M, 19M, 20M, etc.

[0087] When the concentration of the lithium salt, expressed as lithium ions, is less than 0.1 M, the ionic conductivity of the electrolyte decreases significantly, leading to a larger battery capacity.

[0088] In some embodiments, a method for preparing the lithium-ion electrolyte is provided, which includes mixing the solvent, lithium salt and additives in a certain proportion to obtain the lithium-ion electrolyte.

[0089] In some embodiments, a lithium-ion battery is provided, which includes a positive electrode, a negative electrode, an electrolyte, and a separator between the positive electrode and the negative electrode; the electrolyte is the lithium-ion battery electrolyte provided in this application.

[0090] [Positive electrode plate]

[0091] The positive electrode sheet includes a positive current collector and a positive electrode material disposed on at least one surface of the positive current collector, wherein the positive electrode material includes a positive active material.

[0092] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0093] In some embodiments, the positive electrode active material may be a known positive electrode active material for lithium-ion batteries. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0094] In some embodiments, the positive electrode material may optionally include a binder. For example, the binder may include one or more combinations selected from the group consisting of: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0095] In some embodiments, the cathode material may optionally include a conductive agent. For example, the conductive agent may include one or more combinations selected from the group consisting of: Super P, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0096] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned positive electrode material, such as positive electrode active material, conductive agent, binder and any other components in a solvent (e.g. N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0097] [Negative electrode plate]

[0098] The negative electrode sheet includes a negative current collector and a negative electrode material disposed on at least one surface of the negative current collector, wherein the negative electrode material includes a negative electrode active material.

[0099] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0100] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in lithium-ion batteries. For example, the negative electrode active material includes one or more combinations selected from the group consisting of: natural graphite, artificial graphite, mesophase microcarbon spheres (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composites, Li-Sn alloys, Li-Sn-O alloys, Sn, SnO, SnO2, TiO2-Li4Ti5O 12 Li-Al alloy.

[0101] In some embodiments, the negative electrode material may also optionally include a binder. For example, the binder may include one or more combinations selected from the group consisting of: styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0102] In some embodiments, the negative electrode material may optionally include a conductive agent. For example, the conductive agent may include one or more combinations selected from the group consisting of: Super P, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0103] In some embodiments, the negative electrode material may also optionally include other additives. For example, other additives may be thickeners (such as sodium carboxymethyl cellulose (CMC-Na)).

[0104] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned negative electrode material, such as negative electrode active material, conductive agent, binder and any other components in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0105] Electrolyte

[0106] The lithium-ion battery electrolyte described in this application is used.

[0107] [Isolation membrane]

[0108] This application does not impose any particular restriction on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected. For example, the material of the separator membrane can be selected from one or more combinations of the following: glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator membrane can be a single-layer film or a multi-layer composite film, without particular restriction. When the separator membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular restriction.

[0109] [Preparation of Lithium-ion Batteries]

[0110] A lithium-ion battery can be prepared by winding or stacking positive electrode sheets, negative electrode sheets, and separators to form an electrode assembly, which is then packaged and injected with electrolyte.

[0111] The outer packaging can be a hard shell, such as a hard plastic shell, aluminum shell, or steel shell. It can also be a flexible package, such as a pouch. The material of the flexible package can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0112] This application does not impose any particular limitation on the shape of the lithium-ion battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 This is an example of a square-structured lithium-ion battery 5.

[0113] In some implementations, refer to Figure 2 The outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be placed over the opening to close the receiving cavity. Positive electrode sheets, negative electrode sheets, and a separator can be formed into an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. The electrolyte is immersed in the electrode assembly 52. ​​The lithium-ion battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0114] In some implementations, lithium-ion batteries can be assembled into battery modules, and the number of lithium-ion batteries contained in a battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0115] Figure 3 This is battery module 4, used as an example. (See reference...) Figure 3 In battery module 4, multiple lithium-ion batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, the multiple lithium-ion batteries 5 can be fixed in place using fasteners.

[0116] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple lithium-ion batteries 5 are housed.

[0117] In some embodiments, the battery module 4 described above can also be assembled into a battery pack. The number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0118] Figure 4 and Figure 5 This is battery pack 1 as an example. (See reference...) Figure 4 and Figure 5 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0119] In addition, this application also provides an electrical device, which includes the lithium-ion battery provided in this application. In some embodiments, the electrical device includes at least one of the battery modules or battery packs provided in this application. The lithium-ion battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include 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., but is not limited thereto.

[0120] As the electrical device, a lithium-ion battery, battery module, or battery pack can be selected according to its usage requirements.

[0121] Figure 6 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of lithium-ion batteries for this device, a battery pack or battery module can be used.

[0122] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use lithium-ion batteries as their power source.

[0123] Example 1

[0124] (1) Preparation of positive electrode sheet

[0125] A positive electrode slurry was prepared by mixing lithium iron phosphate (LiFePO4) as the positive electrode active material, Super P as the conductive agent, and polyvinylidene fluoride (PVDF) as the binder in N-methylpyrrolidone (NMP). The solid content of the positive electrode slurry was 50 wt%, and the mass ratio of LiFePO4, Super P, and PVDF in the solid components was 95:3:2. The positive electrode slurry was coated onto a current collector aluminum foil, dried at 85°C, and then cold-pressed. Afterward, the foil was trimmed, cut into sheets, and dried under vacuum at 85°C for 4 hours to form the positive electrode sheet.

[0126] (2) Preparation of negative electrode sheet

[0127] The negative electrode active material graphite, conductive agent Super P, binder styrene-butadiene rubber (SBR), and thickener CMC-Na were dispersed in deionized water at a mass ratio of 94:3:1.5:1.5 and mixed evenly to obtain a negative electrode slurry. The solid content of the negative electrode slurry was 30 wt%. The negative electrode slurry was coated onto a negative electrode current collector copper foil and dried at 85°C. Then, it was cold-pressed, trimmed, and cut into sheets. Finally, it was dried under vacuum at 120°C for 12 hours to produce a negative electrode sheet.

[0128] 3) Separating membrane

[0129] A 16μm polyethylene film was selected as the separator.

[0130] 4) Preparation of electrolyte

[0131] The electrolyte mother liquor is a 1M lithium hexafluorophosphate EC / DMC (1:1 vol%) solution; 0.5 wt% of additive 1 is added to it and stirred until completely dissolved to obtain an electrolyte containing a novel functional additive. Additive 1 comprises a combination of compounds shown in Formulas I-4, I-5, I-6, and I-7. Additive 1 is prepared by the following method: disulfide dipyridine and elemental sulfur are added to an appropriate amount of DME solution at a molar ratio of 1:2, heated and stirred at 70°C for 5 hours, and the solvent is removed under vacuum to obtain a mixture of compounds shown in Formulas I-4, I-5, I-6, and I-7, which is the sulfur-containing additive.

[0132] 5) Battery manufacturing

[0133] The positive electrode sheet, separator, and negative electrode sheet prepared in the above steps are stacked in sequence, with the separator positioned between the positive and negative electrodes to isolate them. The resulting bare cell is wound, tabs are welded on, and the bare cell is placed in outer packaging. The electrolyte prepared above is injected into the dried cell at an injection rate of 4 g / Ah. After encapsulation and settling, slow formation occurs, followed by shaping to obtain lithium-ion battery III-1.

[0134] Example 2

[0135] Except for the following differences, the lithium-ion battery III-2 was prepared by the same preparation method as in Example 1.

[0136] In the preparation of the electrolyte, the concentration of additive 1 is 1.0 wt%.

[0137] Example 3

[0138] Except for the following differences, the lithium-ion battery III-3 was prepared by the same preparation method as in Example 1.

[0139] In the preparation of the electrolyte, the concentration of additive 1 is 5.0 wt%.

[0140] Example 4

[0141] Except for the following differences, the lithium-ion battery III-4 was prepared by the same preparation method as in Example 1.

[0142] In the preparation of the electrolyte, compound I-8 is used as additive 2, and additive 2 replaces additive 1.

[0143] Example 5

[0144] Except for the following differences, the lithium-ion battery III-5 was prepared by the same preparation method as in Example 1.

[0145] In the preparation of the electrolyte, compound I-8 is used as additive 2, which replaces additive 1, and the concentration of additive 2 is 1.0 wt%.

[0146] Example 6

[0147] Except for the following differences, the lithium-ion battery III-6 was prepared by the same preparation method as in Example 1.

[0148] In the preparation of the electrolyte, compound I-8 is used as additive 2, which replaces additive 1, and the concentration of additive 2 is 5.0 wt%.

[0149] Example 7

[0150] Except for the following differences, the lithium-ion battery III-7 was prepared by the same preparation method as in Example 1.

[0151] In the preparation of the electrolyte, the concentration of additive 1 is 1.0 wt%; and it also includes additive LiNO3, with a mass ratio of LiNO3 to additive 1 of 2:1.

[0152] Example 8

[0153] Except for the following differences, the lithium-ion battery III-8 was prepared by the same preparation method as in Example 1.

[0154] In the preparation of the electrolyte, compound I-8 is used as additive 2, which replaces additive 1, and the concentration of additive 2 is 1.0 wt%; it also includes additive LiNO3, and the mass ratio of LiNO3 to additive 2 is 2:1.

[0155] Example 9

[0156] Except for the following differences, the lithium-ion battery III-9 was prepared by the same preparation method as in Example 1.

[0157] In the preparation of the electrolyte, the concentration of additive 1 is 1.0 wt%; and it also includes the additive vinylene carbonate, with a mass ratio of vinylene carbonate to additive 1 of 2:1.

[0158] Example 10

[0159] Except for the following differences, the lithium-ion battery III-10 was prepared by the same preparation method as in Example 1.

[0160] In the preparation of the electrolyte, Formula I-8 is used as additive 2, additive 2 replaces additive 1, and the concentration of additive 2 is 1.0 wt%; it also includes additive vinylene carbonate, and the mass ratio of vinylene carbonate to additive 2 is 2:1.

[0161] Example 11

[0162] Except for the following differences, the lithium-ion battery III-11 was prepared by the same preparation method as in Example 1.

[0163] In the preparation of the electrolyte, the concentration of additive 1 is 1.0 wt%; and it also includes additives LiNO3 and vinylene carbonate, with the mass ratio of LiNO3, vinylene carbonate and additive 1 being 2:2:1.

[0164] Example 12

[0165] Except for the following differences, the lithium-ion battery III-12 was prepared by the same preparation method as in Example 1.

[0166] In the preparation of the electrolyte, compound I-8 is used as additive 2, which replaces additive 1, and the concentration of additive 2 is 1.0 wt%. It also includes additives LiNO3 and vinylene carbonate, and the mass ratio of LiNO3, vinylene carbonate and additive 2 is 2:2:1.

[0167] Comparative Example 1

[0168] Except for the following differences, the lithium-ion battery IV-1 was prepared by the same preparation method as in Example 1.

[0169] In the preparation of the electrolyte, diphenyl trisulfide is used instead of additive 1, and the concentration of diphenyl trisulfide is 1.0 wt%.

[0170] Comparative Example 2

[0171] Except for the following differences, the lithium-ion battery IV-2 was prepared by the same preparation method as in Example 1.

[0172] Additive 1 is not added during the preparation of the electrolyte.

[0173] Experimental Example

[0174] The performance of the lithium-ion batteries prepared in Examples 1-12 and Comparative Examples 1-2 was tested, and the specific steps are as follows:

[0175] The lithium-ion battery was subjected to constant current charge-discharge testing. The specific cycle procedure was as follows: at 25℃, the charge-discharge voltage range was 2.5V to 3.65V, and the charge-discharge current was 0.5C. One charge and one discharge constituted one cycle (1 revolution). The capacity C0 and charge capacity C of the individual battery cells after the first cycle were recorded, and the capacity C1 of the coin cell after the 100th cycle was recorded. C0 / C×100% was calculated as the initial coulombic efficiency of the battery, and C1 / C0×100% was calculated as the capacity retention rate of the battery after 100 cycles. The test results are shown in Table 1.

[0176] Table 1 Results of the initial coulombic efficiency and capacity retention tests

[0177]

[0178]

[0179] As shown in Table 1, compared to not using additives (Comparative Example 2) or using other types of sulfur-containing additives (Comparative Example 1), the addition of the sulfur-containing additive provided in this application significantly improves the battery's cycle performance. Furthermore, the simultaneous addition of the sulfur-containing additive provided in this application and LiNO3 further improves the battery's initial efficiency and coulombic efficiency; the simultaneous addition of the sulfur-containing additive provided in this application and vinylene carbonate further enhances the battery's cycle performance; the most significant improvement in cycle performance occurs when the electrolyte simultaneously contains the sulfur-containing additive provided in this application, LiNO3, and vinylene carbonate.

[0180] The above description is merely a preferred embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A lithium-ion battery electrolyte, wherein the lithium-ion battery electrolyte comprises a solvent, a lithium salt, and additives, characterized in that, The additive includes a sulfur-containing additive, the structural formula of which is: ； Where n is an integer selected from 3 to 6; The R 1 and the R 2 for: ； Wherein, # indicates (S) n Connected keys; The additives also include lithium nitrate and vinylene carbonate.

2. The lithium-ion battery electrolyte as described in claim 1, characterized in that, In the lithium-ion battery electrolyte, the sulfur-containing additive accounts for 0.01% to 10% of the total mass.

3. The lithium-ion battery electrolyte as described in claim 1, characterized in that, The mass ratio of lithium nitrate to the sulfur-containing additive is 1~99:1~99; The mass ratio of the vinylene carbonate to the sulfur-containing additive is 1~99:1~99.

4. The lithium-ion battery electrolyte as described in claim 1, characterized in that, The solvent is a carbonate solvent.

5. The lithium-ion battery electrolyte as described in claim 4, characterized in that, The solvent includes one or more combinations selected from the group consisting of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and fluoroethylene carbonate.

6. The lithium-ion battery electrolyte as described in claim 1, characterized in that, The lithium salt is selected from one or more combinations of the following group: lithium hexafluorophosphate, lithium perchlorate, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonyl, and lithium tetrafluoroborate.

7. The lithium-ion battery electrolyte as described in claim 1, characterized in that, In the lithium-ion battery electrolyte, the concentration of the lithium salt, calculated as lithium ions, is 0.5M to 5M.

8. A lithium-ion battery comprising a positive electrode, a negative electrode, an electrolyte, and a separator located between the positive and negative electrodes, characterized in that, The electrolyte is the lithium-ion battery electrolyte according to any one of claims 1 to 7.

9. A battery module comprising the lithium-ion battery of claim 8.

10. A battery pack comprising the battery module of claim 9.

11. An electrical device comprising at least one of the lithium-ion battery of claim 8, the battery module of claim 9, or the battery pack of claim 10.

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