A negative electrode slurry, a negative electrode sheet, a battery cell, a battery, and an electrical device.

Abstract

This invention discloses a negative electrode slurry, a negative electrode sheet, a battery cell, a battery, and electrical equipment. The negative electrode slurry includes a negative electrode active material, a conductive agent, a binder, and a sulfur-containing additive. The technical solution of this invention involves adding a sulfur-containing additive to the negative electrode slurry. This sulfur-containing additive continuously decomposes at the negative electrode to form elemental sulfur, which then undergoes a reduction reaction on the negative electrode surface to transform into polysulfides. The polysulfides initiate ring-opening polymerization of cyclic carbonates, forming an elastic SEI film in situ. Because this invention uses an in-situ addition of sulfur-containing additives to the negative electrode, the efficiency of SEI film formation is higher, and the amount added is less. Furthermore, the use of sulfur-containing additives significantly reduces the generation of gaseous compounds, thereby further reducing electrode material delamination and battery expansion.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and in particular to a negative electrode slurry, a negative electrode sheet, a battery cell, a battery, and an electrical device. Background Technology

[0002] In related technologies, in order to improve the quality of the negative electrode SEI film (solid electrolyte interface film) of lithium-ion batteries during cyclic charging and discharging, carbonate electrolyte additives are used. However, these additives may cause severe delamination of electrode materials and battery swelling. Summary of the Invention

[0003] The main objective of this invention is to provide a negative electrode slurry that aims to alleviate the problems of electrode material delamination and battery expansion caused by the addition of additives to the existing lithium-ion battery negative electrode SEI film.

[0004] To achieve the above objectives, the present invention proposes a negative electrode slurry, which includes a negative electrode active material, a conductive agent, a binder, and a sulfur-containing additive.

[0005] In the technical solution of this invention, a sulfur-containing additive is added to the negative electrode slurry. This sulfur-containing additive continuously decomposes at the negative electrode to form elemental sulfur, which then undergoes a reduction reaction on the negative electrode surface during charging, transforming into polysulfides. The polysulfides initiate ring-opening polymerization of cyclic carbonates, forming an elastic SEI film in situ. Because this invention uses a sulfur-containing additive added in situ to the negative electrode slurry, the efficiency of SEI film formation is higher, and the amount added is less. Furthermore, the use of a sulfur-containing additive significantly reduces the generation of gaseous compounds, thereby further reducing electrode material delamination and battery expansion.

[0006] In some embodiments of the present invention, the sulfur-containing additive includes at least one of polymeric sulfur, a composition of polymeric sulfur and elemental sulfur, organic polysulfides, metal polysulfides, sulfur-containing organic polymers, and copolymers of polymeric sulfur and carbon materials.

[0007] In the technical solution of this invention, the sulfur-containing additives added to lithium-ion batteries can be one or more. Organic polysulfides refer to organic compounds containing polysulfide ions. In some embodiments, organic polysulfides have the general structural formula R-Sn-R, where R is an aliphatic or aromatic group, n is the number of SS bonds, and n is a natural number greater than 0. Metal polysulfides refer to transition metal complexes containing polysulfide ions. In some embodiments, metal polysulfides have the general structural formula R-Sn-R, where R is a group containing metal atoms, n is the number of SS bonds, and n is a natural number greater than 0. Sulfur-containing organic polymers refer to polymers whose main chain or branches contain sulfur atoms. In some embodiments, the sulfur-containing organic polymers of this invention contain SS bonds, and the sulfur loading is >5%. Copolymers of polymeric sulfur and carbon materials refer to copolymers of polymeric sulfur and carbon materials, where the carbon materials may include graphene, carbon nanotubes, etc. All of the above-mentioned sulfur-containing additives can release elemental sulfur during the electrode reaction process, and the elemental sulfur can form polysulfides to initiate the ring-opening polymerization of cyclic carbonates, or directly initiate the ring-opening polymerization of cyclic carbonates by polysulfides, thereby forming an elastic SEI film in situ during the cyclic charging and discharging of lithium-ion batteries.

[0008] In some embodiments of the present invention, the insoluble sulfur content in the sulfur-containing additive needs to reach more than 30% of the total sulfur element percentage, and preferably, the insoluble sulfur content in the sulfur-containing additive accounts for more than 70% of the total sulfur element percentage.

[0009] In the technical solution of this invention, when the insoluble sulfur content in the sulfur-containing additive accounts for more than 30% of the total sulfur element, it is more suitable for the formation of the SEI film than when the insoluble sulfur content accounts for less than 30% of the total sulfur element. Preferably, when the insoluble sulfur content in the sulfur-containing additive accounts for more than 70% of the total sulfur element, the rate of depolymerization of the sulfur-containing additive to generate elemental sulfur is more suitable for the formation of the SEI film than when the insoluble sulfur content in the sulfur-containing additive accounts for more than 30% of the total sulfur element, thereby forming an elastic SEI film in situ during more cycles of lithium-ion battery charging and discharging.

[0010] In some embodiments of the present invention, the molecular weight of the polymeric sulfur is 0.1 million to 300,000, preferably 10,000 to 50,000.

[0011] In the technical solution of this invention, when the molecular weight of the polymerized sulfur is between 0.1 million and 300,000, an elastic SEI film can be formed in situ during a suitable number of lithium-ion battery charge-discharge cycles. Furthermore, the stability of elemental sulfur release can be optimized by selecting polymerized sulfur with a suitable molecular weight. When the molecular weight of the polymerized sulfur is between 10,000 and 50,000, the stability of elemental sulfur release can be further optimized, thereby enabling the formation of an elastic SEI film in situ during an even greater number of lithium-ion battery charge-discharge cycles.

[0012] In some embodiments of the present invention, the organic polysulfide includes at least one of diisopropyltrisulfide, bis-[γ-(triethoxysilyl)propyl]-tetrasulfide, and tert-dodecyl polysulfide; the metal polysulfide includes at least one of molybdenum disulfide, lithium sulfide, and titanium sulfide; and the sulfur-containing organic polymer includes at least one of poly(o-thiocarbamate) and polysulfide rubber.

[0013] In this invention, organic polysulfides and metal polysulfides can directly initiate the ring-opening polymerization of cyclic carbonates and form an elastic SEI film in situ during the cyclic charging and discharging of lithium-ion batteries. Sulfur-containing organic polymers can release elemental sulfur, which, through the formation of polysulfides during the cyclic charging and discharging reaction, initiates the ring-opening polymerization of cyclic carbonates and forms an elastic SEI film in situ during the cyclic charging and discharging of lithium-ion batteries.

[0014] In some embodiments of the present invention, the sulfur-containing additive further includes a stabilizer, which includes at least one of elemental sulfur, halogens, halides, thiazole compounds, iodonitrobenzene, and alkali metal compounds.

[0015] In the technical solution of this invention, the stabilizer works by acting as a capping group to reduce the probability of free radicals formed by the loss of electrons at both ends of the sulfur-containing additive, delaying the time for free radicals to form by the loss of electrons at both ends of the sulfur-containing additive, and making the rate of release of elemental sulfur from polymerized sulfur more stable, or increasing the concentration of elemental sulfur, so that the decomposition reaction is slowed down due to the increase in the concentration of elemental sulfur.

[0016] In some embodiments of the present invention, the weight percentage of the stabilizer relative to the weight percentage of the sulfur-containing additive is 0.1%-10%, preferably 1%-5%.

[0017] In this invention, when the weight of the stabilizer is between 0.1% and 10%, the release rate of the sulfur-containing additive can be controlled within a suitable range, resulting in a more stable, reliable, and higher-quality SEI film formed by the lithium-ion battery during a suitable number of charge-discharge cycles. When the weight of the stabilizer is between 1% and 5%, the release rate of the sulfur-containing additive can be controlled within an even more suitable range, resulting in a more stable, reliable, and higher-quality SEI film formed by the lithium-ion battery during an even greater number of charge-discharge cycles.

[0018] In some embodiments of the present invention, the polymeric sulfur is end-capped polymeric sulfur with the molecular formula MSS. (8n-2) -SM, where n is a natural number greater than 0, and M includes at least one of halogens, halides, thiazole compounds, iodonitrobenzene, and alkali metal compounds.

[0019] In the technical solution of the present invention, since it is necessary for the polymerized sulfur to release elemental sulfur more stably, the stabilizer used for end capping includes at least one of halogens, halides, thiazole compounds, iodonitrobenzene, and alkali metal compounds. In addition, olefin stabilizers, including but not limited to olefinic stabilizers such as benzocyclopropene and isoprene, can also be used to end cap the polymerized sulfur.

[0020] In some embodiments of the present invention, the sulfur-containing organic polymer includes a polymeric sulfur-polythiophene copolymer, a polymeric sulfur-polypyrrole copolymer, and a polymeric sulfur-polyaniline copolymer, and the copolymer of polymeric sulfur with carbon materials includes a polymeric sulfur-carbon nanotube graft copolymer and / or a polymeric sulfur-graphene copolymer.

[0021] In the technical solution of this invention, the sulfur-containing organic polymer can be a block copolymer, a graft copolymer, or a combination of block copolymers and graft copolymers. Because the sulfur-containing additive possesses polymeric sulfur blocks and branches, it can slowly release polymeric sulfur, promoting the formation of a high-quality SEI film.

[0022] In some embodiments of the present invention, the electrical conductivity of the sulfur-containing additive is 10 to 100 S / cm.

[0023] In the technical solution of this invention, the conductivity of the sulfur-containing additive is 10 to 100 S / cm, which meets the conductivity requirements of this technical solution.

[0024] In some embodiments of the present invention, the molecular weight of the sulfur-containing additive is 0.2 million to 500,000, preferably, the molecular weight of the sulfur-containing additive is 10,000 to 50,000.

[0025] In this invention, when the molecular weight of the sulfur-containing additive is between 0.2 million and 500,000, its conductivity is suitable, and the slow release rate of elemental sulfur is optimized, making the SEI film generated by the lithium-ion battery more stable, reliable, and of better quality during long-term charge-discharge cycles. Preferably, when the molecular weight of the sulfur-containing additive is between 10,000 and 50,000, its conductivity is even more suitable, and the slow release rate of elemental sulfur is further optimized, making the SEI film generated by the lithium-ion battery more stable, reliable, and of better quality during more cycles of charge-discharge.

[0026] In some embodiments of the present invention, the negative electrode active material is 80-99 parts, the conductive agent is 0.2-10 parts, the binder is 1-10 parts, and the sulfur-containing additive is 0.5-5 parts.

[0027] In this invention, when the negative electrode active material is 80-90 parts, the increase in reduction potential during the reaction process can be reduced while ensuring a suitable lithium-ion capacity. When the conductive agent is 0.2-10 parts, the decrease in battery density and capacity can be reduced while ensuring a suitable conductivity. When the binder is 1-10 parts, the problem of excessive density in lithium-ion batteries containing binders during processing can be reduced while ensuring a suitable bonding effect. When the sulfur-containing additive is 0.5-5 parts, an elastic SEI film can be formed in situ during a suitable number of lithium-ion battery charge-discharge cycles, and the release stability of elemental sulfur can be improved. The negative electrode slurry may also include other additives, such as dispersants.

[0028] The present invention also provides a negative electrode sheet, comprising the negative electrode slurry described in the above technical solution.

[0029] The present invention also provides a battery cell, including the negative electrode sheet described in the above technical solution.

[0030] The present invention also provides a battery comprising the battery cell described in the above technical solution.

[0031] The present invention also provides an electrical device, including the battery described in the above technical solution.

[0032] This invention employs a method of adding a sulfur-containing additive to the negative electrode slurry. This additive continuously decomposes at the negative electrode to form elemental sulfur, which then undergoes a reduction reaction on the negative electrode surface, transforming into polysulfides. These polysulfides initiate ring-opening polymerization of cyclic carbonates, forming an elastic SEI film in situ. Because this invention uses an in-situ addition of the sulfur-containing additive to the negative electrode slurry, the efficiency of SEI film formation is higher, and the amount added is less. Furthermore, the use of a sulfur-containing additive significantly reduces the generation of gaseous compounds, thereby further reducing electrode material delamination and battery expansion. Detailed Implementation

[0033] The following details embodiments of the battery cell, battery module, battery, and electrical device of this application, as well as a method for processing a negative electrode sheet. 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 following description is provided to enable those skilled in the art to fully understand this application and is not intended to limit the subject matter of the claims.

[0034] 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.

[0035] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0036] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0037] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, optionally 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. For example, the method may also include step (c), indicating 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.

[0038] The batteries mentioned in this field include lithium-ion batteries. Lithium-ion batteries are currently widely used in pure electric vehicles and hybrid vehicles.

[0039] Negative electrode slurry includes negative electrode active material, conductive agent, binder and other additives, such as solvent, dispersant, etc.

[0040] The negative electrode active material is a material used to store active lithium in the cyclic charge and discharge reaction of a lithium-ion battery. For example, the negative electrode active material can be artificial graphite or natural graphite.

[0041] Conductive agents are the medium through which electrons are transferred between active materials and current collectors.

[0042] Adhesives are used to bond negative electrode active materials, conductive agents, and other substances that can be bonded to the current collector onto the current collector.

[0043] The negative electrode sheet includes a current collector and a negative electrode paste, with the negative electrode paste coated on the current collector.

[0044] Current collectors are materials that conduct electrons to the external circuit. In lithium-ion batteries, they mainly refer to metal foils or composite metal foils, such as copper foil, aluminum foil, composite copper foil, or composite aluminum foil.

[0045] SEI film refers to a passivation layer formed on the surface of a liquid lithium-ion battery during the initial charge and discharge process, resulting from the reaction between the electrode material and the electrolyte at the solid-liquid interface. This passivation layer is an interface layer, exhibiting characteristics of a solid electrolyte; it is an electronic insulator, yet it is a Li-type passivation layer. + Li is an excellent conductor. + It can freely embed and extract through this passivation layer.

[0046] A single battery cell consists of a positive electrode, a negative electrode, an electrolyte, and a separator. Lithium-ion battery cells primarily function by the movement of lithium ions between the positive and negative electrodes.

[0047] After the secondary battery electrode is coated with slurry, dried and rolled, it forms a multi-layer composite structure of current collector and coating on at least one side of the current collector.

[0048] In related technologies, in order to improve the quality of the SEI film of the negative electrode of lithium-ion batteries during cyclic charging and discharging, carbonate electrolyte additives are added. However, these additives generate a large number of gaseous compounds, such as carbon dioxide, which may cause severe delamination of the electrode material and battery expansion.

[0049] The main objective of this invention is to provide a negative electrode slurry that addresses the problems of electrode material delamination and battery expansion caused by additives used to improve the quality of the SEI film in lithium-ion batteries.

[0050] To achieve the above objectives, the present invention proposes a negative electrode slurry, which includes a negative electrode active material, a conductive agent, a binder, and a sulfur-containing additive.

[0051] In the technical solution of this invention, a sulfur-containing additive is added to the negative electrode slurry. This sulfur-containing additive continuously decomposes to form elemental sulfur, which then undergoes a reduction reaction on the negative electrode surface during charging, transforming into polysulfides. The polysulfides initiate ring-opening polymerization of cyclic carbonates, forming an elastic SEI film in situ. Because this invention uses an in-situ addition of a sulfur-containing additive to the negative electrode slurry, the efficiency of SEI film formation is higher, and the amount added is less. Furthermore, the use of a sulfur-containing additive significantly reduces the generation of gaseous compounds, thereby further reducing electrode material delamination and battery expansion.

[0052] In some embodiments of the present invention, the sulfur-containing additive includes at least one of polymeric sulfur, a composition of polymeric sulfur and elemental sulfur, organic polysulfides, metal polysulfides, sulfur-containing organic polymers, and copolymers of polymeric sulfur and carbon materials.

[0053] In the technical solution of the present invention, the sulfur-containing additives added to the lithium-ion battery can be one or more. During the cyclic charging and discharging process of the lithium-ion battery, the insoluble sulfur needs to be depolymerized by itself or under external catalysis within a sufficient number of charge and discharge cycles, for example, gaining electrons, and gradually releasing elemental sulfur, such as S2, S4, S6, and S8. The release rate needs to meet the specific requirements for the growth of a high-quality and high-elasticity SEI film during the cyclic charging and discharging process, that is, the release rate matches the growth rate and quality of the SEI film. Then, polysulfides are formed through the electron-gaining reaction of elemental sulfur, thereby initiating the ring-opening polymerization of cyclic carbonates, or the ring-opening polymerization of cyclic carbonates is directly initiated by polysulfides, forming an elastic SEI film in situ.

[0054] In some embodiments of the present invention, the insoluble sulfur content in the sulfur-containing additive needs to reach more than 30% of the total sulfur element percentage, and preferably, the insoluble sulfur content in the sulfur-containing additive accounts for more than 70% of the total sulfur element percentage.

[0055] In the technical solution of this invention, when the content of insoluble sulfur in the sulfur-containing additive accounts for more than 30% of the total sulfur element, compared with the solution where the ratio of insoluble sulfur content to total sulfur element is less than 30%, the sulfur-containing additive has a higher rate of depolymerization into elemental sulfur and can better meet the specific requirements for the growth of high-quality and high-elasticity SEI film during cyclic charging and discharging. That is, its release rate matches the growth rate and quality of SEI film, and the higher content of insoluble sulfur is more suitable for the formation of SEI film. Preferably, when the insoluble sulfur content in the sulfur-containing additive accounts for more than 70% of the total sulfur element, the rate at which the sulfur-containing additive depolymerizes to generate elemental sulfur is higher than that of the scheme where the insoluble sulfur content in the sulfur-containing additive accounts for more than 30% of the total sulfur element. This is because the rate at which the sulfur-containing additive depolymerizes to generate elemental sulfur is greater and can better meet the specific requirements for the growth of a high-quality, high-elasticity SEI film during cyclic charging and discharging. That is, its release rate matches the growth rate and quality of the SEI film, and the higher insoluble sulfur content is more suitable for the formation of the SEI film, thereby forming an elastic SEI film in situ during more cycles of lithium-ion battery charging and discharging.

[0056] In some embodiments of the present invention, the molecular weight of the polymeric sulfur is 0.1 million to 300,000, preferably 10,000 to 50,000.

[0057] In the technical solution of this invention, when the molecular weight of the polymerized sulfur is between 0.1 million and 300,000, an elastic SEI film can be formed in situ during a suitable number of lithium-ion battery charge-discharge cycles. Furthermore, the stability of elemental sulfur release can be optimized by selecting a polymerized sulfur with a suitable molecular weight. When the molecular weight of the polymerized sulfur is between 10,000 and 50,000, the stability of elemental sulfur release can be further optimized by selecting a polymerized sulfur with a suitable molecular weight, thereby enabling the formation of an elastic SEI film in situ during an even greater number of lithium-ion battery charge-discharge cycles.

[0058] In some embodiments of the present invention, the organic polysulfide includes at least one of diisopropyltrisulfide, bis-[γ-(triethoxysilyl)propyl]-tetrasulfide, and tert-dodecyl polysulfide; the metal polysulfide includes at least one of molybdenum disulfide, lithium sulfide, and titanium sulfide; and the sulfur-containing organic polymer includes at least one of poly(o-thiocarbamate) and polysulfide rubber.

[0059] In the technical solution of this invention, the sulfur-containing organic polymer can slowly release elemental sulfur, and through the reaction of elemental sulfur on the electrode surface, an elastic SEI film is formed in situ during the cyclic charging and discharging of the lithium-ion battery. Organic polysulfides and metal polysulfides can directly initiate the ring-opening polymerization of cyclic carbonates and cause an elastic SEI film to be formed in situ during the cyclic charging and discharging of the lithium-ion battery.

[0060] In some embodiments of the present invention, the sulfur-containing additive further includes a stabilizer, which includes at least one of elemental sulfur, halogens, halides, thiazole compounds, iodonitrobenzene, and alkali metal compounds.

[0061] In the technical solution of this invention, the end capping group reduces the probability of free radicals formed by the loss of electrons at both ends of the sulfur-containing additive, delays the time for free radicals to form by the loss of electrons at both ends of the sulfur-containing additive, and makes the rate of release of elemental sulfur from polymerized sulfur more stable, or increases the concentration of elemental sulfur, so that the decomposition reaction is slowed down due to the increase in the concentration of elemental sulfur.

[0062] The specific decomposition reactions are as follows:

[0063]

[0064] M is an end-capping group;

[0065]

[0066]

[0067]

[0068] That is, firstly, the end capping groups at both ends of the polymer are removed, causing the polymerized sulfur to form polymerized sulfur with free radicals at both ends, and then it is gradually released into elemental sulfur until it is completely converted into elemental sulfur.

[0069] In addition, stabilizers may include, but are not limited to, olefins, such as benzocyclopropene and isoprene, to end-cap polymeric sulfur.

[0070] In some embodiments of the present invention, the weight percentage of the stabilizer relative to the weight percentage of the sulfur-containing additive is 0.1%-10%, preferably 1%-5%.

[0071] In this invention, when the weight of the stabilizer is between 0.1% and 10%, the release rate of the sulfur-containing additive can be controlled within a suitable range, resulting in a more stable, reliable, and higher-quality SEI film formed by the lithium-ion battery during a suitable number of charge-discharge cycles. When the weight of the stabilizer is between 1% and 5%, the release rate of the sulfur-containing additive can be controlled within an even more suitable range, resulting in a more stable, reliable, and higher-quality SEI film formed by the lithium-ion battery during an even greater number of charge-discharge cycles.

[0072] In some embodiments of the present invention, the polymeric sulfur is end-capped polymeric sulfur with the molecular formula MSS. (8n-2)-SM, where n is a natural number greater than 0, and M includes at least one of halogens, halides, thiazole compounds, iodonitrobenzene, and alkali metal compounds.

[0073] In the technical solution of this invention, since the polymeric sulfur needs to release elemental sulfur more stably, it is necessary to end-cap the polymeric sulfur. End-capping reduces the probability of the polymeric sulfur having free radicals at both ends, delays the time it takes for the sulfur-containing additive to lose electrons and form free radicals, and makes the rate of elemental sulfur release from the polymeric sulfur more stable. Stabilizers used for end-capping include at least one of halogens, halides, thiazole compounds, iodonitrobenzene, and alkali metal compounds. In addition, olefinic stabilizers, including but not limited to olefinic stabilizers such as benzocyclopropene and isoprene, can also be used to end-cap the polymeric sulfur.

[0074] In some embodiments of the present invention, the sulfur-containing organic polymer includes a polymeric sulfur-polythiophene copolymer, a polymeric sulfur-polypyrrole copolymer, and a polymeric sulfur-polyaniline copolymer, and the copolymer of polymeric sulfur with carbon materials includes a polymeric sulfur-carbon nanotube graft copolymer and / or a polymeric sulfur-graphene copolymer.

[0075] In the technical solution of this invention, the sulfur-containing organic polymer can be a block copolymer, a graft copolymer, or a combination of block copolymers and graft copolymers. The block copolymer-type sulfur-containing organic polymer comprises a first block and a second block, with the first and second blocks arranged alternately. The first block is a polysulfide block, and the degree of polymerization of the repeating unit of the polysulfide block is 2-10000. The second block includes, but is not limited to, at least one of polythiophene blocks, polypyrrole blocks, and polyaniline blocks. The degree of polymerization of the repeating unit of the polythiophene block, polypyrrole block, and polyaniline block is 2-800. The number average molecular weight of the block copolymer-type sulfur-containing organic polymer copolymer is 0.1 million to 1 million. Graft copolymers of sulfur-containing organic polymers have a backbone composed of conductive monomers polymerized into a main chain. The monomer units are conductive monomers, and the branches are polysulfide chains. The backbone includes, but is not limited to, polythiophene, polypyrrole, and polyaniline. The degree of polymerization of the repeating units in the backbone and the polysulfide chains is both 2-10,000. The number-average molecular weight of the graft copolymers is 0.1 million to 1 million. Alternatively, copolymers of polysulfide and carbon materials involve grafting polysulfide onto carbon materials, including, but not limited to, carbon nanotubes and / or graphene. For example, the diameter of the carbon nanotubes is preferably 0.2-100 nm to ensure good electrical conductivity. The degree of polymerization of the structural units of the polysulfide is 2-10,000. The aforementioned sulfur-containing additives also contain end-capping groups, forming sulfur-conductive polymer copolymers with end-capping groups. For example, the end-capping groups include at least one selected from halogens, halides, thiazole compounds, iodonitrobenzene, alkali metal compounds, and olefin groups. The olefin group may include at least one selected from benzocyclopropenyl, isoprene, and allyl. Because the aforementioned sulfur-containing additives possess polymeric sulfur blocks and branched chains, they can slowly release polymeric sulfur, promoting the formation of a high-quality SEI film.

[0076] This invention does not limit the preparation method of the sulfur-conductive polymer copolymer containing end-capped groups, and can be prepared by referring to the preparation methods commonly used by those skilled in the art.

[0077] In some embodiments, sulfur and precursors such as thiophene, pyrrole, and aniline containing the above-mentioned end-capping groups can be mixed and added to a flask, reacted in an oil bath at 170°C for 1 hour, then cooled to room temperature, washed with carbon disulfide and dried to obtain the above-mentioned sulfur-conductive polymer copolymer containing end-capping groups.

[0078] In some embodiments of the present invention, the electrical conductivity of the sulfur-containing additive is 10 to 100 S / cm.

[0079] In the technical solution of this invention, the conductivity of the sulfur-containing additive is 10 to 100 S / cm, which meets the conductivity requirements of this invention, enabling the lithium-ion battery to have suitable conductivity and cycle charge-discharge efficiency while reducing the decrease in battery density and capacity.

[0080] In some embodiments of the present invention, the negative electrode active material is 80-99 parts, the conductive agent is 0.2-10 parts, the binder is 1-10 parts, and the sulfur-containing additive is 0.1-5 parts.

[0081] In this invention, when the negative electrode active material is 80-99 parts, the increase in reduction potential during the reaction process can be reduced while ensuring a suitable lithium-ion capacity. When the conductive agent is 0.2-10 parts, the decrease in battery density and capacity can be reduced while ensuring a suitable conductivity. When the binder is 1-10 parts, the problem of excessive density in lithium-ion batteries containing binders during processing can be reduced while ensuring a suitable bonding effect. When the sulfur-containing additive is 0.1-5 parts, an elastic SEI film can be formed in situ during a suitable number of lithium-ion battery charge-discharge cycles, and the release stability of elemental sulfur can be improved. For example, the negative electrode active material can be graphite, the conductive agent can be acetylene black, the binder can be polyvinyl fluoride, and the dispersant can be sodium carboxymethyl cellulose.

[0082] In some embodiments of the present invention, the molecular weight of the sulfur-containing additive is 0.2 million to 500,000, preferably, the molecular weight of the sulfur-containing additive is 10,000 to 50,000.

[0083] In this invention, when the molecular weight of the sulfur-containing additive is between 0.2 million and 500,000, its conductivity is suitable, and the slow release rate of elemental sulfur is optimized, making the SEI film generated by the lithium-ion battery more stable, reliable, and of better quality during long-term charge-discharge cycles. Preferably, when the molecular weight of the sulfur-containing additive is between 10,000 and 50,000, its conductivity is even more suitable, and the slow release rate of elemental sulfur is further optimized, making the SEI film generated by the lithium-ion battery more stable, reliable, and of better quality during more cycles of charge-discharge.

[0084] The present invention also provides a battery assembly, comprising the battery cells described in the above technical solutions.

[0085] Since the battery assembly adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be repeated here.

[0086] The present invention also provides a battery comprising the battery assembly described in the above technical solution.

[0087] Since the battery adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be repeated here.

[0088] The present invention also provides an electrical device, including the battery described in the above technical solution.

[0089] Since the electrical equipment adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be repeated here.

[0090] This invention employs a sulfur-containing additive in the negative electrode slurry. This additive continuously decomposes at the negative electrode to form elemental sulfur, which then undergoes a reduction reaction on the negative electrode surface, transforming into polysulfides. These polysulfides initiate ring-opening polymerization of cyclic carbonates, forming an elastic SEI film in situ. Because this invention uses an in-situ addition of the sulfur-containing additive to the negative electrode slurry, the efficiency of SEI film formation is higher, and the amount added is less. Furthermore, the use of a sulfur-containing additive significantly reduces the generation of gaseous compounds, thereby further reducing electrode material delamination and battery expansion.

[0091] The specific implementation method is as follows:

[0092] Example 1

[0093] In this embodiment, the cathode uses Li(Ni,Co,Mn)O2 ternary material, purchased from Rongbai New Energy Technology Co., Ltd., with a designed specific capacity of 201 mAh / g. The positive electrode active material has a mass fraction of 95%, the binder PVDF has a mass fraction of 3%, and the conductive agent has a mass fraction of 2%. The electrode coating weight is 13 mg / mm². 2 The compacted density is 3.4 g / cm³. 3 The electrode sheet is prepared through processes such as stirring, coating, and cold pressing.

[0094] In this embodiment, the anode uses artificial graphite, the negative electrode active material has a mass fraction of 95%, the binder SBR has a mass fraction of 1.8%, the dispersant CMC has a mass fraction of 1.2%, the conductive agent has a mass fraction of 1%, and the composition of polymeric sulfur and elemental sulfur has a total mass fraction of 1%, with elemental sulfur accounting for 30% and polymeric sulfur accounting for 70%. The electrode sheet is prepared through processes such as stirring, coating, and cold pressing, and the final compaction density of the electrode sheet is 1.7 g / cm³. 3 The electrode thickness is 56 μm, and the current collector thickness is 8 μm.

[0095] In this embodiment, an EC:EMC ratio of 1:1 and a 1M LiPF6 electrolyte were used. To compare different anode designs, all subsequent cathodes and electrolytes used the same design.

[0096] Finally, the upper electrode and electrolyte are assembled into a stacked battery cell, and the packaging material is aluminum-plastic film.

[0097] The differences between Examples 2-4 and Example 1 are shown in Table 1. The indicators not listed in the table are the same as those in Example 1.

[0098] Comparative Example 1

[0099] The cathode and electrolyte of Comparative Example 1 were designed the same as those in Example 1. The anode used artificial graphite, the negative electrode active material had a mass fraction of 97%, the binder SBR had a mass fraction of 1%, the dispersant CMC had a mass fraction of 1%, and the conductive agent had a mass fraction of 1%. The electrode was prepared through processes such as stirring, coating, and cold pressing, and the final compacted density of the electrode was 1.7 g / cm³. 3 The electrode thickness is 56 μm, and the current collector thickness is 8 μm.

[0100] Finally, the upper electrode and electrolyte are assembled into a stacked battery cell, and the packaging material is aluminum-plastic film.

[0101] Table 1

[0102]

[0103]

[0104] Performance characterization:

[0105] The following tests were performed on the battery cells prepared in the examples and comparative examples:

[0106] 25℃ Cyclic Test: Under 25℃ conditions, first test the cell capacity C0, then discharge the cell at a discharge rate of 0.33C0, and charge it using a constant current and constant voltage process at the same rate. Repeat this process until the capacity is less than 0.8C0.

[0107] 45℃ Cyclic Test: First, test the cell's capacity C0; then, at 45℃, discharge the cell at a discharge rate of 0.33C0, and charge it using a constant current and constant voltage process at the same rate. Repeat this process until the capacity is less than 0.8C0.

[0108] Table 2 shows the results comparison:

[0109] Table 2

[0110] Grouping Cyclic degradation to 80% at 25℃ Cyclic degradation to 80% at 45℃ Example 1 1983 1235 Example 2 2380 1532 Example 3 2123 1478 Example 4 2497 1589 Comparative Example 1 1227 789

[0111] As shown in Tables 1 and 2, in Examples 1 to 4, sulfur-containing additives were added to the negative electrode slurry. This allowed the sulfur-containing additives to continuously decompose at the negative electrode to form elemental sulfur, which then underwent a reduction reaction on the negative electrode surface to transform into polysulfides. The polysulfides initiated the ring-opening polymerization of cyclic carbonates, forming an elastic SEI film in situ. Furthermore, since sulfur-containing additives were used, the generation of gaseous compounds was greatly reduced, thereby further reducing the occurrence of electrode material delamination and battery expansion, which in turn improved the durability of the battery cell.

[0112] The negative electrode slurry of Comparative Example 1 does not contain sulfur-containing additives. Its battery cell only cycled 1227 times in the test of 80% degradation at 25°C and only 789 times in the test of 80% degradation at 45°C, indicating a decrease in its durability.

[0113] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A negative electrode slurry, characterized by, The negative electrode slurry comprises a negative electrode active material, a conductive agent, a binder, and a sulfur-containing additive, the sulfur-containing additive comprising polymeric sulfur or a combination of the polymeric sulfur and at least one of elemental sulfur composition, organic polysulfide, metal polysulfide, sulfur-containing organic polymer, and copolymer of polymeric sulfur and carbon material; The polymeric sulfur is a capped polymeric sulfur with a molecular formula of M-S-S(8n-2)-S-M, n is a natural number greater than 0, and M comprises at least one of halogen, halide, azide compound, iodo-nitrobenzene, and alkali metal compound.

2. The negative electrode slurry of claim 1, wherein the carbon-based material is selected from the group consisting of graphite, carbon black, and carbon nanotubes. The insoluble sulfur content in the sulfur-containing additive accounts for more than 30% of the total sulfur element percentage.

3. The negative electrode slurry of claim 2, wherein the carbon-based material is selected from the group consisting of carbon black, graphite, and carbon nanotubes. The insoluble sulfur content in the sulfur-containing additive accounts for more than 70% of the total sulfur element percentage.

4. The negative electrode slurry according to any one of claims 1 to 3, wherein The molecular weight of the polymeric sulfur is 0.1-300,000.

5. The negative electrode slurry of claim 4, wherein the carbon-based material is selected from the group consisting of carbon black, acetylene black, ketjen black, and super-P. The molecular weight of the polymeric sulfur is 10,000-50,000.

6. The negative electrode slurry of claim 4, wherein the carbon-based material is selected from the group consisting of carbon black, acetylene black, ketjen black, and super-P. The organic polysulfide comprises at least one of diisopropyl trisulfide, bis-[γ-(triethoxysil)propyl]-tetrasulfide, and tertiary-dodecyl polysulfide; the metal polysulfide comprises at least one of molybdenum disulfide, lithium sulfide, and titanium sulfide; and the sulfur-containing organic polymer comprises at least one of poly(o-thio carbamate) and polysulfide rubber.

7. The negative electrode slurry according to any one of claims 1 to 6, wherein The sulfur-containing additive further comprises a stabilizer, the stabilizer comprising at least one of elemental sulfur, halogen, halide, azide compound, iodo-nitrobenzene, and alkali metal compound.

8. The negative electrode slurry of claim 7, wherein the carbon-based material is selected from the group consisting of carbon black, graphite, and carbon nanotubes. The weight of the stabilizer accounts for 0.1%-10% of the weight percentage of the sulfur-containing additive.

9. The negative electrode slurry of claim 8, wherein the carbon-based material is selected from the group consisting of carbon black, graphite, and a combination thereof. The weight of the stabilizer accounts for 1%-5% of the weight percentage of the sulfur-containing additive.

10. The negative electrode slurry according to any one of claims 2 to 9, wherein The sulfur-containing organic polymer further comprises polymeric sulfur-polythiophene copolymer, polymeric sulfur-pyrrole copolymer, and polymeric sulfur-aniline copolymer, and the copolymer of polymeric sulfur and carbon material comprises polymeric sulfur-carbon nanotube graft copolymer and / or polymeric sulfur-graphene copolymer.

11. The negative electrode slurry of claim 10, wherein the carbon-based material is selected from the group consisting of graphite, carbon black, and carbon nanotubes. The conductivity of the sulfur-containing additive is 10-100 S / cm.

12. The negative electrode slurry according to claim 10 or 11, wherein The molecular weight of the sulfur-containing additive is 0.2-500,000.

13. The negative electrode slurry of claim 12, wherein the carbon-based material is selected from the group consisting of graphite, carbon black, and carbon nanotubes. The molecular weight of the sulfur-containing additive is 10,000-50,000.

14. The negative electrode slurry according to any one of claims 1 to 13, wherein The negative electrode active material is 80-99 parts, the conductive agent is 0.2-10 parts, the binder is 1-10 parts, and the sulfur-containing additive is 0.1-5 parts.

15. A negative electrode sheet characterized by comprising: The negative electrode slurry comprises the negative electrode slurry according to any one of claims 1-14.

16. A battery cell, characterized by The negative electrode tab comprises the negative electrode tab according to claim 15.

17. A battery, characterized by The battery cell comprises the battery cell according to claim 16.

18. An electrical device, characterized by The battery comprises the battery according to claim 17.

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