Lithium ion battery
By adding sulfonate compounds to lithium-ion batteries and controlling their degree of order ratio B/A with the positive electrode active material, a stable interface film is formed, which solves the battery performance problem caused by abnormal positive electrode material structure and improves the cycle stability and rate performance of the battery.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHENZHEN HIGHPOWER TECH CO LTD
- Filing Date
- 2025-10-23
- Publication Date
- 2026-05-22
AI Technical Summary
In existing technologies, abnormal microstructure of cathode materials in lithium-ion batteries leads to obstructed ion transport channels, reduced diffusion efficiency, increased interfacial side reactions, and accelerated electrolyte consumption. There is a lack of synergistic consideration of key structural parameters of cathode materials, and the film-forming effect of sulfonate compounds is difficult to adapt to the material structure, making precise repair impossible.
By adding sulfonate compounds to the electrolyte and controlling the ratio of their content to the degree of order of cations in the positive electrode active material (B/A), the sulfonate compounds are adapted to the defect sites in the positive electrode active material, forming a stable and robust interfacial film during charging and discharging, thereby improving the interfacial stability of the positive electrode active material.
It achieves precise repair of battery performance, improves the cycle stability and rate performance of lithium-ion batteries, and avoids the problems of increased internal resistance and increased lithium-ion migration resistance caused by uneven film formation.
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Abstract
Description
Technical Field
[0001] This application relates to the field of lithium-ion battery technology, and more particularly to lithium-ion batteries. Background Technology
[0002] In the field of lithium-ion batteries, the microstructure of the cathode material has a decisive influence on its electrochemical performance. Abnormalities in certain intrinsic structural features of the material will directly lead to obstructed ion transport channels and reduced diffusion efficiency. Simultaneously, increased interfacial side reactions and accelerated electrolyte consumption also restrict the improvement of battery cycle life. Therefore, achieving synergistic matching between the internal structure of the material and the external electrolyte components is crucial for improving the overall performance of the battery.
[0003] In related technologies, a common approach to improve battery cycle stability is to introduce additives, such as sulfonate compounds, into the electrolyte. Sulfonate compounds can participate in the formation of an interfacial protective film on the positive electrode surface, reducing side reactions between the electrolyte and the highly active positive electrode material, thereby protecting the positive electrode interface to some extent and delaying capacity decay.
[0004] However, the above approach only focuses on adjusting the electrolyte side and lacks a synergistic consideration of the key structural parameters of the cathode material. This singular application method makes it difficult for the film-forming effect of sulfonate compounds to adapt to the structural state of the material, thus failing to achieve precise repair of defects. Summary of the Invention
[0005] To address or partially address the problems existing in related technologies, this application provides a lithium-ion battery that, through the synergistic interaction of internal and external electrolyte components in the positive electrode active material, enables the film-forming effect of sulfonate compounds to adapt to the structural state of the positive electrode active material, thereby achieving precise repair of battery performance defects and effectively improving battery performance.
[0006] This application provides a lithium-ion battery, comprising a positive electrode, a negative electrode, and an electrolyte. The positive electrode includes a positive current collector and a positive active material layer disposed on at least one side of the positive current collector. The positive active material layer includes a positive active material, which is spinel lithium nickel manganese oxide. The ratio of the intensity of the ordered crystal peak to the intensity of the disordered crystal peak in the X-ray diffraction pattern of the positive active material is A. The electrolyte includes an additive, which includes a sulfonate compound. The sulfonate compound has a mass percentage of B% in the electrolyte. The lithium-ion battery satisfies the condition: 0.7 ≤ B / A ≤ 5.
[0007] As an optional embodiment, the sulfonate compound includes at least one compound selected from structural formulas I and II:
[0008]
[0009] R11 is selected from one of substituted or unsubstituted C1 to C4 alkylene groups, substituted or unsubstituted C2 to C4 alkenyl groups, and substituted or unsubstituted C1 to C6 chain heteroalkylene groups, wherein the chain heteroalkylene group has 1 to 5 heteroatoms, and the heteroatoms in the chain heteroalkylene group are selected from at least one of O, N, P or S.
[0010] R21 and R22 are each independently selected from one of the following: halogen atom, cyano group, substituted or unsubstituted C1 to C10 alkyl group, substituted or unsubstituted C2 to C10 alkenyl group, and substituted or unsubstituted C2 to C10 alkynyl group.
[0011] As an optional embodiment, the sulfonate compound is selected from at least one of 1,3-propanesulfonate lactone, mannitol sulfate carbonate, and 4-methyl ethyl sulfate.
[0012] As an alternative embodiment, 0.85 ≤ B / A ≤ 4.5; and / or, 1 ≤ A ≤ 3; and / or, 2 ≤ B ≤ 6.
[0013] As an optional embodiment, the intensity of the ordered crystal peak in the X-ray diffraction pattern of the positive electrode active material is the intensity of the crystal peak on the (111) plane, and the intensity of the disordered crystal peak is the intensity of the crystal peak on the (311) plane.
[0014] As an optional embodiment, the additive also includes a fluorinated compound.
[0015] As an optional embodiment, the fluorinated compound is selected from at least one of fluoroethylene carbonate, trifluoroethyl methyl carbonate, difluoroacetamide, fluorocarbamate, fluorotetramethylene sulfone, triethyl fluorophosphate, 2,2,2-trifluoroethyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, ethyl 2,2-difluoroacetate, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, fluorobenzene, fluoroacetonitrile, and fluoroadiponitrile; and / or,
[0016] The mass percentage of the fluorinated compound in the electrolyte is N%, 2≤N≤10; and / or, 2≤(B+N) / A≤10.
[0017] As an optional embodiment, the additive also includes nitrile compounds.
[0018] As an optional embodiment, the nitrile compound is selected from bis(nitrile) and / or 1,3,6-hexanetrionitrile.
[0019] As an optional embodiment, the adiponitrile in the electrolyte is 1% to 5% by mass; and / or, the 1,3,6-hexanetrionitrile in the electrolyte is 0.5% to 3% by mass.
[0020] The technical solution provided in this application may include the following beneficial results:
[0021] This application introduces sulfonate compounds into the electrolyte while controlling the ratio B / A of the sulfonate compound content (B) to the degree of cation order (A) in the positive electrode active material. This allows the sulfonate compound to interact effectively with defect sites in the positive electrode active material, participating in interfacial reactions during charge and discharge. It then forms a stable and robust interfacial film containing sulfonate compounds on the surface of the positive electrode active material, improving its interfacial stability and thus enhancing the battery's cycle stability. Furthermore, when B / A is too low (high A value, many positive electrode defects) and the additive content is too low (low B value), the additive is insufficient to repair all highly active defects, resulting in an incomplete CEI film. Conversely, when B / A is too high (low A value, few positive electrode defects) and the additive content is too high (high B value), the resulting CEI film is too thick, increasing resistance to lithium-ion migration, leading to increased internal resistance and affecting rate performance and capacity. Therefore, this application achieves a uniform and complete CEI film by controlling the ratio to 0.7 ≤ B / A ≤ 5, thereby improving the battery's cycle stability.
[0022] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Detailed Implementation
[0023] The embodiments of this application will now be described in more detail. It should be understood that this application may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to make this application more thorough and complete, and to fully convey the scope of this application to those skilled in the art.
[0024] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.
[0025] It should be understood that although the terms "first," "second," "third," etc., may be used in this application to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.
[0026] In related technologies, a common approach to improve battery cycle stability is to introduce additives, such as sulfonate compounds, into the electrolyte. Sulfonate compounds can participate in the formation of an interfacial protective film on the cathode surface, reducing side reactions between the electrolyte and the highly active cathode material, thereby protecting the cathode interface to some extent and delaying capacity decay. However, this approach focuses solely on adjusting the electrolyte side, lacking a synergistic consideration of the key structural parameters of the cathode material. This singular application method makes it difficult for the film-forming effect of sulfonate compounds to adapt to the material's structural state, hindering precise defect repair.
[0027] To address the aforementioned issues, this application provides a lithium-ion battery in which the film-forming effect of sulfonate compounds is adapted to the structural state of the positive electrode active material through the synergistic interaction of internal and external electrolyte components of the positive electrode active material. This enables precise repair of battery performance defects and effectively improves battery performance.
[0028] This application provides a lithium-ion battery, including a positive electrode, a negative electrode, and an electrolyte. The positive electrode includes a positive current collector and a positive active material layer disposed on at least one side of the positive current collector. The positive active material layer includes a positive active material, which includes spinel lithium nickel manganese oxide. The ratio of the intensity of the ordered crystal peak to the intensity of the disordered crystal peak in the X-ray diffraction pattern of the positive active material is A. The electrolyte includes additives, including sulfonate compounds. The mass percentage of the sulfonate compounds in the electrolyte is B%. The lithium-ion battery satisfies: 0.7 ≤ B / A ≤ 5.
[0029] The embodiments of this application no longer improve the cathode material or electrolyte in isolation, but improve the battery cycle stability through the "synergistic effect" between the two.
[0030] In the embodiments of this application, the positive electrode active material includes spinel lithium nickel manganese oxide (LiNi). 0.5 Mn 1.5 In the spinel structure, oxygen ions form a face-centered cubic close-packed structure, with metal cations filling the gaps in the oxygen ion framework. Specifically: lithium ions (Li... +Nickel ions (Ni) fill the tetrahedral interstitial sites. 2+ / Ni 3+ ) and manganese ions (Mn 3+ / Mn 4+ The lithium spinel nickel manganese oxide (LiMO) is filled with lithium ions at the octahedral interstitial sites. The average operating voltage of LiMO is as high as 4.7V, resulting in high gravimetric and volumetric energy densities. Furthermore, the spinel structure provides three-dimensional lithium-ion diffusion channels, allowing for rapid lithium-ion migration and enabling fast charging and discharging. Moreover, compared to layered ternary materials, the spinel structure is more stable after delithiation, less prone to oxygen evolution reactions, and reduces the risk of thermal runaway under abusive conditions such as high temperatures and overcharging, making it safer than high-nickel ternary batteries.
[0031] However, when spinel lithium nickel manganese oxide materials are working under high voltage (~4.7V), the electrolyte is easily oxidized and decomposed, making the formed CEI film loose and porous, unable to effectively protect the positive electrode. Moreover, the positive electrode active material continues to react with the electrolyte, causing the positive electrode structure to be destroyed (such as the dissolution of manganese and nickel).
[0032] In the X-ray diffraction pattern of the positive electrode active material, the ratio A of the intensity of the ordered crystal peak to the intensity of the disordered crystal peak represents the degree of order of the cations in the positive electrode active material. The lower the A value, the more surface defects there are in the crystal material and the more serious the mixing of cations. These defect sites are the "hot spots" for catalytic oxidation and decomposition of the electrolyte.
[0033] This application embodiment adds a sulfonate ester compound to the electrolyte while controlling the ratio B / A of the sulfonate ester compound content B to the degree of order A of the cations in the positive electrode active material. This allows the sulfonate ester compound to interact well with the defect sites in the positive electrode active material, participate in the interfacial reaction during charge and discharge, and form a stable and robust interfacial film containing the sulfonate ester compound on the surface of the positive electrode active material. This improves the interfacial stability of the positive electrode active material, thereby giving the battery higher cycle stability.
[0034] Furthermore, when the B / A ratio is too low (i.e., many positive electrode defects (high A value) and low additive content (low B value), the additives are insufficient to "repair" all highly active defect points, resulting in an incomplete CEI film. Conversely, when the B / A ratio is too high (i.e., few positive electrode defects (low A value) and high additive content (high B value), the resulting CEI film is too thick, increasing the resistance to lithium-ion migration, leading to increased internal resistance of the battery, and affecting rate performance and capacity. Therefore, the embodiments of this application, by controlling the B / A ratio to 0.7 ≤ B / A ≤ 5, can form a uniform and complete CEI film, improving the cycle stability of the battery.
[0035] As an optional embodiment, the sulfonate compound includes at least one selected from compounds of structural formula I and structural formula II:
[0036]
[0037] R11 is selected from one of substituted or unsubstituted C1 to C4 alkylene groups, substituted or unsubstituted C2 to C4 alkenyl groups, and substituted or unsubstituted C1 to C6 heteroalkyl groups, wherein the number of heteroatoms in the heteroalkyl group is 1 to 5, and the heteroatoms in the heteroalkyl group are selected from at least one of O, N, P or S.
[0038] R21 and R22 are each independently selected from one of the following: halogen atom, cyano group, substituted or unsubstituted C1 to C10 alkyl group, substituted or unsubstituted C2 to C10 alkenyl group, and substituted or unsubstituted C2 to C10 alkynyl group.
[0039] As a preferred embodiment, the sulfonate compound is selected from at least one of 1,3-propanesulfonic acid lactone, mannitol sulfate carbonate, and 4-methyl ethyl sulfate.
[0040] The sulfonate compounds selected in this application contain both cyclic esters and sulfonic acid groups in their molecular structure. Under high voltage, they undergo electrochemical oxidation on the positive electrode surface earlier than the basic electrolyte solvent. Furthermore, after decomposition, they form a CEI film rich in organic sulfonate esters / inorganic lithium sulfate and other components on the positive electrode surface.
[0041] As an alternative embodiment, 0.85 ≤ B / A ≤ 4.5.
[0042] By further controlling 0.85≤B / A≤4.5, the cycle stability of the battery can be further improved in the embodiments of this application.
[0043] As an optional embodiment, 1 ≤ A ≤ 3.
[0044] In the embodiments of this application, if the value of A is too large, it indicates that the lithium ion occupancy is abnormal or the distribution of transition metal ions is disordered, which will cause the lithium ion insertion and extraction channels to be blocked by transition metal ions, reduce the ion diffusion coefficient, and increase the lattice stress during cycling, which is prone to structural distortion. If the value of A is too small, it indicates that the lithium ion order is reduced and the defects increase, which will lead to intensified interface reactions and deteriorate the battery cycle performance.
[0045] Where A can be 1, 2, 3, or any value within the range specified above, this application does not limit it.
[0046] As an alternative embodiment, 2 ≤ B ≤ 6.
[0047] In this embodiment, if the B value is too low, the film formation effect will be limited, which is not conducive to long-term cycling; if the B value is too high, the positive electrode film formation resistance will increase, leading to lithium plating.
[0048] Wherein, B can be 2, 3, 4, 5, 6, or any value within the above-mentioned range, and this application does not limit it in this regard.
[0049] As an optional embodiment, the intensity of the ordered crystal peak in the X-ray diffraction pattern of the positive electrode active material is the intensity of the crystal peak on the (111) plane, and the intensity of the disordered crystal peak is the intensity of the crystal peak on the (311) plane.
[0050] The positive electrode active material in this application embodiment contains spinel lithium nickel manganese oxide, whose internal atoms (lithium, nickel, manganese, and oxygen) are not randomly stacked, but arranged in a three-dimensional space according to certain rules and periodicity to form a crystal structure. In the X-ray diffraction pattern of the positive electrode active material, the intensity ratio A of the diffraction peaks of the (111) plane and the (311) plane is an indicator reflecting the order and anisotropy of the crystal structure.
[0051] In XRD patterns, diffraction peaks at different positions represent different families of crystal planes. The intensity of a diffraction peak (i.e., its height or area) depends primarily on the type, number, and arrangement of atoms on that crystal plane. Crystal planes with higher atomic numbers and higher densities typically produce stronger diffraction peaks. In the XRD pattern of spinel lithium nickel manganese oxide:
[0052] The diffraction peaks of the (111) plane are signals generated by X-rays diffracted from all (111) crystal planes in the crystal.
[0053] The diffraction peaks of the (311) plane are signals generated by X-rays diffracted from all (311) crystal planes in the crystal.
[0054] As an optional embodiment, the additive also includes fluorinated compounds.
[0055] In the embodiments of this application, fluorinated compounds have a better film-forming effect, which can improve the high-temperature performance and cycle performance of the battery.
[0056] In this embodiment, fluorinated compounds can synergistically oxidize and decompose with sulfonate compounds, jointly participating in the formation of the positive electrode CEI film. After decomposition, the fluorinated compounds introduce robust LiF components into the film. LiF possesses high modulus, high stability, and good ionic conductivity, significantly improving the compactness, mechanical strength, and chemical stability of the CEI film. Furthermore, the fluorinated compounds can preferentially adsorb and passivate highly active defect sites on the surface of the positive electrode material, inhibiting the oxidative decomposition of the electrolyte and the dissolution of transition metals, thereby improving the battery's cycle life.
[0057] As a preferred embodiment, the fluorinated compound includes at least one selected from fluoroethylene carbonate, trifluoroethyl methyl carbonate, difluoroacetamide, fluorocarbamate, fluorotetramethylene sulfone, triethyl fluorophosphate, 2,2,2-trifluoroethyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, ethyl 2,2-difluoroacetate, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, fluorobenzene, fluoroacetonitrile, and fluoroadiponitrile.
[0058] The fluorinated compounds provided in this application, including some fluorinated solvents (such as trifluoroethyl methyl carbonate), possess high electrochemical oxidation stability, which can directly improve the high-voltage resistance of the electrolyte system and reduce electrolyte decomposition. Some phosphorus-containing fluorinated compounds (such as fluorophosphates) can capture trace amounts of moisture or inhibit the hydrolysis of LiPF6, reducing HF formation. Some organofluorine compounds (such as fluorophosphates) have certain flame-retardant effects.
[0059] In a preferred embodiment, the mass percentage of the fluorinated compound in the electrolyte is N%, 2≤N≤10.
[0060] In this embodiment, if N is too low, it will not be sufficient to maintain long cycles; if N is too high, it may lead to deterioration of gas production due to insufficient oxidation resistance.
[0061] Wherein, N can be 2, 4, 5, 8, 10, or any value within the above-mentioned range, and this application does not limit it.
[0062] In a preferred embodiment, the mass percentage of the fluorinated compound in the electrolyte is N%, and 2 ≤ (B+N) / A ≤ 10.
[0063] In the embodiments of this application, (B+N) / A represents the ratio of the sum of the content B of the sulfonate compound and the content N of the fluorine-containing compound to the degree of order A of the cations in the positive electrode active material.
[0064] If (B+N) / A is too low, it indicates that the amount of sulfonate compound and fluorine compound used is too low, which cannot guarantee the formation of a sufficiently thick and complete composite interface film on the positive and negative electrode surfaces, leading to deterioration of battery cycle performance. If (B+N) / A is too high, it indicates that the amount of sulfonate compound and fluorine compound used is too high, which will form an excessively thick composite interface film, hindering lithium ion transport and leading to lithium plating.
[0065] As an optional embodiment, the additive also includes nitrile compounds.
[0066] In the embodiments of this application, nitrile compounds can complex transition metal ions, improving the high-temperature performance of the battery. Moreover, the -C≡N groups also participate in the formation of the interface film, generating a stable CEI layer rich in nitrides, which complements the interface film components containing sulfur (sulfonate esters) and fluorine (fluorine compounds), forming a more stable "ternary" or "multi-element" composite film.
[0067] As a preferred embodiment, the nitrile compound is selected from dinitrile and / or 1,3,6-hexanetrinitrile.
[0068] Adiponitrile has a moderate chain length and two fixed cyano groups, resulting in stable and reliable film formation.
[0069] 1,3,6-Hexanetrionitrile has stronger adsorption and film-forming capabilities. It has three cyano groups, resulting in more adsorption sites on electrodes (especially the positive electrode) and aluminum foil surfaces, stronger bonding, and the formation of a denser and more stable protective layer.
[0070] In a preferred embodiment, the adiponitrile in the electrolyte has a mass percentage of C%, and C% is 1% to 5%.
[0071] If the mass percentage of adiponitrile in the electrolyte is too low, it cannot effectively complex transition metal ions and improve the high-temperature performance of the battery.
[0072] If the mass percentage of adiponitrile in the electrolyte is too high, excessive addition will significantly increase the electrolyte viscosity, reduce conductivity, and affect rate performance. Furthermore, excessive addition may also lead to over-reduction at the negative electrode, increasing impedance.
[0073] Wherein, C can be 1, 2, 3, 5, or any value within the above-mentioned range, and this application does not limit it.
[0074] In a preferred embodiment, the mass percentage of 1,3,6-hexanetrionitrile in the electrolyte is D%, and D% is 0.5% to 3%.
[0075] If the mass percentage of 1,3,6-hexanetrionitrile in the electrolyte is too low, it cannot effectively complex transition metal ions and improve the high-temperature performance of the battery.
[0076] If the mass percentage of 1,3,6-hexanetrionitrile in the electrolyte is too high, excessive addition will significantly increase the electrolyte viscosity and impedance, reduce conductivity, and affect rate performance.
[0077] Wherein, D can be 0.5, 1, 2, 3, or any value within the above-mentioned range, and this application does not limit it in this regard.
[0078] In some embodiments, the electrolyte further includes a lithium salt.
[0079] Lithium salts are existing technology and are not limited in this application. For example, the lithium salt can be at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium perchlorate, lithium difluorophosphate, lithium bis(oxalate)borate, lithium difluorooxalateborate, lithium tetrafluoroborate, and lithium difluorodi(oxalate)borate.
[0080] In some embodiments, the electrolyte further includes a solvent, which includes at least one selected from ethylene carbonate, propylene carbonate, butene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl propyl carbonate, diphenyl carbonate, methyl acetate, methyl propionate, methyl butyrate, ethyl acetate, propyl acetate, ethyl butyrate, propyl propionate, γ-butyrolactone, 1,3-dioxolane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.
[0081] It should be noted that this application does not impose any particular limitation on the preparation method of the electrolyte. Those skilled in the art can prepare the electrolyte using conventional technical means, such as mixing the raw materials evenly according to the specified ratio.
[0082] As an optional embodiment, the positive electrode active material includes a transition metal lithium oxide with the chemical formula Li. （1+x） Ni y Co z M （1-y-z） O2, where -0.1≤x≤1; 0≤y≤1, 0≤z≤1, and 0≤y+z≤1; where M is selected from one or more of Mg, Zn, Ga, Ba, Al, Fe, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo, and Zr.
[0083] In this application, there is no particular limitation on the type of positive electrode current collector; it can be any known material suitable for use as a positive electrode current collector. In one embodiment, the positive electrode current collector includes metallic materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum, as well as carbon materials such as carbon cloth and carbon paper. In one embodiment, the positive electrode current collector is a metallic material.
[0084] In some embodiments, the positive electrode active material layer further includes a positive electrode conductive agent, a positive electrode binder, and a solvent.
[0085] In some embodiments, the type of positive conductive agent mentioned in the present application is not limited, and any known conductive agent can be used.
[0086] In some embodiments, the positive electrode conductive agent mentioned in the embodiments of this application includes at least one of carbon materials such as natural graphite, artificial graphite, acetylene black, needle coke, carbon nanotubes, and graphene.
[0087] In one embodiment, there is no limitation on the type of positive electrode binder mentioned in the embodiments of this application, and any known positive electrode binder can be used.
[0088] In some embodiments, the positive electrode binder includes at least one of polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, and nitrocellulose.
[0089] As an optional embodiment, the negative electrode active layer includes a negative electrode active material, which includes artificial graphite and / or silicon-carbon composite materials.
[0090] In the embodiments of this application, there are no particular restrictions on the negative electrode current collector, as long as it can achieve the purpose of this application, such as copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, or composite current collector, etc.
[0091] In some preferred embodiments, the negative current collector comprises copper foil.
[0092] In some embodiments, the negative electrode active layer may further include a negative electrode conductive agent, a negative electrode binder, a thickener, and a solvent.
[0093] The negative electrode conductive agent includes at least one of the following carbon materials: natural graphite, artificial graphite, acetylene black, needle coke, carbon nanotubes, and graphene. The negative electrode binder includes styrene-butadiene latex, and the thickener includes CMC. The solvent includes deionized water.
[0094] In the lithium-ion batteries mentioned in this application, a separator is typically provided between the positive and negative electrodes to prevent short circuits. There are no particular restrictions on the material and shape of the separator, as long as it does not significantly impair the effectiveness of this application.
[0095] In some embodiments, the diaphragm includes a porous sheet-like or non-woven material with excellent liquid retention properties. The diaphragm includes resin or glass fiber diaphragm materials, including but not limited to polyolefins, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, etc.
[0096] In some embodiments, the lithium-ion battery may include an outer packaging that can be used to encapsulate the electrode assembly and electrolyte described above.
[0097] In some implementations, the outer packaging of a lithium-ion battery can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of a lithium-ion battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.
[0098] This application does not impose any particular restrictions on the shape of the lithium-ion battery; it can be cylindrical, square, or any other arbitrary shape.
[0099] On the other hand, one embodiment of this application provides an electrical device including the lithium-ion battery described above.
[0100] For example, the aforementioned electrical devices may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as 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 are not limited thereto.
[0101] To further understand the present invention, the following embodiments are provided to illustrate the present application. These embodiments are for illustrative purposes only and are not intended to limit the scope of the present application.
[0102] Example 1
[0103] I. Preparation of Lithium-ion Batteries
[0104] 1. Preparation of negative electrode sheet: The negative electrode active material artificial graphite, conductive agent Super P, and negative electrode binder sodium carboxymethyl cellulose are mixed in a mass ratio of 96:1.5:2.5, and deionized water is added and stirred evenly to obtain a negative electrode slurry with a solid content of 40wt%. The negative electrode slurry is uniformly coated on one surface of the negative electrode current collector copper foil, and then dried at 110℃. The above steps are repeated on the other surface of the negative electrode current collector, and the negative electrode sheet is obtained by cold pressing.
[0105] 2. Preparation of the positive electrode sheet: The positive electrode active material (spinel lithium nickel manganese oxide), conductive agent (acetylene black), and binder (polyvinylidene fluoride) are mixed at a mass ratio of 96:2:2. N-methylpyrrolidone is added as a solvent, and the mixture is stirred under vacuum until a homogeneous positive electrode slurry is formed. The positive electrode slurry is uniformly coated onto the positive electrode current collector aluminum foil and dried at 85°C. The above steps are repeated on the other surface of the positive electrode current collector, and the mixture is cold-pressed to obtain the positive electrode sheet.
[0106] 3. Electrolyte Preparation: In an argon-atmospheric glove box with a water content <10ppm, ethylene carbonate, propylene carbonate, and propyl propionate (PP) were mixed evenly to obtain the base solvent. Thoroughly dried lithium salt LiPF6 and 1,3-propanesulfonate lactone were dissolved in the base solvent and mixed evenly to obtain the electrolyte. The lithium salt LiPF6 had a mass percentage of 12.5%, the solvent ratio EC:PC:PP = 2:1:7, and the 1,3-propanesulfonate lactone had a mass percentage of 4%.
[0107] 4. Lithium-ion battery fabrication: The above-mentioned positive electrode sheet, separator, and negative electrode sheet are wound to obtain a bare cell. The bare cell is placed in a pre-punched aluminum-plastic film to complete the top and side sealing. After high-temperature baking, electrolyte injection, settling, formation, capacity testing, and other processes, the battery manufacturing is completed.
[0108] Examples 2-17 and Comparative Examples 1-13
[0109] The basic content of Examples 2-17 and Comparative Examples 1-13 is the same as that of Example 1, and the differences are shown in Table 1.
[0110] II. Performance Testing
[0111] 1. Cyclic capacity retention test
[0112] The lithium-ion batteries of each embodiment and comparative example were placed in a 45°C constant temperature test chamber and left to stand for 30 minutes to allow them to reach a constant temperature. The lithium-ion batteries that had reached a constant temperature were then charged at a constant current of 0.5C to a voltage of 4.8V, then charged at a constant voltage of 4.8V until the current was less than or equal to 0.05C, and then discharged at a constant current of 0.5C to a voltage of 3.0V. This constitutes one charge-discharge cycle, and the discharge capacity obtained at this point is recorded as the initial discharge capacity C0. Using the initial discharge capacity as 100%, the charge-discharge cycles were repeated. After 500 cycles, the test was stopped, and the discharge capacity of the lithium-ion battery at this point was recorded as the discharge capacity after 500 cycles, C1. The 45°C charging capacity retention rate was obtained as C1 / C0. The test results are shown in Table 1.
[0113] Table 1. Formulas, Relationships, and Test Results
[0114]
[0115] Referring to Table 1, and comparing Examples 1 to 31, as well as Comparative Examples 1 and 3, it can be seen that when the B / A ratio is too low (i.e., many positive electrode defects (large A value) and the additive content is too low (small B value), the additives are insufficient to "repair" all highly active defect points, resulting in an incomplete CEI film. When the B / A ratio is too high (i.e., few positive electrode defects (small A value) and the additive content is too high (large B value), the formed CEI film is too thick, increasing the resistance to lithium-ion migration, leading to increased battery internal resistance, and affecting rate performance and capacity. When 0.7 ≤ B / A ≤ 5 is satisfied, a uniform and complete CEI film can be formed, improving the cycle stability of the battery. Further comparison of Examples 6 to 9 shows that when 0.85 ≤ B / A ≤ 4.5 is further satisfied, the cycle stability of the battery can be further improved.
[0116] By comparing Examples 1 to 3, and Comparative Examples 1 and 2, it can be seen that if the value of A is too large, it indicates abnormal lithium-ion occupancy or disordered distribution of transition metal ions, which will lead to the lithium-ion insertion / extraction channels being blocked by transition metal ions, reducing the ion diffusion coefficient, and increasing lattice stress during cycling, easily causing structural distortion. If the value of A is too small, it indicates reduced lithium-ion order and increased defects, which will lead to intensified interface reactions and deterioration of battery cycle performance. When 1 ≤ A ≤ 3, the cycle stability of the battery can be improved.
[0117] By comparing Examples 2, 10 and 11, it can be seen that when the sulfonate compound is selected from the compounds provided in the embodiments of this application, the cycle stability of the battery can be improved.
[0118] By comparing Examples 2, 4, and 5, as well as Comparative Examples 3 and 4, it can be seen that if the B value is too low, the film formation effect will be limited, which is not conducive to long-term cycling; if the B value is too high, it will increase the film formation resistance of the positive electrode, leading to lithium plating. When 2≤B≤6 is satisfied, the cycle stability of the battery can be improved.
[0119] By comparing Examples 14 to 17, and Comparative Examples 5 and 6, it can be seen that if N is too low, it is insufficient to maintain long-term cycling; if N is too high, insufficient oxidation resistance may lead to deterioration in gas production. When 2 ≤ N ≤ 10, the cycle stability of the battery can be improved.
[0120] By comparing Examples 3 to 7, Examples 16 and 17, and Examples 1 and 2, and Examples 8 to 15, it can be seen that if (B+N) / A is too low, it indicates that the amount of sulfonate compound and fluorine-containing compound is too low, which cannot guarantee the formation of a sufficiently thick and complete composite interface film on the positive and negative electrode surfaces, leading to deterioration of battery cycle performance. If (B+N) / A is too high, it indicates that the amount of sulfonate compound and fluorine-containing compound is too high, which will form an excessively thick composite interface film, hindering lithium-ion transport and leading to lithium plating. When 2 ≤ (B+N) / A ≤ 10, the cycle stability of the battery can be improved.
[0121] Comparative Examples 2 and 9 to 13 demonstrate that when the positive electrode active material comprises spinel lithium nickel manganese oxide, the cycle stability of the battery can be improved. Although this application has been described with reference to preferred embodiments, those skilled in the art will understand that various changes can be made and equivalents can be substituted for elements therein, without departing from the scope of this application. Furthermore, many modifications can be made to adapt specific situations or materials to the teachings of this application, without departing from the essential scope of this application. Therefore, this application is not intended to be limited to the specific embodiments disclosed as the best mode for carrying out this application, but rather this application will include all embodiments falling within the scope of the appended claims.
[0122] All scopes disclosed in this application include endpoints, and endpoints can be combined with each other.
[0123] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.
Claims
1. A lithium-ion battery, characterized in that, The battery comprises a positive electrode, a negative electrode, and an electrolyte. The positive electrode includes a positive current collector and a positive active material layer disposed on at least one side of the positive current collector. The positive active material layer includes a positive active material, which is spinel lithium nickel manganese oxide. The ratio of the intensity of the ordered crystal peak to the intensity of the disordered crystal peak in the X-ray diffraction pattern of the positive active material is A. The intensity of the ordered crystal peak in the X-ray diffraction pattern of the positive active material is the intensity of the crystal peak on the (111) plane, and the intensity of the disordered crystal peak is the intensity of the crystal peak on the (311) plane. The electrolyte includes an additive, which includes a sulfonate compound. The sulfonate compound has a mass percentage of B% in the electrolyte. The lithium-ion battery satisfies the following conditions: 2≤B / A≤5, 1≤A≤2, 4≤B≤4.
5. The sulfonate compound includes at least one compound selected from structural formula I and structural formula II. R11 is selected from one of substituted or unsubstituted C1 to C4 alkylene groups, substituted or unsubstituted C2 to C4 alkenyl groups, and substituted or unsubstituted C1 to C6 chain heteroalkylene groups, wherein the chain heteroalkylene group has 1 to 5 heteroatoms, and the heteroatoms in the chain heteroalkylene group are selected from at least one of O, N, P or S. R21 and R22 are each independently selected from one of a halogen atom, a cyano group, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C2 to C10 alkenyl group, or a substituted or unsubstituted C2 to C10 alkynyl group; the sulfonate compound is selected from at least one of 1,3-propanesulfonate lactone, mannitol carbonate sulfate, and 4-methyl ethyl sulfate. The additive also includes a fluorinated compound, wherein the mass percentage of the fluorinated compound in the electrolyte is N%, 2≤N≤10; 2≤(B+N) / A≤10.
2. The lithium-ion battery according to claim 1, characterized in that, The fluorinated compound is selected from at least one of fluoroethylene carbonate, trifluoroethyl methyl carbonate, difluoroacetamide, fluorocarbamate, fluorotetramethylene sulfone, triethyl fluorophosphate, 2,2,2-trifluoroethyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, ethyl 2,2-difluoroacetate, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, fluorobenzene, fluoroacetonitrile, and fluoroadiponitrile.
3. The lithium-ion battery according to claim 1, characterized in that, The additives also include nitrile compounds.
4. The lithium-ion battery according to claim 3, characterized in that, The nitrile compound is selected from dinitrile and / or 1,3,6-hexanetrinitrile.
5. The lithium-ion battery according to claim 4, characterized in that, The adiponitrile in the electrolyte is 1% to 5% by mass; and / or, the 1,3,6-hexanetrionitrile in the electrolyte is 0.5% to 3% by mass.