Battery and electronic device

Abstract

The application relates to a battery and an electronic device, the battery comprising a positive electrode sheet, a negative electrode sheet and an electrolyte; the positive electrode sheet comprising a positive electrode current collector and a positive electrode coating arranged on at least one side surface of the positive electrode current collector; the positive electrode coating comprising a positive electrode active material; the positive electrode active material comprising a layered oxide material and a lithium-rich compound; the negative electrode sheet comprising a negative electrode current collector and a negative electrode coating arranged on at least one side surface of the negative electrode current collector; the negative electrode coating comprising a negative electrode active material, and the negative electrode active material comprising a silicon-carbon material; the battery satisfying the following relationship: a / b >= 1.5; 3 <= c / d <= 8. The scheme provided in the application can make the battery have excellent energy density, cycle performance and storage performance.

Description

Technical Field

[0001] This application relates to the field of battery technology, and more particularly to batteries and electronic devices. Background Technology

[0002] With the acceleration of global electrification and intelligentization, end customers' demand for lithium-ion battery energy density is showing an unprecedented and urgent growth. This trend is profoundly reshaping the landscape of major applications, from consumer electronics to electric vehicles and even the low-altitude economy.

[0003] In the electric vehicle sector, consumers are pushing automakers to continuously push the limits of driving range, demanding that batteries store more energy within limited chassis space in exchange for longer driving range and better overall vehicle energy efficiency. At the same time, the increasing thinness and integration of functions in smartphones and wearable devices have led to extreme compression of internal space, forcing batteries to deliver stronger and longer-lasting power in a tiny volume. This comprehensive and multi-dimensional demand upgrade has established improving energy density as an irreversible core driving force in the current iteration of battery technology. Summary of the Invention

[0004] To address or partially address the problems existing in related technologies, this application provides a battery and electronic device that exhibits excellent energy density, cycle performance, and storage performance.

[0005] The first aspect of this application provides a battery, wherein the battery includes a positive electrode, a negative electrode, and an electrolyte; The positive electrode sheet includes a positive current collector and a positive electrode coating disposed on at least one surface of the positive current collector; the positive electrode coating includes a positive electrode active material; the positive electrode active material includes a layered oxide material and a lithium-rich compound; The negative electrode sheet includes a negative electrode current collector and a negative electrode coating disposed on at least one side surface of the negative electrode current collector; the negative electrode coating includes a negative electrode active material, and the negative electrode active material includes a silicon-carbon material; The battery satisfies the following relationship: a / b ≥ 1.5; 3≤c / d≤8; Wherein, the mass fraction of the silicon-carbon material in the negative electrode active material is a%; the mass fraction of the lithium-rich compound in the positive electrode active material is b%; the median particle size Dv50 of the layered oxide material is c μm; and the median particle size Dv50 of the lithium-rich compound is d μm.

[0006] The battery as described in the first aspect, wherein 0 < a ≤ 50; And / or, 0 < b ≤ 10; And / or, 10≤c≤20; And / or, 1≤d≤8.

[0007] The battery as described in the first aspect, wherein the electrolyte comprises fluoroethylene carbonate, ethylene sulfate and nitrile compounds; The mass fraction of the fluoroethylene carbonate in the electrolyte is A; the mass fraction of the ethylene sulfate in the electrolyte is B; and the mass fraction of the nitrile compound in the electrolyte is C. Where 1≤A≤4; 0.5≤B≤4; 0.5≤C≤4.

[0008] The battery as described in the first aspect, wherein the battery satisfies the following relationship: 0.5≤A / k≤2; The specific surface area of ​​the silicon-carbon material is km². 2 / g.

[0009] The battery as described in the first aspect, wherein the battery satisfies the following relationship: 1≤(B+C) / b≤3.

[0010] The battery as described in the first aspect, wherein k ≤ 3.

[0011] The battery as described in the first aspect, wherein the nitrile compound includes oxonium and / or succinic anionyl nitrile.

[0012] The battery as described in the first aspect, wherein the median particle size Dv50 of the silicon-carbon material is 5 μm to 12 μm; And / or, the mass fraction of silicon in the silicon-carbon material is 30% to 70%.

[0013] The battery as described in the first aspect, wherein the layered oxide material comprises lithium cobalt oxide and / or nickel cobalt manganese oxide; And / or, the lithium-rich compound has the chemical formula Li2XO3, wherein X is at least one of Mn, Ni, Co, and Fe.

[0014] A second aspect of this application provides an electronic device comprising a battery as described in the first aspect.

[0015] The technical solution provided in this application can include the following beneficial effects: by synergistically introducing layered oxide materials, lithium-rich compounds, and silicon-carbon materials into the positive and negative electrodes, and precisely controlling the mass ratio of silicon-carbon materials to lithium-rich compounds and the particle size distribution of layered oxide materials and lithium-rich compounds, the energy density of the battery can be effectively improved. On the one hand, adding lithium-rich compounds can compensate for the loss of active lithium in the first cycle of the negative electrode, significantly improving the coulombic efficiency and energy density in the first cycle. At the same time, the appropriate mass ratio of silicon-carbon materials to lithium-rich compounds avoids the risk of lithium plating in the negative electrode and capacity decay in the later stages of cycling due to excessive lithium replenishment. On the other hand, by optimizing the particle size matching of layered oxide materials and lithium-rich compounds, the problem of the deterioration of the compaction density of the positive electrode due to large particle size differences, which in turn offsets the energy density gain, is solved. This ensures that the high compaction density of the positive electrode is maintained while efficiently replenishing lithium, thereby ultimately achieving an improvement in the energy density of the battery cell.

[0016] 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

[0017] To facilitate understanding of this application, it will be described in detail below. However, before describing this application in detail, it should be understood that this application is not limited to the specific embodiments described. It should also be understood that the terminology used herein is for the purpose of describing specific embodiments only and is not intended to be restrictive.

[0018] Where a numerical range is provided, it should be understood that every intermediate value between the upper and lower limits of the range and any other specified or intermediate value within the specified range is covered within this application. The upper and lower limits of these smaller ranges may be independently included in the smaller range and are also covered within this application, subject to any explicitly excluded limits within the specified range. Where the specified range includes one or two limits, the range excluding any or both of those included limits is also included within this application.

[0019] Unless otherwise defined, all terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. While the methods and materials described herein, or any equivalent methods and materials, may also be used in the implementation or testing of this application, preferred methods and materials are now described.

[0020] In the electric vehicle sector, consumers are pushing automakers to continuously push the limits of driving range, demanding that batteries store more energy within limited chassis space in exchange for longer driving range and better overall vehicle energy efficiency. At the same time, the increasing thinness and integration of functions in smartphones and wearable devices have led to extreme compression of internal space, forcing batteries to deliver stronger and longer-lasting power in a tiny volume. This comprehensive and multi-dimensional demand upgrade has established improving energy density as an irreversible core driving force in the current iteration of battery technology.

[0021] To address the aforementioned issues, this application provides a battery comprising a positive electrode, a negative electrode, and an electrolyte; the positive electrode includes a positive current collector and a positive electrode coating disposed on at least one side of the positive current collector; the positive electrode coating includes a positive electrode active material; the positive electrode active material includes a layered oxide material and a lithium-rich compound; the negative electrode includes a negative current collector and a negative electrode coating disposed on at least one side of the negative current collector; the negative electrode coating includes a negative electrode active material, which includes a silicon-carbon material.

[0022] This application does not limit the choice of the positive current collector; for example, the positive current collector can be aluminum foil. The positive electrode sheet includes a positive current collector and a positive coating disposed on at least one surface of the positive current collector.

[0023] The positive electrode coating of this application includes a positive electrode active material, which comprises a layered oxide material and a lithium-rich compound. The layered oxide material typically has an α-NaFeO2-type layered structure, consisting of alternating layers of transition metal-oxygen octahedrons (such as those composed of nickel, cobalt, manganese, or aluminum) and lithium-oxygen octahedrons. During battery charging, an external electric field drives lithium ions to reversibly extract (de-intercalate) from the interlayer spaces of the layered oxide, while the transition metal ions undergo oxidation to compensate for the charge. During discharging, lithium ions are reinserted into the interlayer spaces, and the transition metal ions are reduced, thereby ensuring the electrochemical performance of the battery.

[0024] Cathode lithium replenishment agents include lithium-rich compounds, which are compounds with a high lithium content. Adding lithium-rich compounds to the cathode active material layer allows them to release active lithium, compensating for lithium consumed during SEI film formation and other processes, thus improving the battery's initial coulombic efficiency and consequently increasing its energy density.

[0025] This application does not limit the choice of negative electrode current collector; it can be selected according to actual needs, such as copper foil. The negative electrode coating of this application includes a negative electrode active material, which includes silicon-carbon material. The silicon-carbon material of this application is a lithium-ion battery negative electrode material formed by combining high-capacity silicon and high-stability carbon through nanocomposite technology. It utilizes the extremely high theoretical specific capacity of silicon as the main lithium storage medium, while leveraging the excellent conductivity and mechanical strength of the carbon matrix to buffer the volume expansion of silicon, thereby effectively preventing electrode pulverization and repeated rupture of the interface film.

[0026] The battery in this application satisfies the following relationship: a / b ≥ 1.5; 3≤c / d≤8; Among them, the mass fraction of silicon-carbon material in the negative electrode active material is a; the mass fraction of lithium-rich compound in the positive electrode active material is b; the median particle size Dv50 of layered oxide material is c μm; and the median particle size Dv50 of lithium-rich compound is d μm.

[0027] For example, a / b can be 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, etc.; for example, c / d can be 3, 4, 5, 6, 7, 8, etc.

[0028] This application achieves a significant improvement in battery energy density by synergistically introducing layered oxide materials, lithium-rich compounds, and silicon-carbon materials into the positive and negative electrodes, and precisely controlling the mass ratio of silicon-carbon materials to lithium-rich compounds and the particle size distribution of layered oxide materials and lithium-rich compounds. On the one hand, the addition of lithium-rich compounds can compensate for the loss of active lithium in the first cycle of the negative electrode, significantly improving the coulombic efficiency and energy density in the first cycle. At the same time, the appropriate mass ratio of silicon-carbon materials to lithium-rich compounds avoids the risk of lithium plating in the negative electrode and capacity decay in the later stages of cycling due to excessive lithium replenishment. On the other hand, by optimizing the particle size matching of layered oxide materials and lithium-rich compounds, the problem of deterioration of the compaction density of the positive electrode due to large particle size differences, which in turn offsets the energy density gain, is solved. This ensures that the high compaction density of the positive electrode is maintained while efficiently replenishing lithium, thereby ultimately achieving an improvement in the cell energy density.

[0029] In one specific embodiment, the negative electrode active material further includes graphite. This application utilizes the excellent structural stability and mature lithium intercalation mechanism of graphite to construct a stable conductive framework, thereby buffering the volume expansion stress of silicon-carbon materials, effectively maintaining the overall mechanical integrity of the electrode, and preventing electrode pulverization and contact failure caused by the drastic expansion of silicon; at the same time, graphite provides reversible lithium-ion intercalation sites, achieving a balance between energy density and cycle stability.

[0030] In one specific implementation, 0 < a ≤ 50, for example, a can be 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, etc. When the mass fraction of silicon-carbon material is within the above range, the high theoretical capacity of silicon-carbon material can be used to significantly improve the overall specific capacity of the negative electrode, and the buffering effect of graphite can be used to effectively accommodate the volume expansion of silicon during charging and discharging, preventing particle pulverization and conductive network breakage. If the mass fraction is too low, the high capacity advantage of silicon-carbon material cannot be reflected, and the energy density improvement is negligible. If the mass fraction is too high, the huge volume expansion stress will exceed the tolerance limit of graphite and binder, leading to repeated rupture and regeneration of the SEI film, severe consumption of active lithium, and collapse of the electrode structure, resulting in a sharp drop in first-cycle efficiency and a sharp decline in cycle life.

[0031] In one specific implementation, 0 < b ≤ 10, for example, b can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, etc. When the mass fraction of the lithium-rich compound is within the above range, within this range, the lithium-rich compound undergoes an irreversible delithiation reaction during the first charge. The amount of active lithium ions released is just enough to fill the lithium deficit consumed by the silicon-carbon anode due to the formation of the solid electrolyte interphase (SEI) film and volume expansion and rupture, thereby significantly improving the first-cycle coulombic efficiency and overall energy density of the battery. If the amount added is too low, the released lithium is insufficient to fully compensate for the anode loss, resulting in an insignificant improvement in the first-cycle efficiency and the inability to fully utilize the advantages of high-capacity silicon. If the amount added is too high, the excess lithium ions released cannot be effectively inserted into the anode and will precipitate on the anode surface to form metallic lithium dendrites, which are very likely to pierce the separator and cause a short circuit and explosion. At the same time, the excess active lithium will continue to react with the electrolyte, resulting in gas production, a surge in internal resistance, and a sharp decline in cycle life.

[0032] In one specific embodiment, 10 ≤ c ≤ 20, for example, c can be 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, etc. When the median particle size of the layered oxide material is within the above range, it can effectively ensure the leveling and coating uniformity of the positive electrode slurry, avoiding coating defects caused by excessively coarse particles or agglomeration and high viscosity problems caused by excessively fine particles. At the same time, this particle size is conducive to optimizing the packing density of secondary spherical particles. While ensuring high volumetric energy density, it promotes electrolyte wetting through reasonable pore structure and effectively alleviates volume expansion stress during charging and discharging, thereby improving the cycle stability of the battery while maintaining high capacity output.

[0033] In one specific embodiment, 1 ≤ d ≤ 8, for example, d can be 1, 2, 3, 4, 5, 6, 7, 8, etc. This particle size range can effectively shorten the solid-phase diffusion path of lithium ions within the crystal lattice, resulting in higher mechanical strength and fewer grain boundary defects. It can effectively suppress particle breakage and microcrack generation caused by anisotropic volume expansion during fast charging or long cycling, thereby blocking the electrolyte from eroding the interior of the material and improving the energy density and cycle performance of the battery.

[0034] In one specific embodiment, the electrolyte includes fluoroethylene carbonate (FEC), ethylene sulfate (DTD), and nitrile compounds.

[0035] Fluorinated ethylene carbonate can preferentially undergo reduction and decomposition on the negative electrode surface compared to conventional solvents, constructing a dense solid electrolyte interphase (SEI) film rich in inorganic lithium fluoride (LiF) and possessing both high mechanical strength and excellent flexibility. This protective film can effectively adapt to the severe volume expansion and contraction stress of silicon-carbon materials during charging and discharging, significantly suppressing the repeated rupture and regeneration of the protective film caused by particle deformation, thereby blocking the vicious cycle of continuous decomposition of the electrolyte consuming active lithium, greatly reducing irreversible capacity loss, and ultimately achieving an improvement in the battery's first-cycle coulombic efficiency and energy density, as well as enhanced long-cycle stability.

[0036] Ethylene sulfate (DTD), as a highly efficient bifunctional electrolyte additive, can preferentially decompose compared to conventional solvents during the first charge and discharge of a battery, simultaneously constructing a dense protective film rich in highly stable components such as inorganic lithium sulfate on the surfaces of both the positive and negative electrodes. On the negative electrode side, this film effectively buffers the volume expansion stress of silicon-carbon materials due to its excellent mechanical strength, preventing continuous electrolyte consumption caused by repeated interface rupture. On the positive electrode side, it can significantly suppress the dissolution of transition metal ions under high voltage and the side reactions between lithium-rich compounds and the electrolyte. This not only greatly reduces the impedance of interfacial side reactions but also improves the chemical and mechanical stability of the electrode / electrolyte interface, thereby significantly extending the cycle life and storage performance of the battery.

[0037] Nitrile compounds, with their highly polar cyano (-CN) functional groups in their molecular structure, exhibit excellent interfacial adsorption and film-forming properties. They can undergo electrochemical polymerization or decomposition reactions on the surface of lithium-rich compounds and layered oxide materials, constructing a dense, uniform, and chemically stable passivation protective film in situ. This functional interfacial film not only effectively blocks the violent side reactions between highly active lithium-rich compounds and electrolyte solvents, preventing the ineffective consumption of lithium sources during storage and initial cycling, but also significantly inhibits the dissolution of transition metal ions and the oxidative decomposition of electrolytes in layered oxide materials under high-voltage operating conditions. This greatly reduces interfacial impedance and improves the structural integrity of electrode materials and the overall electrochemical stability of the battery.

[0038] In one specific embodiment, 1 ≤ A ≤ 4, and the mass fraction of fluoroethylene carbonate in the electrolyte is A%, for example, A can be 1, 1.5, 2, 2.5, 3, 3.5, 4, etc. When A is within the above range, it can ensure that a dense, uniform, and highly flexible composite protective film is preferentially formed during the first charge-discharge cycle. This film can adapt to the huge volume changes of silicon-carbon materials to maintain structural integrity, and can also reduce the irreversible loss of active lithium. Thus, while ensuring high first-cycle coulombic efficiency and energy density, it significantly improves the capacity retention rate and safety performance of the battery during long-cycle operation.

[0039] In one specific embodiment, 0.5 ≤ B ≤ 4, for example, B can be 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, etc. When the mass fraction of vinyl sulfate is within the above range, vinyl sulfate can fully decompose to construct a protective layer with high ionic conductivity, strong chemical stability, and excellent flexibility, thereby significantly improving the cycle life and safety performance of the battery.

[0040] In one specific embodiment, 0.5 ≤ C ≤ 4, for example, C can be 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, etc. When the mass fraction of nitrile compounds is within the above range, a dense, flexible, and oxidation-resistant positive electrode electrolyte interface film can be formed, effectively suppressing electrolyte decomposition and gas generation, transition metal dissolution, and lithium-rich compound decomposition. At the same time, it can avoid the increase in impedance caused by excessive interface film thickness due to excessive nitrile compounds, thereby further improving the cycle performance and storage performance of the battery.

[0041] In one specific implementation, the battery satisfies the following relationship: 0.5≤A / k≤2; Among them, the specific surface area of ​​silicon-carbon materials is km². 2 / g.

[0042] For example, A / k can be 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, etc.

[0043] This application constructs a dynamic synergistic matching mechanism between the mass fraction of fluoroethylene carbonate and the specific surface area of ​​silicon-carbon materials. The principle is based on the fact that the large specific surface area of ​​the silicon-carbon anode directly determines the number of active sites for interfacial side reactions and the amount of lithium source consumed for film formation. As the specific surface area of ​​silicon-carbon materials increases, the electrode / electrolyte interface expands significantly, leading to intensified electrolyte decomposition and increased irreversible lithium loss during the initial formation of the solid electrolyte interphase (SEI) film. If a fixed amount of fluoroethylene carbonate is maintained, the film-forming agent will be insufficient to cover all active surfaces, resulting in a porous and weak SEI film with insufficient mechanical strength. This fails to effectively suppress film rupture caused by the volume expansion of silicon-carbon materials in subsequent cycles, as well as the gas generation from electrolyte decomposition. Therefore, when A / k is within the above range, it ensures that sufficient fluoroethylene carbonate molecules are preferentially reduced and decomposed per unit specific surface area, generating a dense and uniform composite protective film rich in lithium fluoride. This not only improves the first-cycle coulombic efficiency and energy density of the battery but also significantly enhances the cycle performance and storage performance of the cell.

[0044] In one specific implementation, the battery satisfies the following relationship: 1≤(B+C) / b≤3.

[0045] For example, (B+C) / b can be 1, 1.2, 1.4, 1.6, 1.8, 2, 2.2, 2.4, 2.6, 2.8, 3, etc.

[0046] As the particle size of lithium-rich compounds decreases, their specific surface area increases exponentially, leading to a significant increase in surface active sites. This makes them highly susceptible to electrolyte oxidation and decomposition, as well as transition metal dissolution. If the concentrations of vinyl sulfate and nitrile compounds are kept constant, the number of vinyl sulfate and nitrile molecules distributed per unit area will be insufficient to form a continuous and dense positive electrode electrolyte interface film. However, by controlling the ratio of the mass fraction of vinyl sulfate and nitrile compounds to the particle size of the lithium-rich compounds within the aforementioned range, sufficient additive molecules can still be adsorbed on the surface of the tiny particles. The inorganic lithium sulfate component generated from the decomposition of vinyl sulfate fills grain boundary defects, and together with the flexible organic network formed by the polymerization of nitrile compounds, a composite protective film with high ionic conductivity, excellent mechanical strength, and strong oxidation resistance is constructed. This film not only effectively suppresses gas-generating side reactions and lattice oxygen release under high voltage but also buffers lattice stress during charge and discharge, thereby significantly improving the battery's long-cycle stability and storage performance.

[0047] In one specific implementation, k ≤ 3, for example, k can be 0.5, 1, 1.5, 2, 2.5, 3, etc. When k is within the above range, it can provide sufficient ion transport channels and buffer space to accommodate the volume changes of silicon-carbon materials, and control interfacial side reactions within an acceptable range. Combined with an appropriate amount of film-forming additives, a stable and dense SEI film is formed, reducing the decomposition and gas generation of the electrolyte, thereby achieving a synergistic improvement in high initial efficiency, long cycle life, and high storage performance.

[0048] In one specific embodiment, the nitrile compound includes oxonium (SN) and / or butadionitrile (ADN). The cyano group in these nitrile compounds exhibits extremely high oxidation stability, significantly enhancing the electrolyte's oxidation resistance at the positive electrode interface and inhibiting solvent decomposition. Simultaneously, these dinitrile molecules can form a dense, flexible, and highly ionicly conductive interfacial film rich in polycyanides and inorganic lithium salts, thereby preventing ineffective lithium source consumption, suppressing the dissolution of transition metal ions and lattice oxygen release under high voltage, and ultimately improving the battery's interfacial stability and safety performance.

[0049] In one specific embodiment, the median particle size Dv50 of the silicon-carbon material is 5μm to 12μm. For example, the median particle size Dv50 of the silicon-carbon material can be 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, etc. Controlling the particle size of the silicon-carbon material within the above range can ensure that the negative electrode slurry has good rheological properties and the negative electrode sheet has a high compaction density. It can also ensure that the silicon-carbon particles, under the protection of graphite and elastic binder, effectively buffer the volume changes during cycling, maintain the integrity of the electrode structure and the continuity of the conductive path, thereby achieving synergistic optimization of high energy density and long cycle life.

[0050] In one specific embodiment, the mass fraction of silicon in the silicon-carbon material is 30% to 70%, for example, the mass fraction of silicon can be 30%, 40%, 50%, 60%, 70%, etc. When the mass fraction of silicon is within the above range, the silicon-carbon material can achieve high capacity while having a small volume change, thereby better maintaining the structural integrity and interface stability of the negative electrode, achieving a balance between high energy density and long cycle life.

[0051] In one specific embodiment, the layered oxide material includes lithium cobalt oxide and / or nickel-cobalt-manganese oxide. This layered oxide material ensures rapid lithium-ion insertion / extraction while maintaining high structural integrity, thereby enabling the battery to exhibit high energy density and excellent cycle and storage performance.

[0052] In one specific embodiment, the lithium-rich compound has the chemical formula Li₂XO₃, wherein X is at least one of Mn, Ni, Co, and Fe. This lithium-rich compound can efficiently release lithium during charge and discharge, replenishing the battery's irreversible lithium loss, improving the battery's initial coulombic efficiency and energy density, and reducing side reactions between the lithium-rich compound and the electrolyte, thus ensuring the battery's cycle performance and storage performance.

[0053] In one specific embodiment, the positive electrode coating further includes a positive electrode conductive agent and a positive electrode binder. The positive electrode conductive agent includes at least one of carbon materials such as natural graphite, artificial graphite, acetylene black, needle coke, carbon nanotubes, graphene, and vapor-grown carbon fiber (VGCF). The positive electrode binder includes at least one of polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, nitrocellulose, polyvinylidene fluoride, and polytetrafluoroethylene.

[0054] In one specific embodiment, the negative electrode coating of this application further includes a negative electrode conductive agent and a negative electrode binder. Both the negative electrode conductive agent and the negative electrode binder of this application can be selected from conventional materials in the art.

[0055] In one specific embodiment, the electrolyte of this application further includes an organic solvent and an electrolyte lithium salt. This application does not limit the selection of organic solvent and electrolyte lithium salt, and can select them according to actual needs, as long as they can fully dissolve the electrolyte lithium salt, fluoroethylene carbonate, ethylene sulfate and nitrile compounds and have high stability.

[0056] In one specific embodiment, the lithium-ion battery further includes a separator. The embodiments of this application do not have any particular restrictions on the material and shape of the separator, as long as it does not significantly impair the effect of this application. It may include porous sheet-like or non-woven fabric-like materials with excellent liquid retention. The materials of the resin or glass fiber separator include, but are not limited to, polyolefins, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, etc., and can be set according to needs.

[0057] In one embodiment, the battery may include an outer packaging that can be used to encapsulate the electrode assembly and electrolyte.

[0058] In one specific embodiment, the outer packaging of the battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch-type soft pack. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0059] This application does not impose any particular restrictions on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape.

[0060] A second aspect of this application provides an electronic device including the aforementioned battery. This electronic device has advantages corresponding to the aforementioned battery, which will not be elaborated further.

[0061] The application fields of the electronic devices in this application embodiment are not particularly limited, and they can be used in consumer electronics products, new energy vehicles, and energy storage, among other fields. For example, the aforementioned electronic 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., without any particular limitation.

[0062] The present application will be further described in detail below through specific embodiments.

[0063] Example 1-1 1. Preparation of negative electrode sheet A negative electrode active material (graphite, silicon carbide), dispersant (CMC), binder (SBR), and conductive agent (SP) were mixed in a ratio of 94:1:4:1. Water was then added to adjust the solid content to 48%, and the mixture was stirred in a vacuum mixer to obtain a negative electrode slurry. The negative electrode slurry was uniformly coated onto one surface of a 10 μm thick copper foil current collector. The copper foil was dried at 85°C to obtain a single-sided negative electrode sheet with a 63 μm thick coating. The above steps were repeated on the other surface of the aluminum foil to obtain a double-sided negative electrode sheet. After cold pressing, cutting, and slitting, the sheet was dried under vacuum at 120°C for 12 hours to obtain a negative electrode sheet with dimensions of 73 mm × 1072 mm.

[0064] Among them, the mass fraction (a%) of silicon-carbon material in the negative electrode active material is 5%; the median particle size (Dv50) of silicon-carbon material is 10 μm; and the specific surface area (k) of silicon-carbon material is 2 m². 2 / g; The mass fraction of silicon in silicon-carbon materials is 60%.

[0065] 2. Preparation of the positive electrode sheet The positive electrode active materials (lithium cobalt oxide and lithium iron ferrite (Li2FeO3)) were mixed with conductive agent carbon black and binder polyvinylidene fluoride at a mass ratio of 98:1:1. N-methylpyrrolidone (NMP) was added, and the mixture was stirred under vacuum until the system was homogeneous to obtain a positive electrode slurry. The solid content of the positive electrode slurry was 68%. The positive electrode slurry was uniformly coated onto one surface of a 10 μm thick aluminum foil for the positive electrode current collector. The aluminum foil was dried at 100°C to obtain a positive electrode sheet with a double-sided coating of positive electrode active material layer with a coating thickness of 62 μm. The above steps were repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided positive electrode coating. After cold pressing, cutting, and slitting, the sheet was dried under vacuum at 85°C for 4 hours to obtain a positive electrode sheet with a size of 71 mm × 1062 mm.

[0066] Among them, the mass fraction b% of lithium-rich compounds in the positive electrode active material is 1%; the median particle size Dv50(c) of lithium cobalt oxide is 15 μm, and the median particle size Dv50(d) of lithium ferrite is 3 μm.

[0067] 3. Preparation of electrolyte In an environment with a water content of less than 10 ppm, diethyl carbonate (DEC) and ethylene carbonate (EC) were mixed at a mass ratio of 2:1. Based on the total mass of the electrolyte, lithium hexafluorophosphate (LiPF6) was added to the solvent, dissolved, and mixed evenly. Then, fluoroethylene carbonate (FEC), vinyl sulfate, and a nitrile compound (butaniline) were added to obtain the electrolyte. The mass percentage of LiPF6 in the electrolyte was 12.5%, the mass percentage of fluoroethylene carbonate (A) was 4%, the mass percentage of vinyl sulfate (B) was 2%, and the mass percentage of the nitrile compound (C) was 1.5%.

[0068] 4. Manufacturing of lithium-ion batteries The positive and negative electrode sheets are stacked in sequence, and the stacked electrode sheets are wound with a separator to obtain an electrode assembly. The electrode assembly is placed in a pre-formed aluminum-plastic film and dehydrated at 80°C. The prepared electrolyte is then injected, and the lithium-ion battery is obtained through vacuum sealing, settling, formation, and shaping processes.

[0069] The main differences between Examples 1-2 to 1-14, Comparative Examples 1-1 to 1-9 and Example 1-1 are the parameters of the positive electrode coating, negative electrode coating, and electrolyte, as shown in Table 1.

[0070] The energy density (ED) of the batteries prepared in Examples 1-1 to 1-14 and Comparative Examples 1-1 to 1-9 was tested: the thickness of the cell was measured using a thickness gauge and recorded as T; the width and length of the cell were measured using calipers and recorded as W and L, respectively. Then, the cells were charged at 25±2℃ with a constant current and constant voltage of 0.5C to 4.53V, cut off at 0.05C, allowed to stand for 10 minutes, and then discharged at a constant current of 0.2C to 2.8V. The discharge energy was recorded as E. The energy density (ED) = E / (T×W×L). Five batteries were used in each group, and the average energy density was recorded in Table 1.

[0071] Table 1

[0072] Example 2-1 1. Preparation of negative electrode sheet A negative electrode active material (graphite, silicon carbide), dispersant (CMC), binder (SBR), and conductive agent (SP) were mixed in a ratio of 94:1:4:1. Water was then added to adjust the solid content to 48%, and the mixture was stirred in a vacuum mixer to obtain a negative electrode slurry. The negative electrode slurry was uniformly coated onto one surface of a 10 μm thick copper foil current collector. The copper foil was dried at 85°C to obtain a single-sided negative electrode sheet with a 63 μm thick coating. The above steps were repeated on the other surface of the aluminum foil to obtain a double-sided negative electrode sheet. After cold pressing, cutting, and slitting, the sheet was dried under vacuum at 120°C for 12 hours to obtain a negative electrode sheet with dimensions of 73 mm × 1072 mm.

[0073] Among them, the mass fraction (a%) of silicon-carbon material in the negative electrode active material is 5%; the median particle size (Dv50) of silicon-carbon material is 10 μm; and the specific surface area (k) of silicon-carbon material is 2 m². 2 / g; The mass fraction of silicon in silicon-carbon materials is 60%.

[0074] 2. Preparation of the positive electrode sheet The positive electrode active materials (lithium cobalt oxide and lithium iron ferrite (Li2FeO3)) were mixed with conductive agent carbon black and binder polyvinylidene fluoride at a mass ratio of 98:1:1. N-methylpyrrolidone (NMP) was added, and the mixture was stirred under vacuum until the system was homogeneous to obtain a positive electrode slurry. The solid content of the positive electrode slurry was 68%. The positive electrode slurry was uniformly coated onto one surface of a 10 μm thick aluminum foil for the positive electrode current collector. The aluminum foil was dried at 100°C to obtain a positive electrode sheet with a double-sided coating of positive electrode active material layer with a coating thickness of 62 μm. The above steps were repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided positive electrode coating. After cold pressing, cutting, and slitting, the sheet was dried under vacuum at 85°C for 4 hours to obtain a positive electrode sheet with a size of 71 mm × 1062 mm.

[0075] Among them, the mass fraction b% of lithium-rich compounds in the positive electrode active material is 2%; the median particle size Dv50(c) of lithium cobalt oxide is 16 μm, and the median particle size Dv50(d) of lithium ferrite is 4 μm.

[0076] 3. Preparation of electrolyte In an environment with a water content of less than 10 ppm, diethyl carbonate (DEC) and ethylene carbonate (EC) were mixed at a mass ratio of 2:1. Based on the total mass of the electrolyte, lithium hexafluorophosphate (LiPF6) was added to the solvent, dissolved, and mixed evenly. Then, fluoroethylene carbonate (FEC), vinyl sulfate, and a nitrile compound (butadienenitrile) were added to obtain the electrolyte. The mass percentages of LiPF6, fluoroethylene carbonate (A), vinyl sulfate, and nitrile compound in the electrolyte were 12.5%, 2%, 1%, and 1%, respectively.

[0077] 4. Manufacturing of lithium-ion batteries The positive and negative electrode sheets are stacked in sequence, and the stacked electrode sheets are wound with a separator to obtain an electrode assembly. The electrode assembly is placed in a pre-formed aluminum-plastic film and dehydrated at 80°C. The prepared electrolyte is then injected, and the lithium-ion battery is obtained through vacuum sealing, settling, formation, and shaping processes.

[0078] The main difference between Examples 2-2 to 2-26 and Example 2-1 is that the parameters of the positive electrode coating, negative electrode coating, and electrolyte are different, as shown in Table 2.

[0079] The batteries prepared in Examples 2-1 to 2-26 were subjected to the following tests: 1. Cyclic performance test In a constant temperature chamber at (25±2)℃, the lithium-ion battery was charged at a constant current and constant voltage of 1.2C to 4.53V, then charged at a constant voltage to 0.05C, and after resting for 5 minutes, discharged at 0.5C to 2.8V. The capacity obtained in this step was taken as the initial capacity. Cyclic tests were performed using 1.2C charging / 0.5C discharging, and the capacity retention rate of the battery after 200 cycles was calculated.

[0080] Cycle capacity retention (%) = Discharge capacity at 200th cycle (mAh) / Discharge capacity at first cycle (mAh) × 100%.

[0081] The average cycle life of each group of 5 batteries is recorded in Table 2.

[0082] 2. Storage performance test The battery cell was charged to 4.53V at a constant current and constant voltage of 0.5C at room temperature, with a cutoff current of 0.05C. The battery cell was then placed in a constant temperature chamber at (25±2)℃ and left to stand until gas was produced. The gas production status of the battery cell was observed every 1 day.

[0083] Each group contains 5 batteries, and the average storage life is recorded in Table 2.

[0084] Table 2

[0085] Example 3-1 The battery preparation method in this embodiment is largely the same as that in Example 1-1, except that the lithium-rich compound is Li2MnO3.

[0086] Example 3-2 The battery preparation method in this embodiment is largely the same as that in Example 1-1, except that the lithium-rich compound is Li2NiO3.

[0087] Example 3-3 The battery preparation method in this embodiment is largely the same as that in Example 1-1, except that the lithium-rich compound is Li2CoO3.

[0088] Examples 3-4 The battery preparation method in this embodiment is largely the same as that in Example 1-1, except that the nitrile compound is ethylenedionitrile.

[0089] Examples 3-5 The battery preparation method in this embodiment is roughly the same as that in Example 1-1, except that the median particle size Dv50 of the silicon-carbon material is 5 μm.

[0090] Examples 3-6 The battery preparation method in this embodiment is roughly the same as that in Example 1-1, except that the median particle size Dv50 of the silicon-carbon material is 12 μm.

[0091] Examples 3-7 The battery preparation method in this embodiment is roughly the same as that in Example 1-1, except that the median particle size Dv50 of the silicon-carbon material is 15 μm.

[0092] Examples 3-8 The battery preparation method in this embodiment is largely the same as that in Example 1-1, except that the mass fraction of silicon in the silicon-carbon material is 30%.

[0093] Examples 3-9 The battery preparation method in this embodiment is largely the same as that in Example 1-1, except that the mass fraction of silicon in the silicon-carbon material is 70%.

[0094] Examples 3-10 The battery preparation method in this embodiment is largely the same as that in Example 1-1, except that the mass fraction of silicon in the silicon-carbon material is 80%.

[0095] Energy density, cycle performance and storage performance were tested for Examples 3-1 to 3-10. Five batteries were used in each group, and the average value was recorded in Table 3.

[0096] Table 3

[0097] From Tables 1, 2, and 3, we can see that: Based on the comparison of Examples 1-1 to 1-20 and Comparative Examples 1-1 to 1-9, it can be seen that when a / b≥1.5 and 3≤c / d≤8, the loss of active lithium in the first cycle of the negative electrode can be compensated while avoiding the risk of lithium plating on the negative electrode, thereby ensuring the high energy density of the battery.

[0098] Based on the comparison of Examples 1-1 to 1-3 with Comparative Examples 1-2 to 1-3, and the comparison of Examples 1-6 to 1-8 with Comparative Examples 1-8 to 1-9, it can be seen that when 0 < a ≤ 50 and 0 < b ≤ 10, the energy density of the battery can be effectively improved.

[0099] As can be seen from Examples 1-9 to 1-11, when a / b≥1.5 and 3≤c / d≤8, even if a>50 or b>10, the energy density of the battery can still be improved. However, due to the excessive content of silicon-carbon materials or lithium-rich compounds, the side reactions of the battery are aggravated, which degrades the cycle performance of the battery.

[0100] Based on the comparison of Examples 1-2, 1-4~1-5 with Comparative Examples 1-4~1-7, and Examples 1-2, 1-12~1-14, it can be seen that when 10≤c≤20 and 1≤d≤8, the energy density and cycle performance of the battery are better.

[0101] Based on the comparison of Examples 2-1 to 2-4 and Examples 2-20 to 2-26, it can be seen that when 0.5≤B≤4, 0.5≤C≤4, and 1≤(B+C) / b≤3, the long-cycle stability and storage performance of the battery can be further improved.

[0102] Based on the comparisons of Examples 2-3, 2-6 to 2-9, Examples 2-10 to 2-14, and Examples 2-15 to 2-19, it can be seen that 1≤A≤4 and 0.5≤A / k≤2 can generate a protective film with excellent performance, thereby making the battery's cycle performance and storage performance better.

[0103] As can be seen from Examples 1-1 and 3-1 to 3-3, when Li2FeO3, Li2MnO3, Li2NiO3, and Li2CoO3 are selected as lithium-rich compounds, the lithium-rich compounds can fully exert their intrinsic properties, and the battery can exhibit excellent electrochemical performance.

[0104] As can be seen from Examples 1-1 and 3-4, when the nitrile compounds include oxonium or succinic anionyl nitrile, the interface stability of the battery is higher, which can significantly improve the electrochemical performance of the battery.

[0105] As can be seen from Examples 3-5 to 3-7, the median particle size Dv50 of silicon-carbon materials is 5μm to 12μm, which can make the electrochemical performance of the battery better.

[0106] As can be seen from Examples 3-8 to 3-10, when the mass fraction of silicon in silicon-carbon materials is 30% to 70%, the battery can achieve excellent energy density, cycle performance, and storage performance.

[0107] 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 battery, characterized in that, The battery includes a positive electrode, a negative electrode, and an electrolyte; The positive electrode sheet includes a positive current collector and a positive electrode coating disposed on at least one surface of the positive current collector; the positive electrode coating includes a positive electrode active material; the positive electrode active material includes a layered oxide material and a lithium-rich compound; The negative electrode sheet includes a negative electrode current collector and a negative electrode coating disposed on at least one side surface of the negative electrode current collector; the negative electrode coating includes a negative electrode active material, and the negative electrode active material includes a silicon-carbon material; The battery satisfies the following relationship: a / b ≥ 1.5; 3≤c / d≤8; Wherein, the mass fraction of the silicon-carbon material in the negative electrode active material is a%; the mass fraction of the lithium-rich compound in the positive electrode active material is b%; the median particle size Dv50 of the layered oxide material is c μm; and the median particle size Dv50 of the lithium-rich compound is d μm.

2. The battery according to claim 1, characterized in that, 0＜a≤50； And / or, 0 < b ≤ 10; And / or, 10≤c≤20; And / or, 1≤d≤8.

3. The battery according to claim 1, characterized in that, The electrolyte includes fluoroethylene carbonate, ethylene sulfate, and nitrile compounds; The mass fraction of the fluoroethylene carbonate in the electrolyte is A; the mass fraction of the ethylene sulfate in the electrolyte is B; and the mass fraction of the nitrile compound in the electrolyte is C. Where 1≤A≤4, 0.5≤B≤4, and 0.5≤C≤4.

4. The battery according to claim 3, characterized in that, The battery satisfies the following relationship: 0.5≤A / k≤2; The specific surface area of ​​the silicon-carbon material is km². 2 / g.

5. The battery according to claim 3 or 4, characterized in that, The battery satisfies the following relationship: 1≤(B+C) / b≤3.

6. The battery according to claim 4, characterized in that, k≤3。 7. The battery according to claim 3, characterized in that, The nitrile compounds include oxonium and / or butadiene nitrile.

8. The battery according to claim 1, characterized in that, The median particle size Dv50 of the silicon-carbon material is 5μm~12μm; And / or, the mass fraction of silicon in the silicon-carbon material is 30% to 70%.

9. The battery according to claim 1, characterized in that, The layered oxide material includes lithium cobalt oxide and / or nickel cobalt manganese oxide; And / or, the lithium-rich compound has the chemical formula Li2XO3, wherein X is at least one of Mn, Ni, Co, and Fe.

10. An electronic device, characterized in that, Includes the battery as described in any one of claims 1 to 9.

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