A battery and an electric device

Abstract

This application discloses a battery and an electrical device. The battery includes a negative electrode and an electrolyte, wherein the battery satisfies 1 ≤ K ≤ 10, where σ represents the conductivity of the electrolyte in mS / cm; θ represents the contact angle between the negative electrode and the electrolyte in °; and τ represents the tortuosity of the negative electrode. The battery provided in this application achieves fast charging of the entire battery system by simultaneously controlling the tortuosity of the negative electrode, the conductivity of the electrolyte, and the contact angle between the negative electrode and the electrolyte, enabling the negative electrode and the electrolyte to work synergistically.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical technology, specifically relating to a battery and electrical device. Background Technology

[0002] In real life, people's requirements for batteries are increasing. They not only pay attention to their energy density and safety performance, but also consider charging time as an important indicator of battery quality. Therefore, there is an urgent need to improve the fast charging performance of batteries to meet market development and user needs. Summary of the Invention

[0003] This application aims to at least partially address one of the technical problems in the related art. To this end, one objective of this application is to provide a battery and electrical device that enables fast charging of the entire battery system.

[0004] To address the aforementioned problems, a first aspect of this application provides a battery. According to an embodiment of this application, the battery includes a negative electrode and an electrolyte, and the battery satisfies… 1≤K≤10, where σ represents the conductivity of the electrolyte in mS / cm; θ represents the contact angle between the negative electrode and the electrolyte in °; and τ is the tortuosity of the negative electrode. The battery provided in this application achieves fast charging of the entire battery system by simultaneously controlling the tortuosity of the negative electrode, the conductivity of the electrolyte, and the contact angle between the negative electrode and the electrolyte, enabling the negative electrode and electrolyte to work synergistically.

[0005] A second aspect of this application provides an electrical device comprising the battery described in the first aspect. Therefore, the electrical device, by employing the aforementioned battery, possesses excellent fast-charging capability. The features and advantages described above for the battery also apply to this electrical device, and will not be repeated here.

[0006] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Detailed Implementation

[0008] The main problem with existing technologies lies in their over-reliance on optimizing a single parameter, leading to an imbalance in overall battery performance. For example, while high fluoride content can improve interfacial stability, it makes it difficult for the electrolyte to fully wet the electrode pores, and reducing the electrode tortuosity (τ) sacrifices mechanical stability. To shorten the lithium-ion transport path, existing technologies tend to increase electrode porosity to reduce the τ value. However, excessively high porosity significantly reduces the mechanical strength of the electrode. This soft, porous structure is prone to expansion and deformation during cyclic charging and discharging, leading to the shedding of active materials and a sharp reduction in battery life. Furthermore, while high porosity theoretically benefits electrolyte penetration, if the contact angle θ between the negative electrode and the electrolyte is not optimized synchronously, the electrolyte may accumulate in the surface pores of the negative electrode, leaving the deeper regions in a "semi-dry" state. Simply adjusting a single parameter in isolation cannot meet the overall synergistic requirements of fast-charging batteries. The key to overcoming this bottleneck lies in establishing a quantitative model of the synergistic effects of multiple parameters.

[0009] In view of this, this application proposes a technical solution for synergistic optimization of electrolyte and negative electrode structure, and provides a design method for fast-charging battery electrolyte and negative electrode. The battery disclosed in this application can achieve the fast-charging goal of the entire battery system.

[0010] In a first aspect, this application provides a battery, including a negative electrode and an electrolyte, wherein the battery satisfies... 1≤K≤10; where σ is the conductivity of the electrolyte, in mS / cm; θ is the contact angle between the negative electrode and the electrolyte, in °; and τ is the tortuosity of the negative electrode.

[0011] Specifically, considering that the electrolyte's wetting rate on the electrode is a bottleneck factor limiting fast charging, this invention constructs a quantitative model of multi-parameter synergistic effect to simultaneously optimize the negative electrode and electrolyte, thereby improving the battery's fast charging performance. The design methods for the electrolyte and electrode in fast-charging batteries are as follows:

[0012] Based on porous electrode theory and interfacial reaction kinetics, the effective Li+ transport rate equation is established:

[0013]

[0014] Where σ is the conductivity of the electrolyte, ΔΦ is the potential gradient, L is the electrode thickness, and η is the overpotential. Under fast charging conditions (η < 0.1V), the exponential term can be approximated linearly, and the formula simplifies to:

[0015]

[0016] In the formula, α is the experimental fit index, used to correct for differences in wetting characteristics of different negative electrode materials. For example, for graphite, α = 1.3. Therefore, a comprehensive performance constant is defined.

[0017]

[0018] For 3C to 4C fast charging systems, the following condition must be met: 1.00 ≤ K < 1.67;

[0019] For 4C to 5C fast charging systems, the following condition must be met: 1.67 ≤ K < 2.42;

[0020] For 5C to 6C fast charging systems, the following condition must be met: 2.42 ≤ K < 3.00;

[0021] For fast charging systems with a capacity of ≥6C, the requirement is 3.00≤K≤10.00.

[0022] In this invention, the conductivity σ of the electrolyte is measured using a conductivity meter. Specifically, after completely discharging the battery casing, the electrolyte is directly drawn up with a syringe. If it cannot be drawn up, the electrode core is removed and immersed in an inert solvent. The electrolyte composition is determined using chromatography. The electrolyte conductivity testing process then includes the following steps:

[0023] (1) Calibration: The instrument is calibrated using a standard KCl solution (e.g., 0.1 mol / L, σ = 12.88 mS / cm at 25℃).

[0024] (2) Sample preparation: Inject the electrolyte into a clean measuring cell and remove air bubbles.

[0025] (3) Temperature control: After immersing the electrode in the electrolyte, place it in a 25°C oven for 1 hour to avoid temperature fluctuations.

[0026] (4) Reading: Read the conductivity value after it has stabilized.

[0027] In this invention, the contact angle θ between the negative electrode and the electrolyte is measured using a contact angle measuring instrument. Specifically, after completely discharging the battery casing, the electrode core is removed, and the negative electrode is disassembled and immersed in an inert solvent to remove residual electrolyte from its surface. The contact angle testing process then includes the following steps:

[0028] (1) Sample preparation: The negative electrode was cut into 10mm×10mm pieces and ultrasonically cleaned with anhydrous ethanol for 5 minutes.

[0029] (2) Adding liquid: Use a pipette to add 2 μL of electrolyte to the surface of the negative electrode.

[0030] (3) Image acquisition: Use a high-speed camera (≥100fps) to capture the shape of the droplets and ensure that the droplets are stable (no evaporation or deformation within 5 seconds).

[0031] (4) Data analysis: The droplet profile was fitted using the software KrüssADVANCE, and the contact angle was calculated.

[0032] In this invention, the tortuosity τ of the negative electrode is measured using X-ray micro-CT. Specifically, after removing the completely discharged battery casing, the electrode core is taken out, and the negative electrode is disassembled and immersed in an inert solvent to remove residual electrolyte from the surface. The tortuosity testing process then includes the following steps:

[0033] (1) Sample preparation: The negative electrode is cut into a cylinder with a diameter of 3 mm to avoid structural damage.

[0034] (2) CT scan: Scanning at 20kV voltage to reconstruct a three-dimensional pore model.

[0035] (3) Calculation of tortuosity: Where L eff L0 represents the actual lithium-ion transport path (tracked through the pore path using the maximum sphere algorithm), and L0 represents the apparent length in the electrode thickness direction.

[0036] The parameter model provided in this application realizes the coordinated control of multiple parameters σ, θ, and τ, establishes a K-value quantification model of electrochemical-fluid dynamic coupling, clarifies the threshold, improves the fast charging performance of the battery, and enables the battery to meet the requirements of the fast charging system.

[0037] In this application, the conductivity of the electrolyte and its wettability to the negative electrode can be improved by adjusting the lithium salt concentration and solvent ratio in the electrolyte and introducing additives. At the same time, the tortuosity of the electrode can be reduced from multiple dimensions by optimizing the morphology of the negative electrode active material, designing the conductive agent network, controlling the electrode rolling parameters, and using magnetic field induction during electrode coating, thereby adjusting the hydrophilicity of the electrode. Ultimately, the conductivity σ of the electrolyte, the contact angle θ between the negative electrode and the electrolyte, and the tortuosity τ of the negative electrode can be synergistically controlled.

[0038] The battery provided in this application has the following effect: by adjusting the tortuosity of the negative electrode, the conductivity of the electrolyte, and the contact angle between the negative electrode and the electrolyte, the negative electrode and the electrolyte work together to achieve the goal of fast charging of the entire battery system.

[0039] For example, the K value can specifically be a range of 1.10, 1.15, 1.20, 1.25, 1.30, 1.35, 1.40, 1.45, 1.50, or any combination thereof. Within the above range, the electrolyte and the negative electrode work synergistically to achieve the 3C to 4C super-fast charging target of the entire battery system.

[0040] For example, the K value can specifically be a range of 1.70, 1.75, 1.80, 1.90, 2.00, 2.10, 2.20, 2.30, 2.40, or any combination thereof. Within the above range, the electrolyte and the negative electrode work synergistically to achieve the 4C to 5C super-fast charging target of the entire battery system.

[0041] For example, the K value can specifically be a range of 2.50, 2.55, 2.60, 2.70, 2.75, 2.80, 2.85, 2.90, 2.95, or any combination thereof. Within the above range, the electrolyte and the negative electrode work synergistically to achieve the 5C to 6C super-fast charging target of the entire battery system.

[0042] For example, the K value can specifically be a range of 3.10, 3.50, 4.00, 4.50, 5.00, 5.50, 6.00, 6.50, 7.00, 8.00, 9.00, 10.00, or any combination thereof. Within the above range, the electrolyte and the negative electrode work synergistically to achieve a super-fast charging target of greater than or equal to 6C for the entire battery system.

[0043] In some preferred embodiments of this application, 3≤K≤10. When the value of K is within the above range, the super-fast charging target of ≥6C for the entire battery system can be met.

[0044] In some embodiments of this application, the conductivity of the electrolyte σ≥8mS / cm, and / or, the contact angle θ between the negative electrode and the electrolyte ≤40°, and / or, the tortuosity τ of the negative electrode ≤2.5.

[0045] In some preferred embodiments of this application, the conductivity σ of the electrolyte satisfies: 12mS / cm≤σ≤18mS / cm, and / or the contact angle θ between the negative electrode and the electrolyte satisfies: 10°≤θ≤30°, and / or the tortuosity τ of the negative electrode satisfies: 1.3≤τ≤1.8.

[0046] Specifically, the electrolyte conductivity σ ≥ 8 mS / cm can be between 12 mS / cm and 18 mS / cm, for example, within the range of 8 mS / cm, 9 mS / cm, 10 mS / cm, 11 mS / cm, 12 mS / cm, 12.5 mS / cm, 13 mS / cm, 13.5 mS / cm, 14 mS / cm, 14.5 mS / cm, 15 mS / cm, 15.5 mS / cm, 16 mS / cm, 16.5 mS / cm, 17 mS / cm, 17.5 mS / cm, 18 mS / cm, 19 mS / cm, 20 mS / cm, or any combination thereof. Therefore, an electrolyte conductivity within this range is beneficial for increasing the migration rate of active ions in the electrolyte and improving the battery charging rate.

[0047] Specifically, the contact angle θ between the negative electrode and the electrolyte is ≤40°, and can be between 10° and 30°, for example, within the range of 8°, 9°, 10°, 11°, 12°, 13°, 14°, 15°, 16°, 17°, 18°, 19°, 20°, 21°, 22°, 23°, 24°, 25°, 26°, 27°, 28°, 29°, 30°, 31°, 32°, 33°, 34°, 35°, 36°, 37°, 38°, 39°, 40°, or any combination thereof. Therefore, a contact angle within this range enhances the wettability of the electrolyte on the negative electrode, promotes sufficient contact between the electrolyte and the electrode, reduces the internal resistance of the negative electrode, and increases the migration rate of active ions within the negative electrode, thereby improving the battery's charging rate.

[0048] Specifically, the tortuosity τ of the negative electrode sheet should be ≤2.5, and can be between 1.3 and 1.8, for example, within the range of 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, or any combination thereof. A tortuosity within this range, and a smaller tortuosity, facilitates thorough electrolyte wetting, resulting in faster battery charging. Furthermore, it works synergistically with the electrolyte conductivity to effectively improve the battery's fast-charging performance.

[0049] In some embodiments of this application, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material, which includes graphite. The graphite includes a first graphite and a second graphite. At least a portion of the surface of the first graphite is provided with a coating layer, and the surface of the second graphite is not provided with a coating layer.

[0050] Specifically, by using the first graphite and the second graphite in combination, the pore structure and tortuosity of the negative electrode sheet can be adjusted, which is beneficial to improving the migration ability of active ions and the liquid phase transport ability, and is easier to match with the conductivity of the electrolyte. This can effectively improve the fast charging performance of the battery, while basically not affecting the energy density, safety performance and cycle life of the battery.

[0051] In some embodiments of this application, the first graphite and the second graphite respectively include at least one of artificial graphite and natural graphite.

[0052] Specifically, natural graphite has low cost and high specific capacity, while artificial graphite has good cycle performance and excellent fast-charging performance. The appropriate graphite material can be selected according to the actual production requirements.

[0053] In some embodiments of this application, the mass ratio of the first graphite to the second graphite is (50-80):(20-50).

[0054] Specifically, the mass ratio of the first graphite to the second graphite can be, for example, 50:50, 60:40, 70:30, 80:20, etc. When the mass ratio of the first graphite to the second graphite in the negative electrode active material meets the above-mentioned range, it is beneficial to obtain a negative electrode sheet with lower tortuosity, which in turn facilitates the full wetting of the negative electrode sheet by the electrolyte and improves the charging rate of the battery.

[0055] In some embodiments of this application, the coating layer includes a carbon coating layer, which includes at least one of amorphous carbon nanotubes and graphene.

[0056] Specifically, coating graphite with a carbon coating layer can improve the compatibility of graphite materials with electrolytes, enhance the cycle stability of graphite materials, and improve rate performance, resulting in higher energy density and longer battery life during charge and discharge. Coating graphite materials with at least one of amorphous carbon, carbon nanotubes, and graphene can improve the electrochemical performance of graphite materials, reduce side reactions between graphite materials and electrolytes, and further improve the charge and discharge capabilities of graphite materials.

[0057] In some embodiments of this application, the first graphite is secondary particulate carbon-coated graphite, and the second graphite is primary particulate uncoated graphite.

[0058] Specifically, the first type of graphite is secondary carbon-coated graphite, which refers to the process of re-agglomerating fine graphite particles into larger particles through a secondary granulation process, and then coating these particles with a layer of carbon material. This process can improve the particle size distribution, specific surface area, and conductivity of graphite, while also enhancing the stability and cycle performance of the material through the carbon coating layer. The second type of graphite can be primary uncoated graphite, which refers to the raw particles that have not undergone secondary processing or agglomeration during the preparation of graphite materials and whose surface is not coated with carbon. Primary uncoated graphite is usually obtained directly from graphite raw materials through crushing, grinding, or other physical methods, and typically has a small particle size and narrow particle size distribution. By mixing secondary carbon-coated graphite and primary uncoated graphite, the excellent rate performance, cycle stability, and fast charging performance of secondary carbon-coated graphite are combined with the rapid ion diffusion path of primary uncoated graphite, thereby balancing the fast charging performance and cycle stability of the battery.

[0059] In some embodiments of this application, the aforementioned negative electrode active material layer may include a binder in addition to the negative electrode active material (i.e., the first graphite and the second graphite). The binder and conductive agent are conventional choices in the battery field. Exemplary binders include, but are not limited to, one or more of the following: styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl alcohol (PVA), polyacrylonitrile (PAN), polyimide (PI), polyacrylic acid (PAA), polyacrylates (such as polymethyl methacrylate, polymethyl acrylate, polyethyl acrylate, etc.), polyolefins (such as polypropylene, polyethylene, etc.), carboxymethyl cellulose (CMC), sodium alginate, etc.

[0060] In some embodiments of this application, the negative electrode active material layer may include a conductive agent or other additives. Conductive agents include, but are not limited to, one or more of carbon nanotubes, carbon black, graphene, carbon fibers, acetylene black, Ketjen black, and graphite flakes. Other additives include, but are not limited to, one or more of mesoporous silica, mesoporous alumina, silica microspheres, and alumina nanoparticles.

[0061] In some preferred embodiments of this application, the negative electrode active material layer includes a conductive agent, which may include carbon black and / or carbon nanotubes. The conductive agent can be used to adjust the conductive network of the negative electrode active material layer, thereby optimizing the tortuosity of the negative electrode sheet.

[0062] In some embodiments of this application, the mass ratio of the negative electrode active material to the conductive agent is 100:(0.5-1.5). For example, the mass ratio of the negative electrode active material to the conductive agent can be 100:0.5, 100:0.6, 100:0.7, 100:0.8, 100:0.9, 100:1.0, 100:1.1, 100:1.2, 100:1.3, 100:1.4, 100:1.5, or any combination thereof. Maintaining a mass ratio of the negative electrode active material to the conductive agent within this range can further optimize the structure of the negative electrode active material layer, balancing energy density and conductivity requirements.

[0063] The aforementioned negative electrode sheet can be obtained by coating a slurry containing negative electrode active material, binder, and conductive agent onto a negative electrode current collector using a normal slurry coating process, followed by drying and rolling. The negative electrode current collector can be single-sided or double-sided coated. In other words, one side of the negative electrode current collector may have a negative electrode active layer, or both opposite sides of the negative electrode current collector may have negative electrode active material layers. When the negative electrode current collector is double-sided coated, it is sufficient as long as the design of the negative electrode active material layer on either side meets the aforementioned scheme of this application. The current collector carrying the negative electrode active material layer can include, but is not limited to, any of the following: copper foil, composite copper foil, carbon-coated copper foil, aluminum foil, composite aluminum foil, carbon-coated aluminum foil, stainless steel foil, copper alloy foil, copper-plated film, etc.

[0064] In some embodiments of this application, the negative electrode active material layer can be a single-layer structure, a double-layer structure, or a multi-layer structure with three or more layers.

[0065] In some embodiments of this application, in the negative electrode active material layer, the mass ratio of the first graphite to the second graphite on the side closer to the negative electrode current collector is greater than the mass ratio of the first graphite to the second graphite on the side farther from the negative electrode current collector.

[0066] Specifically, setting the mass ratio of the first graphite to the second graphite on the side closer to the negative electrode current collector to be greater than the mass ratio of the first graphite to the second graphite on the side farther from the negative electrode current collector can regulate the tortuosity of the negative electrode active material layer, increase the transport rate of active ions in the negative electrode active material layer, improve the conductivity of the negative electrode active material, thereby improving the charge and discharge rate of the battery, and thus improving the fast charging performance of the battery.

[0067] In some embodiments of this application, the negative electrode active material layer includes at least: a first negative electrode active material layer disposed on the negative electrode current collector; a second negative electrode active material layer disposed on the surface of the first negative electrode active material layer away from the negative electrode current collector; and the mass ratio of the first graphite to the second graphite in the first negative electrode active material layer is greater than the mass ratio of the first graphite to the second graphite in the second negative electrode active material layer.

[0068] Specifically, the negative electrode active material layer is configured as multiple layers. Setting the mass ratio of the first graphite to the second graphite in the first negative electrode active material layer to be greater than that in the second negative electrode active material layer can regulate the appropriate tortuosity of the first and second negative electrode active material layers. Active ions can quickly enter the second negative electrode active material layer and gradually enter the first negative electrode active material layer. They can also cooperate with the conductivity of the electrolyte, thereby effectively improving the fast charging performance of the battery.

[0069] In some embodiments of this application, the areal density of the negative electrode active material layer is 135 g / m². 2~320g / m 2 ; and / or, the compaction density of the negative electrode active material layer is 1.3 g / cm³. 3 ~1.9g / cm 3 .

[0070] Specifically, the areal density of the negative electrode active material layer can be, for example, 135 g / m². 2 145g / m 2 155g / m 2 165g / m 2 175g / m 2 185g / m 2 195g / m 2 200g / m 2 235g / m 2 255g / m 2 285g / m 2 305g / m 2 315g / m 2 325g / m 2 Or any combination of the above ranges, where the areal density of the negative electrode active material layer is within the aforementioned range, allows the negative electrode sheet to have suitable tortuosity, thereby achieving excellent fast-charging performance of the battery; the compaction density of the negative electrode active material layer can, for example, be 1.3 g / cm³. 3 1.4g / cm 3 1.5g / cm 3 1.6g / cm 3 1.7g / cm 3 1.8g / cm 3 1.9g / cm 3 Or any combination of the above ranges, the compaction density of the negative electrode active material layer within the above range is conducive to obtaining a negative electrode sheet with lower tortuosity, which in turn is conducive to the electrolyte fully wetting the negative electrode sheet, thereby achieving excellent fast charging performance of the battery.

[0071] In this application, the areal density of the negative electrode active material layer refers to the areal density of both sides of the negative electrode active material layer. Specifically, the areal density of the negative electrode active material layer refers to the mass of the negative electrode active material layer per unit area. The areal density can be calculated using the following formula: Areal density of the negative electrode active material layer = Mass of the negative electrode active material layer / Area of ​​the negative electrode active material layer. Specifically, it can be tested using the following method: Take a sample of a certain area of ​​electrode sheet, weigh it, subtract the mass of the current collector (copper foil), and then divide by the sample area to obtain the areal density of the negative electrode active material layer.

[0072] In this application, the compaction density of the negative electrode active material layer refers to the mass of the negative electrode active material layer per unit volume. The compaction density can be calculated using the following formula: Compaction density of the negative electrode active material layer = Areal density of the negative electrode active material layer / Thickness of the negative electrode active material layer. Specifically, it can be tested using the following method: Measure the total thickness of the electrode sheet after compaction using a thickness gauge, then subtract the thickness of the current collector (copper foil) to obtain the thickness of the negative electrode active material layer, and finally divide the areal density of the negative electrode active material layer by its thickness to obtain the compaction density of the negative electrode active material layer.

[0073] In some embodiments of this application, the battery further includes a positive electrode sheet, which 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 at least one of a layered positive active material, an olivine-type phosphate positive active material, and a spinel-structured positive active material.

[0074] Specifically, the positive electrode active material may include at least one of the following: layered structure positive electrode active materials (e.g., nickel-cobalt-manganese ternary positive electrode materials, nickel-cobalt-aluminum ternary positive electrode materials, lithium nickel oxide / sodium, lithium cobalt oxide / sodium, lithium manganese oxide / sodium, lithium-rich / sodium layered and rock salt phase layered materials), olivine-type phosphate positive electrode active materials (e.g., lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, etc.), and spinel structure positive electrode active materials (e.g., spinel lithium manganese oxide, spinel lithium nickel manganese oxide, lithium-rich spinel lithium manganese oxide, and lithium nickel manganese oxide, etc.). It is understood that the above-mentioned positive electrode active materials may further include doping elements and coating layers, etc.

[0075] In some embodiments of this application, the positive electrode active material layer may further include a positive electrode lithium supplement, a conductive agent, a binder, or other additives. The binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a terpolymer of PVDF-tetrafluoroethylene-propylene, a terpolymer of PVDF-hexafluoropropylene-tetrafluoroethylene, a tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins. This allows the positive electrode active material layer to adhere well to the positive electrode current collector, resulting in strong adhesion and reducing the likelihood of positive electrode coating detachment. The conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. This effectively improves conductivity, reduces internal resistance, and enhances the electrochemical performance of the battery.

[0076] The aforementioned positive electrode sheet can be obtained by coating a slurry containing positive electrode active material, binder, and conductive agent onto a positive electrode current collector using a normal slurry coating process, followed by drying and rolling. The positive electrode current collector can be single-sided or double-sided coated. In other words, the positive electrode current collector can have a positive electrode active layer on one side surface, or it can have positive electrode active material layers on both opposite sides. When the positive electrode current collector is double-sided coated, it is sufficient as long as the design of the positive electrode active material layer on either side meets the aforementioned scheme of this application. The positive electrode current collector carrying the positive electrode active material layer can be a metal current collector or a composite current collector. For example, metal current collectors include, but are not limited to, aluminum foil current collectors; composite current collectors may include a polymer material base layer (such as a base layer of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.) and a metal layer (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) formed on at least one surface of the polymer material base film.

[0077] In some preferred embodiments of this application, the positive electrode active material includes at least one of nickel-cobalt-manganese ternary cathode material, lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, spinel lithium nickel manganese oxide, and lithium-rich spinel lithium manganese oxide. Therefore, the battery exhibits better cycle stability and safety performance.

[0078] In some embodiments of this application, the electrolyte includes a lithium salt, which includes at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium difluorooxalateborate.

[0079] Specifically, lithium salts can provide lithium ions for lithium-ion batteries, support the stability of the electrolyte and electrochemical reactions, help form a protective SEI film, improve conductivity, and enhance the safety of lithium-ion batteries.

[0080] In some embodiments of this application, the electrolyte includes a solvent, which includes at least one of ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, ethyl acetate, methyl propionate, and ethyl propionate.

[0081] Specifically, the solvent can fully dissolve lithium salts, provide an ion transport medium, and also help improve the electrochemical and safety performance of lithium-ion batteries.

[0082] In some embodiments of this application, the electrolyte includes additives, which include at least one of vinylene carbonate, vinyl sulfate, fluoroethylene carbonate, fluoroethers, sulfur-based additives, and nitrile-based additives.

[0083] Specifically, the additives mentioned above can further improve the energy density, fast charging performance, and cycle life of lithium-ion batteries.

[0084] In some preferred embodiments of this application, the lithium salt includes lithium hexafluorophosphate, the solvent includes at least one of ethylene carbonate, ethyl methyl carbonate and ethyl acetate, and the additive includes vinylene carbonate and / or fluoroethylene carbonate.

[0085] In some embodiments of this application, the mass percentages of lithium salt, solvent, and additives are (15%-20%):(65%-75%):(10%-15%). For example, the mass percentages of lithium salt, solvent, and additives can be within the ranges of 15%:70%:15%, 16%:74%:10%, 16%:69%:15%, 18%:67%:15%, 20%:65%:15%, 20%:70%:10%, or any combination thereof. Within this range, the mass percentages of lithium salt, solvent, and additives can regulate the conductivity of the electrolyte, increase the wettability of the electrolyte to the electrodes, and thereby improve the fast-charging performance of the battery.

[0086] In some embodiments of this application, the battery further includes a separator disposed between the positive electrode and the negative electrode, serving to isolate the positive and negative electrodes. This application does not limit the type of separator; any separator material from existing batteries can be used. Exemplary separators include, but are not limited to, single-layer PP (polypropylene) film, single-layer PE (polyethylene) film, double-layer PP / PE film, double-layer PP / PP film, and triple-layer PP / PE / PP film.

[0087] The battery of this application may be in the form of a battery cell, a battery module, or a battery pack. In some embodiments, battery cells may be assembled into a battery module, and the number of battery cells contained in a battery module may be one or more, the specific number of which can be selected by those skilled in the art based on the application and capacity of the battery module. In some embodiments, battery modules may also be assembled into a battery pack, and the number of battery modules contained in a battery pack may be one or more, the specific number of which can be selected by those skilled in the art based on the application and capacity of the battery pack.

[0088] The specific type of battery described in this application is not particularly limited. For example, from a shape perspective, the battery includes, but is not limited to, prismatic batteries, pouch batteries, and cylindrical batteries, etc., and this application does not impose any particular restrictions. From the perspective of the core structure, the battery core can be a wound core (i.e., a core formed by stacking positive electrode sheets, negative electrode sheets, and separators and then winding them) or a stacked core (i.e., multiple positive electrode sheets, negative electrode sheets, and separators are stacked to form a core). The outer casing can be a hard casing (such as a steel casing, a hard plastic casing, etc.) or a soft casing (such as an aluminum-plastic film casing, a pouch-type soft casing, etc.), etc., and this application does not impose any particular restrictions.

[0089] Secondly, this application provides an electrical device including the battery described in the first aspect. This electrical device, due to the use of the battery described in the first aspect, possesses excellent fast-charging capability. The features and advantages described above for the battery also apply to this electrical device, and will not be repeated here.

[0090] Battery cells, battery modules, and battery packs can be used as power sources for electrical devices or as energy storage units for electrical devices. Electrical devices can include, but are not limited to, 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.

[0091] As electrical equipment, battery cells, battery modules, or battery packs can be selected according to their usage requirements.

[0092] In some embodiments of this application, the electrical device may be a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the electrical device, a battery pack or battery module may be used.

[0093] In other embodiments of this application, the device may be a mobile phone, tablet computer, laptop computer, etc. This device typically requires a thin and light design and may use a single battery cell as its power source.

[0094] It should be noted that the features and advantages described above for the battery also apply to this electrical device, and will not be repeated here.

[0095] The embodiments of this application are described in detail below. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. In addition, unless otherwise specified, all reagents used in the following embodiments are commercially available or can be synthesized according to the methods described herein or known methods. For reaction conditions not listed, they are also readily available to those skilled in the art.

[0096] This embodiment illustrates the battery disclosed in this invention, including a positive electrode, a negative electrode, and an electrolyte. The preparation of the positive electrode, negative electrode, and electrolyte includes the following steps:

[0097] Positive electrode 1:

[0098] Lithium iron phosphate (LiFePO4), carbon black (COP), and PVDF (PVDF) binder were mixed in a mass ratio of 96:2:2. The resulting powder was placed in a vacuum mixer, and N-methylpyrrolidone (NMP) solvent was added and stirred until homogeneous to obtain a positive electrode slurry. This slurry was then sieved (through a 200-mesh screen) and coated onto aluminum foil for the positive electrode current collector. After drying in an oven at 120°C, the slurry was rolled and slit to obtain the positive electrode sheet. The resulting positive electrode sheet had a double-sided areal density of 420 g / m³. 2 The compacted density is 2.6 g / cm³. 3 .

[0099] Negative electrode 1:

[0100] The negative electrode active material, conductive agent carbon black, thickener CMC and binder SBR are mixed in a mass ratio of 100:1:1.6:1.8. The mixed powder is placed in a homogenizer, and deionized water is added as a solvent to mix and stir evenly to obtain a negative electrode slurry. The negative electrode slurry is sieved (200 mesh screen) and coated onto the negative electrode current collector aluminum foil. After drying in an oven at 105℃, it is then rolled and cut to obtain negative electrode sheet 1.

[0101] The negative electrode active material includes first graphite (secondary carbon-coated graphite particles) and second graphite (primary uncoated graphite particles), with a mass ratio of 80:20 between the first graphite and the second graphite.

[0102] The resulting negative electrode has a bifacial areal density of 200 g / m³. 2 The compacted density is 1.56 g / cm³. 3 The tortuosity τ of negative electrode 1 is 2.0.

[0103] Negative electrode 2:

[0104] The negative electrode active material, conductive agent carbon black, thickener CMC and binder SBR are mixed in a mass ratio of 100:1:1.6:1.8. The mixed powder is placed in a homogenizer, and deionized water is added as a solvent to mix and stir evenly to obtain a negative electrode slurry. The negative electrode slurry is sieved (200 mesh screen) and coated onto the negative electrode current collector aluminum foil. After drying in an oven at 105℃, it is rolled and cut to obtain negative electrode sheet 2.

[0105] The negative electrode active material includes first graphite (secondary carbon-coated graphite particles) and second graphite (primary uncoated graphite particles), with a mass ratio of 70:30 between the first graphite and the second graphite.

[0106] The resulting negative electrode has a bifacial areal density of 200 g / m³. 2 The compacted density is 1.56 g / cm³. 3 The tortuosity τ of negative electrode 2 is 2.4.

[0107] Negative electrode 3:

[0108] The negative electrode active material, conductive agent carbon black, thickener CMC and binder SBR are mixed in a mass ratio of 100:1:1.6:1.8. The mixed powder is placed in a homogenizer, and deionized water is added as a solvent to mix and stir evenly to obtain a negative electrode slurry. The negative electrode slurry is sieved (200 mesh screen) and coated onto the negative electrode current collector aluminum foil. After drying in an oven at 105℃, it is then rolled and cut to obtain the negative electrode sheet 3.

[0109] The negative electrode active material includes first graphite (secondary carbon-coated graphite particles) and second graphite (primary uncoated graphite particles), with a mass ratio of 60:40 between the first graphite and the second graphite.

[0110] The resulting negative electrode has a bifacial areal density of 200 g / m³. 2 The compacted density is 1.56 g / cm³. 3 The tortuosity τ of negative electrode 3 is 2.9.

[0111] Negative electrode 4:

[0112] The negative electrode active material, conductive agent carbon black, thickener CMC and binder SBR are mixed in a mass ratio of 100:1:1.6:1.8. The mixed powder is placed in a homogenizer, and deionized water is added as a solvent to mix and stir evenly to obtain a negative electrode slurry. The negative electrode slurry is sieved (200 mesh screen) and coated onto the negative electrode current collector aluminum foil. After drying in an oven at 105℃, it is rolled and cut to obtain the negative electrode sheet 4.

[0113] The negative electrode active material includes first graphite (secondary carbon-coated graphite particles) and second graphite (primary uncoated graphite particles), with a mass ratio of 50:50 between the first graphite and the second graphite.

[0114] The resulting negative electrode has a bifacial areal density of 200 g / m³. 2 The compacted density is 1.56 g / cm³. 3 The tortuosity τ of negative electrode 4 is 3.5.

[0115] Negative electrode 5:

[0116] First negative electrode active material layer: The first negative electrode active material, conductive agent carbon black, thickener CMC and binder SBR are mixed in a mass ratio of 100:1:1.6:1.8. The mixed powder is placed in a homogenizer, deionized water is added as a solvent and the mixture is stirred evenly to obtain a negative electrode slurry. The negative electrode slurry is sieved (200 mesh screen) and then coated on the negative electrode current collector aluminum foil. The first negative electrode active material includes first graphite (secondary particle carbon-coated graphite) and second graphite (primary particle uncoated graphite), and the mass ratio of the first graphite and the second graphite is 80:20.

[0117] Second negative electrode active material layer: The second negative electrode active material, conductive agent carbon black, thickener CMC and binder SBR are mixed in a mass ratio of 100:1:1.6:1.8. The mixed powder is placed in a homogenizer, deionized water is added as a solvent and the mixture is stirred evenly to obtain a negative electrode slurry. The negative electrode slurry is sieved (200 mesh sieve) and then coated on the first negative electrode active material layer. The second negative electrode active material includes first graphite (secondary particle carbon-coated graphite) and second graphite (primary particle uncoated graphite), and the mass ratio of the first graphite to the second graphite is 60:40.

[0118] After drying in an oven at 105℃, the material is then rolled and slit to obtain negative electrode sheet 5. The resulting negative electrode sheet has a double-sided areal density of 200 g / m³. 2 The compacted density is 1.5 g / cm³. 3 The tortuosity τ of negative electrode 5 is 1.9.

[0119] Negative electrode 6:

[0120] First negative electrode active material layer: The first negative electrode active material, conductive carbon nanotubes, thickener CMC and binder SBR are mixed in a mass ratio of 100:1:1.6:1.8. The mixed powder is placed in a homogenizer, deionized water is added as a solvent and the mixture is stirred evenly to obtain a negative electrode slurry. The negative electrode slurry is sieved (200 mesh sieve) and then coated on the negative electrode current collector aluminum foil. The first negative electrode active material includes first graphite (secondary particle carbon-coated graphite) and second graphite (primary particle uncoated graphite), and the mass ratio of the first graphite and the second graphite is 80:20.

[0121] Second negative electrode active material layer: The second negative electrode active material, conductive carbon nanotubes, thickener CMC and binder SBR are mixed in a mass ratio of 100:1:1.6:1.8. The mixed powder is placed in a homogenizer, deionized water is added as a solvent and the mixture is stirred evenly to obtain a negative electrode slurry. The negative electrode slurry is sieved (200 mesh sieve) and then coated on the first negative electrode active material layer. The second negative electrode active material includes first graphite (secondary particle carbon-coated graphite) and second graphite (primary particle uncoated graphite), and the mass ratio of the first graphite to the second graphite is 60:40.

[0122] After drying in an oven at 105℃, the material is then rolled and slit to obtain negative electrode sheet 6. The resulting negative electrode sheet has a double-sided areal density of 200 g / m³. 2 The compacted density is 1.5 g / cm³. 3 The tortuosity τ of negative electrode 6 is 1.7.

[0123] Negative electrode 7:

[0124] First negative electrode active material layer: The first negative electrode active material, conductive agent carbon black, thickener CMC and binder SBR are mixed in a mass ratio of 100:1.4:1.6:1.8. The mixed powder is placed in a homogenizer, and deionized water is added as a solvent to mix and stir evenly to obtain a negative electrode slurry. The negative electrode slurry is sieved (200 mesh screen) and then coated on the negative electrode current collector aluminum foil. The first negative electrode active material includes first graphite (secondary particle carbon-coated graphite) and second graphite (primary particle uncoated graphite), and the mass ratio of the first graphite and the second graphite is 80:20.

[0125] Second negative electrode active material layer: The second negative electrode active material, conductive agent carbon black, thickener CMC and binder SBR are mixed in a mass ratio of 100:0.6:1.6:1.8. The mixed powder is placed in a homogenizer, deionized water is added as a solvent and the mixture is stirred evenly to obtain a negative electrode slurry. The negative electrode slurry is sieved (200 mesh screen) and then coated on the first negative electrode active material layer. The second negative electrode active material includes first graphite (secondary particle carbon-coated graphite) and second graphite (primary particle uncoated graphite), and the mass ratio of the first graphite to the second graphite is 60:40.

[0126] After drying in an oven at 105℃, the negative electrode sheet 7 is obtained by rolling and slitting. The double-sided areal density of the obtained negative electrode sheet is 200 g / m³. 2 The compacted density is 1.5 g / cm³. 3 The tortuosity τ of the negative electrode 7 is 1.8.

[0127] Negative electrode plate 8:

[0128] The negative electrode active material, conductive agent carbon black, thickener CMC and binder SBR are mixed in a mass ratio of 100:1:1.6:1.8. The mixed powder is placed in a homogenizer, and deionized water is added as a solvent to mix and stir evenly to obtain a negative electrode slurry. The negative electrode slurry is sieved (200 mesh screen) and coated onto the negative electrode current collector aluminum foil. A magnetic field of 0.6T is applied to the coating, and it is dried in an oven at 105℃. After being rolled and cut, the negative electrode sheet 8 is obtained.

[0129] The negative electrode active material includes first graphite (secondary carbon-coated graphite particles) and second graphite (primary uncoated graphite particles), with a mass ratio of 50:50 between the first graphite and the second graphite.

[0130] The resulting negative electrode has a bifacial areal density of 200 g / m³. 2 The compacted density is 1.5 g / cm³. 3 The tortuosity τ of the negative electrode 8 is 1.7.

[0131] Negative electrode 9:

[0132] The negative electrode active material, conductive agent carbon black, thickener CMC and binder SBR are mixed in a mass ratio of 100:1:1.6:1.8. The mixed powder is placed in a homogenizer, and deionized water is added as a solvent to mix and stir evenly to obtain a negative electrode slurry. The negative electrode slurry is sieved (200 mesh screen) and coated onto the negative electrode current collector aluminum foil. A magnetic field of 0.8T is applied to the coating. After drying in an oven at 105℃, it is then rolled and slit to obtain the negative electrode sheet 9.

[0133] The negative electrode active material includes first graphite (secondary carbon-coated graphite particles) and second graphite (primary uncoated graphite particles), with a mass ratio of 50:50 between the first graphite and the second graphite.

[0134] The resulting negative electrode has a bifacial areal density of 200 g / m³. 2 The compacted density is 1.5 g / cm³. 3 The tortuosity τ of the negative electrode 9 is 1.5.

[0135] Electrolyte 1:

[0136] Electrolyte 1 was prepared by mixing lithium hexafluorophosphate (LiPF6), ethylene carbonate (EC), ethyl methyl carbonate (EMC), ethyl acetate (EA), vinylene carbonate (VC), and fluoroethylene carbonate (FEC) in a mass percentage ratio of 16%:50%:14%:10%:5%:5%. The conductivity σ of electrolyte 1 was 9.8 mS / cm.

[0137] Electrolyte 2:

[0138] Electrolyte 2 was prepared by mixing lithium hexafluorophosphate (LiPF6), ethylene carbonate (EC), ethyl methyl carbonate (EMC), ethyl acetate (EA), vinylene carbonate (VC), and fluoroethylene carbonate (FEC) in a mass percentage ratio of 16%:40%:14%:20%:5%:5%. The conductivity σ of electrolyte 2 was 11.5 mS / cm.

[0139] Electrolyte 3:

[0140] Electrolyte 3 was prepared by mixing lithium hexafluorophosphate (LiPF6), ethylene carbonate (EC), ethyl methyl carbonate (EMC), ethyl acetate (EA), vinylene carbonate (VC), and fluoroethylene carbonate (FEC) in a mass percentage ratio of 16%:30%:14%:30%:5%:5%. The conductivity σ of electrolyte 3 was 12.0 mS / cm.

[0141] Electrolyte 4:

[0142] Electrolyte 4 was prepared by mixing lithium hexafluorophosphate (LiPF6), ethylene carbonate (EC), ethyl methyl carbonate (EMC), ethyl acetate (EA), vinylene carbonate (VC), and fluoroethylene carbonate (FEC) in a mass percentage ratio of 16%:20%:9%:40%:5%:10%. The conductivity σ of electrolyte 4 was 12.3 mS / cm.

[0143] Electrolyte 5:

[0144] Electrolyte 5 was prepared by mixing lithium hexafluorophosphate (LiPF6), ethylene carbonate (EC), ethyl methyl carbonate (EMC), ethyl acetate (EA), vinylene carbonate (VC), and fluoroethylene carbonate (FEC) in a mass percentage ratio of 16%:10%:9%:50%:5%:10%. The conductivity σ of electrolyte 5 was 13.2 mS / cm.

[0145] Electrolyte 6:

[0146] Electrolyte 6 was prepared by mixing lithium hexafluorophosphate (LiPF6), ethylene carbonate (EC), ethyl methyl carbonate (EMC), ethyl acetate (EA), vinylene carbonate (VC), and fluoroethylene carbonate (FEC) in a mass percentage ratio of 18%:10%:7%:50%:5%:10%. The conductivity σ of electrolyte 6 was 14.0 mS / cm.

[0147] Electrolyte 7:

[0148] Electrolyte 7 was prepared by mixing lithium hexafluorophosphate (LiPF6), ethylene carbonate (EC), ethyl methyl carbonate (EMC), ethyl acetate (EA), vinylene carbonate (VC), and fluoroethylene carbonate (FEC) in a mass percentage ratio of 20%:10%:5%:50%:5%:10%. The conductivity σ of electrolyte 7 was 14.8 mS / cm.

[0149] Electrolyte 8:

[0150] Electrolyte 8 was prepared by mixing lithium hexafluorophosphate (LiPF6), ethylene carbonate (EC), ethyl acetate (EA), vinylene carbonate (VC), and fluoroethylene carbonate (FEC) in a mass percentage ratio of 20%:10%:55%:5%:10%. The conductivity σ of electrolyte 8 was 15.3 mS / cm.

[0151] Example 1:

[0152] Under dew point conditions, the positive electrode 1, separator (specifically a polyethylene film), and negative electrode 1 are stacked in sequence and repeated multiple times to obtain a battery cell. The separator must completely isolate the positive electrode 1 and the negative electrode 1. The stacked battery cell is then placed in an aluminum-plastic film soft package and injected with the electrolyte 1 mentioned above. A copper wire is placed as a reference electrode. The battery is formed and capacity tested at room temperature, and activated by charging and discharging with a small current for 3 cycles. After that, a lithium metal layer is plated onto the copper wire reference electrode with a small current to obtain a lithium-ion battery.

[0153] Examples 2-20: Same as Example 1, the main difference is that different negative electrode sheets and electrolytes are used to assemble the batteries, as shown in Table 1.

[0154] Comparative Examples 1-3: Same as Example 1, the main difference is that different negative electrode sheets and electrolytes are used to assemble the batteries, as shown in Table 1.

[0155] Table 1

[0156] Positive electrode sheet Negative electrode sheet Electrolyte Example 1 1 1 1 Example 2 1 2 3 Example 3 1 3 7 Example 4 1 4 8 Example 5 1 2 5 Example 6 1 5 2 Example 7 1 6 1 Example 8 1 7 1 Example 9 1 5 4 Example 10 1 7 3 Example 11 1 8 2 Example 12 1 9 1 Example 13 1 1 8 Example 14 1 5 6 Example 15 1 6 3 Example 16 1 7 5 Example 17 1 8 6 Example 18 1 8 7 Example 19 1 9 7 Example 20 1 9 8 Comparative Example 1 1 3 1 Comparative Example 2 1 4 3 Comparative Example 3 1 4 4

[0157] Performance testing:

[0158] (1) Electrolyte conductivity: The conductivity σ of the electrolyte was measured using a conductivity meter. The specific operating steps are as follows: ① Calibration: The instrument was calibrated using a standard KCl solution (e.g., 0.1 mol / L, σ = 12.88 mS / cm at 25℃); ② Sample preparation: The prepared electrolytes 1-8 were injected into a clean measuring cell, and air bubbles were removed; ③ The electrodes were immersed in the electrolyte and then placed in a 25℃ oven for 1 hour to maintain a constant temperature, avoiding temperature fluctuations; ④ Reading: The conductivity value after stabilization was read. The test results are shown in Table 2.

[0159] (2) Contact angle between the negative electrode and the electrolyte: The contact angle θ between the negative electrode and the electrolyte was measured using a contact angle measuring instrument. The specific operating steps are as follows: ① Sample preparation: The previously prepared negative electrode sheets 1-9 were cut into 10mm×10mm pieces and ultrasonically cleaned with anhydrous ethanol for 5 minutes; ② Droplet addition: 2μL of electrolyte 1-8 was added to the surface of the negative electrode sheet using a pipette; ③ Image acquisition: The droplet shape was captured using a high-speed camera (≥100fps) to ensure droplet stability (no evaporation or deformation within 5 seconds); ④ The droplet profile was fitted using the KrüssADVANCE software, and the contact angle between the negative electrode and the electrolyte was calculated. The test results are shown in Table 2.

[0160] (3) Torque of the negative electrode: The tortuosity τ of the negative electrode was measured using X-ray micro-CT. The specific steps are as follows: ① Sample preparation: The prepared negative electrode 1-9 were cut into cylinders with a diameter of 3mm to avoid structural damage; ② CT scan: Scanning was performed at 20kV to reconstruct the three-dimensional pore model; ③ Torque calculation: Where L effL0 represents the actual lithium-ion transport path (tracked using the maximum sphere algorithm to trace the pore path), and L0 is the apparent length in the electrode thickness direction. Test results are shown in Table 2.

[0161] (4) Average charging rate: The batteries assembled in Examples 1-20 and Comparative Examples 1-3 (with copper wire as a reference electrode) were formed and capacity tested at room temperature, and activated by three cycles of small current charge and discharge. Then, a lithium metal layer was deposited onto the copper wire reference electrode using a small current. After the above preparations, the fast charging capability of the above schemes was tested using the three-electrode method. A negative reference potential of 0mV was used as the lithium plating signal of the battery. Stepped constant current charging rates of 8C, 7C, 6C, 5C, 4C, 3C, 2C, 1C, and 0.5C were set, and the lithium plating boundary of the twenty-three schemes at different rates was tested. The average charging rate is the cumulative value of the product of the lithium plating boundary SOC and the corresponding charging rate for each interval. The performance test results are shown in Tables 2 and 3. Table 3 shows the lithium plating boundary SOC (%) of Examples 1-20 and Comparative Examples 1-3 at different charging rates.

[0162] Table 2

[0163]

[0164] Table 3

[0165]

[0166] As shown in Table 2, compared with Examples 1-12, Examples 13-20, with K values ​​satisfying 3-10, achieved an average charging rate of 6.0-6.8, enabling super-fast charging of the battery at ≥6C. This demonstrates that the electrolyte and negative electrode design method of this application, by adjusting the tortuosity of the negative electrode, the conductivity of the electrolyte, and the contact angle between the negative electrode and the electrolyte, enables the negative electrode and electrolyte to work synergistically to achieve fast charging targets of different rates for the entire battery system.

[0167] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A battery, characterized in that, The battery includes a negative electrode and an electrolyte, and the battery satisfies... 1≤K≤10, where σ represents the conductivity of the electrolyte in mS / cm; θ represents the contact angle between the negative electrode and the electrolyte in °; and τ represents the tortuosity of the negative electrode.

2. The battery according to claim 1, characterized in that, The conductivity of the electrolyte σ≥8mS / cm, and / or the contact angle θ between the negative electrode and the electrolyte ≤40°, and / or the tortuosity τ of the negative electrode ≤2.

5.

3. The battery according to claim 2, characterized in that, The conductivity σ of the electrolyte satisfies: 12mS / cm≤σ≤18mS / cm, and / or the contact angle θ between the negative electrode and the electrolyte satisfies: 10°≤θ≤30°, and / or the tortuosity τ of the negative electrode satisfies: 1.3≤τ≤1.

8.

4. The battery according to any one of claims 1-3, characterized in that, 3≤K≤10。 5. The battery according to any one of claims 1-4, characterized in that, The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material, which includes graphite. The graphite includes a first graphite and a second graphite. At least a portion of the surface of the first graphite is provided with a coating layer, and the surface of the second graphite is not provided with a coating layer.

6. The battery according to claim 5, characterized in that, The first graphite and the second graphite each comprise at least one of artificial graphite and natural graphite.

7. The battery according to claim 5 or 6, characterized in that, The mass ratio of the first graphite to the second graphite is (50-80):(20-50).

8. The battery according to any one of claims 5-7, characterized in that, The coating layer includes a carbon coating layer, which includes at least one of amorphous carbon, carbon nanotubes, and graphene.

9. The battery according to any one of claims 5-8, characterized in that, The first graphite is secondary carbon-coated graphite, and the second graphite is primary uncoated graphite.

10. The battery according to any one of claims 5-9, characterized in that, In the negative electrode active material layer, the mass ratio of the first graphite to the second graphite on the side closer to the negative electrode current collector is greater than the mass ratio of the first graphite to the second graphite on the side farther from the negative electrode current collector.

11. The battery according to claim 10, characterized in that, The negative electrode active material layer includes at least: A first negative electrode active material layer is disposed on the negative electrode current collector; The second negative electrode active material layer is disposed on the side of the first negative electrode active material layer away from the negative electrode current collector; The mass ratio of the first graphite to the second graphite in the first negative electrode active material layer is greater than the mass ratio of the first graphite to the second graphite in the second negative electrode active material layer.

12. The battery according to any one of claims 5-11, characterized in that, The negative electrode active material layer includes a conductive agent, which includes carbon black and / or carbon nanotubes.

13. The battery according to claim 12, characterized in that, The mass ratio of the negative electrode active material to the conductive agent is 100:(0.5-1.5).

14. The battery according to any one of claims 5-13, characterized in that, The areal density of the negative electrode active material layer is 135 g / m³. 2 ~320g / m 2 ; and / or, the compaction density of the negative electrode active material layer is 1.3 g / cm³. 3 ~1.9g / cm 3 .

15. The battery according to any one of claims 1-14, characterized in that, The battery further includes a positive electrode sheet, which 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 at least one of a layered structure positive active material, an olivine-type phosphate positive active material, and a spinel structure positive active material.

16. The battery according to claim 15, characterized in that, The positive electrode active material includes at least one of nickel-cobalt-manganese ternary positive electrode material, lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, spinel nickel manganese oxide, and lithium-rich spinel manganese oxide.

17. The battery according to any one of claims 1-16, characterized in that, The electrolyte comprises a lithium salt, which includes at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium difluorooxalateborate; and / or, the electrolyte comprises a solvent, which includes at least one of ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, ethyl acetate, methyl propionate, and ethyl propionate; and / or, the electrolyte comprises an additive, which includes at least one of vinylene carbonate, fluoroethylene carbonate, ethylene sulfate, fluoroethers, sulfur-based additives, and nitrile-based additives.

18. The battery according to claim 17, characterized in that, The lithium salt includes lithium hexafluorophosphate, the solvent includes at least one of ethylene carbonate, ethyl methyl carbonate and ethyl acetate, and the additive includes vinylene carbonate and / or fluoroethylene carbonate.

19. The battery according to claim 17 or 18, characterized in that, The mass percentages of the lithium salt, the solvent, and the additive are (15%-20%): (65%-75%): (10%-15%).

20. An electrical appliance, characterized in that, The electrical device includes the battery as described in any one of claims 1-19.

Images