Battery and preparation method thereof, method for evaluating flatness of battery, battery device and power utilization device

Abstract

The invention belongs to the technical field of batteries, and particularly relates to a battery and a preparation method thereof, a method for evaluating the flatness of the battery, a battery device and a power utilization device. Wherein PDI = (sigma / mu) 2 / [1 + (sigma / mu) 2], and sigma and mu are the standard deviation and the average value of the thickness data of the battery respectively. The battery has relatively high capacity and relatively good rate capability.

Description

Technical Field

[0001] This application relates to the field of batteries, specifically to batteries and their preparation methods, methods for evaluating battery flatness, battery devices, and electrical devices. Background Technology

[0002] In solid-state battery systems, ion transport at the solid-solid interface strongly depends on the contact stability between particles. When there are differences in the flatness of the battery surface, high-pressure regions (such as protrusions) and low-pressure regions (such as depressions) are generated under confinement force. For example, when a confinement force of 5 MPa is applied, the pressure difference between the two can reach 15 MPa, further causing uneven distribution of ion flux and current density, affecting the battery's capacity and rate performance. At the same time, in the low-pressure region, due to insufficient contact between particles, some active particles cannot participate in the electrochemical reaction, reducing the battery's capacity. Therefore, controlling the flatness of the battery within a certain range to avoid the above problems is one of the current challenges. Summary of the Invention

[0003] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, this invention proposes a battery with high surface flatness that can effectively utilize its capacity and rate performance, a method for preparing the battery, a method for evaluating battery flatness, a battery device, and an electrical device.

[0004] The first aspect of this application provides a battery. According to an embodiment of this application, the battery has a PDI ≤ 0.094%; wherein, PDI = ( s / μ) 2 / [1+( s / μ) 2 ], s μ and μ represent the standard deviation and average value of the battery thickness data, respectively. The thickness data includes multiple thickness values ​​corresponding to the surface lattice of at least one surface of the battery, and the dot density of the surface lattice is ≥0.1 dots / cm. 2 .

[0005] Specifically, the PDI value of the battery has been normalized and calculated based on the standard deviation (σ) and average value (μ) of the thickness data. This results in lower sensitivity to outliers and a better distinction between "normal fluctuations" and "severe unevenness." Meanwhile, the (σ / μ) component in the PDI... 2PDI (Polymer Density Dispersion) can amplify the contribution of high deviations, better meeting the actual needs of battery performance. It balances the shortcomings of "range" and "coefficient of variation (σ / μ)²", avoiding over-reliance on extreme values ​​or ignoring high deviations, and more accurately reflects the uniformity of battery thickness distribution to quantify battery flatness. By controlling PDI ≤ 0.094%, a uniform thickness distribution on the battery surface can be ensured, resulting in high flatness, reducing local high-resistivity areas, improving the utilization rate of active materials, and increasing battery capacity. Simultaneously, a high-flatness battery experiences uniform stress under constraint, promoting rapid transport of active ions and homogenizing ion flux, thus improving the battery's rate performance.

[0006] According to an embodiment of this application, the PDI of the battery is ≤0.088%.

[0007] According to an embodiment of this application, the dot density of the surface dot matrix is ​​1 dot / cm². 2 ~200 pieces / cm 2 .

[0008] According to an embodiment of this application, the battery includes two large surfaces and two narrow surfaces arranged opposite to each other, the area of ​​the large surfaces being larger than the area of ​​the narrow surfaces, and the surface dot matrix being located on at least one of the large surfaces of the battery.

[0009] According to an embodiment of this application, the distance between two adjacent points of the surface dot matrix does not exceed 1 cm.

[0010] A second aspect of this application provides a method for preparing the aforementioned battery. According to an embodiment of this application, the method includes: coating a positive electrode slurry onto at least one side of a positive electrode current collector to obtain a positive electrode sheet; coating a negative electrode slurry onto at least one side of a negative electrode current collector to obtain a negative electrode sheet; assembling the positive electrode sheet, a separator layer, and the negative electrode sheet to obtain the battery; the method satisfies at least one of the following conditions: the dyne value of the positive electrode current collector is 55 mN / m to 80 mN / m, specifically 72 mN / m to 80 mN / m; the dyne value of the negative electrode current collector is 40 mN / m to 65 mN / m, specifically 50 mN / m to 65 mN / m.

[0011] Specifically, the dyne value (surface energy) of the current collector directly affects the wettability and spreadability of the slurry on its surface. The slurry is prone to shrinkage or agglomeration on current collectors with low dyne values. Furthermore, due to inconsistent shrinkage rates during drying, the electrode may warp or crack locally. In subsequent stacking processes, the unevenness of the initially coated electrode will further accumulate, exacerbating the unevenness of the battery. This leads to stress concentration in high-pressure areas and unstable stress interface contact in low-pressure areas under constrained conditions, resulting in uneven stress distribution and ultimately affecting the battery's electrochemical performance. In the method described in this application, by controlling the dyne value of the current collector to meet the above requirements, slurry shrinkage or agglomeration can be appropriately suppressed, inhibiting significant unevenness of the electrode. Simultaneously, it prevents excessive extension to the edges, avoiding edge accumulation and unevenness caused by thick edges and thin centers, thus obtaining a battery with satisfactory flatness.

[0012] A third aspect of this application provides a method for evaluating the flatness of a battery. According to an embodiment of this application, the method includes: measuring the thickness of a surface dot matrix on at least one surface of the battery to obtain thickness data containing multiple thickness values, wherein the dot density of the surface dot matrix is ​​≥0.1 dots / cm². 2 Determine the mean μ and standard deviation of the thickness data. s If the battery satisfies PDI=( s / μ) 2 / [1+( s / μ) 2 If the flatness is ≤0.094%, the flatness of the battery is qualified; otherwise, the flatness of the battery is unqualified.

[0013] This method effectively captures battery surface smoothness. The battery's PDI value is normalized and calculated based on the standard deviation (σ) and mean (μ) of the thickness data. It has low sensitivity to outliers and can better distinguish between "normal fluctuations" and "severe unevenness." Simultaneously, the (σ / μ) in the PDI... 2 PDI (Polymer Density Dispersion) can amplify the contribution of high deviations, better meeting the actual needs of battery performance. It balances the shortcomings of "range" and "coefficient of variation (σ / μ)²", avoiding over-reliance on extreme values ​​or ignoring high deviations, and more accurately reflects the uniformity of battery thickness distribution to quantify battery flatness. Furthermore, by controlling PDI ≤ 0.094%, it ensures uniform thickness distribution on the battery surface, resulting in high flatness, reducing local high-resistivity areas, improving the utilization rate of active materials, and increasing battery capacity. Simultaneously, a high-flatness battery experiences uniform stress under constraint; this uniform pressure distribution reduces interfacial contact resistance, promotes rapid transport of active ions and homogenizes ion flux, improving the battery's rate performance.

[0014] According to an embodiment of this application, the thickness data is obtained by measuring with a coordinate measuring machine; and at least one of the following conditions is met: The coordinate measuring machine uses a dot matrix scanning method for measurement. The probe sampling interval of the coordinate measuring machine is 0.01cm~1cm; The probe moving speed of the coordinate measuring machine is 40~80mm / s; The accuracy of the coordinate measuring machine is ±2μm; The testing temperature of the coordinate measuring machine is 25℃.

[0015] In a fourth aspect, this application provides a battery device. According to an embodiment of this application, the battery device includes the battery described above. This battery device has good battery life and fast charging performance.

[0016] In a fifth aspect, this application provides an electrical device. According to embodiments of this application, the electrical device includes the battery or battery device described above. This electrical device has good battery life and fast charging performance. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of a solid-state battery according to an embodiment of this application.

[0018] Figure label: 10: Large surface area; 20: Overhang area; 30: Positive electrode tab; 40: Negative electrode tab. Detailed Implementation

[0019] The embodiments of the present invention are described in detail below. These embodiments are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0020] This application is based on the inventor's discoveries and understanding of the following facts and problems: Because battery slurries need to disperse solid electrolytes, their viscosity is typically higher than that of liquid battery slurries. High-viscosity slurries are prone to a "shear-thinning" effect during coating, resulting in poor wettability and spreadability. This leads to uneven flow rates at the transfer roller gaps, causing thickness fluctuations. Simultaneously, the slurry is prone to shrinkage or agglomeration, resulting in significant unevenness on the electrode sheets. In subsequent stacking processes, the unevenness of the initially coated electrode sheets is further amplified, exacerbating the overall unevenness of the battery.

[0021] Uneven batteries, when operating under constrained conditions, experience uneven stress. Specifically, in areas of lower pressure, the solid electrolyte and electrode particles do not make sufficient contact at grain boundaries, resulting in high internal porosity and obstructed active ion transport pathways. This leads to a significant increase in impedance in these areas, low utilization of active materials, and reduced battery capacity. Furthermore, the obstructed active ion transport pathways within the battery further increase polarization impedance under high current operation, severely impacting the battery's rate performance.

[0022] Therefore, establishing a reasonable and accurate standard for flatness measurement is crucial to ensuring battery reliability. Through in-depth research and molecular analysis, the inventors have proposed a battery flatness measurement index and control standard based on the PDI value. Batteries that meet the PDI value requirements exhibit higher capacity and better rate performance.

[0023] In view of this, a first aspect of this application provides a battery. According to an embodiment of this application, the battery has a PDI ≤ 0.094%; wherein, PDI = ( s / μ) 2 / [1+( s / μ) 2 ], s μ and μ represent the standard deviation and average value of the battery thickness data, respectively. The thickness data includes multiple thickness values ​​corresponding to the surface lattice of at least one surface of the battery, and the dot density of the surface lattice is ≥0.1 dots / cm. 2 .

[0024] Specifically, the PDI value of the battery has been normalized and calculated based on the standard deviation (σ) and average value (μ) of the thickness data. This results in lower sensitivity to outliers and a better distinction between "normal fluctuations" and "severe unevenness." Meanwhile, the (σ / μ) component in the PDI... 2 It can amplify the contribution of high deviations, which is more in line with the actual needs of battery performance. PDI balances the defects of "range" and "coefficient of variation (σ / μ)²", avoids over-reliance on extreme values ​​or ignoring high deviations, and can more accurately reflect the uniformity of battery thickness distribution to quantify the flatness of the cell. By controlling PDI ≤ 0.094% (specifically within the range of 0.094%, 0.090%, 0.085%, 0.082%, 0.080%, 0.075%, 0.070%, 0.065%, 0.060%, 0.055%, 0.050%, 0.045%, 0.040%, 0.035%, 0.030%, or any two of these ranges), a uniform thickness distribution on the battery surface can be ensured, resulting in high flatness. This reduces localized high-resistance areas, improves the utilization rate of active materials, and increases battery capacity. Simultaneously, a battery with high flatness experiences uniform stress under constrained conditions. This uniform pressure distribution reduces interfacial contact resistance, promotes rapid transport of active ions, and homogenizes ion flux, thereby enhancing the battery's rate performance.

[0025] In some embodiments, controlling the PDI of the battery to ≤0.094% can ensure that the battery capacity is ≥190mAh g. -1 The 0.5C / 0.1C discharge capacity ratio is ≥62%.

[0026] According to an embodiment of this application, the PDI of the battery is ≤0.088%. This further improves the flatness of the battery, which in turn is more conducive to the battery's performance and enhances its overall performance.

[0027] It is understandable that the more thickness data of the battery, the higher the dot density of the surface lattice, and the more accurately the PDI value of the battery can reflect its flatness. In some embodiments, the dot density of the surface lattice is ≥1 dot / cm². 2 As an example, the point density can be 1 point / cm². 2 ~200 pieces / cm 2 Specifically, such as 1 per cm 2 10 pieces / cm 2 20 pieces / cm 2 50 pieces / cm 2 80 pieces / cm 2 100 pieces / cm 2 120 pieces / cm 2 150 pieces / cm 2 180 pieces / cm 2 200 pieces / cm 2 Or the range between either or both. This allows for accurate reflection of the battery's flatness and facilitates measurement.

[0028] According to embodiments of this application, the thickness can be tested at any location on the battery, meaning the surface dot matrix can be located at any position on the battery surface. In some embodiments, the battery includes two large surfaces (referring to the rectangular main area on the electrode sheet coated with electrode material, i.e., the core working area after removing special structures such as tabs, empty foil areas, and overhang areas) and two narrow surfaces arranged opposite each other. The area of ​​the large surfaces is larger than the area of ​​the narrow surfaces, and the surface dot matrix is ​​located on at least one large surface of the battery. This allows for better removal of abnormal data, avoidance of interference from abnormal points, and facilitates measurement. In some embodiments, if the overhang area is filled flat, the large surface can extend to the overhang area, i.e., include the overhang area.

[0029] In some embodiments, the battery includes an electrode core and a casing (e.g., an aluminum-plastic film). The thickness test can be performed on the surface of the electrode core (i.e., the surface dot matrix is ​​located on the surface of the electrode core) or on the surface of the casing (i.e., the surface dot matrix is ​​located on the surface of the casing). As an example, Figure 1The battery surface 10 is shown (including the overhang area 20).

[0030] It is understandable that the dots in the surface dot matrix should be distributed as evenly as possible on the battery surface; the higher the dot density, the more accurate the test results. The specific test area and dot density can be flexibly selected according to actual needs. In some embodiments, the distance between two adjacent dots in the surface dot matrix is ​​0.01cm to 1cm, specifically such as 0.01cm, 0.05cm, 0.10cm, 0.20cm, 0.30cm, 0.40cm, 0.50cm, 0.60cm, 0.70cm, 0.80cm, 0.90cm, 1cm, or any range between two of these. Therefore, with a suitable dot density, thickness data for the battery surface area can be collected in most cases.

[0031] According to the embodiments of this application, it can be understood that there is no particular limitation on the specific type of battery, which can be a primary battery or a secondary battery; the shape of the battery can be a square battery, and according to the outer packaging, the battery can be a hard-shell battery, a soft-pack battery, etc.

[0032] In some embodiments, the battery may include a positive electrode, a negative electrode, a separator, and an outer packaging. The positive electrode, negative electrode, and separator can be manufactured into a cell using a winding or stacking process, and the cell can be housed in the outer packaging. The positive and negative electrode sheets are alternately stacked, and the separator is disposed between adjacent positive and negative electrode sheets.

[0033] In some embodiments, the positive electrode sheet includes a positive current collector and a positive electrode material layer disposed on at least one side of the positive current collector. In some embodiments, the positive electrode material layer may include a positive electrode binder, a positive electrode conductive agent, and a positive electrode active material, and may also include additives with specific functions and effects, such as thickeners, sodium supplements, film-forming additives, flame retardants, high-temperature / low-temperature stabilizers, etc., as needed.

[0034] In some embodiments, the positive current collector 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 substrate and a metal layer formed on at least one surface of the polymer material substrate. Composite current collectors can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0035] As an example, positive electrode active materials may include lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium manganese oxide, nickel-cobalt-manganese ternary materials, nickel-cobalt-aluminum ternary materials, lithium iron phosphate, lithium nickel manganese oxide, lithium-rich manganese-based materials, or positive electrode active materials commonly used in the art.

[0036] As an example, the positive electrode binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), hydrogenated nitrile butadiene rubber (HNBR), ethylene-tetrafluoroethylene-propylene terpolymer, ethylene-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0037] As an example, the positive electrode 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.

[0038] In some embodiments, the negative electrode sheet may include a negative electrode current collector and a negative electrode material layer disposed on at least one side of the negative electrode current collector.

[0039] As an example, the negative electrode material layer may include a negative electrode active material, a thickener, a negative electrode conductive agent, and a negative electrode binder.

[0040] According to embodiments of this application, the negative electrode current collector can be a metal foil, such as copper foil, carbon-coated copper foil, etc.

[0041] According to embodiments of this application, the negative electrode active material may include graphite, silicon-carbon materials, silicon-oxygen materials, elemental silicon, etc.

[0042] According to embodiments of this application, the negative electrode binder may include, but is not limited to, polyvinylidene fluoride (PVDF) and sodium carboxymethyl cellulose (CMC). At least one of Na, polyvinylpyrrolidone, polytetrafluoroethylene, styrene-butadiene rubber (SBR), and hydrogenated nitrile butadiene rubber (HNBR).

[0043] According to embodiments of this application, the negative electrode conductive agent may include, but is not limited to, conductive carbon black, Super C. At least one of acetylene black, Ketjen black, and carbon nanofibers.

[0044] According to embodiments of this application, the separator layer can be a membrane or an electrolyte layer. Specifically, the electrolyte layer can include a solid electrolyte, and the type of solid electrolyte is not particularly limited, including but not limited to sulfide electrolytes, oxide electrolytes, etc.

[0045] A second aspect of this application provides a method for preparing the aforementioned battery. According to an embodiment of this application, the method includes: coating a positive electrode slurry onto at least one side of a positive electrode current collector to obtain a positive electrode sheet; coating a negative electrode slurry onto at least one side of a negative electrode current collector to obtain a negative electrode sheet; assembling the positive electrode sheet, a separator layer, and the negative electrode sheet to obtain the battery; the method satisfies at least one of the following conditions: the dyne value of the positive electrode current collector is 55 mN / m to 80 mN / m, specifically 72 mN / m to 80 mN / m, more specifically... The dyne value of the negative electrode current collector is 40mN / m to 65mN / m, specifically 50mN / m to 65mN / m, more specifically 40mN / m, 45mN / m, 50mN / m, 55mN / m, 60mN / m, 65mN / m, or any two of these values.

[0046] Specifically, the dyne value (surface energy) of the current collector directly affects the wettability and spreadability of the slurry on its surface. The slurry is prone to shrinkage or agglomeration on current collectors with low dyne values. Furthermore, due to inconsistent shrinkage rates during drying, the electrode may warp or crack locally. In subsequent stacking processes, the unevenness of the initially coated electrode will further accumulate, exacerbating the unevenness of the battery. This leads to stress concentration in high-pressure areas and unstable stress interface contact in low-pressure areas under constrained conditions, resulting in uneven stress distribution and ultimately affecting the battery's electrochemical performance. The method described in this application, by controlling the dyne value of the current collector to meet the above requirements, can appropriately suppress slurry shrinkage or agglomeration, inhibiting significant unevenness of the electrode. Simultaneously, it prevents excessive extension to the edges, avoiding edge accumulation and unevenness characterized by thick edges and a thin center, thus obtaining a battery with satisfactory flatness.

[0047] According to embodiments of this application, the solid content of the positive electrode slurry is 70% to 80%, specifically 70%, 72%, 74%, 76%, 78%, 80%, or any range between two of these. This facilitates coating and film formation, and results in a film layer with high flatness, thereby improving the flatness of the battery.

[0048] According to embodiments of this application, the fineness of the positive electrode slurry is 10μm to 15μm, specifically 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, or any range between two of these. This improves the flatness of the battery, thereby enhancing its capacity and rate performance.

[0049] According to an embodiment of this application, the positive electrode slurry has a 50s... -1The viscosity is 300 mPa·s to 800 mPa·s, specifically 300 mPa·s, 400 mPa·s, 500 mPa·s, 600 mPa·s, 700 mPa·s, 800 mPa·s, or any two of these ranges. Therefore, the above viscosity is beneficial for the formation of the cathode slurry film, and the resulting film has high flatness, which in turn helps improve the flatness of the battery.

[0050] In this article, 50s -1 Viscosity refers to the viscosity at a shear rate of 50 s / s. -1 The viscosity of a fluid is measured under the following conditions. It can be measured using a cone-plate viscometer or similar device.

[0051] According to an embodiment of this application, the bifacial areal density of the positive electrode is 420 g·m³. -2 ~450g·m -2 Specifically, such as 420g·m -2 425g·m -2 430g·m -2 435g·m -2 440g·m -2 445g·m -2 450g·m -2 Or a range between or any two of them. Therefore, the aforementioned areal density helps improve the flatness of the positive electrode sheet, thereby improving the flatness of the battery.

[0052] According to embodiments of this application, the solid content of the negative electrode slurry is 40% to 50%, specifically 40%, 42%, 44%, 46%, 48%, 50%, or any range between two of these. This facilitates coating and film formation, and results in a film layer with high flatness, thereby improving the flatness of the battery.

[0053] According to embodiments of this application, the fineness of the negative electrode slurry is 5μm to 10μm, specifically 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, or any range between two of these. This improves the flatness of the battery, thereby enhancing its capacity and rate performance.

[0054] According to an embodiment of this application, the negative electrode slurry has a 50s... -1 The viscosity ranges from 100 mPa·s to 500 mPa·s, specifically 100 mPa·s, 150 mPa·s, 200 mPa·s, 250 mPa·s, 300 mPa·s, 350 mPa·s, 400 mPa·s, 450 mPa·s, 500 mPa·s, or any combination thereof. Therefore, the above viscosity is beneficial for the formation of the negative electrode slurry film, and the resulting film has high flatness, which in turn helps improve the flatness of the battery.

[0055] According to an embodiment of this application, the double-sided areal density of the negative electrode is 170 g·m³. -2 ~190g·m -2 Specifically, such as 170g·m -2 172g·m -2 175g·m -2 178g·m -2 180g·m -2 182g·m -2 185g·m -2 188g·m -2 190g·m -2 Or a range between or any two of them. Therefore, the aforementioned areal density helps improve the flatness of the negative electrode sheet, thereby improving the flatness of the battery.

[0056] In one specific implementation, solid-state batteries can be prepared using the following method: (1) Preparation of positive electrode sheet: The positive electrode active material, positive electrode conductive agent and positive electrode binder are dispersed in a solvent to form a positive electrode slurry; the positive electrode slurry is coated on both sides of the positive electrode current collector, dried, rolled and cut to obtain the positive electrode sheet; (2) Preparation of negative electrode sheet: The negative electrode active material, negative electrode conductive agent and negative electrode binder are dispersed in a solvent to form a negative electrode slurry. The negative electrode slurry is coated on one side of the negative electrode current collector. Ceramic particles and binder are dispersed in a solvent to form a ceramic slurry. The ceramic slurry is coated on the other side of the negative electrode current collector. After drying, rolling and cutting, the negative electrode sheet is obtained. (3) Preparation of solid electrolyte layer: The solid electrolyte and binder are dispersed in a solvent to form a solid electrolyte layer slurry. The solid electrolyte layer slurry is coated on the substrate and dried to form a solid electrolyte layer.

[0057] (4) The solid electrolyte layer is transferred from the substrate surface to the surface of the negative electrode sheet, including the negative electrode active material layer.

[0058] (5) Battery assembly: The negative electrode and positive electrode, including the solid electrolyte layer, are stacked alternately, with the solid electrolyte layer located between the negative electrode and the positive electrode, and the negative electrode located on the outermost side of the battery. After encapsulation, isostatic pressing is performed to obtain a solid battery.

[0059] A third aspect of this application provides a method for evaluating the flatness of a battery. According to an embodiment of this application, the method includes: measuring the thickness of a surface dot matrix on at least one surface of the battery to obtain thickness data containing multiple thickness values, wherein the dot density of the surface dot matrix is ​​≥0.1 dots / cm². 2 Determine the mean μ and standard deviation of the thickness data. sIf the battery satisfies PDI=( s / μ) 2 / [1+( s / μ) 2 If the flatness is ≤0.094%, the flatness of the battery is qualified; otherwise, the flatness of the battery is unqualified.

[0060] This method effectively captures battery surface smoothness. The battery's PDI value is normalized and calculated based on the standard deviation (σ) and mean (μ) of the thickness data. It has low sensitivity to outliers and can better distinguish between "normal fluctuations" and "severe unevenness." Simultaneously, the (σ / μ) in the PDI... 2 PDI (Polymer Density Dispersion) can amplify the contribution of high deviations, better meeting the actual needs of battery performance. It balances the shortcomings of "range" and "coefficient of variation (σ / μ)²", avoiding over-reliance on extreme values ​​or ignoring high deviations, and more accurately reflects the uniformity of battery thickness distribution to quantify battery flatness. Furthermore, by controlling PDI ≤ 0.094%, it ensures uniform thickness distribution on the battery surface, resulting in high flatness, reducing local high-resistivity areas, improving the utilization rate of active materials, and increasing battery capacity. Simultaneously, a high-flatness battery experiences uniform stress under constraint; this uniform pressure distribution reduces interfacial contact resistance, promotes rapid transport of active ions and homogenizes ion flux, improving the battery's rate performance.

[0061] According to embodiments of this application, the thickness data can be obtained by using a coordinate measuring machine (CMM). It is understood that this application does not particularly limit the specific measurement method, and it can be performed according to the operating instructions of the CMM.

[0062] In some embodiments, the coordinate measuring machine uses a dot-matrix scanning method. This facilitates the acquisition of more measurement data, thereby improving the accuracy of the measurement results.

[0063] In some embodiments, the probe sampling interval of the coordinate measuring machine is 0.01cm to 1cm. This results in a suitable sampling density, which can accurately reflect the flatness of the battery while facilitating measurement.

[0064] In some embodiments, the probe movement speed of the coordinate measuring machine is 40 mm / s to 80 mm / s. This allows for both measurement efficiency and accuracy.

[0065] In some embodiments, the coordinate measuring machine has an accuracy of ±2 μm. This results in more accurate test results.

[0066] In some embodiments, the coordinate measuring machine is tested at a temperature of 25°C. This facilitates operation.

[0067] In some embodiments, the solid-state battery is placed vertically and fixed, and a coordinate measuring machine probe is adjusted to contact the battery surface to perform a flatness scan of the matrix. The probe sampling interval is 0.05 mm, the moving speed is 60 mm / s, the accuracy is ±2 μm, the test temperature is 25℃, the thickness data of all matrix points is recorded, and the PDI is calculated using the following formula:

[0068] Where σ and μ are the standard deviation and average value of the thickness of all lattice points on the battery surface, respectively.

[0069] In a fourth aspect, this application provides a battery device. According to an embodiment of this application, the battery device includes the battery described above. This battery device has good battery life and fast charging performance.

[0070] According to embodiments of this application, the battery device can be a battery pack, a battery module, a chassis (e.g., a CTC integrated chassis, a skateboard chassis, etc.).

[0071] According to an embodiment of this application, the battery pack includes a plurality of batteries that can be stacked or disposed within a housing; the battery pack includes a housing, within which a plurality of batteries or at least one battery pack is disposed; the chassis includes a chassis frame, within which a plurality of batteries or at least one battery pack or at least one battery pack is disposed.

[0072] In a fifth aspect, this application provides an electrical device. According to embodiments of this application, the electrical device includes the battery or battery device described above. This electrical device has good battery life and fast charging performance.

[0073] According to embodiments of this application, the specific type of electrical device is not particularly limited and can be any device that uses a battery or battery device as a power source or energy storage unit. As examples, electrical devices include, but are not limited to, electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), mobile terminals (e.g., mobile phones, laptops, game consoles, wearable devices, etc.), drones, aerospace equipment, satellites, ships, energy storage systems, etc.

[0074] It is understood that, in addition to the battery or battery device mentioned above, the electrical device also includes necessary structures and components, all of which can be made with reference to conventional technologies. For example, an electric vehicle may include a body, chassis, tires, navigation system, radar system, steering system, braking system, lubrication system, cooling system, driving system, etc., which will not be described in detail here.

[0075] The embodiments of this application are described in detail below.

[0076] Example 1 Solid-state battery fabrication: (1) Pure silicon, conductive agent acetylene black, and binder CMC were dispersed in water at a mass ratio of 97.5:0.5:2 to obtain a solid content of 42%, a fineness of 8μm, and a 50s s content of 50μm. -1 A negative electrode slurry with a viscosity of 300 mPa·s was coated onto both sides of a copper foil current collector with a dyne value of 51 mN / m. After drying and rolling, a layer of negative electrode active material was formed, resulting in a negative electrode sheet with a double-sided areal density of 180 g·m³. -2 .

[0077] The positive electrode active material, single-crystal ternary NCM811, the conductive agent, acetylene black, and the binder, HNBR, were dispersed in xylene solvent at a mass ratio of 94.5:0.5:5 to obtain a solid content of 75%, a fineness of 12 μm, and a 50s solids content. -1 A positive electrode slurry with a viscosity of 500 mPa·s was coated onto both sides of a positive electrode current collector aluminum foil with a dyne value of 72 mN / m using a single-layer coating method. After drying and rolling, a positive electrode sheet was obtained with a double-sided areal density of 425 g·m³. -2 .

[0078] The sulfide electrolyte Li6PS5Cl (LPSCl) and binder SBR are dispersed in xylene solvent at a mass ratio of 99:1 to obtain a solid electrolyte layer slurry with a solid content of 60%. The solid electrolyte layer slurry is coated on the surface of an aluminum foil substrate and dried to form a solid electrolyte layer. The solid electrolyte layer is then transferred from the aluminum foil substrate to the surface of the active material layer of the negative electrode.

[0079] A negative electrode sheet including a solid electrolyte layer, a positive electrode sheet, and another negative electrode sheet including a solid electrolyte layer are stacked sequentially, with the solid electrolyte layer located between the negative electrode sheet and the positive electrode sheet to obtain an electrode assembly. The electrode assembly is then packaged in an aluminum-plastic film and subjected to isostatic pressing at 80°C and 500 MPa to obtain a solid-state battery.

[0080] Examples 2-7, Comparative Examples 1-2 The preparation method is basically the same as that of the solid-state battery in Example 1. The difference lies in the coating method and areal density of the positive / negative electrodes, as detailed in Table 1.

[0081] Table 1

[0082] Performance testing: 1. Slurry fineness: Drop a small amount of slurry onto the deeper end of the fineness tester groove. Hold the scraper and scrape the slurry from the deeper part of the groove to the shallower part at a uniform speed, so that the slurry fills the groove and is leveled. The position where obvious particle aggregation or scratches first appear in the groove is taken as the fineness value. The same slurry should be tested at least 3 times and the average value should be taken.

[0083] 2. Slurry 50s -1 Viscosity: The slurry was dropped onto the disk of the rotary viscometer. The test was started with the rotor rotating at 50 rpm. The rotor was vertically immersed in the slurry sample cup up to the designated mark. After the reading stabilized, the data was recorded, and the slurry 50s sample was obtained. -1 Viscosity value.

[0084] 3. Areal density: At different positions in the transverse (perpendicular to the coating direction) and longitudinal direction of the electrode, punching machines are used to punch out electrode discs and foil discs with a diameter of 18mm. At least 20 electrode discs are punched out. The mass of each individual electrode disc and foil disc is weighed, and the average value is calculated using the formula: areal density (g / m²) = [mass of electrode disc (g) - mass of foil disc (g)] / disc area (m²). This average value is the electrode areal density.

[0085] 4. Flatness test of solid-state batteries: The solid-state battery was placed vertically and fixed in place. The probe of the coordinate measuring machine was adjusted to contact the surface of the solid-state battery, and the flatness of the dot matrix was scanned. The probe sampling interval was 0.05 mm, and the dot density was 120 dots / cm². 2 The moving speed is 60 mm / s, the accuracy is ±2 μm, the test temperature is 25℃, the X / Y / Z axis travel distance is ≥500×600×400 mm, the thickness data of all matrix points are recorded, and the distribution coefficient PDI is calculated using the following formula:

[0086] Where σ and μ are the standard deviation and average value of the thickness of all lattice points on the battery surface, respectively.

[0087] 5. Electrical performance testing of solid-state batteries: Five solid-state batteries from each embodiment and comparative example were taken and tested in the Ruineng secondary battery performance testing cabinet. The solid-state batteries were charged to 4.2V at 0.1C and discharged to 2.0V at 0.1C. The specific capacity of the positive electrode was calculated and recorded as Q1. Then, the batteries were charged to 2.0V at 0.5C and discharged to 2.0V at 0.1C. The specific capacity of the positive electrode was calculated and recorded as Q2. The discharge capacity at 0.5C / 0.1C is Q1 / Q2×100% and recorded as the rate performance.

[0088] Table 2

[0089] The data above shows that the higher the PDI value, the worse the flatness. However, when the PDI is controlled to be no greater than 0.094%, the battery has higher flatness and better capacity and rate performance.

[0090] Furthermore, as can be seen from Examples 1-3, when the dyne value of the positive electrode aluminum foil is fixed, the closer the dyne value of the negative electrode copper foil is to the boundary value, the larger the PDI value of the battery and the worse the flatness. Similarly, as can be seen from Examples 1, 4, and 5, when the dyne value of the negative electrode copper foil is fixed, the closer the dyne value of the positive electrode aluminum foil is to the boundary value, the larger the PDI value of the battery, the worse the flatness, the worse the uniformity of force distribution, the lower the capacity utilization, and the worse the rate performance. Comparing Examples 1-5 and Example 6, it can be seen that when the dyne values ​​of the positive and negative electrode current collectors are closer to the middle of the value range... The lower the PDI (Power Difference Indicator) value of the battery, the better the flatness and the more significantly the electrical performance is enhanced. This is because when the current collector dyne value is low, the slurry is prone to shrinkage or agglomeration, which can easily lead to unevenness of the electrode. When the current collector dyne value is high, the slurry may extend excessively to the edge of the current collector surface, resulting in edge accumulation and an unevenness that is thicker at the edge and thinner in the middle. Therefore, a current collector dyne value of 50mN / m to 65mN / m for the negative electrode and a current collector dyne value of 72mN / m to 80mN / m for the positive electrode results in higher flatness and better battery performance in solid-state batteries.

[0091] Comparing Examples 1 and 7, it can be seen that, within a suitable range, selecting a current collector with a high dyne value is more effective in improving battery flatness than selecting a current collector with a low dyne value. However, compared to Comparative Examples 1-2, it can be seen that using positive and negative current collectors with excessively high or low dyne values ​​significantly increases the battery flatness PDI value, resulting in poor flatness and poor electrical performance.

[0092] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0093] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A battery, characterized in that, The battery's PDI is ≤ 0.094%; where PDI = ( σ / μ) 2 / [1+( σ / μ) 2 ], σ μ and μ represent the standard deviation and average value of the battery thickness data, respectively. The thickness data includes multiple thickness values ​​corresponding to the surface lattice of at least one surface of the battery, and the dot density of the surface lattice is ≥0.1 dots / cm. 2 .

2. The battery according to claim 1, characterized in that, The battery's PDI is ≤0.088%.

3. The battery according to claim 1 or 2, characterized in that, The dot density of the surface lattice is 1 dot / cm². 2 ~200 pieces / cm 2 .

4. The battery according to any one of claims 1 to 3, characterized in that, It includes two large surfaces and two narrow surfaces arranged opposite each other, the area of ​​the large surfaces is larger than the area of ​​the narrow surfaces, and the surface dot matrix is ​​located on at least one of the large surfaces of the battery.

5. The battery according to any one of claims 1 to 4, characterized in that, The distance between any two adjacent points of the surface dot matrix does not exceed 1 cm.

6. A method for preparing the battery according to any one of claims 1 to 5, characterized in that, include: A positive electrode slurry is coated on at least one side of a positive electrode current collector to obtain a positive electrode sheet; A negative electrode slurry is coated on at least one side of a negative electrode current collector to obtain a negative electrode sheet; The positive electrode, the separator layer, and the negative electrode are assembled to obtain the battery. The method satisfies at least one of the following conditions: The dyne value of the positive electrode current collector is 55mN / m~80mN / m; The dyne value of the negative electrode current collector is 40mN / m to 65mN / m.

7. The method according to claim 6, characterized in that, At least one of the following conditions must be met: The dyne value of the positive electrode current collector is 72mN / m~80mN / m; The dyne value of the negative electrode current collector is 50mN / m to 65mN / m.

8. A method for evaluating battery flatness, characterized in that, include: The thickness of the surface lattice on at least one surface of the battery is measured to obtain thickness data containing multiple thickness values, wherein the dot density of the surface lattice is ≥0.1 dots / cm. 2 ; Determine the mean μ and standard deviation of the thickness data. σ ; If the battery satisfies PDI=( σ / μ) 2 / [1+( σ / μ) 2 If the flatness is ≤0.094%, the flatness of the battery is qualified; otherwise, the flatness of the battery is unqualified.

9. The method according to claim 8, characterized in that, The thickness data is obtained by measuring with a coordinate measuring machine; and at least one of the following conditions is met: The coordinate measuring machine uses a dot matrix scanning method for measurement. The probe sampling interval of the coordinate measuring machine is 0.01cm~1cm; The probe moving speed of the coordinate measuring machine is 40~80mm / s; The accuracy of the coordinate measuring machine is ±2μm; The testing temperature of the coordinate measuring machine is 25℃.

10. A battery device, characterized in that, The battery includes any one of claims 1 to 5.

11. An electrical appliance, characterized in that, Includes the battery according to any one of claims 1 to 5 or the battery device according to claim 10.

Images