Lithium ion battery and electric device

Abstract

The invention belongs to the technical field of batteries, and discloses a lithium ion battery and a power utilization device. The lithium ion battery comprises a positive plate, the positive plate comprises a positive current collector and a positive dressing layer arranged on the surface of at least one side of the positive current collector, and the lithium ion battery meets the following conditions: a / b = 0.5-1.5; wherein a represents the elongation percentage of the positive electrode current collector with the unit of%, and b represents the elongation percentage of the positive electrode dressing layer with the unit of%. The lithium ion battery has excellent energy density.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of batteries, and in particular relates to a lithium ion battery and a power utilization device. BACKGROUND

[0002] With more and more consumers concerned about the cruising range of electric vehicles, automobile manufacturers also regard the battery cruising range as one of the core evaluation indexes, and the most direct and effective technical path is to improve the energy density of the battery. In order to realize the high volumetric energy density of the battery, a positive plate with a high tap density needs to be used. However, the high tap density (such as LFP≥2.6 g / cm3) and high areal density (LFP≥215 g / m2) of the positive plate will cause a series of problems in the battery preparation process. For example, the high areal density positive plate is prone to breakage during cold pressing, and the electrolyte is difficult to be uniformly injected, which will affect the energy density of the battery. Therefore, how to further improve the energy density of the battery is one of the challenges at present. SUMMARY

[0003] The present application aims to at least partially solve one of the technical problems in the related art. To this end, the present application proposes a lithium ion battery and a power utilization device, the lithium ion battery having a high energy density.

[0004] In a first aspect of the present application, a lithium ion battery is provided, comprising a positive plate, the positive plate comprising a positive current collector and a positive coating layer arranged on at least one side surface of the positive current collector, the lithium ion battery satisfying a / b=0.5~1.5. wherein a represents the elongation of the positive current collector, and b represents the elongation of the positive coating layer.

[0005] In the present application, by limiting the ratio of the elongation of the positive current collector and the positive coating layer to 0.5~1.5, i.e., limiting the elongation of the positive current collector to be within 50%~150% of the elongation of the positive coating layer. That is, by adjusting the elongation of the two, the elongation of the positive current collector and the positive coating layer is adapted, and when cold pressing is performed, the elongation of the two is basically equivalent, thereby reducing the risk of fracture of the positive coating layer.

[0006] In addition, the lithium ion battery according to the above embodiments of the present application can also have the following additional technical features: In some embodiments of the present application, a / b=0.5~0.7. Thus, it is helpful to further improve the adaptability of the elongation of the positive current collector and the positive coating layer, thereby reducing the risk of fracture of the positive coating layer when cold pressing is performed.

[0007] In some embodiments of the present application, at least one of the following conditions is satisfied: a is 1%~1.5%; b is 1% to 2%.

[0008] In some embodiments of the present application, the lithium ion battery further comprises a separator, the separator comprises a base film and a ceramic layer arranged on at least one side of the base film, and a colloidal particle layer is arranged on the surface of the ceramic layer away from the base film, and the separator satisfies: c / d = 0.1 to 0.2, wherein c represents the thickness of the colloidal particle layer, in units of microns, and d represents the total thickness of the base film and the ceramic layer, in units of microns. In this way, not only can the stress between high-pressed electrode sheets be buffered, but also the electrolyte can be fully infiltrated into the separator, ensuring the conduction efficiency of ions.

[0009] In some embodiments of the present application, at least one of the following conditions is satisfied: The base film comprises at least one of a polypropylene base film, a polyethylene base film, and a polypropylene and polyethylene composite base film; The colloidal particle layer comprises at least one of polyacrylate and its copolymer, polymethyl methacrylate and its copolymer, and polyvinylidene fluoride and its copolymer.

[0010] In some embodiments of the present application, the lithium ion battery further comprises an electrolyte, and the electrolyte satisfies at least one of the following conditions: The viscosity of the electrolyte is 5 mPa·s to 10 mPa·s; The ionic conductivity of the electrolyte is about 13 Ms / cm to 15 Ms / cm.

[0011] In some embodiments, the electrolyte comprises a lithium salt, a solvent, and an additive, and at least one of the following conditions is satisfied: The solvent comprises ethylene carbonate, methyl ethyl carbonate, and dimethyl carbonate, and the mass ratio of the ethylene carbonate, the methyl ethyl carbonate, and the dimethyl carbonate is 0.5 to 1.5: 2 to 3: 2 to 3; The lithium salt comprises at least one of LiPF6, LiFSI, LiTFSI, LiOTF, LiBF4, LiAsF6, and LiClO4; The additive comprises at least one of vinylene carbonate, fluoroethylene carbonate, vinyl sulfate, methylene methane disulfonate, siloxane additive, lithium bisoxalate borate, lithium difluorophosphate, lithium difluoro oxalate borate, and lithium nitrate.

[0012] In some embodiments of the present application, at least one of the following conditions is satisfied: The positive electrode coating layer comprises a positive electrode binder, and the positive electrode binder comprises modified polyvinylidene fluoride, and the modified polyvinylidene fluoride comprises at least one of an oxygen-containing group and a nitrogen-containing group; The thickness of the positive electrode current collector is 4 microns to 5 microns.

[0013] In some embodiments of this application, the lithium-ion battery further includes a negative electrode sheet, the negative electrode sheet comprising a negative electrode current collector and a negative electrode coating layer disposed on at least one surface of the negative electrode current collector, and satisfying at least one of the following conditions: The negative electrode dressing layer includes a negative electrode adhesive, which includes modified styrene-butadiene rubber, wherein the modified styrene-butadiene rubber includes at least one of oxygen-containing groups and nitrogen-containing groups; The thickness of the negative electrode current collector is 4 micrometers to 5 micrometers.

[0014] In some embodiments of this application, at least one of the following conditions is satisfied: The double-sided areal density of the positive electrode is 400 g / m³. 2 ~500 g / m 2 ; The double-sided areal density of the negative electrode is 160 g / m³. 2 ~200 g / m 2 ; The compaction density of the positive electrode is 2.6 g / m³. 2 ~3.0g / m 2 ; The compaction density of the negative electrode sheet is 1.3 g / m³. 3 ~1.9 g / m 3 .

[0015] In a second aspect of this application, an electrical device is provided, comprising the aforementioned lithium-ion battery. Therefore, the electrical device has a high energy density. Detailed Implementation

[0016] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0017] The positive electrode sheet comprises a positive electrode current collector and a positive electrode coating layer arranged on at least one side of the positive electrode current collector. The positive electrode coating layer has a relatively loose structure. The compaction density of the positive electrode sheet indicates the degree of roller pressure. For example, the thickness of the positive electrode coating layer is 200 before rolling, and the thickness of the positive electrode coating layer is 100 after rolling, that is, the greater the degree of rolling, the greater the extension of the positive electrode coating layer. Therefore, when the positive electrode sheet is cold-pressed (the positive electrode current collector and the positive electrode coating layer are compacted together), the positive electrode current collector and the positive electrode coating layer are simultaneously extended. At this time, the plasticity of the current collector is strong, and the current collector is easy to extend under the action of external force. The plasticity of the positive electrode coating layer with high compaction density does not match the plasticity of the positive electrode current collector (that is, the plasticity of the two is greatly different). If the two are pressed together at the same time, the positive electrode coating layer is easy to break. Therefore, the inventors consider that the extension rate of the positive electrode current collector and the positive electrode coating layer can be controlled to balance the plasticity of the two, thereby reducing the risk of cold-pressing.

[0018] In view of this, in a first aspect of the present application, a lithium ion battery is provided, comprising a positive electrode sheet, the positive electrode sheet comprising a positive electrode current collector and a positive electrode coating layer arranged on at least one side surface of the positive electrode current collector, the lithium ion battery satisfying: a / b=0.5~1.5; wherein a represents the extension rate of the positive electrode current collector, unit: %, b represents the extension rate of the positive electrode coating layer, unit: %.

[0019] In the present application, the ratio of the extension rates of the positive electrode current collector and the positive electrode coating layer is limited to 0.5~1.5, that is, the extension rate of the positive electrode current collector is limited to 50%~150% of the extension rate of the positive electrode coating layer. That is, by adjusting the extension rates of the two, the plasticity of the positive electrode current collector and the positive electrode coating layer is adapted, and the plasticity of the two is basically equivalent when cold-pressed, thereby reducing the risk of breaking the positive electrode coating layer.

[0020] Specifically, a / b in the above can be 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5 or any range between any two of them. a / b in the above range can basically ensure that the plasticity of the positive electrode current collector and the positive electrode coating layer is basically equivalent, thereby ensuring that the positive electrode coating layer does not break during subsequent cold-pressing.

[0021] Furthermore, when a / b < 0.5, it indicates that the elongation of the positive electrode current collector is too small. During cold pressing, the positive electrode coating layer and the positive electrode current collector are prone to relative displacement, which can cause problems such as powder shedding or complete detachment of the positive electrode coating layer. When a / b > 1.5, it indicates that the elongation of the positive electrode current collector is too large. During cold pressing, it is prone to excessive stretching, which can easily cause wavy wrinkles at the edge of the positive electrode current collector, as well as unevenness in the thinned area (there is a process of thinning the edge of the current collector during production. If the elongation of the positive electrode current collector is too small, the thickness of the current collector after cold pressing may be uneven, resulting in inconsistent thickness in the thinned area), affecting subsequent battery manufacturing processes.

[0022] In some embodiments of this application, a / b = 0.5~0.7, specifically, it can be a range of 0.5, 0.6, 0.7, or any two thereof. This helps to further improve the compatibility of the positive electrode current collector and the positive electrode dressing layer in terms of ductility, thereby reducing the risk of breakage of the positive electrode dressing layer during cold pressing.

[0023] In some embodiments of this application, 'a' can be 1% to 1.5%, specifically 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, etc. The elongation of the positive electrode current collector within the above range can meet the shaping requirements of cold pressing and ensure compliance with other process requirements. Excessive elongation will not lead to problems such as wavy wrinkles or thinning areas at the edge of the positive electrode current collector; nor will excessively low elongation lead to problems such as unevenness of the positive electrode sheet.

[0024] Specifically, the elongation 'a' of the positive electrode dressing layer can be controlled by rolling the positive electrode sheet to different degrees or by adjusting the particle size ratio in the positive electrode dressing layer.

[0025] In some embodiments of this application, b can be 1% to 2%, specifically, it can be 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0%, or any two of these ranges. An elongation rate within the above range can generally ensure the stability of the positive electrode dressing layer, thereby improving the stability of the positive electrode sheet. Excessive elongation rate can lead to reduced structural stability of the positive electrode dressing layer, and even problems such as powder shedding or detachment.

[0026] Specifically, the elongation b of the positive current collector can be controlled by tension regulation, processing speed, and post-treatment (annealing) during the aluminum foil manufacturing process.

[0027] In the above text, elongation refers to the proportion of the length of the positive electrode current collector or positive electrode dressing layer that is stretched to its original length when subjected to force. It can be expressed by the formula: Elongation = (Total stretched length - Original length) / Original length × 100%.

[0028] In some embodiments of this application, the bifacial areal density of the positive electrode is 400 g / m². 2 ~500 g / m 2 Specifically, it can be 400g / m 2 420 g / m 2 440 g / m 2 460 g / m 2 480 g / m 2 500 g / m 2 Etc. A bifacial areal density within the aforementioned range helps to improve the energy density of the battery.

[0029] In some embodiments of this application, the compaction density of the positive electrode sheet is 2.6 g / m³. 2 ~3.0g / m 2 Specifically, it can be 2.6 g / m 2 2.7 g / m 2 2.8 g / m 2 2.9 g / m 2 3.0 g / m 2 The compaction density within the above range can basically ensure sufficient particle contact between the positive electrode coating layers on the positive electrode sheet, thereby ensuring the electronic conductivity of the electrode, reducing the internal resistance of the electrode, promoting the electrochemical reaction, and improving the power performance of the battery.

[0030] In some embodiments of this application, the lithium-ion battery further includes a separator disposed between the positive electrode and the negative electrode. The separator includes a base film and a ceramic layer disposed on at least one side of the base film, and a particle layer is disposed on the surface of the ceramic layer away from the base film. The separator satisfies: c / d = 0.1~0.2, where c represents the thickness of the particle layer in micrometers, and d represents the total thickness of the base film and the ceramic layer in micrometers.

[0031] Specifically, in this application, the positive and negative electrode sheets have a high compaction density or areal density, and the particles in the coating layer are compressed more tightly. The greater the compressive force, the greater the internal stress of the electrode sheet. At this time, when the colloid layer (elastic buffer layer) on the surface of the separator in contact with the positive and negative electrode sheets is compressed by the electrode sheets, the colloid layer undergoes elastic deformation, converting the compressive stress of the electrode sheets into the elastic deformation energy of the colloid particles, thereby alleviating or even eliminating the internal stress of the electrode sheets. However, this colloid layer is generally a hydrophobic structure, while the ceramic layer is a hydrophilic structure. The thicker the colloid layer, the thinner the exposed hydrophilic ceramic layer, making it difficult for the electrolyte to wet the separator, thus affecting the ion conduction efficiency and ultimately affecting the battery performance.

[0032] Therefore, by limiting the thickness ratio of the colloidal layer in the separator, c / d = 0.1~0.2 is satisfied. For example, c / d can be 0.1, 0.15, 0.2, or any range between two of them. This not only buffers the stress between the high-voltage solid electrodes but also ensures that the electrolyte fully wets the separator, guaranteeing the ion conduction efficiency.

[0033] In some embodiments of this application, the separator can be a separator known in the art that can be used in lithium-ion batteries and is stable to the electrolyte used. The base membrane includes polyethylene membranes, polypropylene membranes, polyethylene / polypropylene composite membranes, etc.

[0034] In some embodiments of this application, the granular layer includes at least one of polyacrylate (PA) and its copolymers, polymethyl methacrylate (PMMA) and its copolymers, and polyvinylidene fluoride (PVDF) and its copolymers.

[0035] In some embodiments of this application, the lithium-ion battery further includes an electrolyte comprising lithium salt, solvent, and additives. The viscosity of the electrolyte is 5 mPa·s to 10 mPa·s, specifically, it can be within the range of 5 mPa·s, 6 mPa·s, 7 mPa·s, 8 mPa·s, 9 mPa·s, 10 mPa·s, or any two of these ranges. An electrolyte viscosity within this range allows for rapid penetration into the micropores of the high-voltage solid electrode and the micropores of the separator, ensuring unobstructed ion transport channels within the battery. Excessively high electrolyte viscosity may result in slow or insufficient wetting, affecting ion transport.

[0036] In some embodiments of this application, the ionic conductivity of the electrolyte is approximately 13 Ms / cm to 15 Ms / cm, specifically, it can be 13 Ms / cm, 14 Ms / cm, 15 Ms / cm, or any range between two of these. An ionic conductivity within this range indicates that ions move rapidly within the electrolyte, allowing the battery to withstand larger charge and discharge currents, thus exhibiting higher rate performance. Simultaneously, high ionic conductivity indicates lower resistance to ion transport, which helps reduce internal battery resistance, resulting in less energy loss during charge and discharge and improving the battery's energy utilization efficiency.

[0037] In some embodiments of this application, the solvent in the electrolyte includes ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC), and the mass ratio of EC, EMC, and DMC is 0.5~1.5:2~3:2~3. Specifically, the mass ratio of EC, EMC, and DMC can be 1:2:2, 0.5:2:2, 0.5:3:3, 1:3:3, 1:3:2, etc. The above mass ratio range ensures a relatively high content of DMC with lower viscosity, thereby helping to further reduce the viscosity of the electrolyte and improve its wettability.

[0038] In some embodiments of this application, the pore space inside the high-voltage solid electrode is smaller than that of ordinary electrodes, making it more difficult for the electrolyte to penetrate into the electrode during liquid injection. A high-pressure liquid injection process is required to accelerate the penetration of the electrolyte. When the liquid injection machine pressure is ≥400Kpa, the electrolyte wetting problem can be further improved.

[0039] In some embodiments of this application, the lithium salt includes at least one selected from LiPF6, LiFSI, LiTFSI, LiOTF, LiBF4, LiAsF6, and LiClO4. Lithium salts can provide lithium ions to lithium-ion batteries, support electrolyte stability and electrochemical reactions, contribute to the formation of a protective SEI film, improve conductivity, and enhance the safety of lithium-ion batteries.

[0040] In some embodiments of this application, the additive includes at least one selected from vinylene carbonate, fluoroethylene carbonate, ethylene sulfate, methane disulfonate, siloxane additives, lithium bis(oxalato)borate, lithium difluorophosphate, lithium difluorooxalatoborate, and lithium nitrate. This can further improve the energy density, fast-charging performance, and cycle life of lithium-ion batteries.

[0041] In some embodiments of this application, the positive electrode dressing layer includes a positive electrode binder, which includes modified polyvinylidene fluoride (PVDF). The modified PVDF contains oxygen- and nitrogen-containing polar groups. These oxygen- and nitrogen-containing polar groups can enhance the intermolecular forces of PVDF, thereby improving its adhesive properties. This, in turn, enables better adhesion between particles, as well as between the positive electrode dressing layer and the current collector, ultimately improving the structural stability of the positive electrode sheet.

[0042] In some embodiments of this application, the positive electrode coating layer includes a positive electrode active material. This positive electrode active material may include at least one of the following: layered 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 materials, and rock salt phase layered materials); olivine-type phosphate active materials (e.g., lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, etc.); and spinel-structured 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 aforementioned positive electrode active material may further include doping elements and a coating layer. As a specific example, the positive electrode active material includes lithium iron phosphate. Therefore, the lithium-ion battery exhibits better cycle stability and safety performance.

[0043] In some embodiments of this application, the positive electrode coating layer further includes a positive electrode conductive agent, which includes at least one selected from SuperP, superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes (CNTs), graphene, and carbon nanofibers. This effectively improves conductivity, reduces internal resistance, and enhances the electrochemical performance of lithium-ion batteries.

[0044] In some embodiments of this application, the positive electrode current collector includes aluminum foil, and the thickness of the aluminum foil is 4 micrometers to 5 micrometers. Specifically, it can be 4 micrometers, 4.5 micrometers, 5 micrometers, or any range between two of them. In related technologies, the thickness of the current collector is generally greater than 6 micrometers, while in this application, the thickness of the positive electrode current collector is reduced. The thinner aluminum foil occupies less internal space in the battery, and the saved space can be used to fill more positive electrode coating layers, thereby achieving higher battery energy, improving the battery's energy density, and ensuring the mechanical stability of the positive electrode sheet.

[0045] In some embodiments of this application, during the production process of using lightweight aluminum foil (i.e., aluminum foil with a smaller thickness in this application), the mechanical strength of the aluminum foil is reduced due to the reduced aluminum foil thickness, which can easily cause problems such as folding of the coiled tabs and tearing of the welded tabs. The mechanical strength of the tabs can be improved by using a tab embossing process and rounding the edges to reduce the stress on the tabs, thereby improving the folding and tearing problems.

[0046] In some embodiments of this application, the lithium-ion battery further includes a negative electrode sheet, which comprises a negative electrode current collector and a negative electrode coating layer disposed on at least one surface of the negative electrode current collector. The negative electrode coating layer comprises modified styrene-butadiene rubber (SBR), which includes oxygen- and nitrogen-containing polar groups. These oxygen- and nitrogen-containing polar groups can enhance the intermolecular forces of PVDF, thereby improving its adhesion properties. This, in turn, enables better adhesion between particles, as well as between the negative electrode coating layer and the current collector, ultimately improving the structural stability of the negative electrode sheet.

[0047] In some embodiments of this application, the negative electrode current collector includes copper foil. Copper has excellent conductivity, which can efficiently transport electrons from the negative electrode, reduce the internal resistance of the electrode, and improve the rate performance of the battery. At the same time, copper will not undergo side reactions with the negative electrode material.

[0048] In some embodiments of this application, the thickness of the copper foil is 4 to 5 micrometers. This saves space to fill more of the negative electrode coating layer, thereby achieving higher battery energy and increasing the battery's energy density, while also ensuring the mechanical stability of the negative electrode sheet.

[0049] In some embodiments of this application, the negative electrode coating layer includes a negative electrode active material, which may include carbon-based materials, silicon-based materials, tin-based materials, etc. These negative electrode active materials possess excellent capacity performance and low cost, and different active materials can be selected according to actual needs.

[0050] In some embodiments of this application, the negative electrode coating layer further includes a conductive agent. The conductive agent may include, but is not limited to, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0051] In some embodiments of this application, the double-sided areal density of the negative electrode is 160 g / m². 2 ~200 g / m 2 Specifically, it can be 160g / m 2 170 g / m 2 180 g / m 2 190 g / m 2 200 g / m 2 Etc. A bifacial areal density within the aforementioned range helps to improve the energy density of the battery.

[0052] In some embodiments of this application, the compaction density of the negative electrode sheet is 1.3 g / m³. 3 ~1.9 g / m 3 Specifically, it can be 1.3 g / m 3 1.4 g / m 3 1.5 g / m 3 1.6 g / m 3 1.7 g / m 3 1.8 g / m 3 1.9 g / m 3 The compaction density within the above range can basically ensure sufficient particle contact between the negative electrode coating layers on the negative electrode sheet, thereby ensuring the electronic conductivity of the electrode, reducing the internal resistance of the electrode, promoting the electrochemical reaction, and improving the power performance of the battery.

[0053] In some embodiments, the lithium-ion battery has a mass energy density ≥190Wh / kg and a volumetric energy density ≥420Wh / L.

[0054] Typically, a lithium-ion battery includes the aforementioned positive electrode, negative electrode, electrolyte, and separator. The positive electrode, negative electrode, and separator can be manufactured into a cell using winding or stacking processes. The cell and electrolyte can be housed in an outer package. During charging and discharging, active ions repeatedly insert and extract between the positive and negative electrodes. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0055] According to embodiments of this application, the specific type of lithium-ion battery is not particularly limited. For example, from a shape perspective, the lithium-ion battery includes, but is not limited to, prismatic batteries, pouch batteries, and cylindrical batteries, etc., and this application does not impose any particular limitations. From the perspective of the core structure, the core of the lithium-ion battery can be a wound core (i.e., the positive electrode sheet, negative electrode sheet, and separator are stacked and then wound to form the core), or it can be a stacked core (i.e., multiple positive electrode sheets, negative electrode sheets, and separators are stacked to form the core). The outer shell can be a hard shell (such as a steel shell, hard plastic shell, etc.) or a soft shell (such as an aluminum-plastic film, pouch-type soft shell, etc.), etc., and this application does not impose any particular limitations.

[0056] In a second aspect of this application, an electrical device is provided, comprising the aforementioned lithium-ion battery. Therefore, the electrical device has a high energy density.

[0057] In some embodiments of this application, the specific type of electrical device is not particularly limited and can be any device that uses a lithium-ion battery as a power source or energy storage unit. For example, 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, and so on.

[0058] It is understandable that, in addition to the lithium-ion battery mentioned above, the electrical device also includes other 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.

[0059] The present application will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present application in any way. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in the art or in accordance with the product manual.

[0060] Example 1 Positive electrode sheet: A positive electrode slurry is prepared by mixing lithium iron phosphate (the positive electrode active material), modified PVDF, and conductive agent Super P in a mass ratio of 96.8:1.5:1.5. This slurry is then coated, dried, and rolled to obtain the positive electrode sheet. The double-sided areal density of the positive electrode sheet is 450 g / m³. 2 The compacted density is 2.8 g / cm³. 3 The positive electrode current collector uses an aluminum foil with a thickness of 4 micrometers. The elongation of the positive electrode coating layer is 1.5%, and the elongation of the aluminum foil is 1.25%.

[0061] Negative electrode sheet: A negative electrode slurry is prepared by mixing artificial graphite (the negative electrode active material), modified SBR, and conductive agent (Super P) in a mass ratio of 96.8:1.5:1.5. This slurry is then coated, dried, and rolled to obtain the negative electrode sheet. The anode surface density is 180 g / m². 2 The compacted density is 1.6 g / cm³. 3 The negative electrode current collector uses a copper foil with a thickness of 4 micrometers.

[0062] Separator: A ceramic layer is provided on two opposite surfaces of the polypropylene base membrane, and one side of the ceramic layer has a granule layer. The thickness of the granule layer c / total thickness of the base membrane and ceramic layer d=0.15.

[0063] The positive and negative electrode plates and the separator are stacked together to form a battery cell.

[0064] Electrolyte: Lithium salt, solvent and additive are mixed. Specifically, the concentration of lithium salt LiPF6 in the electrolyte is 1.3 mol / L; the mass ratio of solvent EC, EMC and DMC is 1:2:2; based on the total mass of the electrolyte, the mass percentage of additive fluoroethylene carbonate (FEC) is 1.0 wt%. After injecting the above electrolyte into the packaged battery cell, it is allowed to stand, form, degas, age, and undergo capacity testing before relevant performance tests are conducted.

[0065] Examples 2-21 Same as Example 1, the main differences are shown in Table 1.

[0066] Example 22 Same as Example 1, the main difference is that the positive and negative electrode sheets and the separator are wound together to form the battery cell.

[0067] Examples 23-24 Same as Example 1, the main differences are shown in Table 1.

[0068] Comparative Examples 1-2 Same as Example 1, the main differences are shown in Table 1.

[0069] Detection methods Mass energy density: Mass energy density = Energy / Cell mass (the cell mass is measured by an electronic scale); Volumetric energy density: Volumetric energy density = Energy / Cell volume (Volume = Cell width × Cell shoulder height × Cell thickness).

[0070] Test results The detection results of Examples 1-24 and Comparative Examples 1-2 are shown in Table 2.

[0071]

[0072] Conclusion: As can be seen from the above embodiments and comparative examples, the lithium-ion battery of this application does not have the risk of tape breakage during cold pressing, and at the same time has high mass energy density and volumetric energy density.

[0073] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0074] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0075] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0076] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0077] 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.

[0078] 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 lithium-ion battery, characterized in that, The lithium-ion battery includes a positive electrode sheet, which comprises a positive current collector and a positive electrode coating layer disposed on at least one side surface of the positive current collector, wherein the lithium-ion battery satisfies the following condition: a / b = 0.5~1.

5. Where a represents the elongation of the positive electrode current collector, in %, and b represents the elongation of the positive electrode dressing layer, in %.

2. The lithium-ion battery according to claim 1, characterized in that, a / b = 0.5~0.

7.

3. The lithium-ion battery according to claim 1, characterized in that, At least one of the following conditions must be met: a is 1%~1.5%; b is 1%~2%.

4. The lithium-ion battery according to claim 1, characterized in that, It also includes a diaphragm, which includes a base membrane and a ceramic layer disposed on at least one side of the base membrane, and a particle layer is disposed on the surface of the ceramic layer away from the base membrane. The diaphragm satisfies: c / d=0.1~0.2, where c represents the thickness of the particle layer in micrometers and d represents the total thickness of the base membrane and the ceramic layer in micrometers.

5. The lithium-ion battery according to claim 4, characterized in that, At least one of the following conditions must be met: The base film includes at least one of polypropylene base film, polyethylene base film, and polypropylene and polyethylene composite base film; The granular layer includes at least one of polyacrylate and its copolymers, polymethyl methacrylate and its copolymers, and polyvinylidene fluoride and its copolymers.

6. The lithium-ion battery according to claim 1, characterized in that, It also includes an electrolyte that satisfies at least one of the following conditions: The viscosity of the electrolyte is 5 mPa·s to 10 mPa·s; The ionic conductivity of the electrolyte is approximately 13 Ms / cm to 15 Ms / cm.

7. The lithium-ion battery according to claim 6, characterized in that, The electrolyte comprises lithium salt, solvent, and additives, and satisfies at least one of the following conditions: The solvent includes ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate, and the mass ratio of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate is 0.5~1.5:2~3:2~3; The lithium salt includes at least one of LiPF6, LiFSI, LiTFSI, LiOTF, LiBF4, LiAsF6, and LiClO4; The additives include at least one of vinylene carbonate, fluoroethylene carbonate, vinyl sulfate, methane disulfonate, siloxane additives, lithium bis(oxalato)borate, lithium difluorophosphate, lithium difluorooxalatoborate, and lithium nitrate.

8. The lithium-ion battery according to claim 1, characterized in that, At least one of the following conditions must be met: The positive electrode dressing layer includes a positive electrode adhesive, which includes modified polyvinylidene fluoride, wherein the modified polyvinylidene fluoride includes at least one of oxygen-containing groups and nitrogen-containing groups; The thickness of the positive electrode current collector is 4 micrometers to 5 micrometers.

9. The lithium-ion battery according to claim 1, characterized in that, It also includes a negative electrode sheet, which comprises a negative electrode current collector and a negative electrode dressing layer disposed on at least one surface of the negative electrode current collector, and satisfies at least one of the following conditions: The negative electrode dressing layer includes a negative electrode adhesive, which includes modified styrene-butadiene rubber, wherein the modified styrene-butadiene rubber includes at least one of oxygen-containing groups and nitrogen-containing groups; The thickness of the negative electrode current collector is 4 micrometers to 5 micrometers.

10. The lithium-ion battery according to claim 9, characterized in that, At least one of the following conditions must be met: The double-sided areal density of the positive electrode is 400 g / m³. 2 ~500 g / m 2 ; The double-sided areal density of the negative electrode is 160 g / m³. 2 ~200 g / m 2 ; The compaction density of the positive electrode is 2.6 g / m³. 2 ~3.0g / m 2 ; The compaction density of the negative electrode sheet is 1.3 g / m³. 3 ~1.9 g / m 3 .

11. An electrical appliance, characterized in that, The lithium-ion battery includes any one of claims 1 to 10.

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