Electrode sheets and secondary batteries

Abstract

This application relates to the field of secondary batteries, providing an electrode and a secondary battery that can at least improve the liquid absorption rate of the current collector. The electrode includes: a current collector; a nanocone layer located on the surface of the current collector, the nanocone layer comprising an array of multiple nanocones; a nanoparticle layer located on the surface of the nanocone layer away from the current collector, the nanoparticle layer comprising multiple nanoparticles; and a conductive network layer located on the side of the nanoparticle layer away from the nanocone layer.

Description

Technical Field

[0001] This application relates to the field of secondary batteries, and in particular to an electrode and a secondary battery. Background Technology

[0002] With increasing environmental awareness and growing pressure on the living environment, green and clean energy is gaining prominence in the power energy sector. Lithium-ion batteries, as a crucial direction and product in energy conversion and storage, occupy a significant position within this sector. Lithium-ion batteries are a type of chemical battery that relies on lithium ions shuttling between the positive and negative electrodes to achieve discharge. They possess characteristics and advantages such as high energy density, high operating voltage, long cycle life, low self-discharge rate, and environmental friendliness.

[0003] The electrodes of a secondary battery typically include current collectors. Current collectors with high liquid absorption rates promote rapid electrolyte wetting of the electrode materials, ensuring sufficient contact between the active material and the electrolyte, reducing localized polarization, and improving reaction uniformity. Insufficient liquid absorption by the current collector leads to poor solid-liquid interface contact, increasing charge transfer resistance (Rct) and reducing the rate performance of the secondary battery. Utility Model Content

[0004] This application provides an electrode and a secondary battery, which at least helps to improve the liquid absorption rate of the current collector.

[0005] According to some embodiments of this application, one aspect of this application provides an electrode sheet, comprising: a current collector; a nanocone layer located on the surface of the current collector, the nanocone layer comprising a plurality of nanocones arranged in an array; a nanoparticle layer located on the surface of the nanocone layer away from the current collector, the nanoparticle layer comprising a plurality of nanoparticles; and a conductive network layer located on the side of the nanoparticle layer away from the nanocone layer.

[0006] In some embodiments, the current collector is a copper foil, and the nanocone layer is a cuprous oxide nanocone layer.

[0007] In some embodiments, the apex angle of the nanocone is 50° to 70°; and / or, the height of the nanocone is 400 nm to 600 nm in the direction perpendicular to the surface of the current collector.

[0008] In some embodiments, the nanoparticles are titanium dioxide nanoparticles.

[0009] In some embodiments, the thickness of the nanoparticle layer is 20 nm to 50 nm in the direction perpendicular to the surface of the nanocone; and / or, the particle size is 10 nm to 30 nm when the cumulative distribution percentage of the nanoparticles reaches 50%.

[0010] In some embodiments, the surface area of ​​the nanocone layer away from the current collector is the first area, and the surface area of ​​the nanoparticle layer covering the nanocone layer is the second area, wherein the ratio of the second area to the first area is greater than or equal to 90%.

[0011] In some embodiments, the conductive network layer is a fluorinated graphene conductive network layer.

[0012] In some embodiments, the thickness of the conductive network layer is 1 nm to 5 nm in the direction perpendicular to the surface of the current collector.

[0013] In some embodiments, the pores remaining between the nanocones in the nanocone layer, other than the nanoparticles, are the first pores, and the conductive network layer has the second pores, wherein the size of the first pores is larger than the size of the second pores.

[0014] According to some embodiments of this application, another aspect of this application also provides a secondary battery, including: the electrode sheet as described in the above embodiments.

[0015] The technical solution provided in this application has at least the following advantages:

[0016] The electrode provided in this application includes a current collector, on which a nanocone layer, a nanoparticle layer, and a conductive network layer are sequentially disposed. The nanocone layer comprises multiple nanocones arranged in an array to increase the specific surface area of ​​the current collector. By forming vertically aligned nanochannels, capillary pressure is generated, promoting rapid longitudinal penetration of the electrolyte. The nanoparticles on the surface of the nanocones further increase the specific surface area of ​​the nanocones, thereby increasing the specific surface area of ​​the current collector, which is beneficial for promoting electrolyte wetting of the current collector. Furthermore, the nanoparticle layer can increase the interfacial bonding force between the conductive network layer and the nanocone layer, serving as a transition layer between the conductive network layer and the nanocone layer to prevent the conductive network layer from peeling off. The conductive network layer can encapsulate the nanoparticle layer, preventing problems such as expansion, contraction, aggregation, and detachment of the nanoparticles during the charging and discharging process of the secondary battery, thus improving the stability of the electrode. The stable multi-level porous structure formed by the nanocone layer, nanoparticle layer, and conductive network layer is beneficial for increasing the liquid absorption rate of the current collector, which in turn promotes the increase of active sites for the reaction between the current collector and the electrolyte, facilitating ion / electron transport. Attached Figure Description

[0017] One or more embodiments are illustrated by way of example with corresponding pictures in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Unless otherwise stated, the pictures in the accompanying drawings do not constitute a limitation on scale. In order to more clearly illustrate the technical solutions in the embodiments of this application or in the conventional technology, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the structure of an electrode sheet provided in an embodiment of this application.

[0019] Explanation of reference numerals in the attached figures:

[0020] 100, Current collector; 110, Nanocone layer; 111, Nanocone; 120, Nanoparticle layer; 121, Nanoparticle; 130, Conductive network layer; 131, Conductive sheet layer; 112, First pore; 132, Second pore. Detailed Implementation

[0021] As is known from the background technology, insufficient liquid absorption by the current collector can lead to poor solid-liquid interface contact, increase charge transfer resistance (Rct), and reduce the rate performance of the secondary battery.

[0022] Taking the negative electrode current collector copper foil as an example, after the copper foil surface is oxidized, a copper oxide layer is formed, which makes the contact angle of the electrolyte on the copper foil about 65°, severely hindering the wetting of the electrolyte. Traditionally, a single-layer hydrophilic coating, such as silicon dioxide, is formed on the copper foil, which can reduce the contact angle of the copper foil to about 15°. However, due to stress mismatch, silicon dioxide peeling is prone to occur.

[0023] In related technologies, plasma fluorination is used to treat copper foil to improve the liquid absorption rate of copper foil, but the contact angle of the fluorinated layer is about 30°, which cannot meet the requirements of rapid wetting; another method is to deposit cuprous oxide nanowires on the surface of copper foil by electrochemical deposition to improve the liquid absorption rate of copper foil, with a contact angle of about 40°, but the wetting time still requires 25 minutes.

[0024] This application provides an electrode and a secondary battery, which at least helps to improve the liquid absorption rate of the current collector.

[0025] In the description of the embodiments of this application, the technical terms "first", "second", etc. are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0026] In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0027] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A exists, A and B exist simultaneously, and B exists. In addition, the character " / " in this document generally indicates that the related objects before and after it have an "or" relationship.

[0028] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0029] In the accompanying drawings corresponding to the embodiments of this application, the thickness and area of ​​the layers are enlarged for better understanding and ease of description. When describing a component on another component or on the surface of another component, the component may be "directly" located on the surface of the other component, or there may be a third component between the two components. Conversely, when describing a component on the surface of another component, or when another component is formed or disposed on the surface of a component, it indicates that there is no third component between the two components. Furthermore, when describing a component as being "generally" formed on another component, it means that the component is not formed on the entire surface (or front surface) of the other component, nor is it formed on a portion of the edge of the entire surface.

[0030] In the description of the embodiments of this application, when a component "includes" another component, other components are not excluded unless otherwise stated, and other components may be further included.

[0031] The terminology used in the description of the various embodiments herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in the description of the various embodiments and the appended claims, the term "component" is also intended to include the plural form unless the context clearly indicates otherwise.

[0032] The embodiments of this application will now be described in detail with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the embodiments of this application to facilitate a better understanding of the application. However, the technical solutions claimed in this application can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0033] Figure 1 This is a schematic diagram of the structure of an electrode sheet provided in an embodiment of this application.

[0034] refer to Figure 1 The electrode provided in this application embodiment includes: a current collector 100, a nanocone layer 110, a nanoparticle layer 120, and a conductive network layer 130.

[0035] The nanocone layer 110 is located on the surface of the current collector 100, and the nanocone layer 110 includes a plurality of nanocones 111 arranged in an array.

[0036] The nanoparticle layer 120 is located on the surface of the nanocone layer 110 away from the current collector 100, and the nanoparticle layer 120 includes a plurality of nanoparticles 121.

[0037] The conductive network layer 130 is located on the side of the nanoparticle layer 120 away from the nanocone layer 110.

[0038] The electrode provided in this application embodiment includes a current collector 100, on which a nanocone layer 110, a nanoparticle layer 120 and a conductive network layer 130 are sequentially disposed. The nanocone layer 110 includes multiple nanocones 111 arranged in an array to increase the specific surface area of ​​the current collector 100. By forming vertically arranged nanochannels, capillary pressure is generated, promoting rapid longitudinal penetration of the electrolyte. The nanoparticles 121 on the surface of the nanocones 111 increase the specific surface area of ​​the nanocones 111, thereby further increasing the specific surface area of ​​the current collector 100, which is beneficial for promoting electrolyte wetting of the current collector 100. In addition, the nanoparticle layer 120 can also increase the interfacial bonding force between the conductive network layer 130 and the nanocone layer 110, serving as a transition layer between the conductive network layer 130 and the nanocone layer 110, preventing the conductive network layer 130 from peeling off. The conductive network layer 130 can encapsulate the nanoparticle layer 120, preventing the nanoparticles 121 from expanding, contracting, agglomerating, and detaching during the charging and discharging process of the secondary battery, thus improving the stability of the electrode. The stable multi-level porous structure formed by the nanocone layer 110, nanoparticle layer 120 and conductive network layer 130 is conducive to improving the liquid absorption rate of the current collector 100, which in turn helps to increase the number of active sites for the reaction between the current collector 100 and the electrolyte, and promotes ion / electron transport.

[0039] In this embodiment, the current collector 100 is a copper foil; in other embodiments, the current collector 100 may also be an aluminum foil.

[0040] When the current collector is copper foil, the nanocone layer 110 is a cuprous oxide nanocone layer or a copper nanocone layer. When the current collector is aluminum foil, the nanocone layer 110 can be an alumina nanocone layer.

[0041] Taking the current collector 100 as a copper foil and the nanocone layer 110 as a cuprous oxide nanocone layer as an example, the method for forming the nanocone layer 110 is as follows: Prepare a 0.1M–0.5M NaOH solution as the electrolyte. At 25±2℃, use the copper foil as the working electrode, a platinum sheet or graphite as the counter electrode, and a saturated calomel electrode (SCE) as the reference electrode. Apply a constant voltage of 0.8V–1.2V vs. SCE, with a current density of 3mA / cm². 2 ~5mA / cm 2 The time is 12 min to 18 min, so that cuprous oxide nanocones are formed on the surface of the copper foil.

[0042] The growth rate of nanocones can be determined by controlling the current density, and the height of nanocones can be controlled by controlling the oxidation time.

[0043] In other embodiments, the methods for forming cuprous oxide nanocone layers include: chemical oxidation, thermal oxidation, and hydrothermal methods. Chemical oxidation involves oxidizing the surface of a copper foil in an alkaline solution using an oxidizing agent (such as persulfate) to form cuprous oxide nanocone structures; the size and density of the nanocones are controlled by adjusting the solution concentration, temperature, and reaction time. Thermal oxidation involves oxidizing the surface of a copper foil through high-temperature annealing to form cuprous oxide nanocones; the size and density of the nanocones are controlled by adjusting the oxygen flow rate, temperature, and time. Hydrothermal methods generate cuprous oxide nanocones through a hydrothermal reaction in a closed, high-pressure environment; the size and density of the nanocones are controlled by adjusting the reaction temperature, time, and pH value.

[0044] In some embodiments, the apex angle α of the nanocone 111 is 50° to 70°, specifically 50°, 55°, 60°, 65° or 70°.

[0045] It should be noted that the apex angle α of different individual nanocones 111 may be different. Therefore, the apex angle α of nanocones 111 being 50° to 70° means that the average apex angle of multiple nanocones 111 on the surface of current collector 100 is in the range of 50° to 70°.

[0046] In some embodiments, the height H1 of the nanocone 111 is 400nm to 600nm in the direction perpendicular to the surface of the current collector 100, for example, it can be 400nm, 430nm, 450nm, 480nm, 500nm, 520nm, 550nm, 580nm or 600nm.

[0047] It should be noted that the height H1 of different individual nanocones 111 in the direction perpendicular to the surface of the current collector 100 may be different. Therefore, the height H1 of nanocones 111 being 400nm to 600nm means that the average height of multiple nanocones 111 on the surface of the current collector 100 is in the range of 400nm to 600nm.

[0048] In this embodiment, nanoparticle 121 is titanium dioxide nanoparticle. The surface of titanium dioxide nanoparticle has abundant hydroxyl (-OH) groups, which have good wettability to organic electrolytes (such as carbonates), and can promote the penetration of electrolyte into the deep pores of the nanocone 111 array, thereby improving ion accessibility.

[0049] In other embodiments, nanoparticles 121 may also be silicon oxide nanoparticles.

[0050] The nanoparticle layer 120 can be formed by chemical vapor deposition (CVD), atomic layer deposition (ALD), or magnetron sputtering (PVD).

[0051] In some embodiments, the thickness H2 of the nanoparticle layer 120 in the direction perpendicular to the surface of the nanocone 111 is 20 nm to 50 nm, for example, it can be 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm or 50 nm.

[0052] It should be noted that the thickness of the nanoparticle layer 120 at different positions on the nanocone 111 may be different. The thickness H2 of the nanoparticle layer 120 is 20nm to 50nm, which means that the average thickness of the nanoparticle layer 120 is in the range of 20nm to 50nm.

[0053] In some embodiments, the particle size of nanoparticles 121 when the cumulative distribution percentage reaches 50% is 10 nm to 30 nm, for example, 10 nm, 15 nm, 20 nm, 25 nm or 30 nm.

[0054] In some embodiments, the surface area of ​​the nanocone layer 110 away from the current collector 100 is a first area, and the surface area of ​​the nanoparticle layer 120 covering the nanocone layer 110 is a second area. The ratio of the second area to the first area is greater than or equal to 90%, specifically 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100%. That is, the coverage of the nanoparticle layer 120 on the surface of the nanocone layer 110 is greater than 90%.

[0055] In this embodiment, the conductive network layer 130 is a three-dimensional network structure formed by overlapping and staggering conductive sheet layers 131. In other embodiments, the conductive network layer 130 may also be a three-dimensional network structure composed of carbon nanotubes, conductive polymers, or metal nanowires.

[0056] In this embodiment, the conductive network layer 130 is a fluorinated graphene conductive network layer, that is, the conductive sheet 131 is fluorinated graphene. The conductive network formed by the stacking of sheet-like fluorinated graphene gives the current collector 100 high liquid absorption. At the same time, the high bond energy (~485kJ / mol) of the CF bond in the fluorinated graphene endows it with excellent chemical stability, which can suppress electrolyte decomposition and side reactions, so as to achieve the dual function of hydrophilicity and passivation.

[0057] In the fluorinated graphene conductive network layer, the atomic ratio of F atoms to C atoms is 0.15 to 0.2, specifically 0.15, 0.16, 0.17, 0.18, 0.19 or 0.2.

[0058] In this embodiment, the nanoparticles 121 in the nanoparticle layer 120 are titanium dioxide nanoparticles, and the conductive network layer 130 is a fluorinated graphene conductive network layer. The fluorinated functional groups (such as -CF) of the fluorinated graphene can form hydrogen bonds or chemical bonds with the hydroxyl groups (-OH) on the surface of the titanium dioxide nanoparticles, thereby enhancing the interlayer bonding force, reducing desorption, and improving the stability of the current collector 100.

[0059] In some embodiments, the thickness H3 of the conductive network layer 130 in the direction perpendicular to the surface of the current collector 100 is 1 nm to 5 nm, for example, it can be 1 nm, 1.3 nm, 2 nm, 2.5 nm, 3 nm, 3.6 nm, 4 nm, 4.4 nm or 5 nm.

[0060] In some embodiments, the pores remaining between the nanocones 111 in the nanocone layer 110, excluding the nanoparticles 121, are called first pores 112, and the conductive network layer 130 has second pores 132, with the size of the first pores 112 being larger than the size of the second pores 132. Thus, the conductive network layer 130 on the side away from the current collector 100 has smaller pores, absorbing electrolyte through capillary action, while the remaining pores between the nanoparticles 121 on the surface of the nanocones 111 in the nanocone layer 110 on the side closer to the current collector 100 have larger pore sizes, ensuring that the surface of the nanoparticles 121 is not completely covered, thus preserving electrolyte contact windows.

[0061] The electrode provided in this application embodiment includes a current collector 100, on which a nanocone layer 110, a nanoparticle layer 120 and a conductive network layer 130 are sequentially disposed. The nanocone layer 110 includes multiple nanocones 111 arranged in an array to increase the specific surface area of ​​the current collector 100. By forming vertically arranged nanochannels, capillary pressure is generated, promoting rapid longitudinal penetration of the electrolyte. The nanoparticles 121 on the surface of the nanocones 111 increase the specific surface area of ​​the nanocones 111, thereby further increasing the specific surface area of ​​the current collector 100, which is beneficial for promoting electrolyte wetting of the current collector 100. In addition, the nanoparticle layer 120 can also increase the interfacial bonding force between the conductive network layer 130 and the nanocone layer 110, serving as a transition layer between the conductive network layer 130 and the nanocone layer 110, preventing the conductive network layer 130 from peeling off. The conductive network layer 130 can encapsulate the nanoparticle layer 120, preventing the nanoparticles 121 from expanding, contracting, agglomerating, and detaching during the charging and discharging process of the secondary battery, thus improving the stability of the electrode. The stable multi-level porous structure formed by the nanocone layer 110, nanoparticle layer 120 and conductive network layer 130 is conducive to improving the liquid absorption rate of the current collector 100, which in turn helps to increase the number of active sites for the reaction between the current collector 100 and the electrolyte, and promotes ion / electron transport.

[0062] This application provides a specific electrode using copper foil as the current collector. A cuprous oxide nanocone layer is deposited on the copper foil. The height of the nanocones is 500 nm, and the apex angle is 60°. The cuprous oxide nanocone layer can increase the specific surface area of ​​the copper foil from 0.05 m² / s². 2 / g increased to 12m 2 / g, utilizing the capillary pressure generated by the nanochannels between the nanocones, promotes rapid longitudinal penetration of the electrolyte, resulting in a contact angle of 25° between the copper foil with the cuprous oxide nanocone layer and the electrolyte, which is significantly reduced compared to the original contact angle of 65° of the copper foil.

[0063] By setting a titanium dioxide nanoparticle layer with a thickness of 30 nm on the surface of the copper oxide nanocone layer, and setting the particle size of the titanium dioxide nanoparticles at a cumulative distribution percentage of 50% to 20 nm, the contact angle between the copper foil with the copper oxide nanocone layer and the titanium dioxide nanoparticle layer and the electrolyte can be further reduced to 10°.

[0064] By setting a fluorinated graphene conductive network layer with a thickness of 2 nm on a titanium dioxide nanoparticle layer, the contact angle between the copper foil with the cuprous oxide nanocone layer, titanium dioxide nanoparticle layer and fluorinated graphene conductive network layer and the electrolyte can be further reduced to 8°.

[0065] The electrolyte wetting time for copper foil can be shortened to 4.5 minutes, a significant reduction compared to the 60 minutes required for traditional copper foil. Sufficient electrolyte penetration also increases the contact area between the active material and the copper foil, allowing the interfacial resistance (Rct) to decrease from 85 Ω·cm. 2 Reduced to 16Ω·cm 2 This improves lithium-ion insertion / extraction kinetics.

[0066] According to the electrode provided in the embodiments of this application, by constructing a three-level gradient structure of nanocone layer-nanoparticle layer-conductive network layer on the current collector, the electrolyte self-permeation is achieved by utilizing the wetting gradient difference. The wetting gradient generates a surface energy gradient, which drives the electrolyte to spontaneously spread from the high contact angle region (nanocone layer) to the low contact angle region (conductive network layer), thereby reducing the contact angle of the current collector from 65° to 8°, which greatly improves the liquid absorption rate of the current collector.

[0067] Accordingly, another aspect of this application embodiment also provides a secondary battery, including: an electrode as described in the above embodiments. The electrode can be a positive electrode or a negative electrode, and the corresponding current collector can be a positive current collector or a negative current collector. By constructing a three-level gradient structure of nanocone layer-nanoparticle layer-conductive network layer on the current collector in the above embodiments, the electrolyte absorption rate of the current collector is improved.

[0068] The positive current collector is selected from aluminum foil, and the negative current collector is selected from copper foil.

[0069] Based on the chemical composition and working principle of the bare cells, secondary batteries can be classified as lithium-ion batteries, lead-acid batteries, sodium-ion batteries, or nickel-metal hydride batteries. Based on their shape, secondary batteries can be classified as prismatic batteries, cylindrical batteries, or pouch batteries.

[0070] Those skilled in the art will understand that the above embodiments are specific examples of implementing this application, and in practical applications, various changes in form and detail can be made without departing from the spirit and scope of this application. Any person skilled in the art can make various alterations and modifications without departing from the spirit and scope of this application; therefore, the scope of protection of this application should be determined by the scope defined in the claims.

Claims

1. A pole piece, characterized in that, include: current collector; A nanocone layer, the nanocone layer being located on the surface of the current collector, the nanocone layer comprising a plurality of nanocones arranged in an array; A nanoparticle layer is located on the surface of the nanocone layer away from the current collector, and the nanoparticle layer comprises a plurality of nanoparticles; A conductive network layer is located on the side of the nanoparticle layer away from the nanocone layer.

2. The pole piece of claim 1, wherein The current collector is a copper foil, and the nanocone layer is a cuprous oxide nanocone layer.

3. The pole piece according to claim 1 or 2, characterized in that The apex angle of the nanocone is 50° to 70°; and / or, the height of the nanocone is 400 nm to 600 nm in a direction perpendicular to the surface of the current collector.

4. The pole piece of claim 1, wherein The nanoparticles are titanium dioxide nanoparticles.

5. The pole piece according to claim 1 or 4, characterized in that The thickness of the nanoparticle layer is 20 nm to 50 nm in a direction perpendicular to the surface of the nanocone; and / or the particle size is 10 nm to 30 nm when the cumulative distribution percentage of the nanoparticles reaches 50%.

6. The pole piece of claim 1, wherein The surface area of ​​the nanocone layer away from the current collector is the first area, and the surface area of ​​the nanoparticle layer covering the nanocone layer is the second area. The ratio of the second area to the first area is greater than or equal to 90%.

7. The pole piece of claim 1, wherein The conductive network layer is a fluorinated graphene conductive network layer.

8. The pole piece of claim 1 or 7, wherein The thickness of the conductive network layer is 1 nm to 5 nm in the direction perpendicular to the surface of the current collector.

9. The pole piece of claim 1 or 7, wherein The pores remaining between the nanocones in the nanocone layer, excluding the nanoparticles, are the first pores. The conductive network layer has a second pore, and the size of the first pore is larger than the size of the second pore.

10. A secondary battery characterized by comprising: include: The electrode as described in any one of claims 1 to 9.

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