Pole piece of sodium ion battery, preparation method thereof and sodium ion battery

Abstract

This application discloses an electrode for a sodium-ion battery, a method for preparing the same, and the sodium-ion battery. The electrode includes a current collector and a patterned stack disposed on at least one surface thereon. The patterned stack includes at least two patterned layers stacked along the thickness direction. Each patterned layer contains multiple independent and unconnected patterned sub-coatings, which are discretely or concentrically nested within the same patterned layer. This application reduces inter-coating interference and interfacial stress by ensuring the independent and unconnected arrangement of the sub-coatings, thereby hindering the propagation of the peeling initiation point and improving peel strength. It also forms dispersed ion diffusion paths to reduce diffusion resistance and interfacial impedance; simultaneously disperses volume expansion stress, reducing the risk of electrode cracking; and provides multiple deposition sites to improve the uniformity of sodium metal deposition, thus achieving a balance between high peel strength, low interfacial impedance, and good deposition uniformity.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to an electrode for a sodium-ion battery, a method for preparing the same, and the sodium-ion battery itself. Background Technology

[0002] Lithium-ion batteries, with their high energy density and long cycle life, have been widely used in energy storage and power applications. However, my country's total lithium resources are limited and unevenly distributed, and mining is difficult, currently relying heavily on imports. This has led to the search for alternatives to lithium-ion batteries, with sodium, an element in the same group as lithium, being abundant and inexpensive, attracting significant attention. Sodium-ion batteries offer greater economic advantages in large-scale energy storage systems, particularly aligning with the societal need to improve the sustainable use of energy.

[0003] Sodium-ion batteries work on a similar principle to lithium-ion batteries, both achieving charge transfer through the insertion and extraction of ions between the positive and negative electrodes. However, due to the large atomic size of sodium ions and the limited types of suitable insertion materials, the energy density of current sodium-ion full batteries based on insertion reactions is generally low.

[0004] High energy density is crucial for applications such as electric vehicles and mobile devices. Currently, the energy density of sodium-ion batteries still lags far behind that of lithium-ion batteries. To ensure the competitiveness of sodium-ion batteries, the issue of low energy density must be addressed.

[0005] To bridge the energy density gap between sodium-ion batteries and commercial lithium-ion batteries, a viable solution is to replace traditional intercalation-type anodes with metallic sodium anodes. However, metallic sodium remains unstable even in relatively dry air environments and is difficult to process into thin-layer anodes. Most reported studies currently employ excessive amounts of metallic sodium anodes with uncontrollable thickness, severely impacting energy density and limiting large-scale production.

[0006] Chinese patent CN117154081A discloses a high-energy-density sodium-ion battery, which includes a positive electrode, a negative electrode, a separator, an electrolyte, and a battery casing, wherein the negative electrode uses polyimide as the negative electrode material. However, due to the poor conductivity of polyimide, the sodium ion insertion / extraction efficiency is low.

[0007] Chinese patent CN114335523A discloses a method for preparing a hard carbon anode for high-energy-density sodium-ion batteries. This hard carbon anode comprises porous carbon and chemically vapor-deposited carbon for adjusting the surface pore size, while retaining the continuous pore structure within the porous carbon. This invention achieves a hard carbon anode with high initial coulombic efficiency and good rate performance by controlling the surface pore size through a carbon coating structure. However, this hard carbon anode still suffers from significant volume expansion during charge and discharge.

[0008] In summary, existing methods for improving the energy density of sodium-ion batteries by modifying the negative electrode all have certain drawbacks, mainly including: limited energy density improvement, low sodium-ion insertion / extraction efficiency, significant volume expansion during charging and discharging, and insufficient peel strength between the coating and the current collector. Therefore, there is an urgent need to develop a novel sodium-ion battery electrode, its preparation method, and a sodium-ion battery itself. Summary of the Invention

[0009] This application addresses the problems of low energy density, insufficient sodium ion insertion / extraction efficiency, significant volume expansion during charge / discharge, and weak coating peel strength in existing sodium-ion batteries. It provides a sodium-ion battery electrode with a current collector and a patterned stacked layer. The patterned stack includes at least two patterned layers, each comprising multiple independent and unconnected patterned sub-coatings, which are discretely or concentrically nested. This independent, isolated patterned sub-coating structure weakens the interaction between sub-coatings, reduces interfacial stress, blocks the propagation of peeling defects, and prevents localized peeling and diffusion, effectively improving the bonding strength and peel resistance between the coating and the current collector. Simultaneously, it forms multi-path ion diffusion channels, facilitating full electrolyte wetting, balancing the surface electric field distribution, reducing ion diffusion resistance and interfacial impedance, and improving sodium ion insertion / extraction kinetics. Furthermore, it effectively disperses volume expansion stress during charge / discharge, suppresses electrode cracking and deformation, and optimizes the uniformity of sodium metal deposition. Ultimately, while ensuring battery cycle stability, it significantly improves the overall energy density and electrochemical performance of the sodium-ion battery. The technical solution provided in this application is as follows: In a first aspect, this application provides an electrode for a sodium-ion battery, the electrode comprising: Current collector; and Patterned stacks are disposed on at least one surface of the current collector; The patterned stack includes at least two patterned layers stacked along the thickness direction, and two adjacent patterned layers have a partially overlapping area or a completely overlapping area in the plane direction of the current collector. Each of the patterned layers includes a plurality of patterned sub-layers, and the plurality of patterned sub-layers located within the same patterned layer are independent of each other and are not connected to each other; Furthermore, the plurality of patterned sub-coatings located within the same patterned layer are discretely distributed or concentrically nested in the planar direction of the current collector.

[0010] In some preferred embodiments, the plurality of patterned sub-coatings located within the same patterned layer are discretely distributed in the planar direction of the current collector, and the plurality of patterned sub-coatings in at least one patterned layer are annular sub-coatings; each annular sub-coating has an internal hollow region enclosed by its inner boundary, the internal hollow region being an uncoated region for depositing sodium metal; and the gaps between adjacent annular sub-coatings are also uncoated regions for depositing sodium metal.

[0011] In some preferred embodiments, each of the annular sub-coatings has a ring width of 0.5 to 200 μm and a thickness of 2 to 30 μm; and the edge gap between adjacent annular sub-coatings located in the same patterned layer is 1 to 200 μm.

[0012] In some preferred embodiments, the shape of each of the annular sub-coatings is selected from at least one of a circular ring, an elliptical ring, a triangular ring, a quadrilateral ring, a pentagonal ring, or a hexagonal ring; Furthermore, the equivalent circular diameter of the inner hollow region of each of the annular sub-coatings is 0.5~50μm, where the equivalent circular diameter refers to the diameter of a circle with the same area as the inner hollow region.

[0013] In some preferred embodiments, at least one of the patterned layers includes at least two hexagonal annular sub-coatings, and any two hexagonal annular sub-coatings are not nested.

[0014] In some preferred embodiments, the plurality of patterned sub-coatings located within the same patterned layer are concentrically nested in the planar direction of the current collector, and at least one of the patterned layers includes at least two concentric annular sub-coatings, the radial spacing between adjacent annular sub-coatings is 1~200μm, and the ring width of each annular sub-coating is 0.5~200μm and the thickness is 2~30μm.

[0015] In some preferred embodiments, the shape of each of the annular sub-coatings is selected from at least one of a circular ring, an elliptical ring, a triangular ring, a quadrilateral ring, a pentagonal ring, or a hexagonal ring.

[0016] In some preferred embodiments, each patterned layer includes at least two concentric annular sub-coatings.

[0017] In some preferred embodiments, the thickness of the patterned stack is 20~100μm.

[0018] In some preferred embodiments, the blank area ratio in each patterned layer is 20% to 70%; wherein, the blank area ratio refers to the proportion of the area not covered by the patterned sub-coating layer to the total area of ​​the current collector on one side within the same patterned layer.

[0019] In some preferred embodiments, each of the patterned layers comprises structural materials and functional materials; The structural material is selected from at least one of covalent organic framework materials, metal-organic framework materials, metal oxides, metal fluorides, hard carbon, silicon oxide, or silicon carbon; The functional material includes a conductive agent and a binder; The conductive agent is selected from at least one of conductive graphite, carbon black, carbon nanotubes, or graphene. The adhesive is selected from at least one of polyvinylidene fluoride, polyacrylic acid, polyvinyl alcohol, polyimide, polytetrafluoroethylene, sodium carboxymethyl cellulose, or styrene-butadiene rubber.

[0020] In some preferred embodiments, the patterned stack comprises 2 to 50 patterned layers; When the patterned stack comprises at least three patterned layers, along the direction away from the current collector: at least one of the following parameters in each patterned layer of the patterned stack varies with a gradient: The blank area ratio in each patterned layer first decreases and then increases layer by layer. The content of structural material in each patterned layer increases layer by layer and then decreases layer by layer. The content of functional materials in each patterned layer decreases layer by layer and then increases layer by layer.

[0021] In some preferred embodiments, the absolute difference between any two adjacent patterned layers in the blank area ratio is 5% to 10%. And / or, the absolute difference between any two adjacent layers in the content of structural material in each patterned layer is 5% to 10%; And / or, the absolute difference between any two adjacent layers in the content of functional materials in each patterned layer is 5% to 10%.

[0022] Secondly, this application also provides a method for preparing a sodium-ion battery electrode, comprising the following steps: At least two patterned layers are formed layer by layer on at least one surface of the current collector using a patterned deposition process. In forming each patterned layer, multiple independent and unconnected patterned sub-coatings are deposited on the surface of the current collector or on the already formed patterned layer, and the multiple patterned sub-coatings in the same patterned layer are discretely distributed or concentrically nested. Furthermore, when forming two adjacent patterned layers, the patterned layer of the latter layer partially or completely overlaps with the patterned layer of the former layer in the plane direction of the current collector.

[0023] In some preferred embodiments, the deposition method includes 3D printing.

[0024] Thirdly, this application also provides a sodium-ion battery, the sodium-ion battery comprising the electrode sheet described in any of the above claims.

[0025] By adopting the above technical solution, the sodium-ion battery electrode and its preparation method provided in this application have the following beneficial effects on sodium-ion batteries: 1. This application sets the patterned layer as multiple independent and unconnected patterned sub-coatings, with the sub-coatings in the same layer discretely or concentrically nested in the current collector plane. This structure, by isolating the patterned sub-coatings, reduces the interaction between them, effectively alleviates internal stress at the interface, and creates a barrier and isolation effect on the peeling initiation point, preventing peeling defects in a single sub-coating from spreading to the surrounding area. This overall improves the interfacial bonding strength and peel resistance between the coating and the current collector. Simultaneously, the independently arranged patterned sub-coatings can form a multi-level spatial structure with dispersed intervals within themselves and between each other, creating multi-channel radial diffusion paths for sodium ions. This improves the dispersion of ion diffusion paths, reduces diffusion resistance, promotes multi-directional and all-round electrolyte wetting, balances the electric field distribution on the electrode surface, effectively reduces interfacial impedance, and improves the electrochemical performance of the battery. Furthermore, the gap space formed by the independent and unconnected patterned sub-coatings can buffer the volume deformation caused by the sodium ion intercalation and deintercalation process, disperse the stress concentration effect, and effectively reduce the risk of electrode cracking and deformation failure. At the same time, the dispersed multi-channel structure can provide a partitioned deposition space for sodium ions, guide sodium ions to nucleate and grow separately in independent microchannels, avoid local ion aggregation and enrichment, and improve the uniformity of sodium metal deposition.

[0026] 2. The patterned stack of at least two patterned layers on the current collector surface of the electrode sheet in this application can increase the effective loading area of ​​the active material, reduce the proportion of ineffective inactive interfaces, increase the sodium ion storage capacity per unit area, and effectively improve the battery energy density; it can also shorten the sodium ion diffusion distance, accelerate the electron transport rate, and improve the kinetic efficiency of sodium ion insertion / extraction reactions. The multi-layer patterned layers can further enhance the overall adhesion stability of the coating, suppress material shedding caused by volume fluctuations during charging and discharging, and the interlayer and intralayer void structures can synergistically absorb insertion / extraction stress, further disperse the volume expansion effect, stabilize the overall electrode structure, and extend the battery cycle life.

[0027] In addition, the patterned stacking gives the electrode a larger specific surface area, which not only provides more nucleation sites for uniform sodium ion deposition, but also reduces the sodium nucleation barrier, further promoting uniform sodium ion deposition and reducing the risk of dendrite puncture short circuit. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying 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.

[0029] Figure 1 This is a side view of an electrode sheet provided in Embodiment 1 of this application; Figure 2 This is a top view of the first patterned layer provided in Embodiments 1 and 2 of this application; Figure 3 This is a top view of the first patterned layer provided in Embodiment 3 of this application.

[0030] The following is supplementary explanation of the attached figures: 1-Current collector; 2-First patterned layer; 3-Second patterned layer; 4-Third patterned layer. Detailed Implementation

[0031] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0032] The term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of this application. In the description of this application, it should be understood that the terms "upper," "lower," "top," "bottom," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this application 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 application. 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 indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Moreover, the terms "first," "second," etc., are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein.

[0033] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are included. For example, a specified range from “1 to 10” should be considered to include any and all subranges between the minimum value 1 and the maximum value 10. Exemplary subranges of the range 1 to 10 include, but are not limited to, 1 to 6.1, 3.5 to 7.8, 5.5 to 10, etc.

[0034] This application provides an electrode for a sodium-ion battery, comprising a current collector 1 and a patterned stack disposed on at least one surface thereon. Specifically, the patterned stack can be disposed on only a single surface of the current collector 1 (forming a single-sided patterned electrode), or it can be disposed on both the upper and lower surfaces of the current collector 1 (forming a double-sided patterned electrode). When disposed on both surfaces, the patterned stacks on the upper and lower surfaces can be symmetrical to each other, or they can be configured with different pattern shapes, areas, or stack thicknesses according to electrochemical performance requirements. The patterned stack comprises at least two patterned layers stacked along the thickness direction, with adjacent patterned layers having partially or completely overlapping regions in the plane direction of the current collector 1. Each patterned layer includes multiple independent and unconnected patterned sub-coatings, and the multiple patterned sub-coatings within the same patterned layer are discretely distributed or concentrically nested. In this context, "independent and unconnected" means that there is no direct physical connection between any two patterned sub-coatings within the same patterned layer, and there is a gap between adjacent sub-coatings. This gap represents an uncoated exposed area, used to expose the patterned layer on or beneath the current collector 1. "Discrete distribution" refers to multiple patterned sub-coatings arranged randomly or in a regular array, with each patterned sub-coating separated from the others and without geometric inclusion or nesting relationships. "Concentric nested distribution" refers to multiple patterned sub-coatings having a common geometric center, arranged in concentric rings, with radial spacing between adjacent sub-coatings. Specifically, radial spacing refers to the distance along the radial direction from the outer edge of the inner ring to the inner edge of the outer ring.

[0035] The patterned stack in this application includes at least two patterned layers stacked along the thickness direction. Through this layered arrangement, the multi-layered patterned design increases the effective loading area of ​​the active material while reducing the proportion of inactive interfaces, allowing more sodium ions to be stored per unit area, thereby improving energy density. The layered patterned layers also shorten the diffusion path of sodium ions and accelerate the electron transport rate, thus improving the sodium ion insertion / extraction efficiency. Furthermore, the multi-layered patterned design of this invention can also enhance the bonding strength between the coating and the current collector, suppressing material shedding due to volume changes during charging and discharging, and improving the stability of the electrode structure. The gaps between adjacent patterned layers, the gaps between patterned sub-coatings within each patterned layer, and the internal hollow regions can absorb the stress caused by sodium ion insertion / extraction, dispersing the concentration effect of volume expansion, thereby reducing the risk of electrode cracking and extending the cycle life of the sodium-ion battery. In addition, compared with the electrode sheets in the prior art, the electrode sheet provided by the present invention has a higher specific surface area due to the presence of the patterned layer in the patterned stack. This not only provides more nucleation sites for uniform sodium ion deposition, but also reduces the sodium nucleation barrier, further promoting uniform sodium ion deposition and reducing the risk of dendrite puncture short circuit.

[0036] Furthermore, by setting each patterned sub-coating to be independent and unconnected, this application can reduce the mutual influence between coatings and the stress at the interface, effectively hindering and separating the spread of peeling initiation points, and preventing the potential peeling of a single patterned sub-coating from extending to other sub-coatings, thereby improving the overall peeling strength. Simultaneously, multiple independent and unconnected patterned sub-coatings form dispersed, spaced, and independent spaces within and between them. These spaces, on the one hand, form dispersed and spaced radial diffusion paths for sodium ions, increasing the number of diffusion paths between sub-coatings and improving the dispersion of diffusion paths, thereby reducing the diffusion resistance of sodium ions; on the other hand, they facilitate multidirectional wetting of the electrolyte within and between the sub-coatings and promote a more uniform electric field distribution on the electrode surface, thereby helping to reduce interface impedance and improve the battery's electrical performance. In addition, the independent and unconnected patterned sub-coatings can effectively disperse the volume expansion stress generated during charging and discharging, and the spaces between and within the sub-coatings can absorb the stress caused by sodium ion insertion / extraction, reducing the risk of electrode cracking. At the same time, it provides more dispersed multi-channel deposition sites, allowing sodium ions to be deposited separately in multiple smaller independent channels, inducing uniform sodium ion deposition, inhibiting metal aggregation, reducing the risk of dendrite puncture short circuits, and improving the uniformity of sodium metal deposition.

[0037] It should be noted that the patterned sub-coatings in this application can adopt two parallel and alternative distribution methods: discrete distribution and concentric nested distribution. In the discrete distribution method, the annular sub-coatings have an internal hollow region enclosed by their inner boundaries, and there are gaps between adjacent annular sub-coatings. The hollow region and gaps are uncoated areas, serving as sodium deposition sites. The multiple annular sub-coatings are independently and unconnected, which is beneficial for forming a uniform distribution of deposition sites and reducing local current density. In the concentric nested distribution method, the multiple annular sub-coatings have a common geometric center and are arranged in a concentric ring shape. There is a radial spacing between adjacent annular sub-coatings, which can form a gradient distribution of deposition sites and continuous ion transport channels along the radial direction, which is beneficial for dispersing current density, suppressing dendrite growth, and uniformly dispersing deposition stress. Both of the above distribution methods can be used in conjunction with the multilayer patterned stacked structure of this application.

[0038] In some preferred embodiments, multiple patterned sub-coatings located within the same patterned layer are discretely distributed along the planar direction of the current collector 1, and at least one patterned layer contains multiple patterned sub-coatings that are annular. Each annular sub-coating has an internal hollow region enclosed by its inner boundary, which is an uncoated region used for sodium metal deposition. Furthermore, the gaps between adjacent annular sub-coatings are also uncoated regions, similarly used for sodium metal deposition. The internal hollow regions of the annular sub-coatings and the gaps between adjacent annular sub-coatings together constitute multi-level, independent active sites. Their synergistic effect effectively suppresses the lateral growth and aggregation of sodium dendrites, thereby reducing the risk of short circuits. Simultaneously, the multi-level active sites increase the number of reaction sites per unit area, which is beneficial for achieving a thin, uniform distribution of sodium, thereby improving capacity utilization and distribution uniformity. In addition, the internal hollow regions and inter-ring gaps form dispersed and interconnected ion transport channels, which helps reduce concentration polarization and improve the rate performance of the battery. This structure can also effectively absorb the volume expansion stress generated during charging and discharging, reducing the risk of electrode cracking.

[0039] In some preferred embodiments with a discrete distribution, the ring width of each annular sub-coating is 0.5 to 200 μm, for example, but not limited to 0.5 μm, 1.5 μm, 5 μm, 10 μm, 20 μm, 50 μm, 80 μm, 100 μm, 150 μm, and 200 μm. Preferably, the ring width is 1 to 150 μm or 1.5 to 100 μm; the thickness is 2 to 30 μm, for example, but not limited to 2 μm, 5 μm, 8 μm, 10 μm, 15 μm, 20 μm, 25 μm, and 30 μm; and the edge gap between adjacent annular sub-coatings located in the same patterned layer is 1 to 200 μm, for example, but not limited to 1 μm, 5 μm, 10 μm, 20 μm, 50 μm, 80 μm, 100 μm, 120 μm, 150 μm, 180 μm, and 200 μm.

[0040] Firstly, when the ring width is 0.5~200μm, it can optimize ion transport channels, shorten diffusion paths, and enhance stress buffering capacity, while promoting gradient wetting of the electrolyte and ensuring sufficient peel strength between the coating and current collector 1, thus improving the performance of sodium-ion batteries. However, if the ring width is too small (less than 0.5μm), the mechanical integrity of the annular sub-coating may be insufficient, making it prone to breakage or detachment during coating or charge / discharge processes, and difficult to maintain a complete annular structure. If the ring width is too large (greater than 200μm), on the one hand, it will increase the lateral diffusion distance of sodium ions inside the annular coating, increasing diffusion resistance; on the other hand, it will excessively occupy the surface area of ​​current collector 1, reducing the effective active site density per unit area, which is not conducive to improving deposition capacity and deposition uniformity.

[0041] Secondly, when the ring height is 2~30μm, it can also optimize ion transport channels, shorten diffusion paths, and enhance stress buffering capacity, while promoting gradient wetting of the electrolyte and ensuring sufficient peel strength between the coating and current collector 1, which is beneficial to improving the performance of sodium-ion batteries. However, if the thickness is too small (less than 2μm), the mechanical strength of the ring sub-coating may be insufficient, making it difficult to maintain shape stability during multilayer stacking and charge / discharge processes; at the same time, an excessively thin coating cannot provide sufficient volume expansion buffering capacity. If the thickness is too large (greater than 30μm), the effective diffusion distance of sodium ions inside the coating increases, thereby increasing diffusion resistance and reducing transport efficiency; in addition, an excessively thick coating is prone to generating large internal stress during charge / discharge processes, increasing the risk of cracking.

[0042] Secondly, regarding the setting of the edge gap (1~200μm). If the edge gap is too small (less than 1μm), physical contact or connection can easily occur between adjacent annular sub-coatings, thereby destroying the independent and unconnected structural characteristics; at the same time, an excessively narrow gap will restrict the wetting of the electrolyte and the ion diffusion channels in the planar direction, reducing ion transport efficiency. If the edge gap is too large (greater than 200μm), it will excessively occupy the surface area of ​​the current collector, which may lead to a reduction in the number of annular sub-coatings per unit area and a decrease in the density of deposition sites, thereby reducing the deposition capacity and uniformity; at the same time, an excessively large gap will also reduce the coverage density of the effective functional area.

[0043] In some preferred embodiments with a discrete distribution, the shape of each annular sub-coating is selected from at least one of circular rings, elliptical rings, triangular rings, quadrilateral rings, pentagonal rings, or hexagonal rings. Specifically, triangular rings include, but are not limited to, equilateral triangular rings, isosceles triangular rings, or any irregular triangular ring; quadrilateral rings include, but are not limited to, rectangular rings, trapezoidal rings, rhomboid rings, or parallelogram rings; pentagonal rings include, but are not limited to, regular pentagonal rings or irregular pentagonal rings; and hexagonal rings include, but are not limited to, regular hexagonal rings or irregular hexagonal rings. Typical but non-limiting shape combinations include: combinations of triangular and quadrilateral rings, combinations of pentagonal and hexagonal rings, combinations of circular and elliptical rings, or combinations of triangular, quadrilateral, hexagonal, and circular rings.

[0044] The different shapes of the annular sub-coatings mentioned above can be flexibly selected according to actual process requirements. By increasing the inner boundary perimeter and interstitial boundary length of the sub-coating, more abundant ion transport interfaces and deposition sites can be provided, thereby further optimizing the ion diffusion path and improving the uniformity of sodium deposition.

[0045] Furthermore, the equivalent circular diameter of the internal hollow region of each annular sub-coating is 0.5~50μm, for example, but not limited to 0.5μm, 1μm, 2μm, 5μm, 8μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, and 50μm; wherein, the equivalent circular diameter refers to the diameter of a circle with the same area as the internal hollow region.

[0046] By limiting the scope as described above, the electrolyte inside and outside the ring-shaped sub-coating can be rationally distributed, which is beneficial for multidirectional wetting and uniform electric field distribution of the electrolyte inside and between the sub-coatings. This helps to further reduce interfacial impedance and improve electrochemical performance. It also avoids potential problems such as poor wetting and uneven electric field distribution caused by too little or too much electrolyte inside the ring-shaped sub-coating.

[0047] Furthermore, a well-designed internal hollow region is beneficial for further improving deposition uniformity. Multiple independent and unconnected patterned sub-coatings constitute a uniformly dispersed multi-channel structure, allowing sodium ions to deposit separately in different channels, preventing aggregation and improving deposition uniformity.

[0048] In some preferred embodiments where the distribution is discrete, at least one patterned layer includes at least two hexagonal ring sub-coatings, and any two hexagonal ring sub-coatings are not nested. Compared to circular, elliptical, triangular, quadrilateral, or pentagonal ring structures, hexagonal ring sub-coatings can provide a longer total boundary length within the same area, which is beneficial for providing abundant sodium deposition sites, reducing local current density, and suppressing dendrite growth. Simultaneously, hexagonal rings have good close-packing characteristics, enabling efficient arrangement within a plane.

[0049] In some preferred embodiments, multiple patterned sub-coatings located within the same patterned layer are concentrically nested in the planar direction of the current collector 1. Specifically, at least one patterned layer includes at least two concentric annular sub-coatings, with a radial spacing of 1~200μm between adjacent annular sub-coatings, such as, but not limited to, 100μm, 110μm, 120μm, 130μm, 140μm, 150μm, 160μm, 170μm, 180μm, 190μm, and 200μm. Preferably, the radial spacing is 10~200μm, or 100~200μm, etc. The ring width of each annular sub-coating is 0.5~200μm, and the thickness is 2~30μm. The above parameter ranges are the same as those for discretely distributed patterned sub-coatings, and will not be repeated here.

[0050] Similarly, in some preferred embodiments with a concentric nested distribution, the shape of each annular sub-coating is selected from at least one of a circular ring, an elliptical ring, a triangular ring, a quadrilateral ring, a pentagonal ring, or a hexagonal ring. Specifically, triangular rings include, but are not limited to, equilateral triangular rings, isosceles triangular rings, or any irregular triangular ring; quadrilateral rings include, but are not limited to, rectangular rings, square rings, trapezoidal rings, rhomboid rings, or parallelogram rings; pentagonal rings include, but are not limited to, regular pentagonal rings or irregular pentagonal rings; and hexagonal rings include, but are not limited to, regular hexagonal rings or irregular hexagonal rings. Therefore, regardless of whether a discrete or concentric nested distribution is used, the shape of the annular sub-coating can be flexibly selected to adapt to different process requirements.

[0051] The aforementioned annular sub-coating can have a uniform ring width, meaning that the width of the same annular sub-coating is basically the same at all points; or it can have a non-uniform ring width, meaning that the width varies at different locations, in order to adapt to specific electric field distributions or ion transport requirements.

[0052] In some preferred embodiments with a concentric nested distribution, each patterned layer includes at least two concentric annular sub-coatings. This allows for the formation of radially gradient-distributed sodium deposition sites and continuous ion transport channels, which helps to disperse local current density and suppress dendrite growth. Simultaneously, the symmetrical structure of the concentric rings can uniformly disperse the stress generated during deposition, thereby improving the structural stability of the electrode.

[0053] In some preferred embodiments, the thickness of the patterned stack is 20~100μm, such as, but not limited to, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, and 100μm. If the thickness is less than 20μm, the mechanical strength of the coating may be insufficient, and it is prone to cracking or peeling under the stress generated by the volume expansion of sodium deposition; if the thickness is greater than 100μm, since the coating material usually has low ionic conductivity, sodium ions need to pass through a longer coating path to reach the surface of current collector 1, resulting in an increased ion transport path and increased battery internal resistance, which is detrimental to the rate performance and cycle stability of the battery.

[0054] In some preferred embodiments, the blank area ratio in each patterned layer is 20% to 70%; whereby the blank area ratio refers to the proportion of the area of ​​the region not covered by the patterned sub-coating (i.e., the uncoated exposed area) within the same patterned layer to the total area of ​​a single side of the current collector 1. For example, but not limited to, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or 70%. It should be noted that this range of 20% to 70% refers to the percentage of the sum of the areas of all uncoated exposed areas (i.e., the internal hollow areas of the annular sub-coatings and the gaps between adjacent annular sub-coatings) in a single patterned layer to the surface area of ​​that side of the current collector 1. If the proportion is too low (below 20%), there are insufficient deposition sites, which can easily lead to excessively high local current density and induce dendrites; if the proportion is too high (above 70%), the coating control effect is weakened, and the deposition stress distribution is uneven. By controlling the blank area ratio within the range of 20% to 70%, a good balance can be achieved between providing sufficient deposition sites and leveraging the spatial confinement effect of the coating, thereby optimizing the uniformity of sodium deposition and the structural stability of the electrode.

[0055] In some preferred embodiments, each patterned layer comprises structural material and functional material; The structural material is selected from at least one of covalent organic framework materials, metal-organic framework materials, metal oxides, metal fluorides, hard carbon, silicon oxide, or silicon carbon. Typical but non-limiting combinations include: combinations of covalent organic framework materials and metal-organic framework materials, combinations of metal oxides and metal fluorides, combinations of hard carbon and silicon carbon, or combinations of metal-organic framework materials, metal oxides, and silicon oxide. The structural material constitutes 30% to 70% of the mass of the patterned layer.

[0056] Functional materials include conductive agents and binders; The conductive agent is selected from at least one of conductive graphite, carbon black, carbon nanotubes, or graphene. Typical but non-limiting combinations include: a combination of conductive graphite and carbon black, a combination of carbon nanotubes and graphene, a combination of carbon black and carbon nanotubes, or a combination of conductive graphite, carbon nanotubes, and graphene. The conductive agent constitutes 10% to 60% of the mass of the patterned layer.

[0057] The binder is selected from at least one of polyvinylidene fluoride, polyacrylic acid, polyvinyl alcohol, polyimide, polytetrafluoroethylene, sodium carboxymethyl cellulose, or styrene-butadiene rubber. Typical but non-limiting combinations include: combinations of polyvinylidene fluoride and polyacrylic acid, combinations of polyvinyl alcohol and polyimide, combinations of polytetrafluoroethylene and sodium carboxymethyl cellulose, or combinations of polyvinylidene fluoride, polyacrylic acid, and styrene-butadiene rubber. The binder constitutes 10% to 60% of the mass of the patterned layer.

[0058] In some preferred embodiments, the patterned stack comprises 2 to 50 patterned layers; When the patterned stack comprises at least three patterned layers, along the direction away from current collector 1: at least one of the following parameters in each patterned layer of the patterned stack exhibits a gradient change: The blank area ratio in each patterned layer first decreases and then increases layer by layer. The content of structural material in each patterned layer increases layer by layer and then decreases layer by layer. The content of functional materials in each patterned layer decreases layer by layer and then increases layer by layer.

[0059] Through the gradient distribution of blank area ratio, structural material content, and functional material content, different patterned layers can play a synergistic role in the cycling process. The blank area of ​​each patterned layer decreases layer by layer initially and then increases layer by layer: for example, the bottom layer near the current collector has a higher blank area ratio, at 15% ± 2%; the middle layer has a lower blank area ratio, at 5% ± 1%; and the surface layer again has a higher blank area ratio, at 15% ± 2%. Based on this distribution, the bottom layer, due to its high blank area ratio, has a high electronic conductivity network connectivity on current collector 1, which is beneficial for reducing interfacial impedance; the middle patterned layer can form an ion sieve effect, blocking solvated Na. + The surface layer also has a high blank area ratio, and the electrolyte wetting speed is fast, which helps to improve high-rate performance.

[0060] Furthermore, along the direction away from the current collector, the content of structural materials in each patterned layer first increases and then decreases, while the content of functional materials first decreases and then increases, forming an alternating soft and hard layered structure of the patterned sub-coatings. This structure creates an alternating soft and hard buffer network within the sub-coatings and between different patterned layers, which helps improve mechanical buffering capacity and reduce stress concentration points. This effectively suppresses the adverse effects of particle breakage caused by negative electrode expansion on battery performance, further enhancing the cycle stability of sodium-ion batteries. Simultaneously, the patterned layers closer to the current collector have a higher proportion of binder, resulting in stronger adhesion and effectively improving the peel strength between the coating and the current collector, thereby enhancing the structural stability of the electrode during cycling.

[0061] In some preferred embodiments, the absolute difference between any two adjacent patterns in the blank area ratio of each patterned layer is 5% to 10%. And / or, the absolute difference between any two adjacent layers in the content of structural material in each patterned layer is 5% to 10%; And / or, the absolute difference between any two adjacent layers in the content of functional materials in each patterned layer is 5% to 10%.

[0062] In each patterned layer, the absolute difference between any two adjacent layers in terms of blank area ratio, structural material content, and functional material content is independently 5% to 10%. If the absolute difference is less than 5%, the difference between adjacent layers is too small to achieve the purpose of setting up layered patterns; if it is greater than 10%, the difference between adjacent layers is too large, posing a risk of layer collapse and causing the layer structure to be unstable.

[0063] This application also provides a method for preparing a sodium-ion battery electrode, comprising the following steps: At least two patterned layers are formed layer by layer on at least one surface of the current collector 1 using a patterned deposition process. In this process, when forming each patterned layer, multiple independent and unconnected patterned sub-coatings are deposited on the surface of the current collector 1 or on the already formed patterned layer, and the multiple patterned sub-coatings in the same patterned layer are distributed discretely or concentrically nested. Furthermore, when forming two adjacent patterned layers, the subsequent patterned layer partially or completely overlaps with the preceding patterned layer in the plane direction of the current collector 1. Partial overlap means that the subsequent patterned sub-coating only covers a portion of the corresponding area of ​​the preceding sub-coating. The subsequent sub-coating can be offset relative to the preceding sub-coating, thereby covering the inner, outer, or alternating areas of the preceding sub-coating. Complete overlap means that the projection of the subsequent patterned sub-coating in the plane direction of the current collector 1 completely coincides with the corresponding area of ​​the preceding sub-coating, i.e., each sub-coating layer is stacked one-to-one in the vertical direction. In the same patterned stack, the overlap methods between different layers can be the same or different. For example, some patterned layers may completely overlap, while others may partially overlap, or the molecular coating within the same patterned layer may completely overlap with the preceding layer, while some sub-coatings may partially overlap with the preceding layer.

[0064] In some preferred embodiments, the deposition method includes 3D printing. Specifically, a three-dimensional printing path can be generated based on a preset patterned layer geometry, and then patterned sub-coatings can be deposited layer by layer on the surface of the current collector 1 or on the already formed patterned layer.

[0065] This application also provides a sodium-ion battery, including the aforementioned electrode. The electrode is located on the negative electrode side of the battery and has the structure described above, including a current collector 1 and a patterned stack disposed on its surface. The patterned stack includes at least two patterned layers with partially or completely overlapping areas between adjacent layers. Each layer consists of multiple independent and unconnected patterned sub-coatings, distributed discretely or concentrically. This sodium-ion battery can employ a negative electrode-less design, meaning that no sodium metal layer is pre-formed on the negative electrode side. During the first charge, sodium ions from the positive electrode migrate to the negative electrode side, depositing a sodium metal layer in situ in the uncoated exposed areas (sub-coating gaps and hollow areas) of the patterned electrode. This battery can achieve uniform sodium deposition, suppress dendrite growth, and buffer volume expansion stress.

[0066] The following detailed description of examples of this application is exemplary and is used only to explain this application, and should not be construed as limiting this application.

[0067] Example 1 This embodiment provides an electrode for a sodium-ion battery. The electrode includes a current collector 1 with a thickness of 13 μm, and patterned stacked layers with a thickness of 90 μm disposed on two surfaces of the current collector 1. Figure 1 As shown, the patterned overlay includes three patterned layers stacked together: a first patterned layer 2, a second patterned layer 3, and a third patterned layer 4. Wherein, as... Figure 2 As shown, the patterned sub-coatings in each patterned layer are concentrically nested annular sub-coatings. Each annular sub-coating has a ring width of 20 μm and a thickness of 10 μm, with a radial spacing of 10 μm between adjacent annular sub-coatings. Specifically, the blank area ratio of the first patterned layer 2 is 15%, the blank area ratio of the second patterned layer 3 is 8%, and the blank area ratio of the third patterned layer 4 is 15%.

[0068] Each patterned layer contains both structural and functional materials. The structural materials are all hard carbon; the functional materials include conductive agents and binders. The conductive agents are all conductive graphite, and the binders are all mixtures of sodium carboxymethyl cellulose and styrene-butadiene rubber.

[0069] This embodiment also provides a method for preparing the above-mentioned sodium-ion battery electrode, which specifically includes the following steps: (1) Mix the structural material (hard carbon) and functional material (binder and conductive agent (conductive carbon black)) in the following proportions, add deionized water as solvent, stir evenly, and prepare coating slurry A and coating slurry B with a solid content of 40% respectively.

[0070] In the coating slurry A, the mass ratio of hard carbon, binder and conductive agent is 40:40:20, the binder is a mixture of sodium carboxymethyl cellulose and styrene-butadiene rubber in a mass ratio of 1:2, and the slurry viscosity is 8000 Pa·s.

[0071] In coating slurry B, the mass ratio of hard carbon, binder and conductive agent is 60:20:20. The binder is a mixture of sodium carboxymethyl cellulose and styrene-butadiene rubber in a mass ratio of 1:2. The viscosity of the slurry is 7000 Pa·s.

[0072] (2) On one surface of current collector 1 (aluminum foil), a coating slurry A is first deposited using 3D printing to form a coating slurry A, as shown in the figure. Figure 2 The first patterned layer 2 is shown. Then, a coating slurry B is deposited using 3D printing to form a second patterned layer 3 on the first patterned layer 2, with the first patterned layer 2 and the second patterned layer 3 partially overlapping. Next, a coating slurry A is deposited again using 3D printing to form a third patterned layer 4 on the second patterned layer 3, with the second patterned layer 3 and the third patterned layer 4 completely overlapping. After deposition, the first patterned layer 2, the second patterned layer 3, and the third patterned layer 4 on the current collector 1 are dried at 80°C.

[0073] (3) On the other surface of current collector 1 (aluminum foil), perform the same patterning deposition process as described in step (2) above, and then cut to obtain an electrode sheet.

[0074] Example 2 Referring to the electrode and its preparation method in Example 1, the difference is that the thickness of the patterned stack is 100 μm, comprising five patterned layers stacked together: a first patterned layer, a second patterned layer, a third patterned layer, a fourth patterned layer, and a fifth patterned layer. The blank areas of each patterned layer are 20%, 15%, 10%, 15%, and 20%, respectively. In addition to coating slurries A and B, this embodiment also includes coating slurry C, whose formulation is a hard carbon, binder and conductive agent in a mass ratio of 50:30:20. The binder is a mixture of sodium carboxymethyl cellulose and styrene-butadiene rubber in a mass ratio of 1:2, with a viscosity of 6000 Pa·s. The layers are deposited sequentially as follows: first, slurry A is deposited to form a first patterned layer; then, slurry C is deposited to form a second patterned layer, which partially overlaps with the first patterned layer; next, slurry B is deposited to form a third patterned layer, which completely overlaps with the second patterned layer; then, slurry C is deposited to form a fourth patterned layer, which completely overlaps with the third patterned layer; finally, slurry A is deposited to form a fifth patterned layer, which partially overlaps with the fourth patterned layer.

[0075] Example 3 Referring to the electrode and its preparation method in Example 1, the difference is that the thickness of the patterned stack is 90 μm, including five patterned layers stacked together, namely a first patterned layer, a second patterned layer, a third patterned layer, a fourth patterned layer, and a fifth patterned layer. Figure 3 As shown, the patterned sub-coatings in each patterned layer are discretely distributed hexagonal ring-shaped sub-coatings. Each hexagonal ring-shaped sub-coating has a ring width of 20 μm and a thickness of 10 μm, with a 10 μm gap between adjacent hexagonal ring-shaped sub-coatings. The blank area ratios of each patterned layer are as follows: first patterned layer 20%, second patterned layer 15%, third patterned layer 10%, fourth patterned layer 15%, and fifth patterned layer 20%.

[0076] This embodiment uses three coating slurries, A, B, and C, each with a solid content of 40% and viscosities of 8000 Pa·s, 7000 Pa·s, and 6000 Pa·s, respectively. The structural material is a mixture of magnesium fluoride (MgF2) and calcium oxide (CaO). The specific composition ratios of the three slurries are as follows: In coating slurry A, the structural material (MgF2:CaO=12:1), binder (sodium carboxymethyl cellulose: styrene-butadiene rubber=2:0.5), and conductive agent (SP) are mixed in a mass ratio of 40:40:20; in coating slurry B, the structural material (MgF2:CaO=13:0.7), binder (sodium carboxymethyl cellulose: styrene-butadiene rubber=1.4:0.5), and conductive agent (SP) are mixed in a mass ratio of 60:20:20; in coating slurry C, the structural material (MgF2:CaO=14:0.6), binder (sodium carboxymethyl cellulose: styrene-butadiene rubber=1.2:0.5), and conductive agent (SP) are mixed in a mass ratio of 50:30:20.

[0077] The deposition sequence is as follows: the first patterning layer uses coating slurry A; the second patterning layer uses coating slurry C and partially overlaps with the first patterning layer; the third patterning layer uses coating slurry B and completely overlaps with the second patterning layer; the fourth patterning layer uses coating slurry C and completely overlaps with the third patterning layer; and the fifth patterning layer uses coating slurry A and partially overlaps with the fourth patterning layer.

[0078] Example 4 Referring to the electrode and its preparation method in Example 1, the difference is that the thickness of the patterned stack is 20 μm, comprising five patterned layers stacked together: a first patterned layer, a second patterned layer, a third patterned layer, a fourth patterned layer, and a fifth patterned layer. The patterned sub-coatings in each patterned layer are discretely distributed triangular ring-shaped sub-coatings. The blank area ratio, ring width, thickness, and edge gap between adjacent triangular ring sub-coatings of each patterned layer are as follows: First patterned layer: blank area ratio 15%, ring width 200μm, thickness 5μm, edge gap 200μm; Second patterned layer: blank area ratio 50%, ring width 100μm, thickness 2μm, edge gap 100μm; Third patterned layer: blank area ratio 30%, ring width 150μm, thickness 8μm, edge gap 150μm; Fourth patterned layer: blank area ratio 50%, ring width 100μm, thickness 2μm, edge gap 100μm; Fifth patterned layer: blank area ratio 70%, ring width 80μm, thickness 3μm, edge gap 80μm.

[0079] Three coating slurries, A, B, and C, were used, each with a solid content of 40% and viscosities of 9000 Pa·s, 8000 Pa·s, and 7000 Pa·s, respectively. All used ZIF-8 metal-organic frameworks as structural materials and carbon nanotube conductive agents and polyvinylidene fluoride binders as functional materials. The specific composition ratios of the three coating slurries are as follows: In coating slurry A, the mass ratio of structural material, binder (polyvinylidene fluoride), and conductive agent (carbon nanotubes) is 11:4:0.5; in coating slurry B, the mass ratio is 12:3:0.5; and in coating slurry C, the mass ratio is 13:2.1:0.5.

[0080] The deposition sequence is as follows: the first patterning layer uses coating slurry A; the second patterning layer uses coating slurry B and partially overlaps with the first patterning layer; the third patterning layer uses coating slurry C and completely overlaps with the second patterning layer; the fourth patterning layer uses coating slurry B and completely overlaps with the third patterning layer; and the fifth patterning layer uses coating slurry A and partially overlaps with the fourth patterning layer.

[0081] Example 5 Referring to the electrode sheet and its preparation method in Example 3, the difference is that the hexagonal annular sub-coating in each patterned layer is replaced with a hexagonal solid sub-coating. That is, the hexagonal solid sub-coating is not only coated on the annular part, but also filled with coating in the internal area enclosed by the annular part.

[0082] Example 6 Referring to the electrode and its preparation method in Example 1, the difference is that the ring width of the annular sub-coating in each patterned layer is 0.1 μm.

[0083] Example 7 Referring to the electrode and its preparation method in Example 1, the difference is that the ring width of the annular sub-coating in each patterned layer is 280 μm.

[0084] Example 8 The electrode and its preparation method are the same as in Example 1, except that the thickness of the annular sub-coating in each patterned layer is 1 μm.

[0085] Example 9 The electrode and its preparation method are the same as in Example 1, except that the thickness of the annular sub-coating in each patterned layer is 40 μm.

[0086] Example 10 Referring to the electrode and its preparation method in Example 1, the difference is that the radial spacing between adjacent annular sub-coatings in each patterned layer is 50 μm.

[0087] Example 11 Referring to the electrode and its preparation method in Example 1, the difference is that the radial spacing between adjacent annular sub-coatings in each patterned layer is 300 μm.

[0088] Example 12 Referring to the electrode and its preparation method in Example 1, the difference is that the positions of the second patterned layer and the first patterned layer are interchanged. Specifically, along the direction away from the current collector 1, the blank area ratio of the patterned layer in the patterned stack shows a trend of increasing from small to large and then remaining constant, the content of structural material first decreases and then remains constant, and the content of functional material first increases and then remains constant. Accordingly, in step (2) of the preparation method, coating slurry B is first deposited on current collector 1, and then coating slurry A is deposited twice in sequence.

[0089] Example 13 Referring to the electrode and its preparation method in Example 1, the difference is that the positions of the third patterned layer and the second patterned layer are interchanged. Specifically, along the direction away from the current collector 1, the blank area of ​​the patterned layer in the patterned stack first remains unchanged and then decreases, the content of the structural material first remains unchanged and then increases, and the content of the functional material first remains unchanged and then decreases. Accordingly, in step (2) of the preparation method, coating slurry A is deposited twice on the surface of the current collector 1, and then coating slurry B is deposited once.

[0090] Comparative Example 1 Referring to the electrode and its preparation method in Example 1, the difference is that the second and third patterned layers are omitted, and the thickness of the first patterned layer is increased to 90 μm.

[0091] Comparative Example 2 Referring to the electrode and its preparation method in Example 1, the difference is that the first patterned layer is replaced with a continuous coating of equal thickness that covers the entire surface of the current collector 1; the second patterned layer is replaced with a continuous coating of equal thickness that covers the entire surface of the first patterned layer; and the third patterned layer is replaced with a continuous coating of equal thickness that covers the entire surface of the second patterned layer.

[0092] Comparative Example 3 Referring to the electrode and its preparation method in Example 1, the difference is that the first patterned layer, the second patterned layer and the third patterned layer are omitted, and the current collector 1 is directly used as the electrode.

[0093] Comparative Example 4 Referring to the electrode and its preparation method in Example 1, the difference is that the second and third patterned layers are omitted, and the first patterned layer is replaced with a continuous coating with a thickness of 90 μm that covers the entire surface of the current collector 1.

[0094] Comparative Example 5 Referring to the electrode sheet and its preparation method in Example 3, the difference is that the hexagonal ring sub-coatings in each patterned layer are arranged in an interconnected manner, that is, the adjacent hexagonal ring sub-coatings are arranged without gaps.

[0095] Test case For the electrode sheets prepared in Examples 1-13 and Comparative Examples 1-5, the coating peel strength was first tested. A universal testing machine was used, and according to ASTM D903 standard, the coating was peeled from the current collector surface at a peel angle of 180°, with a peel speed of 200 mm / min and a test temperature of 25 ± 2℃. The electrode sheets were cut into strips with a width of 25 mm and an effective peel length of 80 mm. Three parallel samples of each type of electrode sheet were tested, and the average peel force was recorded and the arithmetic mean was calculated. The resulting peel strengths are shown in Table 1.

[0096] The electrodes provided in Examples 1-13 and Comparative Examples 1-5 were used as the negative electrodes of sodium-ion batteries to assemble full cells for evaluation of their electrochemical performance. The specific preparation method of the sodium-ion battery is as follows: Positive electrode preparation: Sodium iron pyrophosphate positive electrode active material, conductive carbon black conductive agent, and polyvinylidene fluoride binder were mixed at a mass ratio of 96:1:3. N-methylpyrrolidone was added as a solvent to prepare a slurry with a solid content of 50%, which was then stirred evenly to obtain the positive electrode slurry. The obtained positive electrode slurry was uniformly coated on one surface of a 15 μm thick carbon-coated aluminum foil, ensuring that the mass of the positive electrode active material on the positive electrode sheet was 15.0 g / cm³. 2The cathode material was dried at 70°C to obtain a positive electrode sheet with a single-sided coating of positive electrode slurry. The coating process was then repeated on the other surface to obtain a positive electrode sheet with a double-sided coating of positive electrode slurry. After coating, the positive electrode sheet was cold-pressed and cut into 56mm × 43mm pieces for later use. The compacted density of the resulting positive electrode sheet was 2.0 g / cm³. 3 .

[0097] Electrolyte preparation: In a glove box, ethylene carbonate, methyl ethyl carbonate and diethyl carbonate were mixed in a mass ratio of 30:50:20 to obtain a mixture. Sodium hexafluorophosphate was then added to the mixture, dissolved and mixed evenly to obtain an electrolyte with a sodium hexafluorophosphate concentration of 1.15 mol / L.

[0098] Separator: A polyethylene film with a thickness of 15μm is used as the separator.

[0099] Packaging materials: 113μm aluminum-plastic composite film provided by DNP is used as the packaging material.

[0100] Battery Assembly: The prepared positive electrode, separator, and negative electrode are placed in their corresponding positions on a desktop stacking machine, with the separator positioned between the positive and negative electrodes to provide isolation. The cells are then wound to obtain bare cells. Each bare cell consists of 5 positive electrode sheets and 6 negative electrode sheets. The bare cells are secured with tape to prevent electrode misalignment. An aluminum-plastic film is stamped to form a pit of appropriate depth under 10T pressure. The secured bare cells are placed in the pit for top-side sealing and tab welding. They are then dried in an 80℃ vacuum oven to remove moisture, injected with the prepared electrolyte, and undergo secondary encapsulation, settling, formation, and degassing processes to obtain a sodium-ion battery.

[0101] The obtained sodium-ion batteries were subjected to energy density and cycle performance tests. The energy density test method was as follows: using a battery testing system, the batteries were left to stand at 25±2℃ for 24 hours, then charged and discharged at a constant current of 0.2C, with a voltage range of 1.5~4.2V, for 3 cycles, and the stable value was taken. The energy density (Wh / kg) was calculated by discharging capacity (mAh / g) × average voltage (V) / battery mass (g, accuracy ±0.1mg), and the energy densities are shown in Table 1. The cycle performance test method was as follows: at 25±2℃, the batteries were charged and discharged at a constant current rate of 1C (voltage range 1.5~4.2V) for 200 cycles. After every 100 cycles, the discharge capacity was measured at a rate of 0.2C (cutoff voltage 1.5V), and the capacity retention rate (the percentage of capacity after the 200th cycle compared to the capacity of the first cycle) was calculated. The capacity retention rate of the sodium-ion batteries after 200 cycles is shown in Table 1.

[0102] Table 1

[0103] Based on the above test data, we can conclude that: (1) The coating on the electrode provided in Examples 1 to 4 of this application has a high peel strength (4.5 to 4.9 N / cm), indicating that the coating and the current collector have a strong bonding force. Meanwhile, the sodium-ion battery prepared by using the electrode provided in Examples 1 to 4 of this application as the negative electrode has a high energy density (271 to 274 Wh / kg) and good cycle stability (93.4% to 94.0%).

[0104] (2) A comparison between Example 3 (hexagonal annular sub-coating) and Example 5 (hexagonal solid sub-coating) shows that when the sub-coating in each patterned layer has an annular structure, it is more beneficial to improve the performance of sodium-ion batteries. Specifically, the energy density (272Wh / kg) and capacity retention rate (93.4%) of Example 3 are significantly higher than those of Example 5 (259Wh / kg, 88.2%), with the capacity retention rate increasing by about 5.2%. This is because the annular sub-coating reduces diffusion resistance by shortening the radial diffusion path of sodium ions and forms a continuous stress buffer zone, thereby alleviating stress concentration caused by volume expansion; at the same time, the internal hollow region enclosed by the inner boundary of the annular sub-coating can also promote electrolyte wetting and uniform electric field distribution, reduce interfacial impedance, and further improve the performance of sodium-ion batteries.

[0105] (3) A comparison of Examples 1 with Examples 6 and 7 shows that the ring width of the annular sub-coating in each patterned layer affects the performance of the sodium-ion battery. Example 1 (ring width 2 μm) had a peel strength of 4.8 N / cm, an energy density of 274 Wh / kg, and a capacity retention rate of 94.0%. Example 6 (ring width 0.1 μm) had a peel strength reduced to 3.8 N / cm, and both its energy density (268 Wh / kg) and capacity retention rate (91.6%) decreased. Example 7 (ring width 280 μm) also had lower energy density (263 Wh / kg) and capacity retention rate (91.4%) than Example 1. This indicates that a ring width of 0.5–200 μm is more conducive to improving the performance of the sodium-ion battery. This is because this width range can optimize ion transport channels, shorten diffusion paths, and enhance stress buffering capacity while promoting gradient wetting of the electrolyte and ensuring sufficient peel strength between the coating and the current collector.

[0106] (4) A comparison of Examples 1 with Examples 8 and 9 shows that the thickness of the annular sub-coating in each patterned layer affects the performance of the sodium-ion battery. Example 1 (thickness 30 μm) exhibits the best overall performance (274 Wh / kg, 94.0%); Example 8 (thickness 1 μm) shows significantly lower energy density (264 Wh / kg) and capacity retention (90.8%); the performance of Example 9 (thickness 40 μm) (266 Wh / kg, 92.5%) is also inferior to that of Example 1. This indicates that a thickness of 2-30 μm is more conducive to improving the performance of the sodium-ion battery. This is because this thickness range can optimize ion transport channels, shorten diffusion paths, and enhance stress buffering capacity while promoting gradient wetting of the electrolyte and ensuring sufficient peel strength between the coating and the current collector.

[0107] (5) A comparison of Example 1 with Examples 10 and 11 shows that the radial spacing between adjacent annular sub-coatings in each patterned layer affects the performance of the sodium-ion battery. Example 1 (spacing 100 μm) exhibits the best performance (274 Wh / kg, 94.0%); Example 10 (spacing 50 μm) shows a decrease in both energy density (261 Wh / kg) and capacity retention (91.9%); Example 11 (spacing 300 μm) also has lower peel strength (4.3 N / cm) and energy density (263 Wh / kg) than Example 1. This indicates that a radial spacing of 1~200 μm between adjacent annular sub-coatings is more conducive to improving the performance of the sodium-ion battery. This is because this spacing range can optimize ion transport channels, shorten diffusion paths, and enhance stress buffering capacity while ensuring that the coating has a suitable loading to maintain energy density.

[0108] (6) A comparison of Example 1 with Examples 12 and 13 shows that when the patterned stack includes at least three patterned layers stacked together, and along the direction away from the current collector, the blank area ratio of the patterned layers in the patterned stack changes from large to small and then to large, the content of structural materials first increases and then decreases, and the content of functional materials first decreases and then increases, it is more conducive to improving the performance of sodium-ion batteries. The energy density (274Wh / kg) and capacity retention (94.0%) of Example 1 (blank area ratio 50%→30%→50%) are both better than those of Example 12 (264Wh / kg, 90.7%) and Example 13 (261Wh / kg, 89.8%). This is because: First, in the direction away from the current collector, the content of structural material in the patterned layer first increases and then decreases, while the content of functional material first decreases and then increases. This can effectively suppress the impact of negative electrode expansion particle breakage on the battery, thereby further improving the cycle stability of the sodium-ion battery. Second, the binder content in the patterned layer near the current collector is higher, and the adhesion is enhanced, which effectively improves the peel strength of the coating on the electrode (4.8 N / cm in Example 1, while it drops to 3.8 N / cm in Example 12), thereby improving the electrode stability during the cycle.

[0109] (7) As can be seen from the comparison between Example 1 and Comparative Examples 1 to 5, the sodium-ion battery electrode provided in this application includes at least two patterned layers stacked together, and the multiple patterned sub-coatings in each patterned layer are independent of each other and not connected to each other, which has the following beneficial effects: First, the multi-layer patterned design increases the effective loading area of ​​the active material while reducing the proportion of inactive interfaces, allowing more sodium ions to be stored per unit area, thereby improving the energy density. The energy density of Example 1 (274 Wh / kg) is significantly higher than that of Comparative Example 1 (253 Wh / kg), Comparative Example 2 (249 Wh / kg), and Comparative Example 3 (255 Wh / kg), representing increases of approximately 21 Wh / kg, 25 Wh / kg, and 19 Wh / kg, respectively.

[0110] Secondly, the layered patterned layers shorten the diffusion path of sodium ions and accelerate the electron transport rate, thereby improving the sodium ion insertion / extraction efficiency. The capacity retention rate of Example 1 (94.0%) was significantly better than that of Comparative Example 1 (86.5%), Comparative Example 2 (85.7%), and Comparative Example 3 (87.0%), by approximately 7.5%, 8.3%, and 7.0%, respectively.

[0111] Furthermore, the independent and unconnected patterned sub-coatings, arranged independently, reduce mutual influence between them, decrease stress concentration at the interface, enhance the adhesion between the coating and the current collector, and suppress material shedding due to volume changes during charging and discharging, thereby improving the structural stability of the electrode. The peel strength of Example 1 (4.8 N / cm) is significantly higher than that of Comparative Example 3.

[0112] Finally, the interlayer voids and the spaces formed by multiple patterned sub-coatings in each patterned layer can absorb the stress generated during sodium ion insertion / extraction, disperse the concentration effect of volume expansion, thereby reducing the risk of electrode cracking and extending the cycle life of sodium-ion batteries. Comparative Example 5 (hexagonal annular sub-coatings without gaps) showed low peel strength and low cycle capacity retention, further confirming the importance of independent, interstitial arrangement.

[0113] The above are merely optional embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An electrode for a sodium-ion battery, characterized in that, The electrode includes: Current collector; and Patterned stacks are disposed on at least one surface of the current collector; The patterned stack includes at least two patterned layers stacked along the thickness direction, and two adjacent patterned layers have a partially overlapping area or a completely overlapping area in the plane direction of the current collector. Each of the patterned layers includes a plurality of patterned sub-layers, and the plurality of patterned sub-layers located within the same patterned layer are independent of each other and are not connected to each other; Furthermore, the plurality of patterned sub-coatings located within the same patterned layer are discretely distributed or concentrically nested in the planar direction of the current collector.

2. The electrode sheet according to claim 1, characterized in that, The plurality of patterned sub-coatings located within the same patterned layer are discretely distributed in the planar direction of the current collector, and the plurality of patterned sub-coatings in at least one patterned layer are annular sub-coatings; each annular sub-coating has an internal hollow region enclosed by its inner boundary, the internal hollow region being an uncoated region for depositing sodium metal; and the gaps between adjacent annular sub-coatings are also uncoated regions for depositing sodium metal.

3. The electrode sheet according to claim 2, characterized in that, Each of the aforementioned annular sub-coatings has a ring width of 0.5~200μm and a thickness of 2~30μm; Furthermore, the edge gap between adjacent annular sub-coatings located within the same patterned layer is 1~200μm.

4. The electrode sheet according to claim 2 or 3, characterized in that, The shape of each of the said annular sub-coatings is selected from at least one of circular rings, elliptical rings, triangular rings, quadrilateral rings, pentagonal rings, or hexagonal rings; Furthermore, the equivalent circle diameter of the inner hollow region of each of the annular sub-coatings is 0.5~50μm; wherein, the equivalent circle diameter refers to the diameter of a circle with the same area as the inner hollow region.

5. The electrode sheet according to claim 4, characterized in that, At least one of the patterned layers includes at least two hexagonal ring sub-coatings, and any two hexagonal ring sub-coatings are not nested.

6. The electrode sheet according to claim 1, characterized in that, The plurality of patterned sub-coatings located within the same patterned layer are concentrically nested in the planar direction of the current collector, and at least one of the patterned layers includes at least two concentric annular sub-coatings. The radial spacing between adjacent annular sub-coatings is 1~200μm, and the ring width of each annular sub-coating is 0.5~200μm, and the thickness is 2~30μm.

7. The electrode sheet according to claim 6, characterized in that, The shape of each of the said annular sub-coatings is selected from at least one of a circular ring, an elliptical ring, a triangular ring, a quadrilateral ring, a pentagonal ring, or a hexagonal ring.

8. The electrode sheet according to claim 7, characterized in that, Each of the patterned layers includes at least two concentric annular sub-coatings.

9. The electrode sheet according to claim 1, characterized in that, The thickness of the patterned stack is 20~100μm.

10. The electrode sheet according to claim 1, characterized in that, In each of the patterned layers, the blank area ratio is 20% to 70%; wherein, the blank area ratio refers to the proportion of the area of ​​the region not covered by the patterned sub-coating layer to the total area of ​​the single side of the current collector within the same patterned layer.

11. The electrode sheet according to claim 1, characterized in that, Each of the patterned layers comprises structural materials and functional materials; The structural material is selected from at least one of covalent organic framework materials, metal-organic framework materials, metal oxides, metal fluorides, hard carbon, silicon oxide, or silicon carbon; The functional material includes a conductive agent and a binder; The conductive agent is selected from at least one of conductive graphite, carbon black, carbon nanotubes, or graphene. The adhesive is selected from at least one of polyvinylidene fluoride, polyacrylic acid, polyvinyl alcohol, polyimide, polytetrafluoroethylene, sodium carboxymethyl cellulose, or styrene-butadiene rubber.

12. The electrode sheet according to claim 11, characterized in that, The patterned stack includes 2 to 50 patterned layers; When the patterned stack comprises at least three patterned layers, along the direction away from the current collector: at least one of the following parameters in each patterned layer of the patterned stack varies with a gradient: The blank area ratio in each patterned layer first decreases and then increases layer by layer. The content of structural material in each patterned layer increases layer by layer and then decreases layer by layer. The content of functional materials in each patterned layer decreases layer by layer and then increases layer by layer.

13. The electrode sheet according to claim 12, characterized in that, The absolute difference between any two adjacent patterns in the blank area ratio of each patterned layer is 5% to 10%. And / or, the absolute difference between any two adjacent layers in the content of structural material in each patterned layer is 5% to 10%; And / or, the absolute difference between any two adjacent layers in the content of functional materials in each patterned layer is 5% to 10%.

14. A method for preparing the electrode sheet according to any one of claims 1 to 13, characterized in that, Includes the following steps: At least two patterned layers are formed layer by layer on at least one surface of the current collector using a patterned deposition process. In forming each patterned layer, multiple independent and unconnected patterned sub-coatings are deposited on the surface of the current collector or on the already formed patterned layer, and the multiple patterned sub-coatings in the same patterned layer are discretely distributed or concentrically nested. Furthermore, when forming two adjacent patterned layers, the patterned layer of the latter layer partially or completely overlaps with the patterned layer of the former layer in the plane direction of the current collector.

15. The preparation method according to claim 14, characterized in that, The deposition method includes 3D printing.

16. A sodium-ion battery, characterized in that, The sodium-ion battery includes the electrode as described in any one of claims 1 to 13.

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