Negative electrode-free sodium-ion battery, its current collector and preparation method

Abstract

This application relates to the field of battery technology, and particularly to a negative electrode-free sodium-ion battery, its current collector, and its preparation method. The current collector includes a current collector body and a porous compound modification layer located on at least one side surface of the current collector body. The porous compound modification layer includes multiple pore structures of mesopore size, and the exposed surface of the porous compound modification layer has sodium-affinity sites. The surface of the pore structure serves as an interface for sodium ion deposition and stripping. This application can significantly improve the electrical performance of the negative electrode-free sodium-ion battery.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a negative electrode-free sodium-ion battery, its current collector, and its preparation method. Background Technology

[0002] Currently, lithium-ion batteries dominate the energy storage and power battery markets, but the ever-increasing demand for large-scale energy storage remains unmet due to the scarcity of lithium resources and cost fluctuations. Sodium-ion batteries, with their abundant sodium resources, low cost, and excellent low-temperature performance, have become the most promising alternative to lithium-ion batteries among many rechargeable secondary battery systems; however, their low energy density hinders their industrialization. Electrodeless sodium-ion battery technology, by eliminating traditional anode materials and directly utilizing current collectors as ion carriers to achieve sodium ion deposition / stripping, significantly improves energy density and further reduces the manufacturing cost of sodium-ion batteries, demonstrating enormous application potential. However, interface instability and short cycle life caused by sodium dendrite growth on the current collector remain key issues that urgently need to be addressed for the commercialization of electrodeless sodium-ion batteries. Summary of the Invention To address at least one of the problems of the prior art, this application provides a negative electrode-free sodium-ion battery, its current collector, and a preparation method thereof, to reduce the impact of sodium dendrite growth and improve cycle life. The specific technical solution is as follows: On the one hand, this application provides a current collector for a negative electrode-free sodium-ion battery, comprising a current collector body and a porous compound modification layer located on at least one side surface of the current collector body; The porous compound-modified layer comprises multiple mesopore-sized pore structures, the exposed surface of the porous compound-modified layer has sodium-loving sites, and the surface of the pore structures serves as an interface for sodium ion deposition and stripping.

[0003] In an exemplary embodiment, the sodium-loving site includes one or more of the following: sodium-loving functional groups, unsaturated coordination sites, metal nanoparticles, or sodium-loving intermediates.

[0004] In an exemplary embodiment, the sodium-loving functional group includes a hydroxyl group.

[0005] In an exemplary embodiment, the metal nanoparticles include at least one of iron, cobalt, or molybdenum; In an exemplary embodiment, the sodium-loving intermediate includes at least one of a carbon-based compound, a sodium-tin alloy intermediate, a sodium-bismuth alloy intermediate, a sodium-antimony alloy intermediate, a sodium-germanium alloy intermediate, a sodium phosphide intermediate, or a sodium sulfide intermediate.

[0006] In an exemplary embodiment, at least a portion of the pore structure of the porous compound-modified layer is an interconnected three-dimensional mesoporous channel.

[0007] In an exemplary embodiment, the current collector body is at least one of an aluminum-based current collector body or a copper current collector body.

[0008] In an exemplary embodiment, the material of the porous compound modification layer includes one or more of mesoporous carbon, mesoporous metal compounds, mesoporous sulfides, or mesoporous selenium compounds.

[0009] In an exemplary embodiment, the thickness of the porous compound modification layer is 5 nm-5 μm.

[0010] In an exemplary embodiment, the pore size of the pore structure is 2nm-500nm.

[0011] In an exemplary embodiment, the thickness of the porous compound modification layer is 5 nm-500 nm; In an exemplary embodiment, the pore size of the pore structure is 2-200 nm.

[0012] In an exemplary embodiment, the material of the porous compound modification layer includes one or more of the following: mesoporous carbon, mesoporous aluminum compound, mesoporous zinc compound, mesoporous tin compound, mesoporous iron compound, mesoporous cobalt compound, mesoporous titanium compound, mesoporous antimony compound, mesoporous bismuth compound, mesoporous germanium compound, mesoporous phosphorus compound, mesoporous molybdenum compound, mesoporous molybdenum sulfide, mesoporous tin sulfide, mesoporous selenium molybdenum compound, or mesoporous selenium oxide.

[0013] In an exemplary embodiment, the material of the porous compound modification layer includes one or more of mesoporous carbon, mesoporous aluminum oxide, mesoporous titanium oxide, mesoporous iron oxide, mesoporous cobalt oxide, mesoporous selenium oxide, mesoporous tin oxide, mesoporous zinc oxide, mesoporous tin sulfide, mesoporous selenium molybdenum sulfide, or mesoporous molybdenum sulfide.

[0014] In an exemplary embodiment, the material of the porous compound modification layer includes one or more of C, Al2O3, TiO2, ZnO, SnO2, Fe2O3, Co3O4, MoO3, SeO2, MoS2, SnS2, or MoSe2.

[0015] In an exemplary embodiment, the thickness of the porous compound modification layer is 5-20 nm.

[0016] In an exemplary embodiment, the pore size of the pore structure is 2-30 nm.

[0017] In an exemplary embodiment, the current collector further includes a dense bonding layer located between the surface of the current collector body and the porous compound modification layer.

[0018] In an exemplary embodiment, the thickness of the dense bonding layer is 0.5 nm-5 μm.

[0019] In an exemplary embodiment, the thickness of the dense bonding layer is 0.5 nm to 500 nm.

[0020] In an exemplary embodiment, the thickness of the dense bonding layer is 0.5 nm-3 nm. On the other hand, this application provides a method for preparing a current collector for a negative electrode-free sodium-ion battery, the method comprising: Provide the current collector body; A porous compound modification layer is formed on at least one side surface of the current collector body. The porous compound modification layer includes a plurality of mesopore-sized pore structures. The exposed surface of the porous compound modification layer has sodium-loving sites. The surface of the pore structures serves as an interface for sodium ion deposition and stripping.

[0021] In an exemplary embodiment, the preparation method further includes: A dense bonding layer is formed between the current collector body and the porous compound modification layer; The thickness of the dense bonding layer is 0.5 nm to 5 μm.

[0022] In an exemplary embodiment, forming a porous compound modification layer on at least one surface of the current collector body includes: A template layer is formed on at least one surface of the current collector body to obtain a composite, wherein the template layer has voids; The composite is subjected to vapor deposition to form a compound modification layer that fills the template layer; The template layer is removed to form the porous compound modified layer.

[0023] In an exemplary embodiment, before forming the template layer, the preparation method further includes: The current collector body is subjected to surface activation treatment, and the template layer is located on at least one side of the activated surface of the current collector body; A dense bonding layer is formed on the activated surface during the initial stage of the vapor deposition process.

[0024] In an exemplary embodiment, the template layer is a soft template formed by immersing the current collector body in a template solution and then self-assembling the template material on the surface of the current collector body.

[0025] In an exemplary embodiment, the template solution further includes a micelle expander, which is used to increase the micelle size in the template layer.

[0026] In an exemplary embodiment, removing the template layer to form the porous compound modification layer includes: In an inert gas environment, the composite having the compound-modified layer is heat-treated to decompose and / or volatilize the template layer, forming the porous structure, and then cooled to obtain the porous compound-modified layer.

[0027] On the other hand, this application provides a sodium-ion battery, including the current collector for a negative electrode-free sodium-ion battery as described above.

[0028] In an exemplary embodiment, the electrolyte of the sodium-ion battery includes an ether solvent and a sodium salt.

[0029] In an exemplary embodiment, the ether solvent includes at least one of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.

[0030] In an exemplary embodiment, the sodium salt includes one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium bis(trifluoromethanesulfonyl)imide, sodium di(fluorooxalateborate), and sodium di(fluorosulfonyl)imide.

[0031] In an exemplary embodiment, the electrolyte further includes at least one of a film-forming additive and a sodium-replenishing additive.

[0032] In an exemplary embodiment, the film-forming additive includes one or more of the following: fluoroethylene carbonate, vinylene carbonate, 1,3-propane sulpholactone, vinyl sulfate, and bicyclic sulfate compounds.

[0033] In an exemplary embodiment, the sodium supplement includes at least one of sodium trimethylsilanolate and sodium amino acid.

[0034] In an exemplary embodiment, the mass percentage of the film-forming additive in the electrolyte is 1-5%.

[0035] In an exemplary embodiment, the concentration of the sodium salt in the electrolyte is 0.8-2.0 mol / L.

[0036] In an exemplary embodiment, the concentration of the sodium supplement in the electrolyte is 0.1-0.5 mol / L.

[0037] Based on the above technical solution, this application has the following beneficial effects: In the current collector of this application, a porous compound modification layer is constructed on at least one side surface of the current collector body. This porous compound layer has a pore structure with multiple mesopore sizes and exposes sodium-loving sites to replace the interface for sodium ion deposition and stripping during battery cycling, thus replacing the negative electrode. This mesopore structure has a high specific surface area, providing a rapid diffusion path for sodium ion transport and effectively buffering the volume change stress generated by repeated deposition / stripping of metallic sodium, maintaining the mechanical integrity of the electrode structure. Furthermore, the porous compound modification layer is located between the electrolyte and the current collector body, which can effectively reduce the direct contact between the electrolyte and the current collector body, suppress side reactions, and prevent electrolyte decomposition products from corroding the current collector body interface, thereby significantly improving the long-term stability of the electrode / electrolyte interface. Simultaneously, the current collector of this application can utilize the synergistic effect of sodium-loving site-induced nucleation, mesopore confined growth, and interface stabilization to improve the interface side reactions of negative electrode-free current collectors, achieving uniform sodium metal deposition and avoiding sodium dendrite growth, further improving the safety and cycle life of negative electrode-free sodium batteries. Attached Figure Description

[0038] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0039] Figure 1 This is a schematic cross-sectional view of the current collector prepared in Example 1; Figure 2 The example and comparative examples are shown in the first-round coulomb efficiency comparison chart. Figure 3 This is a comparison chart of the 0.1C cycle performance of the example and the comparative example; 1-Current collector body, 2-Dense bonding layer, 3-Porous compound modification layer, 4-Porous structure. Detailed Implementation

[0040] 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 some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0041] For the terms defined below, unless a different definition is given elsewhere in the claims or this specification, these definitions shall apply. All numerical values, whether explicitly indicated or not, are defined herein as being modified by the term "about." The term "about" generally refers to a range of numerical values ​​that a person skilled in the art would consider equivalent to the stated values ​​to produce substantially the same properties, functions, results, etc. A range of numerical values ​​indicated by a low value and a high value is defined as including all numerical values ​​included within that range and all subranges included within that range.

[0042] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application 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. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion.

[0043] The following describes a current collector for a negative electrode-free sodium-ion battery provided by embodiments of this application. The current collector includes a current collector body 1 and a porous compound modification layer 3 located on at least one side surface of the current collector body 1. The porous compound modification layer 3 includes multiple pore structures 4 of mesopore size. The exposed surface of the porous compound modification layer 3 has sodium-affinity sites, and the surface of the pore structure 4 serves as an interface for sodium ion deposition and stripping.

[0044] Specifically, a porous compound modification layer 3 can be formed on both sides of the current collector body 1, or a porous compound modification layer 3 can be formed on the side surface of the current collector body 1 used for encapsulating the electrolyte.

[0045] In possible implementations, the current collector body 1 is at least one of an aluminum-based current collector body 1 or a copper current collector body 1, such as aluminum foil or copper foil. Preferably, the current collector body 1 is an aluminum-based current collector body 1. The porous compound modification layer 3 of this application embodiment can be adapted to conventionally used aluminum-based current collector bodies 1 or copper current collector bodies 1, and can meet various configuration requirements for the industrialization of sodium batteries.

[0046] In a possible implementation, the porous compound modification layer 3 is formed on the current collector body 1 through a deposition process, achieving a dense connection between the two, thereby reducing the risk of layer structure detachment and breakage, and improving battery stability. Exemplarily, the above deposition process includes, but is not limited to, one or more of atomic layer deposition (ALD) or chemical vapor deposition (CVD).

[0047] In a possible implementation, at least one end of a portion of the porous compound modification layer 3 is open and exposed on the surface of the porous compound modification layer 3 facing away from the current collector body 1, thereby allowing its pore walls (i.e., the surface of the pore structure 4) to contact the electrolyte, achieving induced nucleation of sodium ions. This means that the porous structure 4 constructs an excellent physical barrier, directly blocking the growth path of sodium dendrites, forcing sodium atoms to deposit uniformly within the pores rather than penetrating vertically, resulting in uniform sodium deposition. Abundant mesoporous channels provide a rapid diffusion path for sodium ions, reducing ion transport resistance and improving rate performance.

[0048] In a possible implementation, the sodium-loving sites are located on the exposed surface of the porous compound modification layer 3, especially on the surface of the pore structure 4, which can reduce the sodium nucleation barrier and guide sodium atoms to preferentially nucleate uniformly in the pores and on the surface, rather than randomly growing to form dendrites. At the same time, the confinement effect of the pore structure 4 can limit the formation of sodium dendrites in the pores and instead tend to deposit uniformly along the pore walls.

[0049] In summary, in the current collector of this application embodiment, a porous compound modification layer 3 is constructed on at least one side surface of the current collector body 1. This porous compound layer has multiple mesopore structures 4 with mesopore sizes and exposes sodium-loving sites to replace the interface for sodium ion deposition and stripping during battery cycling, thus replacing the negative electrode. This mesopore structure has a high specific surface area, providing a rapid diffusion path for sodium ion transport and effectively buffering the volume change stress generated by repeated deposition / stripping of metallic sodium, maintaining the mechanical integrity of the electrode structure. Furthermore, the porous compound modification layer 3 is located between the electrolyte and the current collector body 1, which can effectively reduce the direct contact between the electrolyte and the current collector body 1, suppress side reactions, and prevent electrolyte decomposition products from corroding the interface of the current collector body 1, thereby significantly improving the long-term stability of the electrode / electrolyte interface. At the same time, the current collector of this application can utilize the multiple synergistic effects of sodium-loving site-induced nucleation, mesopore confined growth, and interface stabilization to improve the interface side reactions of the negative electrode-free current collector, achieve uniform sodium metal deposition, and avoid the growth of sodium dendrites, further improving the safety and cycle life of the negative electrode-free sodium battery.

[0050] In some embodiments, the thickness of the porous compound modification layer 3 is 5 nm-5 μm; in a preferred embodiment, the thickness of the porous compound modification layer is 5 nm-1 μm. In a preferred embodiment, the thickness of the porous compound modification layer is 5 nm-500 nm. In a preferred embodiment, the thickness of the porous compound modification layer is 5 nm-100 nm. In a preferred embodiment, the thickness of the porous compound modification layer 3 is 5-20 nm. Exemplarily, the upper limit of the thickness of the porous compound modification layer 3 can be 5 μm, 4.5 μm, 4 μm, 3.5 μm, 3 μm, 2.5 μm, 2 μm, 1.5 μm, 1 μm, etc., or it can be approximately 30 nm, 25 nm, 20 nm, 18 nm, 15 nm, etc., and the lower limit of the thickness can be approximately 5 nm, 7 nm, 9 nm, etc. It is understood that the thickness of the porous compound modification layer 3 can be any value within the above thickness range, and is not limited to the above examples. By forming a porous compound modification layer 3 of the aforementioned thickness, sufficient sodium deposition sites and space are provided to ensure battery capacity and performance, while avoiding sodium stripping difficulties caused by excessively thick material layers, thus reducing sodium loss, battery cost, and weight.

[0051] In some embodiments, the pore size of the pore structure 4 is 2nm-500nm. In a preferred embodiment, the pore size of the pore structure 4 is 2-200nm. In a preferred embodiment, the pore size of the pore structure 4 is 2-100nm. In a preferred embodiment, the pore size of the pore structure 4 is 2-30nm. Exemplarily, the upper limit of the pore size of the pore structure 4 can be approximately or equal to 500nm, 450nm, 400nm, 50nm, 300nm, 250nm, 200nm, 150nm, 100nm, 90nm, 80nm, 70nm, 60nm, 50nm, 40nm, 35nm, 30nm, 28nm, 25nm, etc., and the lower limit of the pore size can be approximately or equal to 2nm, 3nm, 4nm, 5nm, etc. It is understood that the pore size of the pore structure 4 can be any value within the above-mentioned pore size range, and is not limited to the above examples. Thus, the high specific surface area of ​​the mesoporous structure effectively disperses the volume expansion stress during sodium deposition, and the porous network buffers the expansion pressure by reserving space, avoiding the problem of damage caused by local stress concentration in traditional oxide modification layers, resulting in higher structural stability. Furthermore, the high specific surface area of ​​the porous structure 4 provides a rapid diffusion path for sodium ion transport, while avoiding sodium dendrite growth due to excessively large pore sizes and loss of active sodium due to excessively small pore sizes. Combined with the thickness setting of the porous compound modification layer 3, excellent anode-like performance can be achieved, significantly improving the cycle life and capacity of the battery.

[0052] In some embodiments, the current collector further includes a dense bonding layer 2, which is located between the surface of the current collector body 1 and the porous compound modification layer 3.

[0053] Specifically, the dense structural layer is located on the surface of the current collector body 1 and is formed in the initial stage of deposition. It can be tightly bonded to the current collector body 1 and provides excellent adhesion, so that the porous compound modification layer 3 is firmly bonded to the current collector and plays a structural support role.

[0054] In some embodiments, the dense structural layer may be formed on the surface of the current collector body 1 after surface activation, and surface activation may be achieved by acid etching.

[0055] In some embodiments, the thickness of the dense bonding layer 2 is 0.5 nm-5 μm. In a preferred embodiment, the thickness of the dense bonding layer is 0.5 nm-500 nm. In a preferred embodiment, the thickness of the dense bonding layer is 0.5 nm-200 nm. In a preferred embodiment, the thickness of the dense bonding layer is 0.5 nm-50 nm. In a preferred embodiment, the thickness of the dense bonding layer is 0.5 nm-3 nm. In a preferred embodiment, the thickness of the dense bonding layer 2 is 0.5-2 nm. For example, the lower limit of the thickness of the dense bonding layer 2 can be approximately or 0.5 nm, 0.6 nm, 0.7 nm, etc., and the upper limit of the thickness of the dense bonding layer 2 can be approximately or 5 μm, 4.5 μm, 4 μm, 3.5 μm, 3 μm, 2.5 μm, 2 μm, 1.5 μm, 1 μm, 500 nm, 400 nm, 300 nm, 200 nm, 100 nm, 50 nm, 30 nm, 10 nm, 3 nm, 2 nm, 1.8 nm, 1.6 nm, 1.4 nm, etc. It can be understood that the thickness of the dense bonding layer 2 can be any value within the above thickness range, and is not limited to the above examples.

[0056] It should be noted that the thickness of the material layer may vary slightly at different locations, or the thickness of the deposited material may differ slightly from the predetermined value. Accordingly, the upper limit of the thickness may slightly exceed the upper limit of the aforementioned range, or the lower limit of the thickness may slightly exceed the lower limit of the aforementioned range. Similarly, the dimensions of the pore structure 4 may vary slightly at different locations, or the pore diameters of the pore structures 4 may not be consistent with each other. Accordingly, the upper limit of the pore diameter may slightly exceed the upper limit of the aforementioned range, and the lower limit of the pore diameter thickness may slightly exceed the lower limit of the aforementioned range. The aforementioned cases of slightly exceeding the boundary limits all apply to the scope limitation of this application. That is, the boundary values ​​of each range involved in this application are not absolutely limited values, but rather values ​​that meet the error range. For example, each boundary value within ±1nm can be within the protection scope of this application.

[0057] In a possible implementation, the porous compound modification layer 3 is a barrier layer that is chemically inert or moderately active to the electrolyte, which can isolate or at least partially isolate the current collector body 1 from direct contact with the electrolyte. Through this physical barrier, direct contact between the electrolyte and the aluminum current collector can be effectively blocked, side reactions can be suppressed, and electrolyte decomposition products can be prevented from corroding the current collector surface interface. This avoids battery failure problems such as interface deterioration and electrolyte consumption, thereby significantly improving the long-term stability of the electrode / electrolyte interface.

[0058] In some embodiments, at least a portion of the pore structure 4 of the porous compound modification layer 3 consists of interconnected three-dimensional mesoporous channels, forming a three-dimensional network structure. This abundant three-dimensional interconnected pore structure 4 effectively buffers the volumetric stress generated during repeated deposition / stripping of metallic sodium, maintaining the mechanical integrity of the electrode structure. Furthermore, the mesoporous structure resembles a labyrinthine channel; when sodium is deposited into the pores of the modification layer, the pore walls act as mechanical barriers, forcing sodium atoms to deposit uniformly within the pores rather than penetrating longitudinally, thus blocking the growth path of sodium dendrites.

[0059] In some embodiments, the pore structure 4 is uniformly distributed in the porous compound modification layer 3, thereby controlling the sodium ion flux to tend to be uniform on the surface of the current collector, eliminating local high current density areas, inducing smooth sodium deposition, avoiding the formation of dendrite nucleation sites, and effectively inhibiting sodium dendrite growth.

[0060] In some embodiments, the sodium-loving site includes one or more of the following: sodium-loving functional groups, unsaturated coordination sites, metal nanoparticles, or sodium-loving intermediates, such as unsaturated coordination sites in selenides.

[0061] In some embodiments, the sodium-loving functional group includes hydroxyl groups, such as hydroxyl groups on the surface of the oxide-modified layer. In some embodiments, the metal nanoparticles may include, but are not limited to, at least one of iron, cobalt, or molybdenum. It should be noted that the aforementioned metal nanoparticles may be formed through chemical modification, such as impregnation with a metal nanoparticle solution, or the metal nanoparticles may be generated in situ during the initial discharge of a porous compound-modified layer. For example, when Fe2O3, Co3O4, MoO3, etc., are used as the modifier layer, the Fe, Co, and Mo metal nanoparticles generated during the initial discharge can serve as sodium-loving sites for subsequent sodium deposition.

[0062] In some embodiments, the sodium-loving intermediate includes at least one of the following: a carbon-based compound, a sodium-tin alloy intermediate, a sodium-bismuth alloy intermediate, a sodium-antimony alloy intermediate, a sodium-germanium alloy intermediate, a sodium phosphide intermediate, or a sodium sulfide intermediate, such as a sodium-tin alloy intermediate or a sodium sulfide intermediate.

[0063] It should be noted that the sodium-loving sites in the embodiments of this application may also be other structures or substances that can reduce sodium nucleation oversites, and are not limited to the above examples, and will not be enumerated here.

[0064] By forming a porous compound modification layer 3 with sodium-loving sites on its surface, a uniform electron cloud distribution is achieved, which effectively reduces the nucleation overpotential of sodium. This guides metallic sodium to preferentially nucleate uniformly within and on the surface of the mesoporous pores, rather than randomly growing into dendrites. This synergistic effect of "sodium-loving site-induced nucleation" and "mesoporous confined growth" enables uniform deposition of sodium metal, thereby significantly inhibiting dendrite growth.

[0065] In some embodiments, the material of the porous compound modification layer 3 includes one or more of mesoporous carbon, mesoporous metal compounds, mesoporous sulfides, or mesoporous selenium compounds.

[0066] In a preferred embodiment, the material of the porous compound modification layer 3 includes one or more of the following: mesoporous carbon, mesoporous aluminum compound, mesoporous zinc compound, mesoporous tin compound, mesoporous iron compound, mesoporous cobalt compound, mesoporous titanium compound, mesoporous antimony compound, mesoporous bismuth compound, mesoporous germanium compound, mesoporous phosphorus compound, mesoporous molybdenum compound, mesoporous molybdenum sulfide, mesoporous tin sulfide, mesoporous selenium molybdenum compound, or mesoporous selenium oxide. The mesoporous aluminum compound can be mesoporous aluminum oxide, the mesoporous zinc compound can be mesoporous zinc oxide, the mesoporous tin compound can be mesoporous tin oxide, and the mesoporous molybdenum compound can be mesoporous molybdenum oxide.

[0067] In a preferred embodiment, the material of the porous compound modification layer includes one or more of the following: mesoporous carbon, mesoporous aluminum oxide, mesoporous titanium oxide, mesoporous iron oxide, mesoporous cobalt oxide, mesoporous selenium oxide, mesoporous tin oxide, mesoporous zinc oxide, mesoporous tin sulfide, mesoporous selenium molybdenum sulfide, or mesoporous molybdenum sulfide.

[0068] In one embodiment, the material of the porous compound modification layer 3 includes, but is not limited to, one or more of C, Al2O3, TiO2, ZnO, SnO2, Fe2O3, Co3O4, MoO3, SeO2, MoS2, SnS2 or MoSe2.

[0069] It should be noted that the porous compound modification layer 3 in the embodiments of this application can also be formed using other materials with moderate sodium affinity and good interfacial stability, and is not limited to the above examples, and will not be enumerated here.

[0070] By forming a mesoporous layer of the aforementioned material, chemical inertness can be ensured while forming a large number of sodium-loving sites to replace the negative electrode capability.

[0071] In some embodiments, the porous compound modification layer 3 can be formed by a template method and a deposition process. First, a template layer is formed, and then the modification layer material is filled by a deposition process. After the template layer is removed, the porous structure 4 is left, forming the porous compound modification layer 3.

[0072] Specifically, a template layer can be formed on the current collector body. This template layer includes arranged micelle structures, such as ordered micelle structures. The micelle structures are solid structures with gaps between them. Through a deposition process, precursor molecules preferentially enter and fill the gaps between the micelle structures, depositing to form a compound framework. Finally, the template layer is removed by heat treatment. The positions originally occupied by the micelle structures are transformed into three-dimensional interconnected mesoporous structures 4, while the deposited compound framework constitutes a porous compound modification layer 3. Exemplarily, the template layer can be formed by the self-assembly of an amphiphilic block copolymer or by other mechanisms forming a soft template structure.

[0073] In summary, the embodiments of this application, by setting a mesoporous porous compound modification layer 3 on the current collector, combine the multiple synergistic effects of physical confinement of the mesoporous structure, sodium-loving site-induced nucleation and interface stabilization, effectively improve the interfacial side reactions of the negative electrode-free current collector, promote the rapid diffusion of sodium ions, and effectively regulate sodium deposition behavior, thereby significantly extending the cycle life of the negative electrode-free sodium-ion battery.

[0074] This application also provides a method for preparing a current collector for a negative electrode-free sodium-ion battery, the preparation method including S1-S2: S1 provides the current collector body 1; S2, a porous compound modification layer 3 is formed on at least one side surface of the current collector body 1. The porous compound modification layer 3 includes a plurality of mesopore-sized pore structures 4. The exposed surface of the porous compound modification layer 3 has sodium-loving sites. The surface of the pore structure 4 is used as an interface for sodium ion deposition and stripping.

[0075] Specifically, the current collector body 1 can be a high-purity aluminum foil or copper foil, etc.

[0076] Specifically, the porous compound modification layer 3 can be formed by template method and deposition process, such as by soft template method and vapor phase deposition process.

[0077] In some embodiments, the preparation method further includes step S3: forming a dense bonding layer 2 between the current collector body 1 and the porous compound modification layer 3. Specifically, the thickness of the dense bonding layer 2 is 0.5 nm to 5 μm.

[0078] Specifically, the dense bonding layer 2 can be a material layer that naturally forms on the surface of the exposed current collector body 1 during the initial deposition stage, while the porous compound modification layer 3 is formed during the subsequent deposition process.

[0079] In a possible implementation, the interface between the porous compound-modified layer 3 and the densely bonded layer 2 is a natural transition.

[0080] In some implementations, S2 may include S21-S23: S21, a template layer is formed on at least one side surface of the current collector body 1 to obtain a composite, wherein the template layer has voids; S22, perform vapor deposition on the composite to form a compound modification layer that fills the template layer; S23, Remove the template layer to form a porous compound modification layer 3.

[0081] Specifically, the template layer can be formed on both sides of the current collector body 1, or it can be formed on one side of the surface. Vapor deposition can deposit the modification layer material on both sides of the composite, or it can deposit the modification layer material on one side of the composite.

[0082] Specifically, the template layer can be an ordered micelle template layer. For example, the template layer can be formed by the self-assembly of an amphiphilic block copolymer, forming a void region between the area occupied by the micelle structure entity and the micelle structure on the surface of the current collector.

[0083] Specifically, the composite is subjected to vapor deposition, which allows the compound precursor to be preferentially deposited in the void regions between the micelle structures to form a compound skeleton, which serves as the layer structure skeleton of the porous compound modification layer, thus obtaining the modified compound / template composite layer.

[0084] Understandably, a template layer is first formed, whose micelle structure serves as the site-occupying structure for the pore structure 4 in the porous compound modification layer. The void structure in the template layer serves as the skeleton template structure of the porous compound modification layer. After vapor deposition, the compound modification layer can be formed by filling the template layer with the compound precursor to serve as the layer structure skeleton. After heat treatment to remove the template layer, the pores formed by removing the micelle structure are the pore structure 4 of the porous compound modification layer 3, thereby forming a network-like porous compound modification layer with abundant three-dimensional channels.

[0085] In some embodiments, the template layer is a soft template formed by immersing the current collector body 1 in a template solution and then self-assembling the template material on the surface of the current collector body 1. In some embodiments, the soft template is a size-tunable ordered micelle structure. Through template self-assembly, a structurally ordered template layer can be formed, thereby controlling the structural order of the porous compound modification layer 3 and the uniformity of the pore structure 4 distribution, and optimizing the current collector performance.

[0086] In a preferred embodiment, the soft template is an organic template that can be thermally removed through heating decomposition and / or volatilization.

[0087] In a possible implementation, the template material is an amphiphilic template agent, which may include at least one of block copolymers or ionic surfactants, such as block copolymer P123, block copolymer P105, block copolymer F127, hexadecyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), etc.

[0088] It should be noted that the template material used in the embodiments of this application may also be other template agents capable of self-assembling to form a template layer, and is not limited to the examples mentioned above.

[0089] In some embodiments, the template solution further includes a micelle expander, which is used to increase the micelle size in the template layer. The concentration of the micelle expander in the template solution can affect the size of the micelles in the template layer, thereby controlling the size and distribution of the subsequent pore structure 4.

[0090] For example, the micelle expander may be, but is not limited to, at least one of 1,3,5-trimethylbenzene (TMB), 1,3,5-triethylbenzene (TEB), 1,3,5-triisopropylbenzene (TIPB), n-hexane, or polyethylene glycol (PEG). It is understood that the micelle expander may be adapted for use with a template agent and may also be other expanders capable of affecting micelle size, not limited to the examples described above.

[0091] In one embodiment, without adding a micelle expander, a micelle structure of about 2 nm or about 3 nm-4 nm can be formed in the template layer by using an appropriate concentration of template agent and self-assembly reaction parameters, thereby forming a pore structure 4 of about 2 nm or about 3 nm-4 nm. By adding a micelle expander, the micelle size can be increased to about 30 nm or about 40 nm, thereby forming a pore structure 4 of the corresponding size.

[0092] In some embodiments, prior to S21, the preparation method further includes: surface activation treatment of the current collector body 1, with the template layer located on at least one side of the activated surface of the current collector body 1. Specifically, surface activation is used to remove inert substances or impurities from the surface of the current collector body 1 to increase its bonding force with the dense bonding layer 2 and / or the porous compound modification layer 3, thereby improving structural stability. For example, surface activation can clean and activate the surface of the original aluminum current collector body 1, removing the natural alumina layer.

[0093] In one embodiment, the surface activation treatment can be an acid etching treatment, the acid etching temperature can be room temperature, and the treatment time can be 10-20 seconds.

[0094] In some embodiments, the dense bonding layer 2 is formed on the activated surface during the initial stage of the vapor deposition process. The activated surface has a certain roughness, such as micropores, thereby increasing the bonding strength.

[0095] In one embodiment, the vapor deposition process is atomic layer deposition, and the deposited modification layer material can be, but is not limited to, trimethylaluminum (TMA) precursor, etc. The hydroxyl groups exposed on the acid-etched activated aluminum surface react with the trimethylaluminum (TMA) precursor to form a continuous and dense alumina layer, which serves as the dense bonding layer 2. This structural layer is the initial deposition layer that spontaneously grows on the clean aluminum surface after acid etching, and plays a structural support role.

[0096] In some embodiments, S23 may include: heat-treating the composite with the compound-modified layer in an inert gas environment to decompose and / or volatilize the template layer, forming a porous structure 4, and then cooling to obtain a porous compound-modified layer 3. Heat treatment can simultaneously remove the template layer and achieve stable shaping of the porous compound-modified layer 3, avoiding layer structure cracking due to thermal stress or excessive oxidation of the current collector body 1.

[0097] Understandably, the heating temperature of the heat treatment is determined based on the decomposition temperature or volatilization temperature of the template layer. For example, the heating temperature of the P123 template layer can be 400-450°C, and the heating time can be 1-2 hours.

[0098] In some embodiments, heat treatment is performed by programmed heating to remove the template layer.

[0099] In some embodiments, the heat-treated sample is immersed in a cleaning solution for static soaking to remove any trace amounts of template decomposition products that may be attached. After soaking, it is dried in an oxygen-free environment and then stored in an oxygen-free environment.

[0100] In some embodiments, the concentration of the template agent in the template solution can be 0.02-0.06 g / mL.

[0101] In some embodiments, during the self-assembly process of the porous template, the current collector body 1 is left to stand in the template solution for 10-30 minutes.

[0102] In some embodiments, a pore structure with the desired pore size is formed by adjusting one or more of the following synthesis conditions: template agent concentration, micelle expansion agent concentration, template solution pH, template removal heat treatment time, and vapor deposition temperature.

[0103] This application also provides a negative electrode-free sodium-ion battery, including the aforementioned current collector for a negative electrode-free sodium-ion battery. The sodium-ion battery of this application embodiment possesses all the advantages offered by the current collector for a negative electrode-free sodium-ion battery of this application embodiment, which will not be elaborated further here.

[0104] In some embodiments, the electrolyte of the sodium-ion battery includes an ether solvent and a sodium salt; the ether solvent includes at least one of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.

[0105] In some embodiments, the sodium salt includes one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium bis(trifluoromethanesulfonyl)imide, sodium di(fluorooxalateborate), and sodium di(fluorosulfonyl)imide.

[0106] In some embodiments, the electrolyte further includes at least one of a film-forming additive and a sodium-replenishing additive.

[0107] In some embodiments, the film-forming additive includes one or more of fluoroethylene carbonate, vinylene carbonate, 1,3-propane sulpholactone, vinyl sulfate, and bicyclic sulfate compounds.

[0108] In some embodiments, the sodium supplement includes at least one of sodium trimethylsilanolate and sodium amino acid.

[0109] It is understood that the ether solvents, sodium salts, film-forming additives and sodium supplementation additives used in the embodiments of this application may also be other materials that can realize a negative electrode-free sodium-ion battery, and are not limited to the examples above.

[0110] In some implementations, the mass percentage of film-forming additives in the electrolyte is 1-5%.

[0111] In some implementations, the concentration of sodium salt in the electrolyte is 0.8-2.0 mol / L.

[0112] In some implementations, the concentration of sodium supplementation additive in the electrolyte is 0.1-0.5 mol / L.

[0113] In possible implementations, the positive electrode material of the negative electrode-free sodium-ion battery can be any of the existing positive electrode material systems, such as polyanionic positive electrode materials with sodium ferric sulfate (NFS) as the active material, or NFPP (sodium ferric pyrophosphate / composite sodium ferric phosphate), etc., without specific limitations.

[0114] The following describes specific embodiments of this application in conjunction with the aforementioned negative electrode-free sodium-ion battery, its current collector, and its preparation method. The following embodiments describe the technical solutions of this application in more detail. These embodiments are for illustrative purposes only, as various modifications and variations within the scope of the disclosure of this application will be apparent to those skilled in the art. The reagents used in the embodiments are commercially available or synthesized using conventional methods and can be used directly without further processing. Similarly, the materials, instruments, and apparatus used in the embodiments are all commercially available.

[0115] Example 1: Preparation of current collector (1) Pretreatment and surface activation of aluminum-based current collector body 1: Commercial aluminum foil with a purity of 99.99% and a thickness of 20 μm was cut into 10 cm × 10 cm samples. The samples were immersed in 0.05 M hydrochloric acid solution and treated precisely for 20 seconds at room temperature, with slight agitation during treatment to ensure uniform corrosion. After treatment, the samples were immediately transferred to ultrapure water (18.2 MΩ·cm) and rinsed several times until the pH test paper showed neutrality.

[0116] Subsequently, the sample was transferred to an ultrasonic cleaner containing anhydrous ethanol for 3 minutes to remove residual impurities and inhibit oxidation. After removal, the surface liquid was immediately dried with a gentle stream of high-purity nitrogen and then quickly placed in a vacuum drying oven at 60°C and a vacuum degree ≤1 Pa for 4 hours. After drying, the sample was quickly transferred to an argon glove box with a water and oxygen content not exceeding 0.1 ppm for temporary storage.

[0117] (2) Preparation and loading of soft template solution: In an argon-filled glove box, weigh block copolymer P123 (Pluronic P123, MW≈5800), dissolve it in anhydrous ethanol, and prepare a template solution with a concentration of 0.02-0.04 g / mL. Place the solution on a magnetic stirrer and stir for 1-3 hours until P123 is completely dissolved and the template solution is clear and transparent.

[0118] The aluminum foil pretreated in step (1) was vertically immersed in the template solution and allowed to stand for 10-20 minutes to ensure that the P123 micelles were fully and orderly self-assembled on the aluminum surface. After adsorption, the aluminum foil composite was removed and the ethanol was allowed to evaporate naturally under an argon atmosphere in a glove box. After the surface was free of flowing droplets, the sample was transferred to a vacuum drying oven and dried at 40°C and a vacuum degree ≤1 Pa for 45 minutes, thereby fixing the ordered micelle structure onto the aluminum foil to form a template layer.

[0119] (3) Atomic layer deposition (ALD) preparation of compound-modified layers (alumina / template composite layers): Fix the aluminum foil sample loaded with the P123 template obtained in step (2) onto the sample tray of the ALD device (Savannah 100 model), and quickly close the reaction chamber. Evacuate the reaction chamber to stabilize the background pressure to 0.5 Torr (approximately 67 Pa).

[0120] The reaction chamber temperature was set to 200℃, and the precursor trimethylaluminum (TMA) pipeline temperature was set to 150℃, and maintained at this temperature for 30 minutes. During deposition, high-purity nitrogen (99.999% purity) was used as both the carrier gas and the purge gas, with the flow rate consistently controlled at 20 sccm. ALD circulating deposition was then performed.

[0121] A single ALD cycle sequence is as follows: Pulsing the trimethylaluminum (TMA, 99.999% purity) precursor into the reaction chamber; Nitrogen gas is introduced into the reaction chamber to purge and remove excess precursors and byproducts; Pulse deionized water (H2O) steam into the reaction chamber; Nitrogen gas was purged into the reaction chamber again.

[0122] The above cyclic sequence is repeated according to the number of cycles determined by the target thickness. Typically, the number of cycles is selected in the range of 30-200. This process first forms an extremely thin, dense alumina layer on the surface of the surface-activated aluminum foil as a dense bonding layer 2. Then, guided by the template layer, the trimethylaluminum precursor is deposited in the micelle gaps of the template layer, beginning the construction of the prototype of the porous compound modification layer 3 (mesoporous alumina functional layer), i.e., forming the compound modification layer.

[0123] (4) Template removal and mesoporous structure shaping: Remove the sample deposited in step (3) from the ALD device and immediately place it in the quartz boat of the temperature-controlled tube furnace. Purge the furnace tube with high-purity nitrogen (flow rate 50 sccm) for 30 minutes to completely remove air.

[0124] Subsequently, under a nitrogen atmosphere, heat treatment was performed according to a preset procedure: the temperature was increased from room temperature to 420°C at a rate of 3°C / min; it was then held at 420°C for 1.5 hours to ensure complete decomposition and volatilization of the P123 template; afterwards, it was first cooled to 200°C at a rate of 3°C / min, and then slowly cooled to room temperature at a rate of 2°C / min. This heat treatment process removed the organic template P123, forming a... Figure 1 The porous compound modification layer 3 in the middle has a stable mesoporous pore structure 4, and the modification layer is an alumina functional layer.

[0125] (5) Post-processing and storage: Immerse the sample from step (4) in anhydrous ethanol for 5 minutes to remove any trace amounts of template decomposition products that may be attached. After immersion, gently dry with high-purity nitrogen. In a glove box, cut the sample to the required size (45 mm × 58 mm rectangular pieces). Immediately vacuum seal the resulting product with an aluminum-plastic composite film, fill with high-purity argon for protection, and store in a light-proof, dry environment for later use.

[0126] Example 2: Preparation of current collector The difference between this embodiment and embodiment 1 lies in steps (2) and (3), as follows: In step (2), the concentration of P123 is increased to 0.04-0.06 g / mL, and the static adsorption time of aluminum foil in the template solution is extended to 20-30 min to construct a thicker template layer.

[0127] In step (3), the number of ALD cycles is increased to the number of cycles required to achieve the target thickness.

[0128] Other settings are the same as in the embodiment.

[0129] Example 3: Preparation of a Sodium-ion Battery Cell Without a Negative Electrode This embodiment provides a negative electrode-free sodium-ion battery cell prepared using Example 1 or Example 2, specifically including the following steps.

[0130] (1) Preparation of the positive electrode: Positive electrode slurry preparation: Polyanionic sodium ferric sulfate (Na2Fe(SO4)2) was used as the positive electrode active material. Sodium ferric sulfate, polyvinylidene fluoride (PVDF) binder, conductive carbon black (Super P), carbon nanotubes (CNTs), and polyvinylpyrrolidone (PVP) dispersant were weighed at a mass ratio of 95:2.7:1:1:0.3. PVDF was dissolved in an appropriate amount of N-methylpyrrolidone (NMP) solvent to prepare a well-dispersed gel solution; Subsequently, sodium ferric sulfate powder, Super P, CNT, and PVP were added to the gel solution in steps, and the mixture was sheared and dispersed at 2000 rpm for 20 minutes using a high-speed disperser. The mixture was then stirred until a uniform positive electrode slurry with no particle agglomeration was formed. The solid content of the positive electrode slurry was approximately 50%.

[0131] Current collector and coating: A carbon-coated aluminum foil with a body thickness of 12μm and a double-sided carbon coating thickness of 1μm is used as the positive electrode current collector. The above positive electrode slurry is uniformly coated on the aluminum foil surface with a wet film thickness of 20-30μm using a precision coating machine to obtain the positive electrode sheet. The coating speed is 0.5 m / min.

[0132] Drying and cold pressing: The coated positive electrode sheet was transferred to an 80℃ oven for initial drying for 30 minutes, and then placed in a 120℃ vacuum oven for drying for 12 hours to remove residual solvent. The dried positive electrode sheet was then cold-pressed using a roller press, and the compaction density of the positive electrode material coating was approximately 2.1 g / cm³.

[0133] Cutting and drying: The cold-pressed positive electrode sheet is cut into rectangular sheets of 43×56 mm and dried again in a nitrogen vacuum oven at 85℃ for 12 hours.

[0134] (2) Preparation of electrolyte: The electrolyte was prepared in an argon-filled glove box with both moisture and oxygen content below 0.01 ppm. Sodium hexafluorophosphate (NaPF6) was added to diethylene glycol dimethyl ether (G2) solvent to prepare a 1.0 mol / L sodium salt solution. Subsequently, 3% (by mass) of fluoroethylene carbonate (FEC) was added as a film-forming additive, and 0.2 mol / L of trimethylsilanolate was added as a sodium supplement. All operations were performed at room temperature, and the electrolyte was allowed to stand for 24 hours after preparation to ensure complete dissolution and stability of all components.

[0135] (3) Cell assembly: Stacking assembly: The positive electrode sheet prepared above, the single-sided ceramic-coated polyethylene (PE) separator (the separator body thickness is 12 μm and the single-sided ceramic coating thickness is 4 μm), and the current collector prepared in Example 1 or Example 2 (as the negative electrode side, with the porous compound modification layer 3 facing the separator) are stacked and assembled in sequence to form a sandwich structure.

[0136] Packaging and electrolyte injection: An aluminum-plastic composite film is used as the packaging material. The stacked battery cell body is placed inside and heat-sealed on three sides. 1 mL of electrolyte is injected through the reserved injection port.

[0137] Vacuum sealing: After electrolyte injection, the battery cell is vacuum-sealed again. After sealing, it is left to stand at room temperature for 2 hours to ensure that the electrolyte is fully wetted and to remove internal air bubbles.

[0138] (4) Cell formation and aging: After ensuring the electrolyte fully impregnates the packaged battery cell, proceed with the formation and activation process as follows: Segmented constant current charging: First, constant current charging is performed at a rate of 0.05 C for 2 hours, and then the constant current charging is continued at a rate of 0.1 C for 3 hours. During this stage, the cumulative charging capacity reaches 40% of the rated capacity (SOC), completing the initial mild deposition of sodium metal on the modified current collector.

[0139] Constant current and constant voltage charging: Then charge at a constant current rate of 0.2 C to the upper limit voltage of 4.2V, and then switch to constant voltage charging at 4.2V until the charging current decays to 0.02 C to ensure the expulsion and deposition of active sodium.

[0140] First discharge: Finally, discharge at a constant current rate of 0.2 C to the cutoff voltage of 2.0 V to complete the entire formation process.

[0141] After formation, the cell is charged to 3.75 V at a rate of 0.2 C, and then aged at 45°C for 2-4 hours to promote the full formation and reconstruction of the stable solid electrolyte interphase (SEI) membrane, ultimately obtaining a high-performance sodium-ion cell without a negative electrode.

[0142] In addition, to verify the technical effect of the present invention, the following comparative tests were conducted: Comparative Example 1: Unmodified aluminum foil was used as the negative electrode current collector, and the other conditions were the same as in Example 3.

[0143] Comparative Example 2: The modified current collector prepared in Example 1 was used, but a carbonate electrolyte (1.0 M NaPF6-EC / DEC = 1 / 1, containing 5% FEC) was used. Specifically, ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a volume ratio of 1:1 as a solvent, sodium hexafluorophosphate (NaPF6) was added to a concentration of 1.0 mol / L, and then fluoroethylene carbonate (FEC) at 5% of the total mass of the electrolyte was added as a film-forming additive. The remaining conditions were the same as in Example 3.

[0144] It should be noted that the battery preparation conditions and battery size were the same in all embodiments and comparative examples under the same test.

[0145] The battery cells prepared in Examples 1-2 and Comparative Examples 1-2 were subjected to electrical performance tests. The test results are shown in Table 1 and 2. Figure 2-3 The specific test conditions are as follows: 1. Use 4.2-2.0V as the voltage range for the first formation cycle. First, charge at a constant current rate of 0.05C for 2 hours, then switch to a constant current rate of 0.1C for 3 hours. After resting for 2 hours, charge at a constant current rate of 0.2C to the upper limit voltage of 4.2V, then switch to constant voltage charging at 4.2V until the charging current decays to 0.02C to cut off. Finally, discharge at a constant current rate of 0.2C to the cutoff voltage of 2.0V. 2. Using a cycle voltage range of 4.2-2.6V, charge the battery with a constant current of 0.2C until the voltage reaches 4.2V; then apply a constant voltage at 4.2V to charge until the current drops to 0.05C; finally, discharge with a constant current of 0.5C to the cutoff voltage of 2.6V.

[0146] Table 1. Comparison of electrochemical performance between the examples and comparative examples

[0147] Combining Table 1 and Figure 2-3It can be seen that the first-cycle efficiency and cycle stability of Examples 1 and 2 are significantly improved. Specifically, the first-cycle coulombic efficiency of Examples 1 and 2 is significantly higher than that of Comparative Example 1 (more than 50%), proving that the porous compound modification layer 3 effectively reduces active sodium loss, and that the ether-based solvent electrolyte system has a synergistic effect in reducing active sodium loss. Furthermore, Example 2 retains 80% of its capacity after 50 cycles, while Example 1 retains 80% of its capacity after 35 cycles, whereas Comparative Example 1 is close to failure after formation, and Comparative Example 2's capacity retention drops to 40% after 20 cycles, indicating that the modified current collector can effectively suppress sodium dendrite growth and interfacial side reactions. Thus, by combining the modified current collector with a suitable ether-based electrolyte, the first-cycle efficiency, cycle life, and interfacial stability of the anode-less sodium-ion battery are significantly improved through interfacial synergistic effects, solving the technical bottlenecks of low coulombic efficiency and rapid cycle decay in traditional anode-less batteries.

[0148] In summary, 1. The porous compound modification layer 3 of this application constructs a physical barrier with a spatial structure at the current collector surface interface, which not only guides the uniform deposition / stripping reaction of sodium ions, but also significantly inhibits the growth of sodium dendrites, greatly improves battery safety, and further enhances battery cycle performance and longevity.

[0149] 2. An inert porous compound modification layer 3 isolates the current collector body 1 from direct contact with the electrolyte, blocking corrosion and side reactions, and preventing current collector failure.

[0150] 3. The porous, high specific surface area mesoporous structure provides a fast transport path for sodium ions through 4 channels, effectively reducing interfacial impedance and optimizing charge and discharge dynamics.

[0151] 4. The high porosity structure of the porous compound-modified layer 3 can buffer the volume expansion of sodium deposition, reduce interfacial stress damage, and extend cycle life.

[0152] The foregoing description has fully disclosed the specific embodiments of this application. It should be noted that any modifications made by those skilled in the art to the specific embodiments of this application do not depart from the scope of the claims. Accordingly, the scope of the claims of this application is not limited to the foregoing specific embodiments.

Claims

1. A current collector for a negative electrode-less sodium-ion battery, characterized in that, The current collector includes a current collector body and a porous compound modification layer located on at least one side surface of the current collector body; The porous compound-modified layer comprises multiple mesopore-sized pore structures, the exposed surface of the porous compound-modified layer has sodium-loving sites, and the surface of the pore structures serves as an interface for sodium ion deposition and stripping.

2. The current collector for a negative electrode-less sodium-ion battery according to claim 1, characterized in that, The sodium-loving sites include one or more of the following: sodium-loving functional groups, unsaturated coordination sites, metal nanoparticles, or sodium-loving intermediates. The sodium-loving functional group includes a hydroxyl group; The metal nanoparticles include at least one of iron, cobalt, or molybdenum; The sodium-loving intermediate includes at least one of the following: a carbon-based compound, a sodium-tin alloy intermediate, a sodium-bismuth alloy intermediate, a sodium-antimony alloy intermediate, a sodium-germanium alloy intermediate, a sodium phosphide intermediate, or a sodium sulfide intermediate.

3. The current collector for a negative electrode-less sodium-ion battery according to claim 1, characterized in that, At least a portion of the pore structure of the porous compound-modified layer is an interconnected three-dimensional mesoporous channel.

4. The current collector for a negative electrode-less sodium-ion battery according to claim 1, characterized in that, The current collector satisfies at least one of the following characteristics: The current collector body is at least one of aluminum-based current collector body or copper current collector body; The material of the porous compound modification layer includes one or more of mesoporous carbon, mesoporous metal compounds, mesoporous sulfides, or mesoporous selenium compounds; The thickness of the porous compound-modified layer is 5 nm-5 μm; The pore size of the pore structure is 2nm-500nm.

5. The current collector for a negative electrode-less sodium-ion battery according to claim 4, characterized in that, The current collector satisfies at least one of the following characteristics: The thickness of the porous compound modification layer is 5 nm-500 nm; The pore size of the pore structure is 2-200 nm.

6. The current collector for a negative electrode-less sodium-ion battery according to claim 4, characterized in that, The current collector satisfies at least one of the following characteristics: The material of the porous compound modification layer includes one or more of the following: mesoporous carbon, mesoporous aluminum compound, mesoporous zinc compound, mesoporous tin compound, mesoporous iron compound, mesoporous cobalt compound, mesoporous titanium compound, mesoporous antimony compound, mesoporous bismuth compound, mesoporous germanium compound, mesoporous phosphorus compound, mesoporous molybdenum compound, mesoporous molybdenum sulfide, mesoporous tin sulfide, mesoporous selenium molybdenum compound, or mesoporous selenium oxide. The material of the porous compound modification layer includes one or more of C, Al2O3, TiO2, ZnO, SnO2, Fe2O3, Co3O4, MoO3, SeO2, MoS2, SnS2 or MoSe2; The thickness of the porous compound-modified layer is 5-20 nm; The pore size of the pore structure is 2-30 nm.

7. The current collector for a negative electrode-less sodium-ion battery according to any one of claims 1-6, characterized in that, The current collector further includes a dense bonding layer, which is located between the surface of the current collector body and the porous compound modification layer.

8. The current collector for a negative electrode-less sodium-ion battery according to claim 7, characterized in that, The thickness of the dense bonding layer is 0.5 nm to 5 μm.

9. A method for preparing a current collector for a negative electrode-free sodium-ion battery, characterized in that, The preparation method includes: Provide the current collector body; A porous compound modification layer is formed on at least one side surface of the current collector body. The porous compound modification layer includes a plurality of mesopore-sized pore structures. The exposed surface of the porous compound modification layer has sodium-loving sites. The surface of the pore structures serves as an interface for sodium ion deposition and stripping.

10. The preparation method according to claim 9, characterized in that, The preparation method further includes: A dense bonding layer is formed between the current collector body and the porous compound modification layer; The thickness of the dense bonding layer is 0.5 nm to 5 μm.

11. The preparation method according to claim 9, characterized in that, The formation of a porous compound modification layer on at least one surface of the current collector body includes: A template layer is formed on at least one surface of the current collector body to obtain a composite, wherein the template layer has voids; The composite is subjected to vapor deposition to form a compound modification layer that fills the template layer; The template layer is removed to form the porous compound modified layer.

12. The preparation method according to claim 11, characterized in that, Before forming the template layer, the preparation method further includes: The current collector body is subjected to surface activation treatment, and the template layer is located on at least one side of the activated surface of the current collector body; A dense bonding layer is formed on the activated surface during the initial stage of the vapor deposition process.

13. The preparation method according to claim 11, characterized in that, The template layer is a soft template formed by immersing the current collector body in a template solution and then self-assembling the template material on the surface of the current collector body.

14. The preparation method according to claim 13, characterized in that, The template solution also includes a micelle expander, which is used to increase the micelle size in the template layer.

15. The preparation method according to claim 11, characterized in that, The process of removing the template layer to form the porous compound modification layer includes: In an inert gas environment, the composite having the compound-modified layer is heat-treated to decompose and / or volatilize the template layer, forming the porous structure, and then cooled to obtain the porous compound-modified layer.

16. A sodium-ion battery without a negative electrode, characterized in that, Includes the current collector for a negative electrode-less sodium-ion battery as described in any one of claims 1-8.

17. The sodium-ion battery according to claim 16, characterized in that, The electrolyte of the sodium-ion battery comprises an ether solvent and a sodium salt; the electrolyte satisfies at least one of the following characteristics: The ether solvent includes at least one of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether; The sodium salt includes one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium bis(trifluoromethanesulfonyl)imide, sodium di(fluorooxalateborate), and sodium di(fluorosulfonyl)imide.

18. The sodium-ion battery according to claim 17, characterized in that, The electrolyte also includes at least one of a film-forming additive and a sodium supplementation additive; The film-forming additives include one or more of the following compounds: fluoroethylene carbonate, vinylene carbonate, 1,3-propane sulphol, vinyl sulfate, and bicyclic sulfate. The sodium supplement includes at least one of sodium trimethylsilanolate and sodium amino acid; The mass percentage of film-forming additives in the electrolyte is 1-5%; The concentration of the sodium salt in the electrolyte is 0.8-2.0 mol / L; The concentration of the sodium supplement in the electrolyte is 0.1-0.5 mol / L.

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