A rust electrode material, a preparation method and application thereof

Abstract

The application discloses a rust electrode material and a preparation method and application thereof. The rust electrode material comprises two-dimensional conductive material, ferroferric oxide loaded on the two-dimensional conductive material, and zero-dimensional and one-dimensional conductive materials. The two-dimensional conductive material can deposit more ferroferric oxide, can be cooperatively constructed into a three-dimensional skeleton of multi-scale interconnection with the zero-dimensional and one-dimensional conductive materials, realizes space confinement of the ferroferric oxide, avoids the "loss" of the ferroferric oxide in the process of solution and redeposition in the cycle, and improves the deposition amount of the ferroferric oxide in the skeleton space, and improves the active material loading and reaction feasibility. The rust electrode material can be mixed with a binder to be dry-pressed into a negative electrode, and further assembled into a rust air battery. The application realizes the energy storage and release based on the reversible reaction between the rust and iron, constructs a new energy storage mechanism of charge and discharge cycles, and solves the problems of the current traditional energy storage system, such as the unsuitable deployment for the sudden demand and the insufficient performance.

Description

Technical Field

[0001] This invention relates to the field of air batteries, specifically to a rust electrode material, its preparation method, and its application. Background Technology

[0002] With the rapid development of the new energy industry, higher demands are being placed on the development of efficient, safe, and low-cost long-term energy storage systems. Currently, mainstream large-scale energy storage systems include pumped hydro storage, compressed air storage, lithium-ion battery systems, and flow batteries. Among these, flow batteries possess good safety and cycle life, making them suitable for renewable energy regulation and long-term energy storage. However, their low energy density, system complexity, and susceptibility to electrolyte cross-contamination and corrosion limit their application in space-constrained or cost-sensitive scenarios, thus hindering their commercial development. Therefore, exploring long-term energy storage systems with higher energy density, lower material costs, and sustainability has become a key research focus.

[0003] Iron-air batteries have a high specific capacity, and compared with lithium metal or zinc-based batteries, iron-air batteries are less prone to dendrite puncture during charging and discharging, and have the potential for sustainable long-term energy storage. In addition, iron resources are abundant, extraction technology is relatively simple, and cost is low, which is conducive to large-scale application. However, in the process of use, current iron-air batteries still have the following problems: (1) After assembly, factory pretreatment is required, such as discharge treatment before charging, which is not conducive to on-site deployment for sudden demand; (2) Traditional iron electrode sheets have problems such as cracking and easy peeling, unstable structure, and insufficient cycle performance and service life, which are due to the drastic volume change of iron during oxidation-reduction, incomplete reconstruction of conductive network, and insufficient design of binder system; (3) Due to the limitations of reaction kinetics and mass transfer conditions, the usable surface load of iron electrode sheets is still low, and the material utilization rate decreases significantly under high surface load conditions, resulting in the overall energy of the battery not being fully utilized, which hinders its large-scale energy storage application prospects.

[0004] It should be noted that the information disclosed in the background section above is only for understanding the background of this application. Therefore, the background section of this invention may include background information about the problems or environment of this invention, and is not necessarily a description of the prior art. Thus, the content included in the background section does not constitute an admission of the prior art by the applicant. Summary of the Invention

[0005] The purpose of this invention is to overcome one or more shortcomings in the prior art and provide a new rust electrode material with outstanding performance.

[0006] The present invention also provides a negative electrode containing rust electrode material, a composite material, and a rust-air battery, as well as the application of the rust-air battery in energy storage.

[0007] To achieve the above objectives, the present invention employs the following technical solution:

[0008] A rust electrode material comprising a two-dimensional conductive material, ferric oxide loaded on the two-dimensional conductive material, a zero-dimensional conductive material, and a one-dimensional conductive material;

[0009] In the rust electrode material, the two-dimensional conductive material accounts for 10%-40% by mass percentage, and the amount of the two-dimensional conductive material added is more than 1.5 times the amount of either the zero-dimensional conductive material or the one-dimensional conductive material added.

[0010] According to some specific aspects of the present invention, in the rust electrode material, the two-dimensional conductive material forms a basic framework (providing a large area for the deposition of ferric oxide), the zero-dimensional conductive material and the one-dimensional conductive material respectively form an epitaxial framework, and the basic framework and the epitaxial framework together constitute an interconnect framework (the interconnect structure has a confinement effect, which can restrict the aggregation and migration behavior of ferric oxide on a spatial scale and significantly improve its deposition capacity), and the ferric oxide is distributed in the interconnect framework.

[0011] In some embodiments of the present invention, the ferric oxide, the zero-dimensional conductive material, and the one-dimensional conductive material are all loaded on the two-dimensional conductive material.

[0012] In some embodiments of the present invention, the amount of the two-dimensional conductive material added is 1.5-15 times, more 1.5-12 times, and even more 2-10 times the amount of either the zero-dimensional conductive material or the one-dimensional conductive material added.

[0013] In some embodiments of the present invention, the interconnect skeleton includes multiple conductive paths, and each of the conductive paths includes the zero-dimensional conductive material, the one-dimensional conductive material, and the two-dimensional conductive material.

[0014] According to some preferred and specific aspects of the present invention, the zero-dimensional conductive material, the one-dimensional conductive material and the two-dimensional conductive material are all conductive carbon materials.

[0015] Furthermore, the two-dimensional conductive material may include, but is not limited to, graphene, carbon nanosheets, etc.

[0016] Furthermore, the one-dimensional conductive material may include, but is not limited to, carbon nanofibers and / or carbon nanotubes. In some embodiments of the present invention, the one-dimensional conductive material may be single-walled carbon nanotubes and / or multi-walled carbon nanotubes.

[0017] Furthermore, the zero-dimensional conductive material may include, but is not limited to, acetylene black particles, etc.

[0018] In some embodiments of the present invention, the thickness of the two-dimensional conductive material is 1-300 nm, and the sheet diameter (or surface length) is 0.5-20 μm. Further, the thickness of the two-dimensional conductive material is 1-200 nm, and the sheet diameter (or surface length) is 0.5-15 μm. Even further, the thickness of the two-dimensional conductive material is 1-50 nm, and the sheet diameter (or surface length) is 1-10 μm.

[0019] In some embodiments of the present invention, the aspect ratio of the one-dimensional conductive material is 100-3000.

[0020] In some embodiments of the present invention, the particle size of the zero-dimensional conductive material is 10-500 nm.

[0021] In some embodiments of the present invention, the ferric oxide exists in the form of ferric oxide particles, the particle size of which is 10-1000 nm.

[0022] In some embodiments of the present invention, the ferric oxide accounts for 50%-75% of the rust electrode material by mass percentage.

[0023] According to some preferred aspects of the present invention, in the rust electrode material, the mass ratio of the zero-dimensional conductive material, the one-dimensional conductive material and the two-dimensional conductive material is 1:0.1-10:1.5-40.

[0024] Furthermore, in the rust electrode material, the mass ratio of the zero-dimensional conductive material, the one-dimensional conductive material, and the two-dimensional conductive material is 1:0.2-2.8:3-15.

[0025] Furthermore, the mass ratio of the zero-dimensional conductive material, the one-dimensional conductive material, and the two-dimensional conductive material is 1:0.4-2.5:3.5-9.

[0026] According to some preferred aspects of the present invention, in the rust electrode material, the two-dimensional conductive material accounts for 15%-40% by mass percentage, the one-dimensional conductive material accounts for 1%-10% by mass percentage, and the zero-dimensional conductive material accounts for 1%-10% by mass percentage.

[0027] Furthermore, by mass percentage, the total content of the one-dimensional conductive material and the zero-dimensional conductive material in the rust electrode material is 5%-15%.

[0028] In some embodiments of the present invention, by mass percentage, the two-dimensional conductive material accounts for 18%-36% of the rust electrode material, the one-dimensional conductive material accounts for 3%-7% of the rust electrode material, and the zero-dimensional conductive material accounts for 3%-7%.

[0029] Another technical solution provided by the present invention: a method for preparing the above-mentioned rust electrode material, the method comprising: mixing ferric oxide, zero-dimensional conductive material, one-dimensional conductive material and two-dimensional conductive material.

[0030] According to some preferred aspects of the invention, the mixing and homogenization are carried out by a dry mixing method.

[0031] In some preferred embodiments of the present invention, the method for preparing the rust electrode material includes:

[0032] Under solvent-free conditions, ferric oxide and a two-dimensional conductive material are first mixed and stirred to obtain an intermediate. Then, a zero-dimensional conductive material and a one-dimensional conductive material are added to the intermediate, and the mixture is stirred and stirred again.

[0033] Another technical solution provided by the present invention is a rust electrode material, wherein the rust electrode material is a mixture obtained by uniformly mixing ferric oxide, zero-dimensional conductive carbon material, one-dimensional conductive carbon material and two-dimensional conductive carbon material; wherein the mass ratio of the ferric oxide, the two-dimensional conductive carbon material, the one-dimensional conductive carbon material and the zero-dimensional conductive carbon material is 1:0.2-0.8:0.04-0.15:0.04-0.15.

[0034] In some embodiments of the present invention, the mass ratio of the ferric oxide, the two-dimensional conductive carbon material, the one-dimensional conductive carbon material and the zero-dimensional conductive carbon material is 1:0.25-0.75:0.05-0.15:0.04-0.12.

[0035] Another technical solution provided by the present invention: a composite material for preparing a negative electrode for an air battery, the composite material comprising the rust electrode material and binder described above.

[0036] In some embodiments of the present invention, the adhesive may include, but is not limited to, polytetrafluoroethylene (PTFE), hydroxypropyl methylcellulose (HPMC), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), etc., and one or more combinations thereof may be selected.

[0037] In some embodiments of the present invention, the amount of binder added to the composite material accounts for 1%-10% of the amount of rust electrode material added, by weight percentage.

[0038] In some embodiments of the present invention, the composite material is prepared by mixing and homogenizing the rust electrode material and the binder.

[0039] According to some specific aspects of the present invention, the rust electrode material is granular.

[0040] Furthermore, the granular rust electrode material is prepared by the following method:

[0041] Ferric oxide, zero-dimensional conductive materials, one-dimensional conductive materials, and two-dimensional conductive materials are granulated to form rust electrode materials.

[0042] In some embodiments of the present invention, the granulation method includes spray granulation.

[0043] In some embodiments of the present invention, the granular rust electrode material includes a spherical shape.

[0044] Another technical solution provided by the present invention: a negative electrode for an air battery, wherein the negative electrode contains the composite material and current collector described above for preparing a negative electrode for an air battery, and the composite material is loaded on the current collector.

[0045] In some embodiments of the present invention, the current collector may include, but is not limited to, a stainless steel mesh.

[0046] In some embodiments of the present invention, the thickness of the current collector is 5-20 μm.

[0047] In some embodiments of the present invention, the thickness of the negative electrode is 500 μm-10 mm.

[0048] Another technical solution provided by the present invention: a method for preparing the negative electrode for an air battery as described above, the method comprising: placing the composite material on the current collector and pressing it into shape.

[0049] In some embodiments of the present invention, the pressure used for the pressure molding is 5-20 MPa. Further, according to some specific aspects of the present invention, the pressure used for the pressure molding is 8-15 MPa.

[0050] Furthermore, the pressure molding can be performed using a press.

[0051] In some embodiments of the present invention, the pressure molding includes hot pressing.

[0052] In some embodiments of the present invention, the composite material is treated by rolling, grinding or shearing before the pressure molding is performed, so that the binder is fibrous.

[0053] Another technical solution provided by the present invention: a negative electrode for an air battery, the negative electrode comprising a current collector and a rust electrode material loaded on the current collector, the rust electrode material comprising ferric oxide, zero-dimensional conductive material, one-dimensional conductive material and two-dimensional conductive material, the conductivity of the negative electrode being 1-10 S / cm and the porosity being 40%-65%.

[0054] Another technical solution provided by the present invention is a rust-air battery, which includes a negative electrode, an air positive electrode and an electrolyte. The negative electrode is an air battery negative electrode as described above, or an air battery negative electrode made by the preparation method of the air battery negative electrode described above.

[0055] According to certain aspects of the present invention, the reactions of the negative and positive electrodes during the initial charging are as follows:

[0056] Negative electrode reaction: Fe2O3 + 3H2O + 2e - →2Fe(OH)2+2OH - Fe(OH)2+2e - →Fe+2OH - ;

[0057] Positive electrode reaction: 4OH - →O2 + 2H2O + 4e - .

[0058] According to the present invention, the rust-air battery has an initial discharge specific capacity of 400-500 mAh / g and a fifth discharge specific capacity of 550-650 mAh / g at a charge-discharge rate of 0.1C, and a capacity retention rate of 77%-90% after 40 cycles.

[0059] Another technical solution provided by the present invention is a method for using the rust-air battery described above for energy storage, wherein the rust-air battery does not need to be discharged first during energy storage and can be directly used for charging and energy storage.

[0060] According to some specific aspects of the present invention, in the application of the rust-air battery, the ferric oxide in the air battery gains electrons and is reduced to iron during charging, and the iron loses electrons and is oxidized to iron oxide during discharging, thus realizing the storage and release of energy in the process of reduction and oxidation.

[0061] In this invention, by mixing and homogenizing ferric oxide, zero-dimensional conductive materials, one-dimensional conductive materials, and two-dimensional conductive materials, an interconnected framework can be constructed from these three materials. Ferric oxide is loaded onto the two-dimensional conductive material, which has a sheet-like structure and a large planar dimension, thus serving as a basic framework. In addition to ferric oxide, zero-dimensional and one-dimensional conductive materials can also be deposited or loaded onto the two-dimensional conductive material during the mixing process, for example, on the surface of the two-dimensional conductive material or other load-bearing parts. These zero-dimensional and one-dimensional conductive materials can act as additional epitaxial frameworks. After these epitaxial frameworks are mixed and blended together with each other and with the basic framework, a multi-scale interconnected framework can be formed.

[0062] Furthermore, the interconnected framework in this invention refers to the existence of conductive pathways in multiple dimensions, and the presence of multiple conductive pathways, thereby constructing a three-dimensional cross-linked network structure with conductive pathways in multiple spatial dimensions. This three-dimensional cross-linked network spatially confines ferric oxide, preventing its "loss" due to dissolution and redeposition during the cycling process. In addition, this interconnected framework significantly increases the deposition amount of ferric oxide in three-dimensional space, improving the loading of active materials and the feasibility of the reaction.

[0063] In this invention, the terms "zero-dimensional," "one-dimensional," and "two-dimensional" in the zero-dimensional conductive material, one-dimensional conductive material, and two-dimensional conductive material mentioned herein can be understood in their usual sense, for example, as follows:

[0064] Zero-dimensional (0D) materials typically refer to materials where all three dimensions are approximately the same, with no significant aspect ratio. The dimensions in each direction are relatively close, exhibiting a discrete granular structure. For example, the dimensions in all three dimensions are on the micrometer or nanometer scale. Typical materials include nanoparticles, such as metal particles, acetylene black particles, Ketjen black, and conductive carbon black. Furthermore, the granular form can generally be spherical or near-spherical. Even when exhibiting irregular geometric shapes, their three-dimensional dimensions (length, width, and height) are basically on the same order of magnitude, without significant directional extension.

[0065] One-dimensional (1D) materials typically refer to materials that exhibit a large aspect ratio (length / diameter) in three-dimensional space. This means that one dimension is large-scale, while the other two dimensions are smaller. For example, only one dimension, such as length, is macroscopic, while the others, such as width and height (or diameter), are small, potentially at the nanoscale, and the overall structure appears as a slender "wire" or "tubular" shape. Typical examples include carbon nanotubes and carbon nanowires.

[0066] Two-dimensional (2D) materials typically refer to materials that have a large planar dimension and a thin thickness in three-dimensional space (thickness refers to the dimension perpendicular to the plane, which can be measured by atomic force microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and optical microscopy, etc.). That is, the dimension in one dimension is small, and the other two dimensions are large. For example, the dimension in only one dimension is at the nanoscale (usually the thickness), and the other two dimensions are at the macroscale, presenting an overall sheet or layered structure; typical materials include graphene and carbon nanosheets.

[0067] In this invention, particle size refers to the diameter or equivalent diameter of a particle, used to characterize the size of the particle. For regular spherical particles, particle size is its geometric diameter; for non-spherical particles, particle size is usually expressed as "equivalent particle size", which can be calculated by methods such as geometric equivalent particle size and volume equivalent particle size. In this invention, the volume equivalent particle size measurement method is used to measure the diameter of spherical particles.

[0068] In this invention, the sheet diameter (or surface length) of a two-dimensional conductive material refers to the lateral dimension of the two-dimensional material in a plane, usually expressed as "equivalent diameter" or "characteristic length" to describe the size of the sheet. Generally, circular sheets are expressed as diameter, while irregular sheets are usually expressed as the length of the longest diagonal or as equivalent diameter (defined as the diameter of a circle with the same projected area as the sheet). This invention adopts the definition of equivalent diameter.

[0069] Due to the application of the above-described technical solution, the present invention has at least the following advantages compared with the prior art:

[0070] Based on the problems existing in the use of air batteries, such as the need for pretreatment after assembly, unstable iron electrode structure, low areal load, and unsatisfactory utilization of active materials, this invention proposes a renewable energy storage unit (rust-air battery) based on the reaction mechanism of rust (ferric oxide). It utilizes the reversible oxidation-reduction characteristics of iron oxide to construct an electrochemical energy conversion mechanism. Combined with an air positive electrode and an aqueous electrolyte, a novel energy storage unit that can be charged first, then discharged and cycled can be constructed.

[0071] This energy storage unit utilizes the rust electrode material with outstanding performance proposed in this invention. This rust electrode material uses rust, i.e., ferric oxide, as the core active material, supplemented by conductive materials of various dimensions. The inventors of this invention are the first to propose using a two-dimensional conductive material as a deposition carrier, loading ferric oxide onto it, and combining it with one-dimensional and zero-dimensional conductive materials to form an extended network-like epitaxial framework. The two-dimensional conductive material serves as the main basic framework structure, enabling the loading of more active materials. Through the synergistic effect of the three conductive materials, an interconnected core-external framework can be formed inside the electrode. This multi-pathway and three-dimensional conductive network construction:

[0072] Firstly, it can provide more and less obstructed electron transport and transfer paths, which can effectively shorten the path of electrons from the active material to the current collector, thus improving electron conduction ability, conductivity and utilization of active materials.

[0073] Secondly, this interconnected framework can be used to stably confine ferric oxide or other active materials such as iron or ferrous hydroxide generated during the charging and discharging process within a certain spatial range. Simultaneously, it alleviates stress concentration caused by volume expansion during cycling, reducing the risk of cracking and significantly improving the stability of the electrode structure. In particular, the active material is always confined within the interconnected framework, increasing its utilization rate and preventing "loss" during dissolution and redeposition during cycling. This further avoids the drawbacks of structural instability causing some active material to detach or fail to contact conductive materials, thus preventing participation in electrochemical reactions. Furthermore, this interconnected framework significantly increases the deposition amount of ferric oxide in three-dimensional space, enhancing the active material loading and reaction feasibility.

[0074] Furthermore, the simultaneous presence of the three conductive materials results in an ideal porosity in the prepared electrode, which is conducive to the migration of ions in the electrolyte and the smooth progress of electrochemical reactions. In addition, the strong porosity allows the electrolyte to quickly penetrate into the electrode, shortening the ion diffusion path and thus improving the charge transport efficiency. Moreover, the presence of these micropores can also provide sufficient buffer space for the negative electrode, which has volume changes, during the charging and discharging process, preventing the negative electrode structure from cracking, breaking or peeling.

[0075] Furthermore, the combined use of three types of conductive materials not only constructs a multi-dimensional interconnected framework but also provides better structural support for the overall structure. This facilitates the preparation of the anode of this invention using a solvent-free dry pressing molding process, which is simple, easy to repeat, and has good consistency. In contrast, if a conventional iron anode is prepared using a dry pressing molding process, it is very easy to cause excessively high compaction density, which cannot guarantee sufficient porosity. This results in difficulty in electrolyte penetration, and the active material is prone to loss, shedding, or significant migration during cycling, leading to low utilization and insufficient battery cycle performance.

[0076] Meanwhile, the combined use of the aforementioned conductive materials and the applicability of dry molding also allow for an increase in the amount of active material used in this invention (no solvent, the proportion of active material can be increased), thereby increasing the areal loading of active material in the negative electrode, making it suitable for preparing thick electrodes.

[0077] In summary, the negative electrode made of rust electrode material used in this invention, when applied to an air battery, not only possesses excellent cycle stability, coulombic efficiency, and specific capacity, but also can be directly charged and used after assembly, exhibiting rapid response and active scheduling capabilities. It can be applied to large-scale, long-term energy storage and is beneficial for on-site deployment for sudden demands. It can also work in conjunction with intermittent power generation systems, demonstrating significant industrial practical value. Attached Figure Description

[0078] Figure 1 A schematic diagram showing the distribution of various materials in the rust-resistant negative electrode material in this embodiment of the invention;

[0079] Figure 2 A schematic diagram of the structure of the negative electrode for an air battery in an embodiment of the present invention;

[0080] Figure 3 A schematic diagram of the structure of the air positive electrode in an embodiment of the present invention;

[0081] Figure 4 This is a schematic diagram of the explosion of the rust-air battery in an embodiment of the present invention;

[0082] Figure 5 This is a schematic diagram of the rust-air battery after assembly in an embodiment of the present invention;

[0083] Figure 6 This is a scanning electron microscope image of the rust electrode material prepared in Example 3-1 of the present invention;

[0084] Figure 7 This is a discharge curve of the rust-air battery prepared in Example 4-1 of the present invention after 40 cycles;

[0085] Figure 8 The graphs show the cycle performance test results of the rust-air batteries obtained in Examples 4-1, 4-1 and 4-5 of this invention. Detailed Implementation

[0086] Currently, iron-air batteries require pre-processing in the factory after assembly, such as discharge treatment before charging, which is not conducive to on-site deployment for sudden needs. At the same time, if the anode is prepared by the traditional wet process, the following problems are likely to occur: (1) The traditional wet process requires the active materials, conductive agents and binders to be dispersed in organic or aqueous solvents to form a slurry. The slurry is required to have good viscosity and dispersion uniformity. Its solid content is generally low, and the corresponding surface load is low; (2) If the coating thickness is too thick during the coating process of the traditional wet process, uneven drying, cracking, thick edges, poor adhesion and slurry sedimentation are likely to occur. Therefore, the coating thickness is generally controlled in a low range, which further limits the surface load; (3) The traditional wet process is accompanied by a large amount of solvent volatilization during the drying process. When drying, the material shrinks and forms a large porosity and an uneven pore structure, which affects the stress distribution. In subsequent cycles, the volume change of the active material leads to local stress concentration, which can easily cause microcracks in the electrode. (4) In the traditional wet process, the binder may migrate during the drying process, resulting in local poor bonding. The electrode is prone to cracking under the stress generated during the cycle. At the same time, the traditional wet process has higher requirements for the binder. In order to ensure the stability of the slurry and the mechanical strength of the electrode, a higher amount of binder is often required, which reduces the proportion of active material and thus reduces the surface load. Furthermore, in practice, it has been found that the dry process can directly press the powder together without a solvent drying process, thus avoiding the problems of low solid content, inability to thick coating, and drying cracking that exist in the wet process. However, when the current iron anode material is formed using the dry process, the compaction density of the iron anode is too high, the electrolyte penetration is difficult, the active material is prone to loss, shedding or significant transfer during cycling, and it is not easy to contact the conductive agent, resulting in low utilization of the active material and insufficient battery cycle performance. There are obvious problems of one aspect being taken into account but the other is not.

[0087] Based on this, the inventors of this invention, through in-depth research and extensive experimentation, have for the first time proposed a novel energy storage mechanism that enables the storage and release of energy based on the reversible reaction between rust and iron, thus constructing a rechargeable and cyclical energy storage system. Furthermore, they proposed constructing an interconnected framework, specifically by introducing conductive materials of three dimensions—point, line, and surface—into the negative electrode, with two-dimensional conductive materials serving as the main basic framework structure, supplemented by an extensional framework formed by zero-dimensional and one-dimensional conductive materials. These three elements work together to construct a multi-dimensional interconnected framework, thereby solving the problems of existing iron-air batteries being unsuitable for deployments with sudden demands and the trade-offs in processing iron negative electrodes.

[0088] Furthermore, this invention relates to and provides a novel rust electrode material with outstanding performance. The rust electrode material comprises a two-dimensional conductive material, ferric oxide supported on the two-dimensional conductive material, a zero-dimensional conductive material, and a one-dimensional conductive material; wherein, by mass percentage, the two-dimensional conductive material accounts for 10%-40% of the rust electrode material, and the amount of the two-dimensional conductive material added is more than 1.5 times the amount added of either the zero-dimensional conductive material or the one-dimensional conductive material.

[0089] Zero-dimensional conductive materials, one-dimensional conductive materials, and two-dimensional conductive materials constitute the interconnect framework, with ferric oxide distributed within the interconnect framework.

[0090] See Figure 1 As shown, this is a specific example of the present invention. The ferric oxide, the zero-dimensional conductive material, and the one-dimensional conductive material are all loaded onto the two-dimensional conductive material. The ferric oxide, the zero-dimensional conductive material, and the one-dimensional conductive material are mixed together, with the two-dimensional conductive material serving as a carrier, thereby constructing a three-dimensional interconnected framework structure with multiple conductive pathways in both the horizontal and vertical directions. This arrangement also ensures that any conductive pathway contains the zero-dimensional conductive material, the one-dimensional conductive material, and the two-dimensional conductive material, which not only have a synergistic effect but also mutually confine each other, constructing a stable framework network structure.

[0091] Zero-dimensional conductive materials, one-dimensional conductive materials, and two-dimensional conductive materials can be any solid material with excellent conductivity. For example, they can all be conductive carbon materials. Conductive carbon materials come in various forms and are readily available, such as the zero-dimensional, one-dimensional, and two-dimensional conductive carbon materials required by this invention. They are commercially available or prepared using methods commonly used in the art. Zero-dimensional conductive carbon materials can be acetylene black particles, Ketjen black, conductive carbon black, etc.; one-dimensional conductive carbon materials can be carbon nanofibers, carbon nanotubes, etc.; and two-dimensional conductive carbon materials can be graphene, carbon nanosheets, etc.

[0092] The thickness of the two-dimensional conductive material is 1-300 nm, and the sheet diameter (or face length) is 0.5-20 μm. Further, the thickness of the two-dimensional conductive material is 5-200 nm, and the sheet diameter (or face length) is 1-20 μm. Even further, the thickness of the two-dimensional conductive material is 5-100 nm, and the sheet diameter (or face length) is 1-15 μm. According to some specific aspects of the invention, the thickness of the two-dimensional conductive material is 1-50 nm, and the sheet diameter (or face length) is 1-10 μm. Furthermore, the thickness of the two-dimensional conductive material can be 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 15 nm, 17 nm, 20 nm, 22 nm, 25 nm, 28 nm, 30 nm, 33 nm, 35 nm, 36 nm, 38 nm, 40 nm, 42 nm, 43 nm, 44 nm, 45 nm, 46 nm, 48 nm, 50 nm, 60 nm, 80 nm, 100 nm, 120 nm, 130 nm, etc. The thicknesses of two-dimensional conductive materials can range from nm, 150nm, 180nm, 200nm, 250nm, and 280nm, with sheet diameters of 0.5μm, 0.8μm, 1μm, 1.2μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm, 9.5μm, 9.8μm, 10μm, 12μm, 13μm, 15μm, 16μm, 18μm, and 20μm. These materials are commercially available. However, in practice, the thickness and sheet diameter of two-dimensional conductive materials may not be entirely uniform, but rather fall within a general range.

[0093] The aspect ratio of one-dimensional conductive materials is 100-3000. Furthermore, the aspect ratio of the one-dimensional conductive material is 100-2500, or 110-2300, or 120-2000, or 130-1800, or 140-1500, or 150-1200, or 155-1800, or 155-1500, or 155-1200, or 155-1000, or 200-800, or 250-700, or 300-600, or 350-500, or 400-900, or 450-900, or 550-900, or 650-1500, or 600-1200, or 650-1000, or 700-900, or 750-850, etc.

[0094] The particle size of zero-dimensional conductive materials is 10-500 nm. Further, the particle size of zero-dimensional conductive materials is 10-100 nm. Even further, the particle size of zero-dimensional conductive materials is 12-450 nm, or 15-400 nm, or 20-450 nm, or 25-400 nm, or 30-350 nm, or 35-300 nm, or 40-350 nm, or 45-300 nm, or 50-250 nm, or 60-500 nm, or 65-450 nm, or 70-400 nm, or 75-350 nm, or 80-300 nm, or 85-250 nm, or 90-200 nm, or 95-150 nm, or 100-120 nm, etc.

[0095] Ferric oxide exists in the form of ferric oxide particles with a particle size of 10-1000 nm. Further, the particle size of the ferric oxide particles can be 12-950 nm, or 15-900 nm, or 20-850 nm, or 25-800 nm, or 30-750 nm, or 35-700 nm, or 40-650 nm, or 45-600 nm, or 50-550 nm, or 60-500 nm, or 65-450 nm, or 70-400 nm, or 75-350 nm, or 80-300 nm, or 85-250 nm, or 90-200 nm, or 95-150 nm, or 100-120 nm, etc.

[0096] In the rust electrode material, the mass ratio of zero-dimensional conductive material, one-dimensional conductive material, and two-dimensional conductive material is 1:0.1-10:1.5-40. Further, the mass ratio of zero-dimensional conductive material, one-dimensional conductive material, and two-dimensional conductive material is 1:0.2-2.8:3-15. Even further, the mass ratio of zero-dimensional conductive material, one-dimensional conductive material, and two-dimensional conductive material is 1:0.4-2.5:3.5-9.

[0097] In specific implementation cases, ferric oxide accounts for 50%-75% of the rust electrode material by mass percentage. For example, ferric oxide can account for 51%-55%, or 56%-58%, or 59%-62%, or 63%-65%, or 66%-68%, or 69%-70%, or 71%-72%, or 73%-74%, or 52%-57%, or 53%-61%, or 64%-67%, or 54%-57%, or 60%-69%, etc. Furthermore, by mass percentage, two-dimensional conductive materials account for 15%-40% of the rust electrode material, one-dimensional conductive materials account for 1%-10%, and zero-dimensional conductive materials account for 1%-10%. Even further, by mass percentage, the total content of one-dimensional and zero-dimensional conductive materials in the rust electrode material accounts for 5%-15%. Furthermore, by mass percentage, in rust electrode materials, two-dimensional conductive materials account for 18%-36%, one-dimensional conductive materials account for 3%-7%, and zero-dimensional conductive materials account for 3%-7%.

[0098] In this invention, the interconnected framework constructed by the above ratio in the rust electrode material can achieve excellent synergistic effect with ferric oxide. After being made into a negative electrode, it can obtain better conductivity and cycle stability. The utilization rate of ferric oxide is high, which is conducive to the preparation of air batteries with better performance.

[0099] Meanwhile, the novel rust electrode material proposed in this invention can be formed by mixing ferric oxide, zero-dimensional conductive material, one-dimensional conductive material and two-dimensional conductive material to form an interconnected framework, with ferric oxide distributed in the interconnected framework. This structure allows the rust electrode material of this invention to be mixed using a dry mixing method. When further mixed with a binder, it can form a composite material for preparing negative electrodes for air batteries, allowing the composite material to bond with the current collector. Then, it can be molded by pressure or hot pressing. This not only avoids the defects of wet process, but also avoids the defects of conventional iron negative electrodes using dry process, such as excessively high compaction density, difficulty in electrolyte penetration, easy loss, shedding or significant transfer of active material during cycling, and difficulty in contact with conductive agent. It overcomes the problems of sacrificing one aspect for another in the prior art.

[0100] Furthermore, the binder may include, but is not limited to, polytetrafluoroethylene (PTFE), hydroxypropyl methylcellulose (HPMC), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), etc., and one or more combinations thereof may be selected. By weight percentage, the binder accounts for 1%-10% of the rust electrode material in the composite material, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc. The composite material can be prepared by mixing and homogenizing the rust electrode material and the binder.

[0101] The following is combined with Figures 2 to 5 The negative electrode for an air battery containing rust electrode material, the rust air battery, and their preparation methods are described.

[0102] The negative electrode for an air battery comprises a composite material and a current collector. The composite material includes rust-colored electrode material and a binder, and is loaded onto the current collector. When the active material in the composite material is in direct contact with the current collector, electrons are directly conducted through the current collector, for example, electrons are transferred to or from the active material through the current collector. When the active material is not in direct contact with the current collector, electrons are transferred in and out through a multi-path and non-blocking interconnected framework. Due to the three-dimensional interconnected conductive pathways, electrons can be rapidly transferred between the active material and the current collector, greatly improving electron conductivity. The material and form of the current collector are not particularly limited. Furthermore, the conductive substrate material, which is in close contact with the active material in the electrode and is used to collect electrons (or ions) and transport them to the external circuit (or counter electrode), can be appropriately determined. Metal materials can be used, and preferably a mesh that allows the electrolyte to penetrate smoothly, such as a stainless steel mesh. The thickness of the current collector is not particularly limited and can be appropriately determined. Typically, the thickness of the current collector can be 5-20 μm, for example, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, etc.

[0103] Furthermore, in this invention, due to the presence of a special rust-colored electrode material, the negative electrode using this rust-colored electrode material can be prepared using dry pressure molding (the pressure used in pressure molding is 5-20 MPa, and can be further 8-15 MPa), or dry hot pressing molding. The main purpose of heating is to allow the added binder to exert its adhesive effect. Alternatively, before pressure molding, the composite material can be rolled, ground, or subjected to shear force to fiberize the binder, forming a filamentous structure, thereby achieving the adhesive effect. Practice shows that this invention can achieve a high areal loading of the active material, and the negative electrode can be made thicker. The iron content of this negative electrode... Rust-air batteries exhibit excellent performance; in specific cases, the thickness of the negative electrode ranges from 500μm to 10mm, for example, it can be 500μm, 510μm, 520μm, 530μm, 540μm, 550μm, 580μm, 600μm, 620μm, 650μm, 680μm, 700μm, 730μm, 750μm, 780μm, 800μm, 820μm, 850μm, 900μm, 920μm, 950μm, 980μm, 990μm, 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 8mm, 10mm, etc.

[0104] Furthermore, rust electrode materials can exist in granular form and be used to prepare negative electrodes for air batteries. In practice, it has been found that by making rust electrode materials into granules, on the one hand, the structural stability is enhanced; on the other hand, parameters can be controlled, thereby controlling the particle size distribution, which is beneficial for preparing uniform electrodes and suitable for large-scale production. In addition, the granular structure can further improve the contact performance between the active material ferric oxide and the conductive material, reducing the electron transport impedance of the electrode system. The method for making rust electrode materials into granules is not particularly limited; for example, spray granulation can be used, and other methods can also be employed. Spray granulation involves dispersing ferric oxide, zero-dimensional conductive materials, one-dimensional conductive materials, and two-dimensional conductive materials in a solvent to form a slurry, which is then spray-dried using a spray dryer to obtain granular rust electrode materials. Granular rust electrode materials include spherical forms. In this invention, "spherical morphology" can refer to a standard spherical structure or a roughly spherical or near-spherical structure.

[0105] This invention solves the problem of balancing conductivity and porosity in existing iron anodes. Conventional iron anodes are made by mixing active materials with conventional conductive agents to form a slurry, coating it onto a current collector, and then drying it. In practice, attempts have been made to mix active materials with conventional conductive agents and then pressurize the mixture onto a current collector. However, neither of these methods can achieve excellent conductivity and porosity. This invention proposes a special rust electrode material, which includes ferric oxide, zero-dimensional conductive materials, one-dimensional conductive materials, and two-dimensional conductive materials. The combination of multiple conductive materials with ferric oxide achieves a conductivity of 1-10 S / cm and a porosity of 40%-65% for the anode.

[0106] Furthermore, in a specific case, the preparation method of the negative electrode for an air battery includes:

[0107] Ferric oxide and a two-dimensional conductive material are mixed evenly, then a one-dimensional conductive material and a zero-dimensional conductive material are added, and the mixture is continued to be mixed evenly to obtain a rust-containing negative electrode material.

[0108] Then, the rust-colored negative electrode material and the binder are mixed and homogenized under high-speed stirring to obtain the composite material;

[0109] A current collector is placed in a template, and then a composite material is placed on top of the current collector. The material is then pressed and molded using a press to produce a negative electrode for an air battery. This negative electrode is sheet-like, as illustrated in the diagram. Figure 2 As shown, the lower layer is the current collector 10, and the upper layer is the composite material 11.

[0110] The rust-air battery includes a negative electrode, an air positive electrode, and an electrolyte. The negative electrode is the same as the negative electrode used in air batteries.

[0111] Air cathodes can use existing conventional structures and materials without any particular restrictions.

[0112] An air positive electrode can be prepared as follows: a solvent, Nafion (perfluorosulfonic acid resin) solution, a catalyst, and a conductive agent are mixed to form a positive electrode slurry. This slurry is then placed on a positive electrode current collector and dried to obtain the air positive electrode. A schematic diagram is shown below. Figure 3 As shown, the lower layer is the positive electrode current collector 12, and the upper layer is the positive electrode coating 13 after the positive electrode slurry is dried; further, the solvent can be water and / or alcohol, and the alcohol can be ethanol; the catalyst can be a bifunctional or mixed material with OER and ORR catalytic activity, such as the positive electrode catalyst can be RuO2, Pt / C or a mixture thereof; the conductive agent can be carbon black, etc.; the positive electrode current collector can be carbon paper, etc.

[0113] See the structure of the rust-air battery. Figures 4 to 5 As shown, the rust-air battery includes a positive plate 1, a separator 2, a negative plate 3, a first pad 4, a positive electrode (i.e., an air positive electrode) 5, a negative electrode 6 (i.e., a negative electrode for an air battery, also known as a rust negative electrode), a second pad 7, tabs 8 (which can be nickel tabs, etc.), and an electrolyte inlet / outlet 9.

[0114] See Figure 4 As shown, from the oxygen inlet side to the opposite side, the following components are arranged in sequence: positive electrode plate 1, first gasket 4, tab 8, positive electrode (i.e., air positive electrode) 5, separator 2, negative electrode 6, tab 8, second gasket 7, and negative electrode plate 3. The electrolyte inlet / outlet 9 includes an electrolyte inlet and an electrolyte outlet, which are respectively located on opposite sides of the separator 2. The electrolyte flows through the inlet / outlet into the interior of the rust-air battery to provide a reaction channel, while O2 is simultaneously introduced to the positive electrode. See the schematic diagram after assembly. Figure 5 As shown.

[0115] The above-mentioned solution will be further described below with reference to specific embodiments; it should be understood that these embodiments are used to illustrate the basic principles, main features and advantages of the present invention, and the present invention is not limited to the scope of the following embodiments; the implementation conditions used in the embodiments can be further adjusted according to specific requirements, and the implementation conditions not specified are usually the conditions in conventional experiments.

[0116] Unless otherwise specified in the following examples, all raw materials were commercially available or prepared using conventional methods in the art. In the examples, the ferric oxide particles had a particle size of approximately 100 nm and were purchased from Xi'an Bona Materials Technology Co., Ltd.; the graphene was commercially available with a thickness of approximately 1-10 nm and a sheet diameter of approximately 1-10 μm, purchased from Xiamen Kaina Graphene Technology Co., Ltd.; the carbon nanotubes had a diameter of 10-30 nm and a length of 10-30 μm and were purchased from Chengdu Jiacai Technology; the carbon nanofibers were purchased from Xianfeng Nano, with a diameter of 45-130 nm and a length of 0.5-100 μm, product number 105285; the acetylene black was purchased from Kelude, with a particle size of approximately 35 nm, product number MA-EN-CO-000601; the Ketjen black had a particle size of approximately 34 nm and was purchased from Guangzhou Jingyi New Materials Co., Ltd., model EC600JD; and CMK-3 (ordered mesoporous carbon) was purchased from Xianfeng Nano, product number 100423.

[0117] (Rust Electrode Materials and Their Preparation)

[0118] Example 1-1:

[0119] This example provides a rust electrode material and its preparation method. By mass percentage, the rust electrode material contains 63% rust particles (i.e., ferric oxide particles, the same below), 27% graphene, 5% carbon nanotubes, and 5% acetylene black.

[0120] The preparation method of the rust electrode material includes: first, mechanically mixing 63% rust (Fe2O3) particles and 27% graphene with a high-speed mixer (about 2500 rpm) for 30 min, then adding 5% carbon nanotubes and 5% acetylene black, and continuing to mix for 30 min to obtain the rust electrode material.

[0121] Examples 1-2:

[0122] This example provides a rust electrode material and its preparation method. By mass percentage, the rust electrode material contains 54% rust particles, 36% graphene, 5% carbon nanotubes, and 5% acetylene black.

[0123] The preparation method of the rust electrode material includes: first, mechanically mixing 54% rust (Fe2O3) particles and 36% graphene with a high-speed mixer (about 2500 rpm) for 30 min, then adding 5% carbon nanotubes and 5% acetylene black, and continuing to mix for 30 min to obtain the rust electrode material.

[0124] Examples 1-3:

[0125] This example provides a rust electrode material and its preparation method. By mass percentage, the rust electrode material contains 72% rust particles, 18% graphene, 5% carbon nanotubes, and 5% acetylene black.

[0126] The preparation method of the rust electrode material includes: first, mechanically mixing 72% rust (Fe2O3) particles and 18% graphene with a high-speed mixer (about 2500 rpm) for 30 min, then adding 5% carbon nanotubes and 5% acetylene black, and continuing to mix for 30 min to obtain the rust electrode material.

[0127] Examples 1-4:

[0128] This example provides a rust electrode material and its preparation method. By mass percentage, the rust electrode material contains 63% rust particles, 27% graphene, 7% carbon nanotubes, and 3% acetylene black.

[0129] The preparation method of the rust electrode material includes: first, mechanically mixing 63% rust (Fe2O3) particles and 27% graphene with a high-speed mixer (about 2500 rpm) for 30 min, then adding 7% carbon nanotubes and 3% acetylene black, and continuing to mix for 30 min to obtain the rust electrode material.

[0130] Examples 1-5:

[0131] This example provides a rust electrode material and its preparation method. By mass percentage, the rust electrode material contains 63% rust particles, 27% graphene, 3% carbon nanotubes, and 7% acetylene black.

[0132] The preparation method of the rust electrode material includes: first, mechanically mixing 63% rust (Fe2O3) particles and 27% graphene with a high-speed mixer (about 2500 rpm) for 30 min, then adding 3% carbon nanotubes and 7% acetylene black, and continuing to mix for 30 min to obtain the rust electrode material.

[0133] Examples 1-6:

[0134] This example provides a granular rust electrode material and its preparation method. By mass percentage, the granular rust electrode material contains 63% rust particles, 27% graphene, 5% carbon nanotubes, and 5% acetylene black.

[0135] The preparation method of the granular rust electrode material includes: mixing rust particles, graphene, carbon nanotubes and acetylene black in the above proportions, adding a mixed solution of water and ethanol (volume ratio of water to ethanol is 9:1), stirring until a stable slurry is formed (solid content is about 8 wt.%), and then pouring it into a spray dryer, setting the inlet temperature to 200℃ and the outlet temperature to 100℃ to obtain the granular rust electrode material.

[0136] Examples 1-7:

[0137] This example provides a rust electrode material and its preparation method. By mass percentage, the rust electrode material contains 63% rust particles, 27% graphene, 5% carbon nanofibers, and 5% Ketjen Black.

[0138] The preparation method of the rust electrode material includes: first, mechanically mixing 63% rust (Fe2O3) particles and 27% carbon nanosheets with a high-speed mixer (about 2500 rpm) for 30 min, then adding 5% carbon nanofibers and 5% Ketjen black, and continuing to mix for 30 min to obtain the rust electrode material.

[0139] Comparative Example 1-1:

[0140] This example provides a rust electrode material and its preparation method, which is basically the same as Example 1-1, except that: carbon nanotubes and acetylene black are not added, and the amount of graphene added is adjusted to 37%.

[0141] Comparative Examples 1-2:

[0142] This example provides a rust electrode material and its preparation method, which is basically the same as in Example 1-1, except that: no graphene is added, the mass content of carbon nanotubes is adjusted to 18.5%, and the mass content of acetylene black is adjusted to 18.5%.

[0143] Comparative Examples 1-3:

[0144] This example provides a rust electrode material and its preparation method, which is basically the same as in Example 1-1, except that the amount of graphene added is 5%, the amount of carbon nanotubes added is 20%, and the amount of acetylene black added is 12%.

[0145] Comparative Examples 1-4:

[0146] This example provides a rust electrode material and its preparation method, which is basically the same as in Example 1-1, except that: by mass percentage, the rust electrode material contains: 90% rust particles, 2.5% graphene, 2.5% carbon nanotubes, 2.5% acetylene black, and 2.5% CMK-3 (ordered mesoporous carbon).

[0147] The preparation method of the rust electrode material includes: first, mechanically mixing 90% rust (Fe2O3) particles and 2.5% graphene with a high-speed mixer (about 2500 rpm) for 30 min; then adding 2.5% carbon nanotubes, 2.5% acetylene black and 2.5% CMK-3 (ordered mesoporous carbon), and continuing to mix for 30 min to obtain the rust electrode material.

[0148] Comparative Examples 1-5:

[0149] This example provides a rust electrode material and its preparation method, which is basically the same as in Example 1-1, except that the ferric oxide particles are replaced with ferric oxide particles of the same amount and particle size.

[0150] (Composite material for preparing negative electrodes for air batteries and its preparation)

[0151] Example 2-1:

[0152] This example provides a composite material for preparing a negative electrode for an air battery and a method for preparing the same. By mass percentage, the composite material contains 95% of the rust electrode material obtained in Example 1-1 and 5% of PTFE (polytetrafluoroethylene).

[0153] The composite material was prepared by mixing rust electrode material and binder in a high-speed mixer (mixing speed of 3000 rpm) for 15 minutes.

[0154] Example 2-2:

[0155] This example provides a composite material for preparing a negative electrode for an air battery and its preparation method, which is basically the same as Example 2-1, except that the rust electrode material obtained in Example 1-1 is replaced with the rust electrode material prepared in Example 1-2.

[0156] Examples 2-3:

[0157] This example provides a composite material for preparing a negative electrode for an air battery and its preparation method, which is basically the same as Example 2-1, except that the rust electrode material obtained in Example 1-1 is replaced with the rust electrode material prepared in Example 1-3.

[0158] Examples 2-4:

[0159] This example provides a composite material for preparing a negative electrode for an air battery and its preparation method, which is basically the same as Example 2-1, except that the rust electrode material obtained in Example 1-1 is replaced with the rust electrode material prepared in Example 1-4.

[0160] Examples 2-5:

[0161] This example provides a composite material for preparing a negative electrode for an air battery and its preparation method, which is basically the same as Example 2-1, except that the rust electrode material obtained in Example 1-1 is replaced with the rust electrode material prepared in Example 1-5.

[0162] Examples 2-6:

[0163] This example provides a composite material for preparing a negative electrode for an air battery and its preparation method, which is basically the same as Example 2-1, except that the rust electrode material obtained in Example 1-1 is replaced with the rust electrode material prepared in Example 1-6.

[0164] Examples 2-7:

[0165] This example provides a composite material for preparing a negative electrode for an air battery and its preparation method, which is basically the same as Example 2-1, except that the rust electrode material obtained in Example 1-1 is replaced with the rust electrode material prepared in Example 1-7.

[0166] Comparative Example 2-1:

[0167] This example provides a composite material for preparing a negative electrode for an air battery and its preparation method, which is basically the same as Example 2-1, except that the rust electrode material obtained in Example 1-1 is replaced with the rust electrode material prepared in Comparative Example 1-1.

[0168] Comparative Example 2-2:

[0169] This example provides a composite material for preparing a negative electrode for an air battery and its preparation method, which is basically the same as Example 2-1, except that the rust electrode material obtained in Example 1-1 is replaced with the rust electrode material prepared in Comparative Example 1-2.

[0170] Comparative Examples 2-3:

[0171] This example provides a composite material for preparing a negative electrode for an air battery and its preparation method, which is basically the same as Example 2-1, except that the rust electrode material obtained in Example 1-1 is replaced with the rust electrode material prepared in Comparative Examples 1-3.

[0172] Comparative Examples 2-4:

[0173] This example provides a composite material for preparing a negative electrode for an air battery and its preparation method, which is basically the same as Example 2-1, except that the rust electrode material obtained in Example 1-1 is replaced with the rust electrode material prepared in Comparative Examples 1-4.

[0174] Comparative Examples 2-5:

[0175] This example provides a composite material for preparing a negative electrode for an air battery and its preparation method, which is basically the same as Example 2-1, except that the rust electrode material obtained in Example 1-1 is replaced with the rust electrode material prepared in Comparative Examples 1-5.

[0176] (Negative electrode for air batteries and its preparation)

[0177] Example 3-1:

[0178] This example provides a negative electrode for an air battery and its preparation method. The negative electrode comprises a stainless steel mesh (200 mesh, approximately 120 μm thick, the same applies below) and a composite material obtained in Example 2-1 loaded on the stainless steel mesh. The specific preparation process is as follows: First, the stainless steel mesh is placed in a mold, then the composite material obtained in Example 2-1 is placed on the stainless steel mesh, and then pressed and formed using a press (the pressure is 10 MPa) to produce a negative electrode for an air battery (also known as a rust negative electrode) with a thickness of approximately 1800 μm. Figure 6 The SEM image of the negative electrode of this air battery shows a clear interconnected skeleton structure.

[0179] Example 3-2:

[0180] This example provides a negative electrode for an air battery and its preparation method, which is basically the same as Example 3-1, except that the composite material obtained in Example 2-1 is replaced with the composite material prepared in Example 2-2.

[0181] Example 3-3:

[0182] This example provides a negative electrode for an air battery and its preparation method, which is basically the same as Example 3-1, except that the composite material obtained in Example 2-1 is replaced with the composite material prepared in Example 2-3.

[0183] Examples 3-4:

[0184] This example provides a negative electrode for an air battery and its preparation method, which is basically the same as Example 3-1, except that the composite material obtained in Example 2-1 is replaced with the composite material prepared in Example 2-4.

[0185] Examples 3-5:

[0186] This example provides a negative electrode for an air battery and its preparation method, which is basically the same as Example 3-1, except that the composite material obtained in Example 2-1 is replaced with the composite material prepared in Example 2-5.

[0187] Examples 3-6:

[0188] This example provides a negative electrode for an air battery and its preparation method, which is basically the same as Example 3-1, except that the composite material obtained in Example 2-1 is replaced with the composite material prepared in Example 2-6.

[0189] Examples 3-7:

[0190] This example provides a negative electrode for an air battery and its preparation method, which is basically the same as Example 3-1, except that the composite material obtained in Example 2-1 is replaced with the composite material prepared in Example 2-7.

[0191] Comparative Example 3-1:

[0192] This example provides a negative electrode for an air battery and its preparation method, which is basically the same as Example 3-1, except that the composite material obtained in Example 2-1 is replaced with the composite material prepared in Comparative Example 2-1.

[0193] Comparative Example 3-2:

[0194] This example provides a negative electrode for an air battery and its preparation method, which is basically the same as Example 3-1, except that the composite material obtained in Example 2-1 is replaced with the composite material prepared in Comparative Example 2-2.

[0195] Comparative Example 3-3:

[0196] This example provides a negative electrode for an air battery and its preparation method, which is basically the same as Example 3-1, except that the composite material obtained in Example 2-1 is replaced with the composite material prepared in Comparative Example 2-3.

[0197] Comparative Examples 3-4:

[0198] This example provides a negative electrode for an air battery and its preparation method, which is basically the same as Example 3-1, except that the composite material obtained in Example 2-1 is replaced with the composite material prepared in Comparative Example 2-4.

[0199] Comparative Examples 3-5:

[0200] This example provides a negative electrode for an air battery and its preparation method, which is basically the same as Example 3-1, except that the composite material obtained in Example 2-1 is replaced with the composite material prepared in Comparative Example 2-5.

[0201] Performance Test 1:

[0202] The conductivity and porosity of the negative electrodes used in the air batteries obtained in Examples 3-1 to 3-7 and Comparative Examples 3-1 to 3-5 were tested, and the specific results are shown in Table 1. Conductivity was tested using the four-probe method. The specific steps were as follows: the electrode was cut into a regular rectangle (1 cm × 2 cm); the surface was ensured to be flat, avoiding edge bending; a constant current was applied using a four-probe instrument (probe spacing 1 mm), and the voltage was measured; the conductivity was calculated using the conductivity formula. Porosity was tested using the BET (Boiler-Effect Transformation) method.

[0203] Table 1

[0204]

[0205] (Rust-air battery and its preparation)

[0206] Example 4-1:

[0207] This example provides a rust-air battery, which includes a negative electrode, an air positive electrode, and an electrolyte. The negative electrode is the negative electrode for air batteries obtained in Example 3-1.

[0208] The air cathode was prepared as follows: 0.5 mL of deionized water, 0.5 mL of ethanol, 50 μL of Nafion solution (DuPont, USA, Nafion solution DUPONT 5% D520 perfluorosulfonic acid naphthol membrane solution), 3 mg of Pt-Ru / C catalyst (platinum-ruthenium carbon black 40%Pt-20%Ru / C, purchased from Shaanxi Kaida Chemical Co., Ltd.) and 2 mg of carbon black (particle size approximately 30-60 nm, Vulcan XC-72, purchased from the Scientific Materials Station) were mixed and ultrasonicated for 60 min to obtain a cathode slurry. An appropriate amount of cathode slurry was dropped onto carbon paper (thickness 0.3 mm) and dried at room temperature to obtain an air cathode with a thickness of 0.36 mm.

[0209] The electrolyte is an aqueous solution of potassium hydroxide with a concentration of 6 mol / L.

[0210] according to Figures 4 to 5 The structure shown is installed as a rust-air battery.

[0211] Example 4-2:

[0212] This example provides a rust-air battery, which is basically the same as Example 4-1, except that the negative electrode is the negative electrode for air batteries obtained in Example 3-2.

[0213] Example 4-3:

[0214] This example provides a rust-air battery, which is basically the same as Example 4-1, except that the negative electrode is the negative electrode for air batteries obtained in Example 3-3.

[0215] Example 4-4:

[0216] This example provides a rust-air battery, which is basically the same as Example 4-1, except that the negative electrode is the negative electrode for air batteries obtained in Example 3-4.

[0217] Examples 4-5:

[0218] This example provides a rust-air battery, which is basically the same as Example 4-1, except that the negative electrode is the negative electrode for air batteries obtained in Example 3-5.

[0219] Examples 4-6:

[0220] This example provides a rust-air battery, which is basically the same as Example 4-1, except that the negative electrode is the negative electrode for air batteries obtained in Example 3-6.

[0221] Examples 4-7:

[0222] This example provides a rust-air battery, which is basically the same as Example 4-1, except that the negative electrode is the negative electrode for air batteries obtained in Example 3-7.

[0223] Comparative Example 4-1:

[0224] This example provides a rust-air battery, which is basically the same as Example 4-1, except that the negative electrode is the same as the negative electrode for air batteries obtained in Comparative Example 3-1.

[0225] Comparative Example 4-2:

[0226] This example provides a rust-air battery, which is basically the same as Example 4-1, except that the negative electrode is the negative electrode used in the air battery obtained in Comparative Example 3-2.

[0227] Comparative Example 4-3:

[0228] This example provides a rust-air battery, which is basically the same as Example 4-1, except that the negative electrode is the negative electrode used in the air battery obtained in Comparative Example 3-3.

[0229] Comparative Example 4-4:

[0230] This example provides a rust-air battery, which is basically the same as Example 4-1, except that the negative electrode is the same as the negative electrode for air batteries obtained in Comparative Example 3-4.

[0231] Comparative Examples 4-5:

[0232] This example provides a rust-air battery, which is basically the same as Example 4-1, except that the negative electrode is the negative electrode used in the air battery obtained in Comparative Example 3-5.

[0233] Performance Test 2:

[0234] Charge-discharge experiments were conducted on the rust-air batteries obtained in Examples 4-1 to 4-7 and Comparative Examples 4-1 to 4-5, wherein: the charge-discharge rate was 0.1C; the test temperature was 25℃, room temperature; the relevant procedures for the charge-discharge experiment were as follows: the voltage test range was 0.1-2V. After assembling the battery, it was first left to stand for 10 hours, then charged at a current of 0.1C for 10 hours with a cutoff voltage of 2V, then left to stand for 5 minutes, then discharged at a current of 0.1C with a cutoff voltage of 0.1V, then left to stand for 5 minutes before charging again. This charge-discharge cycle was repeated. The test results are shown in Table 2.

[0235] Table 2

[0236]

[0237] Note: The battery system of this invention differs from lithium-ion batteries and other battery systems. It has a structural reorganization process in the early stage, which is reflected in the battery performance as an activation process in the first few cycles, with a relatively low initial capacity. At the same time, since the first few cycles are an activation process, especially the first cycle, it cannot reflect the overall performance of the battery. Therefore, the capacity retention rate mentioned above in this invention is the discharge capacity of the 40th cycle divided by the discharge capacity of the 5th cycle, which reflects the overall performance of the battery.

[0238] Also see Figure 7 As shown, it is the discharge curve of the rust-air battery prepared in Example 4-1 of the present invention after 40 cycles. It can be seen that the discharge voltage is relatively stable overall, with discharge plateaus appearing at about 0.8V and 0.6V, corresponding to the two-electron and one-electron conversion process of iron. The discharge capacity is close to 500mAh / g, which indicates that the battery has a large specific capacity and a good electron / ion conduction network.

[0239] See Figure 8 As shown, it is a cycle performance test diagram of the rust-air battery obtained in Example 4-1, Comparative Examples 4-1 to 4-5 of the present invention. It can be seen that Example 4-1 of the present invention has excellent cycle retention, indicating that the specific rust electrode material of the present invention can improve cycle stability.

[0240] The cycling performance of Comparative Example 4-1 deteriorated significantly, indicating that using only graphene as a conductive component in the rust electrode material cannot construct a stable framework structure, and cannot effectively confine the active components in space or achieve maximum deposition and loading.

[0241] Comparative Example 4-2 did not complete 40 cycles, resulting in significant capacity decay. Figure 8As shown, the capacity retention rate was only 68% after 22 cycles; this indicates that without the addition of graphene, only carbon nanotubes and acetylene black were added to the rust electrode material, which could not form an effective framework structure and had poor stability.

[0242] The cycling performance of Comparative Examples 4-3 deteriorated significantly. Similarly, when the amount of graphene added to the rust electrode material is very small, although a framework structure may be formed locally, it cannot provide support for the active components in all areas, and thus cannot achieve good cycling performance during continuous cycling.

[0243] The cycling performance of Comparative Example 4-4 deteriorated significantly, indicating that when the amount of graphene in the rust electrode material is extremely low and large-sized mesoporous carbon materials are added, although there are enough active ingredients, it is impossible to construct a sufficient and stable interconnect framework structure, and it is impossible to provide effective support and confinement for a large number of active ingredients.

[0244] Comparative examples 4-5 did not complete 40 cycles. Figure 8 As shown, its capacity retention rate after 27 cycles is lower than that of Example 4-1 after 27 cycles, and the overall capacity is much lower than that of Example 4-1. This indicates that, under the system of the present invention, the effect of ferric oxide is worse than that of ferric oxide.

[0245] As used throughout the specification and claims, the term "comprising" is an open-ended term and should be interpreted as "comprising but not limited to." "Substantially" means that within an acceptable margin of error, those skilled in the art can solve the technical problem and substantially achieve the technical effect. It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a product or system comprising a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a product or system. Without further limitations, an element defined by the phrase "comprising one" does not exclude the presence of other identical elements in the product or system comprising said element.

[0246] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

[0247] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

Claims

1. A rust-resistant electrode material, characterized in that, The rust electrode material is a mixture obtained by uniformly mixing ferric oxide, zero-dimensional conductive material, one-dimensional conductive material and two-dimensional conductive material. In the rust electrode material, by mass percentage, the ferric oxide accounts for 50%-75%, the two-dimensional conductive material accounts for 10%-40%, and the amount of the two-dimensional conductive material added is more than 1.5 times the amount of either the zero-dimensional conductive material or the one-dimensional conductive material added. The mass ratio of the zero-dimensional conductive material, the one-dimensional conductive material and the two-dimensional conductive material is 1:0.1-10:1.5-40.

2. The rust-resistant electrode material according to claim 1, characterized in that, In the rust electrode material, the two-dimensional conductive material forms the basic framework, the zero-dimensional conductive material and the one-dimensional conductive material respectively form the epitaxial framework, the basic framework and the epitaxial framework together constitute the interconnect framework, and the ferric oxide is distributed in the interconnect framework.

3. The rust-resistant electrode material according to claim 2, characterized in that, The interconnect skeleton includes multiple conductive paths, and each conductive path contains the zero-dimensional conductive material, the one-dimensional conductive material, and the two-dimensional conductive material.

4. The rust-resistant electrode material according to claim 1, characterized in that, The ferric oxide, the zero-dimensional conductive material, and the one-dimensional conductive material are all loaded on the two-dimensional conductive material; and / or, the amount of the two-dimensional conductive material added is 1.5-15 times the amount of either the zero-dimensional conductive material or the one-dimensional conductive material added.

5. The rust-resistant electrode material according to claim 1, characterized in that, The zero-dimensional conductive material, the one-dimensional conductive material, and the two-dimensional conductive material are all conductive carbon materials.

6. The rust-resistant electrode material according to claim 5, characterized in that, The two-dimensional conductive material includes graphene and / or carbon nanosheets; and / or, the one-dimensional conductive material includes carbon nanofibers and / or carbon nanotubes; and / or, the zero-dimensional conductive material includes acetylene black particles.

7. The rust-resistant electrode material according to claim 1, characterized in that, The thickness of the two-dimensional conductive material is 1-300 nm, and the sheet diameter is 0.5-20 μm; and / or, the aspect ratio of the one-dimensional conductive material is 100-3000; and / or, the particle size of the zero-dimensional conductive material is 10-500 nm; and / or, the one-dimensional conductive material includes single-walled carbon nanotubes and / or multi-walled carbon nanotubes.

8. The rust-resistant electrode material according to claim 1, characterized in that, The ferric oxide exists in the form of ferric oxide particles, and the particle size of the ferric oxide particles is 10-1000 nm.

9. The rust-resistant electrode material according to claim 1, characterized in that, In the rust electrode material, the mass ratio of the zero-dimensional conductive material, the one-dimensional conductive material, and the two-dimensional conductive material is 1:0.2-2.8:3-15.

10. The rust-resistant electrode material according to any one of claims 1-9, characterized in that, By mass percentage, the two-dimensional conductive material accounts for 15%-40% of the rust electrode material, the one-dimensional conductive material accounts for 1%-10% of the rust electrode material, and the zero-dimensional conductive material accounts for 1%-10% of the rust electrode material.

11. The rust-resistant electrode material according to claim 10, characterized in that, Based on mass percentage, the total content of the one-dimensional conductive material and the zero-dimensional conductive material in the rust electrode material is 5%-15%; and / or, the mass ratio of the zero-dimensional conductive material, the one-dimensional conductive material and the two-dimensional conductive material is 1:0.4-2.5:3.5-9.

12. A method for preparing a rust electrode material according to any one of claims 1-11, characterized in that, The preparation method includes: mixing ferric oxide, zero-dimensional conductive material, one-dimensional conductive material and two-dimensional conductive material.

13. The method for preparing the rust electrode material according to claim 12, characterized in that, The mixing and homogenization are carried out using a dry mixing method.

14. The method for preparing the rust electrode material according to claim 12 or 13, characterized in that, The method for preparing the rust electrode material includes: first, mixing and stirring ferric oxide and a two-dimensional conductive material under solvent-free conditions to obtain an intermediate; then, adding a zero-dimensional conductive material and a one-dimensional conductive material to the intermediate and continuing to mix and stir.

15. A composite material for preparing a negative electrode for an air battery, characterized in that, The composite material comprises the rust electrode material as described in any one of claims 1-11 and a binder.

16. The composite material for preparing a negative electrode for an air battery according to claim 15, characterized in that, The binder includes polytetrafluoroethylene; and / or, by mass percentage, the amount of the binder added to the composite material is 1%-10% of the amount of the rust electrode material added; and / or, the composite material is prepared by mixing the rust electrode material and the binder.

17. The composite material for preparing a negative electrode for an air battery according to claim 15, characterized in that, The rust electrode material is granular.

18. The composite material for preparing a negative electrode for an air battery according to claim 17, characterized in that, The granular rust electrode material is prepared by the following method: ferric oxide, zero-dimensional conductive material, one-dimensional conductive material and two-dimensional conductive material are granulated to form granular rust electrode material.

19. The composite material for preparing a negative electrode for an air battery according to claim 18, characterized in that, The granulation method includes spray granulation; and / or, the granular rust electrode material includes a spherical state.

20. A negative electrode for an air battery, characterized in that, The negative electrode comprises a composite material for preparing a negative electrode for an air battery as described in any one of claims 15-19 and a current collector, wherein the composite material is loaded on the current collector.

21. The negative electrode for an air battery according to claim 20, characterized in that, The current collector is a stainless steel mesh; and / or, the thickness of the current collector is 5-20 μm; and / or, the thickness of the negative electrode is 500 μm-10 mm.

22. A method for preparing a negative electrode for an air battery according to claim 20 or 21, characterized in that, The preparation method includes: placing the composite material on the current collector and pressing it into shape.

23. The method for preparing a negative electrode for an air battery according to claim 22, characterized in that, The pressure used in the pressure molding is 5-20 MPa; and / or, before the pressure molding, the composite material is treated by rolling, grinding or shearing to cause the binder to become fibrous.

24. A negative electrode for an air battery, characterized in that, The negative electrode comprises a current collector and a composite material loaded on the current collector. The composite material comprises a rust electrode material and a binder. The rust electrode material is a mixture obtained by uniformly mixing ferric oxide, a zero-dimensional conductive material, a one-dimensional conductive material, and a two-dimensional conductive material. The conductivity of the negative electrode is 1-10 S / cm, and the porosity is 40%-65%. In the rust electrode material, by mass percentage, the ferric oxide accounts for 50%-75%, the two-dimensional conductive material accounts for 10%-40%, and the amount of the two-dimensional conductive material added is more than 1.5 times the amount of either the zero-dimensional conductive material or the one-dimensional conductive material added. The mass ratio of the zero-dimensional conductive material, the one-dimensional conductive material and the two-dimensional conductive material is 1:0.1-10:1.5-40.

25. A rust-air battery, characterized in that, The rust-air battery includes a negative electrode, an air positive electrode, and an electrolyte. The negative electrode is an air battery negative electrode as described in any one of claims 20-21 and 24, or an air battery negative electrode prepared by the method described in claim 22 or 23.

26. The rust-air battery according to claim 25, characterized in that, During the initial charge, the reactions at the negative and positive electrodes are as follows: Negative electrode reaction: Fe2O3 + 3H2O + 2e - →2Fe(OH)2+2OH - Fe(OH)2+2e - →Fe+2OH - ; Positive electrode reaction: 4OH - →O2 + 2H2O + 4e - .

27. The rust-air battery according to claim 25, characterized in that, The rust-air battery has an initial discharge specific capacity of 400-500 mAh / g at a charge / discharge rate of 0.1C, a discharge specific capacity of 550-650 mAh / g at the fifth cycle, and a capacity retention rate of 77%-90% after 40 cycles.

28. A method for energy storage using a rust-air battery according to any one of claims 25-27, characterized in that, There is no need to discharge the rust-air battery first; it can be used directly for charging and energy storage.

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