An electrode material, its preparation method and application

Abstract

This invention discloses an electrode material, its preparation method, and its application. The electrode material uses porous rust, i.e., ferric oxide with a porous structure, as the core active material and loads it onto a two-dimensional conductive material with a sheet-like structure. The electrode material is further made into particles, thus making the electrode material as a whole present as a particle with a porous structure. When the negative electrode made from this special electrode material is used in an air battery, it not only has excellent specific capacity and cycle stability, but can also be directly charged after assembly, with fast response and active scheduling capabilities. When applied to large-scale energy storage, it can directly start the charging process in an uncharged state without pre-activation or initial discharge, which is suitable for the "on-demand charging and fast response" requirements of wind and solar energy storage systems and has good system coupling.

Description

Technical Field

[0001] This invention relates to the field of air batteries, specifically to an 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, the extraction technology is relatively simple, and the 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 pre-activation or initial discharge pretreatment is required before charging can be carried out, which is not conducive to on-site deployment for sudden demand; (2) Poor mechanical stability, which makes them easy to fall off and pulverize during charging and discharging; (3) Poor conductivity, which requires the use of a large amount of conductive agent. However, once the amount of conductive agent is increased too much, the amount of active material added will inevitably be insufficient. Therefore, the conductivity is low and the electron transport impedance is large. At the same time, the utilization rate of active material is low, which makes the battery performance unsatisfactory.

[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 electrode material with outstanding performance.

[0006] The present invention also provides a negative electrode for an air battery containing electrode materials 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] An electrode material comprising a two-dimensional conductive material and ferric oxide loaded on the two-dimensional conductive material, wherein the ferric oxide has a porous structure and the electrode material is granular.

[0009] In some embodiments of the present invention, the two-dimensional conductive material is a conductive carbon material.

[0010] According to some specific aspects of the present invention, the two-dimensional conductive material may include, but is not limited to, graphene.

[0011] 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.

[0012] According to some preferred aspects of the present invention, the ferric oxide exists in the form of ferric oxide particles, and further, the particle size of the ferric oxide particles is 2-1000 nm.

[0013] In some embodiments of the present invention, the porosity of the ferric oxide is 20%-50%.

[0014] In some embodiments of the present invention, the specific surface area of ​​the ferric oxide is greater than or equal to 10 m². 2 / g. Further, the specific surface area of ​​the ferric oxide is 10-200 m² / g. 2 / g. Furthermore, the specific surface area of ​​the ferric oxide is 10-50 m² / g. 2 / g.

[0015] In some embodiments of the present invention, the mass ratio of the ferric oxide to the two-dimensional conductive material is 1.5-4:1.

[0016] According to some preferred aspects of the invention, the electrode material further comprises a first zero-dimensional conductive material.

[0017] Furthermore, the first zero-dimensional conductive material is a conductive carbon material.

[0018] Furthermore, in some embodiments of the present invention, the first zero-dimensional conductive material may include, but is not limited to, conductive carbon black particles.

[0019] According to some preferred aspects of the present invention, the added mass of the first zero-dimensional conductive material accounts for 2%-10% of the total mass of the two-dimensional conductive material and the ferric oxide, by mass percentage.

[0020] In some embodiments of the present invention, the particle size of the first zero-dimensional conductive material is 10-300 nm.

[0021] In some embodiments of the present invention, the first zero-dimensional conductive material is loaded onto the two-dimensional conductive material.

[0022] According to some specific aspects of the present invention, the electrode material has a spherical particle structure.

[0023] In some embodiments of the present invention, the particle size of the electrode material is 1-100 μm. Further, the particle size of the electrode material is 10-50 μm.

[0024] In some embodiments of the present invention, the electrode material is prepared by mixing and granulating raw materials comprising a two-dimensional conductive material and ferric oxide having a porous structure.

[0025] Another technical solution provided by the present invention: a method for preparing the electrode material described above, the preparation method comprising:

[0026] A slurry is prepared by dispersing a two-dimensional conductive material and ferric oxide with a porous structure in a first solvent.

[0027] A first zero-dimensional conductive material is selectively added to the slurry and dispersed evenly.

[0028] Granulation is carried out.

[0029] In some embodiments of the present invention, the first solvent is water and / or an alcohol. Further, the alcohol may include, but is not limited to, ethanol.

[0030] In some embodiments of the present invention, the solid content of the slurry is 3%-20%. Further, the solid content of the slurry is 7%-10%.

[0031] In some embodiments of the present invention, the granulation method includes spray granulation. Further, the spray granulation is performed using a spray dryer.

[0032] Another technical solution provided by the present invention: an electrode material, wherein the electrode material is prepared by mixing and granulating raw materials comprising two-dimensional conductive carbon material, ferric oxide with a porous structure and zero-dimensional conductive carbon material; wherein the mass ratio of the two-dimensional conductive carbon material to the ferric oxide with a porous structure is 1.5-4:1, and the mass percentage of the zero-dimensional conductive carbon material is 2%-10% of the total mass of the two-dimensional conductive material and the ferric oxide with a porous structure.

[0033] 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 electrode material, the second zero-dimensional conductive material and the binder described above.

[0034] In some embodiments of the present invention, the mass ratio of the electrode material, the second zero-dimensional conductive material and the binder is 8-10:0.5-2:1.

[0035] According to some specific aspects of the present invention, the mass ratio of the electrode material, the second zero-dimensional conductive material and the binder is 8-10:0.8-1.2:1.

[0036] In some embodiments of the present invention, the second zero-dimensional conductive material may include, but is not limited to, conductive carbon materials. Further, the second zero-dimensional conductive material may include, but is not limited to, acetylene black and / or conductive carbon black.

[0037] 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.

[0038] In some embodiments of the present invention, the particle size of the second zero-dimensional conductive material is 10-300 nm.

[0039] In some embodiments of the present invention, the composite material is prepared by mixing and homogenizing the electrode material, the second zero-dimensional conductive material, and the binder.

[0040] Another technical solution provided by the present invention: a negative electrode for an air battery, wherein the negative electrode comprises the aforementioned composite material and current collector.

[0041] In some embodiments of the present invention, the current collector may include, but is not limited to, a stainless steel mesh.

[0042] In some embodiments of the present invention, the thickness of the current collector is 50-200 μm.

[0043] In some embodiments of the present invention, the thickness of the negative electrode is 500 μm-10 mm.

[0044] 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 a current collector to form a negative electrode.

[0045] According to some specific aspects of the present invention, a method for preparing the negative electrode for an air battery includes:

[0046] The composite material is processed by rolling, grinding or shearing to cause the binder to become fibrous, resulting in a pretreated composite material. The pretreated composite material is then pressed onto the current collector to form a negative electrode sheet for an air battery.

[0047] In some embodiments of the present invention, the pressing pressure is 6-10 MPa.

[0048] In some embodiments of the present invention, the pressing method further includes hot pressing.

[0049] In some embodiments of the present invention, during the preparation of the negative electrode for the air battery, a current collector is first placed in a mold, then a pretreated composite material is placed on the current collector, and pressure is applied using a press to form the negative electrode for the air battery.

[0050] Another technical solution provided by the present invention: a negative electrode for an air battery, the negative electrode comprising a current collector, a particulate electrode material, conductive particles, and a binder, the electrode material comprising graphene, ferric oxide particles loaded on the graphene and having a porous structure, and a zero-dimensional conductive carbon material, the negative electrode having a conductivity of 1-10 S / cm and a porosity of 35%-55%.

[0051] In some embodiments of the present invention, the conductive particles and the zero-dimensional conductive carbon material can be the same conductive carbon particles or different particles, such as acetylene black particles, Ketjen black particles, conductive carbon black particles, etc., which can be selected independently.

[0052] 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.

[0053] According to certain aspects of the present invention, the reactions of the negative and positive electrodes during the initial charging are as follows:

[0054] Negative electrode reaction: Fe2O3 + 3H2O + 2e - →2Fe(OH)2+2OH - Fe(OH)2+2e - →Fe+2OH - ;

[0055] Positive electrode reaction: 4OH - →O2 + 2H2O + 4e - .

[0056] According to the present invention, the rust-air battery has an initial coulombic efficiency of 56%-70% and an initial discharge specific capacity of 390-500 mAh / g at a charge-discharge rate of 0.1C, and a capacity retention rate of 70%-95% after 30 cycles.

[0057] 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.

[0058] 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.

[0059] In this invention, by mixing ferric oxide and a two-dimensional conductive material, ferric oxide can be loaded onto the two-dimensional conductive material. At the same time, the two-dimensional conductive material has a sheet-like structure with a large planar size. If other conductive materials, such as the aforementioned first zero-dimensional conductive material, are added, the first zero-dimensional conductive material can also be easily loaded or deposited on the surface of the two-dimensional conductive material or other load-bearing parts.

[0060] In this invention, the terms "first" and "second" in the names of "first zero-dimensional conductive material," "second zero-dimensional conductive material," "first solvent," and "second solvent" do not have a sequential order. They are merely used to distinguish materials used in different components or at different stages, and to avoid confusion or misunderstanding caused by identical names.

[0061] In this invention, the terms "zero-dimensional" and "two-dimensional" in the zero-dimensional conductive material and two-dimensional conductive material mentioned can be understood in their usual sense, for example, as follows:

[0062] Zero-dimensional (0D) materials typically refer to materials where all three dimensions are approximately the same, with no significant aspect ratio. Their dimensions are relatively similar in all directions, 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 particles, conductive carbon black particles, and oxide particles. Their dimensions in the three dimensions can be on the nanometer or micrometer scale. 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] Due to the application of the above-described technical solution, the present invention has at least the following advantages compared with the prior art:

[0067] Based on the problems existing in the use of air batteries, such as the need for pretreatment after assembly, poor mechanical stability of iron electrode sheets, high electronic transmission impedance, 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.

[0068] This energy storage unit employs the electrode material with outstanding performance proposed in this invention. This electrode material uses porous rust (ferric oxide with a porous structure) as the core active material, which is loaded onto a two-dimensional conductive material exhibiting a sheet-like structure. Furthermore, the electrode material is made into granules, thus effectively making the entire electrode material present as a porous granular form.

[0069] First, this structural form is similar to two-dimensional conductive materials coating or confining porous iron oxide, which can improve structural stability and prevent it from falling off or pulverizing during charging and discharging.

[0070] Secondly, making the electrode material present as well-dispersed particles is beneficial for preparing a tightly bonded negative electrode after mixing it with other conductive agents and binders. At the same time, this negative electrode has a rich pore structure due to the presence of porous rust. That is, although the material components form a dense and compact electrode, the pore structure on the porous rust can provide a high contact area between the electrode and the electrolyte, shorten the ion diffusion path, and expose more reactive sites, which helps to improve the electrochemical reaction rate and specific capacity. The pore structure can also provide a buffer for the volume expansion of the material during charging and discharging, enhancing cycle stability.

[0071] Third, it is easy to control the particle size distribution of granular electrode materials, which is beneficial for preparing uniform electrodes, improving batch-to-batch quality stability, and making it suitable for large-scale production.

[0072] Fourth, by pre-processing porous rust and two-dimensional conductive materials into granular electrode materials, the rust and two-dimensional conductive materials can have better contact. At the same time, it is beneficial to uniformly disperse them in the negative electrode slurry when preparing the negative electrode. In this way, a multi-dimensional conductive path can be constructed in the negative electrode system using only two-dimensional conductive materials. Moreover, the two-dimensional conductive materials are always in contact with the active material, namely porous rust, which greatly improves the electron transport efficiency, conductivity, and utilization rate of active materials.

[0073] In summary, the negative electrode made using the electrode material of this invention and used in an air battery not only possesses excellent electrical performance such as specific capacity and cycle stability, but also can be directly charged after assembly, exhibiting rapid response and active scheduling capabilities. When applied to large-scale energy storage, it can directly initiate the charging process in an uncharged state without the need for pre-activation or initial discharge, making it suitable for the "charge as you generate, rapid response" requirements of wind and solar energy storage systems, and exhibiting good system coupling. Attached Figure Description

[0074] Figure 1 A schematic diagram showing the distribution of each material in the composite negative electrode material in this embodiment of the invention;

[0075] Figure 2 A schematic diagram of the structure of the negative electrode for an air battery in an embodiment of the present invention;

[0076] Figure 3 A schematic diagram of the structure of the air positive electrode in an embodiment of the present invention;

[0077] Figure 4 This is a schematic diagram of the explosion of the rust-air battery in an embodiment of the present invention;

[0078] Figure 5 This is a schematic diagram of the rust-air battery after assembly in an embodiment of the present invention;

[0079] Figure 6 These are scanning electron microscope (SEM) images of the electrode materials prepared in Examples 1-3 of this invention;

[0080] Figure 7 The graphs show the cycle performance test results of the rust-air batteries obtained in Examples 4-3 and Comparative Examples 4-1 to 4-4 of this invention. Detailed Implementation

[0081] Based on in-depth research and extensive experiments, the inventors of this invention proposed a novel energy storage mechanism that enables the storage and release of energy through a reversible reaction between rust and iron, allowing for rechargeable and cyclic energy dissipation. Furthermore, they proposed loading porous rust onto a two-dimensional conductive material and then fabricating it into granular (or microsphere) shapes. This electrode material facilitates the preparation of a negative electrode with densely bonded components yet abundant porosity. This significantly improves structural stability and allows for the construction of multidimensional conductive pathways within the negative electrode system using only two-dimensional conductive materials. It also provides a large contact area with the electrolyte, short ion diffusion paths, more reactive sites, and buffers the volume expansion of the material during charging and discharging, thereby improving the overall performance of the air battery.

[0082] Furthermore, this invention relates to and provides a novel electrode material with outstanding performance. The electrode material comprises a two-dimensional conductive material and ferric oxide supported on the two-dimensional conductive material. The ferric oxide has a porous structure, and the electrode material is in granular form.

[0083] In some cases, the electrode material also includes a first zero-dimensional conductive material. Furthermore, the first zero-dimensional conductive material can be loaded onto a two-dimensional conductive material. By adding a zero-dimensional conductive material to the particulate electrode material, it is beneficial to increase the electrical contact between ferric oxide and the two-dimensional conductive material in the electrode material, improve the utilization rate of the active material, and increase the electron transport capability and efficiency.

[0084] The first zero-dimensional conductive material can be any solid particulate material with excellent conductivity, such as conductive carbon material, which can be conductive carbon particles, and conductive carbon particles can be acetylene black particles, conductive carbon black particles, Ketjen black particles, etc.

[0085] The first zero-dimensional conductive material, by mass percentage, accounts for 2%-10% of the total mass of the two-dimensional conductive material and ferric oxide. For example, it can account for 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, etc. The particle size of the first zero-dimensional conductive material is 10-300 nm. Furthermore, the particle size of the first zero-dimensional conductive material is 12-95 nm, or 15-90 nm, or 20-85 nm, or 25-80 nm, or 30-75 nm, or 35-70 nm, or 40-50 nm, or 40-65 nm, or 45-60 nm, or 50-55 nm, or 100-120 nm, or 130-140 nm, or 150-160 nm, or 170-180 nm, or 190-200 nm, or 210-220 nm, or 230-240 nm, or 250-260 nm, or 270-280 nm, or 290-300 nm, etc. In this invention, the first zero-dimensional conductive material is commercially available, and the particle size of commercially available sources may not be completely uniform, but is generally within a range.

[0086] See Figure 1 As shown, this is a specific example of the present invention. Ferric oxide with a porous structure and a first zero-dimensional conductive material are both loaded onto a two-dimensional conductive material. Ferric oxide and the first zero-dimensional conductive material are mixed together, with the two-dimensional conductive material serving as a carrier. These are then formed into granular electrode materials, such as spherical granules. After forming the granular electrode material, on the one hand, the effective contact area between the active material (ferric oxide) and the two-dimensional conductive material can be significantly increased, while the first zero-dimensional conductive material interspersed between them further enhances the electrical contact effect. On the other hand, the granular electrode material has a more stable structure and the particle size is easier to uniform, which is beneficial for preparing electrodes with a compact structure between material components and batch-to-batch uniform quality. Simultaneously, the presence of the porous structure of ferric oxide gives the electrode material a rich pore structure, significantly increasing the contact area with the electrolyte, shortening the ion diffusion path, and exposing more reactive sites, which helps to improve the electrochemical reaction rate and specific capacity. The pore structure can also effectively buffer the volume expansion of the material during charging and discharging, avoiding phenomena such as material breakage and enhancing cycle stability.

[0087] The particle size of the electrode material ranges from 1 to 100 μm, including but not limited to 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, and 15 μm. , 15.5μm, 16μm, 16.5μm, 17μm, 17.5μm, 18μm, 18.5μm, 19μm, 19.5μm, 20μm, 22μm, 25μm, 28μm, 30μm, 33μm, 35μm, 36μm, 38μm, 40μm, 42μm, 45μm, 48μm, 50μm, 55μm, 60μm, 65μm, 70μm, 75μm, 80μm, 85μm, 88μm, 90μm, 95μm, 98μm, etc.

[0088] Two-dimensional conductive materials can be any solid material with excellent conductivity, such as two-dimensional conductive carbon materials. Two-dimensional conductive carbon materials are commercially available or can be prepared using methods commonly used in the art. Examples of two-dimensional conductive carbon materials include graphene and carbon nanosheets.

[0089] 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.

[0090] Ferric oxide exists in the form of ferric oxide particles with a particle size of 2-1000 nm. Further, the particle size of the ferric oxide particles can be 5-1000 nm, or 10-1000 nm, or 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.

[0091] In this invention, ferric oxide with a porous structure is selected, and its porosity can be 20%-50%. Furthermore, the specific surface area of ​​ferric oxide is greater than or equal to 10 m² / g.2 / g, for example, the specific surface area of ​​ferric oxide can be 10-200m². 2 / g. Furthermore, the specific surface area of ​​ferric oxide is 10-50 m² / g. 2 / g.

[0092] In this invention, the porous ferric oxide particles can be commercially available or prepared according to conventional methods in the art. For example, they can be prepared as follows: a surfactant (such as F127) and a soluble iron salt (such as ferric chloride or ferric nitrate) are dissolved in ethanol, and an appropriate amount of alkaline aqueous solution such as ammonia is added to prepare a mixed solution. After mixing evenly, the solution is slowly evaporated at low temperature to obtain a gel-like substance. The gel is then ground and calcined in an air atmosphere at a temperature generally higher than 600°C. F127 is first kept at a low temperature (such as 250°C) for about 1 hour to slowly decompose, thereby preparing the porous ferric oxide particles.

[0093] The porous iron oxide particles used in the examples can also be commercially available or prepared according to conventional methods in the art. For example, they can be prepared as follows: a surfactant (such as F127) and a soluble iron salt (such as ferric chloride or ferric nitrate) are dissolved in ethanol, and an appropriate amount of alkaline aqueous solution such as ammonia is added to prepare a mixed solution. After mixing evenly, the solution is slowly evaporated at low temperature to obtain a gel-like substance. The gel is then ground and sintered in a 5% hydrogen-argon mixed atmosphere at a temperature generally higher than 600°C. The F127 is first slowly decomposed at a low temperature (such as 250°C) for about 1 hour to prepare porous iron oxide particles.

[0094] The mass ratio of ferric oxide to the two-dimensional conductive material is 1.5-4:1, for example, it can be 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, 3:1, 3.1:1, 3.2:1, 3.3:1, 3.4:1, 3.5:1, 3.6:1, 3.7:1, 3.8:1, 3.9:1, 4.0:1, etc.

[0095] In this invention, granular electrode materials can be produced by mixing and granulating the components. The particle size distribution of the granular electrode materials can be controlled by controlling the granulation parameters. For example, the components, namely the two-dimensional conductive material and the porous rust component system, can be transformed into granules (e.g., spherical particles, where "spherical" can refer to a standard spherical structure or a roughly spherical or near-spherical structure) through spray granulation. This results in better contact between the active material and the conductive agent, significantly reducing the electron transport impedance of the electrode system. The microspheres produced by granulation have a uniform structure, making them more suitable for large-scale production and contributing to batch-to-batch quality stability.

[0096] In specific implementation examples, the preparation methods of electrode materials include:

[0097] A slurry is prepared by dispersing a two-dimensional conductive material and ferric oxide with a porous structure in a first solvent.

[0098] Selectively add a first zero-dimensional conductive material to the slurry (i.e., the first zero-dimensional conductive material may or may not be added), and disperse it evenly;

[0099] Granulation is carried out.

[0100] Furthermore, the first solvent may include, but is not limited to, water and / or alcohol; further, the alcohol may include, but is not limited to, ethanol. The solid content of the slurry may be 3%-20%, and more particularly, 7%-10%.

[0101] Granulation methods include spray granulation, but other methods can also be used. Furthermore, spray granulation is carried out using a spray dryer (a device that can simultaneously dry and granulate, spraying liquid material into a mist so that it comes into contact with hot air and is dried). The inlet temperature can be set to 190-210℃, and the outlet temperature to 90-110℃.

[0102] The electrode material of this invention, when mixed with a second zero-dimensional conductive material and a binder, can form a composite material for preparing a negative electrode for an air battery. This composite material is then bonded to a current collector, and can be molded by pressure or hot pressing. This not only avoids the defects of wet processes, but also avoids the defects of conventional iron negative electrodes using dry processes, such as excessively high compaction density, difficulty in electrolyte penetration, easy loss, shedding, or significant transfer of active material during cycling, and difficulty in contacting conductive agents. This overcomes the problems of prior art where one aspect is sacrificed for another.

[0103] The addition of a second zero-dimensional conductive material can further improve the electrical conductivity between the particulate electrode material and the current collector. The binder can firmly bond the particulate electrode material, the second zero-dimensional conductive material, and the current collector together to form an electrode structure with good electrochemical and mechanical properties. The mass ratio of electrode material, second zero-dimensional conductive material, and binder is 8-10:0.5-2:1. Further, the mass ratio of electrode material, second zero-dimensional conductive material, and binder is 8-10:0.8-1.2:1.

[0104] The second zero-dimensional conductive material may include, but is not limited to, conductive carbon materials, such as, but not limited to, acetylene black and / or conductive carbon black. The particle size of the second zero-dimensional conductive material is 10-300 nm, for example, 12-95 nm, or 15-90 nm, or 20-85 nm, or 25-80 nm, or 30-75 nm, or 35-70 nm, or 40-50 nm, or 40-65 nm, or 45-60 nm, or 50-55 nm, or 100-120 nm, or 130-140 nm, or 150-160 nm, or 170-180 nm, or 190-200 nm, or 210-220 nm, or 230-240 nm, or 250-260 nm, or 270-280 nm, or 290-300 nm, etc.

[0105] Furthermore, 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.

[0106] The composite material is prepared by mixing and homogenizing the electrode material, the second zero-dimensional conductive material, and the binder.

[0107] The following is combined Figures 2 to 5 The negative electrode for an air battery containing electrode materials, a rust-air battery, and their preparation methods are described.

[0108] The negative electrode for an air battery comprises a composite material and a current collector. The composite material includes an electrode material, a second zero-dimensional conductive material, and a binder. The composite material 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 out or to 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 the two-dimensional conductive material and other conductive materials. In this invention, the electrode material is granular. When loaded onto the current collector, the particles can be closely arranged, thus creating multiple pathways that are not easily blocked, relying almost entirely on the two-dimensional conductive material. This allows electrons to be rapidly transferred between the active material and the current collector, greatly improving electron transfer efficiency. Conductivity; the material and form of the current collector are not particularly limited and can be appropriately determined. As a conductive matrix material that is in close contact with the active material in the electrode to collect electrons (or ions) and transport them to the external circuit (or counter electrode), it can be made of metal materials, etc. Preferably, it is a mesh that allows the electrolyte to penetrate smoothly, such as stainless steel mesh. The thickness of the current collector is also not particularly limited and can be appropriately determined. Typically, the thickness of the current collector can be 50-200μm, for example, it can be 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, 110μm, 120μm, 130μm, 140μm, 150μm, 160μm, 170μm, 180μm, 190μm, etc.

[0109] In specific cases, the thickness of the negative electrode is 500μm-10mm, for example, it can be 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.

[0110] This invention solves the problem of the difficulty in achieving both conductivity and porosity in existing iron anodes. Current 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. However, it is difficult to achieve both excellent conductivity and porosity. This invention proposes a special electrode material that contains ferric oxide with a porous structure and a two-dimensional conductive material. These are mixed and formed into granules. Through the combination of materials and the design of the structure, the conductivity of the anode is achieved to be 1-10 S / cm, and the porosity is 35%-55%.

[0111] In a specific case, the preparation method of the negative electrode for an air battery includes: setting a composite material on a current collector to form a negative electrode.

[0112] Furthermore, the method for preparing the negative electrode for an air battery includes: treating the composite material by rolling, grinding or shearing to cause the binder to become fibrous, obtaining a pretreated composite material, and then pressing the pretreated composite material onto a current collector to form a negative electrode sheet for an air battery.

[0113] Furthermore, the pressing pressure is 6-10 MPa.

[0114] In the process of preparing the negative electrode for the air battery, a current collector is first placed in a mold, the pretreated composite material is placed on the current collector, and then pressed with a press to form the negative electrode for the air battery.

[0115] Furthermore, the method for preparing the negative electrode for an air battery includes: mixing electrode material, a second zero-dimensional conductive material, and PTFE in a predetermined ratio by high-speed stirring (approximately 2000-3000 rpm, mixing for 10-60 minutes) to obtain a pretreated composite material; then pressing the pretreated composite material onto a current collector to form a negative electrode sheet for an air battery, which is sheet-shaped, as shown in the schematic diagram. Figure 2 As shown, the lower layer is the current collector 10, and the upper layer is the pretreated composite material 11.

[0116] 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.

[0117] Air cathodes can use existing conventional structures and materials without any particular restrictions.

[0118] An air positive electrode can be prepared as follows: a second solvent, Nafion (perfluorosulfonic acid resin) solution, a catalyst, and a conductive agent are mixed to form a positive electrode slurry. This slurry is then applied (e.g., by coating) onto 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 second solvent can be water and / or alcohol, and the alcohol can be ethanol, etc.; 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, etc.; the conductive agent can be carbon black, etc.; the positive electrode current collector can be carbon paper, etc.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] Unless otherwise specified in the following examples, all raw materials are commercially available or prepared using conventional methods in the art. In the examples described below, porous rust particles A have an average particle size of approximately 100 nm and a specific surface area of ​​approximately 43.7 m². 2 / g, with a porosity of approximately 32%; porous rust particles B, with an average particle size of approximately 500nm and a specific surface area of ​​approximately 22.5m². 2 / g, porosity approximately 24%; commercially available graphene, thickness approximately 1-10nm, sheet diameter approximately 1-10μm, purchased from Xiamen Kaina Graphene Technology Co., Ltd.; conductive carbon black, Super P, purchased from Xianfeng Nano, particle size 30-45nm, item number 101095.

[0123] (Electrode materials and their preparation)

[0124] Example 1-1:

[0125] This example provides an electrode material and its preparation method. The electrode material contains 70% porous rust particles A and 30% graphene by mass percentage.

[0126] The preparation method of this electrode material includes: mixing 70% porous rust (Fe2O3) particles A and 30% graphene, then adding a mixed solution of water and ethanol (the volume ratio of water to ethanol is 9:1), grinding until a stable slurry is formed (the solid content is about 8 wt.%), pouring the above slurry into a spray dryer, setting the inlet temperature to 200°C and the outlet temperature to 100°C, and performing spray granulation to obtain granular electrode material.

[0127] Examples 1-2:

[0128] This example provides an electrode material and its preparation method, which are basically the same as those in Examples 1-1, except that porous rust particles A are replaced with porous rust particles B in the same amount.

[0129] Examples 1-3:

[0130] This example provides an electrode material and its preparation method. The electrode material comprises porous rust particles A, graphene, and conductive carbon black, wherein the mass ratio of porous rust particles A to graphene is 7:3, and the mass of conductive carbon black added accounts for 5% of the total mass of porous rust particles A and graphene.

[0131] The preparation method of this electrode material includes: mixing porous rust (Fe2O3) particles A and graphene in a certain proportion, then adding a mixed solution of water and ethanol (volume ratio of water to ethanol is 9:1), grinding until a stable slurry is formed (solid content is about 8 wt.%), adding a predetermined proportion of conductive carbon black to the slurry, dispersing it evenly, and then pouring it into a spray dryer. The inlet temperature is set at 200℃ and the outlet temperature at 100℃ for spray granulation to obtain granular electrode material. A scanning electron microscope image of this granular electrode material is shown below. Figure 6 As shown, it can be seen that it exhibits obvious granular structure, and both porous rust particles and conductive carbon black are loaded onto graphene.

[0132] Examples 1-4:

[0133] This example provides an electrode material and its preparation method, which are basically the same as those in Examples 1-3, except that the mass ratio of porous rust particles A to graphene powder is 6:4.

[0134] Examples 1-5:

[0135] This example provides an electrode material and its preparation method, which are basically the same as those in Examples 1-3, except that the mass ratio of porous rust particles A to graphene powder is 8:2.

[0136] Examples 1-6:

[0137] This example provides an electrode material and its preparation method, which are basically the same as those in Examples 1-3, except that: carbon nanosheets (thickness of 3-10 nm, sheet diameter of 0.5-5 μm, purchased from Xiamen Kaina Graphene Technology Co., Ltd.).

[0138] Comparative Example 1-1:

[0139] This example provides an electrode material that is basically the same as in Examples 1-3, except that graphene is replaced with an equal amount of conductive carbon black Super P.

[0140] Comparative Examples 1-2:

[0141] This example provides an electrode material that is basically the same as in Examples 1-3, except that the porous rust particles A are replaced with the same amount of conventional non-porous rust particles (average particle size of about 100 nm, purchased from Xi'an Bona Materials Technology Co., Ltd.).

[0142] Comparative Examples 1-3:

[0143] This example provides an electrode material that is basically the same as in Examples 1-3, except that: instead of spray drying, porous rust (Fe2O3) particles A, graphene, and conductive carbon black are mechanically mixed and homogenized.

[0144] Comparative Examples 1-4:

[0145] This example provides an electrode material that is basically the same as in Examples 1-3, except that porous rust particles A are replaced with an equal amount of porous iron oxide particles.

[0146] Performance Test 1:

[0147] The particle size of the electrode materials obtained in Examples 1-1 to 1-6, Comparative Examples 1-1 to 1-2, and Comparative Examples 1-4 was tested, and the specific results are shown in Table 1.

[0148] Table 1

[0149]

[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. The composite material comprises the electrode material obtained in Examples 1-1, acetylene black (purchased from KELU, with a particle size of about 35 nm, product number MA-EN-CO-000601), and polytetrafluoroethylene (PTFE). The mass ratio of the electrode material, acetylene black, and PTFE is 9:1:1.

[0153] The composite material was prepared by mixing electrode material, acetylene black and polytetrafluoroethylene in a high-speed mixer (stirring 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 electrode material obtained in Example 1-1 is replaced with the 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 electrode material obtained in Example 1-1 is replaced with the 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 electrode material obtained in Example 1-1 is replaced with the 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 electrode material obtained in Example 1-1 is replaced with the 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 electrode material obtained in Example 1-1 is replaced with the electrode material prepared in Example 1-6.

[0164] Comparative Example 2-1:

[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 electrode material obtained in Example 1-1 is replaced with the electrode material prepared in Comparative Example 1-1.

[0166] Comparative Example 2-2:

[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 electrode material obtained in Example 1-1 is replaced with the electrode material prepared in Comparative Example 1-2.

[0168] Comparative Examples 2-3:

[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 electrode material obtained in Example 1-1 is replaced with the electrode material prepared in Comparative Example 1-3.

[0170] Comparative Examples 2-4:

[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 electrode material obtained in Example 1-1 is replaced with the electrode material prepared in Comparative Examples 1-4.

[0172] (Negative electrode for air batteries and its preparation)

[0173] Example 3-1:

[0174] This example provides a negative electrode for an air battery and its preparation method. The negative electrode comprises a stainless steel mesh (200 mesh, 120 μm thick) and a composite material obtained in Example 2-1 loaded on the stainless steel mesh. The specific preparation process is as follows: The composite material of Example 2-1 is mixed and stirred by high-speed stirring at about 2500 rpm to cause PTFE to become fibrous, resulting in a pretreated composite material. Then, the stainless steel mesh is placed in a mold, and the pretreated composite material is pressed on the stainless steel mesh (pressure about 7 MPa) to obtain a negative electrode for an air battery with an electrode thickness of about 1200 μm.

[0175] Example 3-2:

[0176] 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 electrode material obtained in Example 2-1 is replaced with the electrode material obtained in Example 2-2 with the same amount of additive.

[0177] Example 3-3:

[0178] 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 electrode material obtained in Example 2-1 is replaced with the electrode material obtained in Example 2-3 with the same amount of additive.

[0179] Examples 3-4:

[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 electrode material obtained in Example 2-1 is replaced with the electrode material obtained in Example 2-4 with the same amount of additive.

[0181] Examples 3-5:

[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 electrode material obtained in Example 2-1 is replaced with the electrode material obtained in Example 2-5 with the same amount of additive.

[0183] Examples 3-6:

[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 electrode material obtained in Example 2-1 is replaced with the electrode material obtained in Example 2-6 with the same amount of additive.

[0185] Comparative Example 3-1:

[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 electrode material obtained in Example 2-1 is replaced with the electrode material prepared in Comparative Example 2-1 with the same amount of additive.

[0187] Comparative Example 3-2:

[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 electrode material obtained in Example 2-1 is replaced with the electrode material prepared in Comparative Example 2-2 with the same amount of additive.

[0189] Comparative Example 3-3:

[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 electrode material obtained in Example 2-1 is replaced with the electrode material prepared in Comparative Example 2-3 with the same amount of additive.

[0191] Comparative Examples 3-4:

[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 electrode material obtained in Example 2-1 is replaced with the electrode material prepared in Comparative Example 2-4 with the same amount of additive.

[0193] Performance Test 2:

[0194] The conductivity and porosity of the negative electrodes used in the air batteries obtained in Examples 3-1 to 3-6 and Comparative Examples 3-1 to 3-4 were tested, and the specific results are shown in Table 2. Conductivity was determined using the four-probe film impedance 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, and edge bending was avoided; 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 determined using the BET method (gas adsorption method).

[0195] Table 2

[0196]

[0197] (Rust-air batteries and their preparation)

[0198] Example 4-1:

[0199] 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.

[0200] 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 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 approximately 0.36 mm.

[0201] The electrolyte is an aqueous solution of potassium hydroxide with a concentration of 6 mol / L.

[0202] according to Figures 4 to 5 The structure shown is installed as a rust-air battery.

[0203] Example 4-2:

[0204] 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.

[0205] Example 4-3:

[0206] 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.

[0207] Example 4-4:

[0208] 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.

[0209] Examples 4-5:

[0210] 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.

[0211] Examples 4-6:

[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 3-6.

[0213] Comparative Example 4-1:

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

[0215] Comparative Example 4-2:

[0216] This example provides a rust-air battery, which is basically the same as Example 4-3, except that the negative electrode is the negative electrode for air batteries obtained in Comparative Example 3-2.

[0217] Comparative Example 4-3:

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

[0219] Comparative Example 4-4:

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

[0221] Performance Test 3:

[0222] Charge-discharge experiments were conducted on the rust-air batteries obtained in Examples 4-1 to 4-6 and Comparative Examples 4-1 to 4-4. The charge-discharge rate was 0.1C; the test temperature was 25℃ (room temperature); the charge-discharge experimental procedure was 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 0.1C for 10 hours with a cutoff voltage of 2V, then left to stand for 5 minutes, then discharged at 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 3.

[0223] Table 3

[0224]

[0225] Figure 7The graphs show the cycle performance of the rust-air batteries obtained in Examples 4-3 and Comparative Examples 4-1 to 4-4. It is evident that Example 4-3 not only exhibits a higher specific capacity but also better cycle stability and a relatively better capacity retention rate. Comparative Example 4-1, which uses electrode materials without graphene, has a very low specific capacity, and its cycle retention rate is significantly lower than that of Example 4-3. Comparative Example 4-2 uses non-porous rust particles as its electrode material, resulting in poor cycle performance and a significantly lower cycle retention rate compared to Example 4-3. Comparative Example 4-3 uses electrode materials that have not undergone granulation, resulting in a low specific capacity and poor cycle performance. Comparative Example 4-4 uses electrode materials with iron(III) oxide as the active component, and both its specific capacity and cycle performance are significantly lower than those of Example 4-3.

[0226] 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.

[0227] 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.

[0228] 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 negative electrode material for an air battery, characterized in that, The negative electrode material comprises a two-dimensional conductive carbon material, ferric oxide loaded on the two-dimensional conductive carbon material, and a first zero-dimensional conductive material. The ferric oxide has a porous structure, and the negative electrode material is a spherical particle produced by spray granulation. The mass ratio of the ferric oxide to the two-dimensional conductive carbon material is 1.5-4:1; The mass percentage of the first zero-dimensional conductive material is 2%-10% of the total mass of the two-dimensional conductive carbon material and the ferric oxide.

2. The negative electrode material according to claim 1, characterized in that, The two-dimensional conductive carbon material is graphene; and / or, the thickness of the two-dimensional conductive carbon material is 1-300 nm, and the sheet diameter is 0.5-20 μm.

3. The negative electrode material according to claim 1, characterized in that, The ferric oxide exists in the form of ferric oxide particles with a particle size of 2-1000 nm; and / or, the porosity of the ferric oxide is 20%-50%; and / or, the mass ratio of the ferric oxide to the two-dimensional conductive carbon material is 1.5-3:

1.

4. The negative electrode material according to claim 1, characterized in that, The specific surface area of ​​the ferric oxide is greater than or equal to 10 m². 2 / g.

5. The negative electrode material according to claim 4, characterized in that, The specific surface area of ​​the ferric oxide is 10-50 m². 2 / g.

6. The negative electrode material according to claim 1, characterized in that, The first zero-dimensional conductive material is a conductive carbon material.

7. The negative electrode material according to claim 1, characterized in that, The first zero-dimensional conductive material is loaded onto the two-dimensional conductive carbon material; and / or, the first zero-dimensional conductive material comprises conductive carbon black particles; and / or, the particle size of the first zero-dimensional conductive material is 10-300 nm.

8. The negative electrode material according to claim 1, characterized in that, The particle size of the negative electrode material is 1-100 μm.

9. The negative electrode material according to any one of claims 1-8, characterized in that, The particle size of the negative electrode material is 10-50 μm.

10. A method for preparing the negative electrode material according to any one of claims 1-9, characterized in that, The preparation method includes: Two-dimensional conductive carbon material and ferric oxide with a porous structure are dispersed in a first solvent to form a slurry; A first zero-dimensional conductive material is added to the slurry and dispersed evenly; Spray granulation is performed.

11. The method for preparing the negative electrode material according to claim 10, characterized in that, The first solvent is water and / or alcohol; and / or, the solid content of the slurry is 3%-20%.

12. A composite material for preparing a negative electrode for an air battery, characterized in that, The composite material comprises the negative electrode material for air batteries as described in any one of claims 1-9, a second zero-dimensional conductive material, and a binder.

13. The composite material for preparing a negative electrode for an air battery according to claim 12, characterized in that, The mass ratio of the negative electrode material, the second zero-dimensional conductive material, and the binder is 8-10:0.5-2:1; and / or, the second zero-dimensional conductive material is a conductive carbon material; and / or, the binder includes polytetrafluoroethylene.

14. The composite material for preparing a negative electrode for an air battery according to claim 12, characterized in that, The particle size of the second zero-dimensional conductive material is 10-300 nm; and / or, the second zero-dimensional conductive material contains conductive carbon black; and / or, the composite material is prepared by mixing and homogenizing the negative electrode material, the second zero-dimensional conductive material and the binder.

15. A negative electrode for an air battery, characterized in that, The negative electrode comprises the composite material and current collector as described in any one of claims 12-14 for preparing a negative electrode for an air battery.

16. The negative electrode for an air battery according to claim 15, characterized in that, The current collector is a stainless steel mesh; and / or, the thickness of the current collector is 50-200 μm; and / or, the thickness of the negative electrode is 500 μm-10 mm.

17. A method for preparing a negative electrode for an air battery according to claim 15 or 16, characterized in that, The preparation method includes: placing the composite material on a current collector to form a negative electrode.

18. The method for preparing a negative electrode for an air battery according to claim 17, characterized in that, The method for preparing the negative electrode for the air battery includes: The composite material is processed by rolling, grinding or shearing to cause the binder to become fibrous, resulting in a pretreated composite material. The pretreated composite material is then pressed onto the current collector to form a negative electrode sheet for an air battery.

19. The method for preparing a negative electrode for an air battery according to claim 18, characterized in that, The pressing pressure is 6-10 MPa.

20. A negative electrode for an air battery, characterized in that, The negative electrode comprises a current collector, spherical granular negative electrode material produced by spray granulation, conductive particles, and a binder. The negative electrode material comprises graphene, ferric oxide particles with a porous structure supported on the graphene, and zero-dimensional conductive carbon material. The conductivity of the negative electrode is 1-10 S / cm, and the porosity is 35%-55%. The mass ratio of the ferric oxide particles to the graphene is 1.5-4:

1. The mass percentage of the zero-dimensional conductive carbon material is 2%-10% of the total mass of the graphene and the ferric oxide particles.

21. An air battery, characterized in that, The 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 15-16 and 20, or an air battery negative electrode prepared by the method described in any one of claims 17-19.

22. The air battery according to claim 21, 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 - .

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