WO2015051627A1

WO2015051627A1 - Rod-shaped nano iron oxide electrode material, and preparation method therefor and application thereof

Info

Publication number: WO2015051627A1
Application number: PCT/CN2014/075130
Authority: WO
Inventors: 曾宏; 武英; 戚雯; 况春江; 周少雄
Original assignee: 安泰科技股份有限公司
Priority date: 2013-10-12
Filing date: 2014-04-11
Publication date: 2015-04-16
Also published as: CN103606672A

Abstract

Disclosed in the present invention are a rod-shaped nano iron oxide electrode material and a preparation method therefor. The preparation method is: using FeCl3?6H2O, ammonium dihydrogen phosphate and water for hydrothermal reaction as raw materials, and washing the resulting precipitates to obtain rod-shaped nano iron oxide. The nano iron oxide is in a rod shape with an average diameter of 60-80 nm, a length of 250-300 nm, a purity of more than 99.9% and a crystal phase α-Fe2O3. The rod-shaped nano iron oxide electrode material can be used not only as a positive electrode active material for lithium ion batteries, but also as a negative electrode active material for lithium ion batteries. The raw materials used in the preparation method are easily available, nontoxic and free from environmental pollution; the preparation process is simple and convenient to operate, and suitable for large-scale industrial production. The use of the rod-shaped nano iron oxide electrode material as the positive or negative electrode active material for lithium ion batteries leads to such advantages as low cost, excellent electrochemical performances, good chemical stability of the electrode material, high specific capacity, and small polarization of the charge and discharge platform.

Description

Rod-shaped nano-iron oxide electrode material, preparation method and application thereof

The invention belongs to the technical field of preparation of electrode materials for lithium ion batteries, and particularly relates to a rod-shaped nano-iron oxide electrode material, a preparation method and application thereof, the rod-shaped nano-iron oxide has regular shape, uniform size, high purity, and can be used as positive and negative Electrode material. Background technique

As a new type of high-energy battery, lithium-ion battery has the advantages of high energy density, long service life, good cycle performance and no memory effect. It is widely used in mobile electronic products such as mobile phones, notebook computers, digital cameras and so on. In recent years, lithium-ion batteries have become one of the most valuable energy storage devices in the 21st century in the fields of electric vehicles, power tools, smart power grids, distributed energy systems, aerospace, and defense.

Due to its high theoretical specific capacity, abundant reserves, easy preparation, non-toxicity, environmental friendliness and low cost, iron oxide nanomaterials have become a research hotspot in the field of lithium ion battery materials. Common methods for synthesizing nano-iron oxides include mechanical ball milling, hydrothermal reaction, or synthesis of iron oxide nanomaterials by layer-by-layer self-assembly and subsequent heat treatment using FeOOH nanorods as precursors.

The mechanical ball milling method has the following drawbacks despite the simple method: The obtained material has low purity, contains other impurities, and the prepared material is generally granular and the particle distribution is uneven.

In the existing method for synthesizing nanometer iron oxide by hydrothermal reaction, there are generally the following defects: the acquisition of the raw material is not easy, for example, the patent application disclosed in CN102674472A incorporates ferric chloride hexahydrate into the nanocellulose, the nanometer. Cellulose also needs to be prepared by a special method, so the acquisition of raw materials is complicated; the raw materials contain toxic organic components, pollute the environment and the like.

A method for preparing nanometer iron oxide by using FeOOH nanorods as a precursor, generally adding a base, It is polluted by the environment. In addition, the obtained materials must be annealed at about 600 degrees, the process flow is long, the operation steps are cumbersome, the efficiency is low, and the energy consumption is high.

At present, nano-iron oxide prepared by the above method is generally used as a negative electrode material for a lithium ion battery, and is basically not used as a positive electrode material, and a lithium salt such as lithium iron phosphate is usually used as a positive electrode material. The main constituent materials of lithium-ion battery include electrolyte, isolation material, positive and negative materials, etc. The positive electrode material occupies a large proportion (the mass ratio of positive and negative materials is 3:1~4:1), and the cost directly determines the battery cost. High and low. Therefore, the development of low-cost cathode materials is a market demand.

Summary of the invention

One of the objects of the present invention is to provide a method for preparing a rod-shaped nano-iron oxide electrode material in view of the defects existing in the prior art. This method is simple and easy.

Another object of the present invention is to provide a rod-shaped nano-iron oxide electrode material prepared by the above method and its use in a lithium ion battery. The obtained rod-shaped nano-iron oxide not only has a relatively large specific surface area, a regular morphology, a uniform size, and good electrochemical performance.

In order to achieve the above object, the present invention adopts the following technical solutions:

A method for preparing a rod-shaped nanometer iron oxide electrode material, wherein a hydrothermal reaction is carried out by using FeCl ₃ «6H ₂ 0, ammonium dihydrogen phosphate (NH ₄ H ₂ P0 ₄ ) and water as raw materials, and the resulting precipitate is washed to obtain a rod shape. Nano-iron oxide powder.

The mechanism of the above hydrothermal reaction is:

NH ₄ H ₂ P0 ₄ = NH ₃ ⁺ +H ₃ P0 ₄ "

H ₃ P0 ₄ " +H ₂ 0= H ₃ P0 ₄ +OH"

FeCl ₃ «6H ₂ 0= FeCl ₃ +6H ₂ 0

3 OH ^_ + Fe ³⁺ = Fe(OH) ₃ |

2Fe(OH) ₃ = Fe ₂ 0 ₃ |+3H ₂ 0

In the above preparation method of the rod-shaped nano-iron oxide electrode material, as a preferred embodiment, the hydrothermal reaction temperature is 200-240 ° C, and the hydrothermal reaction time is 1-10 h. Exemplary The temperature of the hydrothermal reaction is 202 ° C, 210 ° C, 218 ° C, 225 ° C, 230 ° C, 235 ° C or 238. C, hydrothermal reaction time is 1.5h, 2h, 2.5h, 3h, 4h, 5h, 6h, 7h, 8h, 8.5h or 9.5h. More preferably, the temperature of the hydrothermal reaction is 210-230 ° C, and the time of the hydrothermal reaction is 4-5 h.

In the above preparation method of the rod-shaped nano-iron oxide electrode material, as a preferred embodiment, the molar ratio of FeCl ₃ «6H ₂ 0 to ammonium dihydrogen phosphate in the raw material is 26: 1-30: 1, exemplarily Can be 26.5: 1, 27: 1, 28: 1, 29: 1 or 29.5: 1. Preferably, the molar ratio of FeCl ₃ *6H ₂ 0 to ammonium dihydrogen phosphate in the raw material is 27: 1-28: 1.

In the above method for producing a rod-shaped nano-iron oxide electrode material, as a preferred embodiment, the precipitate is washed successively with deionized water and alcohol.

A rod-shaped nano-iron oxide electrode material prepared by the above method has a rod shape, an average diameter of 60-80 nm, a length of 250-300 nm, a purity of 99.9% or more, and a crystal phase of a-Fe ₂ 0 ₃ .

The above rod-shaped nano-iron oxide electrode material is used in a lithium ion battery, and the rod-shaped nano-iron oxide electrode material is used as an active material of a positive electrode or a negative electrode of a lithium ion battery. Preferably, the specific method of the application is as follows:

First, a binder and a conductive agent are added to the rod-shaped nano-iron oxide powder, thoroughly mixed by grinding, and then the mixed slurry is filtered to obtain a uniform pre-coated refining slurry; The pre-coated refining slurry is applied to the surface current collector of the aluminum foil surface and the current collector of the copper foil, and dried to form a battery positive electrode sheet and a battery negative electrode sheet having an active material.

In the above application, as a preferred embodiment, in the first step, the mass percentage of the binder, the conductive agent and the rod-shaped nano iron oxide powder is: binder: 10-20%; conductive agent : 10-30%; rod-shaped nano iron oxide powder: 50-80%. More preferably, the binder: 10; a conductive agent: 20%; a rod-shaped nano iron oxide powder: 70%.

In the above application, as a preferred embodiment, in the first step, the grinding time is 40-60 min, and exemplarily, the grinding time is 42 min, 45 min, 50 min, 55 min. Or 58min.

In the above application, as a preferred embodiment, in the second step, the drying temperature is 100-120 ° C, and the drying time is 18-24 h. Illustratively, the drying temperature is 105 ° C, 110. C, 102. C, 108. C or 120. C, drying time is 18.5h, 20h, 21h, 22h, 23h or 23.5h.

In the above applications, the binder and the conductive agent are reagents commonly used in the art. Wherein, the binder may be polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose (CMC) or polyolefin (PP, PE and other copolymers: the conductive agent may be Carbon black super P, conductive graphite, ketjen black, carbon nanotubes or nano carbon fibers.

Compared with the prior art, the present invention has the following beneficial effects:

1) The preparation method of the rod-shaped nano iron oxide powder of the invention, the raw material is easy to obtain and non-toxic; the reactant can have a wide concentration range and is easy to control; the toxic substance is not used in the whole reaction, and the reaction does not need to add a surfactant, Catalyst, etc., no pollution to the environment; easy to separate products, few impurities, high purity; simple preparation process, convenient operation, easy to large-scale industrial production.

2) The rod-shaped nano-iron oxide powder obtained by the above method has uniform shape and uniform size, and has a rod shape, and the average diameter is about 60-80 nm, and the length is about 250-300 nm, and the purity of the material is high.

3) The above rod-shaped nano-iron oxide powder is used as a positive and negative electrode active material of a lithium ion battery, and has low cost, good electrochemical performance, good chemical stability of the electrode material, high specific capacity, and low polarization of the charge and discharge platform. It has been proved by experiments that the positive and negative electrodes made of the iron oxide nanorods have good charge and discharge cycles and can be used as electrode materials for lithium ion batteries. The iron oxide nanorod negative electrode materials are charged and discharged under the current of 100mAh/g for the first time. The discharge capacity reaches 1030 mAh/g, the first charge capacity reaches 723 mAh/ _{g; the} iron oxide nanorod positive electrode has a current discharge capacity of 222.4 mAh/g at a current of 20 mAh/g, and the first charge capacity is 175 mAh/g. DRAWINGS

Figure 1 is a hydrothermal method for synthesizing iron oxide (Fe ₂ O ₃ ) nanorods (ie, rod-shaped nano-iron oxides, hereinafter referred to as iron oxide nanorods) by a hydrothermal reaction temperature (low-magnification SEM photograph), specifically hydrothermal reaction temperature Scanning electron micrograph (low-magnification SEM photograph) of iron oxide (Fe ₂ O ₃ ) nanorods prepared at 220 ° C (ie, Example 1); as can be seen from the above picture, the obtained nanomaterials are uniform in size and rod-shaped. The diameters are all about 60-80 nm, and the lengths are about 250-300 nm.

2 is a topographical view (high-power SEM photograph) of a hydrothermally synthesized iron oxide (Fe ₂ O ₃ ) nanorod, specifically an iron oxide prepared by a hydrothermal reaction temperature of 220 ° C (ie, Example 1). ₂ 0 ₃ ) Scanning electron micrograph of nanorods (high magnification SEM photograph). As can be seen from the above picture, the obtained nanomaterials are uniform in size and have a rod shape with a diameter of about 60-80 nm and a length of about 250-300 nm.

Figure 3 is a hydrothermal synthetic iron oxide (Fe ₂ 0 ₃₎ XRD pattern, particularly the hydrothermal reaction temperature is detected XRD pattern of synthetic iron oxide (Fe ₂ 0 ₃₎ when the 220 ° C (i.e. Example 1 embodiment), It is found from the figure that the diffraction peaks of the prepared nanomaterials are all XRD of Fe ₂ 0 ₃ nanorods. The XRD spectrum can confirm that the product is a-Fe ₂ 0 ₃ phase, and the characteristic peak is obvious.

4 is a Raman spectrum of iron oxide nanorods, specifically a Raman spectrum of iron oxide (Fe ₂ 0 ₃ ) synthesized at a hydrothermal reaction temperature of 220 ° C (ie, Example 1), and the prepared nanomaterials are found from the map. The diffraction peaks are all Raman peaks of Fe ₂ 0 ₃ nanorods. The Raman structure of iron oxide nanorods is characterized by typical iron oxide. The product was confirmed to be Fe ₂ 0 ₃ by Raman spectrum.

5 is a capacity-voltage curve of a button cell assembled with the iron oxide nanorods prepared in Example 1 as a negative electrode material. It can be seen from the figure that under the test condition of 0.1C, the iron oxide nanorod negative electrode has a first discharge capacity of 1030 mAh/ _g in the voltage range of 0.01 to 3 V _{; the} first charge capacity reaches 723 mAh/g.

6 is a capacity-cycle number and coulombic efficiency curve of a button cell assembled with the iron oxide nanorods prepared in Example 1 as a negative electrode material. As can be seen from the figure, except for the first to the 18th Coulomb efficiency In addition, the coulombic efficiency of other cycles is close to 100%.

Fig. 7 is a capacity-voltage curve of a button cell assembled by using iron oxide nanorods prepared in Example 1 as a positive electrode material. It can be seen from the figure that under the test condition of 0.1C, the iron oxide nanorod positive electrode has a first discharge capacity of 222.4 mAh/g in the voltage range of 1.5-4.5V, the first charging capacity is 175mAh/g, and the second discharge capacity is 144.4. mAh/g.

Fig. 8 is a capacity (coulombic efficiency) - cycle curve of a button cell assembled with the iron oxide nanorods prepared in Example 1 as a positive electrode material. As can be seen from the figure, in addition to the first to the 10th Coulomb efficiency, the Coulomb efficiency at other cycle times is close to 100%.

detailed description

The invention will be described in detail below by way of examples, but the invention is not limited thereto.

Example 1

Preparation of rod-shaped nano-iron oxide powder:

Weigh 0.972g of ferric chloride (FeCl ₃ '6H ₂ 0 ) and 0.01485g of ammonium dihydrogen phosphate (NH ₄ H ₂ P0 ₄ ) (the molar ratio of ferric chloride to diammonium phosphate is 26: 1) and 160 g of deionized water, all of which were placed in a hydrothermal reaction kettle at 220 ° C for 2 h of hydrothermal reaction time, and then naturally cooled to room temperature. The precipitate was washed three times with deionized water and twice with alcohol, and after separation, a rod-shaped nano-iron oxide powder was obtained, and the purity by HPLC was 99.9%.

As can be seen from Fig. 1 and Fig. 2, the obtained nanomaterials are uniform in size and rod-shaped, and the average diameters are all about 60-80 nm, and the lengths are about 250-300 nm. It can be confirmed from Fig. 3 and Fig. 4 that the product is an a-Fe ₂ 0 ₃ phase, and the characteristic peak is conspicuous.

Preparation of battery positive and negative electrode sheets having the above electrode active material:

The prepared rod-shaped nano-iron oxide powder, the binder polytetrafluoroethylene (PTFE) and the conductive agent carbon black Super P were uniformly mixed according to the mass ratio of 7: 1:2, ground for 45 minutes, and then filtered to obtain a uniform pre-preparation. Coating the refined slurry; directly applying the slurry to the surface collector of the aluminum foil, and in a vacuum oven The anode electrode sheet of the electrode active material battery was obtained by holding at a temperature of 110 ° C for 24 h. The slurry was directly applied to a copper foil surface current collector, and incubated at 110 ° C for 24 h in a vacuum oven to obtain an electrode active material battery negative electrode sheet.

The negative electrode sheet prepared in this example, the lithium sheet is a positive electrode sheet, PE (polyethylene) is a separator, LiPF ₆ lmol/1 DMC:EC:EMC=1:1:1 is an electrolyte assembled into a button battery 1- A. The battery is subjected to constant current charge and discharge experiments. The electrical performance test results are shown in Figure 5 and Figure 6. The first discharge capacity reaches 1030 mAh/ _{g at a} current density of 0.01 to 3 V and a current density of 100 mAh/ _{g; the} first charge capacity is reached. At 723 mAh/g, it can still be maintained at 90 mAh/g after 100 cycles of charge and discharge. The coulombic efficiency of other cycles is close to 100% except for the first to 18th coulombic efficiency.

The positive electrode sheet prepared in this embodiment, the lithium sheet is a negative electrode sheet, and PE (polyethylene) is a separator.

LiPF ₆ lmol/1 DMC: EC: EMC = 1: 1: 1 is assembled into a button battery 1-B. The battery is subjected to constant current charge and discharge experiments. The electrical performance test results are shown in Figure 7 and Figure 8. The first discharge capacity reaches 222.4 mAh/g and the first charge capacity in the voltage range of 1.5-4.5V and 100mA/g current density. 175mAh/g, the second discharge capacity is 144.4mAh/g, and can still be maintained at HOmAh/g after 20 cycles of charge and discharge. The coulombic efficiency is close to 100% except for the first to the 10th Coulomb efficiency. . Example 2

Preparation of rod-shaped nano-iron oxide powder:

Weigh ferric chloride (FeCl ₃ *6H ₂ 0) 0.695g, ammonium dihydrogen phosphate (NH ₄ H ₂ P0 ₄ ) O.Olg

(The molar ratio of ferric chloride to ammonium dihydrogen phosphate is 30:1) and deionized water (120g), all of which are placed in a hydrothermal reaction kettle. At 220 °C, the hydrothermal reaction time is 2 h. Then naturally cool to room temperature. The precipitate was washed three times with deionized water and twice with alcohol, and after separation, a rod-shaped nano-iron oxide powder was obtained, and the purity by HPLC was 99.9%.

After low-magnification SEM analysis, the obtained nanomaterials are uniform in size and rod-shaped, with diameters of about 60-80. Around nanometer, the length is about 250-300 nanometers. The product was confirmed to be a-Fe ₂ 0 ₃ phase by XRD analysis at 33 °, 35.7 °, 53.9. Significant a-Fe ₂ 0 ₃ characteristic peaks were observed at the position.

Preparation of battery positive and negative electrode sheets having the above electrode active material: Same as in Example 1. The negative electrode sheet prepared in this example, the lithium sheet is a positive electrode sheet, PE (polyethylene) is a separator, LiPF ₆ lmol/1 DMC:EC:EMC=1:1:1 is an electrolyte assembled into a button battery 2 A. The battery was subjected to a constant current charge and discharge test. The initial discharge capacity reached 1384 mAh/ _{g at a} current density of 0.01 mA/ _{g at a} current density of 0.01 mA/ _{g; the} first charge capacity reached 773 mAh/g, and the charge and discharge cycle was still 100 times. Maintained at 200 mAh/g, the coulombic efficiency of the other cycles is close to 100%, except for the first to third coulombic efficiency.

LiPF ₆ lmol/1 DMC: EC: EMC=1:1: 1 is assembled into a button battery 2-B. The battery was subjected to a constant current charge and discharge test. The initial discharge capacity reached 197 mAh/g at a current density of 1.5 mA/g at a current range of 1.5-4.5 V, and the first charge capacity was 169 mAh/g. Maintained at 98 mAh/g, the coulombic efficiency at other cycle times is close to 100%, except for the first to second coulombic efficiency. Example 3

Preparation of rod-shaped nano-iron oxide powder: The preparation method of the rod-shaped nano-iron oxide powder of Example 1 was the same except that the hydrothermal reaction condition was 205 ° C and the reaction time was 8 h.

After low-magnification SEM analysis, the obtained nanomaterials are uniform in size and rod-shaped, with diameters of about 60-80 nm and lengths of about 250-300 nm. The product was confirmed to be a-Fe ₂ 0 ₃ phase by XRD analysis at 33.1 °, 35.6 °, 53.8. Significant a-Fe ₂ 0 ₃ characteristic peaks were observed at the position.

Preparation of battery positive and negative electrode sheets having the above electrode active material: Same as in Example 1. The negative electrode sheet prepared in this example, the lithium sheet is a positive electrode sheet, PE (polyethylene) is a separator, LiPF ₆ lmol/1 DMC:EC:EMC=1:1:1 is an electrolyte assembled into a button battery 3- A. Carry out the battery Constant current charge and discharge test, the first discharge capacity reached 1281mAh / _g in the voltage range of 0.013V, 100mA / _g current density _{; the} first charge capacity reached 781mAh / g, after the charge and discharge cycle 50 times can still maintain at 330mAh /g, except for the first to second coulombic efficiency, the coulombic efficiency of the other cycles is close to 100%.

LiPF ₆ lmol/1 DMC: EC: EMC=1:1: 1 is assembled into a button battery 3-B. The battery was subjected to constant current charge and discharge experiments. The initial discharge capacity reached 183 mAh/g and the first charge capacity was 174 mAh/g in the voltage range of 1.5-4.5 V and 100 mA/g current density. Maintained at 83 mAh/g, the coulombic efficiency at other cycle times is close to 100%, except for the first to second coulombic efficiency. Example 4

Preparation of rod-shaped nano-iron oxide powder: The preparation method of the rod-shaped nano-iron oxide powder of Example 1 was the same except that the hydrothermal reaction condition was 240 ° C and the reaction time was 4 h.

After low-magnification SEM analysis, the obtained nanomaterials are uniform in size and rod-shaped, with diameters of about 60-80 nm and lengths of about 250-300 nm. The product was confirmed to be a-Fe ₂ 0 ₃ phase by XRD analysis at 33 °, 35.7 °, 53.9. Significant a-Fe ₂ 0 ₃ characteristic peaks were observed at the position.

Preparation of battery positive and negative electrode sheets having the above electrode active material: Same as in Example 1. The negative electrode sheet prepared in this example, the lithium sheet is a positive electrode sheet, PE (polyethylene) is a separator, LiPF ₆ lmol/1 DMC:EC:EMC=1:1:1 is an electrolyte assembled into a button battery 4- A. The battery was subjected to a constant current charge and discharge test. The initial discharge capacity reached 1083 mAh/g at a current density of 0.01 mA/ _{g at a} current density of 0.01 to 3 V. The first charge capacity reached 730 mAh/g, and the charge and discharge cycle was still 50 times. Maintained at 260 mAh/g, the coulombic efficiency of the other cycles is close to 100%, except for the first to second coulombic efficiency.

The positive electrode sheet prepared in this embodiment, the lithium sheet is a negative electrode sheet, and PE (polyethylene) is a separator. LiPF ₆ lmol/1 DMC: EC: EMC=1:1: 1 is assembled into a button battery 4-B. The battery was subjected to a constant current charge-discharge test. The initial discharge capacity reached 206 mAh/g at a current density of 1.5 mA/g at a current range of 1.5-4.5 V, and the first charge capacity was 181 mAh/g. Maintained at 106 mAh/g, the coulombic efficiency at other cycle times is close to 100%, except for the first to second coulombic efficiency.

It is to be understood that the use of these embodiments is merely illustrative of the invention and is not intended to limit the scope of the invention. In addition, it should be understood that various changes, modifications, and/or variations of the invention may be made by those skilled in the art in the appended claims. Within the limits of protection defined.

Claims

claims

1. A method for preparing rod-shaped nano-iron oxide electrode materials, which is characterized in that FeCl ₃ -6H ₂ 0, ammonium dihydrogen phosphate and water are used as raw materials to perform a hydrothermal reaction, and the resulting precipitate is washed to obtain rod-shaped nano-iron oxide. Iron powder.

2. The preparation method according to claim 1, characterized in that the temperature of the hydrothermal reaction is 200-240 °C, and the time of the hydrothermal reaction is 1-10 h. Preferably, the temperature of the hydrothermal reaction is 210-230 °C, and the time of the hydrothermal reaction is 5-6 h.

3. The preparation method according to claim 1, characterized in that the molar ratio of FeCl ₃ «6H ₂ 0 and ammonium dihydrogen phosphate in the raw material is 26: 1-30: 1,

4. The preparation method according to claim 3, characterized in that the molar ratio of FeCl ₃ «6H ₂ 0 and ammonium dihydrogen phosphate in the raw material is 27: 1-28: 1.

5. The preparation method according to claim 1, characterized in that the precipitate is washed with deionized water and alcohol in sequence.

6. A rod-shaped nano-iron oxide electrode material prepared by the method of any one of claims 1-5, characterized in that it is rod-shaped, with an average diameter of 60-80 nanometers, a length of 250-300 nanometers, and a purity of 99.9% Above, the crystal phase is a-Fe ₂ 0 ₃ .

7. The application of the rod-shaped nano-iron oxide electrode material in lithium-ion batteries according to claim 6, characterized in that the rod-shaped nano-iron oxide electrode material serves as the active material of the positive electrode and negative electrode of the lithium-ion battery.

8. The application according to claim 7, characterized in that the specific application method is as follows: Step 1: Add the binder and conductive agent to the above-mentioned rod-shaped nano-iron oxide powder, mix thoroughly by grinding, and then mix After mixing, the slurry is filtered to obtain a uniform pre-coated refined slurry; Step 2: Apply the pre-coated refined slurry to the aluminum foil surface current collector and the copper foil surface current collector respectively, and then dry them to form an active The battery positive electrode sheet and the battery negative electrode sheet are made of materials.

9. The application according to claim 8, characterized in that, in the step one, the mass percentage of the binder, conductive agent and rod-shaped nano-iron oxide powder is: Binder: 10-20% ; Conductive agent: 10-30%; Rod-shaped nano-iron oxide powder: 50-80%. Preferably, binder: 10%; conductive agent: 20%; rod-shaped nano-iron oxide powder: 70%.

10. The application according to claim 8, characterized in that, in the first step, the grinding time is 40-60min; in the second step, the drying temperature is 100-120 °C, drying time is 18-24 h.