Metal organic framework coated iron oxide negative electrode material and preparation method and application thereof

Abstract

The invention relates to the technical field of preparation of a lithium ion battery negative electrode material, in particular to a metal organic framework coating for improving the performance of an iron oxide negative electrode lithium ion battery and a preparation method of the metal organic framework coating. The metal organic framework coating mainly comprises the step of coating the iron oxide by growing a metal organic framework on the surface of the iron oxide in situ. According to the invention, in-situ synthesis of a metal organic framework material on the surface of iron oxide is innovatively proposed, and the iron oxide material is coated in a hollow structure through a structure provided by an organic framework, so that volume expansion and shrinkage of iron oxide in charge and discharge processes are effectively buffered. By regulating and controlling the mass ratio of the organic framework to the ferric oxide, the high-rate discharge performance and the specific discharge capacity of the ferric oxide negative electrode are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of anode materials for lithium-ion batteries, and particularly to a metal-organic framework coating for improving the performance of lithium-ion batteries with iron oxide anodes and a preparation method thereof. Background Art

[0002] Lithium-ion batteries are widely used in portable electronic products, electric vehicles, and a series of energy storage systems due to their high voltage, high specific energy, and ultra-long cycle life. As a key component of lithium-ion batteries, the anode material directly affects the insertion and extraction of lithium ions, battery capacity, the formation of the SEI film, lifespan, and safety. Although commercial graphite anode materials have reached a theoretical capacity of 372 mAh / g, they still cannot meet the requirements of large-scale energy storage infrastructure. Therefore, there is an urgent need for new anode materials for lithium-ion batteries to provide better energy density and cycle stability. In the past few decades, transition metal oxides have attracted great attention from scientists due to their unique properties and potential applications. Among them is iron oxide (Fe2O3), which is one of the most promising choices for anode materials for lithium-ion batteries due to its remarkable theoretical capacity (1007 mAh / g), sustainability, and economy. However, during the charge and discharge process, Fe2O3 has low electrical conductivity and significant volume expansion, resulting in severe capacity attenuation and irreversible electrode polarization during cycling. To solve these problems, a great deal of work has been done to improve the structural integrity and cycle stability of Fe2O3 anode materials. The main methods include creating nanostructures or applying coatings of conductive carbon materials such as amorphous carbon, graphene, and carbon nanotubes. Constructing nanostructures can reduce the volume effect during the charge and discharge process, while increasing electroactive sites and reducing the diffusion distance of lithium ions and electrons. The combination with carbon-based materials significantly improves the electronic conductivity and structural integrity of electroactive materials, enhancing the cycle stability and performance of the electrode at high rates.

[0003] However, although these methods have alleviated the volume expansion problem of Fe2O3 anode materials to a certain extent, they have not fundamentally solved the problems of electrode structure damage and capacity attenuation caused by volume changes during the charge and discharge process. Therefore, this application aims to further optimize the structure of Fe2O3 anode materials by introducing metal-organic framework (MOF)-derived porous materials to significantly reduce its volume expansion effect and improve its cycle stability and electrochemical performance.

[0004] Metal-organic frameworks (MOFs) are self-assembled structures formed by connecting metal ions or metal clusters with organic ligands through coordination bonds. MOFs have characteristics such as high porosity and significant specific surface area, and have been widely used in fields such as catalysis, gas separation, sensors, and energy storage. In recent years, MOFs have been used as a simple and effective method for preparing porous derivatives (including metals, metal sulfides, metal oxides, and their carbon-based composites). The morphology and porous structure of MOF precursors are usually inherited by metal-based derivatives, thereby improving their conductivity and stability for electrochemical purposes. In addition, when used as the anode component of a lithium-ion battery, the MOF-derived porous material not only provides a higher specific surface area and porosity to increase the contact between the electrolyte and the nanomaterial, but also provides more active sites and shorter diffusion paths to accelerate the diffusion of lithium ions.

[0005] This application aims to solve the volume expansion problem of Fe2O3 during charge and discharge by using the MOF-derived porous material as the carrier of the Fe2O3 anode material, thereby improving its cycle stability and electrochemical performance. Specifically, the MOF-derived porous structure can effectively buffer the volume change of Fe2O3 during the insertion and extraction of lithium ions, reduce the damage of the electrode structure, and at the same time improve the conductivity of the electrode and the lithium ion diffusion rate, thereby achieving more stable cycle performance and higher energy density. Summary of the Invention

[0006] In order to overcome the deficiencies of the prior art, a metal-organic framework-coated iron oxide anode material, its preparation method and application are provided. By synthesizing a metal-organic framework on the surface of iron oxide, the volume expansion of iron oxide during charge and discharge can be effectively inhibited, the loss of irreversible capacity can be reduced, and the electrochemical performance of the iron oxide anode can be improved.

[0007] The specific technical solution of the present invention is as follows: A metal-organic framework-coated iron oxide anode material, which is composed of iron oxide nanoparticles and ZIF-67 metal-organic framework. The mass ratio of iron oxide to ZIF-67 is 1:0.5 to 1, and ZIF-67 is uniformly coated on the surface of iron oxide to form a hollow structure, effectively buffering the volume expansion of iron oxide during charge and discharge.

[0008] A preparation method of the metal-organic framework ZIF-67-coated iron oxide anode material, comprising the following steps: (1) performing a leaching reaction on iron concentrate with an acid, with a leaching time of 60 to 300 min and a leaching temperature of 60 to 90 °C, and filtering to obtain a leaching solution; (2) Add a precipitant to the leaching solution. The precipitant is at least one of sodium carbonate, sodium hydroxide, and ammonia water. The reaction temperature is 60 - 90 °C, the reaction time is 2 h, the aging temperature is 60 °C, and the aging time is 4 h to obtain an iron hydroxide precursor; (3) Sinter the iron hydroxide precursor under an argon or nitrogen atmosphere. The sintering temperature is 350 - 500 °C, and the heat preservation time is 2 - 4 h to obtain iron oxide; (4) Mix and stir iron oxide, a cobalt source, 2-methylimidazole, and a methanol solution. The stirring speed is 200 - 400 rpm, and the stirring time is 12 - 24 h to obtain an iron oxide composite material coated with metal-organic framework ZIF-67.

[0009] A lithium-ion battery includes the iron oxide negative electrode material coated with metal-organic framework ZIF-67 described above, a conductive agent, a binder, and an electrolyte. The mass ratio of the negative electrode material, the conductive agent, and the binder is 7:2:1, and the electrolyte is 1M LiPF6 / EC:DMC:EMC (1:1:1).

[0010] The beneficial effects of the present invention: 1) The present invention for the first time uses an iron concentrate leaching solution as an iron source to prepare an iron oxide composite material coated with metal-organic framework ZIF-67. This method has a short process flow, is simple and reliable, has good repeatability, strong operability, and low cost, and is suitable for industrial production. The electrochemical performance of the coated iron oxide is significantly improved, and it has broad development prospects.

[0011] 2) By constructing an iron oxide coated with metal-organic framework ZIF-67, the present invention can improve the electron and lithium-ion transfer rates of the composite material, improve the rate performance of the material, and significantly improve the electrochemical performance.

[0012] 3) In the iron oxide composite material coated with metal-organic framework ZIF-67 of the present invention, iron oxide particles are uniformly coated inside the metal-organic framework, which can effectively buffer the volume expansion of iron oxide during charge and discharge, improve the interface stability between the material and the electrolyte, and greatly improve the structural stability of iron oxide.

[0013] 4) The iron oxide composite material coated with metal-organic framework ZIF-67 of the present invention has the characteristics of high rate performance and long life when applied to the field of lithium-ion secondary batteries. Description of the Drawings

[0014] Figure 1 SEM images of (a) iron oxide and (b) iron oxide coated with metal-organic framework ZIF-67 prepared in the present invention, showing the structure of iron oxide particles uniformly coated in the ZIF-67 framework; Figure 2The long-cycle performance graph of the metal-organic framework ZIF-67 coated with iron oxide prepared in the present invention as the anode material of a lithium-ion battery, showing the discharge specific capacity of the material after 300 cycles at a current density of 500 mA / g; Figure 3 The rate performance graph of the metal-organic framework ZIF-67 coated with iron oxide prepared in the present invention as the anode material of a lithium-ion battery, showing the discharge specific capacity of the material at different current densities. Detailed implementation manners

[0015] The present invention will be further described below in conjunction with the accompanying drawings and embodiments, but the present invention is not limited in any way. Any transformation or substitution based on the teachings of the present invention falls within the protection scope of the present invention.

[0016] A metal-organic framework coated iron oxide anode material, the material consists of iron oxide nanoparticles and the ZIF-67 metal-organic framework, wherein the mass ratio of iron oxide to ZIF-67 is 1:0.5 - 1, and ZIF-67 is uniformly coated on the surface of iron oxide to form a hollow structure.

[0017] A preparation method of the metal-organic framework coated iron oxide anode material described above, comprising the following steps: (1) Leaching reaction is carried out on iron concentrate and acid, the leaching time is 60 - 300 min, the leaching temperature is 60 - 90 °C, and the leaching solution is obtained by filtration; (2) A precipitant is added to the leaching solution, the precipitant is at least one of sodium carbonate, sodium hydroxide, and ammonia water, the reaction temperature is 60 - 90 °C, the reaction time is 2 h, the aging temperature is 60 °C, and the aging time is 4 h to obtain a ferric hydroxide precursor; (3) The ferric hydroxide precursor is sintered in an argon or nitrogen atmosphere, the sintering temperature is 350 - 500 °C, and the holding time is 2 - 4 h to obtain iron oxide; (4) Iron oxide, cobalt source, 2-methylimidazole, and methanol solution are mixed and stirred, the stirring speed is 200 - 400 rpm, and the stirring time is 12 - 24 h to obtain a metal-organic framework ZIF-67 coated iron oxide composite material.

[0018] In step (1), the acid is at least one of sulfuric acid, hydrochloric acid, and nitric acid, and the concentration of the acid is 1 - 3 mol / L.

[0019] In step (2), the precipitant is at least one of sodium carbonate, sodium hydroxide, and ammonia water, and the concentration of the precipitant is 1 - 2 mol / L.

[0020] In step (4), the cobalt source is at least one of cobalt nitrate hexahydrate (Co(NO3)2·6H2O), cobalt chloride (CoCl2), cobalt acetate (Co(CH3COO)2), and cobalt sulfate (CoSO4), and the molar ratio of the cobalt source to 2-methylimidazole is 1:4.

[0021] The material is used as the anode material of a lithium-ion battery, and after 300 cycles at a current density of 500 mA / g, the discharge specific capacity is not less than 500 mAh / g.

[0022] A lithium-ion battery includes the metal-organic framework ZIF-67-coated iron oxide anode material, a conductive agent, a binder, and an electrolyte, wherein the mass ratio of the anode material, the conductive agent, and the binder is 7:2:1, and the electrolyte is 1M LiPF6 / EC:DMC:EMC (1:1:1).

[0023] After 300 cycles of the battery within the voltage range of 0 to 3V at a current density of 500 mA / g, the discharge specific capacity is not less than 500 mAh / g.

[0024] Example 1: Influence of different sintering temperatures on material properties Step 1: Leach iron concentrate with sulfuric acid for 180 min at a leaching temperature of 80 °C, and filter to obtain the leachate.

[0025] Step 2: Add a 1.5 mol / L sodium carbonate solution to the leachate, react at 80 °C for 2 h, age at 60 °C for 4 h to obtain the iron hydroxide precursor.

[0026] Step 3: Sinter the iron hydroxide precursor in an argon atmosphere at sintering temperatures of 400 °C, 450 °C, and 500 °C for 3 h to obtain iron oxides with different sintering temperatures.

[0027] Step 4: Mix and stir iron oxide, cobalt nitrate hexahydrate, 2-methylimidazole, and methanol solution at a stirring speed of 300 rpm for 24 h to obtain the metal-organic framework ZIF-67-coated iron oxide composite.

[0028] Step 5: Mix the above composite with the conductive agent Super P and the binder PVDF in a mass ratio of 7:2:1 to prepare the anode material of a lithium-ion battery.

[0029] Step 6: After 300 cycles at a current density of 500 mA / g, test its discharge specific capacity.

[0030] Results: 1. After cycling 300 times at a current density of 500 mA / g, the discharge specific capacity of the iron oxide-coated material sintered at 400 °C is 720.5 mAh / g; 2. After cycling 300 times at a current density of 500 mA / g, the discharge specific capacity of the iron oxide-coated material sintered at 450 °C is 752.8 mAh / g; 3. After cycling 300 times at a current density of 500 mA / g, the discharge specific capacity of the iron oxide-coated material sintered at 500 °C is 782.9 mAh / g.

[0031] Conclusion: As the sintering temperature increases, the discharge specific capacity of the material gradually increases, and the best performance is achieved at 500 °C.

[0032] Example 2: Influence of different stirring times on the material properties Step 1: Leaching reaction of iron concentrate with hydrochloric acid, leaching time is 120 min, leaching temperature is 70 °C, and the leaching solution is obtained by filtration.

[0033] Step 2: Add 1.2 mol / L sodium hydroxide solution to the leaching solution, reaction temperature is 70 °C, reaction time is 2 h, aging temperature is 60 °C, and aging time is 4 h to obtain iron hydroxide precursor.

[0034] Step 3: Sinter the iron hydroxide precursor in a nitrogen atmosphere, sintering temperature is 500 °C, holding time is 3 h to obtain iron oxide.

[0035] Step 4: Mix and stir iron oxide, cobalt nitrate hexahydrate, 2-methylimidazole and methanol solution, stirring speeds are 200 rpm, 300 rpm and 400 rpm respectively, and stirring times are 12 h, 18 h and 24 h respectively to obtain iron oxide composites coated with metal-organic framework ZIF-67 with different stirring times.

[0036] Step 5: Mix the above composite material with conductive agent Super P and binder PVDF according to a mass ratio of 7:2:1 to prepare the negative electrode material of the lithium-ion battery.

[0037] Step 6: After cycling 300 times at a current density of 500 mA / g, test its discharge specific capacity.

[0038] Results: 1. After cycling 300 times at a current density of 500 mA / g, the discharge specific capacity of the iron oxide-coated material stirred for 12 h is 710.3 mAh / g; 2. After cycling 300 times at a current density of 500 mA / g, the discharge specific capacity of the iron oxide-coated material stirred for 18 h is 745.6 mAh / g; After 300 cycles at a current density of 500 mA / g, the discharge specific capacity of the iron oxide-coated material stirred for 24 h was 782.9 mAh / g.

[0039] Conclusion: As the stirring time increases, the discharge specific capacity of the material gradually increases and reaches the best performance at 24 h.

[0040] Example 3: Influence of different cobalt sources on the material properties Step 1: Leaching reaction of iron concentrate with nitric acid for 240 min at a leaching temperature of 90 °C, followed by filtration to obtain the leaching solution.

[0041] Step 2: Add 1 mol / L ammonia water solution to the leaching solution, react at 90 °C for 2 h, age at 60 °C for 4 h to obtain the iron hydroxide precursor.

[0042] Step 3: Sinter the iron hydroxide precursor in an argon atmosphere at a sintering temperature of 500 °C for 3 h to obtain iron oxide.

[0043] Step 4: Mix and stir iron oxide, different cobalt sources (cobalt nitrate hexahydrate, cobalt chloride, cobalt acetate, cobalt sulfate), 2-methylimidazole and methanol solution at a stirring speed of 300 rpm for 24 h to obtain iron oxide composites coated with metal-organic framework ZIF-67 with different cobalt sources.

[0044] Step 5: Mix the above composite material with conductive agent Super P and binder PVDF according to a mass ratio of 7:2:1 to prepare the anode material for lithium-ion batteries.

[0045] Step 6: After 300 cycles at a current density of 500 mA / g, test its discharge specific capacity. Results: 1. After 300 cycles at a current density of 500 mA / g, the discharge specific capacity of the iron oxide-coated material using cobalt nitrate hexahydrate was 782.9 mAh / g; 2. After 300 cycles at a current density of 500 mA / g, the discharge specific capacity of the iron oxide-coated material using cobalt chloride was 765.4 mAh / g; 3. After 300 cycles at a current density of 500 mA / g, the discharge specific capacity of the iron oxide-coated material using cobalt acetate was 750.2 mAh / g; 4. After 300 cycles at a current density of 500 mA / g, the discharge specific capacity of the iron oxide-coated material using cobalt sulfate was 735.8 mAh / g.

[0046] Conclusion: Different cobalt sources have a certain impact on the material properties. When cobalt nitrate hexahydrate is used as the cobalt source, the discharge specific capacity of the material is the highest.

[0047] Example 4: Influence of different mass ratios of iron oxide to ZIF-67 on material properties Step 1: Leach iron concentrate with sulfuric acid. The leaching time is 180 min, and the leaching temperature is 80 °C. Filter to obtain the leaching solution.

[0048] Step 2: Add a 1.5 mol / L sodium carbonate solution to the leaching solution. The reaction temperature is 80 °C, the reaction time is 2 h, the aging temperature is 60 °C, and the aging time is 4 h to obtain an iron hydroxide precursor.

[0049] Step 3: Sinter the iron hydroxide precursor in an argon atmosphere. The sintering temperature is 500 °C, and the holding time is 3 h to obtain iron oxide.

[0050] Step 4: Mix iron oxide with ZIF-67 at mass ratios of 0.5:1, 0.7:1, and 0.9:1. Mix cobalt nitrate hexahydrate, 2-methylimidazole, and methanol solution and stir at a stirring speed of 300 rpm for 24 h to obtain iron oxide composites coated with metal-organic framework ZIF-67 with different mass ratios.

[0051] Step 5: Mix the above composite materials with conductive agent Super P and binder PVDF at a mass ratio of 7:2:1 to prepare the anode material for lithium-ion batteries.

[0052] Step 6: After cycling 300 times at a current density of 500 mA / g, test its discharge specific capacity. Results: 1. When the mass ratio of iron oxide to ZIF-67 is 0.5:1, the discharge specific capacity is 782.9 mAh / g; 2. When the mass ratio of iron oxide to ZIF-67 is 0.7:1, the discharge specific capacity is 742.3 mAh / g; 3. When the mass ratio of iron oxide to ZIF-67 is 0.9:1, the discharge specific capacity is 538.4 mAh / g.

[0053] Conclusion: As the proportion of ZIF-67 increases, the discharge specific capacity of the material gradually decreases. When the mass ratio is 0.5:1, the discharge specific capacity reaches the highest at 782.9 mAh / g.

Claims

1. A metal-organic framework-coated iron oxide anode material, characterized in that, The material consists of iron oxide nanoparticles and ZIF-67 metal-organic framework, where the mass ratio of iron oxide to ZIF-67 is 1:0.5 - 1, and ZIF-67 uniformly coats the surface of iron oxide, forming a hollow structure.

2. The preparation method of the iron oxide-coated anode material with metal-organic framework according to claim 1, characterized in that, It includes the following steps: Perform a leaching reaction on iron concentrate and acid for 60 - 300 min at a leaching temperature of 60 - 90 °C, and filter to obtain a leaching solution. (2) Add a precipitant to the leaching solution. The precipitant is at least one of sodium carbonate, sodium hydroxide, and ammonia water. The reaction temperature is 60 - 90 °C, the reaction time is 2 h, the aging temperature is 60 °C, and the aging time is 4 h to obtain an iron hydroxide precursor. (3) Sinter the iron hydroxide precursor in an argon or nitrogen atmosphere at a sintering temperature of 350 - 500 °C for a holding time of 2 - 4 h to obtain iron oxide. (4) Mix and stir iron oxide, a cobalt source, 2-methylimidazole, and a methanol solution at a stirring speed of 200 - 400 rpm for 12 - 24 h to obtain an iron oxide composite material coated with metal-organic framework ZIF-67.

3. The preparation method according to claim 2, wherein In step (1), the acid is at least one of sulfuric acid, hydrochloric acid, and nitric acid, and the concentration of the acid is 1 - 3 mol / L.

4. The preparation method according to claim 2, wherein In step (2), the precipitant is at least one of sodium carbonate, sodium hydroxide, and ammonia water, and the concentration of the precipitant is 1 - 2 mol / L.

5. The preparation method according to claim 2, wherein In step (4), the cobalt source is at least one of cobalt nitrate hexahydrate, cobalt chloride, cobalt acetate, and cobalt sulfate, and the molar ratio of the cobalt source to 2-methylimidazole is 1:

4.

6. The metal-organic framework ZIF-67-coated iron oxide negative electrode material according to any one of claims 1 to 5, characterized in that The material is used as a negative electrode material for a lithium-ion battery, and after cycling 300 times at a current density of 500 mA / g, the discharge specific capacity is not less than 500 mAh / g.

7. A lithium-ion battery, characterized in that, It includes the negative electrode material of iron oxide coated with metal-organic framework ZIF-67 as claimed in claim 1, a conductive agent, a binder, and an electrolyte. The mass ratio of the negative electrode material, the conductive agent, and the binder is 7:2:1, and the electrolyte is 1M LiPF6 / EC:DMC:EMC (1:1:1).

8. The lithium ion battery according to claim 7, characterized in that, After the battery cycles 300 times at a current density of 500 mA / g in the voltage range of 0 - 3V, the discharge specific capacity is not less than 500 mAh / g.

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