阅读说明：本技术 一种用废弃磷酸铁锂电池合成磷酸铁和氧化铁薄膜的方法 (Method for synthesizing iron phosphate and iron oxide film by using waste lithium iron phosphate battery ) 是由 杨晓刚 梅婉婉 仝玉萍 张振 叶壮 李品将 雷岩 郑直 吴其华 葛德培 于 2019-10-16 设计创作，主要内容包括：本发明提供一种用废弃磷酸铁锂电池合成磷酸铁和氧化铁薄膜的方法,包括以下步骤：拆解电池,分离铜箔、铝箔、正极材料磷酸铁锂及负极材料石墨；用草酸、双氧水溶解磷酸铁锂材料,得到浸出液A；以浸出液A、去离子水及乙二醇作为前驱体,经调节pH后,采用水热法在经清洗过的FTO导电玻璃衬底上沉积得到磷酸铁薄膜；再经退火,即得到氧化铁薄膜。本发明采用水热法一步得到目标产物磷酸铁薄膜,退火后成为氧化铁薄膜,用于光电分解水制氢,具有环境友好、节能省时、设备简易、操作简便,且得到的目标产物电化学活性高；工艺简单可控,适用于规模化生产等优点。(The invention provides a method for synthesizing iron phosphate and iron oxide films by using waste lithium iron phosphate batteries, which comprises the following steps of: disassembling the battery, and separating the copper foil, the aluminum foil, the positive electrode material lithium iron phosphate and the negative electrode material graphite; dissolving the lithium iron phosphate material with oxalic acid and hydrogen peroxide to obtain a leaching solution A; taking the leachate A, deionized water and ethylene glycol as precursors, and depositing on a cleaned FTO conductive glass substrate by a hydrothermal method after adjusting the pH value to obtain an iron phosphate film; and annealing to obtain the iron oxide film. According to the invention, a target product iron phosphate film is obtained in one step by adopting a hydrothermal method, and the iron phosphate film becomes an iron oxide film after annealing, is used for preparing hydrogen by photoelectric decomposition of water, and has the advantages of environmental friendliness, energy and time conservation, simple equipment and simplicity and convenience in operation, and the obtained target product has high electrochemical activity; simple and controllable process, suitability for large-scale production and the like.)

1. A method for synthesizing iron phosphate and iron oxide films by using waste lithium iron phosphate batteries is characterized by comprising the following steps:

1) disassembling the battery, and separating the copper foil, the aluminum foil, the positive electrode material lithium iron phosphate and the negative electrode material graphite;

2) dissolving the lithium iron phosphate material with oxalic acid and hydrogen peroxide to obtain a leaching solution A;

3) taking the leachate A, deionized water and ethylene glycol as precursors, and depositing on a cleaned FTO conductive glass substrate by a hydrothermal method after adjusting the pH value to obtain an iron phosphate film; and annealing to obtain the iron oxide film.

2. The method for synthesizing the iron phosphate and the iron oxide film by using the waste lithium iron phosphate batteries through hydrothermal reaction according to claim 1, wherein the molar ratio of the oxalic acid to the hydrogen peroxide to the lithium iron phosphate in the step 2) is 1-4: 5:1, the treatment temperature is 60-90 ℃, and the time is more than 2 hours.

3. The method for hydrothermally synthesizing iron phosphate and iron oxide films by using the waste lithium iron phosphate batteries according to claim 1, wherein the cleaning process of the FTO conductive glass substrate in the step 3) is as follows: the method comprises the steps of respectively ultrasonically washing a mixture of hydrogen peroxide, ammonia water and distilled water in a volume ratio of 1:1:1 for 2-3 hours, naturally drying in the air to obtain a dry and clean FTO conductive glass substrate, and then placing the FTO conductive glass substrate in 0.2mol/L potassium dihydrogen phosphate solution at 60 ℃ for 2 hours.

4. The method for synthesizing the iron phosphate and iron oxide film by using the waste lithium iron phosphate battery in a hydrothermal mode according to claim 1, wherein the volume ratio of the leaching solution A, the deionized water and the glycol in the step 3) is 1/x/(1+ x), wherein x is 1-9, the pH of the obtained precursor solution is adjusted to 1-6.5 by using oxalic acid or deionized water, and the precursor solution is kept in an oven at 100-190 ℃ for 0.5-120 h.

5. The method for hydrothermally synthesizing the iron phosphate and iron oxide thin film by using the waste lithium iron phosphate battery according to claim 1, wherein the annealing reaction temperature of the iron phosphate thin film in the step 3) is 750-800 ℃, and the annealing time is 5-30 min.

Technical Field

The invention belongs to the technical field of inorganic non-metallic material manufacturing, and particularly relates to a method for synthesizing iron phosphate and iron oxide films by using waste lithium iron phosphate batteries.

Background

With the invention and wide application of the battery, a lot of waste batteries are generated while the life and work of people become convenient, and if the waste batteries are not properly treated or stacked anywhere, soil, water sources and the like can be polluted. In addition, due to the shortage of fossil energy, the application of batteries, particularly lithium ion secondary batteries, is becoming more widespread.

Since the commercialization of the lithium ion battery was realized in the last 90 years, the lithium ion battery has the advantages of high working voltage, high energy density, long cycle life, low self-discharge rate, environmental protection, no memory effect and the like, is widely applied to the fields of mobile phones, portable computers, electronic toys and the like, and is rapidly expanding to the fields of electric vehicles, electric automobiles and energy storage devices. Wherein, lithium iron phosphate LiFePO₄The material has the advantages of rich raw material source, low price, no toxicity, high theoretical capacity, good thermal stability, good cycle performance and the like, so the material is a very safe anode material and is generally applied to electric vehicles, new energy vehicles and emergency lamps.

In the recovery of the anode material of the waste lithium ion battery, there are two main approaches at present: (1) the anode material is leached out, and then the separated metal or metal precipitate is gradually recovered. Patent 201611136854.8 discloses a method for treating waste material of positive electrode material of lithium battery, which comprises the following steps: roasting A, acidifying B and leaching (inorganic acid: nitric acid, hydrochloric acid and sulfuric acid), removing iron and aluminum, removing copper and zinc, fluorinating E and precipitating lithium, removing calcium and magnesium by F, extracting G in multiple stages, removing oil by H, and the like. However, the use of a large amount of inorganic acid not only causes danger in the operation process, but also easily causes secondary pollution. Patent 201810055764.9 leaches through using oxalic acid solution, and then separates out the oxalate through cooling and filters, obtains oxalate and filtrating, and the filtrating recycles to make other impurity ion not introduced at the in-process of preparation, the oxalate purity of preparation is high, the crystallinity is good and the granularity is controllable, has realized the cyclic utilization of resource. (2) After the anode material is leached, metal salt is added to adjust the stoichiometric ratio, and the anode material is obtained again, the method disclosed in the patent 201611247446.X is that after the content of metal elements in the recovered anode material is detected, the metal elements are supplemented to a preset value, and the regenerated anode material is obtained by calcining. The method has complex process, and the electrochemical energy can hardly reach the quality of the commercialized lithium iron phosphate material.

The methods do not well explore the value of the waste lithium batteries, and if the waste lithium battery anode materials can be used for preparing other functional materials, the value of the waste lithium battery anode materials is multiplied. For example, hydrogen is currently a well-known clean energy source due to energy shortage, and hydrogen is produced by photoelectric decomposition of water, and research is once hot. With the heavy use of fossil fuels, not only global resources are in short supply, but also environmental pollution is caused, and the hydrogen production by decomposing water by using solar light can simultaneously alleviate the two problems.

Noble metal based electrocatalysts (e.g. Pt, RuO)₂And IrO₂) Are considered the most advanced OER and HER catalysts due to their excellent catalytic activity. The high manufacturing costs of noble metal catalysts have largely limited their mass production. Therefore, it is of great importance to research inexpensive electrocatalysts. Sunpihai et al (adv. Funct. Mater.2018,1801397) hydrothermally reacted with FeCl₃And triphenyl sodium phosphate as a precursor to prepare iron phosphate Fe at 190 DEG C₂PO₅Octahedron, the catalyst after nitrogen doping has higher activity of oxidizing water. Waste in a wide range of applicationsThe preparation of the electrocatalytic and photoelectrocatalysis material with excellent performance by a one-step method by using the discarded lithium iron phosphate as a raw material obviously has obvious application value. However, a method for hydrothermally synthesizing iron phosphate and iron oxide thin films by using waste lithium iron phosphate batteries has not been reported.

Disclosure of Invention

The invention aims to provide a method for synthesizing iron phosphate and iron oxide films by using waste lithium iron phosphate batteries, which is characterized in that oxalic acid is adopted to leach lithium iron phosphate in the waste lithium iron phosphate batteries to obtain an iron-containing precursor solution, the purpose of controlling the morphology is achieved by adjusting the composition of the precursor solution, a target product iron phosphate film is obtained by one step by adopting a hydrothermal method, and the iron oxide film is formed after annealing and is used for preparing hydrogen by photoelectrolysis of water, so that the method is environment-friendly, energy-saving, time-saving, simple in equipment and convenient to operate, and the obtained target product has high electrochemical activity; simple and controllable process, suitability for large-scale production and the like.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a method for synthesizing iron phosphate and iron oxide films by using waste lithium iron phosphate batteries comprises the following steps:

1) disassembling the battery, and separating the copper foil, the aluminum foil, the positive electrode material lithium iron phosphate and the negative electrode material graphite;

2) dissolving the lithium iron phosphate material with oxalic acid and hydrogen peroxide to obtain a leaching solution A;

3) taking the leachate A, deionized water and ethylene glycol as precursors, and depositing on a cleaned FTO conductive glass substrate by a hydrothermal method after adjusting the pH value to obtain an iron phosphate film; and annealing to obtain the iron oxide film.

According to the scheme, the molar ratio of the oxalic acid to the hydrogen peroxide to the lithium iron phosphate in the step 2) is 1-4: 5:1, the treatment temperature is 60-90 ℃, and the treatment time is more than 2 hours.

According to the scheme, the cleaning process of the FTO conductive glass substrate in the step 3) comprises the following steps: the method comprises the steps of respectively ultrasonically washing a mixture of hydrogen peroxide, ammonia water and distilled water in a volume ratio of 1:1:1 for 2-3 hours, naturally drying in the air to obtain a dry and clean FTO conductive glass substrate, and then placing the FTO conductive glass substrate in 0.2mol/L potassium dihydrogen phosphate solution at 60 ℃ for 2 hours.

According to the scheme, the volume ratio of the precursor liquid in the step 3) to the leachate A, deionized water and glycol is 1/x/(1+ x), wherein x is 1-9, oxalic acid or deionized water is used for adjusting the pH value to 1-6.5, and the solution is kept in an oven at 100-190 ℃ for 0.5-120 h.

According to the scheme, the annealing reaction temperature of the ferric phosphate film in the step 3) is 750-800 ℃, and the annealing time is 5-30 min.

The invention has the beneficial effects that:

1) according to the method, the waste lithium battery cathode material is dissolved by using the organic acid at a low temperature, the condition is mild, secondary pollution is not easy to cause, the acid proportion is accurately calculated, and waste and environmental pollution are avoided;

2) the method adopts a hydrothermal method for deposition, is simple to operate, consumes less energy, and can control a target product by controlling the composition of a precursor;

3) the method has the advantages of simple equipment, simple operation, low cost, environmental protection, good (photoelectric) performance of the obtained product, simple and controllable process and suitability for large-scale production.

Drawings

FIG. 1 is a UV-vis diagram of an iron phosphate thin film in example 1 of the present invention;

FIG. 2 is an XRD pattern of an iron phosphate thin film in example 1 of the present invention;

FIG. 3 is a Raman diagram of an iron phosphate thin film in example 1 of the present invention;

FIG. 4 is an SEM photograph of an iron phosphate thin film in example 1 of the present invention;

FIG. 5 is an SEM photograph of an iron phosphate thin film in example 2 of the present invention;

FIG. 6 is an SEM photograph of an iron phosphate thin film in example 3 of the present invention;

FIG. 7 is an SEM photograph of an iron phosphate thin film in example 4 of the present invention;

FIG. 8 is an SEM photograph of an iron phosphate thin film in example 5 of the present invention;

FIG. 9 is an EDS diagram of an iron phosphate thin film in example 1 of the present invention;

FIG. 10 is an SEM photograph of an iron oxide thin film in example 1 of the present invention;

FIG. 11 is an EDS diagram of an iron oxide thin film in example 1 of the present invention;

FIG. 12 is a Raman graph of an iron oxide thin film in example 1 of the present invention;

FIG. 13 is a J-V diagram of an iron phosphate thin film in example 1 of the present invention;

FIG. 14 is a J-V diagram of an iron oxide film in example 1 of the present invention.

Detailed Description

The chemical reagents used in this example were all analytically pure and purchased from shanghai pharmaceutical reagents company or shenzhen kojiu crystal company. Lithium iron phosphate batteries were purchased from Shenzhen (Delipow 14500). The product of the embodiment adopts the following characterization means: the confocal Raman microscope (Renyao InViaReflex) is used for judging the characteristic vibration of the crystal of a sample, a field emission scanning electron microscope (FEI Nova NanoSEM 450) is used for analyzing the appearance and the size of the film, an X-ray diffractometer (Bruker D8Advance, copper target) is used for verifying that the crystal structure of the film is ferric oxide, an X-ray photoelectron spectrometer (Sammer Feishilab 250Xi) is used for verifying the surface chemical composition of the film, an ultraviolet diffuse reflection spectrum (Agilent Cary 5000) is used for representing the visible light absorption performance of the film, an atomic force microscope (Bruker Dimension Icon) is used for verifying the film structure, and a light current-voltage curve is used for verifying the performance of the photoelectrode.

The technical solution of the present invention is described below with reference to the accompanying drawings and examples.