CN115159852B

CN115159852B - Preparation method and application of iron phosphate microcrystalline glass electrode material

Info

Publication number: CN115159852B
Application number: CN202210583139.8A
Authority: CN
Inventors: 赵杰杰; 李成俊; 吕实琛; 刘世权
Original assignee: Qilu University of Technology
Current assignee: Qilu University of Technology
Priority date: 2022-05-25
Filing date: 2022-05-25
Publication date: 2023-10-03
Anticipated expiration: 2042-05-25
Also published as: CN115159852A

Abstract

The application discloses a preparation method and application of an iron phosphate microcrystalline glass electrode material, and belongs to the field of preparation of anode materials of lithium ion batteries. The method comprises the following steps: step 1: fePO is added to the mixture ₄ ·2H ₂ And (3) drying the raw material O, melting at a high temperature to obtain a melt, and then carrying out water quenching and drying to obtain the mother glass. Step 2: and carrying out heat treatment on the parent glass according to the glass transition temperature and the glass crystallization peak temperature in the DTA curve of the parent glass to obtain the crystallization glass. Step 3: grinding devitrified glass, mixing with acetylene black and PVDF, adding dispersant, mixing thoroughly, scraping onto aluminum foil, and vacuum drying to obtain standard pole piece. The lithium ion battery anode material prepared by the method has the advantages of simple process operation, environmental friendliness and easiness in realizing large-scale industrial production. Meanwhile, due to the unique open network structure of the glass matrix, the FePO of the iron phosphate can be relieved ₄ Volume change of the microcrystalline glass positive electrode material in the electrochemical circulation process greatly improves the transmission rate of lithium ions and the circulation stability of the electrode.

Description

Preparation method and application of iron phosphate microcrystalline glass electrode material

Technical Field

The application relates to the field of preparation of lithium ion battery electrode materials, in particular to a preparation method and application of an iron phosphate microcrystalline glass electrode material.

Background

With the exhaustion of non-renewable energy sources, lithium ion batteries are widely applied to the fields of electronic devices, hybrid electric vehicles and energy grids due to the portability, reversible charge and discharge and cleaning performance. With the development of social economy, higher requirements are put on the safety and stability, energy density and cycle life of lithium ion batteries. Firstly, the supply of raw materials, particularly the storage of the earth crust of lithium, iron and cobalt, which are metals involved in lithium ion batteries, is low in price, and in recent years price fluctuations are large. In order to solve these problems, designing a new electrode material having high electrochemical reaction power and long cycle life is a goal pursued by practical industrial production.

Ferric phosphate FePO of olivine structure ₄ The lithium ion battery anode material has the characteristics of higher lithium ion storage capacity (178 mAh/g), environmental friendliness and low price, and becomes a candidate material of the reversible lithium ion battery anode material. Iron phosphate FePO ₄ The synthesis method includes solid phase reaction method, hydrothermal method, sol-gel method, high temperature-water quenching method, etc. Obtaining the ferric phosphate FePO by adopting a high-temperature water quenching method ₄ The microcrystalline glass has simple process operation and is easy to realize large-scale industrial production. Phosphate glass mainly contains P ₂ O ₅ P of (C) ₂ O ₅ Is a glass network forming body capable of forming glass alone, and has a basic structural unit of [ PO ] ₄ ]Tetrahedrons are connected together through oxygen ions. Since phosphorus has a chemical valence state of +5, one of the tetrahedra is present with P ⁵⁺ Non-bridging oxygens linked by double bonds, such that [ PO ₄ ]The bridging oxygens in the tetrahedra can only be combined with the other three [ PO ] ₄ ]The whole body is shared. Pure P ₂ O ₅ Glass has poor chemical stability, but the structural properties of the glass can be improved by doping with other oxides. For Fe-P binary system glass, fe is added under annealing condition ₂ O ₃ -P ₂ O ₅ Fe in glass ₂ O ₃ The maximum molar content of (2) is 50mol%. The porous microstructure of the glass is easy to introduce lithium ions into and release from the glass in the electrochemical reaction process of the glass serving as an electrode of a lithium ion battery.

In this report, the experiment used FePO ₄ ·2H ₂ O is used as a raw material, and FePO is prepared by a melt-water quenching-heat treatment method ₄ Microcrystalline glass in a crystalline phase. The unique open network structure of the glass matrix can relieve iron phosphate FePO ₄ The volume change of the positive electrode material in the electrochemical circulation process is beneficial to improving the transmission rate of lithium ions and the circulation stability of the electrode.

Disclosure of Invention

The application aims at the defects of the prior electrode materials and techniques, the applicationThe application aims to provide a preparation method and application of an iron phosphate electrode material, and FePO-containing electrode material prepared by the method ₄ The microcrystalline glass with the crystalline phase has simple process operation and environment-friendly property, and is easy to realize large-scale industrial production. The prepared material also has excellent lithium storage performance, and the open network structure of the glass matrix in the material can relieve the FePO of iron phosphate ₄ The volume change of the nanocrystalline material in the electrochemical circulation process greatly improves the transmission rate of lithium ions and the circulation stability of the electrode.

In order to solve the problems, the scheme provided by the application is as follows:

the application provides an iron phosphate microcrystalline glass electrode material which is characterized by comprising the following steps of:

step 1: a certain amount of FePO ₄ ·2H ₂ The raw material O is dried for 12-24 hours at the temperature of 100-140 ℃, then is put into an alumina crucible, is placed into a muffle furnace, is heated to 1000-1200 ℃ at the heating rate of 8-10 ℃/min, is insulated for 1-2 hours, is taken out at high temperature by using a crucible tongs, is directly poured into tap water, is rapidly cooled, and is dried for 12-24 hours at the temperature of 60-80 ℃ to obtain parent glass.

Step 2: grinding a certain amount of the mother glass in the step 1 into a sample with 120-140 meshes, performing a DTA test on the sample by using an HCT-4 type comprehensive thermal analyzer to obtain a DTA curve of the mother glass, heating the mother glass to the glass transition temperature at a heating rate of 8-10 ℃/min for 1-2 hours, continuously heating the mother glass to the first crystallization peak temperature (or 20 ℃ higher than the first crystallization peak temperature of the glass) for 1-2 hours, and cooling the mother glass along with a furnace to obtain the crystallization glass.

Step 3: grinding a certain amount of devitrified glass in the step 2 until no obvious granular sensation exists, then placing the mixture into a mortar, mixing the mixture with acetylene black and PVDF according to the mass ratio of (6-8) to (3-1) to 1 for 30-60 minutes, then placing the uniformly mixed sample into a miniature transparent reagent bottle with a magneton, adding 1-1.5ml of polyvinylpyrrolidone or a mixed solution dispersing agent of absolute ethyl alcohol and water, stirring and mixing on a magnetic stirrer for 12-18 hours, dripping the mixture on an aluminum foil after full mixing, uniformly scraping the sample from the head to the tail at one time by using a scraper with the height of 100-150um, uniformly spreading the sample on the aluminum foil, and drying the scraped aluminum foil for 12-14 hours under the vacuum condition of 80-100 ℃ to obtain a battery pole piece.

Preferably, the raw material is dried at 100-140 ℃ for 12-24 hours, preferably 140 ℃ for 12 hours, the preferable high-temperature melting process is heated to 1000-1200 ℃ at a heating rate of 8-10 ℃/min, and is kept at the temperature for 1-2 hours, preferably to 1150 ℃ at a heating rate of 10 ℃/min, and is kept at the temperature for 1 hour, preferably, the water quenching glass is dried at 60-80 ℃ for 12-24 hours, preferably 80 ℃, for 12 hours, preferably, the heat treatment system is heated to the glass transition temperature thereof at a heating rate of 8-10 ℃/min for 1-2 hours, then the heat treatment is continued until the temperature reaches the first crystallization peak temperature (or is higher than the first crystallization peak temperature of glass by 20 ℃) for 1-2 hours, preferably, the heat treatment is continued until the temperature reaches the first crystallization peak temperature (or is higher than the first crystallization peak temperature of glass by 20 ℃) for 1 hour. Preferably, the mass mixing ratio of the sample to the acetylene black and PVDF is (6-8): (3-1): 1, and the mixture is ground and mixed in a mortar for 30-60 minutes, preferably 7:2:1, mixing for 30 minutes, preferably, the dispersing agent is polyvinylpyrrolidone or a mixed solution of absolute ethyl alcohol and water, the adding amount is about 1-1.5ml, the stirring time is 12-18 hours, preferably polyvinylpyrrolidone, 1.25ml,12 hours, preferably, the gap height of the scraper is 100-150um, preferably, the vacuum drying system is: the drying temperature is 80-100deg.C, and the drying time is 12-14 hr, preferably 80 deg.C, and 12 hr.

Compared with the prior art, the application has the beneficial effects that:

the phosphate prepared by the application has good crystallization performance as a lithium ion battery anode material, and experiments show that FePO ₄ ·2H ₂ The crystalline phases of the O devitrified glass samples are all FePO ₄ . FePO by XRF analysis ₄ ·2H ₂ The element of the O sample is mainly Fe ₂ O ₃ And P ₂ O ₅ And the main crystal phase in XRD analysis is FePO ₄ And are consistent. Meanwhile, the scanning electron microscope image shows uniformly distributed granular crystals. The lithium ion button type half cell assembled by the material and taking the lithium sheet as the counter electrode has lower alternating current impedance and good electronic conductivity, and the specific charge-discharge capacity is stabilized at 103mAh g ^-1 And the material has good cycle performance, and the cyclic voltammetry test shows that the material has good reversible charging and discharging properties. In addition, the preparation method is simple, easy to operate and easy to realize industrialized popularization and commercial application.

Drawings

FIG. 1 is a DTA curve of iron phosphate glass.

Figure 2 is an XRD pattern of iron phosphate glass after various heat treatments.

Fig. 3 is a scanning electron microscope image of a different heat treatment of the iron phosphate glass.

Fig. 4 is an ac impedance plot of assembled batteries using different heat treated materials of iron phosphate glass.

Fig. 5 is a graph of constant current charge and discharge test performance of assembled batteries using different heat treated materials of iron phosphate glass.

Fig. 6 is a cyclic voltammetry test plot for an assembled battery using an iron phosphate glass material.

Detailed Description

In order to make the material and technical problems, technical solutions and advantages to be solved by the present application more apparent, the following detailed description will be made with reference to the accompanying drawings and specific embodiments.

In order to enable those skilled in the art to more clearly understand the technical scheme of the present application, the technical scheme of the present application will be described in detail with reference to specific embodiments. If experimental details are not specified in the examples, the conditions are generally conventional or recommended by the reagent company; reagents, consumables, etc. used in the examples described below are commercially available unless otherwise specified.

The application provides a preparation method and application of an iron phosphate microcrystalline glass electrode material, and specific examples are as follows.

Example 1

A preparation method of an iron phosphate microcrystalline glass electrode material comprises the following steps:

1. preparation of parent glass

A certain amount of FePO ₄ ·2H ₂ And (3) drying the O raw material at 140 ℃ for 12 hours, putting the O raw material into an alumina crucible, putting the alumina crucible into a muffle furnace, heating to 1150 ℃ at a heating rate of 10 ℃/min, preserving heat for 1 hour, taking out the O raw material at a high temperature by using a crucible tongs, directly pouring the O raw material into tap water, rapidly cooling the O raw material to obtain water quenched glass, and drying the obtained water quenched glass at 80 ℃ for 12 hours to obtain parent glass.

2. Preparation of devitrified glass

Grinding a certain amount of the mother glass in the step 1 into a sample with 120-140 meshes, performing a DTA test on the sample by using an HCT-4 type comprehensive thermal analyzer to obtain a DTA curve of the mother glass, heating the mother glass to the glass transition temperature of 495 ℃ at the heating rate of 10 ℃/min for 1 hour, continuously heating to the first crystallization peak temperature of 560 ℃ for 1 hour, and cooling the mother glass in a furnace to obtain the crystallization glass.

3. Preparation of pole piece

Grinding a certain amount of devitrified glass in the step 2 until no obvious granular feel exists, then weighing 57.14 mg of acetylene black and 28.57 mg of PVDF with corresponding mass respectively according to the mass ratio of the sample to the acetylene black and the PVDF of 7:2:1 by taking 200 mg of the sample as a reference, and fully mixing the sample, the acetylene black and the PVDF in a mortar for 30 minutes. After completion of the mixing, the mixture was placed in a micro-transparent reagent bottle with a magnet and 1.25ml of NMP was added as a dispersing agent, followed by stirring on a magnetic stirrer for 12 hours. The evenly stirred and mixed sample is dripped on the aluminum foil, and the sample is scraped from the head to the tail evenly by a scraper with 150um at one time, so that the sample is evenly paved on the aluminum foil. And then placing the aluminum foil into a vacuum drying oven at 80 ℃ and drying for 12 hours to obtain the battery pole piece.

Example 2

A method for simply controlling and synthesizing an iron phosphate lithium ion battery anode material comprises the following steps:

1. preparation of parent glass

2. Preparation of devitrified glass

Grinding a certain amount of the mother glass in the step 1 into a sample with 120-140 meshes, performing a DTA test on the sample by using an HCT-4 type comprehensive thermal analyzer to obtain a DTA curve of the mother glass, then heating the mother glass to the glass transition temperature of 495 ℃ at the heating rate of 10 ℃/min for 1 hour, then continuously heating to the temperature of 580 ℃ which is 20 ℃ higher than the first crystallization peak temperature of the glass for 1 hour, and cooling the mother glass along with a furnace to obtain the crystallization glass.

3. Preparation of pole piece

The iron phosphate lithium ion battery positive electrode material pole piece obtained according to the embodiment 1-2 is used as a lithium ion battery positive electrode, and the specific application method is as follows:

the pole pieces of the anode materials of the iron phosphate lithium ion battery prepared in the examples 1-2 are assembled in sequence in a glove box according to the sequence of a cathode shell, a pole piece, an electrolyte, a diaphragm, a lithium piece, a gasket, a spring gasket and an anode shell. After the assembly is completed, each battery is sealed in a sealing bag and then taken out of the glove box, so that the battery is prevented from being contacted with air. (the glove box is always in pure argon atmosphere, the glove is worn in the whole process in the assembling process, tweezers are used for operation, a pole piece, a diaphragm, a lithium piece, a gasket, a spring gasket and dropwise adding electrolyte are used for enabling the gasket and the spring gasket to be located at the middle position as far as possible, the adding amount of the electrolyte is 70 ul), the assembled half battery is punched and sealed by using a manual sealing machine, and the model of the manual sealing machine is MSK-160D. And then standing for more than 12 hours, and performing battery performance tests including alternating current impedance tests, charge and discharge tests and cyclic voltammetry tests.

And (5) selecting an A602-3008W-3UIF-B battery charge and discharge tester for charge and discharge testing. The test voltage is 0.01-3.0V.

A Parstat 2263 electrochemical workstation was used for Cyclic Voltammetry (CV) curve and AC impedance testing. The frequency of the test range of the alternating current impedance is 10mHz-100kHz, and the cyclic volt-ampere test voltage interval is 1.8-4.2V.

Characterization of the prepared iron phosphate lithium ion battery anode material and application of the prepared iron phosphate lithium ion battery anode material are shown in the attached drawing

Comparative example 1

In example 2, only the first crystallization peak temperature at the time of heat treatment of the mother glass was changed, and the other conditions were the same as in example 1.

XRD test results of samples of the iron phosphate microcrystalline glass prepared by the application after different heat treatments show that the main crystal phases of the samples are FePO ₄ The scanning electron microscope image test result shows that the precipitated crystals of the sample are similar to the structures of plant cell walls at 560 ℃, the glassy substances are more, and the precipitated crystals are uniformly distributed in the form of particles at 580 ℃. As shown in fig. 3 (left panel is 560 ℃ C. Sample, right panel is 580 ℃ C. Sample morphology). The alternating current impedance test result of the prepared battery shows that: the impedance of the sample is slightly less than 580 ℃ when the sample is heat treated at 560 ℃, that is to say, the lithium ion conductivity of the sample is higher than that of the sample which is subjected to high-temperature crystallization at 580 ℃ than that of the sample which is subjected to high-temperature crystallization at 560 DEG CThe height of the treated sample. The constant current charge and discharge test results show that: discovery of FePO ₄ ·2H ₂ The specific charge-discharge capacity of the O sample is stabilized at 103mAhg when the O sample is subjected to heat treatment at 580 DEG C ^-1 And good cycle performance can be kept after 130 times of cycle. The cyclic voltammetry test results show that: fePO ₄ The sample has a distinct redox peak, and the redox reaction of the Fe element is performed stepwise. The reduction reaction is Fe ³⁺ Conversion to Fe ²⁺ The reaction equation is FePO4+xLi ⁺ +xe ^- →xLiFePO ₄ +(1-x)FePO ₄ . During the first scan, there was a reduction peak at 2.7V. The reaction equation is LiFePO4-xLi ⁺ -xe ^- →xFePO ₄ +(1-x)LiFePO ₄ The position was 3.4V. As the number of cycles increases, the reduction peak gradually shifts to a higher potential and the oxidation peak gradually shifts to a lower potential, demonstrating an increase in battery cycle reversibility. After 2 times of circulation, the voltage and peak current corresponding to the material are almost unchanged, which shows that the material has good electrochemical circulation performance.

The iron phosphate lithium ion battery anode material prepared by the application has simple process operation and is easy to realize large-scale industrial production. And due to the unique open network structure of the glass matrix, the iron phosphate FePO can be relieved ₄ The volume of the positive electrode material changes in the electrochemical circulation process, so that the transmission rate of lithium ions in the battery and the circulation stability of the electrode are greatly improved.

The above description is only of the preferred embodiments of the present application and is not intended to limit the present application, but various modifications and variations can be made to the present application by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. The preparation method of the iron phosphate microcrystalline glass electrode material is characterized by comprising the following steps:

step 1: a certain amount of FePO ₄ •2H ₂ Drying the raw material O, melting at high temperature to obtain a melt, and then carrying out water quenching and drying to obtain mother glass;

step 2: performing heat treatment on a certain amount of the parent glass in the step 1 according to the glass transition temperature and the glass crystallization peak temperature in the DTA curve of the parent glass to obtain crystallization glass;

the glass transition temperature and the glass crystallization temperature are two peaks in a DTA curve;

step 3: and (3) grinding a certain amount of devitrified glass in the step (2), mixing with acetylene black and PVDF, adding a dispersing agent, fully mixing, scraping the mixture on an aluminum foil, and carrying out vacuum drying to obtain the pole piece.

2. The method for preparing an iron phosphate glass ceramic electrode material according to claim 1, wherein in step 1, fePO is selected from the group consisting of ₄ •2H ₂ And (3) drying the O raw material, then placing the O raw material into an alumina crucible, placing the alumina crucible into a muffle furnace, heating to 1000-1200 ℃ at a heating rate of 8-10 ℃/min, preserving heat for 1-2 hours, taking out the O raw material at a high temperature by using a crucible tongs, directly pouring the O raw material into tap water, and rapidly cooling to obtain the water quenched glass.

3. The method for preparing an iron phosphate glass-ceramic electrode material according to claim 1, wherein in the step 2, the experimental instrument for DTA test is an HCT-4 type comprehensive thermal analyzer manufactured by beijing constant experimental instrument factory, and according to the DTA test result, the water-quenched and dried glass sample is heated to its glass transition temperature at a heating rate of 8-10 ℃/min for 1-2 hours, then is heated to the first crystallization peak temperature or 20 ℃ higher than the first crystallization peak temperature for 1-2 hours, and then is cooled in a furnace to obtain the crystallization glass.

4. The method for preparing an iron phosphate glass ceramic electrode material according to claim 1, wherein in the step 3, the glass ceramic powder, the acetylene black and the PVDF are mixed in a mass ratio of (6-8): (3-1): 1, and are ground and mixed in a mortar for 30-60 minutes.

5. The method for preparing the iron phosphate glass ceramic electrode material according to claim 1, wherein the dispersing agent is polyvinylpyrrolidone or a mixed solution of absolute ethyl alcohol and water, the adding amount is 1-1.5ml, the mixing is carried out in a miniature transparent reagent bottle with a magnet, the stirring and mixing are carried out on a magnetic stirrer for 12-18 hours, and the stirring speed is high enough to stir the slurry, so that the slurry is not easy to be excessively fast or excessively slow.

6. The method for preparing the iron phosphate glass ceramic electrode material according to claim 1, wherein the uniformly mixed slurry is coated on an aluminum foil, samples are uniformly scraped from the head to the tail at one time by a scraper, the samples are uniformly spread on the aluminum foil, and the gap height of the scraper is 100-150um.

7. The method for preparing the iron phosphate glass ceramic electrode material according to claim 1, wherein the vacuum drying system is as follows: the drying temperature is 80-100 ℃ and the drying time is 12-14 hours.

8. An iron phosphate glass ceramic electrode material, characterized in that it is prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the iron phosphate glass-ceramic electrode material according to any one of claims 1 to 7, for a lithium ion battery positive electrode material.