A high-iron-boron-ratio iron borate glass material and its application as a battery anode material

Abstract

The present invention belongs to the cross - field of glass preparation technology and electrochemical material technology, relates to glass electrode materials, and specifically relates to an iron borate glass material with a high iron - to - boron ratio and its application as a battery negative electrode material. Starting from the structure and composition of Fe2O3 - B2O3 glass, by corroding with acid, part of B2O3 in the glass will be corroded away, which will increase the Fe2O3:B2O3 ratio in each sample. Especially for the glass sample after acid treatment, its Fe2O3:B2O3 is much greater than 3 / 7, which is a glass material difficult to prepare by the traditional melting - cooling method; at the same time, the prepared material is still in a glassy state, and when it is applied to the battery negative electrode, the reversible capacity is increased by nearly 50%.

Description

Technical Field

[0001] The present invention belongs to the cross - field of glass preparation technology and electrochemical material technology, relates to glass electrode materials, and specifically relates to an iron borate glass material with a high iron - boron ratio and its application as a battery negative electrode material. Background Art

[0002] In recent years, lithium - ion batteries have been widely used in all aspects of production and life. For example, they are widely used in the aerospace field, the manufacturing field, power sources for transportation, power storage power sources, mobile communication power sources, and a series of other applications. In the current field of energy - storage batteries, being able to manufacture green and environmentally friendly batteries is the current development direction, and lithium - ion batteries have always been the first choice for green and environmentally friendly batteries.

[0003] In the process of development, high - specific - energy is an eternal topic, including the large - capacity of electrode materials. The requirements for an ideal negative electrode material are high specific capacity, good reversibility, a stable and moderate voltage platform, a good interface structure, a stable SEI film, a high Li + diffusion coefficient, high conductivity, being cheap and environmentally friendly. Searching for new negative electrode materials has become a hot topic, and glass materials have obvious advantages as negative electrode materials for lithium - ion batteries. Due to the isotropic nature of its glass structure, charges will move inside the material when moving. The glass structure also has a three - dimensional irregular network structure, which is conducive to the transmission of lithium ions, and this network provides active sites for lithium ions to store during the charge and discharge of the battery. In addition, the introduction of multivalent metal oxides is beneficial to improving the conductivity of the glass material, which has a significant effect on improving the energy and power density of lithium - ion batteries. Therefore, it has great application potential in the field of lithium - ion battery electrodes. Metal borate glasses have a lower atomic weight due to their glass - forming substances. According to Faraday's law, the theoretical capacity of an electrode material is inversely proportional to its molecular weight. Among all known inorganic salt - type electrode materials, because the B element is much lighter than P, Si, and S elements, borates generally have a much smaller molecular weight than phosphates, silicates, and sulfates. Therefore, borates can provide a higher capacity compared to other materials and should have strong potential as negative electrode materials for rechargeable batteries with high energy density.

[0004] When metal borate glass is used as an excellent electrochemical anode material for lithium batteries, it has the characteristics of high reversible capacity, excellent cycling performance and rate performance. It has been found that most iron borate glasses have good electrochemical properties as anode materials, but are affected by the formulation ratio of the two components of Fe2O3 and B2O3. When the content of Fe2O3 is low (<30%), it is easy to form pure glass without generating microcrystals. However, when the content of Fe2O3 is higher than 30, it is extremely easy to crystallize and form glass-ceramics. In addition, as the content of Fe2O3 increases, its performance as an anode material for lithium ion batteries will become higher and higher. When the content of Fe2O3 is low (<30%), its electrochemical performance is relatively low. Therefore, how to prepare iron borate glass with a high iron-boron ratio is a problem that needs to be solved for its use as an anode material for batteries; it is also a problem that needs to be solved to obtain a lithium ion battery with high capacity, high rate performance and high conductivity. Summary of the Invention

[0005] In order to prepare an iron borate glass material with a high iron-boron ratio, the present invention starts from the structure and composition of Fe2O3-B2O3 glass. By etching with acid, B2O3 in the glass will be corroded away, which will increase the ratio of Fe2O3:B2O3 in each sample. Especially for the glass sample after acid treatment, its Fe2O3:B2O3 is much greater than 3 / 7, which is a glass material difficult to prepare by the traditional melting-cooling method.

[0006] The technical solution of the present invention is as follows:

[0007] An iron borate glass material with a high iron-boron ratio is prepared by etching Fe2O3-B2O3 glass with nitric acid.

[0008] Preferably, the Fe2O3-B2O3 glass is prepared by melting and cooling a well-mixed mixture of Fe2O3 powder and boric acid powder.

[0009] Preferably, it is formed by soaking Fe2O3-B2O3 glass in nitric acid for 1-10 minutes.

[0010] Another object of the present invention is to protect the application of the above-mentioned iron borate glass material with a high iron-boron ratio as an anode material for batteries.

[0011] Furthermore, the battery is a lithium ion battery.

[0012] Advantages of the Present Invention

[0013] The corroded glass is used as the anode of a lithium ion battery. Since the content of iron ions in it increases, studying the influence of acid corrosion on the microstructure of iron borate glass, especially on the electrochemical performance, the anode prepared from 10Fe2O3–90B2O3 after 1000 cycles, at 1 Ag −1shows a reversible capacity of about 136.6 mA hg −1 After nitric acid treatment, the 10Fe2O3–90B2O3-HNO3 anode shows a reversible capacity of about 239.5 mA hg after 1000 cycles at 1 A g −1 This indicates that after acid treatment of low-content Fe2O3, the iron-boron ratio increases, and its capacity, rate performance, and conductivity will all increase significantly. Thus, the electrochemical performance of this glass is greatly improved, and a glass with a high iron-boron ratio can be obtained by the melt quenching method at low temperature. −1 Description of the Drawings

[0014] Figure 1 XRD pattern of the 10Fe2O3–90B2O3-HNO3 glass powder prepared in Example 1 of the present invention;

[0015] Figure 2 Electrochemical cycling performance graph of the 10Fe2O3–90B2O3-HNO3 glass powder prepared in Example 1 of the present invention as the anode material of a lithium-ion battery;

[0016] Figure 3 DSC graph of the 10Fe2O3–90B2O3-HNO3 glass prepared in Example 1 of the present invention;

[0017] Figure 4 Impedance spectra of 10Fe2O3–90B2O3 and after nitric acid treatment;

[0018] Figure 5 Impedance spectra of 20Fe2O3–80B2O3 and after nitric acid treatment;

[0019] Figure 6 Impedance spectra of 30Fe2O3–70B2O3 and after nitric acid treatment. Detailed Description of the Invention

[0020] Example 1: Preparation of 10Fe2O3–90B2O3-HNO3 Glass Material

[0021] Weigh 2.0310 g of Fe2O3 powder and 14.1548 g of boric acid powder, grind them in a mortar for 5 min to ensure thorough mixing of the samples. Place the mixed samples in an alumina crucible and melt them in a M1500-30IT muffle furnace with a heating rate of 5 °C / min and a melting temperature of 1280 °C. After maintaining the temperature for 30 min, cool the melted samples in an annealing furnace at 530 °C for 2 h to obtain 10Fe2O3–90B2O3 samples.

[0022] ​The glass sample treated with nitric acid was ground into fragments in a mortar, placed in a beaker, and nitric acid was dropped into it. The sample was soaked in nitric acid for 3 min, washed after acid corrosion, and dried in a dryer to obtain 10Fe2O3–90B2O3-HNO3 glass.

[0023] Figure 1 is the XRD pattern of 10Fe2O3–90B2O3-HNO3 glass powder; from Figure 1 it can be seen that no new crystals were formed in the internal structure of the 10Fe2O3–90B2O3 glass after being treated with nitric acid, and it remained in a glassy state.

[0024] Figure 2 is the electrochemical cycling performance graph of 10Fe2O3–90B2O3-HNO3 glass powder as the anode material of a lithium-ion battery; it can be seen from the graph that after 1000 cycles, the 10Fe2O3–90B2O3 anode of the sample treated with nitric acid showed a reversible capacity twice that of the original glass at 1 Ag −1 condition.

[0025] Figure 3 is the DSC graph of 10Fe2O3–90B2O3-HNO3 glass. It can be seen from the graph that for the original sample without nitric acid treatment, two Tg appeared in its DSC pattern, indicating phase separation occurred and two glassy states were formed. For the sample treated with nitric acid, the first glass transition peak disappeared, indicating that its microstructure was changed after nitric acid corrosion and one of the glass phases was eliminated.

[0026] Example 2: Preparation of 20Fe2O3–80B2O3-HNO3 glass material

[0027] Weighed 3.6444 g of Fe2O3 powder and 11.2888 g of boric acid powder, ground them in a mortar for 5 min to ensure thorough mixing of the sample, placed the mixed sample in an alumina crucible, and melted it in a M1500-30IT muffle furnace. The heating rate of the muffle furnace was 5 °C / min, the melting temperature was 1280 °C, and after holding at a constant temperature for 30 min, the melted sample was cooled in an annealing furnace at 530 °C for 2 h to obtain 20Fe2O3–80B2O3 sample.

[0028] The glass sample treated with nitric acid was ground into fragments in a mortar, placed in a beaker, and nitric acid was dropped into it. The sample was soaked in nitric acid for 1 min, washed after acid corrosion, and dried in a dryer to obtain 20Fe2O3–80B2O3-HNO3.

[0029] Example 3: Preparation of 30Fe2O3–70B2O3-HNO3 glass material

[0030] Weigh 4.9572 g of Fe2O3 powder and 8.9571 g of boric acid powder, grind them in a mortar for 5 min to ensure thorough mixing of the samples. Place the mixed samples in an alumina crucible and melt them in a M1500-30IT muffle furnace. The heating rate of the muffle furnace is 5 °C / min, the melting temperature is 1280 °C, and after maintaining the temperature for 30 min, place the melted samples in an annealing furnace at 530 °C to cool for 2 h to obtain 30Fe2O3–70B2O3 samples.

[0031] Grind the glass samples treated with nitric acid into fragments in a mortar, put them into a beaker, drop nitric acid into it, soak the samples in nitric acid for 10 min, wash them after acid corrosion, and dry them in a dryer to obtain 30Fe2O3–70B2O3-HNO3.

[0032] Example of implementation effect

[0033] Fully mix the three samples of glass powder, acetylene black, and PVDF prepared in Examples 1-3 in a ratio of 7:2:1. Put the materials into a QM-3SP04 planetary ball mill, drop an appropriate amount of N-methylpyrrolidone, and ball mill at a speed of 400 r / min for 4 hours to make the materials mix evenly. After the materials are mixed evenly, apply them evenly on a copper foil and bake in a 110 °C vacuum drying oven for 10 h. Cut the dried copper foil into copper sheets, which are the negative electrode sheets of the battery. Assemble them in a Super1220 / 750 super purification glove box. The assembly order is base, lithium-ion secondary electrolyte, electrode sheet, lithium-ion secondary electrolyte, separator, lithium sheet (positive electrode), nickel mesh, lithium-ion secondary electrolyte, battery case. The formula of the used lithium-ion secondary electrolyte is 1M LiPF6 in DMC:EC:EMC = 1:1:1 Vol%. After assembly, use an MSK-160E button battery sealer to seal the battery. For the sealed battery, use a multimeter to measure the voltage, etc., and conduct a series of electrochemical performance tests such as electrochemical impedance on an electrochemical workstation. The results are as follows:

[0034] Table 1: Comparison of reversible capacities of original samples and acid-treated samples

[0035]

[0036] Table 1 shows the comparison of reversible capacities of original samples and acid-treated samples, indicating that after acid treatment, the capacities of each component have increased. Figures 1 - 3The impedance spectra of the original components and those after acid treatment are shown. According to the impedance results, the smaller the radius of the semicircle in the figure, the smaller the internal resistance, that is, the smaller the impedance of the SEI film and the slower the diffusion rate of lithium ions. From the above spectra, it can be seen that after acid treatment, the impedance becomes smaller compared with that of the original component samples. This indicates that the samples after acid treatment effectively reduce the internal resistance and improve the lithium ion diffusion rate, thereby improving their electrochemical performance.

[0037] The above results show that for the iron-boron glass after nitric acid treatment, due to the corrosion of the B-O phase, the Fe / B ratio in the glass composition increases, which increases the lithium ion conductivity and reversible capacity, changes the iron-boron component, and forms a high-Fe / B ratio iron borate glass. When the iron oxide content is low, the iron-boron ratio, lithium ion conductivity, and reversible capacity can be changed by means of acid corrosion process, increasing the electrochemically active sites and improving its electrochemical performance.

Claims

1. A high-iron-boron-ratio iron borate glass material, characterized in that, It is prepared by etching Fe2O3-B2O3 glass with nitric acid, wherein Fe2O3:B2O3 is greater than 3 / 7; no new crystal is formed in the internal structure of the iron borate glass material formed after nitric acid treatment, and it remains in a glassy state.

2. The iron borate glass material with a high boron ratio according to claim 1, characterized in that, The Fe2O3-B2O3 glass is prepared by melting and cooling a thoroughly mixed homogeneous mixture of Fe2O3 powder and boric acid powder.

3. The iron borate glass material with a high boron ratio according to claim 1, characterized in that, It is made by soaking Fe2O3-B2O3 glass in nitric acid for 1 - 10 minutes.

4. Application of the iron borate glass material with a high iron-boron ratio as claimed in claim 1 as a battery negative electrode material.

5. The application according to claim 4, characterized in that, The battery is a lithium-ion battery.

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