Preparation method and application of FeOCl / PANI composite material

Abstract

A preparation method and application of a FeOCl / PANI composite material, relating to the technical field of chloride ion batteries. The existing aniline intercalation polymerization is relatively slow, and the longer the intercalation time, the higher the degree of polymerization of the polymer, but if the intercalation time is too long, FeOCl is easy to decompose. The present invention first soaks FeOCl nanosheets in aniline monomers for intercalation polymerization, and then adds an oxidant to the soaked reaction solution for treatment. The present invention uses FeOCl nanosheet materials with excellent performance as raw materials to shorten the intercalation time. The present invention uses ferric chloride hexahydrate as an oxidant to accelerate the polymerization of aniline while preparing a product with good dispersibility and no agglomeration. The surroundings, interlayers and surfaces of the FeOCl nanosheets are covered with oxidatively polymerized PANI. Due to the good toughness of polyaniline, the volume expansion and contraction of the FeOCl phase change process have little effect on electrode damage, which is beneficial to improving the discharge capacity and cycle stability of chloride ion batteries.

Description

Technical Field

[0001] The invention relates to the technical field of chloride ion batteries, and in particular to a preparation method and application of a FeOCl / PANI composite material. Background Art

[0002] FeOCl is a positive electrode material for chloride ion batteries. Layered FeOCl materials are abundant in resources (the content of iron in the earth's crust is 4.75%, ranking second among metal elements). It can stably exist in a chloride ion battery system with ionic liquid as electrolyte. It has a high theoretical capacity (250mAh / g) and a high operating voltage. During the discharge process, the separation of chloride ions from FeOCl is divided into two steps. First, the chloride ions are separated and the FeOCl structure remains unchanged. When the chloride ions are separated by 50%, FeOCl undergoes a phase transformation to generate FeO. The FeOCl electrode material will undergo a 141.7% volume expansion and a 58.6% volume contraction during the charge and discharge process, which seriously affects the electrochemical performance of the battery.

[0003] By performing PANI intercalation polymerization on FeOCl, a nano-scale stable FeOCl / PANI composite material is obtained, which can be used as a technical means to improve the electrochemical performance of chloride ion batteries. At present, the preparation method of FeOCl / PANI composite materials mainly performs intercalation polymerization by soaking in aniline monomer. The main disadvantages of this intercalation polymerization method are:

[0004] The intercalation time of aniline monomer into the interlayer of layered FeOCl is closely related to the FeOCl particles. The larger the FeOCl particles are, the longer it takes to fully intercalate. Too long an intercalation time will also cause FeOCl to decompose. In addition to existing in the form of polyaniline, there are also some free aniline ions when aniline is intercalated into the interlayer of FeOCl. For FeOCl layered materials, the effect of alleviating the volume expansion and contraction of the material during the charging and discharging process is poor. Summary of the invention

[0005] The purpose of the present invention is to overcome the above-mentioned defects of the existing intercalation polymerization method and to provide a method for preparing a FeOCl / PANI composite material which is beneficial to improving the discharge capacity and cycle stability of chloride ion batteries.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for preparing a FeOCl / PANI composite material comprises the following steps: firstly, soaking FeOCl nanosheets in aniline monomers for intercalation polymerization, and then adding an oxidant to the soaked reaction solution for treatment.

[0008] As a preferred technical solution of the preparation method of the present invention: when immersing for intercalation polymerization, 0.15g of FeOCl nanosheets are immersed in 4-6mL of aniline monomer, the treatment time is 12-24h, and the treatment temperature is 25-50°C.

[0009] The oxidant is preferably ferric chloride hexahydrate, and more preferably ferric chloride hexahydrate-ethanol solution prepared by dissolving FeCl3·6H2O in ethanol, with a concentration of 0.01-0.1M.

[0010] As a preferred technical solution of the preparation method of the present invention: when adding the oxidant treatment, 4-6 mL of 0.01-0.1 M ferric chloride hexahydrate-ethanol solution is added to every 0.15 g of FeOCl nanosheets, and after adding the ferric chloride hexahydrate-ethanol solution, the mixture is stirred for 10 min-1 h, and the temperature during the stirring treatment is 25-50°C.

[0011] As a preferred technical solution of the preparation method of the present invention: the preparation method further comprises the steps of washing and drying the ethanol after the oxidant treatment, wherein the drying temperature is preferably 55-65°C.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0013] 1. The present invention uses FeOCl nanosheet material with excellent performance (prepared by the method disclosed in Chinese patent application CN 114314673A) as raw material to shorten the intercalation time.

[0014] 2. The present invention uses ferric chloride hexahydrate as an oxidant to accelerate the polymerization of aniline while preparing a product with good dispersibility and no agglomeration. The surroundings, interlayers and surfaces of the FeOCl nanosheets are all covered with oxidatively polymerized PANI. Due to the good toughness of polyaniline, the volume expansion and contraction of the FeOCl phase change process have little effect on electrode damage, which is beneficial to improving the discharge capacity and cycle stability of chloride ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 a and b are the XRD spectra of the products prepared in Example 1 and Example 2, respectively.

[0016] Figure 2 a and b are SEM photos of the products prepared in Example 1 and Example 2, respectively.

[0017] Figure 3 a and b are TEM photos of the products prepared in Example 1 and Example 2, respectively.

[0018] Figure 4 a and b are EDS spectra of the products prepared in Example 1 and Example 2, respectively.

[0019] Figure 5 a and b are the FTIR spectra of the products prepared in Example 1 and Example 2, respectively.

[0020] Figure 6 a, b are the XPS spectra of the N1s narrow peak separation and Cl2p narrow peak separation of the product prepared in Example 1, respectively. Figure 6 c and d are the XPS spectra of the product prepared in Example 2 after N1s narrow peak separation treatment and Cl2p narrow peak separation treatment, respectively.

[0021] Figure 7 a and b are the electrochemical curve and cycle stability curve of the product prepared in Example 1, respectively. Figure 7 c and d are the electrochemical curve and cycle stability curve of the product prepared in Example 2, respectively. DETAILED DESCRIPTION

[0022] Example 1

[0023] This embodiment is used as a comparative example, and only aniline monomer is used for intercalation polymerization. The specific steps are as follows:

[0024] 0.15 g of FeOCl nanosheet material (prepared by the method disclosed in Chinese patent application CN 114314673A) was weighed and placed in a sample bottle, 5 mL of aniline monomer was added, stirred at 50° C. for 24 h, and finally washed with ethanol and dried at 60° C.

[0025] Example 2

[0026] The intercalation polymerization is carried out by soaking aniline monomer, and then an oxidant is added for treatment. The specific steps are as follows:

[0027] Weigh 0.15 g of FeOCl nanosheet material (prepared by the method disclosed in Chinese patent application CN 114314673A), put it into a sample bottle, add 5 mL of aniline monomer, stir at 50°C for 24 h, then add 5 mL of 0.1 M ferric chloride hexahydrate-ethanol solution (prepared by dissolving FeCl3·6H2O in ethanol), stir at 50°C for 1 h, finally wash with ethanol and dry at 60°C.

[0028] Characterization and performance testing of the products prepared in Example 1 and Example 2:

[0029] 1. XRD analysis

[0030] Figure 1 a and b are the XRD spectra of the products prepared in Example 1 and Example 2, respectively. Figure 1 It can be seen from a that after 24 hours of reaction between FeOCl and aniline, a new diffraction peak appeared at 6.4°, and the main peak of FeOCl at 11.2° basically disappeared, indicating that FeOCl was almost intercalated by PANI. Figure 1b It can be seen that after FeOCl reacted with aniline for 24 h and then treated with an oxidant, a new diffraction peak appeared at 6.4°. At the same time, the main peak of FeOCl at 11.2° completely disappeared, indicating that FeOCl was completely intercalated by PANI.

[0031] 2. SEM analysis

[0032] Figure 2 a and b are SEM photos of the products prepared in Example 1 and Example 2, respectively. Figure 2 It can be seen from a that the size of the FeOCl nanosheets has hardly changed (compared with the FeOCl nanosheets disclosed in Chinese patent application CN 114314673A), and the surface remains smooth. Figure 2 b It can be seen that the size of the FeOCl nanosheets has hardly changed (compared with the FeOCl nanosheets disclosed in Chinese patent application CN 114314673A), but the smooth surface state of the FeOCl nanosheets has changed a little, and some roughness appears on the surface and sides.

[0033] 3. TEM analysis

[0034] Figure 3 a and b are TEM photos of the products prepared in Example 1 and Example 2, respectively. The FeOCl nanosheets disclosed in Chinese patent application CN114314673A are in the shape of square sheets, with a thickness of about 20 nm and a length and width of less than 2 μm. Figure 3 a It can be seen that FeOCl nanosheets are only covered by polyaniline in a small area such as the interlayer. Figure 3 a It can be seen that the surroundings, interlayers and surfaces of FeOCl nanosheets are covered by oxidatively polymerized PANI.

[0035] 4. EDS analysis

[0036] Figure 4 a, b are EDS spectra of the products prepared in Example 1 and Example 2, respectively. Figure 4 It can be seen that nitrogen element exists in both prepared products, which indicates that both methods achieve the intercalation of polyaniline.

[0037] 5. FTIR analysis

[0038] Figure 5 a, b are the FTIR spectra of the products prepared in Example 1 and Example 2, respectively. Figure 5 It can be seen that 480cm -1 The strong absorption caused by the vibration of the Fe-O bond in FeOCl still exists. The sample after reaction with aniline has a strong absorption at 600-1600 cm -1The vibration of polyaniline appears in the range, indicating that aniline is intercalated and polymerized between FeOCl layers in the products prepared by the two methods.

[0039] 6. XPS analysis

[0040] Figure 6 a, b are the XPS spectra of the N1s narrow peak separation and Cl2p narrow peak separation of the product prepared in Example 1, respectively. Figure 6 c and d are the XPS spectra of the product prepared in Example 2 after N1s narrow peak separation treatment and Cl2p narrow peak separation treatment, respectively.

[0041] pass Figure 6 As can be seen from a and b, the narrow peak of N1s is split into three peaks at 399.5, 400.0 and 400.7 eV. The three peaks represent the three states of N, from low to high, they are C=N, NH and N + The state of -H indicates that the intercalated aniline is partially oxidized. The narrow peak of Cl2p was split to obtain two peaks at 198.3 and 198.8 eV, representing the chlorine of FeOCl and the chloride ion combined with polyaniline, respectively.

[0042] pass Figure 6 As can be seen from c and d, the narrow peak of N1s is split into three peaks at 399.5, 400.0 and 400.7 eV. The three peaks represent the three states of N, from low to high, they are C=N, NH and N + -H state, indicating that the intercalated aniline is partially oxidized. When an oxidant is added, the oxidized N increases. The narrow peak of Cl2p is split to obtain two peaks at 198.3eV and 198.8eV, representing the chlorine of FeOCl and the chloride ions combined with polyaniline, respectively. After adding an oxidant, the chloride ions combined with polyaniline decrease, and the chloride ions in the FeOCl state increase.

[0043] 7. Electrochemical performance test

[0044] Weigh the prepared active material, binder PVDF (polyvinylidene fluoride) and conductive agent carbon black, dissolve PVDF in NMP (N-methyl-2-pyrrolidone) according to the mass ratio of 6:1:3, stir well, then put the active material and conductive agent carbon black prepared in Examples 1 and 2 into an agate mortar for grinding and mixing, finally disperse the mixed materials in NMP with PVDF dissolved and stir well. Apply it on the synthetic graphite paper, put it in a vacuum drying oven at 80°C for drying overnight, and then form an electrode sheet.

[0045] The electrolyte of chloride ion battery is 0.5M PP14 Cl(1-butyl-1-methylpiperidinium chloride) dissolved in PP 14 The composite ionic liquid of TFSI (1-butyl-1-methylpiperidinium bis(trifluoromethanesulfonyl)imide salt). The prepared ionic electrolyte, positive electrode sheet and metal Li sheet were assembled into a button cell in a glove box, and the battery separator used Celgard3501 polypropylene porous membrane. The battery tester model CT-4008-5V10mA of Shenzhen Xinwei Electronics Co., Ltd. was used. A two-electrode system was used, with metal lithium as the auxiliary electrode and reference electrode, and the scanning potential range was 1.6V-3.5V (vs.Li / Li + ), current density 10mA / g. Scan from open circuit potential to negative electrode, scanning potential range 1.6V-3.5V (vs.Li / Li + ), test temperature 25℃.

[0046] Figure 7 a and b are the electrochemical curve and cycle stability curve of the product prepared in Example 1, respectively. Figure 7 c and d are the electrochemical curve and cycle stability curve of the product prepared in Example 2, respectively.

[0047] pass Figure 7 As can be seen from a and b, the sample obtained after the reaction of FeOCl and aniline for 24 hours has a discharge capacity of 135 mAh / g (54% of the theoretical capacity) in the first cycle as an electrode material battery, and the discharge capacity can still be maintained at 125 mAh / g after 50 cycles, with a capacity retention rate of 93%. The low discharge capacity in the first few times may be due to the serious loss of chloride ions during the intercalation polymerization process, and some chloride ions exist in the form of binding with polyaniline.

[0048] pass Figure 7 As can be seen from c and d, the sample treated with oxidant after the reaction of FeOCl with aniline for 24 hours has a discharge capacity of 186 mAh / g (74% of the theoretical capacity) in the first cycle of the electrode material battery. After 50 cycles, the discharge capacity can still be maintained at 159 mAh / g, and the capacity retention rate is 85%.

[0049] By comparison, it can be found that when the FeOCl / PANI composite material prepared by the present invention is applied to the positive electrode material of a chloride ion battery, the volume expansion and contraction during the phase change of FeOCl has little effect on electrode damage, which is beneficial to improving the discharge capacity and cycle stability of the chloride ion battery.

[0050] The above contents are merely examples and explanations of the concept of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a FeOCl / PANI composite material, comprising: firstly soaking FeOCl nanosheets in aniline monomer for intercalation polymerization, characterized in that: The preparation method also includes the step of adding an oxidant to the reaction solution after soaking, wherein 4-6 mL of 0.01-0.1M ferric chloride hexahydrate-ethanol solution is added to every 0.15 g of FeOCl nanosheets during the oxidant treatment.

2. The preparation method according to claim 1, characterized in that Add ferric chloride hexahydrate-ethanol solution to the reaction solution after soaking and stir for 10 minutes to 1 hour.

3. The preparation method according to claim 1, characterized in that: The temperature during stirring treatment is 25-50°C.

4. The preparation method according to claim 1, characterized in that: When immersing for intercalation polymerization, 0.15 g of FeOCl nanosheets are immersed in 4-6 mL of aniline monomer, the treatment time is 12-24 h, and the treatment temperature is 25-50°C.

5. The preparation method according to claim 1, characterized in that: The preparation method also comprises the steps of washing and drying the ethanol after the oxidant treatment.

6. The preparation method according to claim 5, characterized in that: The drying temperature is 55-65℃.

7. Use of the FeOCl / PANI composite material prepared by the method according to any one of claims 1 to 6 as a positive electrode material for chloride ion batteries.

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