Organic polysilazane / phenol resin composite micro / nanoceramic material, and preparation method and application thereof

Abstract

The application discloses organic polysilazane / phenolic resin composite micro / nano ceramic material and a preparation method and application thereof, belongs to the technical field of ceramic material preparation, and the material is spherical in appearance, wherein four elements of C, N, O and Si are uniformly distributed on the sphere; the preparation method comprises the following steps: first, preparing organic polysilazane / RF polymer; then, carbonizing the organic polysilazane / RF polymer at high temperature and grinding to prepare the organic polysilazane / phenolic resin composite micro / nano ceramic material. The SiCNO / C composite material prepared by the organic polysilazane / phenolic resin composite micro / nano ceramic material and the preparation method and application thereof has high specific capacity and excellent cycle stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ceramic material preparation, and particularly relates to an organic polysilazane / phenolic resin composite micro / nano ceramic material and a preparation method and application thereof. BACKGROUND

[0002] In previous studies, it has been confirmed that amorphous carbon, Si3N4 and a large amount of silicon oxide exist in SiCNO ceramics generated by organic polysilazane at 1000 DEG C. Silicon oxide (SiO x ) is studied as a substitute for Si due to its relatively low volume expansion. Compared with Si, SiO x has the advantages of low cost, easy synthesis and small volume expansion, and can produce inert Li2O and lithium silicate (Li4SiO4, Li2Si2O5) which have a buffering effect on volume expansion during lithiation. However, SiO x , like elemental Si, also faces the problems of high volume expansion and low electronic conductivity. At present, it is considered as one of the most effective ways to improve these problems to manufacture a composite material composed of SiO x uniformly distributed in carbon material. The carbon material can effectively enhance the conductivity and reduce the volume change of SiO x , so that the composite material has excellent structural stability and cycle performance.

[0003] In order to solve the problem of low electronic conductivity of SiO x , various conductive materials are blended with SiO x , and SiO x / carbon composite materials with different morphologies are designed. Among them, carbon material is the most studied conductive material due to its high conductivity and chemical stability. On the other hand, nitrogen-doped carbon material can change the charge distribution and surface polarity of the material surface, thereby greatly improving the charge transfer dynamics performance of the carbon electrode material. In addition, nitrogen-doped carbon material can provide pseudo-capacitance and additional Li + storage sites. SUMMARY

[0004] The present application aims to provide an organic polysilazane / phenolic resin composite micro / nano ceramic material and a preparation method and application thereof. The prepared SiCNO / C composite material exhibits high specific capacity and excellent cycle stability.

[0005] To achieve the above-mentioned purpose, the present application provides an organic polysilazane / phenolic resin composite micro / nano ceramic material. The material is in a spherical morphology, and C, N, O and Si are uniformly distributed on the sphere.

[0006] The application provides a preparation method of the organic polysilazane / phenolic resin composite micro / nano ceramic material, and comprises the following steps:

[0007] Step one, preparing the organic polysilazane / RF polymer;

[0008] Step two, preparing SiCNO / C, i.e. the organic polysilazane / phenolic resin composite micro / nano ceramic material.

[0009] Preferably, the specific operation of step one is as follows: ammonia, deionized water and anhydrous ethanol are uniformly mixed, then resorcinol is added and fully dissolved, after being uniformly stirred and mixed, formaldehyde is added, and after reaction, silazane oligomer is added and continues to react, after the reaction is completed, the obtained product is centrifuged in a centrifuge and washed with anhydrous ethanol to obtain the organic polysilazane / RF polymer.

[0010] Preferably, the specific operation of step two is as follows: the organic polysilazane / RF polymer obtained in step one is vacuum dried, and the dried polymer is placed in a quartz porcelain boat, and after carbonization under a nitrogen atmosphere, the SiCNO / C sample is obtained, and the obtained SiCNO / C sample is ground into powder and then ball milled to obtain SiCNO / C.

[0011] Preferably, in step one, the volume ratio of ammonia, deionized water and anhydrous ethanol is 0.1-0.3:10-30:5-16, the amount of resorcinol is 0.03-1g, the amount of formaldehyde is 0.05-0.15mL, the amount of silazane oligomer is 0.5-1.0mL, and the reaction time is 10-12h.

[0012] Preferably, in step one, the centrifuge speed is 5000-10000rpm / min, the centrifugation time is 5-20min, and the anhydrous ethanol is washed for 3-5 times.

[0013] Preferably, in step two, the drying temperature is 50-100℃, the drying time is 18-20h, the carbonization temperature is 800-1000℃, the heating rate is 5-10℃ / min, the carbonization time is 3-5h, the grinding speed is 300rpm / min, and the ball milling time is 5-10h.

[0014] The application provides an application of the organic polysilazane / phenolic resin composite micro / nano ceramic material, and the organic polysilazane / phenolic resin composite micro / nano ceramic material is applied to a lithium ion battery negative electrode material.

[0015] Therefore, the application adopts the organic polysilazane / phenolic resin composite micro / nano ceramic material, the preparation method and the application thereof, and the prepared SiCNO / C composite material exhibits high specific capacity and excellent cycle stability.

[0016] The technical solutions of the present application are described in further detail below with reference to the accompanying drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a preparation flow chart of the organic polysilazane / phenolic resin composite micro / nano ceramic material and its preparation method and application examples of the present application;

[0018] Figure 2 is the infrared spectrum of Organpolysilazane / RF and SiCNO / C of the organic polysilazane / phenolic resin composite micro / nano ceramic material and its preparation method and application examples of the present application;

[0019] Figure 3 is the XRD diffraction spectrum of SiCNO / C composite microspheres and the Raman scattering images of SiCNO / C-1, SiCNO / C-2 and SiCNO / C-3 of the organic polysilazane / phenolic resin composite micro / nano ceramic material and its preparation method and application examples of the present application;

[0020] Figure 4 is the scanning electron microscope images of organic polysilazane / RF polymer, SiCNO / C-1, SiCNO / C-2, SiCNO / C-3 and the transmission electron microscope image and element distribution map of SiCNO / C-1 of the organic polysilazane / phenolic resin composite micro / nano ceramic material and its preparation method and application examples of the present application;

[0021] Figure 5 is the XPS full spectrum, Si2p high-resolution XPS spectrum, C1s high-resolution XPS spectrum and N1s high-resolution XPS spectrum of SiCNO / C-1 of the organic polysilazane / phenolic resin composite micro / nano ceramic material and its preparation method and application examples of the present application;

[0022] Figure 6 is the Si2p high-resolution XPS spectrum of SiCNO / C-2 and SiCNO / C-3 of the organic polysilazane / phenolic resin composite micro / nano ceramic material and its preparation method and application examples of the present application;

[0023] Figure 7 is the cyclic voltammogram of SiCNO / C-1, SiCNO / C-2, SiCNO / C-3 of the organic polysilazane / phenolic resin composite micro / nano ceramic material and its preparation method and application examples of the present application;

[0024] Figure 8are the first cycle capacity-voltage curves of SiCNO / C-1, SiCNO / C-2 and SiCNO / C-3, and the current density is 100 mA·g -1 are the cycle performance and coulomb efficiency of SiCNO / C-1, SiCNO / C-2 and SiCNO / C-3, the rate performance curves of SiCNO / C-1, SiCNO / C-2 and SiCNO / C-3, and the current density is 100 mA·g -1 for the first three cycles and the subsequent cycle current density is 1 A·g -1 are the long cycle performance curves of SiCNO / C-1, SiCNO / C-2 and SiCNO / C-3;

[0025] Figure 9 are the electrochemical impedance spectrograms of SiCNO / C-1, SiCNO / C-2 and SiCNO / C-3 and the equivalent circuit diagrams of SiCNO / C-1, SiCNO / C-2 and SiCNO / C-3 before and after cycles;

[0026] Figure 10 are the CV curves of SiCNO / C-1 at 0.1-1 mV·s -1 , the linear relationship of Log(i) and Log(v), the contribution of capacitance control to capacity at 0.1-1 mV·s -1 , and the contribution of pseudo-capacitance to total capacity at 0.1 mV·s -1 ;

[0027] Figure 11 are the SEM images of the electrode plane of SiCNO / C-1, SiCNO / C-2 and SiCNO / C-3 before and after 100 charge-discharge cycles;

[0028] Figure 12 are the SEM images of the corresponding cross-section of the electrode of SiCNO / C-1, SiCNO / C-2 and SiCNO / C-3 before and after 100 charge-discharge cycles;

[0029] Figure 13 are the SEM images of the corresponding cross-section of the electrode of SiCNO / C-1, SiCNO / C-2 and SiCNO / C-3 before and after 100 charge-discharge cycles; xThe first charge-discharge voltage curve of / C, SiCNO / C-1, and the current density is 100 mA·g -1 SiO x The cycle performance and coulombic efficiency of / C and SiCNO / C-1;

[0030] Figure 14 SiO x The electrochemical impedance spectrogram of / C and SiCNO / C-1 before cycling, SiO x The electrochemical impedance spectrogram of / C before and after cycling, and SiO x The Z' vs. ω curve of the impedance of / C and SiCNO / C-1 -1 / 2

[0031] Figure 15 SiO x The SEM images of / C electrode before and after 100 charge-discharge cycles. DETAILED DESCRIPTION

[0032] The technical solutions of the present application are further described below through the drawings and examples.

[0033] Unless otherwise defined, the technical terms or scientific terms used in the present application shall have the usual meanings understood by those with ordinary skills in the art to which the present application belongs.

[0034] The present application provides an organic polysilazane / phenolic resin composite micro / nano ceramic material, which is spherical in shape, and C, N, O, and Si are uniformly distributed on the sphere.

[0035] As Figure 1 shown, the preparation method of the above-mentioned organic polysilazane / phenolic resin composite micro / nano ceramic material uses a method to synthesize organic silicon / RF polymer composite microspheres. Under this condition, the ethoxy groups in the silazane oligomer (OPSZ 1001) undergo hydrolysis and condensation reactions. At the same time, the resorcinol and formaldehyde undergo condensation to form a resorcinol formaldehyde (RF) polymer. Because the reaction rates of the above two reactions are similar, and there is a hydrogen bond interaction between the -Si-OH generated by hydrolysis and the phenolic hydroxyl group of phenol, the silazane oligomer can co-condense with resorcinol and formaldehyde to form homogeneous organic polysilazane / RF polymer microspheres. After a carbonization process at 1000°C in a nitrogen environment, nitrogen-doped composite microspheres (SiCNO / C) with uniform element distribution are generated, which specifically includes the following steps:

[0036] Step one, by ​Preparation of organopolysilazane / RF polymer: ammonia, deionized water and anhydrous ethanol are mixed uniformly, then resorcinol is added to be dissolved fully, after stirring and mixing uniformly, formaldehyde is added, after reaction, silazane oligomer is added, and the reaction is continued, after the reaction is completed, the obtained product is centrifuged in a centrifuge, and is washed with anhydrous ethanol to obtain organopolysilazane / RF polymer (OPSZ / RF for short).

[0037] The volume ratio of ammonia, deionized water and anhydrous ethanol is 0.1-0.3:10-30:5-16, the amount of resorcinol is 0.03-1 g, the amount of formaldehyde is 0.05-0.15 mL, and the amount of silazane oligomer is 0.5-1.0 mL, and the reaction is carried out for 10-12 h.

[0038] The centrifuge speed is 5000-10000 rpm / min, the centrifugation time is 5-20 min, and the anhydrous ethanol is washed for 3-5 times.

[0039] Step two, preparation of SiCNO / C, i.e. organopolysilazane / phenolic resin composite micro / nano ceramic material: the organopolysilazane / RF polymer obtained in step one is vacuum dried, and the dried polymer is placed in a quartz boat, and after carbonization under nitrogen atmosphere, a SiCNO / C sample is obtained, and the obtained SiCNO / C sample is ground into powder and then ball milled to obtain SiCNO / C.

[0040] The drying temperature is 50-100℃, the drying time is 18-20 h, the carbonization temperature is 800-1000℃, the heating rate is 5-10℃ / min, the carbonization time is 3-5 h, the grinding speed is 300 rpm / min, and the ball milling time is 5-10 h.

[0041] Figure 2 The infrared spectrum of the product obtained in step one and step three is shown in the figure, through infrared spectrum analysis of the sample, it is found that the absorption peak of -O-H appears at 3590 cm -1 before carbonization of the organopolysilazane / RF composite microspheres, the absorption peak of carbon-carbon double bond on the benzene ring appears at 1614 cm -1 and 1450 cm -1 , and the characteristic peak appearing at 1269 cm -1 is attributed to the stretching vibration of -CH3 in organopolysilazane and C-O bond in resorcinol. The absorption peaks appearing at 916 cm -1 and 2372 cm -1The absorption peak at [value missing] is attributed to the Si-N and Si-H bonds in the organopolysilazane. After the condensed sample was decomposed at 1000℃ in a N2 atmosphere, it did not completely decompose due to the high thermal stability of the C-Si and Si-O bonds. The -Si-CH3 (1267 cm⁻¹) in the organopolysilazane... -1 ) and -CH2-(2972cm -1 The characteristic peaks disappeared, while Si-O (1051 cm⁻¹) -1 ) and -Si-C- bonds (817cm) -1 The characteristic peaks of ) appear after pyrolysis.

[0042] This invention provides the application of organopolysilazane / phenolic resin composite micro / nano ceramic materials, which are applied to lithium-ion battery anode materials.

[0043] Example 1

[0044] This invention provides a method for preparing organopolysilazane / phenolic resin composite micro / nano ceramic materials, comprising the following steps:

[0045] Step 1, adopt Preparation of organopolysilazane / RF polymer: First, ammonia water (0.1 mL, 25 wt%) was mixed thoroughly with deionized water (20 mL) and anhydrous ethanol (8 mL). Then, resorcinol (0.03 g) was added and dissolved completely, and mixed thoroughly. After stirring for 1 h, formaldehyde (0.05 mL) was added. After reacting at room temperature for 24 h, silazane oligomer (0.6 mL) was added, and the reaction was continued for 12 h. After the reaction was completed, the product was centrifuged at 8000 rpm / min for 10 min and washed three times with anhydrous ethanol to obtain Organpolysilazane / RF-1 (OPSZ / RF-1).

[0046] Step 2: Preparation of SiCNO / C, namely organopolysilazane / phenolic resin composite micro / nano ceramic material: The obtained Organpolysilazane / RF-1 polymer was vacuum dried at 80℃ for 24h. Then, the dried polymer was placed in a quartz ceramic boat and carbonized at 1000℃ (5℃ / min, held for 3h) under N2 atmosphere to obtain SiCNO / C sample. The obtained sample was ground into powder in an agate mortar and then ball-milled (300rpm / min) for 6h to obtain SiCNO / C, denoted as SiCNO / C-1.

[0047] Example 2

[0048] The only difference between this example and Example 1 is the preparation method of Step 1: ammonia (0.15 mL, 25 wt%) was mixed with deionized water (20 mL) and anhydrous ethanol (8 mL) uniformly, then resorcinol (0.05 g) was added to dissolve completely, and mixed uniformly. After stirring for 1 h, formaldehyde (0.07 mL) was added, and after 24 h of reaction at room temperature, silazane oligomer (0.6 mL) was added, and the reaction was continued for 12 h. After the reaction was completed, the obtained product was centrifuged at 8000 rpm / min for 10 min in a centrifuge, and washed with anhydrous ethanol repeatedly for 3 times to obtain Organpolysilazane / RF-2, and the final product was recorded as SiCNO / C-2.

[0049] Example 3

[0050] The only difference between this example and Example 1 is the preparation method of Step 1: ammonia (0.3 mL, 25 wt%) was mixed with deionized water (20 mL) and anhydrous ethanol (16 mL) uniformly, then resorcinol (1 g) was added to dissolve completely, and mixed uniformly. After stirring for 1 h, formaldehyde (0.14 mL) was added, and after 24 h of reaction at room temperature, silazane oligomer (0.6 mL) was added, and the reaction was continued for 12 h. After the reaction was completed, the obtained product was centrifuged at 8000 rpm / min for 10 min in a centrifuge, and washed with anhydrous ethanol repeatedly for 3 times to obtain Organpolysilazane / RF-3, and the final product was recorded as SiCNO / C-3.

[0051] Comparative Example 1

[0052] Preparation of SiO x The specific operation steps for preparing SiO

[0053] Step 1, preparation of SiO2 / RF microspheres: ammonia (0.3 mL, 25 wt%) was mixed with deionized water (20 mL) and anhydrous ethanol (16 mL) uniformly, then resorcinol (1 g) was added to dissolve completely, and mixed uniformly. After stirring for 1 h, formaldehyde (0.14 mL) was added. After 24 h of reaction at room temperature, TEOS (0.6 mL) was added, and the reaction was continued for 12 h. The same steps as in Example 1 were used for centrifugation, and the microspheres were washed for 3 times to obtain SiO2 / RF microspheres.

[0054] Step 2, vacuum drying of the SiO2 / RF microspheres obtained in Step 1 was performed, and the dried polymer was placed in a quartz boat, and after carbonization under nitrogen atmosphere, SiO x / C composite microspheres sample, the obtained SiO x / C composite microspheres sample was ground in an agate mortar, and after grinding into powder, ball milling was performed to obtain SiO x / C composite microspheres.

[0055] In order to determine the structure of the three groups of SiCNO / C products, the SiCNO / C three groups of samples were analyzed using an X-ray diffractometer. As shown in Figure 3 , Figure 3 (a) of FIG. 13 is an XRD diffraction spectrum of SiCNO / C-1, SiCNO / C-2 and SiCNO / C-3, and from the figure, it can be seen that relatively wide diffraction peaks appear at about 23° and 43°, indicating that the sample after carbonization is amorphous, and the X-ray diffraction analysis fully proves that the main components of the three groups of materials are SiO x and amorphous carbon. Figure 3 (b) of FIG. 13 is a Raman scattering image of SiCNO / C-1, SiCNO / C-2 and SiCNO / C-3, and the Raman spectrum is used to analyze the existing form of carbon in SiCNO / C-1, SiCNO / C-2 and SiCNO / C-3. As shown in Figure 3 (b) of FIG. 13, the peaks at 1330 cm -1 and 1608 cm -1 in the Raman spectrum are respectively attributed to the D band and the G band of carbon material, proving that there is amorphous carbon in the product after carbonization of the organic polysilazane / RF polymer.

[0056] Figure 4 (a)-(f) of FIG. 13 are scanning electron microscope images of the three groups of organic polysilazane / RF polymers and SiCNO / C-1, SiCNO / C-2, SiCNO / C-3, and from the figure, it can be observed that with the decrease of the content of the silazane oligomer, the particle size of the organic polysilazane / RF polymer microspheres gradually increases, and the reason is that the condensation rate is not synchronized due to the change of the content in the co-condensation process of the organic polysilazane and the phenolic resin, and from the figure, it can also be seen that the three groups of samples SiCNO / C-1, SiCNO / C-2, SiCNO / C-3 all have a typical spherical morphology. Figure 4 (g) of FIG. 13 shows the EDS mapping of SiCNO / C-1, which can show that the four elements C, N, O, Si in the SiCNO / C-1 sample are uniformly distributed in the spherical SiCNO / C-1, and this result is achieved because the hydrolysis and condensation rate of the silazane oligomer and the phenolic resin is matched in the condensation process of the organic silazane oligomer OPSZ1001 and formaldehyde and resorcinol.

[0057] Figure 5 (a) of FIG. 13 shows the same result as the EDS result, and the XPS spectrum shows that the SiCNO / C-1 sample is composed of four elements C, N, O, Si, as shown in Table 1. The high-resolution spectrum of silicon of the OPSZ / RF polymer after carbonization at 1000°C is shown in Figure 5(b) shows that the high-resolution Si2p peak is fitted into three peaks of 102.5 eV, 103.3 eV and 103.9 eV, which correspond to Si 2+ , Si 3+ and Si 4+ , respectively. Through calculation, the ratio of Si 2+ , Si 3+ and Si 4+ is 6.5:47.3:46.1, and the average valence state is determined to be 3.39. Figure 5 (c) shows that the C1s is divided into four peaks of 284.8 eV, 285.8 eV, 286.5 eV and 288.9 eV, proving the existence of C-C / C=C, C-N, C-O and C=O bonds in the SiCNO / C-1 composite material. Figure 5 (d) shows that the N1s spectrum is divided into three peaks, corresponding to pyridine nitrogen (398.5 eV), pyrrole nitrogen (400.8 eV) and graphite nitrogen (400.4 eV), respectively, proving that nitrogen doping is successfully achieved in SiCNO / C. Since nitrogen doping produces more "defects", these "defects" can provide more reaction active sites for lithium ion intercalation, which is beneficial to improve the ion / electron transport capacity of SiCNO / C-1 material, thereby improving its electrochemical performance. The Si2p high-resolution spectrum of samples SiCNO / C-2 and SiCNO / C-3 is shown in Figure 6 , and the average valence state of Si is 3.29 and 3.27, respectively.

[0058] Table 1 Element content in SiCNO / C-1, SiCNO / C-2 and SiCNO / C-3

[0059] Sample C (wt%) N (wt%) O (wt%) Si (wt%) SiCNO / C-1 43.3 6.2 28.4 22.1 SiCNO / C-2 46.3 3.9 30.9 18.9 SiCNO / C-3 52.6 2.0 29.6 15.8

[0060] The prepared SiCNO / C-1, SiCNO / C-2 and SiCNO / C-3 are applied to lithium ion battery negative electrode materials, and the lithium storage performance of SiCNO / C-1, SiCNO / C-2 and SiCNO / C-3 as negative electrode materials is studied by cyclic voltammetry.

[0061] Figure 7 The cyclic voltammograms of SiCNO / C electrode materials at 0.1 mV·s -1 are shown in Figure 7 (a) is the cyclic voltammogram of SiCNO / C-1, Figure 7 (b) is the cyclic voltammogram of SiCNO / C-2, Figure 7 (c) is the cyclic voltammogram of SiCNO / C-3. Figure 7(a) shows that SiCNO / C-1 has a reduction peak at 0.54 V in the first cycle CV curve, and it does not appear in the subsequent cycles, indicating that the electrolyte decomposition and the formation of solid electrolyte interface (SEI) film occur in this cycle. In addition, a reduction peak appears at 1.28 V, which is related to the irreversible reaction between Li and SiO x , and the sharp reduction peak at 0.01 V is due to the formation of silicon lithium alloy, and the wide anodic peak in the range of 0.5-1 V is related to the dealloying of Li x Si alloy and the formation of amorphous silicon.

[0062] In the subsequent cycles, a new reduction peak appears at 0.27 V due to the alloying of amorphous silicon; in addition, the CV curves almost overlap in the following several cycles, which indicates that the SiCNO / C electrode has low polarization degree and high reversibility in the reaction. Figure 7 (b) and Figure 7 (c) in the figure, it can be seen that SiCNO / C-2 and SiCNO / C-3 have similar cyclic voltammetry curves, indicating that the SiCNO / C-1, SiCNO / C-2 and SiCNO / C-3 composite materials have the same electrochemical behavior.

[0063] Figure 8 (a) is the first cycle capacity-voltage curve of the SiCNO / C sample with a current density of 100 mAh·g -1 , and from the figure, it can be seen that the specific discharge capacity of SiCNO / C-1 is 2094.2 mAh·g -1 and 1309.0 mAh·g -1 , and the first cycle CE is 62.5%. In comparison, the specific discharge capacity of SiCNO / C-2 and SiCNO / C-3 is 1133.4 mAh·g -1 and 996.5 mAh·g -1 , and the first cycle CE of SiCNO / C-2 and SiCNO / C-3 is 65.1% and 61.2%. The reason for the low coulombic efficiency is that SEI film is generated during the first cycle charge and discharge process, and irreversible electrochemical reaction generates silicate and lithium oxide, which is also reflected in the CV test results. With the increase of carbon content in the sample, the first cycle CE decreases, which is due to the increase of carbon content in the sample, which enhances the conductivity and structural stability of the sample. From Figure 8 (b), it can be seen that SiCNO / C-1 can still maintain 797.6 mAh·g -1discharge specific capacity and maintained a high coulombic efficiency (99.6%), in contrast, the cycling performance of SiCNO / C-2 and SiCNO / C-3 electrodes slightly decreased compared to SiCNO / C-1. After 100 charge-discharge cycles at the same current density, the SiCNO / C-2 electrode showed a discharge specific capacity of 541.4 mAh·g -1 , and the SiCNO / C-3 electrode showed a discharge specific capacity of only 420.1 mAh·g -1 . From the above results, it can be seen that the SiCNO / C electrodes exhibited a high reversible capacity and excellent cycling stability and coulombic efficiency. The good cycling performance of the SiCNO / C was attributed to the uniform distribution of SiO x in the nitrogen-doped carbon spheres, which limited the volume change and improved the electrical conductivity.

[0064] Figure 8 (c) of FIG. 1 shows the rate performance of the composites containing SiCNO / C-1, SiCNO / C-2 and SiCNO / C-3 at a current density of 100 mAh·g -1 , and then at 100, 200, 500, 1000, 1500 and 2000 mAh·g -1 , respectively. When the current density was returned to 100 mAh·g -1 after cycles 31 to 35, the reversible capacity of the battery could still be restored to 827.8 mAh·g -1 , indicating that the structure of the sample was stable during the lithiation and delithiation processes and did not suffer from serious structural damage. Like SiCNO / C-1, the reversible capacities of SiCNO / C-2 and SiCNO / C-3 could also be restored after cycling at a high current density, which indicated that the spherical SiCNO / C composite had good structural stability during the rate test.

[0065] Figure 8 (d) of FIG. 1 shows the long cycle performance of SiCNO / C. The SiCNO / C-1, SiCNO / C-2 and SiCNO / C-3 electrodes were subjected to 400 discharge / charge cycles at a current density of 1 A·g -1 to examine the cycling stability of the samples. After activation, the SiCNO / C-1, SiCNO / C-2 and SiCNO / C-3 electrodes showed discharge specific capacities of 893.6 mAh·g -1 , 479.5 mAh·g -1 and 458.2 mAh·g -1The discharge specific capacity was [not specified]. Overall, although the capacity decay of the SiCNO electrode material was relatively significant during the first 40 cycles, the discharge specific capacity of SiCNO / C-1 reached 587.0 mAh·g on the 400th cycle. -1 The discharge specific capacity of SiCNO / C-2 and SiCNO / C-3 is only 358.2 mAh·g. -1 and 257.7mAh·g -1 This indicates that SiCNO / C-2 and SiCNO / C-3 have relatively poor cycle stability.

[0066] Figure 9 Figure (a) shows the electrochemical impedance spectroscopy (EIS) results of three groups of samples: SiCNO / C-1, SiCNO / C-2, and SiCNO / C-3. In the Nyquist plot, the larger semicircle diameter represents the charge transfer resistance (Rct), and the smaller semicircle diameter represents the impedance generated by SEI (R). S The test results were fitted, as shown in Table 2. Although SiCNO / C-3 had a higher carbon content than the other two samples, SiCNO / C-1 had the lowest impedance. This is because SiCNO / C-3 has a high carbon content, uneven element distribution, and large particle size, resulting in poor suppression of volume expansion during charge-discharge cycles and affecting the material's capacity. Furthermore, from... Figure 9 As can be seen from (b)-(d) in the figure, the impedance of the three groups of samples decreased after charge-discharge cycles because the material was activated during the cycle.

[0067] Table 2. EIS impedance fitting results of SiCNO / C-1, SiCNO / C-2, and SiCNO / C-3 before cycling.

[0068] Sample [R s (Ω)]]> [R ct (Ω)]]> SiCNO / C-1 0.5 87.1 SiCNO / C-2 0.8 123.7 SiCNO / C-3 1.8 160.8

[0069] To further investigate the lithium storage mechanism of SiCNO / C microsphere anode materials, lithium was stored at different scan rates (0.1, 0.2, 0.5, and 1.0 mV·s). -1 The CV test was performed on SiCNO / C-1 as follows: Figure 10 As shown in (a) above. Observe. Figure 10 In (a), it was found that 0.1–1.0 mV·s -1 The CV curves of the scans are highly consistent in shape, and the relationship between the peak current (i) and the scan rate (v) follows a functional relationship as shown in equation (1):

[0070] i = av b (1);

[0071] Here, 'a' is an adjustable value, and 'b' can be obtained from the fitted slope of the Log(v)-Log(i) plot. It is an indicator of charge storage kinetics and can reveal the corresponding electrode storage mechanism. For example... Figure 10 As shown in (b) above, the calculated b values ​​for the oxidation / reduction peaks are 0.64 and 0.77, respectively, indicating that the total capacity includes both capacitive and diffusion-controlled processes. Furthermore, from... Figure 10 As shown in (c), the response current (i) at a specific scan rate (v) can be quantitatively described as being controlled by a pseudocapacitive process (k1v) and a diffusion control process (k2v). 1 / 2 The combination of the two different mechanisms is expressed as shown in equation (2):

[0072] i(v)=k1v+k2v 1 / 2 (2);

[0073] Figure 10 The results in (c) show that as the scan rate increases, the pseudocapacitive contribution increases while the diffusion contribution decreases accordingly. This indicates that the pseudocapacitive control process has a significant impact on the total electrode capacity, especially at higher scan rates. The contribution of pseudocapacitive capacitance to the battery capacity is calculated by calculating the values ​​of k1 and k2. Figure 10 As shown in (d) in the figure, with a speed of 0.1 mV·s -1 During scanning, the pseudocapacitive contribution of the SiCNO / C-1 electrode was approximately 33.5%. The proportion of pseudocapacitive control increased with increasing scan rate, indicating that the capacitance control mechanism contributes to the Li... + Achieve fast embedding / extraction at higher scan rates.

[0074] Therefore, the SiCNO / C-1 electrode at 1 A·g -1 It exhibits high rate capability and stable long-term cycling performance. The high pseudocapacitance contribution of SiCNO / C can be explained by the following aspects: (1) The large specific surface area of ​​SiCNO / C microspheres can provide enough reactive sites for lithium-ion storage; (2) Nitrogen doping in carbon materials generates more "defects" in the material, which can provide more reactive sites for Li-ion storage. + Provide additional storage sites.

[0075] To further compare the structural stability of SiCNO / C-1, SiCNO / C-2, and SiCNO / C-3 composite materials, the electrode morphology of the materials before and after 100 lithiation / delithiation cycles was observed using scanning electron microscopy, such as... Figure 11 As shown. Among them Figure 11 Image (a) shows the SEM image of the SiCNO / C-1 electrode plane before 100 charge-discharge cycles. Figure 11 Image (b) shows the SEM image of the SiCNO / C-2 electrode plane before 100 charge-discharge cycles.Figure 11 (c) is the SEM image of the SiCNO / C-3 electrode plane before 100 charge-discharge cycles, Figure 11 (d) is the SEM image of the SiCNO / C-1 electrode plane after 100 charge-discharge cycles, Figure 11 (e) is the SEM image of the SiCNO / C-2 electrode plane after 100 charge-discharge cycles, Figure 11 (f) is the SEM image of the SiCNO / C-3 electrode plane after 100 charge-discharge cycles. As can be seen from the figure, after 100 charge-discharge cycles, due to the formation of SEI film on the surface of the electrode, the surface of the SiCNO / C-1 electrode is relatively smooth and flat, without obvious cracks and pulverization phenomenon, while the SiCNO / C-2 and SiCNO / C-3 electrode surfaces appear different degrees of cracking or pulverization.

[0076] As shown in Figure 12 , the cross sections of SiCNO / C-1, SiCNO / C-2 and SiCNO / C-3 as electrodes were tested by SEM, and the volume expansion rates of the three groups of samples after cycling were compared, wherein Figure 12 (a) is the SEM image of the corresponding cross section of SiCNO / C-1 as an electrode before 100 charge-discharge cycles, Figure 12 (b) is the SEM image of the corresponding cross section of SiCNO / C-2 as an electrode before 100 charge-discharge cycles, Figure 12 (c) is the SEM image of the corresponding cross section of SiCNO / C-3 as an electrode before 100 charge-discharge cycles, Figure 12 (d) is the SEM image of the corresponding cross section of SiCNO / C-1 as an electrode after 100 charge-discharge cycles, Figure 12 (e) is the SEM image of the corresponding cross section of SiCNO / C-2 as an electrode after 100 charge-discharge cycles, Figure 12Figure (f) shows the SEM image of the corresponding cross-section after 100 charge-discharge cycles when SiCNO / C-1 is used as the electrode. As can be seen from the figure, after 100 cycles, the thickness of the SiCNO / C-1 electrode expanded from 19.3 μm to 28.5 μm, with a volume expansion rate of 47.7%. The volume expansion rates of SiCNO / C-2 and SiCNO / C-3 materials were 37.9% and 50%, respectively. The results indicate that the volume expansion rates of the three groups of samples (SiCNO / C-1, SiCNO / C-2, and SiCNO / C-3) are relatively low, which is attributed to the uniform distribution of nitrogen-doped carbon in the microspheres, effectively mitigating volume changes. Furthermore, the spherical structure exhibits high mechanical stability, and the stress generated by volume expansion is uniformly transmitted to the entire sphere surface, thereby reducing local stress concentration. This uniform pressure distribution helps reduce the risk of material deformation and fracture, enabling the spherical structure to better withstand volume changes during cycling. In addition, nitrogen doping generates larger defects, which can accommodate more Li... + This also helps reduce volume expansion.

[0077] To compare the effect of nitrogen doping on the electrochemical performance of materials, SiO2 was subjected to... x The charge-discharge performance of / C and SiCNO / C-1 was compared, such as Figure 13 As shown, where Figure 13 (a) in the text represents SiO2 x The first charge-discharge voltage curves of / C and SiCNO / C-1 Figure 13 (b) represents a current density of 100 mA·g -1 SiO x Cyclic performance and coulombic efficiency of / C and SiCNO / C-1. As shown in the figure, the initial discharge capacity of SiCNO / C-1 is 2094.2 mAh·g. -1 The initial CE was 62.5%, while SiO x The initial discharge capacity of / C is 1244.1 mAh·g. -1 The coulombic efficiency is 58.7%. After 100 charge-discharge cycles, SiCNO / C-1 exhibits a power density of 797.6 mAh·g. -1 The reversible capacity of SiO x / C capacity decays rapidly, retaining 424.1 mAh·g after 100 cycles. -1 The discharge specific capacity is significantly improved. Due to nitrogen doping, SiCNO / C-1 exhibits enhanced ion / electron transport rates, resulting in a substantial increase in charge / discharge capacity.

[0078] Figure 14 (a) and Figure 14 (b) shows untreated SiO₂. xThe EIS test results of / C and SiCNO / C before and after cycling were used to fit the test results and estimate R. ct The values ​​were then used to plot SiO at low frequencies using the aforementioned data. x Z'vs. the resistance of / C and SiCNO / C-1. -1 / 2 Curves, such as Figure 14 As shown in (c) of Table 3. Figure 14 As shown in (c), SiCNO / C has the lowest charge transfer impedance, indicating that nitrogen doping plays a very important role in the conductivity of the composite material. Furthermore, after 100 charge-discharge cycles, SiO... x / C's charge transfer impedance (R ct The maximum value indicates that nitrogen doping can further enhance the charge transfer kinetics of the material.

[0079] Table 3 SiCNO / C-1 and SiO x EIS impedance fitting results before / C cycle

[0080] Samples Rs (Ω) Rct (Ω) SiCNO / C-1 0.5 67.2 SiO x / C]] 0.7 179.6

[0081] To visually demonstrate the effect of nitrogen doping on the conductivity of the material, the lithium-ion diffusion coefficient of the above SiCNO / C-1 was calculated according to equation (3):

[0082]

[0083] Calculation of SiO x / D of C and SiCNO / C-1 composite materials Li+ The values ​​are 1.07 × 10 -15 cm 2 ·s -1 4.23×10 -15 cm 2 ·s -1 D Li+ The increase in the value indicates that the lithium ion insertion and extraction rates in SiCNO / C-1 are faster than in the other two samples, demonstrating that the introduction of nitrogen enhances the conductivity of the carbon composite material.

[0084] To further compare SiO x The structural stability of the / C and SiCNO / C-1 composite materials was assessed using scanning electron microscopy (SEM) to observe the morphology of the materials after 100 lithiation / delithiation cycles. For example... Figure 15 As shown, where Figure 15 (a) in the text represents SiO2 x SEM image of the / C electrode before charge-discharge cycles. Figure 15 (b) in the text represents SiO2. xSEM images of SiCNO / C-1 electrode after 100 charge-discharge cycles. As can be seen from the figure, after 100 charge-discharge cycles, due to the formation of SEI film on the surface of the pole piece, the surface of SiCNO / C-1 electrode is complete, without obvious cracks and pulverization phenomenon, while in SiO x / C electrode, cracks of different degrees or pulverization appear on the surface of SiO x / C electrode. The cracks on the surface of SiO x / C fall off from the current collector, indicating that the single carbon material composite is not ideal for inhibiting structural changes. The surface of the nitrogen-doped carbon composite electrode material has almost no cracks, proving that the nitrogen-doped carbon composite material plays an important role in limiting volume expansion. Although nitrogen doping cannot limit the volume change of the negative electrode material during the cycle process, the D Li+ / C-1 electrode shows that nitrogen doping can make more lithium ions be embedded into the electrode material in the same time, so that more uniform volume expansion occurs.

[0085] The present application uses silazane oligomer and resorcinol and formaldehyde as precursors, uses sol-gel (Sol-gel) method, and makes organic polysilazane oligomer (OPSZ 1001) and resorcinol formaldehyde resin (RF) occur co-hydrolysis condensation to prepare OPSZ / RF composite microspheres with uniform size, and obtains nitrogen-doped SiCNO / C composite material after high-temperature ceramicization. This method is easy to prepare SiCNO / C composite material with adjustable size (200-1000nm) and controllable carbon content (20-60wt%), and the C, Si, N and O elements in the SiCNO / C composite material are uniformly distributed in the composite microspheres, and the composite microspheres are used as lithium ion battery negative electrode material to study the lithiation / delithiation mechanism. Nitrogen doping is realized in the SiCNO / C composite material, which provides additional interface lithium storage active sites and improves the lithium ion diffusion rate. The SiCNO / C composite microspheres exhibit two lithium storage mechanisms of diffusion control and capacitance control. In addition, the spherical structure of the SiCNO / C composite microspheres also improves the structural stability of the composite material. Benefiting from the above advantages, the SiCNO / C composite microspheres, especially SiCNO / C-1, exhibit excellent rate performance and long-term stable cycle ability at large current density. The SiCNO / C-1 retains 587.0 mAh·g -1 at 1A·g -1 current density after 400 cycles, and the capacity retention rate is 67.5%.

[0086] In addition, SiO x / C composite microspheres are also prepared by the same synthesis method, and the SiO xThe charge-discharge performance of the two microspheres materials of / C and SiCNO / C-1 was compared. The results show that the SiCNO / C-1 composite microspheres have the most excellent electrochemical performance. After 100 charge-discharge cycles, the SiCNO / C-1 has a reversible capacity of 794.1 mAh·g -1 -1. Since the SiCNO / C-1 is doped with nitrogen element, the discharge specific capacity is significantly improved, indicating that nitrogen doping has an important influence on the improvement of lithium storage performance. In addition, the specific capacity of the SiO x / C composite microspheres without nitrogen doping in the two is attenuated to only 424.1 mAh·g -1 after 100 charge-discharge cycles, indicating that nitrogen doping can further improve the lithium storage performance of the material. The cycle impedance test of the above three materials shows that the SiCNO / C-1 has good structural stability, and the nitrogen doping improves the charge transfer dynamics performance of the composite material, so that it has a high lithium ion migration number, and reaches 4.23*10 -15 cm 2 ·s -1 .

[0087] Therefore, the organic polysilazane / phenolic resin composite micro / nano ceramic material, the preparation method and the application thereof, utilize (Sol-gel) method, and the organic silazane oligomer (OPSZ) and the resorcinol formaldehyde resin are co-condensed to prepare uniform organic polysilazane / phenolic resin (OPSZ / RF) microspheres. In the reaction process, the hydrogen bond interaction between silanol (-Si-OH) and phenol hydroxyl is easy to occur, so that the co-condensation of the two can occur, and the uniform OPSZ / RF polymer is formed. After high-temperature carbonization, the SiCNO / C composite microspheres are obtained. This method is easy to prepare the SiCNO / C composite material with adjustable size (200-1000 nm) and controllable carbon content (20-60 wt%), and various elements are uniformly distributed in the composite microspheres. The prepared SiCNO / C composite material shows high specific capacity and excellent cycle stability.

[0088] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application but not to limit it. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can still be modified or replaced by equivalents, and these modifications or replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. Organic polysilazane / phenol resin composite micro / nano ceramic material, characterized in that: The material is a spherical morphology, wherein C, N, O, Si four elements are uniformly distributed on the sphere; The preparation method of the organic polysilazane / phenolic resin composite micro / nano ceramic material comprises the following steps: Step one, preparing organic polysilazane / RF polymer; The specific operation of step one is: mixing ammonia, deionized water and anhydrous ethanol uniformly, then adding resorcinol to dissolve fully, stirring and mixing uniformly, then adding formaldehyde, adding silazane oligomer after reaction, continuing to react, placing the obtained product in a centrifuge after reaction, and washing with anhydrous ethanol to obtain organic polysilazane / RF polymer. In step one, the volume ratio of ammonia, deionized water and anhydrous ethanol is 0.1-0.3:10-30:5-16, the amount of resorcinol is 0.03-1g, the amount of formaldehyde is 0.05-0.15mL, and the amount of silazane oligomer is 0.5-1.0mL, and the reaction time is 10-12h. Step two, preparing SiCNO / C, i.e. organic polysilazane / phenolic resin composite micro / nano ceramic material. The specific operation of step two is: vacuum drying the organic polysilazane / RF polymer obtained in step one, placing the dried polymer in a quartz porcelain boat, carbonizing under nitrogen atmosphere to obtain SiCNO / C sample, grinding the obtained SiCNO / C sample, and ball milling after grinding into powder to obtain SiCNO / C.

2. The method of making an organopolysilazane / phenolic resin composite micro / nano ceramic material according to claim 1, wherein: Comprising the following steps: Step one, preparing organic polysilazane / RF polymer; Step two, preparing SiCNO / C, i.e. organic polysilazane / phenolic resin composite micro / nano ceramic material.

3. The method for preparing organopolysilazane / phenolic resin composite micro / nano ceramic materials according to claim 2, characterized in that: The specific operation of step one is: mixing ammonia, deionized water and anhydrous ethanol uniformly, then adding resorcinol to dissolve fully, stirring and mixing uniformly, then adding formaldehyde, adding silazane oligomer after reaction, continuing to react, placing the obtained product in a centrifuge after reaction, and washing with anhydrous ethanol to obtain organic polysilazane / RF polymer.

4. The method for preparing organopolysilazane / phenolic resin composite micro / nano ceramic materials according to claim 2, characterized in that: The specific operation of step two is: vacuum drying the organic polysilazane / RF polymer obtained in step one, placing the dried polymer in a quartz porcelain boat, carbonizing under nitrogen atmosphere to obtain SiCNO / C sample, grinding the obtained SiCNO / C sample, and ball milling after grinding into powder to obtain SiCNO / C.

5. The method for preparing organopolysilazane / phenolic resin composite micro / nano ceramic materials according to claim 3, characterized in that: In step one, the volume ratio of ammonia, deionized water and anhydrous ethanol is 0.1-0.3:10-30:5-16, the amount of resorcinol is 0.03-1g, the amount of formaldehyde is 0.05-0.15mL, and the amount of silazane oligomer is 0.5-1.0mL, and the reaction time is 10-12h.

6. The method for preparing organopolysilazane / phenolic resin composite micro / nano ceramic materials according to claim 3, characterized in that: In step one, the centrifuge speed is 5000-10000rpm / min, the centrifugation time is 5-20min, and the anhydrous ethanol washing time is 3-5 times.

7. The method for preparing organopolysilazane / phenolic resin composite micro / nano ceramic materials according to claim 4, characterized in that: In step two, the drying temperature is 50-100℃, the drying time is 18-20h, the carbonization temperature is 800-1000℃, the heating rate is 5-10℃ / min, the carbonization time is 3-5h, the grinding speed is 300rpm / min, and the ball milling time is 5-10h.

8. Use of organic polysilazane / phenol resin composite micro / nano ceramic material, characterized in that: The organic polysilazane / phenol resin composite micro / nano ceramic material of claim 1 is applied to a lithium ion battery negative electrode material.

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