Reduced graphene oxide and use thereof

Abstract

A first aspect of the present invention provides reduced graphene oxide. which undergoes the following steps: graphite oxidation, preparation of a cake, exfoliation, and carbonization reduction; the D95 and D50 particle sizes of the reduced graphene oxide satisfy: 5μm≤D50≤50μm, 20μm≤D95≤150μm; and / or the ratio of D95 to D50 satisfies: 2.1≤D95 / D50≤2.8. The reduced graphene oxide prepared via the present invention has a large specific surface area, low mass, and low density; when the reduced graphene oxide is used in the field of new energy materials, it can be guaranteed that the prepared reduced graphene oxide has excellent conductivity and resistivity as low as 2-5 mΩ·cm, preferably maintained at 2.20-4.00 mΩ·cm.

Description

A kind of reduced graphene oxide and its application Technical Field

[0001] The present invention relates to the technical field of graphene materials, and more particularly to reduced graphene oxide and applications thereof. Background Art

[0002] Reduced graphene oxide is a carbon material different from graphene. Reduced graphene oxide is indeed a type of graphene, and its properties are similar to those of graphene, such as good conductivity. Although it contains more defects than mechanical graphene produced by direct grinding of graphite and BCVD graphene powder produced by BCVD, the product obtained by reduced graphene oxide has fewer layers and better electrochemical properties than mechanical graphene, and has more advantages in production cost than BCVD graphene. For this reason, reduced graphene oxide has become a research focus.

[0003] At present, the preparation of reduced graphene oxide is mostly obtained by treating graphene oxide through a thermal reduction process. During the thermal treatment process, the arrangement of active groups such as oxygen-containing functional groups in graphene oxide is affected, which in turn affects the degree of graphene sheet exfoliation, affecting its specific surface area and other properties, resulting in limited applications of reduced graphene oxide. In order to further improve the specific surface area and other properties of reduced graphene oxide, Chinese invention patent CN115893395A discloses a high specific surface area reduced graphene oxide / carbon composite powder, its preparation method and application. In the disclosed patent, carbon nanotubes are intercalated in the graphene oxide dispersion, and the barrier effect of carbon nanotubes between the layers is used to further improve the specific surface area of ​​reduced graphene oxide, which can reach 1000m 2 / g. However, the introduction of carbon nanotubes through the disclosed patent increases the specific surface area, which greatly increases the production cost.

[0004] Therefore, preparing a reduced graphene oxide powder with large specific surface area, light weight and low density has become an important research.

[0005] Summary of the Invention

[0006] In order to solve the above technical problems, a reduced graphene oxide powder with large specific surface area, light weight, good conductivity and simple process is prepared. The first aspect of the present invention provides a reduced graphene oxide, which is obtained by the following steps: graphite oxidation, preparation of a cake, expansion, and carbonization reduction;

[0007] The carbonization reduction is carried out in a gas atmosphere or under vacuum conditions; the gas includes nitrogen, argon and other gases that do not react with graphene or graphene oxide.

[0008] The D95 and D50 particle sizes of the reduced graphene oxide satisfy:

[0009] 5μm≤D50≤50μm, 20μm≤D95≤150μm; and / or; the ratio of D95 to D50 particle size satisfies 2.1≤D95 / D50≤2.8.

[0010] In the present invention, the inventors, after a large amount of creative verification and research, finally found that the D50 particle size of the prepared reduced graphene oxide satisfies: 5μm≤D50≤50μm, and the D95 particle size satisfies 20μm≤D95≤150μm. The particle size range of the obtained product is relatively large, which further shows that when selecting the preparation raw materials, the requirements for the graphite particle size are relatively low, the raw materials are simple and easy to obtain, and the process conditions are easy to operate. Therefore, it is a practical and low-cost product.

[0011] In some preferred embodiments, the D95 and D50 particle sizes of the reduced graphene oxide satisfy 5 μm ≤ D50 ≤ 50 μm, 20 μm ≤ D95 ≤ 150 μm, and the ratio of D95 to D50 particle sizes satisfies 2.1 ≤ D95 / D50 ≤ 2.8. Further preferably, the ratio of D95 to D50 particle sizes of the reduced graphene oxide satisfies 2.3 ≤ D95 / D50 ≤ 2.7.

[0012] More preferably, when the particle size range of D95 and D50 is 5μm≤D50≤50μm and 20μm≤D95≤150μm, the values ​​of the ratio of D95 to D50 particle size can be listed as: 2.3, 2.32, 2.36, 2.38, 2.4, 2.5, 2.49, 2.5, 2.55, 2.58, 2.6, 2.62, 2.66, and 2.7.

[0013] In the present invention, the inventors have found that when the D95 and D50 particle sizes of the prepared reduced graphene oxide are in the range of 5 μm ≤ D50 ≤ 50 μm and 20 μm ≤ D95 ≤ 150 μm, the ratio of D95 to D50 particle size is in the range of 2.3 to 2.7, which can further ensure that the specific surface area of ​​the prepared reduced graphene oxide is greater than 200 μm. 2 / g, preferably, its specific surface area is 200~1000m 2 / g, under the premise of having both, it is guaranteed that graphene materials with excellent electrical properties, high temperature resistance and high voltage performance can be prepared, which makes it possible for them to be used in batteries.

[0014] In some preferred embodiments, the puffing temperature is 200-800°C; the puffing temperature can be listed as: 200°C, 210°C, 220°C, 245°C, 280°C, 300°C, 350°C, 375°C, 390°C, 400°C, 405°C, 445°C, 460°C, 490°C, 500°C, 550°C, 600°C, 625°C, 675°C, 690°C, 700°C, 720°C, 745°C, 780°C, and 800°C.

[0015] Preferably, the puffing reaction time is 4 to 30 min, for example: 4 min, 5 min, 6 min, 8 min, 10 min, 12 min, 13.5 min, 15 min, 18 min, 19.5 min, 20 min, 21 min, 23.5 min, 25 min, 27 min, 30 min.

[0016] In some preferred embodiments, the expanded product is expanded graphene, and the volume of the expanded graphene is 100 to 350 times that of the graphene before expansion.

[0017] In this invention, the inventors discovered that after the expansion step, the volume of the resulting expanded graphene undergoes a significant change, reaching 100 to 400 times its pre-expansion volume. The inventors speculate that this is because the graphene oxide is rich in oxygen-containing functional groups between its layers and on its surface. During heating, these oxygen-containing groups break and release, causing the internal pressure of the graphene sheets to increase and expand. At an expansion temperature of 200-800°C and a reaction time of 4 to 30 minutes, the graphene oxide deoxygenation reaction becomes more intense, and the expansion of the sheets reaches 100 to 350 times. This further demonstrates that the expansion reaction in this invention is sufficient, thereby ensuring a large specific surface area for the resulting reduced graphene oxide. This ensures that this material exhibits superior electrical performance in electrochemical applications, as demonstrated by good battery capacity retention at various rates and excellent expansion suppression under high temperature and high pressure.

[0018] In some preferred embodiments, based on the mass of the reduced graphene oxide, the sum of the contents of all elements in the reduced graphene oxide except the element C is 0.5-1.5%; preferably, based on the mass of the reduced graphene oxide, the sum of the contents of all elements in the reduced graphene oxide except the element C is 0.8-1.2%.

[0019] More preferably, based on the mass of the reduced graphene oxide, the sum of the contents of all elements in the reduced graphene oxide except the C element can be exemplified as follows: 0.56%, 1.26%, 1.36%, 1.44%, 1.48%, etc.

[0020] In some preferred embodiments, the reduced graphene oxide contains O element, which accounts for only 0.2% to 0.8% of the mass of the reduced graphene oxide based on the mass of the reduced graphene oxide.

[0021] In the present invention, the reduced graphene oxide prepared through the oxidation, expansion, and carbonization reduction steps has an extremely low impurity content, especially the O element, which accounts for 0.2% to 0.8% of the mass of the reduced graphene oxide, and its content value will not affect the application of the reduced graphene oxide.

[0022] Raman spectroscopy is widely used in the analysis of carbon materials. -1 ) represents the disorder in the graphene sample structure. G peak (1595 cm -1 ) comes from E 2g Phonon plane vibration reflects the symmetry and order (degree of graphitization) of the material. It is usually expressed as the ratio of the D peak to the G peak intensity (I D / I G ) measures the order and integrity of graphene materials.

[0023] In some preferred embodiments, the Raman spectrum of the reduced graphene oxide is between 1250 and 1450 cm -1 The intensity value of D peak in the wavelength range is I D and at 1500~1700cm -1 The intensity value of the G peak within the wavelength range I G The relationship satisfies: 0.2≤I D / I G ≤1.2; preferably, the intensity value of the D peak I D and the intensity value of G peak I G The relationship satisfies: 0.25≤I D / I G ≤1.0; specific I D / I G The values ​​that can be listed include: 0.26, 0.53, 0.8, 0.85, 0.91, 0.93, 0.96, 1.0, etc.

[0024] In the present invention, the GOA type graphene oxide cake purchased by Yunnan Yuntian Mo Rui Technology Co., Ltd. is puffed and carbonized to reduce the defects of the product, ensuring that the intensity value of the D peak is 1 D The intensity value of G peak I G The relationship satisfies 0.2≤I D / I GWhen ≤1.2, the prepared reduced graphene oxide can have a special ordered and complete structure, which ensures its excellent conductive properties when used in the field of new energy materials. In particular, the intensity value of the D peak is I D The intensity value of G peak I G The relationship satisfies 0.25≤I D / I G When ≤1.0, the resistivity of the prepared reduced graphene oxide can be guaranteed to be as low as 2-5 mΩ·cm. Preferably, it is maintained at 2.20~4.00 mΩ·cm, ensuring its use in the fields of new energy batteries and the like.

[0025] In some preferred embodiments, the carbonization reduction process lasts for 0 to 12 hours; more preferably, it lasts for 2 to 10 hours. In some preferred embodiments, the carbonization reduction process is performed at a temperature of 900 to 1400°C. The carbonization temperature and time are important factors affecting the resistivity of reduced graphene oxide. Generally speaking, the more complete the carbonization, the lower the powder resistivity.

[0026] In some preferred embodiments, the specific surface area of ​​the reduced graphene oxide is greater than 200 m 2 / g, preferably 200~1000m 2 / g.

[0027] In some preferred embodiments, the expanded bulk density of the reduced graphene oxide is 0.005-0.01 g / m 3 .

[0028] As a preferred embodiment, the reduced graphene oxide is obtained by puffing and carbonizing a graphene oxide cake.

[0029] As a preferred embodiment, the puffing temperature is 600-800°C, the puffing time is 20-35 minutes, the carbonization temperature is 900-1400°C, and the carbonization time is 0-12 hours.

[0030] As a preferred embodiment, the puffing temperature is 500-700°C, the puffing time is 15-25 minutes, the carbonization temperature is 900-1400°C, and the carbonization time is 0-12 hours.

[0031] As a preferred embodiment, the puffing temperature is 300-500°C, the puffing time is 10-20 minutes, the carbonization temperature is 900-1400°C, and the carbonization time is 0-12 hours.

[0032] As a preferred embodiment, the puffing temperature is 200-400° C., the puffing time is 2-10 min, the carbonization temperature is 900-1400° C., and the carbonization time is 0-12 h.

[0033] In the Raman spectrum, the 2D peak (2700 cm -1 ) corresponds to the layer thickness of graphene. 2D / I G Determine the number of graphene layers.

[0034] In some preferred embodiments, the number of layers of the reduced graphene oxide is 1 to 10; or the Raman spectrum of the reduced graphene oxide is between 2600 and 2800 cm -1 The intensity value of the 2D peak within the wavelength range is I 2D and at 1500~1700cm -1 The intensity value of the G peak within the wavelength range I G The relationship satisfies: 0.05≤I 2D / I G ≤0.5. A second aspect of the present invention provides an application of reduced graphene oxide for use in thermal management materials, optoelectronic materials, flexible sensors, and biotechnology.

[0035] Beneficial effects: The reduced graphene oxide provided by the present invention has the following advantages:

[0036] 1) The reduced graphene oxide prepared by the present invention has a large specific surface area, light weight and low density. When used in the field of new energy materials, it can ensure that the prepared reduced graphene oxide has excellent electrical conductivity, with a resistivity as low as 2-5 mΩ·cm, preferably maintained at 2.20~4.00 mΩ·cm.

[0037] 2) The reduced graphene oxide prepared by the present invention has low requirements for raw graphite. The D95 and D50 particle sizes of the reduced graphene oxide can satisfy 5μm≤D50≤50μm and 20μm≤D95≤150μm, and the raw materials can be selected from a wide range and are easy to obtain.

[0038] 3) The reduced graphene oxide prepared by the present invention has a low impurity content in the raw graphite. Based on the mass of the reduced graphene oxide, the content of the O element is 0.2% to 0.8%, which improves the application value and application range of the reduced graphene oxide.

[0039] 4) The Raman spectrum of the reduced graphene oxide prepared by the present invention is between 1250 and 1450 cm -1 The intensity value of D peak in the wavelength range is I D and at 1500~1700cm -1The intensity value of the G peak within the wavelength range I G The relationship satisfies: 0.2≤I D / I G ≤1.2; preferably, the intensity value of the D peak I D and the intensity value of G peak I G The relationship satisfies: 0.25≤I D / I G ≤1.0, the prepared reduced graphene oxide has a special ordered and complete structure, which ensures its high application value in the field of new energy materials;

[0040] 5) The method of the present invention can prepare reduced graphene oxide with different specific surface areas, including 200~300m 2 / g, 300~400 m 2 / g, 400~500 m 2 / g, >500 m 2 / g of different products, and ensure that the specific surface area is 200~300m 2 / g, 300~400 m 2 / g of reduced graphene oxide has excellent performance in inhibiting battery expansion under high temperature and high pressure, which is much higher than that of array CNT; the specific surface area is 300~400m 2 / g of reduced graphene oxide has excellent performance in inhibiting battery expansion under high temperature and high pressure; the specific surface area is 400~500m 2 / g and surface area >500m 2 The rate performance of reduced graphene oxide with a density of / g is ideal, and its high-rate performance is much higher than that of array CNT.

[0041] BRIEF DESCRIPTION OF THE DRAWINGS

[0042] FIG1 is a Raman spectrum of reduced graphene oxide obtained in Example 1;

[0043] FIG2 is a graph showing the carbon content test results of the reduced graphene oxide obtained in Example 1;

[0044] FIG3 is a Raman spectrum of reduced graphene oxide obtained in Example 2;

[0045] FIG4 is a graph showing the carbon content test results of the reduced graphene oxide obtained in Example 2;

[0046] FIG5 is a Raman spectrum of reduced graphene oxide obtained in Example 3;

[0047] FIG6 is a graph showing the carbon content test results of the reduced graphene oxide obtained in Example 3;

[0048] FIG7 is a Raman spectrum of reduced graphene oxide obtained in Example 4;

[0049] FIG8 is a graph showing the carbon content test results of the reduced graphene oxide obtained in Example 4;

[0050] Figures 9 to 12 are particle size distribution test diagrams of Examples 1 to 4, wherein Figure 9 corresponds to Example 1, Figure 10 corresponds to Example 2, Figure 11 corresponds to Example 3, and Figure 12 corresponds to Example 4;

[0051] FIG13 is a graph showing voltammetric cycling tests of Examples 1 and 2 and the CNT array;

[0052] FIG14 is a comparison diagram of the percolation thresholds of Example 3-4 and array CNT. DETAILED DESCRIPTION

[0053] In the present invention, any range or endpoint value disclosed is not limited to the exact range or value, and these ranges or values ​​should be understood to include values ​​close to these ranges or values.

[0054] In the present invention, the specific surface area of ​​reduced graphene oxide is tested using a JW-BK200B instrument under the following test conditions: 250°C / 2.5h treatment, using high-purity nitrogen for adsorption;

[0055] In the present invention, Raman spectroscopy was performed using a German WiTech alpha300R instrument. The test conditions were as follows: argon ions were used as the laser source, the wavelength was 532 nm, the laser power was 10 mV attenuated to 10%, and the test range was 100–3200 cm -1 ;

[0056] In the present invention, the resistivity is measured using an ST2722-SZ four-probe powder resistivity tester;

[0057] In the present invention, the carbon content and oxygen content are tested by an X-ray electron spectrometer, model ESCAlab250, under the following test conditions: the base pressure is 3×10 -8 In the Pa energy analysis mode, A1 Kα 1486.8eV X-rays were used as the excitation source to test the chemical composition of the samples;

[0058] In the present invention, the expanded product is expanded graphene, and its expanded volume is calculated by V=m / ρ. The density of the material before and after expansion is tested according to the GB / T21354-2008 method, and the volume change before and after expansion is obtained by m / ρ. The volume of the expanded graphene is 100 to 400 times that before expansion.

[0059] Example Example 1

[0060] A method of reducing graphene oxide, comprising the following steps:

[0061] Raw material selection: GOA graphene oxide cake purchased by Yunnan Yuntian Mo Rui Technology Co., Ltd. was selected as the production raw material;

[0062] Puffing: Puffing is carried out in a puffing furnace, the puffing temperature is set to 250℃, and the puffing time is 3 minutes;

[0063] Carbonization reduction: Carbonization reduction is carried out in a carbonization furnace at a carbonization temperature of 1350°C for 8 hours to obtain reduced graphene oxide.

[0064] The D50 particle size of reduced graphene oxide is 39.059 μm; the test method refers to GB / T19077-2016;

[0065] The D95 particle size of reduced graphene oxide is 95.938 μm; the test method refers to GB / T19077-2016;

[0066] The specific surface area of ​​reduced graphene oxide is 243.901m 2 / g; Test method reference GB / T19077-2017;

[0067] The volume of the expanded graphene is 115 times that before expansion;

[0068] The resistivity of the reduced graphene oxide is 2.685 mΩ·cm, and the test method is based on GB / T 39978-2021;

[0069] FIG1 is a Raman spectrum of reduced graphene oxide in Example 1. As can be seen from FIG1 , the D peak (1335 cm -1 ) and G peak (1595 cm -1 ) has an intensity ratio of I D / I G = 0.29; 2D peak (2700 cm -1 ) and G peak (1595 cm -1 ) has an intensity ratio of I 2D / IG =0.122;

[0070] The number of layers of reduced graphene oxide is less than 10;

[0071] Figure 2 is a carbon content test chart of reduced graphene oxide in Example 1, which is obtained by XPS test. Based on the mass of the reduced graphene oxide, the carbon content is 98.74%, and the sum of the contents of all elements except the C element is 1.26%; based on the mass of the reduced graphene oxide, the content of the O element is 0.34%. Example 2

[0072] A method of reducing graphene oxide, comprising the following steps:

[0073] Raw material selection: GOA graphene oxide cake purchased by Yunnan Yuntian Mo Rui Technology Co., Ltd. was selected as the production raw material;

[0074] Puffing: Puffing is carried out in a puffing furnace, the puffing temperature is set to 400°C, and the puffing time is 10 minutes;

[0075] Carbonization reduction: Carbonization reduction is carried out in a carbonization furnace at a carbonization temperature of 1200°C and a carbonization time of 8 hours to obtain reduced graphene oxide.

[0076] The D50 particle size of reduced graphene oxide is 21.187 μm; the test method refers to GB / T19077-2016;

[0077] The D95 particle size of reduced graphene oxide is 56.277 μm; the test method refers to GB / T19077-2016;

[0078] The specific surface area of ​​reduced graphene oxide is 387.336 m 2 / g; Test method reference GB / T19077-2017

[0079] The volume of the expanded graphene is 142 times that before expansion;

[0080] The resistivity of the reduced graphene oxide is 3.065 mΩ·cm, and the test method refers to GB / T 39978-2021;

[0081] FIG3 is a Raman spectrum of reduced graphene oxide in Example 2. As can be seen from FIG3 , the D peak (1335 cm -1 ) and G peak (1595 cm -1 ) has an intensity ratio of I D / I G = 0.91; 2D peak (2700 cm -1 ) and G peak (1595 cm -1 ) has an intensity ratio of I 2D / IG =0.087

[0082] The number of layers of reduced graphene oxide is less than 6;

[0083] Figure 4 is a carbon content test chart of reduced graphene oxide in Example 2, obtained by XPS test. Based on the mass of the reduced graphene oxide, the carbon content is 98.64%, and the sum of the contents of all elements except the C element is 1.36%; based on the mass of the reduced graphene oxide, the content of the O element is 0.39%. Example 3

[0084] A method of reducing graphene oxide, comprising the following steps:

[0085] Raw material selection: GOA graphene oxide cake purchased by Yunnan Yuntian Mo Rui Technology Co., Ltd. was selected as the production raw material;

[0086] Puffing: Puffing is carried out in a puffing furnace, the puffing temperature is set to 600℃, and the puffing time is 20 minutes;

[0087] Carbonization reduction: Carbonization reduction is carried out in a carbonization furnace at a carbonization temperature of 1300°C and a carbonization time of 6 hours to obtain reduced graphene oxide.

[0088] The D50 particle size of reduced graphene oxide is 24.863 μm; the test method refers to GB / T19077-2016;

[0089] The D95 particle size of reduced graphene oxide is 61.864 μm; the test method refers to GB / T19077-2016;

[0090] The specific surface area of ​​reduced graphene oxide is 471.947 m 2 / g; Test method reference GB / T19077-2017

[0091] The volume of the expanded graphene is 217 times that before expansion;

[0092] The resistivity of the reduced graphene oxide is 3.530 mΩ·cm, and the test method is based on GB / T 39978-2021;

[0093] FIG5 is a Raman spectrum of reduced graphene oxide in Example 3. As can be seen from FIG5 , the D peak (1335 cm -1 ) and G peak (1595 cm -1 ) has an intensity ratio of I D / I G = 0.93; 2D peak (2700 cm -1 ) and G peak (1595 cm -1 ) has an intensity ratio of I 2D / IG =0.41

[0094] The number of layers of reduced graphene oxide is less than 5;

[0095] Figure 6 is a carbon content test chart of reduced graphene oxide in Example 3, which was obtained by XPS test. Based on the mass of the reduced graphene oxide, the carbon content is 99.35%, and the sum of the contents of all elements except the C element is 0.65%; based on the mass of the reduced graphene oxide, the content of the O element is 0.31%. Example 4

[0096] A method of reducing graphene oxide, comprising the following steps:

[0097] Raw material selection: GOA graphene oxide cake purchased by Yunnan Yuntian Mo Rui Technology Co., Ltd. was selected as the production raw material;

[0098] Puffing: Puffing is carried out in a puffing furnace, the puffing temperature is set to 800℃, and the puffing time is 30 minutes;

[0099] Carbonization reduction: Carbonization reduction is carried out in a carbonization furnace at a carbonization temperature of 1350°C for 10 h to obtain reduced graphene oxide.

[0100] The D50 particle size of reduced graphene oxide is 24.103 μm; the test method refers to GB / T19077-2016;

[0101] The D95 particle size of reduced graphene oxide is 57.256 μm; the test method refers to GB / T19077-2016;

[0102] The specific surface area of ​​reduced graphene oxide is 614.394 m 2 / g; Test method reference GB / T19077-2017;

[0103] The volume of the expanded graphene is 322 times that before expansion;

[0104] The resistivity of the reduced graphene oxide is 3.580 mΩ·cm, and the test method is based on GB / T 39978-2021;

[0105] FIG7 is a Raman spectrum of reduced graphene oxide in Example 4. As can be seen from FIG7 , the D peak (1335 cm -1 ) and G peak (1595 cm -1 ) has an intensity ratio of I D / I G = 0.96; 2D peak (2700 cm -1 ) and G peak (1595 cm -1 ) has an intensity ratio of I 2D / IG =0.274

[0106] The number of layers of reduced graphene oxide is less than 3;

[0107] Figure 8 is a carbon content test chart of reduced graphene oxide in Example 4, obtained by XPS test. Based on the mass of the reduced graphene oxide, the carbon content is 98.56%, and the sum of the contents of all elements except the C element is 1.44%; based on the mass of the reduced graphene oxide, the content of the O element is 0.33%. Comparative Example 1

[0108] A reduced graphene oxide, the specific embodiment of which is the same as that of Example 1, except that a raw material screening step is performed before puffing, and the prepared powder has a D95 of 14.048 μm, a D50 of 7.841 μm, and a D95 / D50 of 1.79. The prepared reduced graphene oxide has a specific surface area of ​​258.137. While the specific surface area of ​​the product is not significantly improved, the cost is increased by 80% compared with Example 1. Comparative Example 2

[0109] A reduced graphene oxide, the specific implementation of which is the same as that of Example 1, except that the reduced graphene oxide is expanded in an expansion furnace, the expansion temperature is set to 150°C, the expansion time is set to 3 minutes, and the specific surface area of ​​the reduced graphene oxide prepared is 190.256 m 2 / g, the specific surface area of ​​the powder decreases, and the battery rate performance also decreases accordingly. Comparative Example 3

[0110] A reduced graphene oxide, the specific implementation of which is the same as that of Example 1, except that: carbonization reduction is carried out in a carbonization furnace, the carbonization temperature is 800 ° C, the carbonization time is 2 h, and the reduced graphene oxide D peak (1335 cm -1 ) and G peak (1595 cm -1 ) has an intensity ratio of I D / I G =1.45, which means that the defectivity of the product increases. As the powder defects increase, the resistivity increases, and the conductive performance of the product also decreases. Application Cases

[0111] Examples 1 to 4 and arrayed carbon nanotubes (hereinafter referred to as arrayed CNTs) were used for electrical performance testing. The arrayed CNTs in the application case were purchased from Qingdao Chaorui Nano New Materials Technology Co., Ltd. Due to their good electrical conductivity and high specific surface area, arrayed CNTs are one of the best performing and most widely used conductive agents on the market today.

[0112] The test methods for rate performance and high temperature expansion performance are as follows:

[0113] S1. Preparation of conductive agent:

[0114] The powders of Example 3, Example 4 and the array CNT were uniformly dispersed in NMP to prepare a conductive agent with a carbon content of 1.0%.

[0115] S2. Preparation of positive electrode sheet:

[0116] S21. Prepare the slurry in the digital mixer tank according to the following mass ratios: the positive electrode main material (NCM-523) accounts for 97.5%; the adhesive PVDF-900 (using an NMP solution containing 5% by mass of PVDF) accounts for 1.5%; the conductive material (solid content) accounts for 1wt%; and NMP is appropriate. After mixing all the materials, mix them evenly in the mixer;

[0117] S22, coating: Cut the aluminum foil into appropriate lengths using a paper cutter, lay it flat on the coating machine, and use a four-sided coater (250μm) to coat the positive electrode slurry on the aluminum foil.

[0118] S23. The coated positive electrode sheet is transferred to an oven (105°C, 2h) to dry the solvent to obtain a positive electrode sheet. The positive electrode sheet is appropriately rolled on a roller base and then cut into multiple 12μm circular sheets using a sheet cutter. The sheet is weighed and sieved, and then dried again (60°C, 0.5h) to remove moisture and then placed in a glove box.

[0119] S3. Battery preparation:

[0120] S31, button battery assembly (its structure is negative electrode shell, thin gasket, lithium sheet, diaphragm, positive electrode sheet, thick gasket, spring, positive electrode shell): battery assembly amine the above structure is assembled, first place the negative electrode on the positive side, place the thin gasket, lithium sheet, then drip the electrolyte, place the positive electrode sheet, place the thick gasket, place the spring, and finally buckle the positive electrode shell.

[0121] S32. Place the assembled battery on a tablet press, press the assembled button cells together, then take them out, wipe off the electrolyte on the surface with ethanol, and let them stand for one day;

[0122] S4. Battery test:

[0123] The battery was loaded onto the Blue Electric test platform and subjected to 0.1C, 0.2C, 1C, 3C, 5C, and 7C discharge tests. After the test, the data was collated and analyzed.

[0124] S5, high temperature expansion characterization;

[0125] S51. Modify the clamp. Connect the working electrode of the electrochemical workstation to the positive electrode of the flat head clamp (red wire), and the reference electrode and counter electrode to the negative electrode of the flat head clamp (black wire). Place the flat head clamp in a 45°C oven to simulate the high temperature working environment of the battery, and load the button battery to be tested.

[0126] S52, start the CHI program, open the electrochemical workstation, select the program OCPT-open circuit potential-time, test the battery open circuit voltage, save the data, and end the program;

[0127] S53. Select the program CV-cyclic voltammetry, enter the initial voltage value lnit (V) (this value is the open circuit voltage), enter the maximum voltage limit value as 5V, enter the minimum limit value as 3.5V, enter the final voltage value as 3.5V, select the initial scan direction; lnital scan polarity (select anode positive), set the scan rate to 0.0001V / s, set the Sweep segments value to 4, keep other unchanged, start the program, save the data after completion, and compare its oxidation peak position and intensity.

[0128] Permeation threshold test:

[0129] S1. Example 1, Example 2, and the arrayed CNTs were uniformly dispersed in NMP to prepare a conductive agent with a carbon content of 1.0%. A positive electrode slurry was prepared according to different conductive agent addition amounts (0.2%, 0.4%, 0.6%, 0.8%, 1.0%, and 1.2%), coated on a PET film, and dried.

[0130] S2. Measure the thickness of the PET film, measure the thickness of the positive electrode coating / PET film, and calculate the thickness of the positive electrode coating;

[0131] S3. Start the four-probe resistivity tester, select the membrane resistivity test program, enter the positive electrode coating thickness value, enter other temperature and humidity parameters, start the test, test 8 values, remove the maximum and minimum values, and take the average of the remaining 6 data;

[0132] S4. Draw a line graph with the amount of conductive agent added as the horizontal axis and the resistivity of the sample film as the vertical axis to obtain the permeation threshold test curve.

[0133] The performance test results of application cases 1 to 4 and array CNT are as follows:

[0134] The battery expansion inhibition performance of Examples 1~2 and array CNT is shown in Figure 13. There are some irreversible redox side reactions in the charging and discharging process of lithium-ion batteries under specific temperature or voltage windows, such as the participation of battery materials in the reaction, catalytic decomposition of the electrolyte, and the uninterrupted growth of the SEI film. The voltammetric cycle test of the electrochemical workstation is used here to characterize the stability of the battery materials in the lithium-ion battery. Figure 13 is a characterization of the side reactions of the button battery. The higher the current, the more intense the side reaction, the more gas is generated, and the more the battery expands. As can be seen from Figure 13, the expansion inhibition performance of Examples 1~2 of the present application scheme is better than that of array CNT, and it can be better applied in high temperature and high pressure systems than array CNT.

[0135] The performance test results of Examples 3-4 and array CNT are as follows:

[0136] Table 1 shows the rate performance test results;

[0137] Table 1:

[0138] As can be seen from Table 1, the rate performance of Examples 3 and 4 is more ideal than that of the array CNT, especially the performance at high rate is more superior.

[0139] Figure 14 compares the percolation thresholds of Examples 3-4 and arrayed CNTs. Adjusting the amount of conductive agent affects its distribution within the cathode system; more conductive agent results in better conductivity. The lower the percolation threshold, the greater the ability of the conductive agent to form a conductive network. As shown in Figure 14, the percolation threshold of Examples 3-4 is significantly lower than that of arrayed CNTs, indicating superior conductivity compared to arrayed CNTs.

Claims

1. A reduced graphene oxide, characterized in that: The following steps are performed: the graphene oxide cake is expanded and carbonized and reduced to obtain; The D95 and D50 particle sizes of the reduced graphene oxide satisfy: 5μm≤D50≤50μm, 20μm≤D95≤150μm; and / or; the ratio of D95 to D50 particle size satisfies 2.1≤D95 / D50≤2.8; Preferably, the ratio of D95 to D50 satisfies: 2.3≤D95 / D50≤2.

7.

2. The reduced graphene oxide according to claim 1, characterized in that The puffing temperature is 200-800° C., and the puffing reaction time is 2-35 min. Preferably, the puffing reaction time is 3-30 min.

3. The reduced graphene oxide according to claim 2, characterized in that The product after expansion is expanded graphene, and the volume of the expanded graphene is 100 to 400 times that before expansion; preferably, the volume of the expanded graphene is 100 to 350 times that before expansion.

4. The reduced graphene oxide according to claim 1, characterized in that Based on the mass of the reduced graphene oxide, the sum of the contents of all elements in the reduced graphene oxide except the C element is 0.5-1.5%; preferably, based on the mass of the reduced graphene oxide, the sum of the contents of all elements in the reduced graphene oxide except the C element is 0.8-1.2%.

5. The reduced graphene oxide according to claim 4, characterized in that The reduced graphene oxide contains O element, and the content of the O element is 0.2% to 0.8% based on the mass of the reduced graphene oxide.

6. The reduced graphene oxide according to any one of claims 1 to 5, characterized in that The Raman spectrum of the reduced graphene oxide is between 1250 and 1450 cm -1 The intensity value of D peak in the wavelength range is I D and at 1500~1700cm -1 The intensity value of the G peak within the wavelength range I G The relationship satisfies: 0.2≤I D / I G ≤1.2; Preferably, the intensity value of the D peak I D and the intensity value of the G peak I G The relationship satisfies: 0.25≤I D / I G ≤1.

0.

7. The reduced graphene oxide according to claim 1, characterized in that The carbonization reduction time is 0 to 12 hours, and the preferred carbonization reaction time is 2 to 10 hours.

8. The reduced graphene oxide according to claim 1 or 7, characterized in that The temperature of the carbonization reduction is 900-1400°C.

9. The reduced graphene oxide according to claim 8, characterized in that The specific surface area of ​​the reduced graphene oxide is greater than 200 m 2 / g, preferably, its specific surface area is 200~1000m 2 / g.

10. The reduced graphene oxide according to claim 8, characterized in that The number of layers of the reduced graphene oxide is 1 to 10; or the Raman spectrum of the original graphene oxide is between 2600 and 2800 cm -1 The intensity value of the 2D peak in the wavelength range is I 2D and at 1500~1700cm -1 The intensity value of the G peak within the wavelength range I G The relationship satisfies: 0.05≤I 2D / I G ≤0.

5.

11. An application of the reduced graphene oxide according to any one of claims 1 to 10 in thermal management materials, optoelectronic materials, flexible sensors, biotechnology, and energy storage.

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