Porous graphite, preparation method thereof, electrode and battery

Abstract

The invention discloses porous graphite and a preparation method thereof, an electrode and a battery, and relates to the technical field of new energy. The preparation method of the porous graphite comprises the following steps: providing liquid resin and a liquid aromatic polymer, mixing, and sequentially carrying out heat treatment, carbonization treatment, graphitization treatment and activation treatment to obtain the porous graphite. According to the preparation method of the porous graphite provided by the embodiment of the invention, the porous graphite is prepared by taking the liquid resin and the liquid aromatic polymer as raw materials, multiple reactions of curing and aging of the resin and combination of the resin and the aromatic polymer occur in the heat treatment process, and the porous graphite is prepared in the carbonization process. Aromatic polymer molecules are rearranged into an ordered carbon layer, and resin cross-linked molecules form a hard carbon skeleton; in the graphitization process, the ordered carbon layer forms a graphite-like carbon layer, and the order degree of the hard carbon skeleton is not changed; in the activation process, the graphite-like carbon layer is difficult to etch, the hard carbon skeleton participates in the reaction to form a pore structure, and finally the porous graphite is prepared.

Description

Technical Field

[0001] This application relates to the field of new energy technology, and in particular to porous graphite and its preparation methods, electrodes and batteries. Background Technology

[0002] Porous graphite is a functional carbon material with abundant nanoscale to microscale pore structures. It retains the good electrical conductivity, thermal conductivity and chemical stability of graphite, and has high specific surface area, low density and excellent adsorption properties due to its well-developed pore structure. It is widely used in electrochemical energy storage (such as lithium-ion battery anodes and supercapacitors), adsorption separation, catalyst support and biomedicine.

[0003] Porous graphite exhibits unique advantages as a novel lithium-ion battery anode material when applied as an anode. Its uniqueness lies in the fact that lithium ions can be stored through two pathways: firstly, lithium ions can intercalate into the interlayer of graphite; secondly, lithium ions can fill the micropores of porous graphite as pseudometals, a characteristic that endows the material with a higher lithium storage capacity.

[0004] However, the preparation of porous graphite remains a major challenge. Graphite is chemically very stable, making it difficult to activate it to produce a rich porous structure. Furthermore, conventional soft carbon-based porous carbons almost completely lose their pores at the high temperatures of graphitization, making it difficult to form porous graphite. Summary of the Invention

[0005] In view of this, this application provides porous graphite and its preparation method, electrodes and batteries.

[0006] The embodiments of this application are implemented as follows: Firstly, the embodiments of this application provide a method for preparing porous graphite, comprising the following steps: Liquid resin and liquid aromatic polymer are provided, mixed, and then subjected to heat treatment, carbonization treatment, graphitization treatment and activation treatment in sequence to obtain the porous graphite.

[0007] Optionally, in some embodiments of this application, the liquid resin is a thermosetting resin; The liquid resin includes one or more of phenolic resin, furfural resin, furfural ketone resin, furfural alcohol resin, melamine-formaldehyde resin, and furfural-phenol resin; The solid content of the liquid resin is 50%~55%; The liquid aromatic polymer includes one or more of polyimide, polybenzimidazole, bismaleimide, polyaryletherketone, and para-aramid. The solid content of the liquid aromatic polymer is 25%-75%.

[0008] Optionally, in some embodiments of this application, the mass ratio of the liquid resin to the liquid aromatic polymer is 1:(3~5).

[0009] Optionally, in some embodiments of this application, the heat treatment includes a curing treatment, an aging treatment, and a cyclization treatment performed sequentially; wherein, The curing treatment, aging treatment, and cyclization treatment are performed at different temperatures; the temperatures of the curing treatment, aging treatment, and cyclization treatment increase sequentially.

[0010] Optionally, in some embodiments of this application, the curing temperature is 80°C to 100°C, and the curing time is 20h to 28h; The aging treatment temperature is 120℃~180℃, and the aging treatment time is 20h~28h; The cyclization treatment temperature is 250℃~350℃, and the cyclization treatment time is 2h~6h.

[0011] Optionally, in some embodiments of this application, the activation process includes introducing an activation gas; wherein, The activating gas includes water vapor or carbon dioxide; The flow rate of the activating gas is 12 mL / g / min to 18 mL / g / min.

[0012] Optionally, in some embodiments of this application, the heating rate of the carbonization treatment is 2℃ / min~5℃ / min, the temperature of the carbonization treatment is 1200℃~1400℃, and the time of the carbonization treatment is 4h~8h; The heating rate of the graphitization treatment is 10℃ / min~15℃ / min, the temperature of the graphitization treatment is 2800℃~3200℃, and the time of the graphitization treatment is 2h~6h. The activation treatment has a heating rate of 2℃ / min to 5℃ / min, an activation treatment temperature of 900℃ to 980℃, and an activation treatment time of 4h to 18h.

[0013] Secondly, embodiments of this application also provide a porous graphite, prepared by the above-described preparation method.

[0014] Thirdly, embodiments of this application also provide an electrode, the material of which includes porous graphite prepared by the above-described preparation method, or includes the above-described porous graphite.

[0015] Fourthly, embodiments of this application also provide a battery, the battery comprising a positive electrode, a negative electrode, a separator and an electrolyte, wherein the material of the negative electrode comprises porous graphite prepared by the above-described preparation method, or comprises the above-described porous graphite, or the negative electrode comprises the above-described electrode.

[0016] In the method for preparing porous graphite provided in this application embodiment, porous graphite is prepared using liquid resin and liquid aromatic polymer as raw materials. During the heat treatment of the liquid resin and liquid aromatic polymer, multiple reactions occur, including resin curing, aging of the cured resin to strengthen the cross-linked structure, and bonding of the liquid resin and liquid aromatic polymer. The mixture of the liquid resin and liquid aromatic polymer possesses both hard carbon and soft carbon components. During the carbonization process, the aromatic polymer molecules rearrange into ordered carbon layers, while the resin cross-linked molecules form a hard carbon framework, mutually... An inlaid structure is formed, and then during the graphitization process, the ordered carbon layer of the aromatic polymer molecules further aligns with the graphite structure to form a graphite-like carbon layer, while the hard carbon skeleton of the resin crosslinking molecules only shrinks drastically without changing its degree of order. In the subsequent activation process, the graphite-like carbon layer is difficult to be activated and etched, and the hard carbon skeleton participates in the reaction in large quantities to form a porous structure. Moreover, because the resin and aromatic polymer are evenly distributed in the inlaid structure, the uniformity of activation and pore formation can be ensured, and finally, porous graphite with suitable porosity and excellent electrochemical performance is obtained.

[0017] The embodiments of this application provide a reliable method for preparing porous graphite. The operation process is simple and can ensure the stable formation of a suitable pore structure in graphite, which is conducive to its widespread application. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a flowchart of a method for preparing porous graphite provided in an embodiment of this application. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. Furthermore, it should be understood that the specific embodiments described herein are only for illustration and explanation of this application and are not intended to limit this application.

[0021] In this application, unless otherwise stated, directional terms such as "upper" and "lower" generally refer to the upper and lower positions of the device in its actual use or operating state, specifically the orientation shown in the accompanying drawings; while "inner" and "outer" refer to the outline of the device. Furthermore, in the description of this application, the term "comprising" means "including but not limited to". The terms first, second, third, etc., are used merely as illustrative purposes and do not impose numerical requirements or establish a numerical order.

[0022] In this application, "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural.

[0023] In this application, "at least one" means one or more, and "more than one" means two or more. "One or more", "at least one of the following", or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0024] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0025] The technical solution of this application is as follows: Firstly, please refer to Figure 1 This application provides a method for preparing porous graphite, comprising the following steps: Step S11: Provide liquid resin and liquid aromatic polymer, mix them, and then perform carbonization, graphitization and activation treatments in sequence to obtain porous graphite.

[0026] In the method for preparing porous graphite provided in this application embodiment, porous graphite is prepared using liquid resin and liquid aromatic polymer as raw materials. During the heat treatment of the liquid resin and liquid aromatic polymer, multiple reactions occur, including resin curing, aging of the cured resin to strengthen the cross-linked structure, and bonding of the liquid resin and liquid aromatic polymer. The mixture of the liquid resin and liquid aromatic polymer possesses both hard carbon and soft carbon components. During the carbonization process, the aromatic polymer molecules rearrange into ordered carbon layers, while the resin cross-linked molecules form a hard carbon framework, mutually... An inlaid structure is formed, and then during the graphitization process, the ordered carbon layer of the aromatic polymer molecules further aligns with the graphite structure to form a graphite-like carbon layer, while the hard carbon skeleton of the resin crosslinking molecules only shrinks drastically without changing its degree of order. In the subsequent activation process, the graphite-like carbon layer is difficult to be activated and etched, and the hard carbon skeleton participates in the reaction in large quantities to form a porous structure. Moreover, because the resin and aromatic polymer are evenly distributed in the inlaid structure, the uniformity of activation and pore formation can be ensured, and finally, porous graphite with suitable porosity and excellent electrochemical performance is obtained.

[0027] The embodiments of this application provide a reliable method for preparing porous graphite. The operation process is simple and can ensure the stable formation of a suitable pore structure in graphite, which is conducive to its widespread application.

[0028] In step S11: It should be noted that the liquid resin and liquid aromatic polymer can be obtained directly through procurement, or obtained by melting or dissolving the solid resin and liquid aromatic polymer.

[0029] In some embodiments, the liquid resin is a thermosetting resin. A thermosetting resin is a high-molecular-weight polymer material whose molecular chains are chemically cross-linked to form a rigid three-dimensional network structure. This cross-linked structure cannot be repeatedly processed and molded during polymerization. Thermosetting resins facilitate subsequent carbonization to form a carbon skeleton and maintain their order during graphitization, which is beneficial for activation treatment to achieve pore-forming purposes.

[0030] In some embodiments, the liquid resin includes one or more of phenolic resin, furfural resin, furfural ketone resin, furfural alcohol resin, melamine-formaldehyde resin, and furfural-phenol resin.

[0031] In some embodiments, the solid content of the liquid resin is 50% to 55%, for example, it can be 50%, 51%, 52%, 53%, 54%, 55%, or any range between two of the above values. Within the range of solid content, the liquid resin has suitable fluidity, which facilitates processing and application, and allows for sufficient and uniform contact with the liquid aromatic polymer.

[0032] In some embodiments, the liquid aromatic polymer includes one or more of polyimide, polybenzimidazole, bismaleimide, polyaryletherketone, and para-aramid.

[0033] In some embodiments, the solid content of the liquid aromatic polymer is 25%-75%, for example, it can be 25%, 30%, 35%, 40%, 50%, 60%, 70%, 75%, or any range between two of the above values. Within the range of the solid content, the liquid aromatic polymer has suitable fluidity, which facilitates processing and application, and allows for sufficient and uniform contact with the liquid resin.

[0034] In some embodiments, the mass ratio of the liquid aromatic polymer to the liquid resin is (3~5):1, for example, it can be 3:1, 3.5:1, 4:1, 4.5:1, 5:1, or any range between two of the above ratios. Within the range of the mass ratio, it is beneficial for the liquid aromatic polymer and the liquid resin to have sufficient and uniform contact, which facilitates subsequent post-processing (carbonization treatment, graphitization treatment, and activation treatment) and avoids waste of raw materials.

[0035] In some embodiments, the heat treatment includes a curing treatment, an aging treatment, and a cyclization treatment performed sequentially. As described above, the curing treatment mainly involves the curing of the resin, the aging treatment mainly involves further aging of the cured resin to strengthen the cross-linked structure, and the cyclization treatment mainly involves the thorough and uniform mixing and contact of the aromatic polymer with the resin.

[0036] In some embodiments, the curing treatment, the aging treatment, and the cyclization treatment are performed at different temperatures. Further, the temperatures of the curing treatment, the aging treatment, and the cyclization treatment increase sequentially.

[0037] In some embodiments, the curing temperature is 80℃~100℃, for example, it can be 80℃, 85℃, 90℃, 95℃, 100℃ or any range between two of the above values; the curing time is 20h~28h, for example, it can be 20h, 22h, 24h, 25h, 26h, 28h or any range between two of the above values. Thus, under the curing conditions described, the curing of the liquid resin is facilitated.

[0038] In some embodiments, the aging treatment temperature is 120℃~180℃, for example, it can be 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, or any range between two of the above values; the aging treatment time is 20h~28h, for example, it can be 20h, 22h, 24h, 25h, 26h, 28h, or any range between two of the above values. Thus, under the conditions of the aging treatment, it is beneficial to further strengthen the cured resin.

[0039] In some embodiments, the cyclization treatment temperature is 250°C to 350°C, for example, 250°C, 260°C, 280°C, 300°C, 320°C, 350°C, or any range between two of the above values; the cyclization treatment time is 2 hours to 6 hours, for example, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, or any range between two of the above values. Thus, under the conditions of the cyclization treatment, it is beneficial for the aromatic polymer and the resin to mix and contact thoroughly and uniformly, and to exist stably.

[0040] It should be noted that the curing treatment, the aging treatment and the cyclization treatment can all be carried out in the same device, such as an oven. Only the temperature of the oven and the corresponding holding time need to be adjusted. The operation is very convenient and there is no need to frequently change equipment, thus avoiding losses.

[0041] In step S12: In some embodiments, the heating rate of the carbonization treatment is 2°C / min to 5°C / min, for example, it can be 2°C / min, 3°C / min, 4°C / min, 5°C / min, or any range between two of the above values; the temperature of the carbonization treatment is 1200°C to 1400°C, for example, it can be 1200°C, 1250°C, 1300°C, 1350°C, 1400°C, or any range between two of the above values; the time of the carbonization treatment is 4h to 8h, for example, it can be 4h, 5h, 6h, 7h, 8h, or any range between two of the above values. In other words, the carbonization treatment involves heating to 1200°C to 1400°C at a heating rate of 2°C / min to 5°C / min, and then holding at that temperature for 4h to 8h. Under these carbonization conditions, it is beneficial for the resin and aromatic polymer to further form an interlocking structure, wherein the aromatic polymer rearranges into ordered carbon layers, and the resin crosslinked molecules form a hard carbon framework, facilitating subsequent graphitization treatment.

[0042] In some embodiments, the carbonization process is carried out in an inert atmosphere to avoid the influence of oxygen on the product. The inert atmosphere may be an atmosphere created by nitrogen, argon, or the like.

[0043] It should be noted that the carbonization process can be carried out in a box furnace.

[0044] In some embodiments, the heating rate of the graphitization treatment is 10℃ / min to 15℃ / min, for example, it can be 10℃ / min, 11℃ / min, 12℃ / min, 13℃ / min, 14℃ / min, 15℃ / min, or any range between two of the above values; the temperature of the graphitization treatment is 2800℃ to 3200℃, for example, it can be 2800℃, 2900℃, 3000℃, 3100℃, 3200℃, or any range between two of the above values; the time of the graphitization treatment is 2h to 6h, for example, it can be 2h, 3h, 4h, 5h, 6h, or any range between two of the above values. In other words, the graphitization treatment involves heating to 3000℃ to 3400℃ at a heating rate of 10℃ / min to 15℃ / min, and then holding at that temperature for 2h to 6h. Thus, under the graphitization treatment conditions, it is beneficial for the ordered carbon layer of the aromatic polymer to further align with the graphite structure to form a graphite-like carbon layer, while the hard carbon skeleton of the resin crosslinking molecules only undergoes drastic shrinkage, maintaining a stable degree of order, which facilitates subsequent further activation treatment.

[0045] In some embodiments, the graphitization process is carried out in an inert atmosphere to avoid the influence of oxygen on the product. The inert atmosphere may be an atmosphere created by nitrogen, argon, or the like.

[0046] It should be noted that the graphitization process can be carried out in a graphitization furnace.

[0047] In some embodiments, the heating rate of the activation treatment is 2℃ / min to 5℃ / min, for example, it can be 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, or any range between two of the above values; the temperature of the activation treatment is 900℃ to 980℃, for example, it can be 900℃, 910℃, 920℃, 930℃, 940℃, 950℃, 960℃, 970℃, 980℃, or any range between two of the above values; the activation time is 4h to 18h, for example, it can be 4h, 5h, 6h, 8h, 10h, 12h, 15h, 18h, or any range between two of the above values. In other words, the activation treatment involves heating to 900℃ to 980℃ at a heating rate of 2℃ / min to 5℃ / min, then introducing an activation gas and holding at that temperature for 4h to 18h. Thus, under the conditions of the activation treatment, the graphite-like carbon layer formed by the aromatic polymer is difficult to etch, while the hard carbon skeleton of the resin crosslinking molecules participates in the reaction in large quantities, thereby forming a porous structure and producing porous graphite.

[0048] In some embodiments, the activation process includes introducing an activation gas.

[0049] Furthermore, the activating gas includes water vapor or carbon dioxide.

[0050] Furthermore, the flow rate of the activating gas is 12 mL / g / min to 18 mL / g / min, for example, it can be 12 mL / g / min, 13 mL / g / min, 14 mL / g / min, 15 mL / g / min, 16 mL / g / min, 17 mL / g / min, 18 mL / g / min, or any range between two of the above values. Within the aforementioned flow rate range, it is beneficial for the activating gas and the graphitized material to fully and uniformly contact, resulting in uniform pore-forming treatment. It should be noted that "mL / g / min" represents the volume of activating gas that comes into contact with each gram of material per minute.

[0051] It should be noted that the activation treatment can be carried out in a tube furnace.

[0052] Secondly, embodiments of this application also provide a porous graphite, which is prepared by the above-described method for preparing porous graphite.

[0053] The porous graphite provided in this application has a suitable specific surface area and pore distribution, and can exhibit excellent electrochemical performance in batteries.

[0054] Thirdly, embodiments of this application also provide an electrode, the material of which includes porous graphite prepared by the above-described preparation method, or includes the above-described porous graphite.

[0055] Fourthly, embodiments of this application also provide a battery, the battery comprising a positive electrode, a negative electrode, a separator and an electrolyte, wherein the material of the negative electrode comprises porous graphite prepared by the above-described preparation method, or comprises the above-described porous graphite, or the negative electrode comprises the above-described electrode.

[0056] The positive electrode, separator, and electrolyte can be made of conventional materials in this field.

[0057] The embodiments of this application use the porous graphite prepared above as the negative electrode of the battery, which can effectively improve the first discharge efficiency of the battery and increase the specific capacity of the battery.

[0058] The present application will be specifically described below through specific embodiments. The following embodiments are only some embodiments of the present application and are not intended to limit the present application.

[0059] Porous graphite Example 1 This embodiment of porous graphite provides a porous graphite, and the preparation method of porous graphite includes the following steps: Step S21: Mix liquid furfural resin with a solid content of 50% with liquid polyimide with a solid content of 55%, wherein the mass ratio of liquid polyimide to liquid furfural resin is 4:1. After mixing, transfer the mixture to an oven and cure at 100℃ for 24h, age at 160℃ for 24h, and cyclize at 270℃ for 4h to obtain the mixture. Step S22: Transfer the mixture into a box furnace and heat it to 1200℃ at a heating rate of 5℃ / min under a nitrogen atmosphere, holding it at that temperature for 4 hours for carbonization. Transfer the resulting carbonized material into a graphitization furnace and heat it to 3000℃ at a heating rate of 15℃ / min under an argon atmosphere, holding it at that temperature for 4 hours for graphitization. Transfer the resulting graphitized material into a tube furnace and heat it to 900℃ at a heating rate of 5℃ / min under a nitrogen atmosphere. Introduce 18 mL / g / min of nitrogen-loaded activation gas water vapor into the tube furnace, continuously introduce it, and hold it at that temperature for 18 hours for activation treatment to obtain porous graphite.

[0060] Porous graphite Example 2 This porous graphite embodiment is basically the same as porous graphite embodiment 1, except that the liquid furfural resin in step S21 is replaced with liquid furfural ketone resin.

[0061] Porous graphite Example 3 This porous graphite embodiment is basically the same as porous graphite embodiment 1, except that the liquid furfural resin in step S21 is replaced with liquid melamine-formaldehyde resin.

[0062] Porous graphite Example 4 This porous graphite embodiment is basically the same as porous graphite embodiment 1, except that the liquid polyimide in step S21 is replaced with liquid para-aramid.

[0063] Porous graphite Example 5 This porous graphite embodiment is basically the same as porous graphite embodiment 1, except that the liquid polyimide in step S21 is replaced with liquid polybenzimidazole.

[0064] Porous graphite Example 6 This porous graphite embodiment is basically the same as porous graphite embodiment 1, except that the activation gas water vapor is replaced with carbon dioxide in step S22.

[0065] Porous graphite Example 7 This porous graphite embodiment is basically the same as porous graphite embodiment 1, except that the mass ratio of liquid polyimide to liquid furfural resin in step S21 is 5:1.

[0066] Porous graphite Example 8 This porous graphite embodiment is basically the same as porous graphite embodiment 1, except that the mass ratio of liquid polyimide to liquid furfural resin in step S21 is 3:1.

[0067] Porous graphite comparative example 1 This porous graphite comparative example is basically the same as that of porous graphite example 1, except that step S21 is not performed, and the mixture in step S22 is replaced with liquid furfural resin in step S21.

[0068] Porous graphite comparative example 2 This porous graphite comparative example is basically the same as that of porous graphite example 1, except that step S21 is not performed, and the mixture in step S22 is replaced with liquid polyimide.

[0069] The specific surface area, pore distribution, and graphitization degree (ID / IG) of porous graphite Examples 1-8 and Comparative Examples 1-3 were tested, and the results are shown in Table 1.

[0070] The specific surface area and pore size distribution were tested using the following methods: Nitrogen adsorption-desorption isotherms were measured at 77 K using a Micromeritcs Tristar 3030 instrument. Before measurement, the samples were degassed under vacuum at 200 °C for 10 h. The specific surface area was calculated using the Brunauer-Emmett-Teller (BET) method and adsorption curve branching data within a relative pressure range of P / P0 of 0.005–1. The pore size distribution was analyzed from the adsorption curves using the Density Function Theory (DFT) model, and pore volume and average pore size data were recorded.

[0071] The degree of graphitization (ID / IG) was measured using Raman spectroscopy. ID / IG is defined as the intensity ratio of the D peak to the G peak in the Raman spectrum, where the D peak corresponds to structural defects or disordered carbon, while the G peak reflects the ordered graphite lattice. The lower the ID / IG, the higher the degree of graphitization.

[0072] Table 1

[0073] As shown in Table 1, based on Examples 1-6 and Comparative Examples 1-2 of porous graphite, this method involves mixing liquid resin and liquid aromatic polymer, followed by curing, aging, and cyclization treatments to form a mixture of aromatic polymer and resin. This mixture is then subjected to carbonization, graphitization, and activation treatments to ultimately produce high-performance porous graphite with a suitable specific surface area and uniform pore distribution. It should be noted that in Comparative Example 1, porous graphite was prepared using only resin as a raw material. While the resin is easily activated to create pores, it is difficult to graphitize. In Comparative Example 2, porous graphite was prepared using only polyimide as a raw material, resulting in a higher degree of graphitization but difficulty in activation and pore creation. As can be seen from Examples 1, 7-8 and Comparative Examples 1-2 of porous graphite, by controlling the mass ratio of liquid resin and liquid aromatic polymer, the content of hard carbon and soft carbon in the post-processing can be controlled, thereby controlling the degree of graphitization and the degree of activation and pore formation. Within the mass ratio range provided in this application, porous graphite with suitable specific surface area and suitable pore distribution can be prepared, promoting the application of porous graphite.

[0074] Battery Example 1 This battery embodiment provides a button cell battery, including the following steps: The porous graphite of Example 1 and the material provided in the comparative example were mixed with styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC) and conductive carbon black (SP) in a mass ratio of 94.5:2.5:1.5:1.5. The mixture was prepared into a slurry with ultrapure water and coated onto a copper foil sheet. The prepared slurry coating was placed in a vacuum drying oven and dried at 90°C for 24 hours. After being pressed by a 5T roller, a circular electrode sheet with a diameter of 12 mm was pressed out using a tablet press to obtain the negative electrode of the experimental battery. Using lithium foil as the counter electrode and glass fiber disc as the separator, the lithium battery uses 1.0 mol / L LiPF6 mixed in a mixed solvent with a volume ratio of EC:DMC:EMC of 1:1:1 as the electrolyte. Springs and gaskets are added, and the batteries are assembled into 2032 model button batteries in a glove box.

[0075] Battery Examples 2-8 Battery Examples 2-8 are basically the same as Battery Example 1, except that the porous graphite of Porous Graphite Example 1 is replaced with the porous graphite of Porous Graphite Examples 2-8.

[0076] Battery Comparison 1~2 The battery comparative examples 1 and 2 are basically the same as battery example 1, except that the porous graphite of porous graphite example 1 is replaced with the porous graphite of porous graphite comparative examples 1 and 2.

[0077] The initial discharge efficiency, specific capacity, and capacity retention of the coin cells in battery examples 1-8 and battery comparative examples 1-2 were tested. The test results are shown in Table 2.

[0078] The test methods for initial discharge efficiency and specific capacity are as follows: Discharge specific capacity: Under a constant temperature environment of 25℃, the test is conducted using a Blue Electric tester. The device is charged and discharged twice at 0.01C within a voltage range of 0.01V to 2.00V. The ratio of the charge specific capacity to the discharge specific capacity of the first cycle is recorded as the initial discharge efficiency, and the discharge specific capacity of the second cycle is recorded as the specific capacity. The specific capacity after 200 cycles is taken as the ratio of the specific capacity of the first cycle and recorded as the capacity retention rate.

[0079] Table 2

[0080] As shown in Table 2, based on battery examples 1-6 and battery comparative examples 1-2, the porous graphite prepared in this method, when applied to the negative electrode of the battery, can effectively improve the initial discharge efficiency and increase the specific capacity of the battery. Even after multiple cycles, it maintains a high specific capacity. High-performance porous graphite can be prepared using different raw materials and the same preparation method, thus improving battery performance. In battery comparative example 1, porous graphite prepared solely from resin was applied to the negative electrode, resulting in a high specific capacity, but poor initial coulombic efficiency and capacity retention. In battery comparative example 2, porous graphite prepared solely from polyimide was applied to the negative electrode, resulting in high initial coulombic efficiency and capacity retention, but poor specific capacity. The porous graphite prepared by the preparation method provided in this application can maintain a better balance between specific capacity, initial coulombic efficiency, and capacity retention. As can be seen from battery examples 1, 7-8 and battery comparative examples 1-2, within the mass ratio range provided in this application, the resin and aromatic polymer in the mixture are uniformly distributed. Subsequently, corresponding changes can be made in the carbonization, graphitization and activation processes to obtain porous graphite, thereby improving the battery's first discharge efficiency, specific capacity and cycle life.

[0081] The technical solutions provided by the embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for preparing porous graphite, characterized in that, Includes the following steps: Liquid resin and liquid aromatic polymer are provided, mixed, and then subjected to heat treatment, carbonization treatment, graphitization treatment and activation treatment in sequence to obtain the porous graphite.

2. The preparation method according to claim 1, characterized in that, The liquid resin is a thermosetting resin; The liquid resin includes one or more of phenolic resin, furfural resin, furfural ketone resin, furfural alcohol resin, melamine-formaldehyde resin, and furfural-phenol resin; The solid content of the liquid resin is 50%~55%; The liquid aromatic polymer includes one or more of polyimide, polybenzimidazole, bismaleimide, polyaryletherketone, and para-aramid. The solid content of the liquid aromatic polymer is 25%-75%.

3. The preparation method according to claim 1, characterized in that, The mass ratio of the liquid resin to the liquid aromatic polymer is 1:(3~5).

4. The preparation method according to claim 1, characterized in that, The heat treatment includes sequentially performing a curing treatment, an aging treatment, and a cyclization treatment; wherein... The curing treatment, aging treatment, and cyclization treatment are performed at different temperatures; the temperatures of the curing treatment, aging treatment, and cyclization treatment increase sequentially.

5. The preparation method according to claim 4, characterized in that, The curing temperature is 80℃~100℃, and the curing time is 20h~28h; The aging treatment temperature is 120℃~180℃, and the aging treatment time is 20h~28h; The cyclization treatment temperature is 250℃~350℃, and the cyclization treatment time is 2h~6h.

6. The preparation method according to claim 1, characterized in that, The activation process includes introducing an activation gas; wherein... The activating gas includes water vapor or carbon dioxide; The flow rate of the activating gas is 12 mL / g / min to 18 mL / g / min.

7. The preparation method according to claim 1 or 6, characterized in that, The heating rate of the carbonization process is 2℃ / min to 5℃ / min, the temperature of the carbonization process is 1200℃ to 1400℃, and the time of the carbonization process is 4h to 8h. The heating rate of the graphitization treatment is 10℃ / min~15℃ / min, the temperature of the graphitization treatment is 2800℃~3200℃, and the time of the graphitization treatment is 2h~6h. The activation treatment has a heating rate of 2℃ / min to 5℃ / min, an activation treatment temperature of 900℃ to 980℃, and an activation treatment time of 4h to 18h.

8. A porous graphite, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 7.

9. An electrode, characterized in that, The electrode material includes porous graphite prepared by the preparation method according to any one of claims 1 to 7, or includes porous graphite as described in claim 8.

10. A battery, characterized in that, The battery includes a positive electrode, a negative electrode, a separator, and an electrolyte. The material of the negative electrode includes porous graphite prepared by the preparation method according to any one of claims 1 to 7, or includes porous graphite as described in claim 8, or the negative electrode includes the electrode as described in claim 9.

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