Negative electrode material and battery

Abstract

The application relates to a negative electrode material and a battery, the negative electrode material comprising graphite, the graphite having pores in the interior and / or on the surface, the average pore diameter of the pores being 0.1-10 nm, the oil absorption value O (mL / 100g) of the negative electrode material, the pore volume V (cm 3 / kg), the tap density T (g / mL) and the powder conductivity e (S / cm) of the negative electrode material under a pressure of 20 KN satisfying 9<=O*V*P / (T*e)<=55; the pore volume of the negative electrode material and the average pore diameter of the pores are tested by using an ASAP2460 device of American Micromeritics Company, the pore volume of the negative electrode material is calculated in a pore diameter range by using a BJH Desorption cumulative volume of pores model, and the average pore diameter of the pores is calculated by using a BJH Desorption model.

Description

Technical Field

[0001] The present application belongs to the technical field of negative electrode materials, and more specifically, relates to negative electrode materials and batteries. Background Art

[0002] During the graphitization process, volatiles and impurity elements in the raw materials escape under high temperature conditions, thereby forming pores inside and / or on the surface of the graphite. It is known to those skilled in the art that the pore volume of artificial graphite within a certain range can increase the Li + The diffusion channels of the pore volume promote the diffusion of lithium ions at the solid-liquid interface and within the solid phase, reducing concentration polarization, which is beneficial to improving the capacity and rate performance of the negative electrode material. Based on this, the applicant has found through in-depth research that simply meeting the pore volume requirement does not necessarily effectively improve rate performance.

[0003] Therefore, at the current stage when graphite materials have developed to a very mature stage, simply improving one parameter can no longer meet the market demand for low-cost, high-performance graphite materials. It is necessary to explore the mechanism of the coordinated action of multiple factors and develop graphite negative electrode materials that meet market demand. Summary of the Invention

[0004] The present application provides a negative electrode material and a battery. The negative electrode material of the present application can meet good processing performance while also having high-rate charge and discharge performance.

[0005] In a first aspect, the present application provides a negative electrode material, wherein the negative electrode material comprises artificial graphite, wherein the artificial graphite has pores, and the average pore size P of the pores is The oil absorption value O (mL / 100g), pore volume V (cm 3 / kg), tap density T (g / mL), and powder conductivity e (S / cm) of the negative electrode material under a pressure of 20KN satisfy: 9≤0*V*P / (T*e)≤55;

[0006] The pore volume and average pore diameter were measured using ASAP2460 equipment from American Micromeritics, where the BJH Desorption cumulative volume of pores model was used. The pore volume of the negative electrode material is calculated within the pore diameter range, and the average pore diameter of the pores is calculated using the BJH Desorption model.

[0007] In some embodiments, the pores are distributed inside and / or on the surface of the artificial graphite.

[0008] In some embodiments, the oil absorption value of the negative electrode material is 24 mL / 100 g to 49 mL / 100 g.

[0009] In some embodiments, the pore volume of the negative electrode material is 2 cm 3 / kg~4cm 3 / kg.

[0010] In some embodiments, the tap density of the negative electrode material is 1.00 g / mL to 1.50 g / mL.

[0011] In some embodiments, the powder conductivity of the negative electrode material under a pressure of 20 KN is 300 S / cm to 450 S / cm.

[0012] In some embodiments, the true density of the negative electrode material is 2.230 g / cm 3 ~2.260g / cm 3 .

[0013] In some embodiments, the median particle size D50 of the negative electrode material is 12 μm to 20 μm.

[0014] In some embodiments, the negative electrode material is measured by X-ray diffraction, and the interlayer spacing of the (002) plane of the negative electrode material is d 002 ,

[0015] In some embodiments, the negative electrode material is measured by X-ray diffraction, and the peak intensity ratio of the (004) plane to the (110) plane of the negative electrode material is I 004 / I 110 3 to 5.

[0016] In some embodiments, the negative electrode material includes artificial graphite primary particles and / or artificial graphite secondary particles.

[0017] In some embodiments, the pores include at least one of micropores and mesopores.

[0018] In some embodiments, the average pore size of the pores is

[0019] The technical solution of this application has at least the following beneficial effects:

[0020] It is known to those skilled in the art that graphite has a certain range of pore volume that can increase the Li +The diffusion channels promote the diffusion of lithium ions at the solid-liquid interface and in the solid phase, reduce concentration polarization, and are conducive to improving the capacity and rate performance of the negative electrode material. Based on this, the applicant has found through in-depth research that the rate performance may not be effectively improved if only sufficient pore volume is satisfied, because the improvement of battery rate performance is not only affected by the transmission of lithium ions, but also by the transmission of electrons. On the one hand, lithium ion deintercalation requires diffusion channels and reaction interfaces, and the negative electrode material is fully infiltrated with the electrolyte as a medium, thereby improving the transmission rate of lithium ions. However, in fact, some pores cannot be infiltrated by the electrolyte and cannot play their role. The influence of the pore size and surface morphology that cannot play their role may hinder electron transmission, increase resistance and reduce battery rate performance. On the other hand, the negative electrode material needs to transfer charge at the solid-liquid interface during use. In addition, if the negative electrode material has excellent conductivity during the electrode preparation process, the amount of conductive agent used in the electrode can be reduced, thereby increasing the battery capacity while improving the rate performance. Therefore, the negative electrode material is also required to have good conductivity. Only by balancing the pore structure and surface morphology of the negative electrode material particles and taking into account both ion and electron transport can the battery rate performance be further improved. In addition, too much porous structure will also lead to a decrease in the tap density of the graphite negative electrode material, resulting in poor processing performance during the preparation of slurry and electrodes, and ultimately causing poor battery cycle performance. Therefore, this application conducts a large number of experimental explorations on the combination of five factors: the average pore diameter of the pores, the pore volume of the negative electrode material, the oil absorption value, the tap density, and the powder conductivity, and controls the O*V*P / (T*e) of the negative electrode material within the range of 9 to 55. This means that the negative electrode material can fully utilize the advantages of the rich pore structure and good conductivity of the material itself to increase the lithium ion diffusion rate and faster charge transfer on the basis of ensuring the processing performance, and ultimately achieve the purpose of improving the high-rate charge and discharge performance of the graphite negative electrode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present application is further described below with reference to the accompanying drawings and examples.

[0022] Figure 1 This is a flow chart for preparing the negative electrode material of this application. DETAILED DESCRIPTION

[0023] In order to better understand the technical solution of the present application, the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0024] It should be clear that the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0025] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The singular forms "a", "an", "the" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0026] It should be understood that the term "and / or" as used herein is merely a description of the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, or B exists alone. Furthermore, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0027] For graphite negative electrode materials, the special layered structure of graphite determines the Li + It can only be embedded from the end face of the material and gradually diffuse into the interior of the particles, resulting in a low diffusion rate of lithium ions, poor rate performance and more prone to lithium precipitation, which can cause safety problems such as short circuit and thermal runaway. Therefore, a certain proportion of pores inside the graphite negative electrode helps to increase the lithium ion diffusion channel, thereby improving the performance of the graphite negative electrode and improving safety performance. Generally speaking, artificial graphite has a certain number of pore structures. On the one hand, the presence of pores can increase Li + The diffusion channel inside the graphite material reduces the Li + The diffusion resistance is reduced, thereby effectively improving the rate performance of the material. On the other hand, too much pore structure will lead to an increase in the specific surface area of ​​the material, which in turn leads to the deterioration of the product's first efficiency and cycle performance. Therefore, under the premise of a certain limit on the particle size of the graphite material, it is necessary to select a specific range of pore volume, which can enable the prepared graphite negative electrode material to have better rate performance. At present, most researchers stay at the exploration of the influence of a single factor on the performance of graphite materials. However, in the continuous research process of the applicant, it is found that simply improving the pore structure has limited improvement in rate performance and cannot meet people's increasingly rapid demand for high rate performance of graphite negative electrode materials.

[0028] In view of this, the applicant has explored the graphite negative electrode material by adopting a mechanism of action in which multiple factors work together, and has been able to develop a graphite negative electrode material with high rate performance, thereby meeting the market's increasingly rapid demand for graphite material rate performance.

[0029] The following is a detailed description of one of the preparation processes developed by the applicant and its related products.

[0030] A method for preparing a negative electrode material, such as Figure 1 As shown, the following steps are included:

[0031] S10. Ultrasonic treatment is performed on a mixture containing asphalt and alkali solution at 60°C to 80°C to obtain a first precursor, wherein the asphalt includes asphalt saturated fraction and asphalt aromatic fraction, the mass ratio of the asphalt saturated fraction to the asphalt aromatic fraction is (40-60): (60-40), and the molar concentration of the alkali solution is 0.01M to 0.05M.

[0032] S20, carbonizing the first precursor to obtain a second precursor.

[0033] S30, graphitizing the second precursor to obtain a negative electrode material.

[0034] In the above scheme, the preparation method of the negative electrode material provided in the present application is achieved by mixing a mixture of asphalt saturated components and asphalt aromatic components with a low concentration of alkali solution and then ultrasonically treating the mixture within a certain temperature range, so that the alkali solution etches the interior and surface of the asphalt in situ to form a pore structure. The existence of the pore structure is conducive to the formation of a rich and regular pore structure in the material, and realizes precise control of the pore volume and pore size, oil absorption value, tap density, and powder conductivity of the graphite material, which is conducive to improving the material's liquid absorption performance and high-rate charge and discharge performance, thereby meeting the needs of consumer and power-end customers for the fast charging performance of negative electrode materials.

[0035] Specifically, the preparation method of the present application is described in detail below with reference to the examples:

[0036] Step S10: ultrasonically treat the mixture containing asphalt and alkali solution at 60° C. to 80° C. to obtain a first precursor.

[0037] In the above steps, the mixture containing asphalt and alkali solution of a specific concentration is ultrasonically treated at 60°C to 80°C, so that the surface and interior of the asphalt material will be etched by the low-concentration alkali solution, forming a pore structure within a certain pore size range, which provides a good foundation for the synergistic effect of the pores in the subsequently prepared negative electrode material and the oil absorption value, tap density and powder conductivity of the material.

[0038] In some embodiments, the mixture containing asphalt and alkali solution is prepared by heating the asphalt saturated fraction and the asphalt aromatic fraction to 60° C. to 80° C. to soften them, and then adding alkali solution with a molar concentration of 0.01M to 0.05M.

[0039] In some embodiments, the asphalt and alkali solution are mixed by at least one of mechanical stirring and ultrasonic dispersion. When mechanical stirring is used, a propeller stirrer, a turbine stirrer, a flat-blade stirrer, or the like can be used, as long as the components of the materials are thoroughly mixed.

[0040] In some embodiments, the ratio of asphalt to alkali solution is 50 g / 100 ml to 100 g / 100 ml, specifically 50 g / 100 ml, 60 g / 100 ml, 70 g / 100 ml, 80 g / 100 ml, 90 g / 100 ml, or 100 g / 100 ml, etc., but is not limited to the values ​​listed above, and other values ​​not listed within this range are also applicable. Controlling the amount of alkali solution added in the present application within the above range facilitates the controlled etching of a specific ratio of pores within the asphalt by the alkali solution.

[0041] In some embodiments, the alkaline solution includes at least one of a potassium hydroxide solution and a sodium hydroxide solution.

[0042] In some embodiments, the molar concentration of the alkali solution is 0.01M to 0.05M, specifically 0.01M, 0.02M, 0.03M, 0.04M, or 0.05M, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable. If the molar concentration of the alkali solution is less than 0.01M, effective etching cannot be performed and a pore structure with a suitable pore size cannot be formed; if the molar concentration of the alkali solution is greater than 0.05M, the pore size of the formed pore structure is too large and the number of pores is too large, resulting in an increase in the specific surface area of ​​the material, which in turn leads to a deterioration in the initial efficiency and cycle performance of the negative electrode material.

[0043] In some embodiments, the ultrasonic treatment time is 6 hours to 12 hours. Specifically, the ultrasonic treatment time can be 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours or 12 hours, etc., but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0044] In some embodiments, the temperature of the ultrasonic treatment is 60°C to 80°C. Specifically, the temperature of the ultrasonic treatment can be 60°C, 65°C, 70°C, 75°C, or 80°C, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable. If the temperature of the ultrasonic treatment is less than 60°C, the etching effect is insufficient and a rich pore structure cannot be formed. If the temperature of the ultrasonic treatment is greater than 80°C, the etching intensity may be too high, which may easily cause the formed pore structure to collapse and fail to form effective pores.

[0045] In some embodiments, after step S10, the process further includes: cooling the ultrasonically treated material to room temperature, and repeatedly washing and filtering until the filtrate is neutral to remove excess alkali solution, and then removing the solvent by suction filtration, drying, and then shaping.

[0046] In some embodiments, the median particle size of the first precursor after shaping treatment is 12μm to 20μm, specifically 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm or 20μm, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0047] In some embodiments, the shaping process includes at least one of pulverizing, spheroidizing, and classifying.

[0048] S20 , carbonizing the first precursor obtained in step S10 to obtain a second precursor.

[0049] In some embodiments, the reaction temperature of the carbonization treatment is 500°C to 1200°C, specifically 500°C, 600°C, 700°C, 750°C, 800°C, 850°C, 900°C, 1000°C, 1100°C, or 1200°C, etc., but is not limited to the values ​​listed above, and other values ​​not listed within this range are also applicable. It can be understood that the carbonization treatment temperature within the above range is conducive to the controllable and uniform decomposition and release of impurities, volatiles, and unstable substances within the material, forming a regular pore structure.

[0050] In some embodiments, the holding time of the carbonization treatment is 8 hours to 12 hours, specifically 8 hours, 9 hours, 10 hours, 11 hours or 12 hours, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0051] In some embodiments, the heating rate of the carbonization treatment is 2°C / min to 10°C / min, specifically 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min or 10°C / min, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0052] In some embodiments, the cooling rate after carbonization treatment is 1°C / min to 5°C / min, specifically 1°C / min, 2°C / min, 3°C / min, 4°C / min or 5°C / min, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0053] In some embodiments, the carbonization process is performed under a protective atmosphere comprising at least one of nitrogen, helium, neon, argon, krypton, and xenon.

[0054] S30, graphitizing the second precursor to obtain a negative electrode material.

[0055] In some embodiments, the temperature of the graphitization treatment is 2800°C to 3200°C, specifically 2800°C, 2850°C, 2900°C, 2950°C, 3000°C, 3050°C, 3100°C, 3150°C or 3200°C, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0056] In some embodiments, the holding time of the graphitization treatment is 6 hours to 12 hours, specifically 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours or 12 hours, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0057] In some embodiments, the graphitization treatment includes: first heating the temperature to 1600°C to 1800°C at a heating rate of 0.2°C / min to 1°C / min, then heating the temperature to 3000°C to 3200°C at a heating rate of 2°C / min to 8°C / min, holding the temperature for 6 to 20 hours, and finally cooling the temperature to room temperature. This application adopts a two-stage heating treatment method for graphitization, which is conducive to forming a graphite material with a stable pore structure and improving the degree of graphitization of the graphite material.

[0058] In some embodiments, the heating rate of the first stage of the graphitization treatment is 0.2°C / min to 1°C / min, specifically 0.2°C / min, 0.3°C / min, 0.4°C / min, 0.5°C / min, 0.6°C / min, 0.7°C / min, 0.8°C / min, 0.9°C / min or 1°C / min, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0059] In some embodiments, the heating rate of the second heating stage of the graphitization treatment is 2°C / min to 8°C / min, specifically 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, or 8°C / min, etc., but is not limited to the listed values. Other values ​​not listed within this numerical range are also applicable. In the present application, the heating rate of the first heating stage of the graphitization treatment is less than the heating rate of the second heating stage of the graphitization treatment, which can ensure the formation of a pore structure of appropriate size and morphology, which is conducive to the infiltration of the electrolyte.

[0060] Those skilled in the art will understand that the above-described method for preparing the battery is merely an example, and other methods commonly used in the art may be used without departing from the disclosure of this application.

[0061] The present application provides a negative electrode material, the negative electrode material includes artificial graphite, the artificial graphite has pores, and the average pore diameter P of the pores is The oil absorption value O (mL / 100g) and pore volume V (cm 3 / kg), tap density T (g / mL), and powder conductivity e (S / cm) of the negative electrode material under a pressure of 20KN meet the following requirements: 9≤0*V*P / (T*e)≤55;

[0062] The pore volume and average pore size of the negative electrode material were tested using the ASAP2460 equipment from Micromeritics, Inc. of the United States. The BJH Desorption cumulative volume of pores model was used to calculate the average pore size of the negative electrode material. The pore volume of the negative electrode material was calculated within the pore size range, and the average pore size was calculated using the BJH Desorption model.

[0063] In the above scheme, the negative electrode material provided by this application is formed by in-situ etching of a mixture of asphalt saturated fraction and asphalt aromatic fraction with 0.01M~0.05M alkali solution to form pores on the material, and is produced and processed through carbonization and graphitization processes to achieve precise control of the pores inside and / or on the surface of the graphite, so that the pore size, pore volume, oil absorption value, tap density and powder conductivity of the material pores meet the ideal control design requirements. The effective pores with uniform distribution are formed inside and / or on the surface of the graphite, which can effectively infiltrate the electrolyte while maintaining a high tap density and powder conductivity, providing more lithium ion deintercalation channels and increasing the effective reaction area on the surface of the graphite negative electrode material, ultimately achieving the purpose of improving the high-rate charge and discharge performance and safety performance of graphite.

[0064] Generally speaking, the pore volume within a certain range in artificial graphite can increase the diffusion channel of Li ions, promote the diffusion of lithium ions at the solid-liquid interface and in the solid phase, reduce concentration polarization, and help improve the capacity and rate performance of the negative electrode material. Based on this, the applicant found through in-depth research that there is only enough lithium ion diffusion channel and electrochemical reaction area, and the rate performance still has a lot of room for improvement. The reason is that because lithium ion deintercalation requires not only diffusion channels and reaction interfaces, but also electrolyte as a medium, some pores cannot be wetted by the electrolyte due to the influence of surface morphology or other factors, and thus cannot play their role. Naturally, the corresponding surface cannot undergo electrochemical reaction, resulting in insufficient effective electrochemical reaction space; at the same time, the improvement of battery performance is not only affected by the transmission of lithium ions, but also by the transmission of electrons. On the one hand, lithium ion deintercalation requires diffusion channels and reaction interfaces, and the negative electrode material is fully wetted by the electrolyte as a medium, thereby improving the transmission rate of lithium ions. However, in fact, some pores cannot be wetted by the electrolyte and cannot play their role. The influence of the pore size and surface morphology that cannot play a role may hinder electron transmission, increase resistance and reduce battery rate performance. On the other hand, the lithium ion deintercalation and intercalation of the negative electrode material during use requires further charge transfer at the interface. In addition, if the negative electrode material has excellent conductivity during the electrode preparation process, the amount of conductive agent used in the electrode can be reduced, thereby increasing the battery capacity while improving the rate performance. Therefore, the material is also required to have good conductivity. Only by balancing the pore structure and surface morphology of the negative electrode material particles and taking into account both ion transport and electron transport can the high rate performance and high capacity of the battery be further exerted. In addition, in addition to the impact on rate performance, excessive pore structure will also lead to a decrease in the tap density of graphite as a negative electrode material, resulting in poor processing performance during the preparation of slurry and electrodes, and ultimately causing poor battery cycle performance. Therefore, the present application, by synergizing the effects of pore size, pore volume, tap density, oil absorption value and powder conductivity, constructs the relationship: 9≤O*V*P / (T*e)≤55, so that the graphite artificial graphite material forms a rich and regular pore structure, so that the negative electrode material can have good rate performance and good processing performance.

[0065] In the present application, the value range of O*V*P / (T*e) is 9 to 55, specifically, it can be 9, 12, 15, 20, 25, 34, 38, 40, 43, 46, 48, 52 or 55, etc. Of course, it can also be other values ​​within the above range, and this application does not limit it here. Specifically, V represents the pore volume of the graphite material, and P represents the average pore size of the pores on the graphite material. The larger the average pore size P and pore volume V of the pores on the artificial graphite material, the richer the pore structure of the artificial graphite particles, which can create more lithium ion diffusion channels and effective reaction areas for the graphite material, which is beneficial to improving the rate performance of the graphite negative electrode material. However, when the pores become more, on the one hand, the pores provide transmission channels for lithium ions to improve the rate performance, but on the other hand, the electron mobility is related to the lattice structure of the material. The better the crystal quality and the more complete the lattice, the more regular the internal ion arrangement, and the higher the electron mobility will generally be. The atomic arrangement around the pores of graphite is relatively irregular, which easily forms defect traps, reduces the transmission rate of electrons in the particles, and may have a counter-effect on the rate improvement to a certain extent. Therefore, the distribution and number of pore structures are closely related. The amount or size may lead to an increase in side reactions, a decrease in tap density, and an impact on conductivity, resulting in poor processing performance and cycle performance of the negative electrode material; at the same time, the presence of the pore structure changes the surface state of the graphite negative electrode material, the roughness of the particle surface increases, and there are relatively more tiny protrusions on the rough particle surface. There are microscopic gaps between particles, which reduces the contact area between particles, increases the interface resistance, and reduces the conductivity. Not only that, the particles will also reduce the tap density of the negative electrode material due to the voids and pores inside the particles due to the rough surface. Among them, the greater the oil absorption value, the better the adsorption and wetting performance of the graphite negative electrode surface for the electrolyte; in addition, the powder conductivity will also vary due to differences in graphite production process and pore structure, which will have a certain impact on the electrochemical activity of the graphite material. Therefore, the applicant found through a large number of experimental studies that the average pore size, pore volume, oil absorption value, tap density and powder conductivity of the artificial graphite material are controlled at 9≤O*V*P /

[0066] (T*e)≤55, which makes the negative electrode material have good electrolyte wettability and conductivity, and also has appropriate compaction and tap density, which can ensure the processing performance of the artificial graphite negative electrode material while maximizing the rate performance and cycle performance, thereby improving the comprehensive electrochemical performance of the artificial graphite negative electrode material.

[0067] In some embodiments, the pores are distributed in the interior and / or on the surface of the artificial graphite.

[0068] In some embodiments, the pores include at least one of micropores and mesopores.

[0069] In some embodiments, the average pore size P of the pores is Specifically it can be or When the pore size is within this range, it is conducive to sufficient electrolyte infiltration without affecting the material density, and has a beneficial effect on improving the rate performance and processing performance of the graphite negative electrode material.

[0070] In some embodiments, the pore volume of the negative electrode material is 2 cm 3 / kg~4cm 3 / kg, specifically, the pore volume of the negative electrode material is 2cm 3 / kg, 2.5cm 3 / kg、3cm 3 / kg、3.5cm 3 / kg or 4cm 3 / kg, etc., and of course, other values ​​within the above range can also be used, and this application does not limit them here. Within the above range, it shows that the pore volume of the negative electrode material of this application is large, so that when the graphite is used as the negative electrode material, there are more effective active sites on the surface when the lithium is inserted and removed, which is beneficial to improving the electrochemical performance of the graphite negative electrode material. If the pore volume of the negative electrode material is less than 2cm 3 / kg, which results in a decrease in the diffusion efficiency of lithium ions and a deterioration in rate performance. If the pore volume of the negative electrode material is greater than 4cm 3 / kg, which causes the graphite negative electrode material to form a larger amount of solid electrolyte membrane (SEI membrane) during the first lithium insertion process, resulting in a capacity loss angle of the negative electrode material during the first charge and discharge process. Moreover, more binder will be required in the subsequent slurrying process, resulting in an increase in internal resistance. Therefore, the first efficiency of the negative electrode material is reduced and the cycle performance is deteriorated.

[0071] In some embodiments, the oil absorption value O of the negative electrode material is 24 mL / 100 g to 49 mL / 100 g, and specifically can be 24 mL / 100 g, 28 mL / 100 g, 32 mL / 100 g, 38 mL / 100 g, 45 mL / 100 g, or 49 mL / 100 g, etc. Of course, it can also be other values ​​within the above range, and this application is not limited thereto. Within the above-defined range, it is shown that the oil absorption value of the negative electrode material of the present application is large, indicating that the graphite negative electrode surface has good adsorption and wettability for the electrolyte, thereby increasing the effective reaction area on the surface of the graphite negative electrode material, thereby achieving the purpose of improving the high-rate charge and discharge performance of the graphite.

[0072] In some embodiments, the tap density of the negative electrode material is 1.00 g / mL to 1.50 g / mL, specifically 1.00 g / mL, 1.10 g / mL, 1.20 g / mL, 1.30 g / mL, 1.40 g / mL or 1.50 g / mL, etc., and of course it can also be other values ​​within the above range. This application is not limited here. Within the above-mentioned limited range, it shows that the mass of active material per unit volume of the negative electrode material of the present application is large, which is beneficial to improving the capacity performance and cycle performance of the material, thereby improving the processing performance.

[0073] In some embodiments, the powder conductivity of the negative electrode material under a pressure of 20 kN is 350 S / cm to 430 S / cm, specifically 350 S / cm, 360 S / cm, 370 S / cm, 380 S / cm, 390 S / cm, 400 S / cm, 410 S / cm, 420 S / cm or 430 S / cm, etc., and of course it can also be other values ​​within the above range, which is not limited in this application. Within the above-defined range, it is shown that the powder conductivity of the negative electrode material of the present application is large, which is conducive to the rapid migration of electrons between particles and within particles. At the same time, it is also conducive to charge transfer at the solid-liquid interface of the negative electrode material during use, thereby improving the conductive properties of the negative electrode material and thereby improving the rate performance of the negative electrode material.

[0074] In some embodiments, the true density of the negative electrode material is 2.230 g / cm 3 ~2.260g / cm 3 , specifically 2.230g / cm 3 , 2.235g / cm 3 , 2.240g / cm 3 , 2.245g / cm 3 , 2.250g / cm 3 , 2.255g / cm 3 or 2.260g / cm 3 Of course, it can also be other values ​​within the above range, which is not limited in this application. Within the above-defined range, it shows that the artificial graphite has a good degree of order and can provide a good way for the electrochemical insertion and deinsertion of lithium ions.

[0075] In some embodiments, the median particle size of the negative electrode material is 12 μm to 20 μm, specifically, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm or 20 μm, etc. Of course, it can also be other values ​​within the above range, which is not limited in this application.

[0076] In some embodiments, the negative electrode material is measured by X-ray diffraction, and the interlayer spacing of the (002) plane is d002 , Specifically, it can be 3.360, 3.361, 3.362, 3.363 or 3.364, etc. Of course, it can also be other values ​​within the above range, which is not limited in this application. 002 Within the above range, it can be seen that the graphite crystallinity of the artificial graphite particles is high, that is, the degree of graphitization is high, and the capacity of the product is high.

[0077] In some embodiments, the peak intensity ratio of the (004) plane to the (110) plane of the negative electrode material is measured by X-ray diffraction. 004 / I 110 3 to 5, I 004 / I 110 Specifically, it can be 3, 3.3, 4, 4.2, 4, 8 or 5, etc. Of course, it can also be other values ​​within the above range, and this application does not limit it. 004 / I 110 Controlling within the above range indicates that the negative electrode material of the present application has a better orientation degree.

[0078] In some embodiments, the artificial graphite includes artificial graphite primary particles and / or artificial graphite secondary particles, with the artificial graphite primary particles being the main component.

[0079] An embodiment of the present application also provides a battery comprising the above-mentioned negative electrode material.

[0080] Those skilled in the art will appreciate that the battery preparation method described above is merely an example. Without departing from the disclosure of this application, other methods commonly used in the art may be employed, and other types of batteries may be prepared for testing, such as sodium-ion batteries, potassium-ion batteries, and the like.

[0081] The following further illustrates the embodiments of the present application in multiple embodiments. The embodiments of the present application are not limited to the following specific embodiments. Within the scope of the unchanged main rights, appropriate changes can be made to the implementation.

[0082] Example 1

[0083] (1) The aromatic fraction and saturated fraction of asphalt were mixed in a mass ratio of 40:60, heated to 80°C to soften, and then mixed with 0.05M KOH solution. The mixture was kept at 80°C and ultrasonically treated for 12 h.

[0084] (2) Cooling the mixture obtained in step (1) to room temperature, repeatedly washing and filtering with distilled water until the filtrate is neutral, removing the solvent by suction filtration, and then placing it in a vacuum oven to dry for 10 hours;

[0085] (3) crushing the material obtained in step (2), wherein the median particle size of the crushed material is 16 μm;

[0086] (4) carbonizing the mixture obtained in step (3) at 1200° C.;

[0087] (5) The sample carbonized in step (4) is subjected to high-temperature graphitization at 3200° C. to obtain a graphite negative electrode material.

[0088] The negative electrode material comprises primary artificial graphite particles and secondary artificial graphite particles, with primary artificial graphite particles being the main component.

[0089] Example 2

[0090] The difference from Example 1 is that the temperature of the ultrasonic treatment in step (1) is 60° C. and the time of the ultrasonic treatment is 10 h.

[0091] The negative electrode material comprises primary artificial graphite particles and secondary artificial graphite particles, with primary artificial graphite particles being the main component.

[0092] Example 3

[0093] The difference from Example 1 is that the temperature of ultrasonic treatment in step (1) is 70° C. and the time of ultrasonic treatment is 10 h.

[0094] The negative electrode material comprises primary artificial graphite particles and secondary artificial graphite particles, with primary artificial graphite particles being the main component.

[0095] Example 4

[0096] The difference from Example 1 is that in step (1), the mass ratio of asphalt saturated fraction to asphalt aromatic fraction is 50:50.

[0097] The negative electrode material comprises primary artificial graphite particles and secondary artificial graphite particles, with primary artificial graphite particles being the main component.

[0098] Example 5

[0099] The difference from Example 1 is that in step (1), the mass ratio of asphalt saturated fraction to asphalt aromatic fraction is 60:40.

[0100] The negative electrode material comprises primary artificial graphite particles and secondary artificial graphite particles, with primary artificial graphite particles being the main component.

[0101] Example 6

[0102] The difference from Example 1 is that the concentration of the alkaline solution added in step (1) is 0.04M KOH.

[0103] The negative electrode material comprises primary artificial graphite particles and secondary artificial graphite particles, with primary artificial graphite particles being the main component.

[0104] Example 7

[0105] The difference from Example 1 is that the concentration of the alkaline solution added in step (1) is 0.03M KOH.

[0106] The negative electrode material comprises primary artificial graphite particles and secondary artificial graphite particles, with primary artificial graphite particles being the main component.

[0107] Example 8

[0108] The difference from Example 1 is that the concentration of the alkaline solution added in step (1) is 0.02M KOH.

[0109] The negative electrode material comprises primary artificial graphite particles and secondary artificial graphite particles, with primary artificial graphite particles being the main component.

[0110] Example 9

[0111] The difference from Example 1 is that the concentration of the alkaline solution added in step (1) is 0.01 M KOH.

[0112] The negative electrode material comprises primary artificial graphite particles and secondary artificial graphite particles, with primary artificial graphite particles being the main component.

[0113] Example 10

[0114] Different from Example 1, the carbonization temperature in step (3) is 500°C.

[0115] The negative electrode material comprises primary artificial graphite particles and secondary artificial graphite particles, with primary artificial graphite particles being the main component.

[0116] Example 11

[0117] Different from Example 1, the carbonization temperature in step (4) is 1000°C.

[0118] The negative electrode material comprises primary artificial graphite particles and secondary artificial graphite particles, with primary artificial graphite particles being the main component.

[0119] Example 12

[0120] Different from Example 1, the graphitization temperature in step (5) is 2800°C.

[0121] The negative electrode material comprises primary artificial graphite particles and secondary artificial graphite particles, with primary artificial graphite particles being the main component.

[0122] Example 13

[0123] Different from Example 1, the graphitization temperature in step (5) is 3000°C.

[0124] The negative electrode material comprises primary artificial graphite particles and secondary artificial graphite particles, with primary artificial graphite particles being the main component.

[0125] Comparative Example 1

[0126] (1) Mixing the asphalt aromatic fraction and the asphalt saturated fraction in a mass ratio of 40:60 and heating to 80°C to soften;

[0127] (2) carbonizing the material obtained in step (1) at 1200° C.;

[0128] (3) The sample carbonized in step (2) is subjected to high-temperature graphitization at 3200° C. to obtain a graphite negative electrode material.

[0129] Comparative Example 2

[0130] The difference from Example 1 is that in step (1), the mixture is softened at 80°C and then mixed with 0.1M KOH solution, and ultrasonic treatment is performed at 80°C for 20 hours.

[0131] Comparative Example 3

[0132] Different from Example 1, the temperature of ultrasonic treatment in step (1) is room temperature (25° C.).

[0133] Performance Testing

[0134] (1) Test method for median particle size of negative electrode materials:

[0135] The particle size distribution range of the negative electrode material was tested by Malvern laser particle size analyzer.

[0136] (2) Testing method for pore volume and average pore diameter of negative electrode materials:

[0137] The test was carried out using the ASAP2460 equipment of American Micromeritics. The pore volume V and average pore diameter P were calculated using the BJHDesorption cumulative volume of pores model. The pore size range is calculated, where the BJH Desorption cumulative volume of pores model is used. The pore volume of the negative electrode material was calculated within the pore size range, and the average pore size was calculated using the BJH Desorption model.

[0138] (3) Testing method of oil absorption value of negative electrode material:

[0139] The oil absorption value O is the amount of linseed oil added when the torque generated by the change in viscosity reaches 70% of the maximum torque, and the unit is mL / 100g.

[0140] (4) Test method for the tap density of negative electrode materials:

[0141] The tap density T was measured using a Quantachrome Dual Autotap tap density analyzer from Anton Paar (Shanghai) Trading Co., Ltd. The tap density T is the value after 222 vibrations and is expressed in g / mL.

[0142] (5) Test method for the powder conductivity of negative electrode materials:

[0143] The powder conductivity e was tested using a Mettler-Toledo S230 conductivity meter. The powder conductivity e was the value measured under a pressure of 20 kN, and the unit was S / cm.

[0144] (6) The surface morphology of the negative electrode material was observed using a Hitachi S4800 scanning electron microscope.

[0145] (7) True density D is measured using Anton Paconta's PENTAPYC 5200e true density meter. The Archimedean principle of gas displacement (density = mass / volume) and Bohr's law (PV = nRT) of inert gases with small molecular diameters under certain conditions are used to accurately measure the true volume of the material being tested, thereby obtaining its true specific gravity in g / cm 3 .

[0146] (8) Battery performance test method: The samples prepared in Examples 1 to 13 and Comparative Examples 1 to 3 were mixed in an N-methylpyrrolidone solution (NMP, AR) with a mass ratio of conductive adhesive (CMC+SP): SBR = 95:1.5:1.5:2 under magnetic stirring for 8 hours to mix them evenly. The mixed slurry was coated on a copper foil and dried in a vacuum at 60°C as a working electrode. Metallic lithium was used as the counter electrode and reference electrode, the diaphragm was Celgard2325, and the electrolyte was 1 mol·L-1LiPF6-EC (ethylene carbonate) / DMC (dimethyl carbonate) / EMC (ethyl methyl carbonate) (volume ratio of 1:1:1). CR2016 button cell batteries were assembled in a glove box filled with high-purity argon. Four batteries were prepared for each sample group.

[0147] The first discharge capacity / first discharge efficiency test was conducted on a LAND battery tester with the following charge and discharge conditions: 2 h rest; discharge: 0.1C to 0.005V, 0.09C, 0.08C…0.02C to 0.001V; 15 min rest; charge: 0.1C to 1.5V; 15 min rest. The test conditions for the charge rate are as follows: 0.1C discharge to 0.01V, constant voltage for 5h; 0.1C charge to 1.5V; ②0.2C discharge to 0.01V, constant voltage 0.01C; 0.2C charge to 1.5V; ③0.2C discharge to 0.01V, constant voltage 0.01C; 2C charge to 1.5V, 0.2C charge to 1.5V; ④0.2C discharge to 0.01V, constant voltage 0.01C; 0.2C charge to 1.5V; ⑤1C discharge to 0.01V, constant voltage 0.01C; 0.2C charge to 1.5V; ⑥2C discharge to 0.01V.

[0148] The tableting liquid absorption test conditions were as follows: the powder sample was prepared into a slurry using a JS-24FS powder tablet press, dried, ground, and sieved, and then pressed into tablets using a pressure of 4400 pounds. After rebounding for 8 hours, the tablets were tested for liquid absorption time. The test results are shown in Tables 1 and 2.

[0149] Table 1. Parameter test results of negative electrode materials of various embodiments and comparative examples

[0150]

[0151]

[0152] Table 2. Performance parameter test of negative electrode materials of various embodiments and comparative examples

[0153]

[0154] As shown in Tables 1 and 2, the negative electrode material provided by the present application is formed by in-situ etching of a mixture of asphalt saturated fraction and asphalt aromatic fraction with 0.01M~0.05M alkali solution to form a pore structure on the surface and / or inside of the material, and is produced and processed through carbonization and graphitization processes to achieve precise control of the internal and / or surface pores of the graphite, the internal contact conditions of the graphite negative electrode material, and the distribution of the pores, so that the pore size, pore volume, oil absorption value, tap density and powder conductivity of the material pores meet the ideal control design requirements, so that when the negative electrode material of the present application is made into an electrode and used in a battery, the rate performance and cycle performance of the graphite negative electrode material can be maximized while ensuring the processing performance.

[0155] In Comparative Example 1, low concentration of alkali solution was not added, resulting in insufficient pore structure of the prepared negative electrode material, making the pore volume and average pore diameter of the negative electrode material smaller, while the tap density was larger, resulting in O*V*P / (T*e) not meeting the limited range of 9 to 55, resulting in Li +The diffusion channels inside the graphite material are limited, which increases the Li + The diffusion resistance will limit the rate performance of the material.

[0156] In Comparative Example 2, the concentration of the alkaline solution added is greater than the specified range of the present application, and the heat treatment time is increased. Although the pore structure obtained by etching is richer, it also leads to more side reactions of the negative electrode material finally obtained, and the initial efficiency is reduced.

[0157] In Comparative Example 3, the ultrasonic treatment was carried out at room temperature, resulting in insufficient etching intensity, which resulted in insufficient pore structure, making the pore volume and average pore diameter of the negative electrode material smaller, while the tap density was larger, resulting in O*V*P / (T*e) not meeting the limited range of 9 to 55, resulting in Li + The diffusion channels inside the graphite material are limited, which increases the Li + The diffusion resistance will limit the rate performance of the material.

[0158] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A negative electrode material, characterized in that The negative electrode material includes artificial graphite, the artificial graphite has pores, the average pore diameter of the pores is P, the unit is Å, the oil absorption value of the negative electrode material is O, the unit is mL / 100g, and the pore volume is V, the unit is cm 3 / kg, the tap density is T, the unit is g / mL, and the powder conductivity of the negative electrode material under a pressure of 20KN is e, the unit is S / cm, and the negative electrode material satisfies: , 1.121≤T≤1.5, 1.967≤V≤3.345, 75≤P≤125, 300≤e≤450; the true density of the negative electrode material is 2.2403 g / cm 3 ~2.260 g / cm 3 ; The pore volume and the average pore diameter of the pores are measured using an ASAP2460 device from Micromeritics, USA. The pore volume of the negative electrode material is calculated using the BJH Desorption cumulative volume of pores model within a pore diameter range of 17 Å to 3000 Å, and the average pore diameter of the pores is calculated using the BJH Desorption model. The tap density T was measured using a Quantachrome Dual Autotap tap density analyzer from Anton Paar Shanghai Trading Co., Ltd. The tap density T was the value after 222 vibrations. The powder conductivity e was tested using a Mettler-Toledo S230 conductivity meter, and the powder conductivity e was the value measured under a pressure of 20 kN.

2. The negative electrode material according to claim 1, characterized in that The negative electrode material includes at least one of the following characteristics (1) to (2): (1) The pores are distributed inside and / or on the surface of the artificial graphite; (2) The oil absorption value of the negative electrode material is 24 mL / 100 g to 49 mL / 100 g.

3. The negative electrode material according to claim 1, characterized in that The median particle size D50 of the negative electrode material is 12 μm to 20 μm.

4. The negative electrode material according to claim 1, characterized in that The negative electrode material is measured by X-ray diffraction, and the interlayer spacing of the 002 surface of the negative electrode material is d 002 , 3.360Å≤d 002 ≤3.364Å.

5. The negative electrode material according to claim 1, characterized in that The negative electrode material is measured by X-ray diffraction, and the peak intensity ratio of the 004 face to the 110 face of the negative electrode material is I 004 / I 110 3~5.

6. The negative electrode material according to claim 1, characterized in that The negative electrode material includes artificial graphite primary particles and / or artificial graphite secondary particles.

7. The negative electrode material according to claim 1, characterized in that The pores include at least one of micropores and mesopores.

8. A battery, characterized in that: The battery comprises the negative electrode material according to any one of claims 1 to 7.

Images