CN116986580B - Carbon material and preparation method thereof, negative electrode plate, secondary battery and power utilization device - Google Patents

Carbon material and preparation method thereof, negative electrode plate, secondary battery and power utilization device Download PDF

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CN116986580B
CN116986580B CN202311242153.2A CN202311242153A CN116986580B CN 116986580 B CN116986580 B CN 116986580B CN 202311242153 A CN202311242153 A CN 202311242153A CN 116986580 B CN116986580 B CN 116986580B
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carbon material
heating
carbon
negative electrode
secondary battery
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CN116986580A (en
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吴凯
许逸达
张欣欣
陈晓霞
刘犇
马宇
刘士坤
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Contemporary Amperex Technology Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes

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  • Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Carbon And Carbon Compounds (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

The application relates to a carbon material and a preparation method thereof, a negative electrode plate, a secondary battery and an electric device, wherein the carbon material has a pore canal structure; the carbon material has an exhaust gas amount A with respect to water and an exhaust gas amount B with respect to methanol, which are obtained by a liquid probe measurement method; and 0 < A/B is less than or equal to 6. The microscopic pore canal structure of the carbon material is favorable for intercalation and deintercalation of sodium ions, so that the secondary battery using the carbon material has excellent rate capability.

Description

Carbon material and preparation method thereof, negative electrode plate, secondary battery and power utilization device
Technical Field
The application relates to the technical field of secondary batteries, in particular to a carbon material and a preparation method thereof, a negative electrode plate, a secondary battery and an electric device.
Background
Secondary batteries represented by lithium ion batteries have been widely used at present. Similar to lithium ion batteries, sodium ion batteries rely on sodium ions to back and forth release and intercalation between positive and negative electrode materials to achieve charge and discharge processes. And the sodium resource reserves are abundant and widely distributed, so that the sodium ion battery becomes a new generation electrochemical system with great development potential.
The cathode material is one of the key factors restricting the performance of the sodium ion battery at present. Sodium ion anode materials currently exist with a larger atomic radius of sodium ions than lithium ions, for example, the intercalation and storage of sodium ions are easily limited by the smaller spacing of graphite layers by adopting the traditional graphite anode materials. There is therefore a need to develop a negative electrode material more suitable for sodium ion batteries. However, the negative electrode material in the prior art has the defects of poor cycle performance, insufficient capacity retention rate and the like.
Disclosure of Invention
The present application is directed to a carbon material having a micro-porous structure and being suitable for sodium ion deintercalation by being characterized with respect to the displacement of a probe liquid, thereby improving the performance of a secondary battery, a method for manufacturing the same, a negative electrode tab, a secondary battery, and an electric device.
To this end, the present application provides a carbon material having a pore structure;
the carbon material is obtained by a liquid probe measurement method, and the exhaust gas amount of the carbon material relative to water is A, and the exhaust gas amount relative to methanol is B; and 0 < A/B is less than or equal to 6.
Sodium ions are intercalated, deintercalated and stored in the negative electrode, and related dynamics are related to the microscopic pore channel structure of the carbon material. The amount of gas that can be exchanged out of the water characterizes the total volume of the channels that sodium ions can go in and out of. The kinetic diameter of methanol is larger than that of water, and if the methanol cannot enter the pore canal which can be detected by the water, the pore canal is narrow, so that the rapid transmission of sodium ions is not facilitated; if it is accessible to both water and methanol, it is indicated that it is suitable for rapid transport of sodium ions. Therefore, if a considerable part of the gas which can be exchanged by water in the carbon material can also be exchanged by methanol, namely, the condition that the A/B is less than or equal to 6 is satisfied, the whole pore structure of the carbon material is suitable for embedding and extracting sodium ions, thereby being beneficial to improving the multiplying power performance of the secondary battery.
In any embodiment, the value of A/B is 5 or less. In any embodiment, the value of A/B is 4 or less. In any embodiment, the value of A/B is 3 or less. In any embodiment, the value of A/B is 2 or less. In any embodiment, the value of A/B is 1 or less.
In any embodiment, the carbon material has an exhaust gas amount C relative to a mixed solution of ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1 obtained by a liquid probe measurement method; and B/C is more than or equal to 5.
The volume of the gas which can be discharged by the mixed solution of the ethylene carbonate and the dimethyl carbonate according to the volume ratio of 1:1 is approximate to the volume of a pore channel which can be entered by the electrolyte. B/C is more than or equal to 5, which indicates that most of the gas which can be exchanged by methanol in the carbon material cannot be exchanged by the mixed solution consisting of ethylene carbonate and dimethyl carbonate, and the pore structure can be used as a sodium storage site in the carbon material and can not be filled by electrolyte to become an external volume which does not contribute to capacity.
In any embodiment, B is greater than or equal to 0.05 mL/g.
When the exhaust amount of the carbon material relative to methanol is more than or equal to 0.05 mL/g, the carbon material has a relatively rich overall pore structure suitable for sodium ion intercalation, deintercalation and storage, and can show better rate capability when used for a battery cathode.
In any embodiment, in the X-ray diffraction spectrum of the carbon material, the 002 peak corresponds to a 2 theta value between 22 ° and 24 °; in the Raman spectrum of the carbon material, id/Ig is 1.0-1.4, wherein Id represents that the Raman shift is 1350+/-50 cm -1 D peak intensity in the range, ig represents Raman shift of 1580+ -50 cm -1 G peak intensity in the range.
When the 2 theta value of the X-ray diffraction spectrum of the carbon material meets the above conditions, the carbon material is shown to have moderate amorphous degree, and the structural requirement of the carbon material serving as a sodium storage material is more easily met. The Id/Ig value in the Raman spectrum of the carbon material can reflect the disorder degree of the carbon material, and when the disorder degree is higher, sodium storage sites of the carbon material can be more, but the first effect can be lower; conversely, decreasing order may increase first effect, but may result in decreased gram capacity. When the Id/Ig value meets the above conditions, the carbon material has moderate order degree, proper sodium storage gram capacity and first effect, and good multiplying power performance.
In any embodiment, the volume particle diameter Dv50 of the carbon material is 3 μm to 7 μm.
In any embodiment, the volume particle diameter Dv90 of the carbon material is 9 μm to 18 μm.
When the volume particle diameters Dv50 and Dv90 of the carbon material are respectively in the above ranges, the construction of smooth ion and electron transmission channels at the pole piece level is facilitated, and the rate capability of the secondary battery is improved.
In any embodiment, the carbon material has a specific surface area of 0.1 m 2 /g~50 m 2 /g。
When the specific surface area of the carbon material is low, active ions consumed in SEI film formation are reduced, so that the first effect is improved; on the other hand, the higher specific surface area of the carbon material can be beneficial to the transmission of active ions. Therefore, when the specific surface area of the carbon material is within the above range, the above advantages can be combined, thereby obtaining a good gram capacity and initial efficiency, while having good rate performance.
In a second aspect of the present application, there is provided a method for preparing a carbon material according to the first aspect of the present application, including: preheating a carbon precursor to obtain an intermediate; carbonizing the intermediate to prepare the carbon material.
By subjecting the carbon precursor to the above treatment, the formation of the pore structure of the carbon material can be controlled by the pretreatment and carbonization treatment, thereby preparing the carbon material according to the first aspect of the present application.
In any embodiment, the carbonization treatment comprises: sequentially performing first heating and second heating on the intermediate; the first heating includes: heating to T2, and then carrying out first heat preservation, wherein the temperature of T2 is 300-800 ℃; the second heating includes: and (3) heating to T3, and then carrying out second heat preservation, wherein T3 is 1000-1700 ℃.
The intermediate is carbonized by the staged heating method, so that pyrolysis, carbonization and local graphitization can be realized step by step, and a regular pore structure is easy to form at the local graphitization position.
In any embodiment, the heating rate of the first heating step is less than or equal to 1 ℃/min.
In the first heating process, the heating rate not exceeding 1 ℃/min is adopted, so that a through pore canal structure is formed in the heating process, a channel for gas to quickly escape is generated, and collapse of the pore canal structure due to impact of a large amount of gas generated by heating is avoided.
In any embodiment, the first heat preservation time is t2, and t2 is 1-50 h.
Under certain temperature conditions, the heat preservation time can influence the graphitization degree of the material. When the heat preservation time is adopted, the local graphitization degree is improved, and a regular pore structure is easy to form. Overall, a slightly longer hold time helps to increase the a/B value and a slightly shorter hold time helps to decrease the a/B value, e.g., a hold time that is too short, e.g., shorter than 1 h, may result in insufficient carbonization, resulting in an undesirable pore structure that negatively affects the sodium storage process.
In any embodiment, the preheating treatment includes: heating to T1; t1 is 200-700 ℃.
The carbon precursor can be carbonized at a low temperature through the preheating treatment, which is favorable for the advanced forming of the carbon skeleton, so that a certain pore structure is maintained in the subsequent carbonization and activation. During the preheating treatment, the degree of crosslinking between the macromolecules increases, and the pore structure is slowly formed and cured.
In any embodiment, the preheating treatment further comprises the following steps: removing impurities; the impurity removal includes an acidic solution washing step and/or an alkaline solution washing step.
During the preheating treatment, a small amount of impurities are generated, and the impurities play an auxiliary role in occupying space. This portion of the impurities can be removed by acidic solution washing and/or alkaline solution washing, leaving behind the corresponding pores.
In any embodiment, the carbon precursor comprises at least one selected from the group consisting of: biomass materials, high molecular polymers, coal and secondary processed products thereof. In some embodiments, the biomass material comprises at least one selected from the group consisting of: wood (e.g., pine, poplar, etc.), straw, bamboo, bark, fruit shells (e.g., walnut shells, coconut shells, etc.), fruit pits (e.g., date pits), starch, sucrose, cellulose, lignin, hemicellulose, chitin, pectin, xylan, chitosan, and protein.
Any known raw material suitable for preparing hard carbon can be adopted for preparing the carbon material, and when biomass materials are selected, the biomass material has the advantages of low raw material cost, environmental protection and the like.
In a third aspect of the present application, there is provided a negative electrode tab, the negative electrode tab including the carbon material described in the first aspect of the present application or a carbon material prepared according to the preparation method described in the second aspect of the present application.
In a fourth aspect of the present application, there is provided a secondary battery including a positive electrode tab, a negative electrode tab, an electrolyte, and a separator; the negative electrode plate is the negative electrode plate in the third aspect of the application.
In any embodiment, the secondary battery is a lithium ion battery or a sodium ion battery.
In a fifth aspect of the present application, there is provided an electric device including the secondary battery according to the fourth aspect of the present application.
The foregoing description is only an overview of the technical solutions of the present application, and in order to make the technical means of the present application more clearly understood, it is possible to implement the present application in accordance with the content of the present specification, and in order to make the above and other objects, features and advantages of the present application more clearly understood, the following describes the embodiments of the present application.
Drawings
Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the application. Also, like reference numerals are used to designate like parts throughout the figures. In the drawings:
fig. 1 is a schematic view of a secondary battery according to an embodiment of the present application;
fig. 2 is an exploded view of the secondary battery according to an embodiment of the present application shown in fig. 1;
FIG. 3 is a schematic view of a battery module according to an embodiment of the present application;
FIG. 4 is a schematic view of a battery pack according to an embodiment of the present application;
FIG. 5 is an exploded view of the battery pack of one embodiment of the present application shown in FIG. 4;
fig. 6 is a schematic view of an electric device in which a secondary battery according to an embodiment of the present application is used as a power source;
FIG. 7 is an X-ray diffraction pattern of a carbon material according to an embodiment of the present application;
FIG. 8 is a Raman spectrum of a carbon material according to an embodiment of the present application;
reference numerals illustrate:
1, a battery pack; 2, upper box body; 3, lower box body; 4, a battery module; 5 a secondary battery; 51 a housing; 52 electrode assembly; 53 cover plates.
Detailed Description
Exemplary embodiments of the present disclosure will be described in more detail below. It should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
The "range" disclosed herein is defined in terms of lower and upper limits, with a given range being defined by the selection of a lower and an upper limit, the selected lower and upper limits defining the boundaries of the particular range. Ranges that are defined in this way can be inclusive or exclusive of the endpoints, and any combination can be made, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Furthermore, if minimum range values 1 and 2 are listed and maximum range values 3, 4, and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise indicated, the numerical range "a-b" represents a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed throughout, and "0-5" is a shorthand representation of only a combination of these values. When a certain parameter is expressed as an integer of 2 or more, it is disclosed that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or the like.
All embodiments and alternative embodiments of the present application may be combined with each other to form new solutions, unless specifically stated otherwise.
All technical features and optional technical features of the present application may be combined with each other to form new technical solutions, unless specified otherwise.
All steps of the present application may be performed sequentially or randomly, preferably sequentially, unless otherwise indicated. For example, the method comprises steps (a) and (b), meaning that the method may comprise steps (a) and (b) performed sequentially, or may comprise steps (b) and (a) performed sequentially. For example, it is mentioned that the method may further comprise step (c), meaning that step (c) may be added to the method in any order, e.g. the method may comprise steps (a), (b) and (c), may also comprise steps (a), (c) and (b), may also comprise steps (c), (a) and (b), etc.
Reference herein to "comprising" and "including" means open ended, as well as closed ended, unless otherwise noted. For example, the terms "comprising" and "comprises" may mean that other components not listed may be included or included, or that only listed components may be included or included.
The cathode material is one of the key factors restricting the performance of the sodium ion battery at present. Sodium ion anode materials currently exist with a larger atomic radius of sodium ions than lithium ions, for example, the intercalation and storage of sodium ions are easily limited by the smaller spacing of graphite layers by adopting the traditional graphite anode materials. Accordingly, it is desirable in the art to develop negative electrode materials that are more suitable for sodium ion batteries, common negative electrode materials including hard carbon. However, the hard carbon materials in the prior art have the defects of poor cycle performance, insufficient capacity retention rate and the like.
According to the method, the novel carbon material is provided by optimizing the displacement relation of the carbon material relative to different liquid probes, and the pore channel structure of the carbon material is suitable for embedding and extracting sodium ions, so that the rate capability of the secondary battery is improved.
The technical scheme described in the embodiments of the present application is applicable to a carbon material, a preparation method of the carbon material, a negative electrode tab including the carbon material, a secondary battery including the negative electrode tab, a battery module using the secondary battery, a battery pack using the secondary battery or the battery module, and an electric device using at least one of the secondary battery, the battery module, and the battery pack.
Carbon material
In some embodiments, a carbon material is provided, the carbon material having a pore structure;
The carbon material has an exhaust gas amount A with respect to water and an exhaust gas amount B with respect to methanol, which are obtained by a liquid probe measurement method; and 0 < A/B is less than or equal to 6.
Sodium ions are intercalated, deintercalated and stored in the negative electrode, and related dynamics are related to the microscopic pore channel structure of the carbon material. The carbon material provided by the embodiment of the application has a loose pore structure, and the pore characteristics are described through liquid probe molecules. The amount of gas that can be exchanged out of the water characterizes the total volume of the channels that sodium ions can go in and out of. The kinetic diameter of methanol is larger than that of water, and if the methanol cannot enter the pore canal which can be detected by the water, the pore canal is narrow, so that the rapid transmission of sodium ions is not facilitated; if it is accessible to both water and methanol, it is indicated that it is suitable for rapid transport of sodium ions. Therefore, if a considerable part of the gas which can be exchanged by water in the carbon material can be exchanged by methanol, namely, the condition that the A/B is less than or equal to 6 is satisfied, the whole pore structure of the carbon material is suitable for embedding and extracting sodium ions, thereby being beneficial to improving the multiplying power performance of the secondary battery.
The liquid probe measurement method specifically comprises the following steps: the carbon material was first dried in vacuo at 120 ℃ for 12 h and then stored in a dry environment (relative humidity less than 1.5%) for 3 days for subsequent measurement. The carbon material and probe liquid (mass ratio of carbon material to probe liquid 1:1.5) were placed in a soft inflatable air bag at 20 ℃ and 50% relative humidity while avoiding contact with each other. The air bag was then sealed, the volume V0 of the air bag was measured by a drainage method, the carbonaceous material in the bag and the probe liquid were thoroughly mixed by pressing and then allowed to stand for a time t, and the final volume V1 was recorded. Wherein the standing time t is at least three days, and the volume change of the air bag is less than 0.3% in 24 hours after the standing time t. The calculation formula of the displacement is (V1-V0)/M, wherein M is the mass of the carbonaceous material and is not less than 20g.
In some embodiments, water is used as the probe liquid, and the displacement of the carbon material relative to the water is measured. In some embodiments, methanol is used as the probe liquid, and the displacement of the carbon material relative to methanol is measured. In some embodiments, using a mixed solution of ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1 as the probe liquid, the displacement of the carbon material relative to the mixed solution of ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1 is measured.
The drainage method specifically comprises the following steps: firstly, preparing a beaker with matched air bag size, filling a certain amount of water in the beaker, placing the beaker on a balance, and clearing the mass of the beaker. The air bag was then completely immersed in water and was kept free from contact with the beaker wall and the beaker bottom, and the change in mass of the balance was recorded. According to the Archimedes buoyancy principle, the balance mass change can be converted into the air bag volume change, so that the purpose of measuring the volume change value is realized.
In some embodiments, the value of A/B is 5 or less. In some embodiments, the value of A/B is 4 or less. In some embodiments, the value of A/B is 3 or less. In some embodiments, the value of A/B is 2 or less. In some embodiments, the value of A/B is 1 or less.
In some embodiments, the carbon material has an exhaust gas amount C relative to a mixed solution of ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1 obtained by liquid probe measurement; and B/C is more than or equal to 5.
The volume of the gas which can be discharged by the mixed solution of the ethylene carbonate and the dimethyl carbonate according to the volume ratio of 1:1 is approximate to the volume of a pore channel which can be entered by the electrolyte. B/C is more than or equal to 5, which indicates that most of the gas which can be exchanged by methanol in the carbon material cannot be exchanged by the mixed solution consisting of ethylene carbonate and dimethyl carbonate, and the pore structure can be used as a sodium storage site in the carbon material and can not be filled by electrolyte to become an external volume which does not contribute to capacity.
In some embodiments, B is ≡0.05. 0.05 mL/g.
When the exhaust amount of the carbon material relative to methanol is more than or equal to 0.05 mL/g, the total pore structure suitable for sodium ion intercalation, deintercalation and storage is rich, and when the carbon material is used for a battery cathode, the carbon material can show better multiplying power performance.
In some embodiments, B < 55 mL/g.
In any embodiment, in the X-ray diffraction spectrum of the carbon material, the 002 peak corresponds to a 2 theta value between 22 ° and 24 °; in the Raman spectrum of the carbon material, id/Ig is 1.0-1.4, wherein Id represents that the Raman shift is 1350+/-50 cm -1 D peak intensity in the range, ig represents Raman shift of 1580+ -50 cm -1 G peak intensity in the range.
The X-ray diffraction spectrum may reflect the arrangement of atoms in the material, wherein the shape of the 002 peak specific to the carbon material may give information about the degree of amorphous carbon material. When the corresponding 2 theta value is between 22 degrees and 24 degrees, the carbon material has moderate amorphous degree, and the structural requirement of the sodium storage material is more easily met. In a specific embodiment of the present application, the X-ray diffraction spectrum is measured using an X-ray diffractometer, the test instrument is D8 Advance by bruck, and the target is copper.
The g peak in the raman spectrum of a carbon material can describe the degree of graphitization of the material, and the d peak is related to defects in the structure. Therefore, the degree of disorder of the carbon material can be expressed by the intensity ratio Id/Ig of the d peak and the g peak, and when the degree of disorder is higher, sodium storage sites can be more, but the first effect can be lower; conversely, decreasing order may increase first effect, but may result in decreased gram capacity. When the Id/Ig value meets the above conditions, the carbon material has moderate order degree, proper sodium storage gram capacity and first effect, and good multiplying power performance.
In the specific embodiment of the application, the raman spectrum of the carbon material is tested by using a raman spectrometer, d peak intensity and g peak intensity of 100 points are obtained during the test, id/Ig of 100 points is calculated, 30 Id/Ig of the largest and smallest are removed, and the average value of the remaining 40 Id/Ig is used as Id/Ig of the carbon material. The test instrument is specifically a Horiba LabRAM HR800 Raman spectrometer. The test conditions specifically include: excitation wavelength 532nm, grating 600, objective lens 50 times, integration time 10s, accumulated times 3 times, and surface scanning.
In some embodiments, the carbon material has a volume particle diameter Dv50 of 3-7 μm; for example, it may be about 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, etc.
In some embodiments, the carbon material has a volume particle diameter Dv90 of 9-18 μm; for example, it may be about 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, etc.
When the volume particle diameters Dv50 and Dv90 of the carbon material are respectively in the above ranges, the construction of smooth ion and electron transmission channels at the pole piece level is facilitated, and the rate capability of the secondary battery is improved.
In a specific embodiment of the present application, the volume particle sizes Dv50, dv90 of the carbonaceous material are measured by reference to the GB/T19077-2016 particle size distribution laser diffraction method. The test instrument is in particular a Mastersizer 2000E laser particle size analyzer from malvern instruments, uk.
In some embodiments, the carbon material has a specific surface area of 0.1 m 2 /g~50 m 2 /g; for example, may be about 0.1 m 2 /g、0.5 m 2 /g、1 m 2 /g、5 m 2 /g、10 m 2 /g、15 m 2 /g、20 m 2 /g、25 m 2 /g、30 m 2 /g、35 m 2 /g、40 m 2 /g、45 m 2 /g、50 m 2 /g, etc.
When the specific surface area of the carbon material is low, active ions consumed in SEI film formation are reduced, so that the first effect is improved; on the other hand, the higher specific surface area of the carbon material can be beneficial to the transmission of active ions. Therefore, when the specific surface area of the carbon material is within the above range, the above advantages can be combined, thereby obtaining a good gram capacity and initial efficiency, while having good rate performance.
Preparation method of carbon material
In some embodiments, a method of making a carbon material is provided, comprising: preheating a carbon precursor to obtain an intermediate; carbonizing the intermediate to prepare a carbon material; the carbon material is obtained by a liquid probe measurement method, and the exhaust gas amount of the carbon material relative to water is A, and the exhaust gas amount relative to methanol is B; and 0 < A/B is less than or equal to 6.
By performing the above-described treatment on the carbon precursor, the formation of the pore structure of the carbon material can be controlled by the pretreatment and carbonization treatment, thereby preparing the above-described carbon material.
In some embodiments, the carbonization treatment comprises: sequentially performing first heating and second heating on the intermediate; the first heating includes: heating to T2, and then performing first heat preservation, wherein T2 is 300-800 ℃, such as 300 ℃, 400 ℃, 500 ℃, 600 ℃, 700 ℃, 800 ℃ and the like; the second heating includes: and heating to T3, and then performing second heat preservation, wherein T3 is 1000-1700 ℃, and can be about 1000 ℃, 1100 ℃, 1200 ℃, 1300 ℃, 1400 ℃, 1500 ℃, 1600 ℃, 1700 ℃ and the like.
The intermediate is carbonized by the staged heating method, so that pyrolysis, carbonization and local graphitization can be realized step by step, and a regular pore structure is easy to form at the local graphitization position.
T3 affects the pore structure of the carbon material mainly by: when T3 is higher, the local graphitization degree is increased, a regular pore structure is easy to form, and the A/B value is increased; as the T3 value decreases, the average distance between carbon atoms becomes longer, a loose pore structure is easily formed, resulting in an increase in the B value and a decrease in the a/B value; as the T3 temperature is further reduced, the degree of carbon structure amorphization increases, pore size structure further expands, resulting in a decrease in B/C value.
In some embodiments, the first heating step has a ramp rate of less than or equal to 1 ℃/min.
In the first heating process, the heating rate not exceeding 1 ℃/min is adopted, so that a through pore canal structure is formed in the heating process, a channel for gas to escape rapidly is generated, the collapse of the pore canal structure caused by the impact of a large amount of gas generated by heating is avoided, and macropores or macropores are formed, so that the B/C value can be reduced.
In some embodiments, the first incubation time is t2, t2 is 1-50 h, and may be, for example, about 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h, 20 h.
Under certain temperature conditions, the heat preservation time can influence the graphitization degree of the material. When the heat preservation time is adopted, the local graphitization degree is improved, and a regular pore structure is easy to form. Overall, a slightly longer hold time helps to increase the a/B value and a slightly shorter hold time helps to decrease the a/B value, e.g., a hold time that is too short, e.g., shorter than 1 h, may result in insufficient carbonization, resulting in an undesirable pore structure that negatively affects the sodium storage process.
In some embodiments, the preheating treatment comprises: heating to T1; t1 is 200-700 ℃; for example, the temperature may be about 200 ℃, 300 ℃, 400 ℃, 500 ℃, 600 ℃, 700 ℃, or the like.
The carbon precursor can be carbonized at a low temperature through the preheating treatment, which is favorable for the advanced forming of the carbon skeleton, so that a certain pore structure is maintained in the subsequent carbonization and activation. During the preheating treatment, the degree of crosslinking between the macromolecules increases, and the pore structure is slowly formed and cured. Specifically, the temperature of the preheating treatment has the following effect on the a/B value: when the preheating temperature is lower, the formed framework is loose, the advanced forming effect is not obvious, the graphitization process of the finally obtained carbonaceous material is more free, the local graphitization degree is increased, and the A/B value is increased; the adoption of proper preheating temperature (for example, 200-700 ℃) is beneficial to the advanced curing of the framework, so that the A/B value is proper; the use of excessively high pre-heat treatment temperatures (e.g., above 700 ℃) tends to result in difficult removal of the occupied impurities, which negatively impacts the final carbon material properties.
In some embodiments, the preheating treatment is followed by the steps of: removing impurities; the impurity removal includes an acidic solution washing step and/or an alkaline solution washing step.
During the preheating treatment, a small amount of impurities are generated, and the impurities play an auxiliary role in occupying space. This portion of the impurities can be removed by acidic solution washing and/or alkaline solution washing, leaving behind the corresponding pores.
In some embodiments, the removing of impurities comprises an acidic solution washing step and an alkaline solution washing step. In some embodiments, the removing impurities sequentially comprises the steps of: acidic solution washing, water washing, alkaline solution washing, water washing and drying. In some embodiments, the removing impurities sequentially comprises the steps of: washing with alkaline solution, washing with water, washing with acidic solution, washing with water, and drying. Deionized water can be adopted for the water washing, the water washing times can be one or more times until the pH of the filtrate is neutral (namely, the pH is 7+/-0.5), and the water washing process is considered to be completed. The drying may be air drying or vacuum drying until the mass change rate of the material after the interval of 2 hours is < 0.1wt%, and the drying process is considered to be completed.
In some embodiments, the carbon precursor comprises at least one selected from the group consisting of: biomass materials, high molecular polymers, coal and secondary processed products thereof.
Any known raw material suitable for preparing hard carbon can be adopted for preparing the carbon material, and when biomass materials are selected, the biomass material has the advantages of low raw material cost, environmental protection and the like.
In some embodiments, the carbon precursor may include a high molecular polymer, such as polyacrylonitrile, phenolic resin, epoxy resin (e.g., polyethylene oxide), polyethylene terephthalate, polyfurfuryl alcohol, and the like.
In some embodiments, the carbon precursor may include coal, such as bituminous coal, subbituminous coal, anthracite coal, fat coal, lean coal, and the like; and secondary processed products thereof such as semi-coke, coking, etc.
In some embodiments, the biomass material comprises at least one selected from the group consisting of: wood (e.g., pine, poplar, etc.), straw, bamboo, bark, fruit shells (e.g., walnut shells, coconut shells, etc.), fruit pits (e.g., date pits), starch, sucrose, cellulose, lignin, hemicellulose, chitin, pectin, xylan, chitosan, and protein.
Different biomass materials have unique component compositions and morphological characteristics, so that the physical and chemical property changes in the subsequent carbonization process are determined to a great extent, and finally the pore structure characteristics of the carbonized carbonaceous materials are determined. Wherein, materials such as bamboo, pine, poplar, straw and the like naturally contain rich pore channel structures, and impurities in the materials can leave a large number of pore channels when removed; the carbonaceous materials obtained by taking the materials as precursors have loose pore channel structures, and have lower corresponding A/B values and larger B values. When biomolecular monomers such as starch, sucrose, lignin, cellulose, hemicellulose and the like are used as precursors, the pores formed at last are easy to be more and irregular because the process involves a random molecular cross-linking coupling process, the corresponding A/B value can be lower, and the B/C value can be larger. For denser precursors such as walnut shells, date pits and coconut shells, the pore canal of the finally formed carbonaceous material is compact and regular, and the corresponding A/B value can be larger.
In some embodiments, the carbon precursor is subjected to the following pretreatment prior to the preheating treatment: crushing. The crushing may employ processes known in the art that are suitable for crushing in the preparation of carbonaceous materials, for example, the crushing may include one or both of ball milling crushing, air jet milling crushing.
In some embodiments, a method of preparing a carbon material includes:
s1, providing a carbon precursor, wherein the carbon precursor comprises a biomass material;
s2, crushing the carbon precursor;
s3, preheating: heating the crushed carbon precursor in the step S2 in a protective atmosphere, and heating to T1 at a heating rate of less than or equal to 2 ℃/min, wherein T1 is 200-700 ℃; cooling to room temperature after heat preservation to obtain an intermediate;
s4, removing impurities: removing impurities from the intermediate obtained in the step S3, wherein the removing impurities sequentially comprise acid solution washing, water washing, alkaline solution washing, water washing and drying, or alkaline solution washing, water washing, acid solution washing, water washing and drying;
s5, carbonization treatment: sequentially performing first heating and second heating on the intermediate subjected to impurity removal in the step S3; the first heating includes: heating to T2 at a heating rate less than or equal to 1 ℃/min, and then carrying out first heat preservation, wherein the temperature of T2 is 300-800 ℃, and the time T2 of the first heat preservation is 1-50 h; the second heating includes: and (3) heating to T3, and then carrying out second heat preservation, wherein the temperature of T3 is 1000-1700 ℃, and the time T3 of the second heat preservation is 1-10 h.
Negative pole piece
In some embodiments, a negative electrode tab is provided that includes the carbon material of any of the embodiments of the present application.
In some embodiments, the negative electrode tab includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, the negative electrode active material layer including a negative electrode active material including a carbon material as in any of the examples herein. As an example, the anode current collector has two surfaces opposing in its own thickness direction, and the anode active material layer is provided on either one or both of the two surfaces opposing the anode current collector.
In some embodiments, the negative electrode current collector may employ a metal foil or a composite current collector. For example, as the metal foil, copper foil may be used. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
In some casesIn an embodiment, the anode active material layer comprises an anode active material comprising a carbon material provided in any of the embodiments herein. In some examples, only the carbon material provided in any of the embodiments of the present application was used as the anode active material. In other embodiments, the negative active material may also include other negative active materials for batteries known in the art. For example, the anode active material includes one or a combination of two or more selected from the group consisting of: natural graphite, artificial graphite, mesocarbon microbeads (MCMB), hard carbon, soft carbon, silicon-carbon composites, li-Sn alloys, li-Sn-O alloys, sn, snO, snO 2 、TiO 2 -Li 4 Ti 5 O 12 Li-Al alloy.
In some embodiments, the anode active material layer further optionally includes a binder. For example, the binder may include one or a combination of two or more selected from the group consisting of: styrene Butadiene Rubber (SBR), polyacrylic acid (PAA), sodium Polyacrylate (PAAs), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium Alginate (SA), polymethacrylic acid (PMAA), carboxymethyl chitosan (CMCS).
In some embodiments, the anode active material layer may further optionally include a conductive agent. For example, the conductive agent may include one or a combination of two or more selected from the group consisting of: super P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
In some embodiments, the anode active material layer may further optionally include other adjuvants. For example, the other auxiliary agent may be a thickener such as sodium carboxymethylcellulose (CMC-Na).
In some embodiments, the negative electrode sheet may be prepared by: dispersing the above components for preparing the anode active material layer, such as the anode active material, the conductive agent, the binder, and any other components, in a solvent (e.g., deionized water) to form an anode slurry; and coating the negative electrode slurry on a negative electrode current collector, and obtaining a negative electrode plate after the procedures of drying, cold pressing and the like.
Secondary battery
In some embodiments, a secondary battery is provided that includes a positive electrode tab, a negative electrode tab, an electrolyte, and a separator; wherein, the negative pole piece is the negative pole piece that this application arbitrary embodiment provided. The secondary battery may be, for example, a lithium ion battery, a sodium ion battery, or a potassium ion battery.
[ Positive electrode sheet ]
The positive electrode plate comprises a positive electrode current collector and a positive electrode material arranged on at least one surface of the positive electrode current collector, wherein the positive electrode material comprises a positive electrode active material.
In some embodiments, the positive current collector may employ a metal foil or a composite current collector. For example, as the metal foil, aluminum foil may be used. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
In some embodiments, when the secondary battery is a sodium-ion battery, the positive electrode active material may employ a positive electrode active material for a sodium-ion battery, which is well known in the art. As an example, the positive electrode active material may be used alone, or two or more kinds may be combined. Wherein the positive electrode active material is selected from sodium-iron composite oxide (NaFeO) 2 ) Sodium cobalt composite oxide (NaCoO) 2 ) Sodium chromium composite oxide (NaCrO) 2 ) Sodium manganese composite oxide (NaMnO) 2 ) Sodium nickel composite oxide (NaNiO) 2 ) Sodium nickel titanium composite oxide (NaNi) 1/2 Ti 1/2 O 2 ) Sodium nickel manganese composite oxide (NaNi) 1/2 Mn 1/2 O 2 ) Sodium iron manganese composite oxide (Na 2/3 Fe 1/3 Mn 2/3 O 2 ) Sodium nickel cobalt manganese composite oxide (NaNi) 1/3 Co 1/3 Mn 1/3 O 2 ) Sodium iron phosphate compound (NaFePO) 4 ) Sodium manganese phosphate compound (NaMn) P O 4 ) Sodium cobalt phosphate compound (NaCoPO) 4 ) Prussian blue type materials, polyanionic materials (phosphates, fluorophosphates, pyrophosphates, sulfates), etc., but the present invention is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials for sodium ion batteries may be used.
In some embodiments, the positive electrode material may further optionally include a binder. For example, the binder may include one or a combination of two or more selected from the group consisting of: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluoroacrylate resin.
In some embodiments, the positive electrode material further optionally includes a conductive agent. For example, the conductive agent may include one or a combination of two or more selected from the group consisting of: super P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
In some embodiments, the positive electrode sheet may be prepared by: dispersing the above positive electrode material, such as a positive electrode active material, a conductive agent, a binder, and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; and (3) coating the positive electrode slurry on a positive electrode current collector, and obtaining a positive electrode plate after the procedures of drying, cold pressing and the like.
[ negative electrode sheet ]
The negative electrode piece provided by any embodiment of the application is adopted.
[ isolation Membrane ]
The separator is not particularly limited in this application, and any known porous separator having electrochemical stability and mechanical stability may be used according to practical requirements. For example, the separator may be a single-layer or multi-layer film containing one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride.
[ electrolyte ]
The electrolyte plays a role in ion conduction between the positive electrode plate and the negative electrode plate. The electrolyte includes an electrolyte salt and a solvent.
In some embodiments, when the secondary battery is a sodium ion battery, the electrolyte salt includes a sodium salt; as an example, the sodium salt may be selected from NaPF 6 、NaClO 4 、NaBCl 4 、NaSO 3 CF 3 Na (CH) 3 )C 6 H 4 SO 3 One or more of them.
In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methylethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1, 4-butyrolactone, sulfolane, dimethyl sulfone, methyl sulfone, and diethyl sulfone.
In some embodiments, the electrolyte further optionally includes an additive. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives capable of improving certain properties of the battery, such as additives that improve the overcharge performance of the battery, additives that improve the high or low temperature performance of the battery, and the like.
[ preparation of Secondary Battery ]
The positive electrode plate, the negative electrode plate and the isolating film can be manufactured into an electrode assembly through a winding process or a lamination process, and then the electrode assembly is packaged through an outer package and then electrolyte is injected, so that the secondary battery is manufactured.
Wherein the overwrap may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, or the like. The overwrap may also be a flexible package, such as a bag-type flexible package. The material of the flexible bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.
The shape of the secondary battery is not particularly limited in the present application, and may be cylindrical, square, or any other shape. For example, fig. 1 is a secondary battery 5 of a square structure as one example.
In some embodiments, referring to fig. 2, the outer package may include a housing 51 and a cover 53. The housing 51 may include a bottom plate and a side plate connected to the bottom plate, where the bottom plate and the side plate enclose a receiving chamber. The housing 51 has an opening communicating with the accommodation chamber, and the cover plate 53 can be provided to cover the opening to close the accommodation chamber. The positive electrode tab, the negative electrode tab, and the separator may be formed into the electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is enclosed in the accommodating chamber. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and those skilled in the art may select according to specific practical requirements.
Battery module and battery pack
In some embodiments, the secondary batteries may be assembled into a battery module, and the number of secondary batteries included in the battery module may be one or more, and the specific number may be selected by one skilled in the art according to the application and capacity of the battery module.
Fig. 3 is a battery module 4 as an example. Referring to fig. 3, in the battery module 4, a plurality of secondary batteries 5 may be sequentially arranged in the longitudinal direction of the battery module 4. Of course, the arrangement may be performed in any other way. The plurality of secondary batteries 5 may be further fixed by fasteners.
Alternatively, the battery module 4 may further include a case having an accommodating space in which the plurality of secondary batteries 5 are accommodated.
In some embodiments, the secondary battery may also be assembled into a battery pack.
In some embodiments, the battery modules 4 may also be assembled into a battery pack, and the number of battery modules included in the battery pack may be one or more, and the specific number may be selected by one skilled in the art according to the application and capacity of the battery pack.
Fig. 4 and 5 are battery packs 1 as an example. Referring to fig. 4 and 5, a battery case and a plurality of battery modules 4 disposed in the battery case may be included in the battery pack 1. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be covered on the lower box body 3 and forms a closed space for accommodating the battery module 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.
Power utilization device
The application also provides an electric device comprising the secondary battery provided by the application. In certain embodiments, the power device comprises at least one of a battery module, or a battery pack provided herein. The secondary battery, the battery module, or the battery pack may be used as a power source of the power device, and may also be used as an energy storage unit of the power device. The power utilization device may include mobile devices (e.g., cell phones, notebook computers, etc.), electric vehicles (e.g., electric only vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.
As the electricity consumption device, a secondary battery, a battery module, or a battery pack may be selected according to the use requirements thereof.
Fig. 6 is an electrical device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle or the like. In order to meet the high power and high energy density requirements of the secondary battery by the power consumption device, a battery pack or a battery module may be employed.
As another example, the device may be a cell phone, tablet computer, notebook computer, or the like. The device is generally required to be light and thin, and a secondary battery can be used as a power source.
Example 1
Carbon material
The embodiment first provides a carbon material, which is prepared by the following steps:
s1, according to the mass ratio of 1:1 weighing glucose and polyethylene oxide (PEO, average molecular weight is 600000) as carbon precursors;
s2, crushing the carbon precursor provided in the step S1 to a particle size of about 6 mu m by adopting a ball milling method;
s3, preheating: placing the carbon precursor crushed in the step S2 into a kiln, introducing argon as a shielding gas, heating to T1 at a speed of 2 ℃/min, keeping the temperature of T1 at 400 ℃, and naturally cooling to room temperature to obtain an intermediate;
s4, performing impurity removal treatment on the intermediate obtained in the step S3, wherein the method sequentially comprises the following steps: washing with 3mol/L perchloric acid water solution at 60 ℃ for 12 hours, washing with deionized water to be neutral in pH (pH is 7+/-0.5), washing with 3mol/L NaOH water solution at 95 ℃ for 24 hours, washing with deionized water to be neutral in pH (pH is 7+/-0.5), and air drying; the standard of the completion of the drying procedure is as follows: the mass change rate of the material after the interval of 2h is less than 0.1wt%;
S5, carbonization treatment: placing the intermediate subjected to impurity removal in the step S4 into a kiln, introducing argon as a shielding gas, controlling the pressure of a hearth tower to be less than or equal to-2 kPa, then heating to T2 at a speed of less than or equal to 1 ℃/min, wherein T2 is 800 ℃, and preserving heat T2 and T2 is 3 h; then heating to T3 at a speed of less than or equal to 1 ℃/min, wherein T3 is 1200 ℃, and the temperature is kept at T3 and T3 is 6 h, so that the carbon material is obtained after the end.
Test battery assembly
Fully stirring and mixing the prepared carbon material, a binder Styrene Butadiene Rubber (SBR), a thickener sodium carboxymethylcellulose (CMC-Na) and a conductive agent carbon black in a proper amount of solvent deionized water according to a mass ratio of 96.2:1.8:1.2:0.8 to form uniform negative electrode slurry; and uniformly coating the negative electrode slurry on the surface of a negative electrode current collector copper foil, and drying in an oven to obtain the negative electrode plate. Mixing Ethylene Carbonate (EC), ethylmethyl carbonate (EMC) and diethyl carbonate (DEC) according to a volume ratio of 1:1:1 to obtain an organic solvent, and then mixing NaPF 6 Dissolving in the organic solvent to obtain NaPF 6 An electrolyte with a concentration of 1 mol/L. The negative electrode plate and the electrolyte are adopted, a metal sodium plate is used as a counter electrode, a Polyethylene (PE) film is used as an isolating film, and the CR2430 button cell is assembled in a glove box protected by argon.
Detection of
And detecting parameters such as the displacement, the particle size, the X-ray diffraction spectrum, the Raman spectrum, the specific surface area and the like of the prepared carbon material relative to a probe liquid (a mixed solution of water, methanol, ethylene carbonate and dimethyl carbonate according to the volume ratio of 1:1), and detecting the performance of the button cell prepared by the carbon material.
(1) Carbon material parameter detection
And detecting the displacement of the carbon material by adopting a liquid probe method, wherein water, methanol and a mixed solution consisting of ethylene carbonate and dimethyl carbonate according to a volume ratio of 1:1 are respectively used as probe liquids. The carbon material was detected and calculated to have an air displacement A relative to water of 13.63 mL/g, an air displacement B relative to methanol of 12.22 mL/g, and an air displacement C relative to a mixed solution of ethylene carbonate and dimethyl carbonate at a volume ratio of 1:1 of 0.21 mL/g.
Further, the X-ray diffraction spectrum of the above carbon material was examined as shown in fig. 7, in which the 002 peak corresponds to a 2 θ value of 22 ° to 24 °; the Raman spectrum is shown in FIG. 8, wherein the Raman shift is 1350+ -50 cm -1 D peak intensity Id and Raman shift within the range are 1580 + -50 cm -1 The ratio Id/Ig of the g-peak intensities Id in the range was 1.25. The volume particle diameter Dv50 of the carbon material is 6 μm, dv90 is 10 μm, and the specific surface area is 5m 2 /g。
(2) Capacity retention rate
At 25 ℃, firstly, discharging the button cell to 0V at constant current with current density of 10mA/g, and recording the first-circle discharge capacity of the button cell; then, the battery was charged to 2.0V at a constant current density of 10mA/g, and the first-turn charge capacity Q0 of the button cell was recorded.
Then, a discharge and charge cycle between 0 and 2V was performed at a selected current density, and the stabilized charge capacity was recorded as Q1. Thus, the capacity retention rate of the battery at this current density was Q1/q0×100%.
The battery was tested to have a capacity retention of 98.1% at 0.3A/g, 95.5% at 0.6A/g and 91.7% at 1.2A/g.
Examples 2 to 18, comparative examples 1 to 2
Examples 2 to 5, 10 to 14 and comparative examples 1 to 2 employ carbon precursors with the same mass ratio as example 1, namely 1:1 glucose and PEO as carbon precursors; examples 6 to 9 use glucose and PEO in a mass ratio of 2:1 as carbon precursors, example 15 uses glucose and PEO in a mass ratio of 1.5:1 as carbon precursors, examples 16 to 17 use glucose and PEO in a mass ratio of 1.2:1 as carbon precursors, and example 18 uses starch as carbon precursors; further, the same procedure as in example 1 was followed except for the step parameters in table 1 to prepare a carbon material and test cells. The results of the detection of the prepared carbon material and battery are recorded in table 2.
TABLE 1
TABLE 2
According to the above experimental results, compared with comparative examples 1 to 2, when the ratio a/B of the carbon material to the water displacement a and the methanol displacement B is not more than 6, the rate performance of the battery can be significantly improved.
As is clear from the comparison between example 18 and other examples (in particular, example 4), the improvement of the battery performance was more advantageous when the displacement B of the carbon material relative to methanol was 0.05 mL/g or more. This is mainly because the exhaust gas amount B reflects the pore structure and volume suitable for sodium ion deintercalation in the carbon material, and when the exhaust gas amount B is too small, it indicates that the total volume of the pores is too small, which may be unfavorable for rapid deintercalation of sodium ions, so that the adoption of the exhaust gas amount B of 0.05 mL/g or more is more favorable for rapid deintercalation of sodium ions, thereby improving the rate performance of the battery.
As can be seen from comparative examples 2 to 5 or comparative examples 13 to 14, the improvement of the battery performance is more advantageous when the ratio B/C of the displacement B of the carbon material with respect to methanol to the displacement C of the mixed solution of ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1 is 5 or more. This is mainly because if the value of B/C is too small, it indicates that the pore volume that can be detected by both methanol and the mixed solution of ethylene carbonate and dimethyl carbonate is large, and this part of the pores is easily filled with the electrolyte, so that the effect of closed-cell sodium storage cannot be obtained. When the B/C value is greater than or equal to 5, most of the pores can be used as sodium storage spaces.
The foregoing is merely a preferred embodiment of the present application, but the scope of the present application is not limited thereto, and any changes or substitutions easily contemplated by those skilled in the art within the technical scope of the present application should be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims (10)

1. A carbon material, characterized in that the carbon material has a pore structure;
the carbon material is obtained by a liquid probe measurement method, the air displacement relative to water is A, the air displacement relative to methanol is B, and the air displacement relative to a mixed solution of ethylene carbonate and dimethyl carbonate according to a volume ratio of 1:1 is C; and A/B is more than 0 and less than or equal to 6, and B/C is more than or equal to 5;
the preparation method of the carbon material comprises the following steps:
preheating a carbon precursor to obtain an intermediate; the carbon precursor is glucose and polyethylene oxide; the preheating treatment includes: heating to T1; the T1 is 200-700 ℃; then removing impurities from the intermediate by washing with an acidic solution; carbonizing the intermediate to prepare the carbon material;
wherein the carbonization treatment comprises: sequentially performing first heating and second heating on the intermediate; the first heating includes: heating to T2 at a heating rate of less than or equal to 1 ℃/min, and then carrying out first heat preservation, wherein the temperature of T2 is 300-800 ℃, the time of the first heat preservation is T2, and the time of T2 is 1-50 h; the second heating includes: and (3) heating to T3, and then carrying out second heat preservation, wherein T3 is 1000-1700 ℃.
2. The carbon material of claim 1, wherein a/B has a value of 3 or less.
3. The carbon material according to any one of claims 1 to 2, wherein B is not less than 0.05 mL/g.
4. The carbon material according to claim 3, wherein in the X-ray diffraction spectrum of the carbon material, a 2-theta value corresponding to a 002 peak is 22 ° to 24 °; in the Raman spectrum of the carbon material, id/Ig is 1.0-1.4, wherein Id represents that the Raman shift is 1350+/-50 cm -1 D peak intensity in the range, ig represents Raman shift of 1580+ -50 cm -1 G peak intensity in the range.
5. The carbon material according to claim 3, wherein the carbon material has a volume particle diameter Dv50 of 3 to 7 μm and a Dv90 of 9 to 18 μm.
6. The carbon material according to claim 3, wherein the specific surface area of the carbon material is 0.1 to 50 m 2 /g。
7. The method for producing a carbon material according to any one of claims 1 to 6, comprising: preheating a carbon precursor to obtain an intermediate; the preheating treatment includes: heating to T1; the T1 is 200-700 ℃; then removing impurities from the intermediate by washing with an acidic solution; carbonizing the intermediate to prepare the carbon material;
Wherein the carbonization treatment comprises: sequentially performing first heating and second heating on the intermediate; the first heating includes: heating to T2 at a heating rate of less than or equal to 1 ℃/min, and then carrying out first heat preservation, wherein the temperature of T2 is 300-800 ℃, the time of the first heat preservation is T2, and the time of T2 is 1-50 h; the second heating includes: and (3) heating to T3, and then carrying out second heat preservation, wherein T3 is 1000-1700 ℃.
8. The negative electrode piece is characterized by comprising the carbon material according to any one of claims 1 to 6 or the carbon material prepared by the preparation method of the carbon material according to claim 7.
9. A secondary battery comprising the negative electrode tab of claim 8.
10. An electric device, characterized in that the electric device comprises the secondary battery according to claim 9.
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