CN116995231A

CN116995231A - Carbon material and preparation method thereof, negative electrode plate, secondary battery and power utilization device

Info

Publication number: CN116995231A
Application number: CN202311242110.4A
Authority: CN
Inventors: 吴凯; 许逸达; 张欣欣; 陈晓霞; 刘犇; 刘士坤; 马宇
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2023-09-25
Filing date: 2023-09-25
Publication date: 2023-11-03
Anticipated expiration: 2043-09-25
Also published as: CN116995231B

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 structure, the carbon material has an exhaust gas quantity A relative to water and an exhaust gas quantity B relative to dichloromethane, which are obtained by a liquid probe measurement method; and A/B is less than or equal to 2. When the carbon material is used for a negative electrode material of a secondary battery, the micro-pore structure of the carbon material is beneficial to improving the sodium ion migration rate under the low-temperature condition, so that the secondary battery using the carbon material has good low-temperature performance.

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 low-temperature performance and the like.

Disclosure of Invention

The application aims to provide a carbon material, a preparation method thereof, a negative electrode plate, a secondary battery and an electric device, wherein the carbon material has a certain micro-pore structure, and is favorable for improving the sodium ion migration rate under the low-temperature condition by representing the displacement relative to probe liquid, so that the low-temperature performance of the secondary battery can be improved.

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 air displacement relative to water is A, and the air displacement relative to dichloromethane is B; and A/B is less than or equal to 2.

When the sodium ion battery works, the width of the pore channel structure in the cathode carbonaceous material has a great influence on the ion migration rate. The ion transmission rate in the narrower pore channels is slower, and the effect of the pore channels on the reduction of the ion transmission rate is particularly obvious at low temperature, so that the polarization of the whole system is obviously increased.

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 methylene chloride is slightly larger than that of water, and for these channels that can be detected by water, if they cannot be entered by methylene chloride, it is shown that they are narrower. Sodium ions located in the narrower channels undergo stronger interactions due to the closer distance from the surrounding carbon skeleton. Under low temperature conditions, i.e. with limited thermal movement, a greater potential is required to drive the sodium ions in the narrower pores, which means that the migration velocity of the sodium ions is reduced and greater polarization is produced. Therefore, when the amount of gas capable of being exchanged by water is mostly exchanged by methylene chloride (i.e., A/B.ltoreq.2 is satisfied), it is shown that the narrow pores occupy a relatively low proportion in the channel structure of the carbon material, so that the carbon material can maintain a relatively high sodium ion mobility even under low temperature conditions, thereby reducing polarization and improving low temperature performance of the battery.

In any embodiment, the value of A/B is 1.8 or less. In any embodiment, the A/B value is 1.5 or less. In any embodiment, the A/B value is 1.4 or less. In any embodiment, the value of A/B is 1.2 or less. In any embodiment, the value of A/B is 1.1 or less.

In any embodiment, A is greater than or equal to 0.1 mL/g.

The displacement a of the carbon material relative to water is related to the porosity richness of the carbon material. When the ratio A is more than or equal to 0.1 mL/g, the pore structure of the carbon material is rich, and the sufficient pore structure can be provided for the migration of sodium ions under the low-temperature condition, thereby being beneficial to the low-temperature performance of the battery.

In any embodiment, A is 2 mL/g or more. In any embodiment, A is 5 mL/g or more. In any embodiment, A is 10 mL/g or more. In any embodiment, A is 50 mL/g or greater. In any embodiment, A is 100 mL/g or more. In any embodiment, A is 150 mL/g or more.

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 producing a carbon material according to the first aspect of the present application, comprising: and carbonizing the carbon precursor to obtain the carbon material.

The carbon precursor is carbonized to form a pore structure, so that the carbon material according to the first aspect of the present application is prepared.

In any embodiment, the carbonization treatment comprises: the carbonization treatment includes: sequentially performing first heating and second heating on the carbon precursor; the first heating includes: heating to T1, and then carrying out first heat preservation, wherein the temperature of T1 is 300-800 ℃; the second heating includes: and (3) heating to T2, and then carrying out second heat preservation, wherein T2 is 1000-1700 ℃.

The carbon precursor 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 carbonization treatment further comprises the following steps: removing impurities from the carbon precursor; the impurity removal includes an acidic solution washing step and/or an alkaline solution washing step.

By acidic solution washing and/or alkaline solution washing, part of the impurities of the carbon precursor may be removed, leaving 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.

The preparation of the carbon material of the application can be carried out by adopting any known raw materials suitable for preparing hard carbon, and has the advantages of low raw material cost, environmental protection and the like when biomass materials are selected.

According to a third aspect of the application, a negative electrode piece is provided, wherein the negative electrode piece comprises the carbon material according to the first aspect of the application or the carbon material prepared by the preparation method according to the second aspect of the 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 according to 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 comprising the secondary battery according to the fourth aspect of the present application.

The foregoing description is only an overview of the present application, and in order that the present application may be more clearly understood by reference to the following detailed description, which refers to the accompanying drawings.

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 the 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 the 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 the present 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 of the application and alternative embodiments may be combined with each other to form new solutions, unless otherwise specified.

All technical features and optional technical features of the application may be combined with each other to form new technical solutions, unless specified otherwise.

All the steps of the present application may be performed sequentially or randomly, preferably sequentially, unless otherwise specified. 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.

The terms "comprising" and "including" as used herein mean open ended or 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 low-temperature performance and the like.

According to the application, through optimizing the displacement relation of the carbon material relative to different liquid probes, a novel carbon material is provided, and the pore channel structure of the carbon material is suitable for storing sodium in the battery circulation process, so that the low-temperature performance of the secondary battery is improved.

The technical scheme described in the embodiment of the application is applicable to a carbon material, a preparation method of the carbon material, a negative electrode plate containing the carbon material, a secondary battery containing the negative electrode plate, 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 methylene dichloride, which are obtained by a liquid probe measurement method; and A/B is less than or equal to 2.

The carbon material provided by the embodiment of the application has a specific pore structure, and the characteristics of the pore are described by 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 methylene chloride is slightly larger than that of water, and for these channels that can be detected by water, if they cannot be entered by methylene chloride, it is shown that they are narrower. Sodium ions located in the narrower channels undergo stronger interactions due to the closer distance from the surrounding carbon skeleton. Under low temperature conditions, i.e. with limited thermal movement, a greater potential is required to drive the sodium ions in the narrower pores, which means that the migration velocity of the sodium ions is reduced and greater polarization is produced. Therefore, when the amount of gas capable of being exchanged by water is mostly exchanged by methylene chloride (i.e., A/B.ltoreq.2 is satisfied), it is shown that the narrow pores occupy a relatively low proportion in the channel structure of the carbon material, so that the carbon material can maintain a relatively high sodium ion mobility even under low temperature conditions, thereby reducing polarization and improving low temperature performance of the 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, using methylene chloride as the probe liquid, the displacement of the carbon material relative to methylene chloride 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 any embodiment, the value of A/B is 1.8 or less; for example, the value of A/B may be about 1.7, 1.6, 1.5, 1.4, 1.3, 1.2, or 1.1.

In any embodiment, A is greater than or equal to 0.1 mL/g; for example, A may be about 0.1 mL/g, 0.2 mL/g, 0.5 mL/g, 1 mL/g, 2 mL/g, 5 mL/g, 10 mL/g, 20 mL/g, 30 mL/g, 40 mL/g, 50 mL/g, 60 mL/g, 70 mL/g, 80 mL/g, 90 mL/g, 100 mL/g, 110 mL/g, 120 mL/g, 130 mL/g, 140 mL/g, or 150 mL/g, etc.

In any embodiment, A.ltoreq.170 mL/g.

The displacement a of the carbon material relative to water is related to the stability of the carbon material. When the weight of the carbon material is less than or equal to 170 mL/g, the pore structure of the carbon material is not so much as to obviously reduce the overall stability of the material, and the collapse of the carbon material in the process of embedding/extracting sodium ions can be avoided.

The X-ray diffraction spectrum can reflect the arrangement form between atoms in the material, wherein the shape of the 002 peak specific to the carbon material can give information about the degree of amorphous carbon material. When the corresponding 2 theta value is between 22 and 24 degrees, the carbon material has moderate amorphous degree and is easier to meet the structural requirement as a sodium storage material. In a specific embodiment of the 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 carbonaceous material can describe the degree of graphitization of the material, and the d-peak is related to defects in the structure. The degree of disorder of carbonaceous materials is generally expressed by the ratio of the intensities of the d peak and g peak, id/Ig, and when the degree of disorder is high, the sodium storage sites may be more, but the first effect may be lower. Conversely, decreasing order may increase first effect, but may result in decreased gram capacity. When the method meets the conditions, the order degree of the carbonaceous material is moderate, and the carbonaceous material has proper sodium storage gram capacity and first effect.

In a specific embodiment of the application, the raman spectrum of the carbonaceous material is tested using a raman spectrometer, the d-peak intensity and g-peak intensity of 100 points are obtained during the test, the Id/Ig of 100 points is calculated, the maximum 30 Id/Ig and the minimum 30 Id/Ig are removed, and the average value of the remaining 40 Id/Ig is used as the Id/Ig of the carbonaceous 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 in the above range, the construction of a smooth ion and electron transmission channel at the pole piece level is facilitated, and the sodium storage performance of the secondary battery is improved.

In a specific embodiment of the present application, the volume particle diameters Dv50, dv90 of the carbon material are measured by a particle size distribution laser diffraction method according to GB/T19077-2016. 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 surface of the carbon material can be beneficial to the transmission of active ions. Therefore, when the body surface area of the carbon material is within the above range, a good gram capacity and a first effect can be obtained at the same time.

Preparation method of carbon material

In some embodiments, a method of making a carbon material is provided, comprising: carbonizing a carbon precursor to prepare a carbon material; the carbon material is obtained by a liquid probe measurement method, and the air displacement relative to water is A, and the air displacement relative to dichloromethane is B; and A/B is less than or equal to 2.

The carbon precursor is subjected to the carbonization treatment to form a pore structure, so that the carbon material is prepared.

In some embodiments, the carbonization treatment comprises: the carbonization treatment includes: sequentially performing first heating and second heating on the carbon precursor; the first heating includes: heating to T1, and then carrying out first heat preservation, wherein the temperature of T1 is 300-800 ℃; the second heating includes: and (3) heating to T2, and then carrying out second heat preservation, wherein T2 is 1000-1700 ℃.

Wherein T1 is 300-800 ℃, which can realize low-temperature carbonization of the carbon precursor and is beneficial to the advanced formation of the carbon skeleton, thereby maintaining a certain pore structure in the subsequent carbonization and activation. The low temperature carbonization helps to form a through pore structure, provides a fast escape channel, and avoids collapse of the pore structure under the impact of a large amount of gas generated by the second heating. T2 is 1000-1700 ℃, and under the temperature condition, the local graphitization degree is higher, and a regular pore structure is easy to form. T2 affects the pore structure of the carbon material mainly by: when T2 is higher, the local graphitization degree is increased, and a regular pore structure is easy to form, so that the A/B value is larger and the A value is smaller; as the T2 value decreases, the average distance between carbon atoms becomes longer, a loose pore structure is easily formed, resulting in a decrease in a/B value and an increase in a value.

In some embodiments, the first incubation time is t1 and the second incubation time is t2; t1 and t2 are each independently selected from 1 to 50 h, and may be, for example, each independently selected from about 1 h, 2h, 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, 30 h, 40 h, 50 h, and the like.

In some embodiments, the carbonization treatment is preceded by the further step of: removing impurities from the carbon precursor; the impurity removal includes an acidic solution washing step and/or an alkaline solution washing step.

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 method further comprises the following steps before the removing: preheating: the preheating treatment includes: heating to 200-700 ℃, preserving heat, and cooling to room temperature; for example, the heating may be performed to 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.

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.

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 the 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. In addition, when biomolecular monomers such as starch, sucrose, lignin, cellulose, hemicellulose and the like are used as precursors, the pores formed finally are easy to be more and irregular because the process involves a random molecular cross-linking coupling process. The corresponding A/B value of the carbon material prepared by the two carbon precursors may be smaller, and the A value may be larger. For very dense precursors such as walnut shells, date pits and coconut shells, the pore canal of the finally formed carbonaceous material is compact and regular, the corresponding A/B value can be larger, and the A value can be smaller.

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 200-700 ℃ at a heating rate of less than or equal to 2 ℃/min; 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 S4; the first heating includes: heating to T1 at a heating rate less than or equal to 1 ℃/min, and then carrying out first heat preservation, wherein the temperature T1 is 300-800 ℃, and the time T1 of the first heat preservation is 1-50 h; the second heating includes: and (3) heating to T2, and then carrying out second heat preservation, wherein the temperature of T2 is 1000-1700 ℃, and the time T2 of the second heat preservation is 1-50 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 the carbon material of any of the embodiments of the present application. 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 embodiments, the negative electrode active material layer comprises a negative electrode active material comprising a carbon material provided by any of the embodiments of the present application. In some examples, only the carbon material provided in any one 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 electrode plate is the negative electrode plate provided by any embodiment of the application. 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 ) Composite oxidation of sodium nickel manganeseObject (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 (NaMnPO) 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, and any known porous separator having electrochemical stability and mechanical stability may be selected 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, which comprises 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 by the present application. 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 5:1, weighing sucrose and polyethylene oxide (PEO, with an average molecular weight of 600000) and uniformly mixing to obtain a carbon precursor;

s2, preheating: placing the carbon precursor in the step S1 into a kiln, introducing argon as a shielding gas, heating to 300 ℃ at a speed of 2 ℃/min, and naturally cooling to room temperature after heat preservation to obtain an intermediate;

s3, crushing the intermediate obtained in the step S2 to a particle size of about 6 mu m by adopting a ball milling method;

s4, carrying out impurity removal treatment on the intermediate crushed 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 containing 5% of hydrogen as a shielding gas, controlling the pressure of a hearth tower to be less than or equal to-2 kPa, then heating to T1 at a speed of less than or equal to 1 ℃/min, wherein T1 is 600 ℃, and preserving heat T1 and T1 is 3 h; then heating to T2 at a speed of less than or equal to 1 ℃/min, wherein T2 is 1150 ℃, and the heat preservation is carried out, wherein T2 is 6 h, and 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. Then toThe metal sodium sheet is a counter electrode, a Polyethylene (PE) film is used as a separation film, and the CR2430 button cell is assembled in a glove box protected by argon.

Detection of

And detecting parameters such as the exhaust gas quantity, 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 probe liquid (water and methylene dichloride), and detecting the performance of the sodium ion battery prepared by the carbon material.

(1) Carbon material parameter detection

The displacement of the carbon material was detected by a liquid probe method using water and methylene chloride as probe liquids, respectively. The carbon material was detected and calculated to have an air displacement A with respect to water of 12.56 mL/g and an air displacement B with respect to methylene chloride of 11.87 mL/g.

In addition, the true density of the carbon material was detected to be 1.54. 1.54 g/cm ³ The method comprises the steps of carrying out a first treatment on the surface of the The X-ray diffraction spectrum is shown in FIG. 7, wherein 2 theta value corresponding to 002 peak is 22 deg. to 24 deg., and the Raman spectrum is shown in FIG. 8, wherein 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 1.27. The volume particle diameter Dv50 of the carbon material was 5.3 μm, dv90 was 10.1 μm, and the specific surface area was 5.2. 5.2 cm ² /g。

(2) Low temperature capacity retention rate

The button cell was first discharged to 0V at a current density of 10mA/g at 25℃and then charged to 2.0V at a current density of 10mA/g, and the first charge capacity Q0 of the button cell was recorded. The capacity C0 at normal temperature Chu Nake of the material is Q0/M, wherein M is the use mass of the carbonaceous material.

The button cells prepared in each example and comparative example were first discharged to 0V at a current density of 10mA/g, and then charged to 2.0V at a current density of 10mA/g, and the first-turn charge capacity Q1 of the button cells was recorded. The low Wen Chuna gram capacity C1 of the material is Q1/M, wherein M is the use mass of the carbonaceous material.

The low-temperature capacity retention rate of the material is C1/C0 multiplied by 100 percent.

Examples 2 to 11 and comparative example 1

The same procedure as in example 1 was followed except for the procedure parameters in table 1 to prepare a carbon material and a sodium ion battery. The detection results of the prepared carbon material and sodium ion battery are recorded in table 2.

TABLE 1

TABLE 2

From the above experimental results, it is found that the battery can have better low-temperature performance when the ratio A/B of the carbon material to the amount of water discharged A to the amount of methylene chloride discharged B is 2 or less than that of comparative example 1. This is mainly because, when the ratio A/B of the carbon material to the exhaust gas amounts of the two probe liquids is less than or equal to 2, it is shown that the ratio of the narrow pores corresponding to the gas amounts is relatively low, so that the carbon material can maintain relatively high sodium ion mobility even under low temperature conditions, thereby reducing polarization and improving the low temperature performance of the battery.

From examples 1 to 11, it is understood that the carbon material has a wide range of values for the displacement A of water, and can significantly improve the low-temperature performance when A is not less than 0.1 and not more than mL/g and not more than 170 mL/g.

The present application is not limited to the above-mentioned embodiments, and any changes or substitutions that can be easily understood by those skilled in the art within the technical scope of the present application are intended to be included in 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

1. A carbon material, characterized in that the carbon material has a pore structure;

2. The carbon material of claim 1, wherein a/B has a value of 1.2 or less.

3. The carbon material of claim 1, wherein A is greater than or equal to 0.1 mL/g.

4. A carbon material according to claim 3, wherein a is 2 mL/g or more.

5. The carbon material according to any one of claims 1 to 4, wherein in an X-ray diffraction spectrum of the carbon material, a 2Θ 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.

6. The carbon material according to any one of claims 1 to 4, wherein the carbon material has a volume particle diameter Dv50 of 3 to 7 μm and a Dv90 of 9 to 18 μm.

7. The carbon material according to any one of claims 1 to 4, wherein the carbon material has a specific surface area of 0.1 to 50 m ² /g。

8. The method for producing a carbon material according to any one of claims 1 to 7, comprising: and carbonizing the carbon precursor to obtain the carbon material.

9. The method for producing a carbon material according to claim 8, wherein the carbonization treatment comprises: sequentially performing first heating and second heating on the carbon precursor; the first heating includes: heating to T1, and then carrying out first heat preservation, wherein the temperature of T1 is 300-800 ℃; the second heating includes: and (3) heating to T2, and then carrying out second heat preservation, wherein T2 is 1000-1700 ℃.

10. The method for producing a carbon material according to claim 8, wherein the carbonization treatment is preceded by the steps of: removing impurities from the carbon precursor; the impurity removal includes an acidic solution washing step and/or an alkaline solution washing step.

11. A negative electrode sheet, characterized in that the negative electrode sheet comprises the carbon material according to any one of claims 1 to 7, or the carbon material produced by the production method of the carbon material according to any one of claims 8 to 10.

12. A secondary battery comprising the negative electrode tab of claim 11.

13. An electric device, characterized in that the electric device comprises the secondary battery according to claim 12.