WO2024082308A1 - 碳质材料及其制备方法、以及含有其的二次电池和用电装置 - Google Patents

碳质材料及其制备方法、以及含有其的二次电池和用电装置 Download PDF

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WO2024082308A1
WO2024082308A1 PCT/CN2022/126836 CN2022126836W WO2024082308A1 WO 2024082308 A1 WO2024082308 A1 WO 2024082308A1 CN 2022126836 W CN2022126836 W CN 2022126836W WO 2024082308 A1 WO2024082308 A1 WO 2024082308A1
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carbonaceous material
water vapor
washing
optionally
temperature
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PCT/CN2022/126836
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English (en)
French (fr)
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马宇
张欣欣
陈晓霞
欧阳楚英
林文光
陈尚栋
成伟鸣
郑孝吉
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宁德时代新能源科技股份有限公司
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Priority to PCT/CN2022/126836 priority Critical patent/WO2024082308A1/zh
Publication of WO2024082308A1 publication Critical patent/WO2024082308A1/zh

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    • 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

Definitions

  • the present application belongs to the field of battery technology, and specifically relates to a carbonaceous material and a preparation method thereof, as well as a secondary battery and an electrical device containing the same.
  • secondary batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.
  • energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.
  • Graphite is the most commonly used negative electrode active material for secondary batteries, but its theoretical gram capacity is only 372mAh/g, and the room for improving energy density is very limited; at the same time, the interlayer spacing of graphite is small, and the improvement of rate performance is also limited.
  • hard carbon can realize the rapid embedding and extraction of active ions during the charging and discharging process of secondary batteries, so its development prospects are very broad.
  • the gram capacity and first coulomb efficiency of hard carbon are low, and the improvement of energy density, service life and rate performance of secondary batteries is limited.
  • the purpose of the present application is to provide a carbonaceous material and a preparation method thereof, as well as a secondary battery and an electrical device containing the same, wherein the carbonaceous material can take into account a higher gram capacity, a higher first coulombic efficiency and a higher structural stability, and can enable the secondary battery to have a high energy density, a long service life and good rate performance at the same time.
  • the carbonaceous materials provided in this application can take into account higher gram capacity, higher first coulombic efficiency and higher structural stability, and can make the secondary battery have high energy density, long service life and good rate performance at the same time.
  • the inventors of this application speculate that a possible reason is that when the water vapor adsorption rate v is between 0.015 and 0.050, the carbonaceous material of this application has high structural stability and a unique pore structure, which can facilitate the embedding, storage and extraction of active ions, and thus the carbonaceous material of this application can take into account higher gram capacity and first coulombic efficiency, and can make the secondary battery have high energy density, long service life and good rate performance at the same time.
  • 0.020 ⁇ v ⁇ 0.050 This helps to further improve the gram capacity, first coulombic efficiency and structural stability of the carbonaceous material, and further improve the energy density, service life and rate performance of the secondary battery.
  • the water vapor adsorption time t when the carbonaceous material adsorbs water vapor to reach equilibrium is 1h-12h, and can be optionally 4.5h-7h.
  • the water vapor adsorption time when the carbonaceous material adsorbs water vapor to reach equilibrium meets the above-mentioned specific range, it helps to further improve the gram capacity, first coulomb efficiency and structural stability of the carbonaceous material, thereby further improving the energy density, service life and rate performance of the secondary battery.
  • the true density ⁇ of the carbonaceous material is 1.0 g/cm 3 -2.2 g/cm 3 , and can be 1.3 g/cm 3 -1.7 g/cm 3 .
  • the true density of the carbonaceous material meets the above specific range, it is helpful to further improve the gram capacity and first coulombic efficiency of the carbonaceous material.
  • the carbonaceous material includes a plurality of nanopore structures.
  • the carbonaceous material includes a plurality of pore structures with a pore size of less than 10 nm.
  • I d /I g in the Raman spectrum of the carbonaceous material, is 1.0-1.3, optionally 1.05-1.15, I d represents the d peak intensity of the Raman shift in the range of 1350 ⁇ 50cm -1 , and I g represents the g peak intensity of the Raman shift in the range of 1580 ⁇ 50cm -1 .
  • the carbonaceous material has a higher gram capacity and a higher first coulomb efficiency, and also has good rate performance.
  • the interlayer spacing of the (002) crystal plane of the carbonaceous material is ⁇ 0.37 nm, and can be optionally 0.37 nm-0.42 nm.
  • the 2 ⁇ value corresponding to the (002) crystal plane peak is between 22° and 24°.
  • the volume particle size Dv50 of the carbonaceous material is 4 ⁇ m-6 ⁇ m.
  • the volume particle size Dv90 of the carbonaceous material is 8 ⁇ m-16 ⁇ m.
  • volume particle size Dv50 and/or Dv90 of the carbonaceous material is within an appropriate range, it is beneficial to improve the active ion and electron transport performance, thereby further improving the rate performance of the secondary battery.
  • the specific surface area of the carbonaceous material is 0.1m2 /g- 20m2 /g, optionally 1m2 /g- 20m2 /g.
  • the carbonaceous material can have higher gram capacity and first coulombic efficiency, and also have better rate performance.
  • the powder compaction density of the carbonaceous material under a force of 50000N is 0.90g/ cm3-1.05g / cm3 , and can be 0.92g/ cm3-1.02g / cm3 .
  • the compaction density of the negative electrode sheet can be increased, thereby increasing the energy density of the secondary battery.
  • the tap density of the carbonaceous material is 0.78 g/cm 3 -0.95 g/cm 3 , and can be 0.83 g/cm 3 -0.93 g/cm 3 .
  • the compaction density of the negative electrode sheet can be increased, thereby increasing the energy density of the secondary battery.
  • the second aspect of the present application provides a method for preparing a carbonaceous material, comprising the following steps: S10, providing a carbon source: the carbon source is a cellulose biomass material; S20, low-temperature pre-carbonization treatment: heating the carbon source to a first temperature T1 at a first heating rate under a protective gas atmosphere, and then heat-treating it for a first time t1 to obtain a first intermediate product; S30, high-temperature carbonization treatment: heating the obtained first intermediate product to a second temperature T2 at a second heating rate under a protective gas atmosphere, and then heat-treating it for a second time t2 to obtain a carbonaceous material, wherein the adsorption rate v of the carbonaceous material under constant temperature and humidity conditions of 25°C and 40%RH when water vapor is used for adsorption test satisfies 0.015 ⁇ v ⁇ 0.050, and the water vapor adsorption test is carried out under the following conditions: in a constant temperature and humidity box at 25°C
  • the carbonaceous material obtained by the preparation method provided by the present application can take into account a high gram capacity, a high first coulombic efficiency and a high structural stability, thereby enabling the secondary battery to have a high energy density, a long service life and good rate performance. And compared with the existing commercial hard carbon, the gram capacity, the first coulombic efficiency and the rate performance of the carbonaceous material obtained by the preparation method of the present application are significantly improved.
  • the cellulose content in the cellulose biomass material is greater than 0wt% and less than or equal to 100wt%, and the ash content is 0wt%-5wt%.
  • the cellulose content in the cellulose biomass material is greater than or equal to 20 wt% and less than 100 wt%, and the ash content is 0 wt%-5 wt%.
  • the cellulose content in the cellulose biomass material is greater than 0wt% and less than or equal to 100wt%, and the ash content is 0wt%-2wt%.
  • the cellulose content in the cellulose biomass material is greater than or equal to 20 wt% and less than 100 wt%, and the ash content is 0 wt%-2 wt%.
  • the hemicellulose content in the cellulose biomass material is 0wt%-70wt%, and can be optionally 0wt%-30wt%.
  • the lignin content in the cellulose biomass material is 0wt%-60wt%, and can be optionally 10wt%-60wt%.
  • the obtained carbonaceous material can have a higher gram capacity, a higher first coulombic efficiency and a higher structural stability, thereby further improving the energy density, service life and rate performance of the secondary battery.
  • the cellulosic biomass material includes one or more woody biomass materials, which may be selected from one or more of hardwood, softwood and nut shells, and may be selected from one or more of pine wood, bamboo and walnut shells.
  • the first heating rate is 1°C/min-10°C/min, and can be optionally 1°C/min-3°C/min.
  • the first temperature T1 is 150°C-1000°C, and can be optionally 300°C-700°C.
  • the first time t1 is 1 hour to 20 hours, and can be optionally 5 hours to 20 hours.
  • the second heating rate is ⁇ 10°C/min, and can be optionally 0.5°C/min-10°C/min.
  • the second temperature T2 is 1000°C-1600°C, and can be optionally 1200°C-1500°C.
  • the second time t2 is 1h-12h, and can be optionally 3h-10h.
  • t1+t2 is 10 h-30 h, which helps the obtained carbonaceous material to have a suitable water vapor adsorption rate, high capacity, high first coulombic efficiency and high structural stability.
  • the method further includes the steps of: crushing the first intermediate product obtained in S20, or washing and removing impurities from the first intermediate product obtained in S20, or first crushing and then washing and removing impurities from the first intermediate product obtained in S20 to obtain a first intermediate product with an ash content of ⁇ 0.01wt%, wherein the washing and removing impurities process includes at least an acidic solution washing step and an alkaline solution washing step.
  • This helps to further improve the gram capacity, first coulombic efficiency and structural stability of the carbonaceous material, and also helps to reduce the true density of the carbonaceous material.
  • the washing and impurity removal treatment process includes the following steps in sequence: acidic solution washing, water washing, alkaline solution washing, water washing and drying; or, the washing and impurity removal treatment process includes the following steps in sequence: alkaline solution washing, water washing, acidic solution washing, water washing and drying.
  • the H + concentration of the acidic solution is 0.1 mol/L-6 mol/L, and can be optionally 1 mol/L-6 mol/L.
  • the washing temperature of the acidic solution is 10°C-95°C, and can be optionally 30°C-95°C.
  • the washing time of the acidic solution is 1 h-24 h, and can be optionally 10 h-24 h.
  • the solute of the acidic solution includes one or more of hydrochloric acid, nitric acid, sulfuric acid and perchloric acid, and the solvent includes water.
  • the OH- concentration of the alkaline solution is 0.1 mol/L-6 mol/L, and can be optionally 1 mol/L-6 mol/L.
  • the washing temperature of the alkaline solution is 10°C-95°C, and can be optionally 30°C-95°C.
  • the washing time of the alkaline solution is 1 h-24 h, and can be optionally 10 h-24 h.
  • the solute of the alkaline solution includes NaOH, KOH or a combination thereof, and the solvent includes water.
  • a third aspect of the present application provides a secondary battery, which includes a negative electrode plate, wherein the negative electrode plate includes the carbonaceous material of the first aspect of the present application or the carbonaceous material prepared by the method of the second aspect of the present application.
  • a fourth aspect of the present application provides an electrical device, which includes the secondary battery of the third aspect of the present application.
  • the carbonaceous material provided by the present application can take into account higher gram capacity, higher first coulombic efficiency and higher structural stability, thereby enabling the secondary battery to have high energy density, long service life and good rate performance at the same time.
  • the electrical device of the present application includes the secondary battery provided by the present application, and thus has at least the same advantages as the secondary battery.
  • FIG. 1 is a schematic diagram of a battery cell according to an embodiment of the present application.
  • FIG. 2 is an exploded schematic diagram of an embodiment of a battery cell of the present application.
  • FIG. 3 is a schematic diagram of an embodiment of a battery module of the present application.
  • FIG. 4 is a schematic diagram of an embodiment of a battery pack of the present application.
  • FIG. 5 is an exploded schematic diagram of the embodiment of the battery pack shown in FIG. 4 .
  • FIG. 6 is a schematic diagram of an embodiment of an electric device including the secondary battery of the present application as a power source.
  • range disclosed in the present application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range.
  • the range defined in this way can be inclusive or exclusive of end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60-120 and 80-110 is listed for a specific parameter, it is understood that the range of 60-110 and 80-120 is also expected.
  • the numerical range "a-b" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers.
  • the numerical range "0-5" represents that all real numbers between "0-5" have been fully listed herein, and "0-5" is just the abbreviation of these numerical combinations.
  • a parameter is expressed as an integer ⁇ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • the method may further include step (c), which means that step (c) may be added to the method in any order.
  • the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.
  • the “include” and “comprising” mentioned in this application represent open-ended or closed-ended expressions.
  • the “include” and “comprising” may represent that other components not listed may also be included or only the listed components may be included or only the listed components may be included.
  • the term "or” is inclusive.
  • the phrase “A or B” means “A, B, or both A and B”. More specifically, any of the following conditions satisfies the condition "A or B”: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).
  • the values of the parameters mentioned in this application can be measured using various test methods commonly used in the art, for example, they can be measured according to the test methods given in this application.
  • active ions refers to ions that can be intercalated and extracted between the positive electrode and the negative electrode of a secondary battery, including but not limited to lithium ions, sodium ions, etc.
  • micropores refer to pores with a pore diameter of less than 2 nm
  • mesopores refer to pores with a pore diameter of 2 nm-50 nm
  • macropores refer to pores with a pore diameter of more than 50 nm.
  • micropore when the term “micropore” appears, it refers to pores with a pore diameter of less than 2 nm; when the term “mesopore” appears, it refers to pores with a pore diameter of 2nm-50nm; when the term “macroporous” appears, it refers to pores with a pore diameter of more than 50nm.
  • small mesopore refers to pores with a pore diameter of 2 nm to 10 nm
  • large mesopore refers to pores with a pore diameter greater than 10 nm and less than or equal to 50 nm.
  • capillary pores when used herein refers to micropores and/or small mesopores, ie pores with a pore diameter of ⁇ 10 nm.
  • hard carbon Compared with graphite, hard carbon has a larger interlayer spacing, which is conducive to the rapid embedding and extraction of active ions, so that secondary batteries have excellent low-temperature performance, power performance and safety performance.
  • hard carbon has unique advantages.
  • most of the commercialized hard carbons are low-capacity hard carbons with low capacity and first coulombic efficiency.
  • the capacity is usually between 200mAh/g and 280mAh/g, and the first coulombic efficiency is usually less than 75%, which severely limits its practical application.
  • the first aspect of the embodiment of the present application provides a carbonaceous material, which has a higher gram capacity, a higher first coulombic efficiency and a higher structural stability, and can make the secondary battery have a high energy density, a long service life and good rate performance.
  • the carbonaceous material provided in the present application satisfies an adsorption rate v of 0.015 ⁇ v ⁇ 0.050 when subjected to an adsorption test using water vapor under constant temperature and humidity conditions of 25°C and 40% RH.
  • the stacking thickness of the carbonaceous material is ⁇ 5mm.
  • the test time at this time is recorded, which is the water vapor adsorption time t.
  • the water vapor adsorption mass m2 (i.e., the mass increased when the carbonaceous material adsorbs water vapor to reach equilibrium) is obtained by subtracting the initial mass m1 of the carbonaceous material from the total mass of the carbonaceous material obtained at this time.
  • RH relative Humidity
  • the carbonaceous materials provided in this application can take into account higher gram capacity, higher first coulombic efficiency and higher structural stability, and can make the secondary battery have high energy density, long service life and good rate performance at the same time.
  • the inventors of this application speculate that a possible reason is that when the water vapor adsorption rate v is between 0.015 and 0.050, the carbonaceous material of this application has high structural stability and a unique pore structure, which can facilitate the embedding, storage and extraction of active ions, and thus the carbonaceous material of this application can take into account higher gram capacity and first coulombic efficiency, and can make the secondary battery have high energy density, long service life and good rate performance at the same time.
  • the inventors of the present application discovered that under the constant temperature and humidity conditions of 25°C and 40% RH, water vapor will preferentially adsorb into the capillary structure (i.e., microporous structure and/or small mesoporous structure) of the carbonaceous material, and usually will not enter the large mesoporous structure and/or macroporous structure of the carbonaceous material. Therefore, the water vapor adsorption rate v under the constant temperature and humidity conditions of 25°C and 40% RH can intuitively reflect the content of sites suitable for active ion storage in the carbonaceous material.
  • the carbonaceous material contains very few capillary structures, and the pore structure is mostly large mesoporous structure and/or macroporous structure. Therefore, the structural stability of the carbonaceous material is poor and the space contained inside that can accommodate active ions is very small, which is not suitable for the storage of active ions, and thus the gram capacity of the carbonaceous material is still relatively low; in addition, since the pore structure is mostly large mesoporous structure and/or macroporous structure, this also leads to an increase in the proportion of electrolyte infiltration area inside the carbonaceous material, an increase in the consumption of active ions during the formation of the solid electrolyte interface membrane (hereinafter referred to as SEI membrane), an increase in the first irreversible capacity loss, and thus the gram capacity and first coulombic efficiency of the carbonaceous material are both relatively low.
  • SEI membrane solid electrolyte interface membrane
  • the specific surface area of the carbonaceous material is relatively high, which leads to an increase in the consumption of active ions during the formation of the SEI film, an increase in the first irreversible capacity loss, and a decrease in the first coulombic efficiency.
  • the carbonaceous material has a strong water absorption capacity.
  • some water molecules will be firmly combined with the functional groups (such as oxygen-containing functional groups) on the surface of the carbonaceous material by chemical bonds, so that the water molecules are not easy to remove, which will block the capillary structure of the carbonaceous material and hinder the embedding and removal of active ions.
  • the water molecules adsorbed on the surface of the carbonaceous material may also react with the electrolyte, which will also lead to a decrease in the gram capacity and the first coulombic efficiency of the carbonaceous material.
  • v may be 0.016, 0.018, 0.020, 0.022, 0.024, 0.026, 0.028, 0.030, 0.032, 0.034, 0.036, 0.038, 0.040, 0.042, 0.044, 0.046, 0.048, 0.050 or any value within the above range, optionally, 0.018 ⁇ v ⁇ 0.050, 0.020 ⁇ v ⁇ 0.050. This helps to further improve the gram capacity, first coulombic efficiency and structural stability of the carbonaceous material, and further improve the energy density, service life and rate performance of the secondary battery.
  • the water vapor adsorption time t when the carbonaceous material adsorbs water vapor to reach equilibrium is 1h-12h.
  • the water vapor adsorption time t when the carbonaceous material adsorbs water vapor to reach equilibrium is 3h-12h, 4h-12h, 4h-9h, 4.5h-7h.
  • the carbonaceous material contains more capillary pore structures.
  • the skeleton structure of the carbonaceous material is relatively fragile and easily collapses to form larger pores, which in turn leads to an increase in the proportion of the electrolyte infiltration area inside the carbonaceous material, an increase in the first irreversible capacity loss, and a decrease in the first coulombic efficiency;
  • the carbonaceous material contains fewer capillary pore structures, which are not suitable for the embedding, storage and removal of active ions, which will also lead to a decrease in the gram capacity and first coulombic efficiency of the carbonaceous material.
  • the carbonaceous material comprises a plurality of nanopore structures.
  • the carbonaceous material comprises a plurality of pore structures with a pore size below 10 nm.
  • the carbonaceous material may further comprise one or more pore structures with a pore size greater than 10 nm.
  • the true density ⁇ of the carbonaceous material is 1.0 g/cm 3 -2.2 g/cm 3 , optionally 1.3 g/cm 3 -2.0 g/cm 3 , 1.3 g/cm 3 -1.7 g/cm 3 , 1.3 g/cm 3 -1.65 g/cm 3 , 1.3 g/cm 3 -1.6 g/cm 3 , 1.3 g/cm 3 -1.55 g/cm 3 .
  • the capillary pore structure of the carbonaceous material is rich and the closed-pore effect is good.
  • the space for the calibration liquid (such as n-butanol) to enter is less than the actual pore space of the carbonaceous material, and these pore structures that are not entered can store active ions.
  • the electrolyte is not easy to enter the interior of the carbonaceous material particles, and the consumption of active ions during SEI film formation is reduced; in addition, the true density of the carbonaceous material should not be too low. At this time, the active ions may not be easily embedded due to the good closed-pore effect of the carbonaceous material.
  • the calibration liquid such as n-butanol
  • the closed-pore effect of the carbonaceous material is poor, the large mesoporous structure and/or the macroporous structure are rich, which causes the capillary pore structure to be easily exposed to the electrolyte, resulting in a reduction in the storage space for active ions, and then the gram capacity and the first coulomb efficiency of the carbonaceous material are reduced.
  • the true density of carbonaceous materials is a well-known meaning in the art and can be measured using instruments and methods known in the art.
  • the Archimedean immersion volume displacement method can be used for testing, and the calibration liquid can be n-butanol.
  • the testing instrument can be a powder true density meter.
  • the carbonaceous material may have a regular or irregular morphology.
  • the carbonaceous material may have an irregular multi-angle morphology.
  • the C element content in the carbonaceous material may be 95 wt %-98 wt %.
  • the content of O element in the carbonaceous material may be 1 wt %-5 wt %.
  • the H content in the carbonaceous material may be less than 0.4 wt %.
  • the N content in the carbonaceous material may be ⁇ 2 wt %.
  • the total content of C, O, H and N elements in the carbonaceous material may be 99 wt % to 99.5 wt %.
  • the carbonaceous material contains less impurity elements, and the impurity elements mainly include S, K, Ca, and Fe.
  • the S content may be ⁇ 0.0021wt%
  • the K content may be ⁇ 0.0019wt%
  • the Ca content may be ⁇ 0.0011wt%
  • the Fe content may be ⁇ 0.0010wt%.
  • I d /I g in the Raman spectrum of the carbonaceous material, is 1.0-1.3, I d represents the d peak intensity in the Raman shift range of 1350 ⁇ 50cm -1 , and I g represents the g peak intensity in the Raman shift range of 1580 ⁇ 50cm -1 .
  • I d /I g can be 1.0, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3 or any range thereof.
  • I d /I g can be 1.05-1.15.
  • the Raman spectrum of the carbonaceous material can be tested using a Raman spectrometer. During the test, the d peak intensity and g peak intensity of 100 points are obtained, and the I d /I g of the 100 points are calculated. The maximum and minimum 30 I d /I g are removed, and the average value of the remaining 40 I d /I g is used as the I d /I g of the carbonaceous material.
  • the test instrument can be a Horiba LabRAM HR800 Raman spectrometer. The test conditions can be: excitation wavelength 532nm, grating 600 lines, objective lens 50 times, integration time 10s, cumulative number of times 3 times, surface scan.
  • the d peak is generated from the carbon atom lattice defect, and the g peak is generated from the in-plane vibration of the sp2 carbon atom.
  • the d peak intensity is related to the number of carbonaceous material structural defects, and the g peak intensity is related to the number of graphite crystallites in the carbonaceous material structure. Therefore, I d /I g can characterize the order of the carbonaceous material structure. The smaller I d /I g is , the higher the order of the carbonaceous material structure, the higher the integrity of the carbon plane, and the first coulombic efficiency of the carbonaceous material increases, but the gram capacity becomes lower and the rate performance becomes worse.
  • the carbonaceous material of the present application satisfies I d /I g of 1.0-1.3. At this time, the order of the carbonaceous material structure is moderate, so that the carbonaceous material has a higher gram capacity and a higher first coulombic efficiency, and also has good rate performance.
  • the interlayer spacing of the (002) crystal plane of the carbonaceous material is ⁇ 0.37 nm, and can be optionally 0.37 nm-0.42 nm.
  • the 2 ⁇ value corresponding to the (002) crystal plane peak is between 22° and 24°.
  • the interlayer spacing of the (002) crystal plane of the carbonaceous material can be tested by using an X-ray diffractometer with reference to JIS K 0131-1996 and JB/T 4220-2011.
  • the testing instrument can be a Bruker D8 Discover X-ray diffractometer.
  • the volume particle size Dv50 of the carbonaceous material may be 4 ⁇ m-6 ⁇ m.
  • the volume particle size Dv90 of the carbonaceous material may be 8 ⁇ m-16 ⁇ m.
  • the carbonaceous material simultaneously satisfies a volume particle size Dv50 of 4 ⁇ m to 6 ⁇ m and a volume particle size Dv90 of 8 ⁇ m to 16 ⁇ m.
  • volume particle size Dv50 and/or Dv90 of the carbonaceous material is within an appropriate range, it is beneficial to improve the active ion and electron transport performance, thereby further improving the rate performance of the secondary battery.
  • volume particle size Dv50 and Dv90 of the carbonaceous material are well-known in the art, which means the particle size corresponding to the cumulative volume distribution percentage of the material reaching 50% and 90%, respectively, and can be measured using instruments and methods known in the art. For example, it can be conveniently measured using a laser particle size analyzer with reference to GB/T 19077-2016 particle size distribution laser diffraction method.
  • the test instrument can be the Mastersizer 2000E laser particle size analyzer of Malvern Instruments Ltd., UK.
  • the specific surface area of the carbonaceous material is 0.1m 2 /g-20m 2 /g, and can be 1m 2 /g-20m 2 /g.
  • the carbonaceous material can have a higher gram capacity and first coulombic efficiency at the same time, and can also have better rate performance.
  • the carbonaceous material and the binder can also have a strong bonding force, thereby improving the cohesion and bonding force of the negative electrode sheet, reducing the volume expansion of the negative electrode sheet during the cycle, and making the secondary battery have better cycle performance.
  • the specific surface area of carbonaceous materials has a well-known meaning in the art and can be measured by instruments and methods known in the art. For example, it can be tested by nitrogen adsorption specific surface area analysis test method with reference to GB/T 19587-2017 and calculated by BET (Brunauer Emmett Teller) method, wherein the nitrogen adsorption specific surface area analysis test can be measured by ASAP 3020 surface area and pore size analyzer of Micromeritics, USA.
  • the powder compaction density of the carbonaceous material under a force of 50000N is 0.90g/ cm3-1.05g / cm3 , and can be 0.92g/ cm3-1.02g / cm3 .
  • the compaction density of the negative electrode sheet can be increased, thereby increasing the energy density of the secondary battery.
  • the powder compaction density of the carbonaceous material has a meaning well known in the art and can be measured by instruments and methods known in the art. For example, it can be measured by an electronic pressure testing machine (for example, UTM7305 model) with reference to standard GB/T24533-2009.
  • An exemplary test method is as follows: weigh 1g of carbonaceous material powder, add it to a mold with a bottom area of 1.327cm2 , pressurize it to 5000kg (equivalent to 50000N), maintain the pressure for 30s, then release the pressure, maintain for 10s, and then record and calculate the powder compaction density of the carbonaceous material under a force of 50000N.
  • the tap density of the carbonaceous material is 0.78 g/cm 3 -0.95 g/cm 3 , and can be 0.83 g/cm 3 -0.93 g/cm 3 .
  • the compaction density of the negative electrode sheet can be increased, thereby increasing the energy density of the secondary battery.
  • the tap density of carbonaceous materials has a well-known meaning in the art and can be measured using instruments and methods known in the art. For example, it can be measured using a powder tap density tester with reference to GB/T 5162-2006.
  • the test instrument can be Dandong Better BT-301.
  • the second aspect of the embodiment of the present application provides a method for preparing a carbonaceous material, comprising the following steps: S10, providing a carbon source: the carbon source is a cellulose biomass material; S20, low-temperature pre-carbonization treatment: heating the carbon source to a first temperature T1 at a first heating rate under a protective gas atmosphere, and then keeping it warm for a first time t1 to obtain a first intermediate product; S30, high-temperature carbonization treatment: heating the obtained first intermediate product to a second temperature T2 at a second heating rate under a protective gas atmosphere, and then keeping it warm for a second time t2 to obtain a carbonaceous material, wherein the adsorption rate v of the carbonaceous material under constant temperature and humidity conditions of 25°C and 40% RH when adsorbed using water vapor satisfies 0.015 ⁇ v ⁇ 0.050.
  • the present application uses cellulose biomass materials as carbon sources to prepare carbonaceous materials.
  • Cellulose is a chain macromolecular organic substance with high crystallinity in biomass materials. On the one hand, it has high thermal stability and a wide range of adjustable parameters for pyrolysis process. On the other hand, the pore structure formed by chain macromolecular organic substances in the process of converting into carbonaceous materials is highly controllable, which can make it have a suitable water vapor adsorption rate and also help to improve the platform capacity.
  • the carbon source does not use cellulose biomass materials or the biomass materials used do not contain cellulose, the controllability of the pore structure of the carbonaceous material prepared therefrom is poor, and the content of the capillary pore structure is small, which is manifested as a too small water vapor adsorption rate.
  • the cellulose content in the cellulose biomass material may be greater than 0wt% and less than or equal to 100wt%, and may be selected as 10wt%-100wt%, 20wt%-100wt%, 30wt%-100wt%, and 40wt%-100wt%. This is conducive to increasing the controllability of the pore structure of the carbonaceous material and making it have a suitable water vapor adsorption rate.
  • the preparation process of carbonaceous materials includes at least a low-temperature pre-carbonization treatment process and a high-temperature carbonization treatment process.
  • Low-temperature pre-carbonization treatment can regulate the structural characteristics and surface characteristics of the carbon skeleton, and appropriately improve the carbon yield; at the same time, it can reduce the toughness of cellulose biomass materials, which is helpful for subsequent crushing and washing and impurity removal.
  • High-temperature carbonization treatment can cause a closed-pore effect on the biochar obtained by low-temperature pre-carbonization treatment, thereby reducing the contact area between the carbonaceous material and the electrolyte, that is, reducing the consumption of active ions during SEI film formation, and improving the first coulomb efficiency of the carbonaceous material; high-temperature carbonization treatment can also make the biochar obtained by low-temperature pre-carbonization treatment aromatic ring, thereby improving the order and conductivity of the carbonaceous material, while removing the excess O and H elements on the carbon skeleton structure, and helping to form an ordered pseudographite microcrystalline structure.
  • the carbonaceous material obtained by the preparation method provided by the present application can take into account a higher gram capacity, a higher first coulombic efficiency and a higher structural stability, thereby enabling the secondary battery to have a high energy density, a long service life and good rate performance. And compared with the existing commercial hard carbon, the gram capacity, the first coulombic efficiency and the rate performance of the carbonaceous material obtained by the preparation method of the present application are significantly improved.
  • Ash will not only produce catalytic reactions during the low-temperature pre-carbonization process, consume the C element content, and reduce the active ion storage sites, but also increase the complexity and production cost of the washing and impurity removal process; and, in the subsequent high-temperature carbonization process, the metal impurities in the ash will be reduced to metal elements and then agglomerated.
  • the carbon skeleton structure When metal elements agglomerate, the carbon skeleton structure will collapse, especially the collapse of the capillary structure, which will lead to a reduction in the storage space of active ions in the obtained carbonaceous material and a decrease in capacity, which is manifested as a too low adsorption rate for water vapor; at the same time, metal impurities also have catalytic activity, which will lead to the aggravation of the decomposition of the carbon skeleton structure during the cracking process, so that the pore structure tends to form a large-sized mesoporous structure and/or a large-porous structure, thereby resulting in poor stability of the carbon skeleton structure and an increase in the proportion of the electrolyte infiltration area inside the obtained carbonaceous material, an increase in the consumption of active ions during the formation of the SEI film, and an increase in the first irreversible capacity loss.
  • the ash content in the cellulose biomass material may be 0wt%-5wt%, optionally 0wt%-4wt%, 0wt%-3wt%, 0wt%-2wt%, 0wt%-1wt%. This can reduce the adverse effects of impurities on carbonaceous materials, improve the gram capacity, first coulomb efficiency and structural stability of carbonaceous materials, and also help reduce the true density of carbonaceous materials.
  • the cellulose content in the cellulose biomass material is greater than 0 wt% and less than or equal to 100 wt%, and the ash content is 0 wt%-5 wt%.
  • Cellulosic biomass materials can also contain hemicellulose.
  • Hemicellulose is an amorphous polymer with a relatively small molecular weight in biomass materials. It is easy to decompose into small molecular sugars and volatilize during low-temperature pre-carbonization treatment, which is conducive to the formation of a pore structure; but its content should not be too high. When it is higher than 70wt%, it will cause poor stability of the carbon skeleton structure, poor closed-cell effect, increase in the content of large mesoporous structure and/or macroporous structure in the carbonaceous material, increase in the proportion of electrolyte infiltration area inside the carbonaceous material, increase in the first irreversible capacity loss, and reduce the first coulombic efficiency.
  • the hemicellulose content in the cellulose biomass material may be 0wt%-70wt%, optionally 0wt%-60wt%, 0wt%-50wt%, 0wt%-40wt%, 0wt%-30wt%, 0wt%-20wt%.
  • Cellulosic biomass materials may also contain lignin.
  • Lignin is a macromolecular organic substance containing benzene rings and having a high degree of crosslinking. It helps to form carbon hexagonal rings during low-temperature pre-carbonization treatment, helps to improve the stability of the carbon skeleton structure, and is beneficial to improving the rate performance of secondary batteries; but the controllability of the pore structure formed by it is poor, so when its content is too high, for example, greater than 60wt%, it will cause the capacity of the obtained carbonaceous material platform to be limited.
  • the lignin content in the cellulosic biomass material is 0wt%-60wt%, and can be optionally 5wt%-60wt%, 10wt%-60wt%, 10wt%-50wt%, and 15wt%-50wt%.
  • the cellulose content in the cellulose biomass material is greater than 0wt% and less than or equal to 100wt%, the hemicellulose content is 0wt%-70wt%, the lignin content is 0wt%-60wt%, and the ash content is 0wt%-5wt%.
  • the cellulose content in the cellulose biomass material is greater than or equal to 20wt% and less than 100wt%, the hemicellulose content is 0wt%-30wt%, the lignin content is 10wt%-60wt%, and the ash content is 0wt%-2wt%.
  • the cellulose content in the cellulose biomass material may be 100wt%, that is, the cellulose biomass material may directly use cellulose as a carbon source. This helps the obtained carbonaceous material to have a high capacity, but the stability of the carbon skeleton structure formed during the preparation process is slightly reduced, thereby causing a slight decrease in the effect of improving the rate performance of the secondary battery.
  • the cellulose content can be detected by acid hydrolysis anthrone colorimetry.
  • Cellulose can be hydrolyzed into ⁇ -D-glucose under acidic conditions, and ⁇ -D-glucose is dehydrated in a strong acid environment to generate ⁇ -furfural compounds, which are dehydrated and condensed with anthrone to generate blue-green furfural derivatives.
  • the product has a characteristic absorption peak at 620nm, and the cellulose content can be quantitatively detected by the change in absorbance.
  • the acid can be sulfuric acid.
  • the hemicellulose content can be detected by DNS colorimetry. Hemicellulose is converted into reducing sugar after acid treatment, and the reducing sugar reacts with DNS to generate a reddish-brown substance. The product has a characteristic absorption peak at 540nm, and the hemicellulose content can be quantitatively detected by the change in absorbance.
  • the lignin content can be detected by acetylation method. After the phenolic hydroxyl groups in lignin are acetylated, acetyl lignin is generated, and the product has a characteristic absorption peak at 280nm. The content of lignin can be quantitatively detected by the change of the absorbance value.
  • the ash content can be determined in accordance with GB/T 28731-2012.
  • the cellulosic biomass material includes one or more woody biomass materials that meet the above requirements of the present application, and can optionally include one or more of hardwood, softwood, and nut shells, for example, it can include one or more of pine wood, bamboo, and walnut shells.
  • the preparation method further comprises the step of: pre-treating the cellulose biomass material.
  • the pre-treatment process may include crushing, washing and drying steps. Crushing the cellulose biomass material is helpful for loading. Washing can remove impurities that are obviously attached to the surface of the cellulose biomass material to prevent them from affecting the subsequent low-temperature pre-carbonization treatment process. Drying can remove moisture attached to the surface of the cellulose biomass material and part of the body moisture, thereby reducing the impact of moisture on the subsequent low-temperature pre-carbonization treatment process.
  • the first heating rate is ⁇ 10°C/min, and can be selected from 1°C/min-10°C/min, 1°C/min-5°C/min, and 1°C/min-3°C/min.
  • the first heating rate is within a suitable range, it helps the obtained carbonaceous material to have a suitable water vapor adsorption rate, high capacity, high first coulombic efficiency, and high structural stability.
  • the first heating rate is too high, the controllability of the pore structure of the prepared carbonaceous material is poor, the content of the capillary pore structure is small, and the water vapor adsorption rate is low.
  • the first temperature T1 is 150°C-1000°C, for example, the first temperature T1 can be 200°C, 300°C, 400°C, 500°C, 600°C, 700°C, 800°C, 900°C, 1000°C or any range thereof.
  • the first temperature T1 is 200°C-900°C, 300°C-700°C, 300°C-600°C.
  • the pore structure As the first temperature increases, the pore structure is formed more completely and the content of capillary pore structure increases; but when the first temperature is too high, the volatilization rate of the volatile matter is accelerated, the size of the formed pore structure becomes larger, the stability of the carbon skeleton structure becomes worse, and it will also lead to poor closed-cell effect during high-temperature carbonization treatment, increase in the content of large mesoporous structure and/or macroporous structure in the carbonaceous material, increase in the proportion of electrolyte infiltration area inside the carbonaceous material, increase in the first irreversible capacity loss, decrease in the first coulombic efficiency, and at the same time, decrease in the content of capillary pore structure in the carbonaceous material, which is manifested as a lower water vapor adsorption rate.
  • the first time t1 is 1h-20h, and can be 5h-20h.
  • Those skilled in the art can select a suitable first time within the above range according to the first temperature and the first heating rate. For example, when the first temperature is high and/or the first heating rate is low, the first time can be appropriately shortened.
  • the second heating rate is ⁇ 10°C/min, and may be 0.5°C/min-10°C/min.
  • the present application is not limited thereto, and the second heating rate may be adjusted according to actual conditions.
  • the second temperature T2 is 1000°C-1600°C, for example, 1000°C, 1050°C, 1100°C, 1150°C, 1200°C, 1250°C, 1300°C, 1350°C, 1400°C, 1450°C, 1500°C, 1550°C, 1600°C or any range thereof.
  • the second temperature T2 is 1200°C-1500°C.
  • the second temperature is within a suitable range, it is helpful for the obtained carbonaceous material to have a suitable water vapor adsorption rate, high capacity and high first coulombic efficiency.
  • the carbonaceous material When the second temperature is low, there are more oxygen-containing functional groups on the surface of the carbonaceous material, and these oxygen-containing functional groups have better hydrophilicity, so the carbonaceous material will show a fast water vapor adsorption rate and short adsorption time, but at this time the pore structure has a poor closed-cell effect, and there are more large mesoporous structures and/or macroporous structures in the carbonaceous material, which leads to an increase in the proportion of electrolyte infiltration areas inside the carbonaceous material, an increase in the first irreversible capacity loss, and a decrease in the first coulombic efficiency.
  • the closed-cell effect of the pore structure becomes better, thereby reducing the consumption of active ions during SEI film formation, and the active ion storage sites of the carbonaceous material increase, thereby increasing its capacity and first coulombic efficiency; but when the second temperature is too high, the microstructure of the carbonaceous material will undergo a qualitative change, which is not conducive to the storage of active ions, and is manifested as a decrease in the water vapor adsorption rate.
  • the second time t2 is 1h-12h, and can be 3h-10h.
  • Those skilled in the art can select a suitable first time within the above range according to the second temperature and the second heating rate. For example, when the second temperature is high and/or the second heating rate is low, the second time can be appropriately shortened.
  • t1+t2 is 10 h to 30 h, which helps the obtained carbonaceous material to have a suitable water vapor adsorption rate, high capacity, high first coulombic efficiency and high structural stability.
  • the crushing process can reduce the particle size of the first intermediate product, thereby helping to obtain a carbonaceous material of a desired size.
  • the volume particle size Dv50 of the crushed particles is 4 ⁇ m-6 ⁇ m.
  • the volume particle size Dv90 of the crushed particles is 8 ⁇ m-16 ⁇ m.
  • the volume particle size Dv50 of the crushed particles is 4 ⁇ m-6 ⁇ m and the volume particle size Dv90 is 8 ⁇ m-16 ⁇ m.
  • the crushing step can also be omitted.
  • the washing and impurity removal treatment can remove inorganic impurities and water-soluble impurities in the first intermediate product, and avoid the metal impurities being reduced to metal elements and then agglomerating during the subsequent high-temperature carbonization treatment. Because the agglomeration of metal elements will cause the collapse of the carbon skeleton structure, especially the collapse of the capillary structure, which will lead to a reduction in the storage space of active ions in the obtained carbonaceous material and a decrease in capacity; at the same time, the metal impurities also have catalytic activity, which will lead to the aggravation of the decomposition of the carbon skeleton structure during the cracking process, so that the pore structure tends to form a large-sized large mesoporous structure and/or a large-porous structure, thereby increasing the proportion of the electrolyte infiltration area inside the obtained carbonaceous material, increasing the consumption of active ions during SEI film formation, increasing the first irreversible capacity loss, and reducing the first coulomb efficiency.
  • the washing and impurity removal treatment process includes at least an acidic solution washing step and an alkaline solution washing step.
  • the acidic solution is mainly used to remove metal impurities in the first intermediate product
  • the alkaline solution is mainly used to remove Si-containing impurities in the first intermediate product that cannot react with acid, thereby fully ensuring the removal of impurities, reducing the adverse effects of impurities on carbonaceous materials, and improving the gram capacity and first coulomb efficiency of carbonaceous materials.
  • the crushing treatment needs to be performed before the washing and impurity removal treatment, so that during the subsequent washing and impurity removal, the first intermediate product can expose as much surface as possible, so that the particles and the washing liquid can fully contact and improve the washing and impurity removal effect. If the crushing treatment is performed after the washing and impurity removal treatment, some large pieces of raw materials will basically remain in their original appearance after pyrolysis, and the washing liquid may not be able to enter the bulk phase of the large particles, and then the impurities deeply wrapped in the bulk phase of the large particles cannot be removed, resulting in an insignificant washing and impurity removal effect.
  • Crushing can adopt a process known in the art suitable for crushing in the preparation of carbonaceous materials.
  • the crushing can include ball milling or air flow milling.
  • the washing and impurity removal treatment process comprises the following steps in sequence: acid solution washing, water washing, alkaline solution washing, water washing and drying; or, the washing and impurity removal treatment process comprises the following steps in sequence: alkaline solution washing, water washing, acid solution washing, water washing and drying.
  • Deionized water can be used for water washing, and the number of water washings can be one or more times until the pH of the filtrate is neutral (i.e., the pH is 7 ⁇ 0.5), and the water washing step is considered to be completed.
  • Drying can be forced air drying or vacuum drying until the mass change rate of the material after an interval of 2h is ⁇ 0.1wt%, and the drying step is considered to be completed.
  • the present application has no particular restrictions on parameters such as the solute type, concentration, washing temperature, and washing time of the acidic solution and the alkaline solution, as long as the impurities can be fully removed.
  • the H + concentration of the acidic solution is 0.1 mol/L-6 moL/L, optionally 1 mol/L-6 moL/L.
  • the washing temperature of the acidic solution is 10°C-95°C, optionally 30°C-95°C.
  • the washing time of the acidic solution is 1 h-24 h, optionally 10 h-24 h.
  • the solute of the acidic solution includes one or more of hydrochloric acid, nitric acid, sulfuric acid and perchloric acid, and the solvent includes water.
  • the OH- concentration of the alkaline solution is 0.1 mol/L-6 mol/L, and can be optionally 1 mol/L-6 mol/L.
  • the washing temperature of the alkaline solution is 10°C-95°C, optionally 30°C-95°C.
  • the washing time of the alkaline solution is 1 h-24 h, optionally 10 h-24 h.
  • the solute of the alkaline solution includes NaOH, KOH or a combination thereof, and the solvent includes water.
  • the washing and impurity removal step can be omitted.
  • washing and impurity removal treatment is required to ensure that the ash content in the material before high-temperature carbonization treatment is ⁇ 0.01wt%.
  • the present application has no particular limitation on the type of protective gas atmosphere in S20 and S30.
  • the protective gas includes nitrogen, an inert gas or a combination thereof.
  • the inert atmosphere includes argon, helium or a combination thereof.
  • the volume concentration of the gas may be above 99.9%.
  • the preparation method further includes: S40, crushing: crushing the carbonaceous material obtained in S30, at which time the carbonaceous material agglomerated during the preparation process can be crushed to meet the required particle size, so as to facilitate the preparation of negative electrode slurry and negative electrode sheet.
  • this step can be omitted.
  • the preparation method includes the following steps: providing a carbon source: the carbon source is a cellulose biomass material, the cellulose content in the cellulose biomass material is greater than 0wt% and less than or equal to 100wt%, and the ash content is 0wt%-5wt%; low-temperature pre-carbonization treatment: the carbon source is heated to 150°C-1000°C, optionally 300°C-700°C, under a protective gas atmosphere at a rate of ⁇ 10°C/min, and then heat-treated for 1h-20h, optionally 5h -20h, to obtain the first intermediate product; high temperature carbonization treatment: the first intermediate product obtained is heated to 1000°C-1600°C, optionally 1200°C-1500°C, at a rate of ⁇ 10°C/min under a protective gas atmosphere, and then heat-treated for 1h-12h, optionally 3h-10h, to obtain a carbonaceous material, wherein the carbonaceous material is subjected to a constant temperature and humidity condition of 25°
  • the preparation method comprises the following steps: providing a carbon source: the carbon source is a cellulosic biomass material, the cellulose content in the cellulosic biomass material is greater than 0wt% and less than or equal to 100wt%, and the ash content is 0wt%-5wt%; low-temperature pre-carbonization treatment: heating the carbon source to 150°C-1000°C, optionally 300°C-700°C, at a rate of ⁇ 10°C/min under a protective gas atmosphere, and then heat-treating for 1h-20h, optionally 5h-20h, to obtain a first intermediate product; high-temperature carbonization treatment: After the obtained first intermediate product is crushed to a volume particle size Dv50 of 4 ⁇ m-6 ⁇ m and/or a volume particle size Dv90 of 8 ⁇ m-16 ⁇ m, it is heated to 1000°C-1600°C, optionally 1200°C-1500°C, and then heat-treated for 1h-12h, optionally 3h-10h, at a
  • the preparation method includes the following steps: providing a carbon source: the carbon source is a cellulose biomass material, the cellulose content in the cellulose biomass material is greater than 0wt% and less than or equal to 100wt%, and the ash content is 0wt%-5wt%; low-temperature pre-carbonization treatment: heating the carbon source to 150°C-1000°C, optionally 300°C-700°C, at a rate of ⁇ 10°C/min under a protective gas atmosphere, and then heat-treating for 1h-20h, optionally 5h-20h, to obtain a first intermediate product; high-temperature carbonization treatment: crushing the obtained first intermediate product to a volume of After the particle size Dv50 is 4 ⁇ m-6 ⁇ m and/or the volume particle size Dv90 is 8 ⁇ m-16 ⁇ m, it is washed with an acid solution, washed with water, washed with an alkaline solution, washed with water and dried in sequence, and then heated to 1000°C-1600°C, optionally
  • the preparation method of the second aspect of the embodiment of the present application can prepare the carbonaceous material of any embodiment of the first aspect of the embodiment of the present application.
  • the preparation method of the carbonaceous material provided in the present application is simple in process and suitable for commercial production.
  • the preparation method of the carbonaceous material provided in the present application does not require the addition of an additional conductive agent or other additives, so that the carbonaceous material obtained by the preparation method provided in the present application has a lower heteroatom content.
  • a third aspect of the embodiments of the present application provides a secondary battery.
  • the secondary battery mentioned in the embodiments or implementations of the present application refers to a single physical module including one or more battery cells to provide higher voltage and capacity.
  • the secondary battery mentioned in the present application may include a battery cell, a battery module or a battery pack, etc.
  • a battery cell is the smallest unit that makes up a secondary battery, which can realize the function of charging and discharging alone.
  • the present application has no particular restrictions on the shape of the battery cell, which can be cylindrical, square or any other shape.
  • Figure 1 is a battery cell 5 of a square structure as an example.
  • the battery cell includes an electrode assembly and an electrolyte, and the battery cell may further include an outer package.
  • the outer package may be used to encapsulate the electrode assembly and the electrolyte.
  • the outer package may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer package may also be a soft package, such as a bag-type soft package.
  • the material of the soft package may be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT) and polybutylene succinate (PBS).
  • the electrode assembly usually includes a positive electrode sheet, a negative electrode sheet, etc.
  • active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet, and the electrolyte plays a role in conducting active ions between the positive electrode sheet and the negative electrode sheet.
  • the electrode assembly can be made by a winding process and/or a lamination process.
  • the outer package may include a shell 51 and a cover plate 53.
  • the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity.
  • the shell 51 has an opening connected to the receiving cavity, and the cover plate 53 is used to cover the opening to close the receiving cavity.
  • the electrode assembly 52 is encapsulated in the receiving cavity.
  • the number of electrode assemblies 52 contained in the battery cell 5 can be one or more, which can be adjusted according to demand.
  • battery cells can be assembled into a battery module, and the number of battery cells contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.
  • FIG. 3 is a schematic diagram of a battery module 4 as an example. As shown in FIG. 3, in the battery module 4, multiple battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, they can also be arranged in any other manner. The multiple battery cells 5 can be further fixed by fasteners.
  • the battery module 4 may further include a housing having a receiving space, and the plurality of battery cells 5 are received in the receiving space.
  • the battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.
  • Figures 4 and 5 are schematic diagrams of a battery pack 1 as an example.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 is used to cover the lower box body 3 and form a closed space for accommodating the battery modules 4.
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • the negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector.
  • the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode film layer comprises the carbonaceous material of the first aspect of the embodiment of the present application or the carbonaceous material prepared by the method described in the second aspect of the embodiment of the present application, thereby enabling the secondary battery to have high energy density, long service life and good rate performance.
  • the negative electrode film layer may further include other negative electrode active materials in addition to the above-mentioned carbonaceous materials.
  • the other negative electrode active materials include but are not limited to one or more of natural graphite, artificial graphite, soft carbon, silicon-based materials, tin-based materials and lithium titanate.
  • the silicon-based material may include one or more of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite and silicon alloy material.
  • the tin-based material may include one or more of elemental tin, tin oxide and tin alloy material.
  • the negative electrode film layer may further include a negative electrode conductive agent.
  • a negative electrode conductive agent may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the negative electrode film layer may further include a negative electrode binder.
  • the negative electrode binder may include one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).
  • SBR styrene-butadiene rubber
  • SR-1B water-soluble unsaturated resin
  • PAM polyacrylamide
  • PVA polyvinyl alcohol
  • SA sodium alginate
  • CMCS carboxymethyl chitosan
  • the negative electrode film layer may further include other additives.
  • the other additives may include a thickener, such as sodium carboxymethyl cellulose (CMC), a PTC thermistor material, and the like.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • a metal foil a copper foil may be used.
  • the composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer.
  • the metal material may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy.
  • the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS) and polyethylene (PE).
  • the negative electrode film layer is usually formed by coating the negative electrode slurry on the negative electrode current collector, drying and cold pressing.
  • the negative electrode slurry is usually formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional auxiliary agents in a solvent and stirring them uniformly.
  • the solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.
  • the negative electrode plate does not exclude other additional functional layers in addition to the negative electrode film layer.
  • the negative electrode plate described in the present application also includes a conductive primer layer (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector; in some embodiments, the negative electrode plate described in the present application also includes a protective layer covering the surface of the negative electrode film layer.
  • the positive electrode plate includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector.
  • the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • a metal foil aluminum foil may be used.
  • the composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer.
  • the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy.
  • the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS) and polyethylene (PE).
  • the positive electrode film layer generally comprises a positive electrode active material, an optional binder and an optional conductive agent.
  • the positive electrode film layer is generally formed by coating the positive electrode slurry on the positive electrode current collector, drying and cold pressing.
  • the positive electrode slurry is generally formed by dispersing the positive electrode active material, the optional conductive agent, the optional binder and any other components in a solvent and stirring evenly.
  • the solvent may be N-methylpyrrolidone (NMP), but is not limited thereto.
  • the binder for the positive electrode film layer may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PTFE polytetrafluoroethylene
  • vinylidene fluoride-tetrafluoroethylene-propylene terpolymer vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer
  • tetrafluoroethylene-hexafluoropropylene copolymer tetraflu
  • the conductive agent for the positive electrode film layer includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the positive electrode active material may be a positive electrode active material for a secondary battery known in the art.
  • the positive electrode active material may include, but is not limited to, one or more of lithium-containing transition metal oxides, lithium-containing phosphates, and their respective modified compounds.
  • the lithium transition metal oxide may include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds.
  • lithium-containing phosphate may include, but are not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, a composite material of lithium iron manganese phosphate and carbon, and their respective modified compounds.
  • the positive electrode active material for the lithium ion battery may include one or more of a lithium transition metal oxide and a modified compound thereof of the general formula Li a Ni b Co c M d O e A f . 0.8 ⁇ a ⁇ 1.2, 0.5 ⁇ b ⁇ 1, 0 ⁇ c ⁇ 1, 0 ⁇ d ⁇ 1, 1 ⁇ e ⁇ 2, 0 ⁇ f ⁇ 1, M includes one or more selected from Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and A includes one or more selected from N, F, S and Cl.
  • a positive electrode active material for a lithium ion battery may include one or more of LiCoO2 , LiNiO2 , LiMnO2 , LiMn2O4 , LiNi1/3Co1 / 3Mn1 / 3O2 (NCM333 ) , LiNi0.5Co0.2Mn0.3O2 ( NCM523 ) , LiNi0.6Co0.2Mn0.2O2 ( NCM622 ) , LiNi0.8Co0.1Mn0.1O2 ( NCM811), LiNi0.85Co0.15Al0.05O2 , LiFePO4 , and LiMnPO4 .
  • the positive electrode active material may include but is not limited to one or more of sodium-containing transition metal oxides, polyanion materials (such as phosphates, fluorophosphates, pyrophosphates, sulfates, etc.), and Prussian blue materials.
  • the positive active material for a sodium ion battery may include one or more of NaFeO2, NaCoO2, NaCrO2, NaMnO2, NaNiO2, NaNi1/2Ti1/2O2, NaNi1/2Mn1/2O2, Na2/3Fe1/3Mn2/3O2 , NaNi1 / 3Co1 / 3Mn1 / 3O2 , NaFePO4 , NaMnPO4 , NaCoPO4 , Prussian blue - based materials , and materials of the general formula XpM'q ( PO4 ) rOxY3 -x .
  • X includes one or more selected from H + , Li + , Na + , K + and NH4 + , M ' is a transition metal cation, optionally including one or more selected from V, Ti, Mn, Fe, Co, Ni, Cu and Zn, and Y is a halogen anion, optionally including one or more selected from F, Cl and Br.
  • the modified compound of each positive electrode active material mentioned above may be a compound obtained by doping and/or surface coating the positive electrode active material.
  • the present application has no particular limitation on the type of the electrolyte, which can be selected according to actual needs.
  • the electrolyte can be selected from at least one of a solid electrolyte and a liquid electrolyte (ie, an electrolyte solution).
  • the electrolyte is an electrolyte solution
  • the electrolyte solution includes an electrolyte salt and a solvent.
  • the type of the electrolyte salt is not particularly limited and can be selected according to actual needs.
  • the electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium bisoxalatoborate (LiBOB), lithium difluorophosphate (LiPO 2 F 2 ), lithium difluorobisoxalatophosphate (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).
  • LiPF 6 lithium hexafluorophosphate
  • LiBF 4 lithium perchlorate
  • the electrolyte salt may include one or more of sodium hexafluorophosphate (NaPF 6 ), sodium tetrafluoroborate (NaBF 4 ), sodium perchlorate (NaClO 4 ), sodium hexafluoroarsenate (NaAsF 6 ), sodium bis(fluorosulfonyl)imide (NaFSI), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), sodium trifluoromethanesulfonate (NaTFS), sodium difluorooxalatoborate (NaDFOB), sodium dioxalatoborate (NaBOB), sodium difluorophosphate (NaPO 2 F 2 ), sodium difluorobis(oxalatophosphate) (NaDFOP) and sodium tetrafluorooxalatophosphate (NaTFOP).
  • NaPF 6 sodium hexafluorophosphate
  • NaBF 4
  • the solvent may include ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sul
  • the electrolyte may further include additives.
  • the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high temperature performance, and additives that improve battery low temperature power performance.
  • Secondary batteries using electrolytes and some secondary batteries using solid electrolytes also include a separator.
  • the separator is arranged between the positive electrode plate and the negative electrode plate to play a role of isolation.
  • the present application has no particular restrictions on the type of the separator, and any known porous structure separator with good chemical stability and mechanical stability can be selected.
  • the material of the isolation membrane may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation membrane may be a single-layer film or a multi-layer composite film. When the isolation membrane is a multi-layer composite film, the materials of each layer are the same or different.
  • the positive electrode sheet, the separator, the negative electrode sheet and the electrolyte can be assembled to form a secondary battery.
  • the positive electrode sheet, the separator, and the negative electrode sheet can be formed into an electrode assembly through a winding process and/or a lamination process, and the electrode assembly is placed in an outer package, and the electrolyte is injected after drying. After vacuum packaging, standing, formation, shaping and other processes, a battery cell is obtained.
  • Multiple battery cells can also be further connected in series, in parallel or in mixed connection to form a battery module.
  • Multiple battery modules can also be connected in series, in parallel or in mixed connection to form a battery pack. In some embodiments, multiple battery cells can also directly form a battery pack.
  • the fourth aspect of the embodiment of the present application provides an electric device, the electric device includes the secondary battery of the present application.
  • the secondary battery can be used as a power source for the electric device, and can also be used as an energy storage unit for the electric device.
  • the electric device can be, but is not limited to, a mobile device (such as a mobile phone, a tablet computer, a laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc.
  • the electrical device may select a specific type of secondary battery according to its usage requirements, such as a battery cell, a battery module or a battery pack.
  • Fig. 6 is a schematic diagram of an electric device as an example.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.
  • a battery pack or a battery module can be used as a power source.
  • the electric device may be a mobile phone, a tablet computer, a notebook computer, etc.
  • the electric device is usually required to be light and thin, and a battery cell may be used as a power source.
  • Pine wood was used as the carbon source, with a particle size of ⁇ 1 mm, a cellulose content of 40 wt%, a hemicellulose content of 23%, a lignin content of 27%, and an ash content of 1 wt%.
  • the pine wood was heated to 150°C (as the first temperature T1) at 1°C/min (as the first heating rate) under a nitrogen atmosphere, and then kept warm for 10 hours (first time t1). After the heating, it was cooled to room temperature to obtain a first intermediate product.
  • the first intermediate product is crushed by air jet mill to a volume particle size Dv50 of 4 ⁇ m-6 ⁇ m, then washed with a 3mol/L perchloric acid aqueous solution at 50°C for 10 hours, then washed with deionized water until neutral, then washed with a 3mol/L NaOH aqueous solution at 80°C for 20 hours, then washed with deionized water until neutral, and finally dried by air to remove moisture to obtain a first intermediate product with an ash content of ⁇ 0.01wt%.
  • the first intermediate product obtained above was heated to 1400°C (as the second temperature T2) at 0.5°C/min (as the second heating rate) under a nitrogen atmosphere and then kept warm for 6 hours (as the second time t2), after which a carbonaceous material was obtained.
  • a carbonaceous material with a mass of m1 is evenly placed in a container and the stacking thickness of the carbonaceous material is ⁇ 5 mm.
  • the water vapor adsorption mass m2 and the water vapor adsorption time t when the carbonaceous material adsorbs water vapor to reach equilibrium are recorded.
  • the water vapor adsorption rate v m2 /( m1 ⁇ t), the unit of m1 is g, the unit of m2 is g, and the unit of t is h.
  • the Archimedean impregnation volume displacement method was used to test the true density of carbonaceous materials with n-butanol as the medium.
  • the method for preparing the carbonaceous material is similar to that in Example 1, except that the preparation process parameters of the carbonaceous material are adjusted, as shown in Table 1 for details.
  • the carbonaceous materials prepared in the embodiments and comparative examples are fully stirred and mixed with the binder styrene-butadiene rubber (SBR), the thickener sodium carboxymethyl cellulose (CMC-Na), and the conductive agent carbon black in a mass ratio of 96.2:1.8:1.2:0.8 in an appropriate amount of solvent deionized water to form a uniform negative electrode slurry; the negative electrode slurry is evenly coated on the surface of the negative electrode current collector copper foil, and dried in an oven for use.
  • SBR binder styrene-butadiene rubber
  • CMC-Na thickener sodium carboxymethyl cellulose
  • conductive agent carbon black in a mass ratio of 96.2:1.8:1.2:0.8 in an appropriate amount of solvent deionized water
  • Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain an organic solvent, and then NaPF 6 is dissolved in the above organic solvent to prepare an electrolyte with a concentration of 1 mol/L.
  • a metal sodium sheet is used as a counter electrode and a polyethylene (PE) film is used as an isolation membrane to assemble a CR2430 button battery in an argon-protected glove box.
  • PE polyethylene
  • the button cells prepared in each embodiment and comparative example were first discharged at a constant current to 0 V at a current density of 10 mA/g, and the first-cycle discharge capacity of the button cells was recorded; thereafter, they were charged at a constant current to 2.0 V at a current density of 10 mA/g, and the first-cycle charging capacity of the button cells was recorded.
  • the first coulombic efficiency of the carbonaceous material (%) the first cycle charging capacity of the button cell/the first cycle discharging capacity of the button cell ⁇ 100%.
  • the rate performance was characterized by the ratio of the discharge capacity at 1C to the discharge capacity at 0.33C. The higher the ratio, the better the rate performance.
  • Figures 7 to 9 are scanning electron microscope images of the carbonaceous material provided by the present application at different magnifications. As shown in Figures 7 to 9, the morphology of the carbonaceous material provided by the present application is an irregular multi-angle shape.
  • Comprehensive test results in Table 2 show that when the carbonaceous material meets the conditions of constant temperature and humidity of 25°C and 40%RH, and the water vapor adsorption rate v is between 0.015 and 0.050, the carbonaceous material has a higher gram capacity, a higher first coulomb efficiency, and a good rate performance.
  • the carbonaceous materials prepared in Comparative Examples 1-7 have a water vapor adsorption rate v of either less than 0.015 or greater than 0.050 under constant temperature and humidity conditions of 25°C and 40% RH, which cannot enable the carbonaceous materials to have both a higher gram capacity, a higher first coulombic efficiency and good rate performance.
  • Comparative Example 1 uses rice husk as a carbon source, and its ash content is higher than 5wt%. Since the ash will not only produce a catalytic reaction during the low-temperature pre-carbonization treatment, consume the C element content, and reduce the active ion storage sites, but also reduce the metal impurities in the ash to metal elements and then agglomerate during the subsequent high-temperature carbonization treatment. The agglomeration of metal elements will cause the collapse of the carbon skeleton structure, especially the collapse of the capillary structure, which will lead to a reduction in the storage space of active ions in the obtained carbonaceous material, and a decrease in capacity, which is manifested as a too low water vapor adsorption rate.
  • the metal impurities also have catalytic activity, which will lead to an aggravated decomposition of the carbon skeleton structure during the cracking process, and make the pore structure tend to form a large-sized large mesoporous structure and/or a large-porous structure, thereby resulting in an increase in the proportion of the electrolyte infiltration area inside the obtained carbonaceous material, an increase in the consumption of active ions during SEI film formation, an increase in the first irreversible capacity loss, and a decrease in the first coulombic efficiency.
  • Comparative Example 2 when preparing the carbonaceous material, no low-temperature pre-carbonization treatment was performed, which resulted in poor closed-pore effect of the carbonaceous material, low content of capillary pore structure and high content of large mesoporous structure and/or macroporous structure, and thus a high proportion of electrolyte infiltration area inside the carbonaceous material, high first irreversible capacity loss, and low first coulombic efficiency.
  • the carbonaceous material can have a higher gram capacity, first coulombic efficiency and/or rate performance.

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Abstract

一种碳质材料及其制备方法、以及含有其的二次电池和用电装置，碳质材料在25笆、40%RH恒温恒湿条件下，采用水蒸气进行吸附测试时的吸附速率v满足0.015sgvsg0.050,水蒸气吸附测试在如下条件下进行：在25笆、40%RH的恒温恒湿箱中，将质量为m1的碳质材料放置在容器中，记录碳质材料吸附水蒸气达到平衡时的水蒸气吸附质量m2与水蒸气吸附时间t,则水蒸气吸附速率v=m2/（m1X t）,m1的的计计量量单单位位为为gg,,m2的计量单位为g，t的计量单位为h。碳质材料能兼顾较高的克容量、较高的首次库伦效率和较高的结构稳定性。

Description

碳质材料及其制备方法、以及含有其的二次电池和用电装置 技术领域
本申请属于电池技术领域，具体涉及一种碳质材料及其制备方法、以及含有其的二次电池和用电装置。
背景技术
近年来，二次电池被广泛应用于水力、火力、风力和太阳能电站等储能电源系统，以及电动工具、电动自行车、电动摩托车、电动汽车、军事装备、航空航天等多个领域。随着二次电池的应用及推广，其能量密度、使用寿命和倍率性能受到越来越多的关注。石墨是二次电池最常用的负极活性材料，但其理论克容量仅为372mAh/g，能量密度提升空间十分有限；同时石墨的层间距较小，倍率性能提升也受到限制。硬碳作为一种新型负极活性材料，在二次电池充放电过程中能够实现活性离子的快速嵌入和脱出，因此发展前景十分广阔。但是，硬碳的克容量和首次库伦效率较低，对二次电池能量密度、使用寿命和倍率性能的提升有限。
发明内容
本申请的目的在于提供一种碳质材料及其制备方法、以及含有其的二次电池和用电装置，所述碳质材料能兼顾较高的克容量、较高的首次库伦效率和较高的结构稳定性，并且能使二次电池同时具有高能量密度、长使用寿命和良好的倍率性能。
本申请第一方面提供一种碳质材料，所述碳质材料在25℃、40％RH恒温恒湿条件下，采用水蒸气进行吸附测试时的吸附速率v满足0.015≤v≤0.050，所述水蒸气吸附测试在如下条件下进行：在25℃、40％RH的恒温恒湿箱中，将质量为m 1的所述碳质材料放置在容器中，记录所述碳质材料吸附水蒸气达到平衡时的水蒸气吸附质量m 2与水蒸气吸附时间t，则水蒸气吸附速率v＝m 2/(m 1×t)，m 1的计量单位为g，m 2的计量单位为g，t的计量单位为h。
与目前商品化的碳质材料相比，本申请提供的碳质材料能兼顾较高的克容量、较高的首次库伦效率和较高的结构稳定性，并且能使二次电池同时具有高能量密度、长使用寿命和良好的倍率性能。尽管机理尚不明确，本申请的发明人推测一个可能的原因是，当水蒸气吸附速率v在0.015至0.050之间时，本申请的碳质材料的结构稳定性高且具有独特的孔结构，能够方便活性离子的嵌入、储存和脱出，进而本申请的碳质材料能够兼顾较高的克容量和首次库伦效率，并且能使二次电池同时具有高能量密度、长使用寿命和良好的倍率性能。
在本申请的任意实施方式中，0.020≤v≤0.050。由此有助于进一步提升碳质材料的克容量、首次库伦效率和结构稳定性，进而还能进一步提升二次电池的能量密度、使用寿命和倍率性能。
在本申请的任意实施方式中，所述碳质材料吸附水蒸气达到平衡时的水蒸气吸附时间t为1h-12h，可选为4.5h-7h。当碳质材料吸附水蒸气达到平衡时的水蒸气吸附时间满足上述特定的范围时，有助于进一步提升碳质材料的克容量、首次库伦效率和结构稳定性，进而能进一步提升二次电池的能量密度、使用寿命和倍率性能。
在本申请的任意实施方式中，所述碳质材料的真密度ρ为1.0g/cm 3-2.2g/cm 3，可选为1.3g/cm 3-1.7g/cm 3。当碳质材料的真密度满足上述特定的范围时，有助于进一步提升碳质材料的克容量和首次库伦效率。
在本申请的任意实施方式中，所述碳质材料包括多个纳米孔结构，可选地，所述碳质材料包括多个孔径在10nm以下的孔结构。
在本申请的任意实施方式中，在所述碳质材料的拉曼光谱中，I d/I g为1.0-1.3，可选为1.05-1.15，I d表示拉曼位移在1350±50cm -1范围内的d峰强度，I g表示拉曼位移在1580±50cm -1范围内的g峰强度。此时，碳质材料具有更高的克容量和更高首次库伦效率，同时还具有良好的倍率性能。
在本申请的任意实施方式中，所述碳质材料的(002)晶面的层间距为≥0.37nm，可选为0.37nm-0.42nm。
在本申请的任意实施方式中，在所述碳质材料的X射线衍射谱中，(002)晶面峰对应的2θ值在22°至24°之间。
在本申请的任意实施方式中，所述碳质材料的体积粒径Dv50为4μm-6μm。
在本申请的任意实施方式中，所述碳质材料的体积粒径Dv90为8μm-16μm。
碳质材料的体积粒径Dv50和/或Dv90在合适的范围内时，有利于提升活性离子和电子传输性能，从而能够进一步提升二次电池的倍率性能。
在本申请的任意实施方式中，所述碳质材料的比表面积为0.1m 2/g-20m 2/g，可选为1m 2/g-20m 2/g。当碳质材料的比表面积在合适的范围内时，碳质材料能同时具有更高的克容量和首次库伦效率，同时还能具有更好的倍率性能。
在本申请的任意实施方式中，所述碳质材料在50000N作用力下的粉体压实密度为0.90g/cm 3-1.05g/cm 3，可选为0.92g/cm 3-1.02g/cm 3。碳质材料的粉体压实密度在合适的范围内时，可以提升负极极片的压实密度，进而提高二次电池的能量密度。
在本申请的任意实施方式中，所述碳质材料的振实密度为0.78g/cm 3-0.95g/cm 3，可选为0.83g/cm 3-0.93g/cm 3。碳质材料的振实密度在合适的范围内时，可以提升负极极片的压实密度，进而提高二次电池的能量密度。
本申请第二方面提供一种碳质材料的制备方法，包括如下步骤：S10，提供碳源：所述碳源为纤维素类生物质材料；S20，低温预碳化处理：将所述碳源在保护气体气氛下，以第一升温速率升温至第一温度T1后保温处理第一时间t1，得到第一中间产物；S30，高温碳化处理：将所得到的第一中间产物在保护气体气氛下，以第二升温速率升温至第二温度T2后保温处理第二时间t2，得到碳质材料，其中，所述碳质材料在25℃、40％RH恒温恒湿条件下，采用水蒸气进行吸附测试时的吸附速率v满足0.015≤v≤0.050，所述水 蒸气吸附测试在如下条件下进行：在25℃、40％RH的恒温恒湿箱中，将质量为m 1的所述碳质材料放置在容器中，记录所述碳质材料吸附水蒸气达到平衡时的水蒸气吸附质量m 2与水蒸气吸附时间t，则水蒸气吸附速率v＝m 2/(m 1×t)，m 1的计量单位为g，m 2的计量单位为g，t的计量单位为h。
通过本申请提供的制备方法获得的碳质材料能够兼顾较高的克容量、较高的首次库伦效率和较高的结构稳定性，进而能使二次电池同时具有高能量密度、长使用寿命和良好的倍率性能。并且与现有商品化的硬碳相比，通过本申请的制备方法得到的碳质材料的克容量、首次库伦效率和倍率性能均得到明显提升。
在本申请的任意实施方式中，所述纤维素类生物质材料中的纤维素含量为大于0wt％且小于等于100wt％，且灰分含量为0wt％-5wt％。
在本申请的任意实施方式中，所述纤维素类生物质材料中的纤维素含量为大于等于20wt％且小于100wt％，且灰分含量为0wt％-5wt％。
在本申请的任意实施方式中，所述纤维素类生物质材料中的纤维素含量为大于0wt％且小于等于100wt％，且灰分含量为0wt％-2wt％。
在本申请的任意实施方式中，所述纤维素类生物质材料中的纤维素含量为大于等于20wt％且小于100wt％，且灰分含量为0wt％-2wt％。
在本申请的任意实施方式中，所述纤维素类生物质材料中的半纤维素含量为0wt％-70wt％，可选为0wt％-30wt％。
在本申请的任意实施方式中，所述纤维素类生物质材料中的木质素含量为0wt％-60wt％，可选为10wt％-60wt％。
通过调节纤维素类生物质材料中的纤维素、灰分、半纤维素和木质素中的一者或多者的含量满足上述范围，有助于所获得的碳质材兼顾较高的克容量、较高的首次库伦效率和较高的结构稳定性，进而能进一步提升二次电池的能量密度、使用寿命和倍率性能。
在本申请的任意实施方式中，所述纤维素类生物质材料包括木本生物质材料中的一种或多种，可选为包括硬木、软木和坚果壳中的一种或多种，更可选为包括松木、毛竹和核桃壳中的一种或多种。
在本申请的任意实施方式中，第一升温速率为1℃/min-10℃/min，可选为1℃/min-3℃/min。
在本申请的任意实施方式中，第一温度T1为150℃-1000℃，可选为300℃-700℃。
在本申请的任意实施方式中，第一时间t1为1h-20h，可选为5h-20h。
在S20中，通过调节第一升温速率、第一温度和第一时间等中的一者或者多者在上述范围内，有利于更好地调控碳骨架结构和表面，提高低温预碳化处理效果，并获得具有合适水蒸气吸附速率的碳质材料。
在本申请的任意实施方式中，第二升温速率为≤10℃/min，可选为0.5℃/min-10℃/min。
在本申请的任意实施方式中，第二温度T2为1000℃-1600℃，可选为1200℃-1500℃。
在本申请的任意实施方式中，第二时间t2为1h-12h，可选为3h-10h。
在S30中，通过调节第二升温速率、第二温度和第二时间等中的一者或者多者在上述范围内，有利于提高孔结构的闭孔效果，提高高温碳化处理效果，并获得具有合适水蒸气吸附速率的碳质材料。
在本申请的任意实施方式中，t1+t2为10h-30h。由此有助于所获得的碳质材料具有合适的水蒸气吸附速率，具有高容量、高首次库伦效率和高结构稳定性。
在本申请的任意实施方式中，在S20之后、S30之前所述方法还包括步骤：将S20所得到的第一中间产物进行破碎处理，或者将S20所得到的第一中间产物进行洗涤除杂处理，或者将S20所得到的第一中间产物进行先破碎处理后洗涤除杂处理，以得到灰分含量≤0.01wt％的第一中间产物，所述洗涤除杂处理工艺至少包括酸性溶液洗涤步骤和碱性溶液洗涤步骤。由此，有助于进一步提升碳质材料的克容量、首次库伦效率和结构稳定性，同时还有助于降低碳质材料的真密度。
在本申请的任意实施方式中，所述洗涤除杂处理工艺依次包括如下步骤：酸性溶液洗涤、水洗、碱性溶液洗涤、水洗以及干燥；或，所述洗涤除杂处理工艺依次包括如下步骤：碱性溶液洗涤、水洗、酸性溶液洗涤、水洗以及干燥。
在本申请的任意实施方式中，所述酸性溶液的H +浓度为0.1mol/L-6moL/L，可选为1mol/L-6moL/L。
在本申请的任意实施方式中，所述酸性溶液的洗涤温度为10℃-95℃，可选为30℃-95℃。
在本申请的任意实施方式中，所述酸性溶液的洗涤时间为1h-24h，可选为10h-24h。
在本申请的任意实施方式中，所述酸性溶液的溶质包括盐酸、硝酸、硫酸和高氯酸中的一种或多种，溶剂包括水。
通过调节酸性溶液的H +浓度、洗涤温度、洗涤时间、溶质种类等中的一者或者多者在上述范围内，有利于实现充分洗涤，更好地除去金属杂质。
在本申请的任意实施方式中，所述碱性溶液的OH -浓度为0.1mol/L-6moL/L，可选为1mol/L-6moL/L。
在本申请的任意实施方式中，所述碱性溶液的洗涤温度为10℃-95℃，可选为30℃-95℃。
在本申请的任意实施方式中，所述碱性溶液的洗涤时间为1h-24h，可选为10h-24h。
在本申请的任意实施方式中，所述碱性溶液的溶质包括NaOH、KOH或其组合，溶剂包括水。
通过调节碱性溶液的OH -浓度、洗涤温度、洗涤时间、溶质种类等中的一者或者多者在上述范围内，有利于实现充分洗涤。
本申请第三方面提供一种二次电池，其包括负极极片，所述负极极片包括本申请第一方面的碳质材料或通过本申请第二方面的方法制备得到的碳质材料。
本申请第四方面提供一种用电装置，其包括本申请第三方面的二次电池。
本申请提供碳质材料能够兼顾较高的克容量、较高的首次库伦效率和较高的结构稳定性，进而能使二次电池同时具有高能量密度、长使用寿命和良好的倍率性能。本申请的用电装置包括本申请提供的二次电池，因而至少具有与所述二次电池相同的优势。
附图说明
为了更清楚地说明本申请实施例的技术方案，下面将对本申请实施例中所需要使用的附图作简单地介绍。显而易见地，下面所描述的附图仅仅是本申请的一些实施方式， 对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据附图获得其他的附图。
图1是本申请的电池单体的一实施方式的示意图。
图2是本申请的电池单体的一实施方式的分解示意图。
图3是本申请的电池模块的一实施方式的示意图。
图4是本申请的电池包的一实施方式的示意图。
图5是图4所示的电池包的实施方式的分解示意图。
图6是包含本申请的二次电池作为电源的用电装置的一实施方式的示意图。
图7至图9是本申请提供的碳质材料在不同放大倍数下的扫描电子显微镜图。
在附图中，附图未必按照实际的比例绘制。附图标记说明如下：1电池包，2上箱体，3下箱体，4电池模块，5电池单体，51壳体，52电极组件，53盖板。
具体实施方式
以下，适当地参照附图详细说明具体公开了本申请的碳质材料及其制备方法、以及含有其的二次电池和用电装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案，并且这样的技术方案应被认为包含在本申请的公开内容中。
如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案，并且这样的技术方案应被认为包含在本申请的公开内容中。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
如果没有特别的说明，本申请中使用的术语具有本领域技术人员通常所理解的公知含义。
如果没有特别的说明，本申请中提到的各参数的数值可以用本领域常用的各种测试方法进行测定，例如，可以按照本申请给出的测试方法进行测定。
如果没有特别的说明，在本申请中，术语“活性离子”是指能在二次电池正极和负极之间往返嵌入和脱出的离子，包括但不限于锂离子、钠离子等。
在本申请中，术语“多个”、“多种”是指两个或两种以上。
根据国际纯粹与应用化学联合会(IUPAC)的定义，微孔(Micropores)是指孔径＜2nm的孔，介孔(Mesopores)是指孔径为2nm-50nm的孔，大孔(Macropores)是指孔径＞50nm的孔。
在本申请的上下文中，术语“微孔”出现时，均指孔径＜2nm的孔；术语“介孔”出现时，均指孔径为2nm-50nm的孔；术语“大孔”出现时，均指孔径＞50nm的孔。
在本申请的上下文中，术语“小介孔”是指孔径为2nm-10nm的孔，术语“大介孔”是指孔径为大于10nm且小于等于50nm的孔。
在本申请的上下文中，术语“毛细孔”出现时，是指微孔和/或小介孔，即孔径≤10nm的孔。
在本申请的上下文中，术语“较大的孔”与“较小的孔”表示相对概念。
随着二次电池的应用及推广，其能量密度、使用寿命和倍率性能受到越来越多的关注。负极活性材料性能在一定程度上决定了二次电池的能量密度、使用寿命和安全性。石墨(包括天然石墨、人造石墨)是二次电池最常用的负极活性材料，但其理论克容量仅为372mAh/g，能量密度提升空间十分有限；同时石墨的层间距较小，倍率性能提升也受到限制，已经不能满足高倍率性能二次电池的实际需求。
与石墨相比，硬碳的层间距更大，因此，有利于活性离子的快速嵌入和脱出，从而能使二次电池具有优异的低温性能、功率性能和安全性能，特别是在动力电池领域，硬碳具有独特的优势。但是，目前商品化的硬碳大多属于低容量型硬碳，其容量和首次库伦效率较低，例如容量通常在200mAh/g至280mAh/g之间，首次库伦效率通常低于75％，由此导致其实际应用严重受限。
因此，如何同时提高硬碳的克容量和首次库伦效率仍是目前亟待解决的技术难题。
鉴于此，本申请实施方式第一方面提供了一种碳质材料，其兼顾较高的克容量、较高的首次库伦效率和较高的结构稳定性，并且能使二次电池同时具有高能量密度、长使用寿命和良好的倍率性能。
碳质材料
本申请提供的碳质材料在25℃、40％RH恒温恒湿条件下，采用水蒸气进行吸附测试时的吸附速率v满足0.015≤v≤0.050。
所述水蒸气吸附测试在如下条件下进行：在25℃、40％RH的恒温恒湿箱中，将质量为m 1的所述碳质材料放置在容器中，记录所述碳质材料吸附水蒸气达到平衡时的水蒸气吸附质量m 2与水蒸气吸附时间t，则水蒸气吸附速率v＝m 2/(m 1×t)，m 1的计量单位为g，m 2的计量单位为g，t的计量单位为h。在所述容器中，所述碳质材料的堆积厚度为≤5mm。
在水蒸气吸附测试中，当所述碳质材料吸附水蒸气后的总质量不再继续增加时，认为所述碳质材料吸附水蒸气达到了平衡，记录此时的测试时间，即为水蒸气吸附时间t，用此时得到的所述碳质材料的总质量减去所述碳质材料的初始质量m 1即得到水蒸气吸附质量m 2(即所述碳质材料吸附水蒸气达到平衡时增加的质量)。
RH(Relative Humidity)表示相对湿度，其是指空气中水蒸气分压与相同温度下水的饱和蒸气压的百分比。
与目前商品化的碳质材料相比，本申请提供的碳质材料能兼顾较高的克容量、较高的首次库伦效率和较高的结构稳定性，并且能使二次电池同时具有高能量密度、长使用寿命和良好的倍率性能。尽管机理尚不明确，本申请的发明人推测一个可能的原因是，当水蒸气吸附速率v在0.015至0.050之间时，本申请的碳质材料的结构稳定性高且具有独特的孔结构，能够方便活性离子的嵌入、储存和脱出，进而本申请的碳质材料能够兼顾较高的克容量和首次库伦效率，并且能使二次电池同时具有高能量密度、长使用寿命和良好的倍率性能。
本申请的发明人在研究过程中发现，在25℃、40％RH恒温恒湿条件下，水蒸气会优先吸附进入碳质材料的毛细孔结构(即微孔结构和/或小介孔结构)中，且通常不会进入碳质材料的大介孔结构和/或大孔结构中，由此25℃、40％RH恒温恒湿条件下的水蒸气吸附速率v可以直观地反映碳质材料中适合活性离子储存的位点含量。
水蒸气吸附速率v小于0.015时，认为碳质材料内部所包含的毛细孔结构很少，且孔结构多为大介孔结构和/或大孔结构，因此碳质材料的结构稳定性差且内部所包含的能够容纳活性离子的空间很少，不适合活性离子的储存，进而碳质材料的克容量还较低；此外，由于孔结构多为大介孔结构和/或大孔结构，由此还导致碳质材料内部电解液浸润区域占比增加，固体电解质界面膜(下称SEI膜)成膜时对活性离子消耗增加，首次不可逆容量损失增加，进而碳质材料的克容量和首次库伦效率均较低。
水蒸气吸附速率v大于0.050时，认为碳质材料的比表面积较高，由此导致SEI膜成膜时对活性离子消耗增加，首次不可逆容量损失增加，首次库伦效率降低。此外，碳质材料的吸水性较强，二次电池制备和使用过程中部分水分子与碳质材料表面的官能团(例如含氧官能团)将以化学键较牢固的结合，由此水分子不易脱去，从而会堵塞碳质材料的毛细孔结构，妨碍活性离子的嵌入和脱出，同时碳质材料表面吸附的水分子还可能会和电解液发生反应，进而还会导致碳质材料的克容量和首次库伦效率均降低。
在一些实施例中，v可以为0.016，0.018，0.020，0.022，0.024，0.026，0.028，0.030，0.032，0.034，0.036，0.038，0.040，0.042，0.044，0.046，0.048，0.050或上述范围内任意数值组成的范围，可选地，0.018≤v≤0.050，0.020≤v≤0.050。由此有助于进一步提升 碳质材料的克容量、首次库伦效率和结构稳定性，进而还能进一步提升二次电池的能量密度、使用寿命和倍率性能。
在一些实施例中，所述碳质材料吸附水蒸气达到平衡时的水蒸气吸附时间t为1h-12h。可选地，所述碳质材料吸附水蒸气达到平衡时的水蒸气吸附时间t为3h-12h，4h-12h，4h-9h，4.5h-7h。发明人在进一步研究中发现，当碳质材料吸附水蒸气达到平衡时的水蒸气吸附时间满足上述特定的范围时，有助于进一步提升碳质材料的克容量、首次库伦效率和结构稳定性，进而能进一步提升二次电池的能量密度、使用寿命和倍率性能。
水蒸气吸附时间较长时，认为碳质材料所含的毛细孔结构较多，此时碳质材料的骨架结构较脆弱，容易坍塌形成尺寸较大的孔，进而导致碳质材料内部电解液浸润区域占比增加，首次不可逆容量损失增加，首次库伦效率降低；水蒸气吸附时间较短时，认为碳质材料所含的毛细孔结构较少，不适合活性离子的嵌入、储存和脱出，进而也会导致碳质材料的克容量和首次库伦效率降低。
在一些实施例中，所述碳质材料包括多个纳米孔结构。可选地，所述碳质材料包括多个孔径在10nm以下的孔结构。在一些实施例中，所述碳质材料还可以包括一个或多个孔径大于10nm的孔结构。
在一些实施例中，所述碳质材料的真密度ρ为1.0g/cm 3-2.2g/cm 3，可选为1.3g/cm 3-2.0g/cm 3，1.3g/cm 3-1.7g/cm 3，1.3g/cm 3-1.65g/cm 3，1.3g/cm 3-1.6g/cm 3，1.3g/cm 3-1.55g/cm 3。发明人在进一步研究中发现，当碳质材料的真密度满足上述特定的范围时，有助于进一步提升碳质材料的克容量和首次库伦效率。
碳质材料的真密度较小时，认为碳质材料的毛细孔结构丰富且闭孔效果良好，此时，标定液体(例如正丁醇)进入的空间比碳质材料的实际孔空间少，而这些未被进入的孔结构则可以储存活性离子，同时，电解液不易进入碳质材料颗粒内部，进而SEI膜成膜时对活性离子消耗降低；另外，碳质材料的真密度也不宜过低，此时可能会由于碳质材料的闭孔效果太好而导致活性离子也不易嵌入。碳质材料的真密度较大时，标定液体(例如正丁醇)很容易浸润颗粒内部，认为此时碳质材料的闭孔效果差、大介孔结构和/或大孔结构丰富，由此导致毛细孔结构容易暴露给电解液而导致活性离子储存空间减少，进而碳质材料的克容量和首次库伦效率均降低。
在本申请中，碳质材料的真密度为本领域公知的含义，可以用本领域已知的仪器及方法进行测定。例如可以采用阿基米德浸渍体积置换法进行测试，标定液体可采用正丁醇。测试仪器可采用粉体真密度计。
在一些实施例中，所述碳质材料可具有规则或者无规则的形貌，例如，所述碳质材料的形貌可为无规则的多棱角形。
在一些实施例中，所述碳质材料中的C元素含量可为95wt％-98wt％。
在一些实施例中，所述碳质材料中的O元素含量可为1wt％-5wt％。
在一些实施例中，所述碳质材料中的H元素含量可为<0.4wt％。
在一些实施例中，所述碳质材料中的N元素含量可为<2wt％。
在一些实施例中，所述碳质材料中的C、O、H和N元素含量的总和可为99wt％-99.5wt％。
在一些实施例中，所述碳质材料中杂质元素含量较少，杂质元素主要包含S、K、Ca、 Fe，S元素含量可为<0.0021wt％，K元素含量可为<0.0019wt％，Ca元素含量可为<0.0011wt％，Fe元素含量可为<0.0010wt％。
在一些实施例中，在所述碳质材料的拉曼光谱中，I d/I g为1.0-1.3，I d表示拉曼位移在1350±50cm -1范围内的d峰强度，I g表示拉曼位移在1580±50cm -1范围内的g峰强度。例如，I d/I g可以为1.0，1.05，1.1，1.15，1.2，1.25，1.3或以上任何数值组成的范围。可选地，I d/I g可以为1.05-1.15。
碳质材料的拉曼光谱可以使用拉曼光谱仪进行测试，测试时获取100个点的d峰强度和g峰强度，计算100个点的I d/I g，去除最大与最小的各30个I d/I g，剩余40个I d/I g的平均值作为碳质材料的I d/I g。测试仪器可以为Horiba LabRAM HR800拉曼光谱仪。测试条件可以为：激发波长532nm，光栅600刻线，物镜50倍，积分时间10s，累计次数3次，面扫。
d峰产生于碳原子晶格缺陷，g峰产生于sp2碳原子的面内振动。在碳质材料结构中，d峰强度与碳质材料结构缺陷数量相关，g峰强度与碳质材料结构中石墨微晶数量相关，因此，I d/I g可以表征碳质材料结构的有序度。I d/I g越小，碳质材料结构的有序度越高，碳平面的完整性越高，碳质材料的首次库伦效率增加，但是克容量变低、倍率性能变差。本申请的碳质材料满足I d/I g为1.0-1.3，此时，碳质材料结构的有序度适中，从而碳质材料具有更高的克容量和更高首次库伦效率，同时还具有良好的倍率性能。
在一些实施例中，所述碳质材料的(002)晶面的层间距为≥0.37nm，可选为0.37nm-0.42nm。
在一些实施例中，在所述碳质材料的X射线衍射谱中，(002)晶面峰对应的2θ值在22°至24°之间。
在本申请中，碳质材料的(002)晶面的层间距可以参照JIS K 0131-1996、JB/T 4220-2011，使用X射线衍射仪进行测试。测试仪器可以为Bruker D8 Discover X射线衍射仪。
在一些实施例中，所述碳质材料的体积粒径Dv50可为4μm-6μm。
在一些实施例中，所述碳质材料的体积粒径Dv90可为8μm-16μm。
在一些实施例中，所述碳质材料同时满足体积粒径Dv50为4μm-6μm并且体积粒径Dv90为8μm-16μm。
碳质材料的体积粒径Dv50和/或Dv90在合适的范围内时，有利于提升活性离子和电子传输性能，从而能够进一步提升二次电池的倍率性能。
在本申请中，碳质材料的体积粒径Dv50、Dv90为本领域公知的含义，其表示材料累计体积分布百分数分别达到50％、90％时所对应的粒径，可以用本领域已知的仪器及方法进行测定。例如可以参照GB/T 19077-2016粒度分布激光衍射法，采用激光粒度分析仪方便地测定。测试仪器可以为英国马尔文仪器有限公司的Mastersizer 2000E型激光粒度分析仪。
在一些实施例中，所述碳质材料的比表面积为0.1m 2/g-20m 2/g，可选为1m 2/g-20m 2/g。当碳质材料的比表面积在合适的范围内时，碳质材料能同时具有更高的克容量和首次库伦效率，同时还能具有更好的倍率性能。此外，碳质材料的比表面积在合适的范围内时，碳质材料与粘结剂之间还能具有较强的结合力，从而能提高负极极片的内聚力和粘结力，降低负极极片在循环过程中的体积膨胀，使二次电池具有更好的循环性能。
在本申请中，碳质材料的比表面积为本领域公知的含义，可以用本领域已知的仪器及方法进行测定。例如可以参照GB/T 19587-2017，采用氮气吸附比表面积分析测试方法测试，并用BET(Brunauer Emmett Teller)法计算得出，其中氮气吸附比表面积分析测试可以通过美国Micromeritics公司的ASAP 3020型表面积及孔径分析仪进行测定。
在一些实施例中，所述碳质材料在50000N作用力下的粉体压实密度为0.90g/cm 3-1.05g/cm 3，可选为0.92g/cm 3-1.02g/cm 3。碳质材料的粉体压实密度在合适的范围内时，可以提升负极极片的压实密度，进而提高二次电池的能量密度。
在本申请中，碳质材料的粉体压实密度为本领域公知的含义，可以用本领域已知的仪器及方法进行测定。例如可以参照标准GB/T24533-2009，通过电子压力试验机(例如可以为UTM7305型)进行测定。示例性测试方法如下：称取1g碳质材料粉末，加入底面积为1.327cm 2的模具中，加压至5000kg(相当于50000N)，保压30s，然后卸压，保持10s，然后记录并计算得到碳质材料在50000N作用力下的粉体压实密度。
在一些实施例中，所述碳质材料的振实密度为0.78g/cm 3-0.95g/cm 3，可选为0.83g/cm 3-0.93g/cm 3。碳质材料的振实密度在合适的范围内时，可以提升负极极片的压实密度，进而提高二次电池的能量密度。
在本申请中，碳质材料的振实密度为本领域公知的含义，可以用本领域已知的仪器及方法进行测定。例如可参照GB/T 5162-2006，使用粉体振实密度测试仪进行测定。测试仪器可以采用丹东百特BT-301。
碳质材料的制备方法
本申请实施方式的第二方面提供一种碳质材料的制备方法，包括如下步骤：S10，提供碳源：所述碳源为纤维素类生物质材料；S20，低温预碳化处理：将所述碳源在保护气体气氛下，以第一升温速率升温至第一温度T1后保温处理第一时间t1，得到第一中间产物；S30，高温碳化处理：将所得到的第一中间产物在保护气体气氛下，以第二升温速率升温至第二温度T2后保温处理第二时间t2，得到碳质材料，其中，所述碳质材料在25℃、40％RH恒温恒湿条件下，采用水蒸气进行吸附测试时的吸附速率v满足0.015≤v≤0.050。
所述水蒸气吸附测试在如下条件下进行：在25℃、40％RH的恒温恒湿箱中，将质量为m 1的所述碳质材料放置在容器中，记录所述碳质材料吸附水蒸气达到平衡时的水蒸气吸附质量m 2与水蒸气吸附时间t，则水蒸气吸附速率v＝m 2/(m 1×t)，m 1的计量单位为g，m 2的计量单位为g，t的计量单位为h。
本申请以纤维素类生物质材料为碳源制备碳质材料。纤维素属于生物质材料中的结晶度高的链状大分子有机物，一方面其热稳定性高，热解工艺参数可调节范围较宽，另一方面，链状大分子有机物在转化为碳质材料的过程中形成的孔结构的可控性高，能使其具有合适的水蒸气吸附速率，还有助于提高平台容量。当碳源不使用纤维素类生物质材料或者采用的生物质材料不包含纤维素时，由其制备的碳质材料的孔结构的可控性较差、且毛细孔结构含量少，表现为对水蒸气吸附速率过小。在一些实施例中，所述纤维素类生物质材料中的纤维素含量可为大于0wt％且小于等于100wt％，可选为10wt％-100wt％，20wt％-100wt％，30wt％-100wt％，40wt％-100wt％。由此有利于增加碳质材料的孔结构的可控性，并使其具有合适的水蒸气吸附速率。
碳质材料的制备工艺至少包括低温预碳化处理工序和高温碳化处理工序。低温预碳化处理能够调控碳骨架结构特性和表面特性，并适当提高碳收率；同时能够降低纤维素类生物质材料的韧性，有助于后续破碎处理和洗涤除杂处理。高温碳化处理可对低温预碳化处理得到的生物碳造成闭孔效果，从而减少碳质材料与电解液的接触面积，即减少SEI膜成膜时对活性离子的消耗，提高碳质材料的首次库伦效率；高温碳化处理还能够使低温预碳化处理得到的生物碳进行芳环化，由此能够提高碳质材料的有序程度和导电性，同时能够除去碳骨架结构上多余的O元素和H元素，并有助于形成有序的赝石墨微晶结构。
因此，通过本申请提供的制备方法获得的碳质材料能够兼顾较高的克容量、较高的首次库伦效率和较高的结构稳定性，进而能使二次电池同时具有高能量密度、长使用寿命和良好的倍率性能。并且与现有商品化的硬碳相比，通过本申请的制备方法得到的碳质材料的克容量、首次库伦效率和倍率性能均得到明显提升。
发明人在研究中还发现，纤维素类生物质材料需要具有较低的灰分含量。灰分不仅会在低温预碳化处理过程中产生催化反应，消耗C元素含量，减少活性离子储存位点，而且还会增加洗涤除杂处理工艺的复杂性和生产成本；并且，在后续高温碳化处理过程中，灰分中的金属杂质会还原成金属单质而后团聚。金属单质团聚时会导致碳骨架结构坍塌，尤其是毛细孔结构的坍塌，进而导致获得的碳质材料活性离子储存空间减少，容量下降，表现为对水蒸气吸附速率过小；同时金属杂质还具有催化活性，将导致裂解过程中碳骨架结构分解加剧，使孔结构趋向于形成尺寸较大的大介孔结构和/或大孔结构，由此导致碳骨架结构稳定性差并且获得的碳质材料内部电解液浸润区域占比增加，SEI膜成膜时对活性离子的消耗增加，首次不可逆容量损失增加，因此，碳质材料的首次库伦效率降低。在一些实施例中，所述纤维素类生物质材料中的灰分含量可为0wt％-5wt％，可选为0wt％-4wt％，0wt％-3wt％，0wt％-2wt％，0wt％-1wt％。由此能够降低杂质对碳质材料的不利影响，提高碳质材料的克容量、首次库伦效率和结构稳定性，并还有助于降低碳质材料的真密度。
在一些实施例中，可选地，所述纤维素类生物质材料中的纤维素含量为大于0wt％且小于等于100wt％，且灰分含量为0wt％-5wt％。
纤维素类生物质材料还可以包含半纤维素。半纤维素属于生物质材料中分子量较小的无定形高分子物质，其在低温预碳化处理过程中由于易分解成小分子糖类而挥发，由此有利于形成孔结构；但其含量不宜太高，当高于70wt％时，会造成碳骨架结构稳定性差，闭孔效果差，碳质材料中的大介孔结构和/或大孔结构含量增加，碳质材料内部电解液浸润区域占比增加，首次不可逆容量损失增加，首次库伦效率降低。在一些实施例中，所述纤维素类生物质材料中的半纤维素含量可为0wt％-70wt％，可选为0wt％-60wt％，0wt％-50wt％，0wt％-40wt％，0wt％-30wt％，0wt％-20wt％。
纤维素类生物质材料还可以包含木质素。木质素是含苯环的、具有高交联度的大分子有机物，其在低温预碳化处理过程中有助于碳六元环的形成，有助于提升碳骨架结构稳定性，从而对提升二次电池的倍率性能有利；但其形成的孔结构的可控性较差，由此当其含量过高，例如大于60wt％时，会造成获得的碳质材料平台容量提升空间有限。在一 些实施例中，所述纤维素类生物质材料中的木质素含量为0wt％-60wt％，可选为5wt％-60wt％，10wt％-60wt％，10wt％-50wt％，15wt％-50wt％。
在一些实施例中，所述纤维素类生物质材料中的纤维素含量为大于0wt％且小于等于100wt％，半纤维素含量为0wt％-70wt％，木质素含量为0wt％-60wt％，且灰分含量为0wt％-5wt％。可选地，所述纤维素类生物质材料中的纤维素含量为大于等于20wt％且小于100wt％，半纤维素含量为0wt％-30wt％，木质素含量为10wt％-60wt％，且灰分含量为0wt％-2wt％。由此，有助于所获得的碳质材料更好地兼顾较高的克容量、较高的首次库伦效率和较高的结构稳定性，进而能进一步提升二次电池的能量密度、使用寿命和倍率性能。
在一些实施例中，所述纤维素类生物质材料中的纤维素含量可为100wt％，即所述纤维素类生物质材料可以直接采用纤维素作为碳源。由此，有助于所获得的碳质材料具有高容量，但是其在制备过程中形成的碳骨架结构稳定性略有下降，由此导致对二次电池倍率性能的提升效果略有下降。
在本申请中，纤维素含量可采用酸水解蒽酮比色法进行检测。纤维素在酸性条件下可水解为β-D-葡萄糖，β-D-葡萄糖在强酸环境中脱水生成β-糠醛类化合物，其与蒽酮脱水缩合生成蓝绿色糠醛衍生物，产物在620nm处具有特征吸收峰，通过吸光值变化即可定量检测纤维素含量。例如，所述酸可为硫酸。
在本申请中，半纤维素含量可采用DNS比色法进行检测。半纤维素经酸处理后转化成还原糖，还原糖与DNS反应生成红棕色物质，产物在540nm处具有特征吸收峰，通过吸光值变化即可定量检测半纤维素含量。
在本申请中，木质素含量可采用乙酰化法进行检测。木质素中的酚羟基发生乙酰化后生成乙酰木质素，产物在280nm处具有特征吸收峰，通过吸光值的变化即可定量检测木质素的含量。
在本申请中，灰分含量可参照GB/T 28731-2012进行测定。
在一些实施例中，所述纤维素类生物质材料包括满足本申请上述要求的木本生物质材料中的一种或多种，可选为包括硬木、软木和坚果壳中的一种或多种，例如可以包括松木、毛竹和核桃壳中的一种或多种。
在一些实施例中，所述制备方法还包括步骤：对纤维素类生物质材料进行预处理。所述预处理工艺可包括破碎、清洗和干燥步骤。对纤维素类生物质材料进行破碎处理有助于装填料。清洗可以去除纤维素类生物质材料表面明显附着的杂质，避免其影响后续的低温预碳化处理工序。干燥可以去除纤维素类生物质材料表面附着的水分以及部分体相水分，从而降低水分对后续低温预碳化处理工序的影响。
在一些实施例中，第一升温速率为≤10℃/min，可选为1℃/min-10℃/min，1℃/min-5℃/min，1℃/min-3℃/min。第一升温速率在合适的范围内时，有助于所获得的碳质材料具有合适的水蒸气吸附速率，具有高容量、高首次库伦效率和高结构稳定性。第一升温速率太高时，制备的碳质材料的孔结构的可控性较差、毛细孔结构含量少，表现为对水蒸气吸附速率较小。
在一些实施例中，第一温度T1为150℃-1000℃，例如，第一温度T1可以为200℃，300℃，400℃，500℃，600℃，700℃，800℃，900℃，1000℃或以上任何数值组成的范 围。可选地，第一温度T1为200℃-900℃，300℃-700℃，300℃-600℃。第一温度在合适的范围内时，有助于所获得的碳质材料具有合适的水蒸气吸附速率，具有高容量、高首次库伦效率和高结构稳定性。第一温度升高，孔结构的形成更充分，毛细孔结构含量增加；但第一温度过高时，挥发分挥发速率加快，形成的孔结构尺寸变大，碳骨架结构稳定性变差，并且还会导致高温碳化处理过程中的闭孔效果差，碳质材料中的大介孔结构和/或大孔结构含量增加，碳质材料内部电解液浸润区域占比增加，首次不可逆容量损失增加，首次库伦效率降低，同时碳质材料中毛细孔结构含量减少，表现为对水蒸气吸附速率较小。
在一些实施例中，第一时间t1为1h-20h，可选为5h-20h。本领域技术人员可以根据采用的第一温度以及第一升温速率在上述范围内选择合适的第一时间，例如，在第一温度较高和/或第一升温速率较小时，第一时间可以适当缩短。
在S20中，通过调节第一升温速率、第一温度和第一时间等中的一者或者多者在上述范围内，有利于更好地调控碳骨架结构和表面，提高低温预碳化处理效果，并获得具有合适水蒸气吸附速率的碳质材料。
在一些实施例中，第二升温速率为≤10℃/min，可选为0.5℃/min-10℃/min。但本申请不限于此，第二升温速率可根据实际情况进行调整。
在一些实施例中，第二温度T2为1000℃-1600℃，例如，可以为1000℃，1050℃，1100℃，1150℃，1200℃，1250℃，1300℃，1350℃，1400℃，1450℃，1500℃，1550℃，1600℃或以上任何数值组成的范围。可选地，第二温度T2为1200℃-1500℃。第二温度在合适的范围内时，有助于所获得的碳质材料具有合适的水蒸气吸附速率，具有高容量和高首次库伦效率。第二温度较低时，碳质材料表面的含氧官能团较多，这些含氧官能团的亲水性较好，因此会使得碳质材料表现为对水蒸气吸附速率快且吸附时间短，但是此时孔结构的闭孔效果较差，碳质材料中的大介孔结构和/或大孔结构较多，进而导致碳质材料内部电解液浸润区域占比增加，首次不可逆容量损失增加，首次库伦效率降低。第二温度升高，孔结构的闭孔效果变好，由此可以降低SEI膜成膜时对活性离子消耗，并且碳质材料的活性离子储存位点增加，由此还可以使其容量和首次库伦效率增加；但第二温度过高时，会使得碳质材料微观结构发生质的变化，不利于活性离子储存，表现为对水蒸气吸附速率减小。
在一些实施例中，第二时间t2为1h-12h，可选为3h-10h。本领域技术人员可以根据采用的第二温度以及第二升温速率在上述范围内选择合适的第一时间，例如，在第二温度较高和/或第二升温速率较小时，第二时间可以适当缩短。
在S30中，通过调节第二升温速率、第二温度和第二时间等中的一者或者多者在上述范围内，有利于提高孔结构的闭孔效果，提高高温碳化处理效果，并获得具有合适水蒸气吸附速率的碳质材料。
在一些实施例中，t1+t2为10h-30h。由此有助于所获得的碳质材料具有合适的水蒸气吸附速率，具有高容量、高首次库伦效率和高结构稳定性。
在一些实施例中，在S20之后、S30之前还包括步骤：将S20所得到的第一中间产物进行破碎处理，或者将S20所得到的第一中间产物进行洗涤除杂处理，或者将S20所得到的第一中间产物进行先破碎处理后洗涤除杂处理，以得到灰分含量≤0.01wt％的第一中间 产物，所述洗涤除杂处理工艺至少包括酸性溶液洗涤步骤和碱性溶液洗涤步骤。由此，有助于进一步提升碳质材料的克容量、首次库伦效率和结构稳定性，同时还有助于降低碳质材料的真密度。
破碎处理可以降低第一中间产物的粒度，进而有助于获得所需尺寸的碳质材料。在一些实施例中，破碎后的颗粒的体积粒径Dv50为4μm-6μm。在一些实施例中，破碎后的颗粒的体积粒径Dv90为8μm-16μm。在一些实施例中，破碎后的颗粒的体积粒径Dv50为4μm-6μm且体积粒径Dv90为8μm-16μm。当然，在一些实施例中，破碎步骤也可以省略。
洗涤除杂处理可以除去第一中间产物中的无机杂质和水溶性杂质等，避免后续高温碳化处理过程中，金属杂质被还原成金属单质而后团聚。因为金属单质团聚过程中会导致碳骨架结构坍塌，尤其是毛细孔结构的坍塌，进而导致获得的碳质材料活性离子储存空间减少，容量下降；同时金属杂质还具有催化活性，将导致裂解过程中碳骨架结构分解加剧，使孔结构趋向于形成尺寸较大的大介孔结构和/或大孔结构，由此导致获得的碳质材料内部电解液浸润区域占比增加，SEI膜成膜时对活性离子的消耗增加，首次不可逆容量损失增加，首次库伦效率降低。所述洗涤除杂处理工艺至少包括酸性溶液洗涤步骤和碱性溶液洗涤步骤。酸性溶液主要用于除去第一中间产物中的金属杂质，碱性溶液主要用于除去第一中间产物中无法和酸反应的含Si杂质等，由此能够充分保证杂质的去除，降低杂质对碳质材料的不利影响，提高碳质材料的克容量和首次库伦效率。
在本申请中，破碎处理需要在洗涤除杂处理之前进行，由此以便后续洗涤除杂时，使第一中间产物暴露尽可能多的表面，以便于颗粒和洗涤液充分接触，提高洗涤除杂效果。如果破碎处理在洗涤除杂处理之后进行，有些大块的原料经热解后基本会保持原貌，洗涤液可能无法进入大块颗粒的体相中，进而大块颗粒体相中被深度包裹的杂质无法除去，由此导致洗涤除杂效果不明显。
破碎可采用本领域已知的适合在碳质材料的制备中进行破碎的工艺。在一些实施例中，所述破碎可包括球磨或者气流磨破碎。
酸性溶液洗涤和碱性溶液洗涤的顺序不受特别的限制。在一些实施例中，所述洗涤除杂处理工艺依次包括如下步骤：酸性溶液洗涤、水洗、碱性溶液洗涤、水洗以及干燥；或，所述洗涤除杂处理工艺依次包括如下步骤：碱性溶液洗涤、水洗、酸性溶液洗涤、水洗以及干燥。水洗时可采用去离子水，水洗次数可为一次或多次，直至过滤液的pH为中性(即pH为7±0.5)，认为水洗步骤完成。干燥可为鼓风干燥或真空干燥，直至间隔2h后物料的质量变化率为≤0.1wt％，认为干燥步骤完成。
本申请的对酸性溶液和碱性溶液的溶质种类、浓度、洗涤温度以及洗涤时间等参数没有特别的限制，能够保证杂质充分去除即可。
在一些实施例中，所述酸性溶液的H +浓度为0.1mol/L-6moL/L，可选为1mol/L-6moL/L。
在一些实施例中，所述酸性溶液的洗涤温度为10℃-95℃，可选为30℃-95℃。
在一些实施例中，所述酸性溶液的洗涤时间为1h-24h，可选为10h-24h。
在一些实施例中，所述酸性溶液的溶质包括盐酸、硝酸、硫酸和高氯酸中的一种或多种，溶剂包括水。
通过调节酸性溶液的H +浓度、洗涤温度、洗涤时间、溶质种类等中的一者或者多者在上述范围内，有利于实现充分洗涤，更好地除去金属杂质。
在一些实施例中，所述碱性溶液的OH -浓度为0.1mol/L-6moL/L，可选为1mol/L-6moL/L。
在一些实施例中，所述碱性溶液的洗涤温度为10℃-95℃，可选为30℃-95℃。
在一些实施例中，所述碱性溶液的洗涤时间为1h-24h，可选为10h-24h。
在一些实施例中，所述碱性溶液的溶质包括NaOH、KOH或其组合，溶剂包括水。
通过调节碱性溶液的OH -浓度、洗涤温度、洗涤时间、溶质种类等中的一者或者多者在上述范围内，有利于实现充分洗涤。
在一些实施例中，洗涤除杂处理步骤还可以省略。
在一些实施例中，当所获得的第一中间产物的灰分含量为≥0.5wt％时，需要进行洗涤除杂处理，以保证高温碳化处理前材料中的灰分含量为≤0.01wt％。
本申请对S20和S30中的保护气体气氛的种类没有特别的限制，在一些实施例中，所述保护气体包括氮气、惰性气体或其组合，可选地，所述惰性气氛包括氩气、氦气或其组合。可选地，所述气体的体积浓度可为99.9％以上。
在一些实施例中，所述制备方法还包括：S40，破碎：将S30所得到的碳质材料破碎，此时可以将制备过程中团聚的碳质材料破碎，以使其满足所需颗粒尺寸，便于制备负极浆料和负极极片。当然，在一些实施例中，该步骤可以省略。
在一些实施例中，所述制备方法包括如下步骤：提供碳源：所述碳源为纤维素类生物质材料，所述纤维素类生物质材料中的纤维素含量为大于0wt％且小于等于100wt％，且灰分含量为0wt％-5wt％；低温预碳化处理：将所述碳源在保护气体气氛下，以≤10℃/min的速率升温至150℃-1000℃，可选为300℃-700℃后保温处理1h-20h，可选为5h-20h，得到第一中间产物；高温碳化处理：将所得到的第一中间产物在保护气体气氛下，以≤10℃/min的速率升温至1000℃-1600℃，可选为1200℃-1500℃后保温处理1h-12h，可选为3h-10h，得到碳质材料，其中，所述碳质材料在25℃、40％RH恒温恒湿条件下，采用水蒸气进行吸附测试时的吸附速率v满足0.015≤v≤0.050。由此所获得的碳质材料能够更好地兼顾较高的克容量、较高的首次库伦效率和较高的结构稳定性，进而能进一步提升二次电池的能量密度、使用寿命和倍率性能。
在一些实施例中，所述制备方法包括如下步骤：提供碳源：所述碳源为纤维素类生物质材料，所述纤维素类生物质材料中的纤维素含量为大于0wt％且小于等于100wt％，且灰分含量为0wt％-5wt％；低温预碳化处理：将所述碳源在保护气体气氛下，以≤10℃/min的速率升温至150℃-1000℃，可选为300℃-700℃后保温处理1h-20h，可选为5h-20h，得到第一中间产物；高温碳化处理：将所得到的第一中间产物破碎至体积粒径Dv50为4μm-6μm和/或体积粒径Dv90为8μm-16μm后，再在保护气体气氛下，以≤10℃/min的速率升温至1000℃-1600℃，可选为1200℃-1500℃后保温处理1h-12h，可选为3h-10h，得到碳质材料，其中，所述碳质材料在25℃、40％RH恒温恒湿条件下，采用水蒸气进行吸附测试时的吸附速率v满足0.015≤v≤0.050。由此所获得的碳质材料能够更好地兼顾较高的克容量、较高的首次库伦效率和较高的结构稳定性，进而能进一步提升二次电池的能量密度、使用寿命和倍率性能。
在一些实施例中，所述制备方法包括如下步骤：提供碳源：所述碳源为纤维素类生物质材料，所述纤维素类生物质材料中的纤维素含量为大于0wt％且小于等于100wt％，且灰分含量为0wt％-5wt％；低温预碳化处理：将所述碳源在保护气体气氛下，以≤10℃/min的速率升温至150℃-1000℃，可选为300℃-700℃后保温处理1h-20h，可选为5h-20h，得到第一中间产物；高温碳化处理：将所得到的第一中间产物破碎至体积粒径Dv50为4μm-6μm和/或体积粒径Dv90为8μm-16μm后，依次经过酸性溶液洗涤、水洗、碱性溶液洗涤、水洗以及干燥步骤后，再在保护气体气氛下，以≤10℃/min的速率升温至1000℃-1600℃，可选为1200℃-1500℃后保温处理1h-12h，可选为3h-10h，得到碳质材料，其中，所述碳质材料在25℃、40％RH恒温恒湿条件下，采用水蒸气进行吸附测试时的吸附速率v满足0.015≤v≤0.050。由此所获得的碳质材料能够更好地兼顾较高的克容量、较高的首次库伦效率和较高的结构稳定性，进而能进一步提升二次电池的能量密度、使用寿命和倍率性能。
本申请实施方式第二方面的制备方法能够制备本申请实施方式第一方面任一实施例的碳质材料。本申请提供的碳质材料的制备方法工艺简单，适合商品化生产。本申请提供的碳质材料的制备方法无需额外加入导电剂，也无需额外加入其它助剂，从而通过本申请提供的制备方法所得到的碳质材料具有更低的杂原子含量。
二次电池
本申请实施方式第三方面提供一种二次电池。
本申请的实施例或实施方式中所提到的二次电池是指包括一个或多个电池单体以提供更高的电压和容量的单一的物理模块。例如，本申请中所提到的二次电池可以包括电池单体、电池模块或电池包等。电池单体是组成二次电池的最小单元，其独自能够实现充放电的功能。本申请对电池单体的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。如图1是作为一个示例的方形结构的电池单体5。
在一些实施例中，电池单体包括电极组件和电解质，单体电池还可包括外包装。外包装可用于封装电极组件及电解质。外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。外包装也可以是软包，例如袋式软包。所述软包的材质可以是塑料，如聚丙烯(PP)、聚对苯二甲酸丁二醇酯(PBT)和聚丁二酸丁二醇酯(PBS)中的一种或多种。
电极组件通常包括正极极片、负极极片等，在二次电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出，电解质在正极极片和负极极片之间起到传导活性离子的作用。电极组件可通过卷绕工艺和/或叠片工艺制成。
在一些实施例中，如图2所示，外包装可包括壳体51和盖板53。壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53用于盖设所述开口，以封闭所述容纳腔。电极组件52封装于所述容纳腔。电池单体5所含电极组件52的数量可以为一个或多个，可根据需求来调节。
在本申请的一些实施例中，电池单体可以组装成电池模块，电池模块所含电池单体的数量可以为多个，具体数量可根据电池模块的应用和容量来调节。图3是作为一个示例的电池模块4的示意图。如图3所示，在电池模块4中，多个电池单体5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个电池单体5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个电池单体5容纳于该容纳空间。
在一些实施例中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以根据电池包的应用和容量进行调节。图4和图5是作为一个示例的电池包1的示意图。如图4和图5所示，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2用于盖设下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
[负极极片]
在一些实施例中，所述负极极片包括负极集流体以及设置在所述负极集流体至少一个表面上的负极膜层。例如，所述负极集流体具有在自身厚度方向相对的两个表面，所述负极膜层设置在所述负极集流体的两个相对表面中的任意一者或两者上。
在一些实施例中，所述负极膜层包括本申请实施方式第一方面的碳质材料或通过本申请实施方式第二方面所述的方法制备得到的碳质材料。由此能使二次电池同时具有高能量密度、长使用寿命和良好的倍率性能。
在一些实施例中，所述负极膜层还可以进一步包括除了上述碳质材料以外的其他负极活性材料。在一些实施例中，所述其他负极活性材料包括但不限于天然石墨、人造石墨、软炭、硅基材料、锡基材料和钛酸锂中的一种或多种。所述硅基材料可包括单质硅、硅氧化物、硅碳复合物、硅氮复合物和硅合金材料中的一种或多种。所述锡基材料可包括单质锡、锡氧化物和锡合金材料中的一种或多种。
在一些实施例中，所述负极膜层还可选地包括负极导电剂。本申请对所述负极导电剂的种类没有特别的限制，作为示例，所述负极导电剂可包括超导碳、导电石墨、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯和碳纳米纤维中的一种或多种。
在一些实施例中，所述负极膜层还可选地包括负极粘结剂。本申请对所述负极粘结剂的种类没有特别的限制，作为示例，所述负极粘结剂可包括丁苯橡胶(SBR)、水溶性不饱和树脂SR-1B、水性丙烯酸类树脂(例如，聚丙烯酸PAA、聚甲基丙烯酸PMAA、聚丙烯酸钠PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)和羧甲基壳聚糖(CMCS)中的一种或多种。
在一些实施例中，所述负极膜层还可选地包括其他助剂。作为示例，其他助剂可包括增稠剂，例如，羧甲基纤维素钠(CMC)、PTC热敏电阻材料等。
在一些实施例中，所述负极集流体可采用金属箔片或复合集流体。作为金属箔片的示例，可采用铜箔。所述复合集流体可包括高分子材料基层以及形成于所述高分子材料基层至少一个表面上的金属材料层。作为示例，所述金属材料可包括铜、铜合金、镍、镍合金、钛、钛合金、银和银合金中的一种或多种。作为示例，所述高分子材料基层可包括聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)和聚乙烯(PE)中的一种或多种。
所述负极膜层通常是将负极浆料涂布在负极集流体上，经干燥、冷压而成的。所述负极浆料通常是将负极活性材料、可选的导电剂、可选的粘结剂、其他可选的助剂分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)或去离子水，但不限于此。
所述负极极片并不排除除了所述负极膜层之外的其他附加功能层。例如，在一些实施例中，本申请所述的负极极片还包括夹在所述负极集流体和所述负极膜层之间、设置在所述负极集流体表面的导电底涂层(例如由导电剂和粘结剂组成)；在一些实施例中，本申请所述的负极极片还包括覆盖在所述负极膜层表面的保护层。
[正极极片]
在一些实施例中，所述正极极片包括正极集流体以及设置在所述正极集流体至少一个表面的正极膜层。例如，所述正极集流体具有在自身厚度方向相对的两个表面，所述正极膜层设置于所述正极集流体的两个相对表面中的任意一者或两者上。
所述正极集流体可采用金属箔片或复合集流体。作为金属箔片的示例，可采用铝箔。所述复合集流体可包括高分子材料基层以及形成于所述高分子材料基层至少一个表面上的金属材料层。作为示例，所述金属材料可包括铝、铝合金、镍、镍合金、钛、钛合金、银和银合金中的一种或多种。作为示例，所述高分子材料基层可包括聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)和聚乙烯(PE)中的一种或多种。
所述正极膜层通常包含正极活性材料、可选的粘结剂和可选的导电剂。所述正极膜层通常是将正极浆料涂布在所述正极集流体上，经干燥、冷压而成的。所述正极浆料通常是将正极活性材料、可选的导电剂、可选的粘结剂以及任意的其他组分分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)，但不限于此。作为示例，用于正极膜层的粘结剂可包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物和含氟丙烯酸酯树脂中的一种或多种。作为示例，用于正极膜层的导电剂包括超导碳、导电石墨、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯和碳纳米纤维中的一种或多种。
所述正极活性材料可采用本领域公知的用于二次电池的正极活性材料。
当本申请的二次电池为锂离子电池时，所述正极活性材料所述正极活性材料可包括但不限于含锂过渡金属氧化物、含锂磷酸盐及其各自的改性化合物中的一种或多种。所述锂过渡金属氧化物的示例可包括但不限于锂钴氧化物、锂镍氧化物、锂锰氧化物、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物、锂镍钴铝氧化物及其各自的改性化合物中的一种或多种。所述含锂磷酸盐的示例可包括但不限于磷酸铁锂、磷酸铁锂与碳的复合材料、磷酸锰锂、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料及其各自的改性化合物中的一种或多种。
在一些实施例中，为了进一步提高二次电池的能量密度，用于锂离子电池的正极活性材料可以包括通式为Li aNi bCo cM dO eA f的锂过渡金属氧化物及其改性化合物中的一种或多种。0.8≤a≤1.2，0.5≤b＜1，0＜c＜1，0＜d＜1，1≤e≤2，0≤f≤1，M包括选自Mn、Al、Zr、Zn、Cu、Cr、Mg、Fe、V、Ti和B中的一种或多种，A包括选自N、F、S和Cl中的一种或多种。
作为示例，用于锂离子电池的正极活性材料可包括LiCoO 2、LiNiO 2、LiMnO 2、LiMn 2O 4、LiNi 1/3Co 1/3Mn 1/3O 2(NCM333)、LiNi 0.5Co 0.2Mn 0.3O 2(NCM523)、LiNi 0.6Co 0.2Mn 0.2O 2(NCM622)、LiNi 0.8Co 0.1Mn 0.1O 2(NCM811)、LiNi 0.85Co 0.15Al 0.05O 2、 LiFePO 4和LiMnPO 4中的一种或多种。
当本申请的二次电池为钠离子电池时，所述正极活性材料可包括但不限于含钠过渡金属氧化物、聚阴离子材料(如磷酸盐、氟磷酸盐、焦磷酸盐、硫酸盐等)、普鲁士蓝类材料中的一种或多种。
作为示例，用于钠离子电池的正极活性材料可包括NaFeO 2、NaCoO 2、NaCrO 2、NaMnO 2、NaNiO 2、NaNi 1/2Ti 1/2O 2、NaNi 1/2Mn 1/2O 2、Na 2/3Fe 1/3Mn 2/3O 2、NaNi 1/3Co 1/3Mn 1/3O 2、NaFePO 4、NaMnPO 4、NaCoPO 4、普鲁士蓝类材料和通式为X pM’ q(PO 4) rO xY 3-x的材料中的一种或多种。在通式X pM’ q(PO 4) rO xY 3-x中，0＜p≤4，0＜q≤2，1≤r≤3，0≤x≤2，X包括选自H +、Li +、Na +、K +和NH 4 +中的一种或多种，M’为过渡金属阳离子，可选地为包括选自V、Ti、Mn、Fe、Co、Ni、Cu和Zn中的一种或多种，Y为卤素阴离子，可选地为包括选自F、Cl和Br中的一种或多种。
在本申请中，上述各正极活性材料的改性化合物可以是对所述正极活性材料进行掺杂改性和/或表面包覆改性。
[电解质]
本申请对所述电解质的种类没有特别的限制，可根据实际需求进行选择。例如，所述电解质可以选自固态电解质及液态电解质(即电解液)中的至少一种。
在一些实施例中，所述电解质采用电解液，所述电解液包括电解质盐和溶剂。
所述电解质盐的种类不受具体的限制，可根据实际需求进行选择。
当本申请的二次电池为锂离子电池时，作为示例，所述电解质盐可包括六氟磷酸锂(LiPF 6)、四氟硼酸锂(LiBF 4)、高氯酸锂(LiClO 4)、六氟砷酸锂(LiAsF 6)、双氟磺酰亚胺锂(LiFSI)、双三氟甲磺酰亚胺锂(LiTFSI)、三氟甲磺酸锂(LiTFS)、二氟草酸硼酸锂(LiDFOB)、二草酸硼酸锂(LiBOB)、二氟磷酸锂(LiPO 2F 2)、二氟二草酸磷酸锂(LiDFOP)和四氟草酸磷酸锂(LiTFOP)中的一种或多种。
当本申请的二次电池为钠离子电池时，所述电解质盐可包括六氟磷酸钠(NaPF 6)、四氟硼酸钠(NaBF 4)、高氯酸钠(NaClO 4)、六氟砷酸钠(NaAsF 6)、双氟磺酰亚胺钠(NaFSI)、双三氟甲磺酰亚胺钠(NaTFSI)、三氟甲磺酸钠(NaTFS)、二氟草酸硼酸钠(NaDFOB)、二草酸硼酸钠(NaBOB)、二氟磷酸钠(NaPO 2F 2)、二氟二草酸磷酸钠(NaDFOP)和四氟草酸磷酸钠(NaTFOP)中的一种或多种。
所述溶剂的种类不受具体的限制，可根据实际需求进行选择。在一些实施例中，作为示例，所述溶剂可包括碳酸乙烯酯(EC)、碳酸亚丙酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸亚丁酯(BC)、氟代碳酸乙烯酯(FEC)、甲酸甲酯(MF)、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(PA)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸丙酯(PP)、丁酸甲酯(MB)、丁酸乙酯(EB)、1,4-丁内酯(GBL)、环丁砜(SF)、二甲砜(MSM)、甲乙砜(EMS)和二乙砜(ESE)中的一种或多种。
在一些实施例中，所述电解液还可选地包括添加剂。例如，所述添加剂可以包括负极成膜添加剂，也可以包括正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温性能的添加剂、改善电池低温功率 性能的添加剂等。
[隔离膜]
采用电解液的二次电池、以及一些采用固态电解质的二次电池中，还包括隔离膜。所述隔离膜设置在所述正极极片和所述负极极片之间，起到隔离的作用。本申请对所述隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施例中，所述隔离膜的材质可以包括玻璃纤维、无纺布、聚乙烯、聚丙烯和聚偏二氟乙烯中的一种或多种。所述隔离膜可以是单层薄膜，也可以是多层复合薄膜。所述隔离膜为多层复合薄膜时，各层的材料相同或不同。
[制备方法]
本申请的二次电池的制备方法是公知的。在一些实施例中，可将正极极片、隔离膜、负极极片和电解液组装形成二次电池。作为示例，可将正极极片、隔离膜、负极极片经卷绕工艺和/或叠片工艺形成电极组件，将电极组件置于外包装中，烘干后注入电解液，经过真空封装、静置、化成、整形等工序，得到电池单体。多个电池单体还可以进一步经由串联或并联或混联组成电池模块。多个电池模块还可以经由串联或并联或混联形成电池包。在一些实施例中，多个电池单体还可以直接组成电池包。
用电装置
本申请实施方式第四方面提供一种用电装置，所述用电装置包括本申请的二次电池。所述二次电池可以用作所述用电装置的电源，也可以用作所述用电装置的能量存储单元。所述用电装置可以但不限于是移动设备(例如手机、平板电脑、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等。
所述用电装置可以根据其使用需求来选择二次电池的具体类型，例如电池单体、电池模块或电池包。
图6是作为一个示例的用电装置的示意图。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对高功率和高能量密度的需求，可以采用电池包或电池模块作为电源。
作为另一个示例的用电装置可以是手机、平板电脑、笔记本电脑等。该用电装置通常要求轻薄化，可以采用电池单体作为电源。
实施例
下述实施例更具体地描述了本申请公开的内容，这些实施例仅仅用于阐述性说明，因为在本申请公开内容的范围内进行各种修改和变化对本领域技术人员来说是明显的。除非另有声明，以下实施例中所报道的所有份、百分比、和比值都是基于质量计，而且实施例中使用的所有试剂都可商购获得或是按照常规方法进行合成获得，并且可直接使用而无需进一步处理，以及实施例中使用的仪器均可商购获得。
实施例1
以松木作为碳源，颗粒尺寸为≤1mm，纤维素含量为40wt％，半纤维素含量为23％，木质素含量为27％，灰分含量为1wt％。
将松木在氮气气氛下，以1℃/min(作为第一升温速率)升温至150℃(作为第一温度T1)后保温处理10h(第一时间t1)，结束后冷却至室温得到第一中间产物。
将第一中间产物采用气流磨破碎至体积粒径Dv50为4μm-6μm，之后使用3mol/L的高氯酸水溶液在50℃下洗涤10h，之后使用去离子水洗涤至中性，再用3mol/L的NaOH水溶液在80℃下洗涤20h，再使用去离子水洗涤至中性，最后鼓风干燥除去水分，得到灰分含量为≤0.01wt％的第一中间产物。
将上述所得到的第一中间产物在氮气气氛下，以0.5℃/min(作为第二升温速率)升温至1400℃(作为第二温度T2)后保温处理6h(作为第二时间t2)，结束后得到碳质材料。
在25℃、40％RH(即空气中水蒸气分压与水的饱和蒸气压的比值为40％)的恒温恒湿箱中，将质量为m 1的碳质材料均匀放置在容器中且所述碳质材料的堆积厚度为≤5mm，记录碳质材料吸附水蒸气达到平衡时的水蒸气吸附质量m 2与水蒸气吸附时间t，则水蒸气吸附速率v＝m 2/(m 1×t)，m 1的计量单位为g，m 2的计量单位为g，t的计量单位为h。
采用阿基米德浸渍体积置换法，以正丁醇为介质测试碳质材料的真密度。
实施例2-19和对比例1-7
碳质材料的制备方法与实施例1类似，不同之处在于调整了碳质材料的制备工艺参数，具体详见表1。
性能测试
将各实施例和对比例制备的碳质材料与粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC-Na)、导电剂炭黑按照质量比96.2:1.8:1.2:0.8在适量的溶剂去离子水中充分搅拌混合，形成均匀的负极浆料；将负极浆料均匀涂覆于负极集流体铜箔的表面上，于烘箱中干燥后备用。将碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)按照体积比1:1:1进行混合得到有机溶剂，然后将NaPF 6溶解于上述有机溶剂中，配制成浓度为1mol/L的电解液。之后以金属钠片为对电极，聚乙烯(PE)薄膜作为隔离膜，在氩气保护的手套箱组装成CR2430型扣式电池。
在25℃下，首先以10mA/g的电流密度将各实施例和对比例制备的扣式电池恒流放电至0V，记录扣式电池的首圈放电容量；之后以10mA/g的电流密度恒流充电至2.0V，记录扣式电池的首圈充电容量。
碳质材料的可逆克容量(mAh/g)＝扣式电池的首圈充电容量/碳质材料的质量。
碳质材料的首次库伦效率(％)＝扣式电池的首圈充电容量/扣式电池的首圈放电容量×100％。
将扣式电池分别以0.33C和1C进行满充和满放后，得到0.33C和1C下的放电容量，以1C下的放电容量与0.33C下的放电容量的比值表征倍率性能，该比值越高，表明倍率性能越好。
表1
Figure PCTCN2022126836-appb-000001
Figure PCTCN2022126836-appb-000002
表2
Figure PCTCN2022126836-appb-000003
Figure PCTCN2022126836-appb-000004
图7至图9是本申请提供的碳质材料在不同放大倍数下的扫描电子显微镜图，如图7至图9所示，本申请提供的碳质材料的形貌为无规则的多棱角形。综合表2测试结果可知，当碳质材料满足25℃、40％RH恒温恒湿条件下，水蒸气吸附速率v在0.015至0.050之间时，碳质材料兼顾较高的克容量、较高的首次库伦效率以及良好的倍率性能。
对比例1-7制备得到的碳质材料在25℃、40％RH恒温恒湿条件下，水蒸气吸附速率v或者小于0.015，或者大于0.050，由此均不能使碳质材料兼顾较高的克容量、较高的首次库伦效率以及良好的倍率性能。
对比例1采用稻壳作为碳源，其灰分含量高于5wt％。由于灰分不仅会在低温预碳化处理过程中产生催化反应，消耗C元素含量，减少活性离子储存位点，而且还会在后续高温碳化处理过程中，使灰分中的金属杂质还原成金属单质而后团聚，金属单质团聚时会导致碳骨架结构坍塌，尤其是毛细孔结构的坍塌，进而导致获得的碳质材料活性离子储存空间减少，容量下降，表现为对水蒸气吸附速率过小。同时金属杂质还具有催化活性，将导致裂解过程中碳骨架结构分解加剧，使孔结构趋向于形成尺寸较大的大介孔结构和/或大孔结构，由此导致获得的碳质材料内部电解液浸润区域占比增加，SEI膜成膜时对活性离子的消耗增加，首次不可逆容量损失增加，首次库伦效率降低。
对比例2在制备碳质材料时，未进行低温预碳化处理，由此导致碳质材料的闭孔效果差，毛细孔结构含量少且大介孔结构和/或大孔结构含量高，进而碳质材料内部电解液浸润区域占比高，首次不可逆容量损失高，首次库伦效率低。
综合实施例1-19的测试结果还可知，当碳质材料的水蒸气吸附时间t进一步满足在4.5h至7h之间时，碳质材料能够具有更高的克容量、首次库伦效率和/或倍率性能。
综合实施例1-19的测试结果还可知，当碳质材料的真密度ρ进一步满足在1.3g/cm 3-1.7g/cm 3之间时，碳质材料能够具有更高的克容量、首次库伦效率和/或倍率性能。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。

Claims (21)

  1. 一种碳质材料，其中，所述碳质材料在25℃、40％RH恒温恒湿条件下，采用水蒸气进行吸附测试时的吸附速率v满足0.015≤v≤0.050，
    所述水蒸气吸附测试在如下条件下进行：在25℃、40％RH的恒温恒湿箱中，将质量为m 1的所述碳质材料放置在容器中，记录所述碳质材料吸附水蒸气达到平衡时的水蒸气吸附质量m 2与水蒸气吸附时间t，则水蒸气吸附速率v＝m 2/(m 1×t)，m 1的计量单位为g，m 2的计量单位为g，t的计量单位为h。
  2. 根据权利要求1所述的碳质材料，其中，0.020≤v≤0.050。
  3. 根据权利要求1或2所述的碳质材料，其中，所述碳质材料吸附水蒸气达到平衡时的水蒸气吸附时间t为1h-12h，可选为4.5h-7h。
  4. 根据权利要求1-3任一项所述的碳质材料，其中，所述碳质材料的真密度ρ为1.0g/cm 3-2.2g/cm 3，可选为1.3g/cm 3-1.7g/cm 3。
  5. 根据权利要求1-4任一项所述的碳质材料，其中，所述碳质材料包括多个纳米孔结构，可选地，所述碳质材料包括多个孔径在10nm以下的孔结构。
  6. 根据权利要求1-5任一项所述的碳质材料，其中，
    在所述碳质材料的拉曼光谱中，I d/I g为1.0-1.3，可选为1.05-1.15，I d表示拉曼位移在1350±50cm -1范围内的d峰强度，I g表示拉曼位移在1580±50cm -1范围内的g峰强度；和/或，
    所述碳质材料的(002)晶面的层间距为≥0.37nm，可选为0.37nm-0.42nm；和/或，
    在所述碳质材料的X射线衍射谱中，(002)晶面峰对应的2θ值在22°至24°之间。
  7. 根据权利要求1-6任一项所述的碳质材料，其中，所述碳质材料满足如下条件(1)至(5)中的至少一者：
    (1)所述碳质材料的体积粒径Dv50为4μm-6μm；
    (2)所述碳质材料的体积粒径Dv90为8μm-16μm；
    (3)所述碳质材料的比表面积为0.1m 2/g-20m 2/g，可选为1m 2/g-20m 2/g；
    (4)所述碳质材料在50000N作用力下的粉体压实密度为0.90g/cm 3-1.05g/cm 3，可选为0.92g/cm 3-1.02g/cm 3；
    (5)所述碳质材料的振实密度为0.78g/cm 3-0.95g/cm 3，可选为0.83g/cm 3-0.93g/cm 3。
  8. 一种碳质材料的制备方法，包括如下步骤：
    S10，提供碳源：所述碳源为纤维素类生物质材料；
    S20，低温预碳化处理：将所述碳源在保护气体气氛下，以第一升温速率升温至第一温度T1后保温处理第一时间t1，得到第一中间产物；
    S30，高温碳化处理：将所得到的第一中间产物在保护气体气氛下，以第二升温速率升温至第二温度T2后保温处理第二时间t2，得到碳质材料，其中，所述碳质材料在25℃、40％RH恒温恒湿条件下，采用水蒸气进行吸附测试时的吸附速率v满足0.015≤v≤0.050，所述水蒸气吸附测试在如下条件下进行：在25℃、40％RH的恒温恒湿箱中，将质量为m 1的所述碳质材料放置在容器中，记录所述碳质材料吸附水蒸气达到平衡时的水蒸气吸附 质量m 2与水蒸气吸附时间t，则水蒸气吸附速率v＝m 2/(m 1×t)，m 1的计量单位为g，m 2的计量单位为g，t的计量单位为h。
  9. 根据权利要求8所述的方法，其中，所述纤维素类生物质材料中的纤维素含量为大于0wt％且小于等于100wt％，且灰分含量为0wt％-5wt％。
  10. 根据权利要求8或9所述的方法，其中，
    所述纤维素类生物质材料中的纤维素含量为大于等于20wt％且小于100wt％；和/或，
    所述纤维素类生物质材料中的灰分含量为0wt％-2wt％。
  11. 根据权利要求9或10所述的方法，其中，
    所述纤维素类生物质材料中的半纤维素含量为0wt％-70wt％，可选为0wt％-30wt％；和/或，
    所述纤维素类生物质材料中的木质素含量为0wt％-60wt％，可选为10wt％-60wt％。
  12. 根据权利要求9-11任一项所述的方法，其中，所述纤维素类生物质材料包括木本生物质材料中的一种或多种，可选为包括硬木、软木和坚果壳中的一种或多种，更可选为包括松木、毛竹和核桃壳中的一种或多种。
  13. 根据权利要求8-12任一项所述的方法，其中，
    第一升温速率为1℃/min-10℃/min，可选为1℃/min-3℃/min；和/或，
    第一温度T1为150℃-1000℃，可选为300℃-700℃；和/或，
    第一时间t1为1h-20h，可选为5h-20h。
  14. 根据权利要求8-13任一项所述的方法，其中，
    第二升温速率为≤10℃/min，可选为0.5℃/min-10℃/min；和/或，
    第二温度T2为1000℃-1600℃，可选为1200℃-1500℃；和/或，
    第二时间t2为1h-12h，可选为3h-10h。
  15. 根据权利要求8-14任一项所述的方法，其中，t1+t2为10h-30h。
  16. 根据权利要求8-15任一项所述的方法，其中，在S20之后、S30之前还包括步骤：将S20所得到的第一中间产物进行破碎处理，或者将S20所得到的第一中间产物进行洗涤除杂处理，或者将S20所得到的第一中间产物进行先破碎处理后洗涤除杂处理，以得到灰分含量≤0.01wt％的第一中间产物，所述洗涤除杂处理工艺至少包括酸性溶液洗涤步骤和碱性溶液洗涤步骤。
  17. 根据权利要求16所述的方法，其中，所述洗涤除杂处理工艺依次包括如下步骤：酸性溶液洗涤、水洗、碱性溶液洗涤、水洗以及干燥；或，所述洗涤除杂处理工艺依次包括如下步骤：碱性溶液洗涤、水洗、酸性溶液洗涤、水洗以及干燥。
  18. 根据权利要求16或17所述的方法，其中，所述酸性溶液满足如下条件(1)至(4)中的至少一者：
    (1)所述酸性溶液的H +浓度为0.1mol/L-6moL/L，可选为1mol/L-6moL/L；
    (2)所述酸性溶液的洗涤温度为10℃-95℃，可选为30℃-95℃；
    (3)所述酸性溶液的洗涤时间为1h-24h，可选为10h-24h；
    (4)所述酸性溶液的溶质包括盐酸、硝酸、硫酸和高氯酸中的一种或多种，溶剂包括水。
  19. 根据权利要求16-18任一项所述的方法，其中，所述碱性溶液满足如下条件(1)至(4)中的至少一者：
    (1)所述碱性溶液的OH -浓度为0.1mol/L-6moL/L，可选为1mol/L-6moL/L；
    (2)所述碱性溶液的洗涤温度为10℃-95℃，可选为30℃-95℃；
    (3)所述碱性溶液的洗涤时间为1h-24h，可选为10h-24h；
    (4)所述碱性溶液的溶质包括NaOH、KOH或其组合，溶剂包括水。
  20. 一种二次电池，包括负极极片，所述负极极片包括权利要求1-7任一项所述的碳质材料或通过权利要求8-19任一项所述的方法制备得到的碳质材料。
  21. 一种用电装置，包括权利要求20所述的二次电池。
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