Carbonaceous material, method for preparing same, and secondary battery and electric device comprising same

Abstract

The invention relates to a carbonaceous material and a preparation method thereof, and a secondary battery and an electric device containing the carbonaceous material, the adsorption rate v of the carbonaceous material during an adsorption test by using water vapor under the constant temperature and humidity conditions of 25 basketry and 40% RH meets 0.015 sgvsg 0.050, and the water vapor adsorption test is carried out under the following conditions: in a constant temperature and humidity chamber of 25 basketry and 40% RH, the adsorption rate v meets 0.015 sgvsg 0.050; a carbonaceous material with the mass of m1 is placed in a container, the water vapor adsorption mass m2 and the water vapor adsorption time t when the carbonaceous material adsorbs water vapor to be balanced are recorded, the water vapor adsorption rate v is equal to m2 / (m1Xt), the metering unit of m1 is g, the metering unit of m2 is g, and the metering unit of t is h. The carbonaceous material can give consideration to relatively high gram volume, relatively high first coulombic efficiency and relatively high structural stability.

Description

Carbonaceous material and preparation method thereof, as well as secondary battery and electric device containing same Technical Field

[0001] 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. Background Art

[0002] In recent years, secondary batteries have been widely used in energy storage systems such as hydropower, thermal, wind, and solar power stations, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields. With the application and promotion of secondary batteries, their energy density, service life, and rate performance have received increasing attention. Graphite is the most commonly used negative electrode active material for secondary batteries, but its theoretical gram capacity is only 372 mAh / g, which limits the potential for energy density improvement. Furthermore, the small interlayer spacing of graphite also limits rate performance improvements. As a new type of negative electrode active material, hard carbon has great potential for development because it can rapidly embed and extract active ions during the charge and discharge process of secondary batteries. However, hard carbon has low gram capacity and initial coulombic efficiency, which limits its potential to improve the energy density, service life, and rate performance of secondary batteries.

[0003] Summary of the Invention

[0004] 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.

[0005] The first aspect of the present application provides a carbonaceous material, wherein the adsorption rate v of the carbonaceous material when subjected to an adsorption test using water vapor under constant temperature and humidity conditions of 25°C and 40% RH 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 chamber at 25°C and 40% RH, the carbonaceous material with a mass of m1 is placed in a container, and 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, then the water vapor adsorption rate v = m2 / (m1×t), the unit of measurement of m1 is g, the unit of measurement of m2 is g, and the unit of measurement of t is h.

[0006] Compared with currently commercialized carbonaceous materials, the carbonaceous material provided by the present 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. Although the mechanism is not clear, the inventors of the present application speculate that one possible reason is that when the water vapor adsorption rate v is between 0.015 and 0.050, the structural stability of the carbonaceous material of the present application is high and it has a unique pore structure, which can facilitate the embedding, storage and extraction of active ions, and thus the carbonaceous material of the present 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.

[0007] In any embodiment of the present application, 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.

[0008] In any embodiment of the present application, the water vapor adsorption time t when the carbonaceous material adsorbs water vapor to reach equilibrium is 1 hour to 12 hours, and can be optionally 4.5 hours to 7 hours. When 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 coulombic efficiency, and structural stability of the carbonaceous material, thereby further improving the energy density, service life, and rate performance of the secondary battery.

[0009] In any embodiment of the present application, the true density ρ of the carbonaceous material is 1.0 g / cm 3 -2.2g / cm 3 , optional 1.3g / cm 3 -1.7g / cm 3 When the true density of the carbonaceous material meets the above-mentioned specific range, it helps to further improve the gram capacity and the first coulombic efficiency of the carbonaceous material.

[0010] In any embodiment of the present application, the carbonaceous material includes a plurality of nanoporous structures. Optionally, the carbonaceous material includes a plurality of pore structures with a pore diameter of less than 10 nm.

[0011] In any embodiment of the present application, in the Raman spectrum of the carbonaceous material, I d / I g 1.0-1.3, optional 1.05-1.15, I d Indicates that the Raman shift is 1350±50cm -1 d peak intensity in the range, I g Indicates that the Raman shift is 1580±50cm -1At this point, the carbonaceous material has higher gram capacity and higher first coulombic efficiency, as well as good rate performance.

[0012] In any embodiment of the present application, 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.

[0013] In any embodiment of the present application, in the X-ray diffraction spectrum of the carbonaceous material, the 2θ value corresponding to the (002) crystal plane peak is between 22° and 24°.

[0014] In any embodiment of the present application, the volume particle size Dv50 of the carbonaceous material is 4 μm-6 μm.

[0015] In any embodiment of the present application, the volume particle size Dv90 of the carbonaceous material is 8 μm-16 μm.

[0016] When the 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.

[0017] In any embodiment of the present application, the specific surface area of ​​the carbonaceous material is 0.1m 2 / g-20m 2 / g, optional 1m 2 / g-20m 2 When the specific surface area of ​​the carbonaceous material is within a suitable range, the carbonaceous material can simultaneously have higher gram capacity and first coulombic efficiency, as well as better rate performance.

[0018] In any embodiment of the present application, the powder compaction density of the carbonaceous material under a force of 50,000 N is 0.90 g / cm 3 -1.05g / cm 3 , optional 0.92g / cm 3 -1.02g / cm 3 When the compaction density of the carbonaceous material powder is within an appropriate range, the compaction density of the negative electrode sheet can be increased, thereby increasing the energy density of the secondary battery.

[0019] In any embodiment of the present application, the tap density of the carbonaceous material is 0.78 g / cm 3 -0.95g / cm 3 , optional 0.83g / cm 3 -0.93g / cm 3When the tap density of the carbonaceous material is within an appropriate range, the compaction density of the negative electrode sheet can be increased, thereby increasing the energy density of the secondary battery.

[0020] 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 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 for a second time t2 to obtain a carbonaceous material, wherein the carbonaceous material is heated to a temperature of 2 Under the constant temperature and humidity conditions of 5°C and 40% RH, the adsorption rate v when water vapor is used for adsorption test satisfies 0.015≤v≤0.050. The water vapor adsorption test is carried out under the following conditions: in a constant temperature and humidity chamber at 25°C and 40% RH, the carbonaceous material with a mass of m1 is placed in a container, and 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.

[0021] The carbonaceous material obtained by the preparation method provided in this application can achieve a high gram capacity, a high first coulombic efficiency, and high structural stability, thereby enabling secondary batteries to simultaneously possess high energy density, long service life, and good rate performance. Furthermore, compared to existing commercial hard carbon, the gram capacity, first coulombic efficiency, and rate performance of the carbonaceous material obtained by the preparation method of this application are significantly improved.

[0022] In any embodiment of the present application, 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%.

[0023] In any embodiment of the present application, 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%.

[0024] In any embodiment of the present application, 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%-2 wt%.

[0025] In any embodiment of the present application, 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%.

[0026] In any embodiment of the present application, the hemicellulose content in the cellulose biomass material is 0 wt%-70 wt%, optionally 0 wt%-30 wt%.

[0027] In any embodiment of the present application, the lignin content in the cellulosic biomass material is 0 wt%-60 wt%, optionally 10 wt%-60 wt%.

[0028] By adjusting the content of one or more of cellulose, ash, hemicellulose and lignin in the cellulosic biomass material to meet the above range, 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.

[0029] In any embodiment of the present application, the cellulosic biomass material includes one or more woody biomass materials, which can be selected from one or more of hardwood, softwood and nut shells, and more preferably one or more of pine, bamboo and walnut shells.

[0030] In any embodiment of the present application, the first heating rate is 1° C. / min-10° C. / min, and can be optionally 1° C. / min-3° C. / min.

[0031] In any embodiment of the present application, the first temperature T1 is 150°C-1000°C, and can be optionally 300°C-700°C.

[0032] In any embodiment of the present application, the first time t1 is 1 hour to 20 hours, and can be optionally 5 hours to 20 hours.

[0033] In S20, by adjusting one or more of the first heating rate, the first temperature and the first time within the above range, it is beneficial to better regulate the carbon skeleton structure and surface, improve the low-temperature pre-carbonization treatment effect, and obtain a carbonaceous material with a suitable water vapor adsorption rate.

[0034] In any embodiment of the present application, the second heating rate is ≤10°C / min, and can be optionally 0.5°C / min-10°C / min.

[0035] In any embodiment of the present application, the second temperature T2 is 1000°C-1600°C, and can be optionally 1200°C-1500°C.

[0036] In any embodiment of the present application, the second time t2 is 1 hour to 12 hours, and can be optionally 3 hours to 10 hours.

[0037] In S30, by adjusting one or more of the second heating rate, the second temperature and the second time within the above range, it is beneficial to improve the closed-pore effect of the pore structure, improve the high-temperature carbonization treatment effect, and obtain a carbonaceous material with a suitable water vapor adsorption rate.

[0038] In any embodiment of the present application, 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.

[0039] In any embodiment of the present application, after S20 and before S30, the method further includes the steps of: crushing the first intermediate product obtained in S20, or washing and removing impurities on the first intermediate product obtained in S20, or first crushing the first intermediate product obtained in S20 and then washing and removing impurities on the first intermediate product obtained in S20, so as 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.

[0040] In any embodiment of the present application, 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.

[0041] In any embodiment of the present application, the H of the acidic solution + The concentration is 0.1mol / L-6moL / L, and can be selected as 1mol / L-6moL / L.

[0042] In any embodiment of the present application, the washing temperature of the acidic solution is 10°C-95°C, optionally 30°C-95°C.

[0043] In any embodiment of the present application, the washing time of the acidic solution is 1 hour to 24 hours, and can be optionally 10 hours to 24 hours.

[0044] In any embodiment of the present application, 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.

[0045] By adjusting the H + One or more of the concentration, washing temperature, washing time, solute type, etc. being within the above range is conducive to achieving sufficient washing and better removal of metal impurities.

[0046] In any embodiment of the present application, the OH of the alkaline solution - The concentration is 0.1mol / L-6moL / L, and can be selected as 1mol / L-6moL / L.

[0047] In any embodiment of the present application, the washing temperature of the alkaline solution is 10°C-95°C, optionally 30°C-95°C.

[0048] In any embodiment of the present application, the washing time of the alkaline solution is 1 hour to 24 hours, and can be optionally 10 hours to 24 hours.

[0049] In any embodiment of the present application, the solute of the alkaline solution includes NaOH, KOH or a combination thereof, and the solvent includes water.

[0050] By adjusting the OH - When one or more of the concentration, washing temperature, washing time, solute type, etc. are within the above range, it is beneficial to achieve sufficient washing.

[0051] A third aspect of the present application provides a secondary battery comprising a negative electrode plate, wherein the negative electrode plate comprises 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.

[0052] A fourth aspect of the present application provides an electrical device comprising the secondary battery of the third aspect of the present application.

[0053] The carbonaceous materials provided herein are capable of achieving a high gram capacity, a high initial coulombic efficiency, and high structural stability, thereby enabling secondary batteries to simultaneously possess high energy density, a long service life, and good rate performance. The electrical device of the present application includes the secondary battery provided herein, and thus has at least the same advantages as the aforementioned secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] To more clearly illustrate the technical solutions of the embodiments of this application, the following briefly describes the drawings required for use in the embodiments of this application. Obviously, the drawings described below are merely some embodiments of this application. Those skilled in the art can derive other drawings based on the drawings without inventive effort.

[0055] FIG1 is a schematic diagram of a battery cell according to an embodiment of the present application.

[0056] FIG2 is an exploded schematic diagram of an embodiment of a battery cell of the present application.

[0057] FIG3 is a schematic diagram of an embodiment of a battery module of the present application.

[0058] FIG4 is a schematic diagram of an embodiment of a battery pack of the present application.

[0059] FIG. 5 is an exploded schematic diagram of the embodiment of the battery pack shown in FIG. 4 .

[0060] FIG6 is a schematic diagram of an embodiment of an electric device including the secondary battery of the present application as a power source.

[0061] 7 to 9 are scanning electron microscope images of the carbonaceous material provided in this application at different magnifications.

[0062] In the accompanying drawings, which are not necessarily drawn to scale, reference numerals are as follows: 1 battery pack, 2 upper housing, 3 lower housing, 4 battery module, 5 battery cell, 51 housing, 52 electrode assembly, 53 cover plate. DETAILED DESCRIPTION

[0063] Hereinafter, the carbonaceous material and its preparation method, as well as the secondary battery and the electric device containing the carbonaceous material of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0064] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this 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.

[0065] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0066] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of this application.

[0067] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, 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.

[0068] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0069] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: 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).

[0070] Unless otherwise specified, the terms used in this application have the common meanings generally understood by those skilled in the art.

[0071] Unless otherwise specified, 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.

[0072] Unless otherwise specified, in this application, the term "active ions" refers to ions that can be intercalated and deintercalated between the positive electrode and the negative electrode of a secondary battery, including but not limited to lithium ions, sodium ions, etc.

[0073] In this application, the terms "plurality" and "multiple" refer to two or more.

[0074] According to the definition of the International Union of Pure and Applied Chemistry (IUPAC), 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, and macropores refer to pores with a pore diameter of more than 50 nm.

[0075] In the context of this application, 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 2 nm-50 nm; when the term "macroporous" appears, it refers to pores with a pore diameter of more than 50 nm.

[0076] In the context of the present application, the term "small mesopores" refers to pores with a pore diameter of 2 nm to 10 nm, and the term "large mesopores" refers to pores with a pore diameter greater than 10 nm and less than or equal to 50 nm.

[0077] In the context of this application, the term "capillary pores" when used refers to micropores and / or small mesopores, ie pores with a pore diameter of ≤10 nm.

[0078] In the context of this application, the terms "larger pores" and "smaller pores" represent relative concepts.

[0079] With the application and promotion of secondary batteries, their energy density, service life, and rate performance are receiving increasing attention. The performance of the negative electrode active material determines, to a certain extent, the energy density, service life, and safety of secondary batteries. Graphite (including natural graphite and artificial graphite) is the most commonly used negative electrode active material for secondary batteries, but its theoretical gram capacity is only 372mAh / g, which means that there is very limited room for energy density improvement. Furthermore, the small interlayer spacing of graphite limits the improvement of rate performance, and it can no longer meet the actual demand for high-rate performance secondary batteries.

[0080] Compared to graphite, hard carbon has a larger interlayer spacing, which facilitates the rapid insertion and extraction of active ions, resulting in secondary batteries with excellent low-temperature performance, power performance, and safety. Hard carbon offers unique advantages, particularly in the field of power batteries. However, most commercialized hard carbons are low-capacity, with low capacity and first coulombic efficiency (for example, the capacity is typically between 200 mAh / g and 280 mAh / g, and the first coulombic efficiency is typically below 75%), which severely limits their practical applications.

[0081] Therefore, how to simultaneously improve the gram capacity and first coulombic efficiency of hard carbon remains a technical challenge that needs to be solved urgently.

[0082] In view of this, the first aspect of the embodiment of the present application provides a carbonaceous material, which takes into account higher gram capacity, higher first coulombic efficiency and higher structural stability, and enables the secondary battery to have high energy density, long service life and good rate performance at the same time.

[0083] carbonaceous materials

[0084] The carbonaceous material provided in the present application satisfies an adsorption rate v of 0.015≤v≤0.050 when subjected to a water vapor adsorption test under constant temperature and humidity conditions of 25° C. and 40% RH.

[0085] The water vapor adsorption test was conducted under the following conditions: A carbonaceous material having a mass m1 was placed in a container in a constant temperature and humidity chamber at 25°C and 40% RH. The water vapor adsorption mass m2 and the water vapor adsorption time t, when the carbonaceous material reached equilibrium, were recorded. The water vapor adsorption rate v = m2 / (m1×t), where m1 is measured in g, m2 is measured in g, and t is measured in h. The stacked thickness of the carbonaceous material in the container was ≤ 5 mm.

[0086] In the water vapor adsorption test, when the total mass of the carbonaceous material no longer increases after adsorbing water vapor, it is considered that the carbonaceous material has reached equilibrium in adsorbing water vapor. The test time at this time is recorded, which is the water vapor adsorption time t. The total mass of the carbonaceous material obtained at this time is subtracted from the initial mass m1 of the carbonaceous material to obtain the water vapor adsorption mass m2 (that is, the mass increased when the carbonaceous material adsorbs water vapor to reach equilibrium).

[0087] RH (Relative Humidity) stands for relative humidity, which refers to the percentage of water vapor partial pressure in the air to the saturated vapor pressure of water at the same temperature.

[0088] Compared with currently commercialized carbonaceous materials, the carbonaceous material provided by the present 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. Although the mechanism is not clear, the inventors of the present application speculate that one possible reason is that when the water vapor adsorption rate v is between 0.015 and 0.050, the structural stability of the carbonaceous material of the present application is high and it has a unique pore structure, which can facilitate the embedding, storage and extraction of active ions, and thus the carbonaceous material of the present 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.

[0089] During the research process, the inventors of the present application discovered that under 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 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.

[0090] When the water vapor adsorption rate v is less than 0.015, it is believed that the carbonaceous material contains very few capillary pore 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 specific 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.

[0091] When the water vapor adsorption rate v is greater than 0.050, it is believed that the specific surface area of ​​the carbonaceous material is high, which leads to increased consumption of active ions during SEI film formation, increased first irreversible capacity loss, and reduced first coulombic efficiency. In addition, carbonaceous materials have strong water absorption. During the preparation and use of secondary batteries, some water molecules will be firmly bound to the functional groups on the surface of the carbonaceous material (such as oxygen-containing functional groups) through chemical bonds. As a result, the water molecules are not easy to remove, which will clog the capillary structure of the carbonaceous material and hinder the embedding and removal of active ions. At the same time, 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 specific capacity and first coulombic efficiency of the carbonaceous material.

[0092] In some embodiments, v can 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 range thereof, 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.

[0093] In some embodiments, the water vapor adsorption time t when the carbonaceous material adsorbs water vapor to reach equilibrium is 1h-12h. Optionally, 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 inventors found in further research that when 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 coulombic efficiency and structural stability of the carbonaceous material, thereby further improving the energy density, service life and rate performance of the secondary battery.

[0094] When the water vapor adsorption time is long, it is believed that the carbonaceous material contains more capillary pore structures. At this time, 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; when the water vapor adsorption time is short, it is believed that the carbonaceous material contains fewer capillary pore structures, which is 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.

[0095] In some embodiments, the carbonaceous material comprises a plurality of nanoporous structures. Alternatively, the carbonaceous material comprises a plurality of pore structures with a pore size of less than 10 nm. In some embodiments, the carbonaceous material may further comprise one or more pore structures with a pore size greater than 10 nm.

[0096] In some embodiments, the true density ρ of the carbonaceous material is 1.0 g / cm 3 -2.2g / cm 3 , optional 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 The inventors found in further research that when the true density of the carbonaceous material satisfies the above-mentioned specific range, it helps to further improve the gram capacity and the first coulombic efficiency of the carbonaceous material.

[0097] When the true density of the carbonaceous material is low, it is believed that the carbonaceous material has a rich capillary pore structure and a good closed-pore effect. At this time, 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. At the same time, 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. When the true density of the carbonaceous material is high, the calibration liquid (such as n-butanol) can easily infiltrate the interior of the particles. It is believed that the closed-pore effect of the carbonaceous material is poor, and the large mesoporous structure and / or macroporous structure are rich. As a result, the capillary pore structure is easily exposed to the electrolyte, resulting in a reduction in the storage space for active ions, and thus the gram capacity and first coulombic efficiency of the carbonaceous material are reduced.

[0098] In this application, the true density of a carbonaceous material is generally known in the art and can be measured using instruments and methods known in the art. For example, the Archimedean immersion volume displacement method can be used for testing, with n-butanol being a suitable calibration liquid. A powder true density meter can be used as the testing instrument.

[0099] In some embodiments, the carbonaceous material may have a regular or irregular morphology. For example, the carbonaceous material may have an irregular multi-angle morphology.

[0100] In some embodiments, the carbon content of the carbonaceous material may be 95 wt%-98 wt%.

[0101] In some embodiments, the O content in the carbonaceous material may be 1 wt%-5 wt%.

[0102] In some embodiments, the H content in the carbonaceous material may be less than 0.4 wt %.

[0103] In some embodiments, the N content in the carbonaceous material may be less than 2 wt %.

[0104] In some embodiments, the total content of C, O, H, and N elements in the carbonaceous material may be 99 wt% to 99.5 wt%.

[0105] In some embodiments, the carbonaceous material contains a small amount of impurity elements, which 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%, and the Fe content may be <0.0010wt%.

[0106] In some embodiments, in the Raman spectrum of the carbonaceous material, I d / Ig 1.0-1.3, I d Indicates that the Raman shift is 1350±50cm -1 d peak intensity in the range, I g Indicates that the Raman shift is 1580±50cm -1 g peak intensity in the range. For example, I d / I g It can be 1.0, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3 or any range thereof. d / I g It can be 1.05-1.15.

[0107] The Raman spectrum of carbonaceous materials 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 peak intensity of 100 points is calculated. d / I g , remove the largest and smallest 30 I d / I g , the remaining 40 I d / I g The average value of the carbonaceous material I d / I g The test instrument can be a Horiba LabRAM HR800 Raman spectrometer. The test conditions can be: excitation wavelength 532nm, grating 600 lines, objective lens 50x, integration time 10s, accumulation times 3 times, and surface scan.

[0108] The d peak is generated by the carbon atom lattice defect, and the g peak is generated by the in-plane vibration of the sp2 carbon atom. In the carbonaceous material structure, 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 It can characterize the order of the carbonaceous material structure. d / I g The smaller the carbon material, the higher the order of the carbon material structure, the higher the integrity of the carbon plane, the higher the first coulombic efficiency of the carbon material, but the gram capacity becomes lower and the rate performance becomes worse. The carbon material of this application meets I d / I g It is 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.

[0109] In some embodiments, 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.

[0110] In some embodiments, in the X-ray diffraction spectrum of the carbonaceous material, the 2θ value corresponding to the (002) crystal plane peak is between 22° and 24°.

[0111] In the present application, the interlayer spacing of the (002) crystal plane of the carbonaceous material can be measured with reference to JIS K 0131-1996 and JB / T 4220-2011 using an X-ray diffractometer, which can be a Bruker D8 Discover X-ray diffractometer.

[0112] In some embodiments, the volume particle size Dv50 of the carbonaceous material may be 4 μm-6 μm.

[0113] In some embodiments, the volume particle size Dv90 of the carbonaceous material may be 8 μm-16 μm.

[0114] In some embodiments, the carbonaceous material simultaneously satisfies a volume particle size Dv50 of 4 μm to 6 μm and a volume particle size Dv90 of 8 μm to 16 μm.

[0115] When the 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.

[0116] In this application, the volume particle sizes Dv50 and Dv90 of carbonaceous materials are generally known in the art and represent the particle sizes corresponding to the 50% and 90% cumulative volume distribution percentages, respectively. These can be measured using instruments and methods known in the art. For example, they can be conveniently measured using a laser particle size analyzer, referring to the laser diffraction method for particle size distribution in GB / T 19077-2016. The testing instrument can be a Mastersizer 2000E laser particle size analyzer from Malvern Instruments Ltd., UK.

[0117] In some embodiments, the specific surface area of ​​the carbonaceous material is 0.1 m 2 / g-20m 2 / g, optional 1m 2 / g-20m 2 When the specific surface area of ​​the carbonaceous material is within an appropriate range, it can simultaneously achieve higher gram capacity and first coulombic efficiency, while also exhibiting better rate performance. Furthermore, when the specific surface area of ​​the carbonaceous material is within an appropriate range, it can also provide a stronger bond between the carbonaceous material and the binder, thereby improving the cohesion and adhesion of the negative electrode sheet, reducing the volume expansion of the negative electrode sheet during cycling, and improving the cycle performance of the secondary battery.

[0118] In this application, the specific surface area of ​​a carbonaceous material 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 the nitrogen adsorption specific surface area analysis test method in accordance with GB / T 19587-2017 and calculated using the BET (Brunauer Emmett Teller) method. The nitrogen adsorption specific surface area analysis test can be measured using an ASAP 3020 surface area and pore size analyzer from Micromeritics, USA.

[0119] In some embodiments, the powder compaction density of the carbonaceous material under a force of 50,000 N is 0.90 g / cm 3 -1.05g / cm 3 , optional 0.92g / cm 3 -1.02g / cm 3 When the compaction density of the carbonaceous material powder is within an appropriate range, the compaction density of the negative electrode sheet can be increased, thereby increasing the energy density of the secondary battery.

[0120] In this application, the compacted density of carbonaceous material powder is 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 by an electronic pressure testing machine (such as UTM7305) with reference to the standard GB / T24533-2009. An exemplary test method is as follows: 1g of carbonaceous material powder is weighed and added to a container with a bottom area of ​​1.327cm 2 In the mold, pressurize 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 the force of 50000N.

[0121] In some embodiments, the tap density of the carbonaceous material is 0.78 g / cm 3 -0.95g / cm 3 , optional 0.83g / cm 3 -0.93g / cm 3 When the tap density of the carbonaceous material is within an appropriate range, the compaction density of the negative electrode sheet can be increased, thereby increasing the energy density of the secondary battery.

[0122] In this application, the tap density of a carbonaceous material is generally known 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 in accordance with GB / T 5162-2006. A suitable tester is the Dandong Better BT-301.

[0123] Preparation method of carbonaceous material

[0124] A second aspect of an 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 when subjected to an adsorption test using water vapor under constant temperature and humidity conditions of 25°C and 40% RH satisfies 0.015≤v≤0.050.

[0125] The water vapor adsorption test is carried out under the following conditions: in a constant temperature and humidity chamber at 25°C and 40% RH, the carbonaceous material with a mass of m1 is placed in a container, and 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 measurement of m1 is g, the unit of measurement of m2 is g, and the unit of measurement of t is h.

[0126] The present application uses cellulose biomass materials as carbon sources to prepare carbonaceous materials. Cellulose is a chain-like macromolecular organic substance with high crystallinity among biomass materials. On the one hand, it has high thermal stability and a wide range of adjustable parameters for the pyrolysis process. On the other hand, the pore structure formed by the chain-like macromolecular organic substance during its conversion into carbonaceous materials is highly controllable, which enables it to have a suitable water vapor adsorption rate and also helps to increase the platform capacity. When the carbon source does not use cellulose biomass materials or the biomass materials used do not contain cellulose, the pore structure of the carbonaceous material prepared therefrom has poor controllability and a low content of capillary pore structure, which manifests as a too low water vapor adsorption rate. In some embodiments, the cellulose content in the cellulose biomass material may be greater than 0wt% and less than or equal to 100wt%, and may be optionally 10wt%-100wt%, 20wt%-100wt%, 30wt%-100wt%, or 40wt%-100wt%. This is conducive to increasing the controllability of the pore structure of the carbonaceous material and enabling it to have a suitable water vapor adsorption rate.

[0127] 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 increase 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 aromaticize the biochar obtained by low-temperature pre-carbonization treatment, thereby improving the order and conductivity of the carbonaceous material, while removing excess O and H elements on the carbon skeleton structure, and helping to form an ordered pseudographite microcrystalline structure.

[0128] Therefore, the carbonaceous material obtained by the preparation method provided in this application can achieve a high gram capacity, a high first coulombic efficiency, and high structural stability, thereby enabling secondary batteries to simultaneously possess high energy density, long service life, and good rate performance. Furthermore, compared to existing commercial hard carbon, the gram capacity, first coulombic efficiency, and rate performance of the carbonaceous material obtained by the preparation method of this application are significantly improved.

[0129] The inventors also discovered during their research that cellulose biomass materials need to have a low ash content. Ash not only produces a catalytic reaction during the low-temperature pre-carbonization process, consuming the C element content and reducing active ion storage sites, but also increases the complexity and production cost of the washing and impurity removal process. Furthermore, during the subsequent high-temperature carbonization process, the metal impurities in the ash are reduced to metal elements and then agglomerated. The agglomeration of metal elements causes the carbon skeleton structure to collapse, especially the collapse of the capillary structure, which in turn leads to a reduction in the active ion storage space and capacity of the obtained carbonaceous material, manifested as an excessively low water vapor adsorption rate. At the same time, the metal impurities also have catalytic activity, which will lead to an intensified decomposition of the carbon skeleton structure during the cracking process, causing the pore structure to tend to form larger mesoporous and / or macroporous structures. This results in poor stability of the carbon skeleton structure and an increase in the proportion of electrolyte-wetted areas within the obtained carbonaceous material. This increases the consumption of active ions during SEI film formation and the first irreversible capacity loss, thus reducing the first coulombic efficiency of the carbonaceous material. In some embodiments, the ash content in the cellulosic biomass material may be 0 wt%-5 wt%, optionally 0 wt%-4 wt%, 0 wt%-3 wt%, 0 wt%-2 wt%, or 0 wt%-1 wt%. This can reduce the adverse effects of impurities on the carbonaceous material, improve the gram capacity, first coulombic efficiency, and structural stability of the carbonaceous material, and also help reduce the true density of the carbonaceous material.

[0130] In some embodiments, optionally, the cellulose content in the cellulosic biomass material is greater than 0 wt% and less than or equal to 100 wt%, and the ash content is 0 wt%-5 wt%.

[0131] Cellulosic biomass materials can also contain hemicellulose. Hemicellulose is an amorphous high-molecular substance with a relatively small molecular weight in biomass materials. During the low-temperature pre-carbonization process, it is easy to decompose into small-molecule sugars and volatilize, 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 the content of large mesoporous structure and / or large pore structure in the carbonaceous material, increase the proportion of electrolyte infiltration area inside the carbonaceous material, increase the first irreversible capacity loss, and reduce the first coulombic efficiency. In some embodiments, the hemicellulose content in the cellulosic biomass material may be 0wt%-70wt%, optionally 0wt%-60wt%, 0wt%-50wt%, 0wt%-40wt%, 0wt%-30wt%, or 0wt%-20wt%.

[0132] Cellulosic biomass materials can also contain lignin. Lignin is a macromolecular organic substance containing benzene rings and having a high degree of cross-linking. It helps to form carbon six-membered rings during low-temperature pre-carbonization treatment, helps to improve the stability of the carbon skeleton structure, and thus is beneficial to improving the rate performance of secondary batteries; but the controllability of the pore structure formed by it is poor. Therefore, when its content is too high, for example, greater than 60wt%, it will cause the capacity improvement space of the obtained carbonaceous material platform to be limited. In some embodiments, the lignin content in the cellulosic biomass material is 0wt%-60wt%, optionally 5wt%-60wt%, 10wt%-60wt%, 10wt%-50wt%, and 15wt%-50wt%.

[0133] In some embodiments, the cellulose content in the cellulosic 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%. Alternatively, the cellulose content in the cellulosic 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%. As a result, the obtained carbonaceous material is helped to better balance higher gram capacity, higher first coulombic efficiency and higher structural stability, thereby further improving the energy density, service life and rate performance of the secondary battery.

[0134] In some embodiments, the cellulose content of the cellulosic biomass material can be 100 wt%, meaning that the cellulosic biomass material can directly use cellulose as a carbon source. This helps the resulting carbonaceous material have a high capacity, but the stability of the carbon skeleton structure formed during the preparation process is slightly reduced, resulting in a slight decrease in the effect of improving the rate performance of the secondary battery.

[0135] In this application, cellulose content can be measured using an acid hydrolysis anthrone colorimetric method. Cellulose can be hydrolyzed into β-D-glucose under acidic conditions. β-D-glucose dehydrates in a strong acid environment to form β-furfural compounds. These compounds dehydrate and condense with anthrone to form a blue-green furfural derivative. The product has a characteristic absorption peak at 620 nm, and the change in absorbance can be used to quantitatively measure the cellulose content. For example, the acid can be sulfuric acid.

[0136] In this application, hemicellulose content can be detected using the DNS colorimetric method. After acid treatment, hemicellulose is converted into reducing sugars, which react with DNS to produce a reddish-brown substance. The product has a characteristic absorption peak at 540 nm, and the change in absorbance can be used to quantitatively detect the hemicellulose content.

[0137] In this application, the lignin content can be detected by acetylation. The phenolic hydroxyl groups in lignin undergo acetylation to generate acetyl lignin, which has a characteristic absorption peak at 280 nm. The change in absorbance can be used to quantitatively detect the lignin content.

[0138] In this application, the ash content can be measured with reference to GB / T 28731-2012.

[0139] In some embodiments, 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, bamboo, and walnut shells.

[0140] In some embodiments, the preparation method further comprises the step of pretreating the cellulosic biomass material. The pretreatment process may include crushing, cleaning, and drying steps. Crushing the cellulosic biomass material facilitates packing. Cleaning can remove impurities that are clearly attached to the surface of the cellulosic biomass material, preventing them from affecting the subsequent low-temperature pre-carbonization process. Drying can remove moisture attached to the surface of the cellulosic biomass material and some bulk moisture, thereby reducing the impact of moisture on the subsequent low-temperature pre-carbonization process.

[0141] In some embodiments, the first heating rate is ≤10°C / min, and can be selected from 1°C / min to 10°C / min, 1°C / min to 5°C / min, and 1°C / min to 3°C / min. When the first heating rate is within an appropriate 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. When the first heating rate is too high, the pore structure of the prepared carbonaceous material has poor controllability and a low content of capillary pore structure, which is manifested as a low water vapor adsorption rate.

[0142] In some embodiments, the first temperature T1 is 150° C. to 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. Alternatively, the first temperature T1 is 200° C. to 900° C., 300° C. to 700° C., or 300° C. to 600° C. When the first temperature is within a suitable range, the obtained carbonaceous material can have a suitable water vapor adsorption rate, high capacity, high first coulombic efficiency, and high structural stability. As the first temperature rises, 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-pore effect during high-temperature carbonization treatment, increase the content of large mesoporous structure and / or macroporous structure in the carbonaceous material, increase the proportion of electrolyte infiltration area inside the carbonaceous material, increase the first irreversible capacity loss, reduce the first coulombic efficiency, and at the same time, reduce the content of capillary pore structure in the carbonaceous material, which is manifested as a lower water vapor adsorption rate.

[0143] In some embodiments, the first time t1 is 1 hour to 20 hours, and may be 5 hours to 20 hours. Those skilled in the art may select an appropriate first time within the above range based on 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 may be appropriately shortened.

[0144] In S20, by adjusting one or more of the first heating rate, the first temperature and the first time within the above range, it is beneficial to better regulate the carbon skeleton structure and surface, improve the low-temperature pre-carbonization treatment effect, and obtain a carbonaceous material with a suitable water vapor adsorption rate.

[0145] In some embodiments, the second heating rate is ≤10°C / min, and may be 0.5°C / min-10°C / min. However, the present application is not limited thereto, and the second heating rate may be adjusted according to actual conditions.

[0146] In some embodiments, the second temperature T2 is 1000° C. to 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. Alternatively, the second temperature T2 is 1200° C. to 1500° C. When the second temperature is within a suitable range, the obtained carbonaceous material has a suitable water vapor adsorption rate, high capacity, and high first coulombic efficiency. 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. However, at this time, the pore structure has a poor closed-pore effect, and there are more large mesoporous structures and / or macroporous structures in the carbonaceous material, which in turn 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. As the second temperature rises, the closed-pore effect of the pore structure becomes better, thereby reducing the consumption of active ions during SEI film formation, and increasing the active ion storage sites of the carbonaceous material, thereby increasing its capacity and first coulombic efficiency. However, when the second temperature is too high, the microstructure of the carbonaceous material will undergo a qualitative change, which is not conducive to active ion storage, and is manifested as a decrease in the water vapor adsorption rate.

[0147] In some embodiments, the second time t2 is 1 hour to 12 hours, and may be 3 hours to 10 hours. Those skilled in the art may select an appropriate first time within the above range based on the second temperature and the second heating rate used. For example, when the second temperature is high and / or the second heating rate is low, the second time may be appropriately shortened.

[0148] In S30, by adjusting one or more of the second heating rate, the second temperature and the second time within the above range, it is beneficial to improve the closed-pore effect of the pore structure, improve the high-temperature carbonization treatment effect, and obtain a carbonaceous material with a suitable water vapor adsorption rate.

[0149] In some embodiments, t1+t2 is 10 h to 30 h, thereby helping the obtained carbonaceous material to have a suitable water vapor adsorption rate, high capacity, high first coulombic efficiency and high structural stability.

[0150] In some embodiments, after S20 and before S30, the process further includes the following steps: crushing the first intermediate product obtained in S20, washing and removing impurities from the first intermediate product obtained in S20, or first crushing the first intermediate product obtained in S20 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 ≤0.01 wt%, 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, while also helping to reduce the true density of the carbonaceous material.

[0151] The crushing process can reduce the particle size of the first intermediate product, thereby helping to obtain a carbonaceous material of a desired size. In some embodiments, the volume particle size Dv50 of the crushed particles is 4 μm to 6 μm. In some embodiments, the volume particle size Dv90 of the crushed particles is 8 μm to 16 μm. In some embodiments, the volume particle size Dv50 of the crushed particles is 4 μm to 6 μm and the volume particle size Dv90 is 8 μm to 16 μm. Of course, in some embodiments, the crushing step can be omitted.

[0152] The washing and impurity removal treatment can remove inorganic impurities and water-soluble impurities in the first intermediate product, and prevent the metal impurities from being reduced to metal elements and then agglomerating during the subsequent high-temperature carbonization treatment. Because the agglomeration of metal elements will cause the carbon skeleton structure to 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; at the same time, the metal impurities also have catalytic activity, which will lead to the aggravated decomposition of the carbon skeleton structure during the cracking process, causing the pore structure to tend to form a large mesoporous structure and / or a large pore structure with a larger size, 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, and 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 the carbonaceous material, and improving the gram capacity and first coulomb efficiency of the carbonaceous material.

[0153] In this application, the crushing process needs to be performed before the washing and impurity removal process. This allows the first intermediate product to expose as much surface area as possible during the subsequent washing and impurity removal process, thereby facilitating sufficient contact between the particles and the washing liquid and improving the washing and impurity removal effect. If the crushing process is performed after the washing and impurity removal process, some large pieces of raw materials will basically retain their original appearance after pyrolysis, and the washing liquid may not be able to enter the bulk phase of the large particles. As a result, impurities deeply encapsulated in the bulk phase of the large particles cannot be removed, resulting in a poor washing and impurity removal effect.

[0154] Crushing can be performed using a process known in the art suitable for crushing in the preparation of carbonaceous materials. In some embodiments, the crushing can include ball milling or air flow milling.

[0155] The order of acidic solution washing and alkaline solution washing is not particularly limited. In some embodiments, the washing and impurity removal treatment process comprises 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 comprises the following steps in sequence: alkaline solution washing, water washing, acidic 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, 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 2 hours is ≤0.1wt%, and the drying step is considered to be completed.

[0156] 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.

[0157] In some embodiments, the acidic solution has H + The concentration is 0.1mol / L-6moL / L, and can be selected as 1mol / L-6moL / L.

[0158] In some embodiments, the washing temperature of the acidic solution is 10°C-95°C, optionally 30°C-95°C.

[0159] In some embodiments, the washing time of the acidic solution is 1 hour to 24 hours, and optionally 10 hours to 24 hours.

[0160] In some embodiments, 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.

[0161] By adjusting the H + One or more of the concentration, washing temperature, washing time, solute type, etc. being within the above range is conducive to achieving sufficient washing and better removal of metal impurities.

[0162] In some embodiments, the OH of the alkaline solution - The concentration is 0.1mol / L-6moL / L, and can be selected as 1mol / L-6moL / L.

[0163] In some embodiments, the washing temperature of the alkaline solution is 10°C-95°C, optionally 30°C-95°C.

[0164] In some embodiments, the washing time of the alkaline solution is 1 hour to 24 hours, and can be optionally 10 hours to 24 hours.

[0165] In some embodiments, the solute of the alkaline solution includes NaOH, KOH, or a combination thereof, and the solvent includes water.

[0166] By adjusting the OH - When one or more of the concentration, washing temperature, washing time, solute type, etc. are within the above range, it is beneficial to achieve sufficient washing.

[0167] In some embodiments, the washing and impurity removal step can be omitted.

[0168] In some embodiments, when the ash content of the obtained first intermediate product is ≥0.5 wt %, washing and impurity removal treatment is required to ensure that the ash content in the material before high-temperature carbonization treatment is ≤0.01 wt %.

[0169] The present application does not particularly limit the type of protective gas atmosphere in S20 and S30. In some embodiments, the protective gas includes nitrogen, an inert gas, or a combination thereof. Alternatively, the inert atmosphere includes argon, helium, or a combination thereof. Optionally, the volume concentration of the gas may be greater than 99.9%.

[0170] In some embodiments, the preparation method further includes: S40, crushing: crushing the carbonaceous material obtained in S30. At this time, the carbonaceous material agglomerated during the preparation process can be crushed to meet the required particle size to facilitate the preparation of negative electrode slurry and negative electrode sheets. Of course, in some embodiments, this step can be omitted.

[0171] In some embodiments, the preparation method includes 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℃-1000℃, optionally 300℃-700℃, under a protective gas atmosphere at a rate of ≤10℃ / min, and then heat-treating for 1h-20h, optionally 5h -20h to obtain a first intermediate product; high-temperature carbonization treatment: the obtained first intermediate product is heated to 1000℃-1600℃, optionally 1200℃-1500℃, under a protective gas atmosphere at a rate of ≤10℃ / min, and then heat-treated for 1h-12h, optionally 3h-10h, to obtain a carbonaceous material, wherein the carbonaceous material has an adsorption rate v of 0.015≤v≤0.050 when subjected to a water vapor adsorption test under constant temperature and humidity conditions of 25℃ and 40%RH. The carbonaceous material thus obtained can better balance higher gram capacity, higher first coulombic efficiency and higher structural stability, thereby further improving the energy density, service life and rate performance of the secondary battery.

[0172] In some embodiments, the preparation method includes 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 maintaining the temperature for 1h-20h, optionally 5h-20h, to obtain a first intermediate product; high-temperature carbonization treatment: The obtained first intermediate product is crushed to a volume particle size Dv50 of 4μm-6μm and / or a volume particle size Dv90 of 8μm-16μm, and then heated to 1000℃-1600℃, optionally 1200℃-1500℃, at a rate of ≤10℃ / 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 has an adsorption rate v of 0.015≤v≤0.050 when subjected to a water vapor adsorption test under constant temperature and humidity conditions of 25℃ and 40%RH. The carbonaceous material thus obtained can better balance higher gram capacity, higher first coulombic efficiency and higher structural stability, thereby further improving the energy density, service life and rate performance of the secondary battery.

[0173] In some embodiments, the preparation method includes 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℃-1000℃, optionally 300℃-700℃, under a protective gas atmosphere at a rate of ≤10℃ / min, 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 4μm-6μm and / or the volume particle size Dv90 is 8μm-16μm, it is washed with an acidic solution, washed with water, washed with an alkaline solution, washed with water, and dried. Then, under a protective gas atmosphere, the temperature is raised to 1000℃-1600℃, optionally 1200℃-1500℃, and then heat-treated for 1h-12h, optionally 3h-10h, to obtain a carbonaceous material, wherein the adsorption rate v of the carbonaceous material when subjected to a water vapor adsorption test under constant temperature and humidity conditions of 25℃ and 40%RH satisfies 0.015≤v≤0.050. The carbonaceous material thus obtained can better balance higher gram capacity, higher first coulombic efficiency, and higher structural stability, thereby further improving the energy density, service life, and rate performance of the secondary battery.

[0174] 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 auxiliary agents, so that the carbonaceous material obtained by the preparation method provided in the present application has a lower heteroatom content.

[0175] secondary batteries

[0176] A third aspect of the embodiments of the present application provides a secondary battery.

[0177] The secondary battery mentioned in the embodiments or implementations of this application refers to a single physical module that includes one or more battery cells to provide higher voltage and capacity. For example, the secondary battery mentioned in this application may include a battery cell, a battery module or a battery pack. A battery cell is the smallest unit that makes up a secondary battery, which can realize the function of charging and discharging alone. This application has no particular restrictions on the shape of the battery cell, which can be cylindrical, square or any other shape. Figure 1 shows a battery cell 5 with a square structure as an example.

[0178] In some embodiments, a battery cell includes an electrode assembly and an electrolyte, and the cell may further include an outer packaging. The outer packaging may be used to encapsulate the electrode assembly and the electrolyte. The outer packaging may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging may also be a soft package, such as a bag-type soft package. The soft package may be made of plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0179] An electrode assembly typically includes a positive electrode sheet and a negative electrode sheet. During the charge and discharge process of a secondary battery, active ions are embedded and released back and forth between the positive and negative electrode sheets. The electrolyte conducts the active ions between the positive and negative electrode sheets. Electrode assemblies can be manufactured through winding and / or lamination processes.

[0180] In some embodiments, as shown in Figure 2, the outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a bottom plate and side plates connected to the bottom plate, which together form a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 is used to cover the opening to seal the receiving cavity. The electrode assembly 52 is enclosed in the receiving cavity. The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and can be adjusted according to needs.

[0181] In some embodiments of the present application, battery cells can be assembled into a battery module. 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. Figure 3 is a schematic diagram of a battery module 4 as an example. As shown in Figure 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 arbitrary manner. The multiple battery cells 5 can further be fixed by fasteners.

[0182] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0183] In some embodiments, the above-mentioned 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. As shown in Figures 4 and 5, 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. The upper box body 2 is used to cover the lower box body 3 and form an enclosed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0184] [Negative electrode]

[0185] In some embodiments, 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. For example, the negative electrode current collector has two surfaces that are opposite to each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposing surfaces of the negative electrode current collector.

[0186] In some embodiments, 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.

[0187] In some embodiments, the negative electrode film layer may further include other negative electrode active materials in addition to the above-mentioned carbonaceous materials. In some embodiments, 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 materials may include one or more of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy materials. The tin-based materials may include one or more of elemental tin, tin oxide, and tin alloy materials.

[0188] In some embodiments, the negative electrode film layer may further optionally include a negative electrode conductive agent. The present application does not particularly limit the type of the negative electrode conductive agent. As examples, the 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.

[0189] In some embodiments, the negative electrode film layer may further optionally include a negative electrode binder. The present application does not particularly limit the type of the negative electrode binder. As examples, 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).

[0190] In some embodiments, the negative electrode film layer may further include other additives. For example, the other additives may include a thickener, such as sodium carboxymethyl cellulose (CMC), a PTC thermistor material, and the like.

[0191] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, 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. As an example, the metal material may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. As an example, the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS) and polyethylene (PE).

[0192] The negative electrode film layer is typically formed by coating a negative electrode slurry onto a negative electrode current collector, drying, and cold pressing. The negative electrode slurry is typically formed by dispersing the negative electrode active material, an optional conductive agent, an optional binder, and other optional additives in a solvent and stirring until uniformly mixed. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0193] The negative electrode plate does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode plate described in the present application further 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 further includes a protective layer covering the surface of the negative electrode film layer.

[0194] [Positive electrode]

[0195] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector. For example, the positive electrode current collector has two surfaces that are opposite to each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposing surfaces of the positive electrode current collector.

[0196] The positive electrode current collector may be a metal foil or a composite current collector. As an example of 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. As an example, the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. As an example, the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS) and polyethylene (PE).

[0197] 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 a positive electrode slurry on the positive electrode current collector, drying and cold pressing. The positive electrode slurry is generally formed by dispersing a positive electrode active material, an optional conductive agent, an optional binder and any other components in a solvent and stirring evenly. The solvent may be N-methylpyrrolidone (NMP), but is not limited thereto. As an example, 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. As an example, 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.

[0198] The positive electrode active material may be a positive electrode active material for a secondary battery known in the art.

[0199] When the secondary battery of the present application is a lithium-ion battery, 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. Examples of 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. Examples of the 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.

[0200] In some embodiments, in order to further improve the energy density of the secondary battery, the positive electrode active material for the lithium ion battery may include a general formula of Li a Ni b Co c M d O e A f One or more lithium transition metal oxides and modified compounds thereof. 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.

[0201] As an example, the positive active material for lithium ion batteries may include LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM333),LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM622),LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), LiNi 0.85 Co 0.15 Al 0.05 One or more of O2, LiFePO4 and LiMnPO4.

[0202] When the secondary battery of the present application is a sodium ion battery, 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.

[0203] As an example, the positive active material for sodium ion batteries may include NaFeO2, NaCoO2, NaCrO2, NaMnO2, NaNiO2, NaNi 1 / 2 Ti 1 / 2 O2、NaNi 1 / 2 Mn 1 / 2 O2、Na 2 / 3 Fe 1 / 3 Mn 2 / 3 O2、NaNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, NaFePO4, NaMnPO4, NaCoPO4, Prussian blue materials and general formula X p M' q (PO4) r O x Y 3-x One or more materials. p M' q (PO4) r O x Y 3-x , 0<p≤4, 0<q≤2, 1≤r≤3, 0≤x≤2, X includes H + 、Li + 、Na + , K+ and NH4 + One or more of, 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.

[0204] In the present application, the modified compounds of the above-mentioned positive electrode active materials may be the ones subjected to doping modification and / or surface coating modification on the positive electrode active materials.

[0205] [Electrolytes]

[0206] The present application has no particular limitation on the type of the electrolyte, and the electrolyte can be selected according to actual needs. For example, the electrolyte can be selected from at least one of a solid electrolyte and a liquid electrolyte (ie, an electrolyte solution).

[0207] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0208] The type of the electrolyte salt is not particularly limited and can be selected according to actual needs.

[0209] When the secondary battery of the present application is a lithium ion battery, as an example, the electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobisoxalatophosphate (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).

[0210] When the secondary battery of the present application is a sodium ion battery, the electrolyte salt may include sodium hexafluorophosphate (NaPF6), sodium tetrafluoroborate (NaBF4), sodium perchlorate (NaClO4), sodium hexafluoroarsenate (NaAsF6), sodium bis(fluorosulfonyl)imide (NaFSI), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), sodium trifluoromethanesulfonate (NaTFS), sodium difluorooxalatoborate (NaDFOB), sodium dioxalatoborate (NaBOB), sodium difluorophosphate (NaPO2F2), sodium difluorobis(oxalatophosphate) (NaDFOP) and sodium tetrafluorooxalatophosphate (NaTFOP). One or more.

[0211] The type of the solvent is not specifically limited and can be selected according to actual needs. In some embodiments, for example, 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), ethyl methyl sulfone (EMS) and diethyl sulfone (ESE). One or more.

[0212] In some embodiments, the electrolyte may further include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, or additives capable of improving 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.

[0213] [Isolation film]

[0214] Secondary batteries using electrolytes, as well as some using solid-state electrolytes, also include a separator. This separator is positioned between the positive and negative electrodes to provide isolation. This application does not specifically limit the type of separator; any known porous separator with good chemical and mechanical stability can be used.

[0215] In some embodiments, 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 may be the same or different.

[0216] [Preparation method]

[0217] The preparation method of the secondary battery of the present application is well known. In some embodiments, the positive electrode sheet, the separator, the negative electrode sheet and the electrolyte can be assembled to form a secondary battery. As an example, 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, dried and injected with electrolyte, and then vacuum packaged, left to stand, formed, and shaped to obtain a battery cell. Multiple battery cells can also be further connected in series, in parallel, or mixed to form a battery module. Multiple battery modules can also be connected in series, in parallel, or mixed to form a battery pack. In some embodiments, multiple battery cells can also directly form a battery pack.

[0218] Electrical devices

[0219] In a fourth aspect of the embodiments of the present application, there is provided an electrical device, the electrical device comprising the secondary battery of the present application. The secondary battery can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may 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, a satellite, an energy storage system, etc.

[0220] 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.

[0221] Figure 6 is a schematic diagram of an exemplary electrical device. This device is a pure electric vehicle, hybrid electric vehicle, or plug-in hybrid electric vehicle. To meet the device's high power and high energy density requirements, a battery pack or battery module can be used as a power source.

[0222] As another example, an electric device may be a mobile phone, a tablet computer, a laptop computer, etc. Such an electric device is usually required to be lightweight and thin, and may use a battery cell as a power source.

[0223] Example

[0224] The following examples describe the present disclosure in more detail. These examples are intended to be illustrative only, as various modifications and variations within the scope of the present disclosure will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are by mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing. The instruments used in the examples are commercially available.

[0225] Example 1

[0226] 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%.

[0227] The pine wood was heated to 150° C. (as the first temperature T1) at a rate of 1° C. / min (as the first heating rate) under a nitrogen atmosphere, and then kept warm for 10 hours (the first time t1). After the heating, the wood was cooled to room temperature to obtain a first intermediate product.

[0228] The first intermediate product is crushed by air jet mill to a volume particle size Dv50 of 4μm-6μm, 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 with air to remove moisture to obtain a first intermediate product with an ash content of ≤0.01wt%.

[0229] 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.

[0230] In a constant temperature and humidity chamber at 25°C and 40% RH (i.e., the ratio of the water vapor partial pressure in the air to the saturated vapor pressure of water is 40%), 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.

[0231] The true density of carbonaceous materials was tested by Archimedes impregnation volume displacement method with n-butanol as the medium.

[0232] Examples 2-19 and Comparative Examples 1-7

[0233] The preparation method of the carbonaceous material is similar to that of Example 1, except that the preparation process parameters of the carbonaceous material are adjusted. See Table 1 for details.

[0234] Performance Testing

[0235] The carbonaceous materials prepared in each embodiment and comparative example were thoroughly stirred and mixed with the binder styrene-butadiene rubber (SBR), the thickener sodium carboxymethyl cellulose (CMC-Na), and the conductive agent carbon black in an appropriate amount of deionized water in a mass ratio of 96.2:1.8:1.2:0.8 to form a uniform negative electrode slurry; the negative electrode slurry was evenly coated on the surface of the negative electrode current collector copper foil, dried in an oven and set aside. Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain an organic solvent, and then NaPF6 was dissolved in the above organic solvent to prepare an electrolyte with a concentration of 1 mol / L. Afterwards, a metal sodium sheet was used as the counter electrode and a polyethylene (PE) film was used as the isolation membrane to assemble a CR2430 button battery in an argon-protected glove box.

[0236] At 25°C, the button cells prepared in each embodiment and comparative example were first discharged at a current density of 10 mA / g to 0 V, and the first-cycle discharge capacity of the button cells was recorded. Thereafter, the button cells were charged at a current density of 10 mA / g to 2.0 V, and the first-cycle charge capacity of the button cells was recorded.

[0237] The reversible gram capacity of the carbonaceous material (mAh / g) = the first cycle charge capacity of the button cell / the mass of the carbonaceous material.

[0238] First coulombic efficiency of carbonaceous material (%) = first cycle charge capacity of button cell / first cycle discharge capacity of button cell × 100%.

[0239] After the button battery was fully charged and fully discharged at 0.33C and 1C respectively, the discharge capacity at 0.33C and 1C was obtained. 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.

[0240] Table 1

[0241]

[0242]

[0243] Table 2

[0244]

[0245]

[0246] Figures 7 to 9 are scanning electron micrographs of the carbonaceous material provided herein at different magnifications. As shown in Figures 7 to 9, the carbonaceous material provided herein has an irregular, multi-angular morphology. Based on the test results in Table 2, it can be seen that when the carbonaceous material meets the conditions of constant temperature and humidity at 25°C and 40% RH, and the water vapor adsorption rate v is between 0.015 and 0.050, the carbonaceous material achieves both high gram capacity and high initial coulombic efficiency, as well as good rate performance.

[0247] 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. Therefore, the carbonaceous materials cannot have both a higher gram capacity, a higher first coulombic efficiency and good rate performance.

[0248] Comparative Example 1 uses rice husk as a carbon source, and its ash content is higher than 5wt%. Since the ash not only produces a catalytic reaction during the low-temperature pre-carbonization treatment process, consumes the C element content, and reduces the active ion storage site, but also reduces the metal impurities in the ash to metal elements and then agglomerates during the subsequent high-temperature carbonization treatment. When the 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 water vapor adsorption rate. At the same time, the metal impurities also have catalytic activity, which will lead to an aggravated decomposition of the carbon skeleton structure during the cracking process, causing the pore structure to tend to form a large-sized mesoporous structure and / or a macroporous 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 coulombic efficiency.

[0249] In Comparative Example 2, when preparing the carbonaceous material, no low-temperature pre-carbonization treatment was performed, resulting 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.

[0250] Based on the test results of Examples 1-19, it can be seen that when the water vapor adsorption time t of the carbonaceous material is further satisfied to be between 4.5h and 7h, the carbonaceous material can have a higher gram capacity, first coulombic efficiency and / or rate performance.

[0251] It can be seen from the test results of Examples 1-19 that when the true density ρ of the carbonaceous material further satisfies 1.3 g / cm 3 -1.7g / cm 3 When the carbonaceous materials have a higher specific capacity, first coulombic efficiency and / or rate capability, the carbonaceous materials can have a higher specific capacity, first coulombic efficiency and / or rate capability.

[0252] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A carbonaceous material, wherein The carbonaceous material has an adsorption rate v of 0.015≤v≤0.050 when subjected to a water vapor adsorption test under constant temperature and humidity conditions of 25°C and 40% RH. The water vapor adsorption test is carried out under the following conditions: in a constant temperature and humidity chamber at 25°C and 40% RH, the carbonaceous material with a mass of m1 is placed in a container, and 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 measurement of m1 is g, the unit of measurement of m2 is g, and the unit of measurement of t is h.

2. The carbonaceous material according to claim 1, wherein 0.020≤v≤0.050。 3. The carbonaceous material according to claim 1 or 2, wherein 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.

4. The carbonaceous material according to any one of claims 1 to 3, wherein The true density ρ of the carbonaceous material is 1.0 g / cm 3 -2.2g / cm 3 , optional 1.3g / cm 3 -1.7g / cm 3 .

5. The carbonaceous material according to any one of claims 1 to 4, wherein The carbonaceous material includes a plurality of nanopore structures. Optionally, the carbonaceous material includes a plurality of pore structures with a pore diameter of less than 10 nm.

6. The carbonaceous material according to any one of claims 1 to 5, wherein In the Raman spectrum of the carbonaceous material, I d / I g 1.0-1.3, optional 1.05-1.15, I d Indicates that the Raman shift is 1350±50cm -1 d peak intensity in the range, I g Indicates that the Raman shift is 1580±50cm -1 g peak intensity within the range; and / or, The interlayer spacing of the (002) crystal plane of the carbonaceous material is ≥0.37 nm, and can be selected from 0.37 nm to 0.42 nm; and / or, In the X-ray diffraction spectrum of the carbonaceous material, the 2θ value corresponding to the (002) crystal plane peak is between 22° and 24°.

7. The carbonaceous material according to any one of claims 1 to 6, wherein: The carbonaceous material satisfies at least one of the following conditions (1) to (5): (1) The volume particle size Dv50 of the carbonaceous material is 4 μm-6 μm; (2) the volume particle size Dv90 of the carbonaceous material is 8 μm-16 μm; (3) The specific surface area of ​​the carbonaceous material is 0.1m 2 / g-20m 2 / g, optional 1m 2 / g-20m 2 / g; (4) The powder compaction density of the carbonaceous material under a force of 50,000 N is 0.90 g / cm 3 -1.05g / cm 3 , optional 0.92g / cm 3 -1.02g / cm 3 ; (5) The tap density of the carbonaceous material is 0.78 g / cm 3 -0.95g / cm 3 , optional 0.83g / cm 3 -0.93g / cm 3 .

8. A method for preparing a carbonaceous material, comprising the following steps: S10, providing a carbon source: the carbon source is a cellulosic 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 maintaining the temperature 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 maintaining the temperature for a second time t2 to obtain a carbonaceous material, wherein: The adsorption rate v of the carbonaceous material when subjected to a water vapor adsorption test under constant temperature and humidity conditions of 25°C and 40% RH satisfies 0.015≤v≤0.

050. The water vapor adsorption test is carried out under the following conditions: in a constant temperature and humidity chamber at 25°C and 40% RH, the carbonaceous material with a mass of m1 is placed in a container, and 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), where the unit of m1 is g, the unit of m2 is g, and the unit of t is h.

9. The method according to claim 8, wherein 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%.

10. The method according to claim 8 or 9, wherein: The cellulose content in the cellulose biomass material is greater than or equal to 20 wt% and less than 100 wt%; and / or, The ash content in the cellulosic biomass material is 0 wt%-2 wt%.

11. The method according to claim 9 or 10, wherein: The hemicellulose content in the cellulosic biomass material is 0wt%-70wt%, optionally 0wt%-30wt%; and / or, The lignin content in the cellulose biomass material is 0 wt%-60 wt%, and can be optionally 10 wt%-60 wt%.

12. The method according to any one of claims 9 to 11, wherein: The cellulosic biomass material includes one or more woody biomass materials, and can be selected from one or more of hardwood, softwood and nut shells, and can be selected from one or more of pine wood, bamboo and walnut shells.

13. The method according to any one of claims 8 to 12, wherein: The first heating rate is 1°C / min-10°C / min, optionally 1°C / min-3°C / min; and / or, The first temperature T1 is 150°C-1000°C, optionally 300°C-700°C; and / or, The first time t1 is 1 hour to 20 hours, and can be optionally 5 hours to 20 hours.

14. The method according to any one of claims 8 to 13, wherein: The second heating rate is ≤10°C / min, and can be optionally 0.5°C / min-10°C / min; and / or, The second temperature T2 is 1000° C.-1600° C., optionally 1200° C.-1500° C.; and / or, The second time t2 is 1 hour to 12 hours, and can be optionally 3 hours to 10 hours.

15. The method according to any one of claims 8 to 14, wherein: t1+t2 is 10h-30h.

16. The method according to any one of claims 8 to 15, wherein: After S20 and before S30, the following steps are also included: crushing the first intermediate product obtained in S20, or washing and removing impurities on the first intermediate product obtained in S20, or first crushing the first intermediate product obtained in S20 and then washing and removing impurities to obtain a first intermediate product with an ash content of ≤0.01wt%, and the washing and removing impurities treatment process includes at least an acidic solution washing step and an alkaline solution washing step.

17. The method according to claim 16, wherein 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.

18. The method according to claim 16 or 17, wherein The acidic solution satisfies at least one of the following conditions (1) to (4): (1) H of the acidic solution + The concentration is 0.1mol / L-6moL / L, and can be selected from 1mol / L-6moL / L; (2) The washing temperature of the acidic solution is 10°C-95°C, and can be optionally 30°C-95°C; (3) The washing time of the acidic solution is 1 hour to 24 hours, and can be optionally 10 hours to 24 hours; (4) 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.

19. The method according to any one of claims 16 to 18, wherein: The alkaline solution satisfies at least one of the following conditions (1) to (4): (1) OH of the alkaline solution - The concentration is 0.1mol / L-6moL / L, and can be selected from 1mol / L-6moL / L; (2) The washing temperature of the alkaline solution is 10°C-95°C, and can be optionally 30°C-95°C; (3) The washing time of the alkaline solution is 1 hour to 24 hours, and can be optionally 10 hours to 24 hours; (4) The solute of the alkaline solution includes NaOH, KOH or a combination thereof, and the solvent includes water.

20. A secondary battery comprising a negative electrode plate, wherein the negative electrode plate comprises the carbonaceous material according to any one of claims 1 to 7 or the carbonaceous material prepared by the method according to any one of claims 8 to 19.

21. An electric device comprising the secondary battery according to claim 20.

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