Carbonaceous material, method for producing the same, and secondary battery and electric device containing the same

Abstract

A carbonaceous material and a preparation method thereof, and a secondary battery and an electric device containing the same, the carbonaceous material satisfying 0.015<=v<=0.050 in an adsorption rate v when a water vapor adsorption test is performed at 25 DEG C and 40% RH under constant temperature and humidity conditions, the water vapor adsorption test being performed as follows: placing the carbonaceous material with a mass of m1 in a container in a constant temperature and humidity chamber at 25 DEG C and 40% RH, recording a water vapor adsorption mass m2 and a water vapor adsorption time t when the carbonaceous material adsorbs water vapor to reach equilibrium, and then the water vapor adsorption rate v=m2 / (m1*t), the unit of m1 being g, the unit of m2 being g, and the unit of t being h. The carbonaceous material can have a high gravimetric capacity, a high initial coulombic efficiency and a high structural stability.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of batteries, and particularly relates to a carbonaceous material and a preparation method thereof, and a secondary battery and an electric device containing the same. BACKGROUND

[0002] In recent years, secondary batteries are widely applied in energy storage power systems such as hydraulic, thermal, wind and solar power stations, and in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. With the application and promotion of secondary batteries, their energy density, service life and rate performance are attracting more and more attention. Graphite is the most commonly used negative active material for secondary batteries, but its theoretical specific capacity is only 372 mAh / g, and the space for improving energy density is very limited; at the same time, the interlayer spacing of graphite is small, and the improvement of rate performance is also limited. Hard carbon, as a new type of negative active material, can realize the rapid intercalation and deintercalation of active ions during the charging and discharging process of secondary batteries, so it has a very broad development prospect. However, the specific capacity and the first coulombic efficiency of hard carbon are low, which limits the improvement of the energy density, service life and rate performance of secondary batteries. SUMMARY

[0003] The purpose of the present application is to provide a carbonaceous material and a preparation method thereof, and a secondary battery and an electric device containing the same, which can balance high specific capacity, high first coulombic efficiency and high structural stability, and enable the secondary battery to have high energy density, long service life and good rate performance at the same time.

[0004] The first aspect of the present application provides a carbonaceous material, wherein the adsorption rate v of the carbonaceous material satisfies 0.015≤v≤0.050 when a water vapor adsorption test is carried out under the condition of 25℃, 40%RH constant temperature and humidity, and the water vapor adsorption test is carried out under the following conditions: placing the carbonaceous material with a mass of m1 in a container in a constant temperature and humidity chamber at 25℃, 40%RH, recording the water vapor adsorption mass m2 and the water vapor adsorption time t when the carbonaceous material adsorbs water vapor to reach equilibrium, then 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.

[0005] Compared with the currently commercialized carbonaceous materials, the carbonaceous material provided in the application can balance the higher gram capacity, higher first coulombic efficiency and higher structural stability, and can make the secondary battery simultaneously have high energy density, long service life and good rate performance. Although the mechanism is not clear, the inventors of the 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 application is high and has a unique pore structure, which can facilitate the insertion, storage and extraction of active ions, and thus the carbonaceous material of the application can balance the higher gram capacity and first coulombic efficiency, and can make the secondary battery simultaneously have high energy density, long service life and good rate performance.

[0006] In any embodiment of the application, 0.020≤v≤0.050. Thereby it helps to further improve the gram capacity, first coulombic efficiency and structural stability of the carbonaceous material, and thus can further improve the energy density, service life and rate performance of the secondary battery.

[0007] In any embodiment of the application, the water vapor adsorption time t of the carbonaceous material when adsorbing water vapor to reach equilibrium is 1h-12h, which can be selected as 4.5h-7h. When the water vapor adsorption time of the carbonaceous material when adsorbing water vapor to reach equilibrium meets the above specific range, it helps to further improve the gram capacity, first coulombic efficiency and structural stability of the carbonaceous material, and thus can further improve the energy density, service life and rate performance of the secondary battery.

[0008] In any embodiment of the application, the true density p of the carbonaceous material is 1.0g / cm 3 -2.2g / cm 3 , which can be selected as 1.3g / cm 3 -1.7g / cm 3 . When the true density of the carbonaceous material meets the above specific range, it helps to further improve the gram capacity and first coulombic efficiency of the carbonaceous material.

[0009] In any embodiment of the application, the carbonaceous material comprises a plurality of nanopore structures, and optionally, the carbonaceous material comprises a plurality of pore structures with a pore size of less than 10nm.

[0010] In any embodiment of the application, in the Raman spectrum of the carbonaceous material, I d / I g is 1.0-1.3, which can be selected as 1.05-1.15, I d represents the intensity of the d peak with a Raman shift in the range of 1350±50cm -1 , I g represents the intensity of the G peak with a Raman shift in the range of 1580±50cm -1the g peak intensity in the range. At this time, the carbonaceous material has higher gram capacity and higher first coulomb efficiency, and also has good rate performance.

[0011] In any embodiment of the present application, the interlayer spacing of the (002) crystal plane of the carbonaceous material is ≥0.37 nm, and optionally 0.37 nm-0.42 nm.

[0012] In any embodiment of the present application, in the X-ray diffraction spectrum of the carbonaceous material, the (002) crystal plane peak corresponds to a 2θ value of 22°-24°.

[0013] In any embodiment of the present application, the volume particle size Dv50 of the carbonaceous material is 4 μm-6 μm.

[0014] In any embodiment of the present application, the volume particle size Dv90 of the carbonaceous material is 8 μm-16 μm.

[0015] When the volume particle size Dv50 and / or Dv90 of the carbonaceous material is in a suitable range, the active ion and electron transmission performance can be improved, thereby further improving the rate performance of the secondary battery.

[0016] In any embodiment of the present application, the specific surface area of the carbonaceous material is 0.1 m 2 / g-20 m 2 / g, and optionally 1 m 2 / g-20 m 2 / g. When the specific surface area of the carbonaceous material is in a suitable range, the carbonaceous material can have higher gram capacity and first coulomb efficiency, and also have better rate performance.

[0017] In any embodiment of the present application, the powder compaction density of the carbonaceous material under the action of 50,000 N is 0.90 g / cm 3 -1.05 g / cm 3 , and optionally 0.92 g / cm 3 -1.02 g / cm 3 . When the powder compaction density of the carbonaceous material is in a suitable range, the compaction density of the negative electrode sheet can be improved, thereby improving the energy density of the secondary battery.

[0018] In any embodiment of the present application, the tap density of the carbonaceous material is 0.78 g / cm 3 -0.95 g / cm 3 , and optionally 0.83 g / cm 3 -0.93 g / cm 3When the tap density of the carbonaceous material is within a proper range, the compaction density of the negative electrode sheet can be improved, and thus the energy density of the secondary battery can be improved.

[0019] The second aspect of the present application provides a preparation method of 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: the carbon source is treated at a first temperature T1 for a first time t1 under a protective gas atmosphere at a first heating rate, to obtain a first intermediate product; S30, high-temperature carbonization treatment: the obtained first intermediate product is treated at a second temperature T2 for a second time t2 under a protective gas atmosphere at a second heating rate, to obtain a carbonaceous material, wherein the adsorption rate v of the carbonaceous material satisfies 0.015≤v≤0.050 when the carbonaceous material is subjected to an adsorption test using water vapor under a constant temperature and humidity condition of 25℃ and 40% RH, and the water vapor adsorption test is performed under the following conditions: the carbonaceous material with a mass of m1 is placed in a container in a constant temperature and humidity chamber at 25℃ and 40% RH, and the water vapor adsorption mass m2 and the water vapor adsorption time t of the carbonaceous material when the water vapor adsorption reaches equilibrium are recorded, so that 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.

[0020] The carbonaceous material obtained by the preparation method provided in the present application can have high gravimetric capacity, high initial coulombic efficiency and high structural stability, and thus the secondary battery can have high energy density, long service life and good rate performance. Compared with the existing commercial hard carbon, the gravimetric capacity, the initial coulombic efficiency and the rate performance of the carbonaceous material obtained by the preparation method of the present application are all significantly improved.

[0021] In any embodiment of the present application, the cellulose content in the cellulose biomass material is greater than 0wt% and less than or equal to 100wt%, and the ash content is 0wt%-5wt%.

[0022] In any embodiment of the present application, the cellulose content in the cellulose biomass material is greater than or equal to 20wt% and less than 100wt%, and the ash content is 0wt%-5wt%.

[0023] In any embodiment of the present application, the cellulose content in the cellulose biomass material is greater than 0wt% and less than or equal to 100wt%, and the ash content is 0wt%-2wt%.

[0024] In any embodiment of the present application, the cellulose content in the cellulose biomass material is greater than or equal to 20wt% and less than 100wt%, and the ash content is 0wt%-2wt%.

[0025] In any embodiment of the present application, the content of hemicellulose in the cellulosic biomass material is 0wt%-70wt%, optionally 0wt%-30wt%.

[0026] In any embodiment of the present application, the content of lignin in the cellulosic biomass material is 0wt%-60wt%, optionally 10wt%-60wt%.

[0027] 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 has higher gravimetric capacity, higher first coulomb efficiency and higher structural stability, thereby further improving the energy density, service life and rate performance of the secondary battery.

[0028] In any embodiment of the present application, the cellulosic biomass material comprises one or more of woody biomass materials, optionally comprises one or more of hardwood, softwood and nut shell, and more optionally comprises one or more of pine, bamboo and walnut shell.

[0029] In any embodiment of the present application, the first temperature increasing rate is 1℃ / min-10℃ / min, optionally 1℃ / min-3℃ / min.

[0030] In any embodiment of the present application, the first temperature T1 is 150℃-1000℃, optionally 300℃-700℃.

[0031] In any embodiment of the present application, the first time t1 is 1h-20h, optionally 5h-20h.

[0032] In S20, by adjusting one or more of the first temperature increasing rate, the first temperature and the first time within the above range, the carbon skeleton structure and the surface are better controlled, the low-temperature pre-carbonization treatment effect is improved, and the carbonaceous material with a suitable water vapor adsorption rate is obtained.

[0033] In any embodiment of the present application, the second temperature increasing rate is ≤10℃ / min, optionally 0.5℃ / min-10℃ / min.

[0034] In any embodiment of the present application, the second temperature T2 is 1000℃-1600℃, optionally 1200℃-1500℃.

[0035] In any embodiment of the present application, the second time t2 is 1h-12h, optionally 3h-10h.

[0036] In S30, by adjusting one or more of the second temperature rising rate, the second temperature, and the second time within the above ranges, the closed pore effect of the pore structure is improved, the high-temperature carbonization treatment effect is improved, and the carbonaceous material with a suitable water vapor adsorption rate is obtained.

[0037] In any embodiment of the present application, t1+t2 is 10h-30h. Thus, the obtained carbonaceous material has a suitable water vapor adsorption rate, a high capacity, a high first coulombic efficiency, and a high structural stability.

[0038] In any embodiment of the present application, after S20 and before S30, the method further comprises a step of: subjecting the first intermediate product obtained in S20 to a crushing treatment, or subjecting the first intermediate product obtained in S20 to a washing and impurity removal treatment, or subjecting the first intermediate product obtained in S20 to a crushing treatment followed by a washing and impurity removal treatment, to obtain a first intermediate product with an ash content of ≤0.01wt%. The washing and impurity removal treatment process at least comprises an acid solution washing step and an alkaline solution washing step. Thus, the gravimetric capacity, the first coulombic efficiency, and the structural stability of the carbonaceous material are further improved, and the true density of the carbonaceous material is also reduced.

[0039] In any embodiment of the present application, the washing and impurity removal treatment process comprises the following steps in sequence: acid solution washing, water washing, alkaline solution washing, water washing, and drying; or, the washing and impurity removal treatment process comprises the following steps in sequence: alkaline solution washing, water washing, acid solution washing, water washing, and drying.

[0040] In any embodiment of the present application, the H + The concentration of the acid solution is 0.1mol / L-6moL / L, which can be optionally 1mol / L-6moL / L.

[0041] In any embodiment of the present application, the washing temperature of the acid solution is 10℃-95℃, which can be optionally 30℃-95℃.

[0042] In any embodiment of the present application, the washing time of the acid solution is 1h-24h, which can be optionally 10h-24h.

[0043] In any embodiment of the present application, the solute of the acid solution comprises one or more of hydrochloric acid, nitric acid, sulfuric acid, and perchloric acid, and the solvent comprises water.

[0044] By adjusting one or more of the H + concentration, the washing temperature, the washing time, the solute type, etc. of the acid solution within the above ranges, the metal impurities are better removed through sufficient washing.

[0045] In any embodiment of the present application, the OH - The concentration is 0.1 mol / L-6 moL / L, and can be 1 mol / L-6 moL / L.

[0046] In any embodiment of the present application, the washing temperature of the alkaline solution is 10℃-95℃, and can be 30℃-95℃.

[0047] In any embodiment of the present application, the washing time of the alkaline solution is 1h-24h, and can be 10h-24h.

[0048] 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.

[0049] By adjusting one or more of the OH - concentration, washing temperature, washing time, solute type, etc. of the alkaline solution within the above ranges, sufficient washing can be achieved.

[0050] The third aspect of the present application provides a secondary battery, which includes a negative electrode sheet including 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.

[0051] The fourth aspect of the present application provides an electric device, which includes the secondary battery of the third aspect of the present application.

[0052] The carbonaceous material provided by the present application can have high gravimetric capacity, high initial coulombic efficiency and high structural stability, and thus the secondary battery can have high energy density, long service life and good rate performance. The electric device provided by the present application includes the secondary battery provided by the present application, and thus has at least the same advantages as the secondary battery. BRIEF DESCRIPTION OF DRAWINGS

[0053] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0054] Figure 1 is a schematic diagram of an embodiment of a battery cell of the present application.

[0055] Figure 2 is an exploded schematic diagram of an embodiment of a battery cell of the present application.

[0056] Figure 3 is a schematic diagram of an embodiment of a battery module of the present application.

[0057] Figure 4 is a schematic view of an embodiment of the battery pack of the present application.

[0058] Figure 5 is Figure 4 is an exploded schematic view of the embodiment of the battery pack shown in

[0059] Figure 6 is a schematic view of an embodiment of an electric device containing the secondary battery of the present application as a power source.

[0060] Figures 7 to 9 are scanning electron microscope images of the carbonaceous material provided by the present application at different magnifications.

[0061] In the drawings, the drawings are not necessarily drawn to scale. Reference signs are explained as follows: 1 battery pack, 2 upper case, 3 lower case, 4 battery module, 5 battery cell, 51 case, 52 electrode assembly, 53 cover plate. DETAILED DESCRIPTION

[0062] Hereinafter, embodiments of the carbonaceous material of the present application and a method for producing the same, and a secondary battery and an electric device containing the same will be specifically disclosed with appropriate reference to the drawings. However, there will be cases where unnecessary detailed description is omitted. For example, there will be cases where detailed description of matters that are well known, repeated description of actually identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the drawings and the following description are provided so that those skilled in the art can fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0063] The ranges disclosed herein are intended to be "open" ranges, i.e., the upper and lower limits of the range are not included. The ranges are also intended to include any and all sub-ranges of the range, i.e., all combinations of any two of the range limits, unless otherwise indicated. For example, a range of "1 to 10" is intended to include any number from 1 to 10, including the end values in the range, e.g., 1 and 10, and any and all intermediate values, e.g., 3.14, 4.56 etc. In addition, the phrase "a range of "a to b" is intended to include the end values in the range, i.e., "a" and "b", and to exclude any and all values outside of the range, unless otherwise indicated. For example, if a parameter is listed as being an integer > 2, it is understood that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0064] 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, unless otherwise specified.

[0065] All technical features and optional technical features 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, unless otherwise specified.

[0066] Unless otherwise specified, all steps of the present application can be performed in sequence or randomly, and preferably in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method also comprises step (c), which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0067] Unless otherwise specified, the "includes" and "contains" mentioned in the present application are open-ended, and can also be closed. For example, the "includes" and "contains" can mean that other components not listed can also be included or contained, or only the listed components can be included or contained.

[0068] If not specifically stated otherwise, the term "or" in the present application is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, any of the following satisfy the condition "A or B": A is true (or present) and B is false (or not present); A is false (or not present) and B is true (or present); or both A and B are true (or present).

[0069] If not specifically stated otherwise, the terms used in the present application have the commonly understood meaning as understood by a person skilled in the art.

[0070] If not specifically stated otherwise, the values of the parameters mentioned in the present application can be measured by various test methods commonly used in the art, for example, according to the test methods given in the present application.

[0071] If not specifically stated otherwise, the term "active ion" in the present application refers to ions that can be reversibly intercalated and deintercalated between the positive and negative electrodes of a secondary battery, including but not limited to lithium ions, sodium ions, etc.

[0072] In the present application, the terms "a plurality of" and "a plurality of kinds" mean two or more.

[0073] According to the definition of the International Union of Pure and Applied Chemistry (IUPAC), micropores refer to pores with a pore size < 2 nm, mesopores refer to pores with a pore size of 2 nm-50 nm, and macropores refer to pores with a pore size > 50 nm.

[0074] In the context of the present application, the term "micropore" refers to a pore with a pore size < 2 nm, the term "mesopore" refers to a pore with a pore size of 2 nm-50 nm, and the term "macropore" refers to a pore with a pore size > 50 nm.

[0075] In the context of the present application, the term "small mesopore" refers to a pore with a pore size of 2 nm-10 nm, and the term "large mesopore" refers to a pore with a pore size greater than 10 nm and less than or equal to 50 nm.

[0076] In the context of the present application, the term "capillary pore" refers to a micropore and / or a small mesopore, i.e., a pore with a pore size ≤ 10 nm.

[0077] In the context of the present application, the terms "larger pore" and "smaller pore" represent relative concepts.

[0078] With the application and promotion of secondary batteries, the energy density, service life and rate performance thereof are paid more and more attention. The performance of negative active material determines the energy density, service life and safety of the secondary battery to some extent. Graphite (including natural graphite and artificial graphite) is the most commonly used negative active material for secondary batteries, but the theoretical specific capacity thereof is only 372 mAh / g, and the energy density thereof has very limited room for improvement. Meanwhile, the interlayer spacing of graphite is small, and the rate performance thereof is also limited, which cannot meet the actual needs of secondary batteries with high rate performance.

[0079] Compared with graphite, the interlayer spacing of hard carbon is larger, and thus, the rapid embedding and extraction of active ions are facilitated, so that the secondary battery has excellent low-temperature performance, power performance and safety performance, and in particular, hard carbon has unique advantages in the field of power batteries. However, most of the commercialized hard carbon currently belongs to low-capacity hard carbon, and the capacity and the first coulombic efficiency thereof are low, for example, the capacity is usually between 200 mAh / g and 280 mAh / g, and the first coulombic efficiency is usually lower than 75%, which seriously limits the actual application thereof.

[0080] Therefore, how to simultaneously improve the specific capacity and the first coulombic efficiency of hard carbon is still a technical problem to be solved at present.

[0081] In view of this, the first aspect of the embodiments of the present application provides a carbonaceous material which has high specific capacity, high first coulombic efficiency and high structural stability, and enables the secondary battery to have high energy density, long service life and good rate performance at the same time.

[0082] Carbonaceous material

[0083] The adsorption rate v of the carbonaceous material provided in the present application meets 0.015≤v≤0.050 when the adsorption test is carried out by using water vapor under the condition of constant temperature and humidity at 25℃ and 40% RH.

[0084] The water vapor adsorption test is carried out under the following conditions: in a constant temperature and humidity chamber at 25℃ 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 of the carbonaceous material when the water vapor adsorption reaches equilibrium are recorded, so that 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. In the container, the bulk thickness of the carbonaceous material is ≤5 mm.

[0085] In the water vapor adsorption test, when the total mass of the carbonaceous material after adsorbing water vapor no longer continues to increase, it is considered that the carbonaceous material has reached equilibrium in adsorbing water vapor, and the test time at this time is recorded, that is, the water vapor adsorption time t, and the total mass of the carbonaceous material 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 of the carbonaceous material adsorbing water vapor to reach equilibrium).

[0086] RH (Relative Humidity) represents relative humidity, which refers to the percentage of water vapor partial pressure in air to the saturated vapor pressure of water at the same temperature.

[0087] Compared with the currently commercialized carbonaceous materials, the carbonaceous material provided in the present application can balance high gram capacity, high first coulombic efficiency and high 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 carbonaceous material of the present application has high structural stability and unique pore structure, which can facilitate the insertion, storage and extraction of active ions, and thus the carbonaceous material of the present application can balance high 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.

[0088] The inventors of the present application found in the research process that under the constant temperature and humidity conditions of 25°C and 40% RH, water vapor will preferentially adsorb into the capillary pore structure (i.e. micropore structure and / or small mesopore structure) of the carbonaceous material, and generally will not enter the large mesopore structure and / or macropore structure of the carbonaceous material, so that the water vapor adsorption rate v under the constant temperature and humidity conditions of 25°C and 40% RH can directly reflect the content of sites suitable for active ion storage in the carbonaceous material.

[0089] When the water vapor adsorption rate v is less than 0.015, it is considered that the carbonaceous material contains very little capillary pore structure, and the pore structure is mostly large mesopore structure and / or macropore structure, so that the carbonaceous material has poor structural stability and contains very little space to accommodate active ions, and is not suitable for active ion storage, and thus the gram capacity of the carbonaceous material is also low; in addition, since the pore structure is mostly large mesopore structure and / or macropore structure, the proportion of electrolyte infiltration area in the carbonaceous material is increased, the consumption of active ions during the formation of solid electrolyte interface film (hereinafter referred to as SEI film) is increased, the first irreversible capacity loss is increased, and thus the gram capacity and the first coulombic efficiency of the carbonaceous material are both low.

[0090] When the water vapor adsorption rate v is greater than 0.050, it is considered that the specific surface area of the carbonaceous material is relatively high, which leads to an increase in consumption of active ions when the SEI film is formed, an increase in the first irreversible capacity loss, and a decrease in the first coulombic efficiency. In addition, the carbonaceous material has strong water absorption. During the preparation and use of the secondary battery, some water molecules will be combined with the functional groups (such as oxygen-containing functional groups) on the surface of the carbonaceous material in a relatively firm chemical bond, so that the water molecules are not easy to be removed, thereby blocking the capillary pore structure of the carbonaceous material, hindering the embedding and de-embedding of active ions, and also causing the carbonaceous material to have a decrease in the specific capacity and the first coulombic efficiency.

[0091] 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 a range consisting of any numerical value within the above ranges, optionally, 0.018≤v≤0.050, 0.020≤v≤0.050. This is helpful to further improve the specific capacity, the first coulombic efficiency, and the structural stability of the carbonaceous material, and further improve the energy density, the service life, and the rate performance of the secondary battery.

[0092] In some embodiments, the water vapor adsorption time t of the carbonaceous material when the water vapor adsorption reaches equilibrium is 1h-12h. Optionally, the water vapor adsorption time t of the carbonaceous material when the water vapor adsorption reaches equilibrium is 3h-12h, 4h-12h, 4h-9h, 4.5h-7h. The inventors have found in further research that when the water vapor adsorption time of the carbonaceous material when the water vapor adsorption reaches equilibrium satisfies the above specific range, it is helpful to further improve the specific capacity, the first coulombic efficiency, and the structural stability of the carbonaceous material, and further improve the energy density, the service life, and the rate performance of the secondary battery.

[0093] When the water vapor adsorption time is relatively long, it is considered that the carbonaceous material contains more capillary pore structures. At this time, the skeleton structure of the carbonaceous material is relatively weak and is easy to collapse to form a larger pore, thereby causing an increase in the proportion of the internal electrolyte wetting area of 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 relatively short, it is considered that the carbonaceous material contains less capillary pore structures, which is not suitable for the embedding, storage, and de-embedding of active ions, thereby also causing a decrease in the specific capacity and the first coulombic efficiency of the carbonaceous material.

[0094] In some embodiments, the carbonaceous material comprises a plurality of nanoporous structures. Optionally, the carbonaceous material comprises a plurality of pore structures with a pore size of 10 nm or less. In some embodiments, the carbonaceous material can further comprise one or more pore structures with a pore size greater than 10 nm.

[0095] In some embodiments, the carbonaceous material has a true density p of 1.0 g / cm 3 -2.2 g / cm 3 , optionally 1.3 g / cm 3 -2.0 g / cm 3 , 1.3 g / cm 3 -1.7 g / cm 3 , 1.3 g / cm 3 -1.65 g / cm 3 , 1.3 g / cm 3 -1.6 g / cm 3 , 1.3 g / cm 3 -1.55 g / cm 3 . The inventors have found in further studies that when the carbonaceous material has a true density within the above specified ranges, the gravimetric capacity and the first coulombic efficiency of the carbonaceous material are further improved.

[0096] When the true density of the carbonaceous material is small, it is considered that the carbonaceous material has abundant mesoporous structures and good closed-pore effect. At this time, the space entered by the calibration liquid (such as n-butanol) is less than the actual pore space of the carbonaceous material, and these unentered pore structures can store active ions. At the same time, the electrolyte is not easy to enter the interior of the carbonaceous material particles, thereby reducing the consumption of active ions when the SEI film is formed. In addition, the true density of the carbonaceous material should not be too low, otherwise the active ions may not be easily inserted due to the too good closed-pore effect of the carbonaceous material. When the true density of the carbonaceous material is large, the calibration liquid (such as n-butanol) can easily infiltrate the interior of the particles. It is considered that the carbonaceous material has poor closed-pore effect, abundant macroporous structures and / or mesoporous structures at this time, which leads to the exposure of the mesoporous structures to the electrolyte, thereby reducing the active ion storage space, and further reducing the gravimetric capacity and the first coulombic efficiency of the carbonaceous material.

[0097] In the present application, the true density of the carbonaceous material has the meaning known in the art and can be determined by using instruments and methods known in the art. For example, the Archimedes immersion volume displacement method can be used for testing, and n-butanol can be used as the calibration liquid. The testing instrument can be a powder true density meter.

[0098] In some embodiments, the carbonaceous material can have a regular or irregular morphology, for example, the morphology of the carbonaceous material can be irregular polyhedral.

[0099] In some embodiments, the content of C element in the carbonaceous material can be 95wt%-98wt%.

[0100] In some embodiments, the content of O element in the carbonaceous material can be 1wt%-5wt%.

[0101] In some embodiments, the content of H element in the carbonaceous material can be <0.4wt%.

[0102] In some embodiments, the content of N element in the carbonaceous material can be <2wt%.

[0103] In some embodiments, the sum of the contents of C, O, H and N elements in the carbonaceous material can be 99wt%-99.5wt%.

[0104] In some embodiments, the content of impurity elements in the carbonaceous material is less, and the impurity elements mainly include S, K, Ca and Fe, the content of S element can be <0.0021wt%, the content of K element can be <0.0019wt%, the content of Ca element can be <0.0011wt%, and the content of Fe element can be <0.0010wt%.

[0105] In some embodiments, in the Raman spectrum of the carbonaceous material, I d / I g is 1.0-1.3, I d represents the intensity of d peak with Raman shift in the range of 1350±50cm -1 , I g represents the intensity of g peak with Raman shift in the range of 1580±50cm -1 . For example, I d / I g may be 1.0, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3 or a range consisting of any of the above values. Alternatively, I d / I g may be 1.05-1.15.

[0106] The Raman spectrum of the carbonaceous material can be tested by using a Raman spectrometer, and the intensities of d peak and g peak of 100 points are obtained during the test, I d / I g of the 100 points are calculated, 30 largest and smallest I d / I g are removed, and the average value of the remaining 40 I d / I g is taken as the I d / I gThe testing instrument can be a Horiba LabRAM HR800 Raman spectrometer. The testing conditions can be: excitation wavelength 532 nm, grating 600 lines, objective lens 50 times, integration time 10 s, cumulative number 3 times, and area scanning.

[0107] The d peak is generated by carbon atom lattice defects, and the g peak is generated by in-plane vibration of sp2 carbon atoms. In the structure of the carbonaceous material, the d peak intensity is related to the number of defects in the structure of the carbonaceous material, and the g peak intensity is related to the number of graphite crystallites in the structure of the carbonaceous material. Therefore, I d / I g The order degree of the structure of the carbonaceous material can be characterized. d / I g The smaller the value is, the higher the order degree of the structure of the carbonaceous material is, and the higher the integrity of the carbon plane is, and the first coulomb efficiency of the carbonaceous material is increased, but the specific capacity is lowered and the rate performance is deteriorated. The carbonaceous material of the present application satisfies I d / I g 1.0-1.3, at this time, the order degree of the structure of the carbonaceous material is moderate, so that the carbonaceous material has higher specific capacity and higher first coulomb efficiency, and also has good rate performance.

[0108] In some embodiments, the interlayer spacing of the (002) crystal plane of the carbonaceous material is ≥0.37 nm, and optionally 0.37 nm-0.42 nm.

[0109] In some embodiments, in the X-ray diffraction spectrum of the carbonaceous material, the (002) crystal plane peak corresponds to a 2θ value of 22° to 24°.

[0110] In the present application, the interlayer spacing of the (002) crystal plane of the carbonaceous material can be tested by using an X-ray diffractometer according to JIS K 0131.1996, JB / T4220-2011. The testing instrument can be a Bruker D8 Discover X-ray diffractometer.

[0111] In some embodiments, the volume particle size Dv50 of the carbonaceous material can be 4 μm-6 μm.

[0112] In some embodiments, the volume particle size Dv90 of the carbonaceous material can be 8 μm-16 μm.

[0113] In some embodiments, the carbonaceous material simultaneously satisfies the volume particle size Dv50 of 4 μm-6 μm and the volume particle size Dv90 of 8 μm-16 μm.

[0114] When the volume particle size Dv50 and / or Dv90 of the carbonaceous material is in a suitable range, the active ion and electron transmission performance can be improved, so that the rate performance of the secondary battery can be further improved.

[0115] In the present application, the volume particle size Dv50, Dv90 of the carbonaceous material is the meaning known in the art, which represents the particle size corresponding to the cumulative volume distribution percentage of 50%, 90% respectively, and can be measured by the instruments and methods known in the art. For example, it can be conveniently measured by referring to GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method, using a laser particle size analyzer. The testing instrument can be a Mastersizer 2000E laser particle size analyzer of Malvern Instruments Ltd., UK.

[0116] In some embodiments, the specific surface area of the carbonaceous material is 0.1 m 2 / g-20 m 2 / g, and optionally 1 m 2 / g-20 m 2 / g. When the specific surface area of the carbonaceous material is within the appropriate range, the carbonaceous material can have both higher gravimetric capacity and first coulombic efficiency, and also have better rate performance. In addition, when the specific surface area of the carbonaceous material is within the appropriate range, the carbonaceous material and the binder can have strong binding force, thereby improving the cohesion and adhesion of the negative electrode sheet, reducing the volume expansion of the negative electrode sheet during the cycle process, and making the secondary battery have better cycle performance.

[0117] In the present application, the specific surface area of the carbonaceous material is the meaning known in the art, and can be measured by the instruments and methods known in the art. For example, it can be tested by referring to GB / T 19587-2017, using the nitrogen adsorption specific surface area analysis test method, and calculated by the BET (Brunauer Emmett Teller) method, wherein the nitrogen adsorption specific surface area analysis test can be measured by the ASAP 3020 surface area and pore size analyzer of Micromeritics Corporation, USA.

[0118] In some embodiments, the powder compaction density of the carbonaceous material under the action of 50000 N force is 0.90 g / cm 3 -1.05 g / cm 3 , and optionally 0.92 g / cm 3 -1.02 g / cm 3 . When the powder compaction density of the carbonaceous material is within the appropriate range, the compaction density of the negative electrode sheet can be improved, and thus the energy density of the secondary battery can be improved.

[0119] In the present application, the tap density of the carbonaceous material is the meaning known in the art, which can be measured by the instruments and methods known in the art. For example, it can be measured by an electronic pressure testing machine (for example, UTM7305) according to the standard GB / T 24533-2009. The exemplary test method is as follows: 1 g of carbonaceous material powder is weighed and added into a mold with a bottom area of 1.327 cm 2 , and is pressed to 5000 kg (equivalent to 50000 N), and is kept for 30 s, then is unloaded, and is kept for 10 s, then the tap density of the carbonaceous material under the action of 50000 N is recorded and calculated.

[0120] In some embodiments, the tap density of the carbonaceous material is 0.78 g / cm 3 -0.95 g / cm 3 , and optionally 0.83 g / cm 3 -0.93 g / cm 3 . When the tap density of the carbonaceous material is in the appropriate range, the tap density of the negative electrode sheet can be improved, and thus the energy density of the secondary battery can be improved.

[0121] In the present application, the tap density of the carbonaceous material is the meaning known in the art, which can be measured by the instruments and methods known in the art. For example, it can be measured by a powder tap density tester according to GB / T 5162-2006. The testing instrument can be Dandong Baiter BT-301.

[0122] Method for producing a carbonaceous material

[0123] The second aspect of the embodiments of the present application provides a preparation method of a carbonaceous material, comprising the following steps: S10, providing a carbon source: the carbon source is a cellulose-based biomass material; S20, low-temperature pre-carbonization treatment: the carbon source is treated at a first temperature T1 for a first time t1 under a protective gas atmosphere at a first heating rate, to obtain a first intermediate product; S30, high-temperature carbonization treatment: the obtained first intermediate product is treated at a second temperature T2 for a second time t2 under a protective gas atmosphere at a second heating rate, to obtain a carbonaceous material, wherein the adsorption rate v of the carbonaceous material satisfies 0.015≤v≤0.050 when the adsorption test is performed under the condition of 25℃, 40% RH constant temperature and humidity using water vapor.

[0124] The water vapor adsorption test is carried out as follows: the carbonaceous material with a mass of m1 is placed in a container in a constant temperature and humidity chamber at 25℃ and 40% RH, and the water vapor adsorption mass m2 and the water vapor adsorption time t of the carbonaceous material when the water vapor adsorption reaches equilibrium are recorded, then the water vapor adsorption rate v = m2 / (m1 x t), the unit of m1 is g, the unit of m2 is g, and the unit of t is h.

[0125] The cellulose biomass material is used as a carbon source to prepare the carbonaceous material. The cellulose belongs to the chain macromolecular organic matter with high crystallinity in the biomass material. On the one hand, the thermal stability is high, and the pyrolysis process parameters can be adjusted in a wide range. On the other hand, the chain macromolecular organic matter has high controllability of the pore structure formed in the process of being converted into the carbonaceous material, can make it have a suitable water vapor adsorption rate, and also helps to improve the platform capacity. When the carbon source does not use the cellulose biomass material or the biomass material does not contain cellulose, the controllability of the pore structure of the carbonaceous material prepared therefrom is poor, and the content of the capillary pore structure is small, which shows that the water vapor adsorption rate is too small. In some embodiments, the cellulose content in the cellulose biomass material can be greater than 0wt% and less than or equal to 100wt%, which can be selected as 10wt%-100wt%, 20wt%-100wt%, 30wt%-100wt%, 40wt%-100wt%. Thus, it is beneficial to increase the controllability of the pore structure of the carbonaceous material and make it have a suitable water vapor adsorption rate.

[0126] The preparation process of the carbonaceous material at least includes a low-temperature pre-carbonization treatment process and a high-temperature carbonization treatment process. The low-temperature pre-carbonization treatment can regulate the carbon skeleton structure characteristics and surface characteristics, and appropriately improve the carbon yield; at the same time, it can reduce the toughness of the cellulose biomass material, which is helpful for subsequent crushing treatment and washing and impurity removal treatment. The high-temperature carbonization treatment can cause a closed pore effect on the bio-carbon obtained by the low-temperature pre-carbonization treatment, thereby reducing the contact area of the carbonaceous material and the electrolyte, i.e. reducing the consumption of active ions when the SEI film is formed, improving the first coulomb efficiency of the carbonaceous material; the high-temperature carbonization treatment can also make the bio-carbon obtained by the low-temperature pre-carbonization treatment be aromatic, thereby being able to improve the order degree and conductivity of the carbonaceous material, and at the same time, being able to remove the excess O elements and H elements on the carbon skeleton structure, and being helpful for forming an ordered pseudo-graphite microcrystalline structure.

[0127] Therefore, the carbonaceous material obtained by the preparation method provided in the present application can have high gravimetric capacity, high first coulomb efficiency and high structural stability, and thus the secondary battery can have high energy density, long service life and good rate performance. Compared with the existing commercial hard carbon, the gravimetric capacity, the first coulomb efficiency and the rate performance of the carbonaceous material obtained by the preparation method of the present application are all obviously improved.

[0128] The inventors have also found in the research that the cellulose biomass material needs to have a low ash content. Ash not only produces catalytic reactions in the low-temperature pre-carbonization process, consumes C element content, and reduces active ion storage sites, but also increases the complexity and production cost of the washing and impurity removal process; and in the subsequent high-temperature carbonization process, the metal impurities in the ash will be reduced to metal elements and then agglomerated. The agglomeration of metal elements will cause the collapse of the carbon skeleton structure, especially the collapse of the capillary pore structure, thereby reducing the active ion storage space of the obtained carbon material, decreasing the capacity, and showing too small water vapor adsorption rate; at the same time, the metal impurities also have catalytic activity, which will cause the decomposition of the carbon skeleton structure to intensify in the cracking process, making the pore structure tend to form large mesopore structures and / or macropore structures, thereby causing the carbon skeleton structure to be poor in stability and the internal electrolyte immersion area ratio of the obtained carbon material to increase, the consumption of active ions when the SEI film is formed to increase, and the first irreversible capacity loss to increase, so the first coulombic efficiency of the carbon material is reduced. In some embodiments, the ash content in the cellulose biomass material can be 0wt%-5wt%, optionally 0wt%-4wt%, 0wt%-3wt%, 0wt%-2wt%, 0wt%-1wt%. In this way, the adverse effects of impurities on the carbon material can be reduced, the gravimetric capacity, the first coulombic efficiency, and the structural stability of the carbon material can be improved, and the true density of the carbon material can also be reduced.

[0129] In some embodiments, optionally, the cellulose content in the cellulose biomass material is greater than 0wt% and less than or equal to 100wt%, and the ash content is 0wt%-5wt%.

[0130] The cellulose biomass material can also contain hemicellulose. Hemicellulose is a small molecular weight amorphous polymer in biomass materials, which is volatile in the low-temperature pre-carbonization process due to its easy decomposition into small molecular sugars, thereby facilitating the formation of pore structures; but its content should not be too high, when higher than 70wt%, it will cause the carbon skeleton structure to be poor in stability, the closed pore effect to be poor, the content of large mesopore structures and / or macropore structures in the carbon material to increase, the internal electrolyte immersion area ratio of the carbon material to increase, the first irreversible capacity loss to increase, and the first coulombic efficiency to decrease. In some embodiments, the hemicellulose content in the cellulose biomass material can be 0wt%-70wt%, optionally 0wt%-60wt%, 0wt%-50wt%, 0wt%-40wt%, 0wt%-30wt%, 0wt%-20wt%.

[0131] The cellulose-based biomass material can also contain lignin. Lignin is a large-molecular organic substance containing benzene rings and having high cross-linking degree, which is helpful to the formation of carbon six-membered rings in the low-temperature pre-carbonization process, and is helpful to the improvement of the stability of the carbon skeleton structure, thereby being beneficial to the improvement of the rate performance of the secondary battery; but the controllability of the pore structure formed by lignin is poor, and thus when the content of lignin is too high, for example, greater than 60wt%, the platform capacity of the obtained carbon material has limited room for improvement. In some embodiments, the content of lignin in the cellulose-based biomass material is 0wt%-60wt%, which can be selected as 5wt%-60wt%, 10wt%-60wt%, 10wt%-50wt%, or 15wt%-50wt%.

[0132] In some embodiments, the content of cellulose in the cellulose-based biomass material is greater than 0wt% and less than or equal to 100wt%, the content of hemicellulose is 0wt%-70wt%, the content of lignin is 0wt%-60wt%, and the content of ash is 0wt%-5wt%. Alternatively, the content of cellulose in the cellulose-based biomass material is greater than or equal to 20wt% and less than 100wt%, the content of hemicellulose is 0wt%-30wt%, the content of lignin is 10wt%-60wt%, and the content of ash is 0wt%-2wt%. Thus, the obtained carbon material can better balance the high specific capacity, high first coulombic efficiency, and high structural stability, thereby further improving the energy density, service life, and rate performance of the secondary battery.

[0133] In some embodiments, the content of cellulose in the cellulose-based biomass material can be 100wt%, i.e., the cellulose-based biomass material can directly use cellulose as a carbon source. Thus, the obtained carbon material has high capacity, but the stability of the carbon skeleton structure formed during the preparation process is slightly decreased, thereby slightly reducing the improvement effect on the rate performance of the secondary battery.

[0134] In the present application, the content of cellulose can be detected by acid hydrolysis anthrone colorimetry. Cellulose can be hydrolyzed to β-D-glucose under acidic conditions, and β-D-glucose can be dehydrated to form β-furfural compounds in a strong acid environment, which can be dehydrated with anthrone to form blue-green furfural derivatives. The product has a characteristic absorption peak at 620nm, and the content of cellulose can be quantitatively detected by the change of absorbance. For example, the acid can be sulfuric acid.

[0135] In the present application, the content of hemicellulose can be detected by DNS colorimetry. Hemicellulose is converted into reducing sugar after acid treatment, and the reducing sugar reacts with DNS to form a red-brown substance. The product has a characteristic absorption peak at 540nm, and the content of hemicellulose can be quantitatively detected by the change of absorbance.

[0136] In the present application, the lignin content can be detected by acetylation method. The phenolic hydroxyl group in lignin is acetylated to form acetyl lignin. The product has a characteristic absorption peak at 280 nm. The content of lignin can be quantitatively detected by the change of absorbance.

[0137] In the present application, the ash content can be determined according to GB / T 28731-2012.

[0138] In some embodiments, the cellulosic biomass material comprises one or more of woody biomass materials satisfying the above requirements of the present application, and optionally comprises one or more of hardwood, softwood and nut shell, for example, can comprise one or more of pine, bamboo and walnut shell.

[0139] In some embodiments, the preparation method further comprises the step of pretreating the cellulosic biomass material. The pretreatment process can include crushing, washing and drying steps. Crushing the cellulosic biomass material helps to load the material. Washing can remove impurities obviously attached to the surface of the cellulosic biomass material, avoiding its influence on the subsequent low-temperature pre-carbonization process. Drying can remove the water attached to the surface of the cellulosic biomass material and part of the bulk water, thereby reducing the influence of water on the subsequent low-temperature pre-carbonization process.

[0140] In some embodiments, the first heating rate is ≤10℃ / min, optionally 1℃ / min-10℃ / min, 1℃ / min-5℃ / min, 1℃ / min-3℃ / min. When the first heating rate is within a suitable range, the obtained carbonaceous material has 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 prepared carbonaceous material has poor controllability of pore structure and less capillary pore structure content, which shows a small water vapor adsorption rate.

[0141] In some embodiments, the first temperature T1 is 150-1000℃, for example, the first temperature T1 can be 200℃, 300℃, 400℃, 500℃, 600℃, 700℃, 800℃, 900℃, 1000℃ or any range consisting of any of the above values. Alternatively, the first temperature T1 is 200-900℃, 300-700℃, 300-600℃. When the first temperature is within the 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 temperature is increased, the formation of pore structure is more sufficient, and the content of capillary pore structure is increased; but when the first temperature is too high, the volatilization rate of volatile components is accelerated, the size of the formed pore structure is increased, the stability of the carbon skeleton structure is decreased, and it also leads to poor closed pore effect in the high-temperature carbonization process, the content of large mesopore structure and / or macropore structure in the carbonaceous material is increased, the proportion of the electrolyte immersion area in the carbonaceous material is increased, the first irreversible capacity loss is increased, the first coulombic efficiency is reduced, at the same time, the content of capillary pore structure in the carbonaceous material is reduced, which shows a smaller water vapor adsorption rate.

[0142] In some embodiments, the first time t1 is 1-20h, and can be 5-20h. Those skilled in the art can select a suitable first time within the above range according to the first temperature and the first heating rate, for example, when the first temperature is higher and / or the first heating rate is smaller, the first time can be appropriately shortened.

[0143] 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 control the carbon skeleton structure and the surface, improve the low-temperature pre-carbonization effect, and obtain a carbonaceous material with a suitable water vapor adsorption rate.

[0144] In some embodiments, the second heating rate is ≤10℃ / min, and can be 0.5-10℃ / min. However, the present application is not limited thereto, and the second heating rate can be adjusted according to the actual situation.

[0145] In some embodiments, the second temperature T2 is 1000-1600°C, for example, can be 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 consisting of any of the aforementioned values. Alternatively, the second temperature T2 is 1200-1500°C. When the second temperature is within the appropriate 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, the carbonaceous material surface has more oxygen-containing functional groups, which have better hydrophilicity, so that the carbonaceous material exhibits a fast water vapor adsorption rate and short adsorption time, but the closed pore effect of the pore structure is poor, and there are more large mesoporous structures and / or macroporous structures in the carbonaceous material, which increases the proportion of electrolyte infiltration area in the carbonaceous material, increases the first irreversible capacity loss, and reduces the first coulombic efficiency. When the second temperature is high, the closed pore effect of the pore structure is good, which can reduce the consumption of active ions during the formation of SEI film, and increase the active ion storage sites of the carbonaceous material, thereby increasing the capacity and first coulombic efficiency of the carbonaceous material; but when the second temperature is too high, the microstructure of the carbonaceous material changes in quality, which is not conducive to active ion storage, and exhibits a reduced water vapor adsorption rate.

[0146] In some embodiments, the second time t2 is 1-12h, and can be 3-10h. Those skilled in the art can select a suitable first time within the above range according to the second temperature and the second heating rate, for example, when the second temperature is high and / or the second heating rate is low, the second time can be appropriately shortened.

[0147] In S30, by adjusting one or more of the second heating rate, the second temperature and the second time within the above range, the closed pore effect of the pore structure is improved, the high-temperature carbonization treatment effect is improved, and a carbonaceous material with a suitable water vapor adsorption rate is obtained.

[0148] In some embodiments, t1+t2 is 10-30h. Thus, the obtained carbonaceous material has a suitable water vapor adsorption rate, high capacity, high first coulombic efficiency and high structural stability.

[0149] In some embodiments, after S20 and before S30, there is further included a step of: subjecting the first intermediate product obtained in S20 to a crushing treatment, or subjecting the first intermediate product obtained in S20 to a washing and impurity removal treatment, or subjecting the first intermediate product obtained in S20 to a crushing treatment followed by a washing and impurity removal treatment, to obtain a first intermediate product with ash content ≤ 0.01wt%. The washing and impurity removal treatment process at least includes an acid solution washing step and an alkaline solution washing step. Thereby, it is helpful to further improve the gravimetric capacity, the first coulombic efficiency and the structural stability of the carbonaceous material, while it is also helpful to reduce the true density of the carbonaceous material.

[0150] The crushing treatment can reduce the particle size of the first intermediate product, and thereby it is helpful to obtain the carbonaceous material with the desired size. In some embodiments, the volume particle size Dv50 of the crushed particles is 4-6pm. In some embodiments, the volume particle size Dv90 of the crushed particles is 8-16pm. In some embodiments, the volume particle size Dv50 of the crushed particles is 4-6pm and the volume particle size Dv90 is 8-16pm. Of course, in some embodiments, the crushing step can also be omitted.

[0151] The washing and impurity removal treatment can remove inorganic impurities, water-soluble impurities, etc. in the first intermediate product, to avoid the metal impurities being reduced to metal elements and then agglomerated in the subsequent high-temperature carbonization process. Because the agglomeration of metal elements will cause the collapse of the carbon skeleton structure, especially the collapse of the capillary pore structure, thereby leading to the reduction of the active ion storage space of the obtained carbonaceous material and the reduction of the capacity; at the same time, the metal impurities also have catalytic activity, which will cause the decomposition of the carbon skeleton structure to be intensified in the cracking process, so that the pore structure tends to form large mesopore structure and / or macropore structure with larger size, thereby leading to the increase of the proportion of the internal electrolyte immersion area of the obtained carbonaceous material, the increase of the consumption of active ions when the SEI film is formed, the increase of the first irreversible capacity loss, and the reduction of the first coulombic efficiency. The washing and impurity removal treatment process at least includes an acid solution washing step and an alkaline solution washing step. The acid 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 that cannot react with acid in the first intermediate product, thereby being able to fully ensure the removal of impurities, reduce the adverse effects of impurities on the carbonaceous material, and improve the gravimetric capacity and the first coulombic efficiency of the carbonaceous material.

[0152] In the present application, the crushing treatment needs to be performed before the washing and impurity removal treatment, so that the first intermediate product is exposed to as much surface as possible during the subsequent washing and impurity removal, so as to facilitate the full contact between the particles and the washing liquid and improve the washing and impurity removal effect. If the crushing treatment is performed after the washing and impurity removal treatment, some large pieces of raw materials will basically remain in the original state after pyrolysis, and the washing liquid may not enter the bulk phase of the large pieces of particles, so that the impurities deeply wrapped in the bulk phase of the large pieces of particles cannot be removed, thereby resulting in an insignificant washing and impurity removal effect.

[0153] The crushing can employ 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 jet milling.

[0154] The sequence of the acidic solution washing and the alkaline solution washing is not particularly limited. In some embodiments, the washing and impurity removal treatment process sequentially includes the following steps: acidic solution washing, water washing, alkaline solution washing, water washing, and drying; or, the washing and impurity removal treatment process sequentially includes the following steps: alkaline solution washing, water washing, acidic solution washing, water washing, and drying. Deionized water can be used for water washing, and the water washing can be performed once or multiple times until the pH of the filtrate is neutral (i.e., pH is 7±0.5), and it is considered that the water washing step is completed. The drying can be air drying or vacuum drying until the mass change rate of the material is ≤0.1wt% after 2h, and it is considered that the drying step is completed.

[0155] The present application does not have particular limitations on the solute type, concentration, washing temperature, and washing time of the acidic solution and the alkaline solution, and can ensure that the impurities are fully removed.

[0156] In some embodiments, the H + The concentration is 0.1mol / L-6moL / L, which can be 1mol / L-6moL / L.

[0157] In some embodiments, the washing temperature of the acidic solution is 10℃-95℃, which can be 30℃-95℃.

[0158] In some embodiments, the washing time of the acidic solution is 1h-24h, which can be 10h-24h.

[0159] 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.

[0160] By adjusting one or more of the H + The concentration, the washing temperature, the washing time, the solute type, etc. of the acidic solution within the above ranges are conducive to achieving sufficient washing and better removing metal impurities.

[0161] In some embodiments, the OH - The concentration is 0.1 mol / L-6 moL / L, and can be 1 mol / L-6 moL / L.

[0162] In some embodiments, the washing temperature of the alkaline solution is 10℃-95℃, and can be 30℃-95℃.

[0163] In some embodiments, the washing time of the alkaline solution is 1h-24h, and can be 10h-24h.

[0164] In some embodiments, the solute of the alkaline solution includes NaOH, KOH or a combination thereof, and the solvent includes water.

[0165] By adjusting one or more of the OH - The concentration, the washing temperature, the washing time, the solute type, etc. of the alkaline solution within the above ranges are conducive to achieving sufficient washing.

[0166] In some embodiments, the washing and impurity removal process step can also be omitted.

[0167] In some embodiments, when the ash content of the obtained first intermediate product is ≥0.5wt%, the washing and impurity removal process needs to be performed to ensure that the ash content in the material before the high-temperature carbonization process is ≤0.01wt%.

[0168] The type of the protective gas atmosphere in S20 and S30 is not particularly limited in the present application, and in some embodiments, the protective gas includes nitrogen, inert gas or a combination thereof, and optionally, the inert atmosphere includes argon, helium or a combination thereof. Optionally, the volume concentration of the gas can be 99.9% or more.

[0169] In some embodiments, the preparation method further includes: S40, crushing: crushing the carbonaceous material obtained in S30, at this time, the agglomerated carbonaceous material in the preparation process can be crushed to meet the required particle size, so as to facilitate the preparation of the negative electrode slurry and the negative electrode sheet. Of course, in some embodiments, this step can be omitted.

[0170] In some embodiments, the preparation method comprises the following steps: providing a carbon source: the carbon source is a cellulosic biomass material, the cellulose content in the cellulosic biomass material is greater than 0wt% and less than or equal to 100wt%, and the ash content is 0wt%-5wt%; low-temperature pre-carbonization treatment: the carbon source is heated to 150℃-1000℃, optionally 300℃-700℃, at a rate of ≤10℃ / min under a protective gas atmosphere, and then treated 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℃, at a rate of ≤10℃ / min under a protective gas atmosphere, and then treated for 1h-12h, optionally 3h-10h, to obtain a carbonaceous material, wherein the adsorption rate v of the carbonaceous material satisfies 0.015≤v≤0.050 when the adsorption test is carried out using water vapor under the condition of 25℃, 40% RH constant temperature and humidity. The carbonaceous material obtained thereby can better balance the 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.

[0171] In some embodiments, the preparation method comprises the following steps: providing a carbon source: the carbon source is a cellulosic biomass material, the cellulose content in the cellulosic biomass material is greater than 0wt% and less than or equal to 100wt%, and the ash content is 0wt%-5wt%; low-temperature pre-carbonization treatment: the carbon source is heated to 150℃-1000℃, optionally 300℃-700℃, at a rate of ≤10℃ / min under a protective gas atmosphere, and then treated 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 treated for 1h-12h, optionally 3h-10h, to obtain a carbonaceous material, wherein the adsorption rate v of the carbonaceous material satisfies 0.015≤v≤0.050 when the adsorption test is carried out using water vapor under the condition of 25℃, 40% RH constant temperature and humidity. The carbonaceous material obtained thereby can better balance the 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 comprises the following steps: providing a carbon source: the carbon source is a cellulosic biomass material, the cellulose content in the cellulosic biomass material is greater than 0wt% and less than or equal to 100wt%, and the ash content is 0wt%-5wt%; low-temperature pre-carbonization treatment: the carbon source is heated to 150-1000℃, optionally 300-700℃, at a rate of ≤10℃ / min under a protective gas atmosphere, and then held for 1-20h, optionally 5-20h, to obtain a first intermediate product; high-temperature carbonization treatment: the obtained first intermediate product is crushed to a volume particle size Dv50 of 4-6μm and / or a volume particle size Dv90 of 8-16μm, and then sequentially subjected to acid solution washing, water washing, alkaline solution washing, water washing, and drying steps, and then heated to 1000-1600℃, optionally 1200-1500℃, at a rate of ≤10℃ / min under a protective gas atmosphere, and then held for 1-12h, optionally 3-10h, to obtain a carbonaceous material, wherein the adsorption rate v of the carbonaceous material satisfies 0.015≤v≤0.050 when the adsorption test is carried out using water vapor under the condition of 25℃, 40% RH constant temperature and humidity. The carbonaceous material obtained in this way can better balance the high gravimetric capacity, high first coulombic efficiency and high structural stability, thereby further improving the energy density, service life and rate performance of the secondary battery.

[0173] The preparation method of the second aspect of the embodiments of the present application can prepare the carbonaceous material of any one of the embodiments of the first aspect of the embodiments of the present application. The preparation method of the carbonaceous material provided by the present application is simple in process and suitable for commercial production. The preparation method of the carbonaceous material provided by the present application does not need to add additional conductive agents or other additives, so that the carbonaceous material obtained by the preparation method provided by the present application has a lower content of heteroatoms.

[0174] Secondary battery

[0175] The third aspect of the embodiments of the present application provides a secondary battery.

[0176] The secondary battery mentioned in the embodiments or embodiments of the present application refers to a single physical module comprising one or more battery monomers to provide higher voltage and capacity. For example, the secondary battery mentioned in the present application can include battery monomers, battery modules or battery packs, etc. The battery monomer is the smallest unit that constitutes the secondary battery, which can realize the function of charging and discharging by itself. The present application does not have special restrictions on the shape of the battery monomer, which can be cylindrical, square or any other shape. Figure 1 is a battery monomer 5 in a square structure as an example.

[0177] In some embodiments, a single battery cell includes an electrode assembly and an electrolyte, and the single battery cell may also include an outer packaging. The outer packaging can be used to encapsulate the electrode assembly and the electrolyte. The outer packaging can be a rigid shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging can also be a flexible package, such as a pouch-type flexible package. The material of the flexible package can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0178] Electrode assemblies typically include positive and negative electrodes. During the charging and discharging process of a secondary battery, active ions move back and forth between the positive and negative electrodes, inserting and extracting. The electrolyte acts as a conductor for these active ions between the positive and negative electrodes. Electrode assemblies can be manufactured using winding and / or stacking processes.

[0179] In some embodiments, such as Figure 2 As shown, the outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates enclosing a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 is used to cover the opening to close the receiving cavity. Electrode assemblies 52 are encapsulated in the receiving cavity. The number of electrode assemblies 52 contained in the battery cell 5 may be one or more, and can be adjusted as needed.

[0180] In some embodiments of this application, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module. Figure 3 This is a schematic diagram of battery module 4 as an example. Figure 3 As shown, in battery module 4, multiple battery cells 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple battery cells 5 can be fixed in place using fasteners.

[0181] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0182] In some embodiments, the battery modules described above 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. Figure 4 and Figure 5 This is a schematic diagram of battery pack 1 as an example. Figure 4 and Figure 5As shown, the battery pack 1 can include a battery case and a plurality of battery modules 4 disposed in the battery case. The battery case includes an upper case 2 for capping a lower case 3 and forms an enclosed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery case in any manner.

[0183] [Anode electrode sheet]

[0184] In some embodiments, the anode electrode sheet includes an anode current collector and an anode film layer disposed on at least one surface of the anode current collector. For example, the anode current collector has two surfaces opposite in the thickness direction of itself, and the anode film layer is disposed on either one or both of the two opposite surfaces of the anode current collector.

[0185] In some embodiments, the anode film layer includes the carbonaceous material of the first aspect of the embodiments or the carbonaceous material prepared by the method of the second aspect of the embodiments. Thereby, the secondary battery can have high energy density, long service life, and good rate performance at the same time.

[0186] In some embodiments, the anode film layer can further include other anode active materials in addition to the carbonaceous material described above. In some embodiments, the other anode 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 can include one or more of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy materials. The tin-based materials can include one or more of elemental tin, tin oxide, and tin alloy materials.

[0187] In some embodiments, the anode film layer can optionally further include an anode conductive agent. The present application does not have a particular limitation on the type of the anode conductive agent, and as an example, the anode conductive agent can include one or more of super conductive carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0188] In some embodiments, the anode film layer can optionally further include an anode binder. The present application does not have a particular limitation on the type of the anode binder, and as an example, the anode binder can include one or more of styrene butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethylacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0189] In some embodiments, the negative electrode film layer can optionally further include other auxiliary agents. As an example, the other auxiliary agents can include thickening agents, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc.

[0190] In some embodiments, the negative electrode current collector can employ a metal foil or a composite current collector. As an example of the metal foil, a copper foil can be employed. The composite current collector can 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 can 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 can include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0191] The negative electrode film layer is generally formed by coating a negative electrode slurry on a negative electrode current collector, drying, and cold-pressing. The negative electrode slurry is generally formed by dispersing a negative electrode active material, an optional conductive agent, an optional binder, and other optional auxiliary agents in a solvent and stirring uniformly. The solvent can be N-methyl pyrrolidone (NMP) or deionized water, but is not limited thereto.

[0192] The negative electrode tab does not exclude other additional functional layers other than the negative electrode film layer. For example, in some embodiments, the negative electrode tab described in the present application further includes a conductive primer layer (e.g., composed of a conductive agent and a binder) disposed on the surface of the negative electrode current collector, sandwiched between the negative electrode current collector and the negative electrode film layer; in some embodiments, the negative electrode tab described in the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0193] [Positive electrode tab]

[0194] In some embodiments, the positive electrode tab 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 opposite in the thickness direction thereof, and the positive electrode film layer is disposed on either one or both of the two opposite surfaces of the positive electrode current collector.

[0195] The positive current collector can employ a metal foil or a composite current collector. As an example of a metal foil, an aluminum foil can be employed. The composite current collector can 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 can include one or more of aluminum, an aluminum alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, and a silver alloy. As an example, the polymer material base layer can include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0196] The positive electrode film layer generally includes a positive 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 current collector, drying, and cold-pressing. The positive electrode slurry is generally formed by dispersing and uniformly stirring a positive active material, an optional conductive agent, an optional binder, and any other components in a solvent. The solvent can be N-methyl pyrrolidone (NMP), but is not limited thereto. As an example, the binder used in the positive electrode film layer can include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylic resin. As an example, the conductive agent used in the positive electrode film layer includes one or more of super P, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0197] The positive active material can employ a positive active material for a secondary battery known in the art.

[0198] When the secondary battery of the present application is a lithium ion battery, the positive active material can include, but is not limited to, one or more of a lithium-containing transition metal oxide, a lithium-containing phosphate, and a modified compound of each thereof. Examples of the lithium-containing transition metal oxide can 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 a modified compound of each thereof. Examples of the lithium-containing phosphate can include, but are not limited to, one or more of lithium iron phosphate, a composite of lithium iron phosphate and carbon, lithium manganese phosphate, a composite of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite of lithium manganese iron phosphate and carbon, and a modified compound of each thereof.

[0199] In some embodiments, in order to further increase the energy density of the secondary battery, the positive active material for a lithium ion battery can include a compound represented by the general formula Li a Ni b Coc M d O e A f One or more of lithium transition metal oxides and their modified compounds. 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.

[0200] As an example, positive electrode active materials for lithium-ion batteries may include LiCoO2, LiNiO2, LiMnO2, LiMn2O4, and 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.

[0201] When the secondary battery of this 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, polyanionic materials (such as phosphates, fluorophosphates, pyrophosphates, sulfates, etc.), and Prussian blue materials.

[0202] As an example, positive electrode active materials for sodium-ion batteries may include NaFeO2, NaCoO2, NaCrO2, NaMnO2, NaNiO2, and 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 materials with the general formula X p M' q (PO4)r O x Y 3-x one or more of the materials of general formula X p M’ q (PO4) r O x Y 3-x , 0 < p < 4, 0 < q < 2, 1 < r < 3, 0 < x < 2, X comprises one or more selected from H + , Li + , Na + , K + , and NH4 + , M’ is a transition metal cation, optionally comprising one or more selected from V, Ti, Mn, Fe, Co, Ni, Cu, and Zn, and Y is a halide anion, optionally comprising one or more selected from F, Cl, and Br.

[0203] In the present application, the modification compound of each of the above positive electrode active materials can be a doping modification and / or a surface coating modification to the positive electrode active material.

[0204] [Electrolyte]

[0205] The type of the electrolyte is not particularly limited in the present application, and can be selected according to actual needs. For example, the electrolyte can be selected from at least one of a solid-state electrolyte and a liquid electrolyte (i.e., electrolyte solution).

[0206] In some embodiments, the electrolyte employs an electrolyte solution comprising an electrolyte salt and a solvent.

[0207] The type of the electrolyte salt is not particularly limited, and can be selected according to actual needs.

[0208] When the secondary battery of the present application is a lithium ion battery, as an example, the electrolyte salt can comprise one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonylimide (LiFSI), lithium bis-trifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoro-oxalato-borate (LiDFOB), lithium difluoro-oxalato-borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluoro-dioxalato-phosphate (LiDFOP), and lithium tetrafluoro-oxalato-phosphate (LiTFOP).

[0209] When the secondary battery of the present application is a sodium-ion battery, the electrolyte salt can include one or more of sodium hexafluorophosphate (NaPF6), sodium tetrafluoroborate (NaBF4), sodium perchlorate (NaClO4), sodium hexafluoroarsenate (NaAsF6), sodium bisfluorosulfonylimide (NaFSI), sodium bis-trifluoromethanesulfonylimide (NaTFSI), sodium trifluoromethanesulfonate (NaTFS), sodium difluoro oxalato borate (NaDFOB), sodium bisoxalate borate (NaBOB), sodium difluorophosphate (NaPO2F2), sodium difluoro di-oxalate phosphate (NaDFOP), and sodium tetrafluoro oxalate phosphate (NaTFOP).

[0210] The kind of the solvent is not particularly limited, and can be selected according to actual needs. In some embodiments, as an example, the solvent can include one or more of ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0211] In some embodiments, the electrolyte solution can also optionally include an additive. For example, the additive can include a negative electrode film-forming additive, can also include a positive electrode film-forming additive, and can also include an additive capable of improving certain performance of the battery, such as an additive capable of improving overcharge performance of the battery, an additive capable of improving high-temperature performance of the battery, an additive capable of improving low-temperature power performance of the battery, etc.

[0212] [Separator]

[0213] In some secondary batteries using electrolyte solutions, and some secondary batteries using solid-state electrolytes, a separator is also included. The separator is disposed between the positive electrode sheet and the negative electrode sheet, and functions to separate. The kind of the separator is not particularly limited in the present application, and any known porous structure separator having good chemical stability and mechanical stability can be selected.

[0214] In some embodiments, the material of the separator can include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film, or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of the layers can be the same or different.

[0215] [Preparation method]

[0216] The preparation method of the secondary battery of the present application is 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, the negative electrode sheet can be formed into an electrode assembly through a winding process and / or a stacking process, the electrode assembly is placed in an outer package, the electrolyte is injected after drying, and the battery monomer is obtained through processes such as vacuum packaging, standing, formation, shaping, etc. A plurality of battery monomers can further be connected in series or in parallel or in a hybrid manner to form a battery module. A plurality of battery modules can further be connected in series or in parallel or in a hybrid manner to form a battery pack. In some embodiments, a plurality of battery monomers can also be directly connected to form a battery pack.

[0217] Electricity-using device

[0218] The fourth aspect of the embodiments of the present application provides a power consuming device, which comprises the secondary battery of the present application. The secondary battery can be used as a power source of the power consuming device, or can be used as an energy storage unit of the power consuming device. The power consuming device can be, but is not limited to, a mobile device (such as a mobile phone, a tablet computer, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc.

[0219] The specific type of the secondary battery, such as a battery monomer, a battery module or a battery pack, can be selected according to the use requirements of the power consuming device.

[0220] Figure 6 is a schematic diagram of a power consuming device as an example. The power consuming device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirements of high power and high energy density of the power consuming device, a battery pack or a battery module can be used as a power source.

[0221] The power consuming device as another example can be a mobile phone, a tablet computer, a notebook computer, etc. The power consuming device usually requires thinning, and a battery monomer can be used as a power source.

[0222] Examples

[0223] The present application is described in more detail by the following examples, which are merely illustrative and not limiting, as various modifications and changes in the embodiments described herein will be obvious to those skilled in the art. Unless otherwise indicated, all parts, percentages, and ratios reported herein are on a mass basis, and all reagents used in the examples are commercially available or synthesized according to conventional methods and used without further purification, and the instruments used in the examples are commercially available.

[0224] Example 1

[0225] The pine wood used as carbon source has 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%.

[0226] The pine wood was heated to 150°C (as a first temperature T1) at a first heating rate of 1°C / min under a nitrogen atmosphere, and then held for 10 h (as a first time t1), and then cooled to room temperature to obtain a first intermediate product.

[0227] The first intermediate product was broken by a jet mill to a volume particle size Dv50 of 4-6 μm, and then washed with 3 mol / L hydrochloric acid aqueous solution at 50°C for 10 h, and then washed with deionized water until neutral, and then washed with 3 mol / L NaOH aqueous solution at 80°C for 20 h, and then washed with deionized water until neutral, and finally dried by blowing air to remove water to obtain a first intermediate product with an ash content of ≤0.01 wt%.

[0228] The first intermediate product obtained above was heated to 1400°C (as a second temperature T2) at a second heating rate of 0.5°C / min under a nitrogen atmosphere, and then held for 6 h (as a second time t2), and then cooled to obtain a carbonaceous material.

[0229] The carbonaceous material with a mass of m1 was uniformly placed in a container in a constant temperature and humidity chamber at 25°C and 40% RH (i.e., the ratio of the water vapor partial pressure in air to the saturated vapor pressure of water is 40%), and the bulk thickness of the carbonaceous material was ≤5 mm, and the water vapor adsorption mass m2 and the water vapor adsorption time t of the carbonaceous material when the water vapor adsorption reached equilibrium were recorded, and then the water vapor adsorption rate v = m2 / (m1 x t), the unit of m1 is g, the unit of m2 is g, and the unit of t is h.

[0230] The true density of the carbonaceous material was tested by the Archimedes immersion volume displacement method using n-butanol as the medium.

[0231] Examples 2-19 and Comparative Examples 1-7

[0232] The carbonaceous material was prepared according to the method of Example 1, except that the process parameters of the carbonaceous material were adjusted, and the details are shown in Table 1.

[0233] Performance test

[0234] The carbonaceous material prepared in each example and comparative example was mixed with a binder styrene-butadiene rubber (SBR), a thickening agent sodium carboxymethyl cellulose (CMC-Na), and a conductive agent carbon black in a mass ratio of 96.2:1.8:1.2:0.8 in an appropriate amount of solvent deionized water to form a uniform negative electrode slurry. The negative electrode slurry was uniformly coated on the surface of a negative electrode current collector copper foil, which was dried in an oven and then used. Ethylene carbonate (EC), methyl ethyl 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 organic solvent to prepare an electrolyte with a concentration of 1 mol / L. Then, a CR2430 button cell was assembled in an argon glove box with a metal sodium sheet as the counter electrode and a polyethylene (PE) film as the separator.

[0235] At 25°C, the button cell prepared in each example and comparative example was first discharged at a current density of 10 mA / g to 0V, and the first circle discharge capacity of the button cell was recorded. Then, the button cell was charged at a current density of 10 mA / g to 2.0V, and the first circle charge capacity of the button cell was recorded.

[0236] The reversible capacity (mAh / g) of the carbonaceous material = the first circle charge capacity of the button cell / the mass of the carbonaceous material.

[0237] The first cycle coulombic efficiency (%) of the carbonaceous material = the first circle charge capacity of the button cell / the first circle discharge capacity of the button cell x 100%.

[0238] After the button cell was fully charged and discharged at 0.33C and 1C, respectively, the discharge capacities at 0.33C and 1C were obtained, and the ratio of the discharge capacity at 1C to the discharge capacity at 0.33C was used to represent the rate performance. The higher the ratio, the better the rate performance.

[0239] Table 1

[0240]

[0241]

[0242] Table 2

[0243]

[0244]

[0245] Figures 7 to 9 is a scanning electron microscope image of the carbonaceous material provided by the present application at different magnifications, as shown in FIG. 1. Figures 7 to 9 As shown in Table 2, when the carbonaceous material satisfies the water vapor adsorption rate v between 0.015 and 0.050 under the constant temperature and humidity condition of 25°C and 40% RH, the carbonaceous material can have higher gram capacity, higher first coulombic efficiency and good rate performance.

[0246] The carbonaceous material prepared by Comparative Examples 1-7 has a water vapor adsorption rate v less than 0.015 or greater than 0.050 under the constant temperature and humidity condition of 25°C and 40% RH, and thus cannot have higher gram capacity, higher first coulombic efficiency and good rate performance.

[0247] Comparative Example 1 uses rice husk as the carbon source, and the ash content is higher than 5 wt%. Since the ash not only produces catalytic reactions during the low-temperature pre-carbonization process, consumes C element content, and reduces active ion storage sites, but also reduces metal impurities in the ash into metal elements during the subsequent high-temperature carbonization process, and the metal element aggregation will cause the collapse of the carbon skeleton structure, especially the collapse of the capillary pore structure, which will further reduce the active ion storage space of the obtained carbonaceous material, decrease the capacity, and result in too small water vapor adsorption rate. At the same time, the metal impurities have catalytic activity, which will cause the decomposition of the carbon skeleton structure to be intensified during the cracking process, and the pore structure tends to form large mesoporous structure and / or macroporous structure, which will increase the proportion of the electrolyte immersion area in the carbonaceous material, increase the consumption of active ions when the SEI film is formed, increase the first irreversible capacity loss, and reduce the first coulombic efficiency.

[0248] In Comparative Example 2, the low-temperature pre-carbonization process is not performed during the preparation of the carbonaceous material, which results 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 high proportion of electrolyte immersion area in the carbonaceous material, high first irreversible capacity loss, and low first coulombic efficiency.

[0249] The test results of Examples 1-19 also show that when the water vapor adsorption time t of the carbonaceous material further satisfies 4.5h to 7h, the carbonaceous material can have higher gram capacity, first coulombic efficiency and / or rate performance.

[0250] The test results of Examples 1-19 also show that when the true density p of the carbonaceous material further satisfies 1.3g / cm 3 -1.7g / cm 3 , the carbonaceous material can have higher gram capacity, first coulombic efficiency and / or rate performance.

[0251] Note that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and embodiments having substantially the same configuration, function, and effect as the technical idea of the present application are included in the technical scope of the present application. In addition, other modes constructed by combining part of the configurations of the embodiments in a manner that a person skilled in the art can think of within the scope of the present application are also included in the scope of the present application.

Claims

1. A carbonaceous material, wherein, The adsorption rate v of the carbonaceous material in the adsorption test using water vapor under the constant temperature and humidity condition of 25 DEG C and 40% RH satisfies 0.015≤v≤0.050, The water vapor adsorption test is performed under the following conditions: in a constant temperature and humidity chamber at 25 DEG 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 m1 is g, the unit of m2 is g, and the unit of t is h; The true density p of the carbonaceous material is 1.0 g / cm 3 - 2.2 g / cm 3 .

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 of the carbonaceous material when adsorbing water vapor to reach equilibrium is 1 h-12 h.

4. The carbonaceous material according to claim 3, wherein, The water vapor adsorption time t of the carbonaceous material when adsorbing water vapor to reach equilibrium is 4.5 h-7 h.

5. The carbonaceous material of claim 1, wherein, The true density p of the carbonaceous material is 1.3 g / cm 3 -1.7 g / cm 3 .

6. The carbonaceous material of claim 1, wherein, The carbonaceous material comprises a plurality of nanopore structures.

7. The carbonaceous material according to claim 6, wherein, The carbonaceous material comprises a plurality of pore structures with a pore size of less than 10 nm.

8. The carbonaceous material according to claim 1, wherein, In the Raman spectrum of the carbonaceous material, I d / I g is 1.0-1.3, I d represents the intensity of the d-peak with a Raman shift in the range of 1350 ± 50 cm -1 -1, I g represents the intensity of the g-peak with a Raman shift in the range of 1580 ± 50 cm -1 -1; and / or, The interlayer spacing of the (002) crystal plane of the carbonaceous material is ≥0.37 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°.

9. The carbonaceous material according to claim 8, wherein, In the Raman spectrum of the carbonaceous material, I d / I g is 1.05-1.15; and / or, The interlayer spacing of the (002) crystal plane of the carbonaceous material is 0.37 nm-0.42 nm.

10. The carbonaceous material of claim 1, 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 carbonaceous material has a specific surface area of 0.1 m 2 / g-20m 2 / g; (4) the powder compaction density of the carbonaceous material under a force of 50000 N is 0.90 g / cm 3 - 1.05 g / cm 3 ; (5) the carbonaceous material has a tapped density of 0.78 g / cm 3 -0.95 g / cm 3 .

11. The carbonaceous material according to claim 10, wherein, The carbonaceous material satisfies at least one of the following conditions (1) to (3): (1) the carbonaceous material has a specific surface area of 1 m 2 / g-20m 2 / g; (2) the powder compaction density of the carbonaceous material under the action of 50000N force is 0.92g / cm 3 -1.02g / cm 3 ; (3) the carbonaceous material has a tapped density of 0.83 g / cm 3 -0.93 g / cm 3 .

12. A preparation method of a carbonaceous material, comprising the following steps: S10, providing a carbon source: the carbon source is a cellulose-based biomass material; S20, low-temperature pre-carbonization treatment: the carbon source is treated under a protective gas atmosphere, and after being heated to a first temperature T1 at a first heating rate, the temperature is maintained for a first time t1 to obtain a first intermediate product; S30, high-temperature carbonization treatment: the obtained first intermediate product is treated by keeping at a second temperature T2 for a second time t2 after being heated to the second temperature T2 at a second heating rate in a protective gas atmosphere, to obtain a carbonaceous material, wherein, The adsorption rate v of the carbonaceous material in the adsorption test using water vapor under the constant temperature and humidity condition of 25 DEG C and 40% RH satisfies 0.015≤v≤0.050, the water vapor adsorption test is performed under the following conditions: in a constant temperature and humidity chamber at 25 DEG 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 m1 is g, the unit of m2 is g, and the unit of t is h; The true density p of the carbonaceous material is 1.0 g / cm 3 - 2.2 g / cm 3 .

13. The method of claim 12, wherein, The cellulose content in the cellulose-based biomass material is greater than 0 wt% and less than or equal to 100 wt%, and the ash content is 0 wt%-5 wt%.

14. The method according to claim 12, wherein, The cellulose content in the cellulose-based 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 0wt%-2wt%.

15. The method of claim 13, wherein, The hemicellulose content in the cellulosic biomass material is 0wt%-70wt%; and / or, The lignin content in the cellulosic biomass material is 0wt%-60wt%.

16. The method of claim 15, wherein, The hemicellulose content in the cellulosic biomass material is 0wt%-30wt%; and / or, The lignin content in the cellulosic biomass material is 10wt%-60wt%.

17. The method of claim 13, wherein, The cellulosic biomass material comprises one or more of woody biomass materials.

18. The method of claim 13, wherein, The cellulosic biomass material comprises one or more of hardwood, softwood and nut shell.

19. The method of claim 13, wherein, The cellulosic biomass material comprises one or more of pine, bamboo and walnut shell.

20. The method of claim 12, wherein, The first temperature increasing rate is 1℃ / min-10℃ / min; and / or, The first temperature T1 is 150℃-1000℃; and / or, The first time t1 is 1h-20h.

21. The method of claim 20, wherein, The first temperature increasing rate is 1℃ / min-3℃ / min; and / or, The first temperature T1 is 300℃-700℃; and / or, The first time t1 is 5h-20h.

22. The method of claim 12, wherein, The second temperature increasing rate is ≤10℃ / min; and / or, The second temperature T2 is 1000℃-1600℃; and / or, The second time t2 is 1h-12h.

23. The method of claim 22, wherein, The second temperature increasing rate is 0.5℃ / min-10℃ / min; and / or, The second temperature T2 is 1200℃-1500℃; and / or, The second time t2 is 3h-10h.

24. The method of claim 12, wherein, t1+t2 is 10h-30h.

25. The method of claim 12, wherein, After S20 and before S30, further comprising a step of: subjecting the first intermediate product obtained in S20 to a crushing treatment, or subjecting the first intermediate product obtained in S20 to a washing and impurity removing treatment, or subjecting the first intermediate product obtained in S20 to a crushing treatment followed by a washing and impurity removing treatment, to obtain a first intermediate product with an ash content ≤0.01wt%, wherein the washing and impurity removing treatment process at least comprises an acid solution washing step and an alkaline solution washing step.

26. The method of claim 25, wherein, The washing and impurity removing treatment process comprises the following steps in sequence: acid solution washing, water washing, alkaline solution washing, water washing and drying; or, the washing and impurity removing treatment process comprises the following steps in sequence: alkaline solution washing, water washing, acid solution washing, water washing and drying.

27. The method of claim 25, wherein, The acid solution satisfies at least one of the following conditions (1) to (4): (1) the H + concentration is 0.1-6 mol / L; (2) the washing temperature of the acid solution is 10℃-95℃; (3) the washing time of the acid solution is 1h-24h; (4) the solute of the acid solution comprises one or more of hydrochloric acid, nitric acid, sulfuric acid and perchloric acid, and the solvent comprises water.

28. The method of claim 27, wherein, The acid solution satisfies at least one of the following conditions (1) to (3): (1) the H + concentration is 1 mol / L-6 moL / L; (2) the washing temperature of the acidic solution is 30°C to 95°C; (3) the washing time of the acidic solution is 10 h to 24 h.

29. The method of claim 25, wherein, The basic solution satisfies at least one of the following conditions (1) to (4): (1) the OH concentration of the basic solution is 0.1-6 mol / L - 0.1-6 mol / L; (2) the washing temperature of the basic solution is 10°C to 95°C; (3) the washing time of the basic solution is 1 h to 24 h; (4) the solute of the basic solution includes NaOH, KOH, or a combination thereof, and the solvent includes water.

30. The method of claim 29, wherein, The basic solution satisfies at least one of the following conditions (1) to (3): (1) the OH - concentration is 1 mol / L-6 moL / L; (2) the washing temperature of the basic solution is 30°C to 95°C; (3) the washing time of the basic solution is 10 h to 24 h.

31. A secondary battery comprising a negative electrode sheet comprising the carbonaceous material of any one of claims 1-11 or prepared by the method of any one of claims 12-30.

32. An electric device comprising the secondary battery of claim 31.

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