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

Abstract

The invention provides a carbonaceous material and a preparation method thereof, and a secondary battery and an electric device containing the carbonaceous material, the carbonaceous material has an O element content A tested by an X-ray photoelectron spectroscopy method and an O element content B tested by an elemental analysis method, and the carbonaceous material satisfies A / B > = 3 and 5wt% < = A < = 20wt%. According to the carbonaceous material provided by the invention, the cycle performance and the rate capability of the secondary battery can be greatly improved.

Description

[0001] This application is a divisional application based on the invention with application number 202280091570.9, application date October 21, 2022, applicant CATL, and invention title "Carbon-based materials and their preparation methods, as well as secondary batteries and electrical devices containing the same". Technical Field

[0002] This application belongs to the field of battery technology, specifically relating to a carbonaceous material and its preparation method, as well as a secondary battery and electrical device containing the same. Background Technology

[0003] In recent years, rechargeable batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and many other fields. With the application and promotion of rechargeable batteries, their energy density, lifespan, and rate performance have received increasing attention. Graphite is the most commonly used negative electrode active material in rechargeable batteries, but its theoretical specific capacity is only 372 mAh / g, limiting the potential for energy density improvement; at the same time, the small interlayer spacing of graphite also limits the improvement of rate performance. Hard carbon, as a novel negative electrode active material, can achieve rapid insertion and extraction of active ions during the charging and discharging process of rechargeable batteries, thus showing great development potential. However, the cycle performance and rate performance of currently commercially available hard carbon materials are not ideal. Summary of the Invention

[0004] The purpose of this application is to provide a carbonaceous material and its preparation method, as well as a secondary battery and an electrical device containing the same, wherein the carbonaceous material enables the secondary battery to have significantly improved cycle performance and rate performance.

[0005] The first aspect of this application provides a carbonaceous material, wherein the content of O element in the carbonaceous material as determined by X-ray photoelectron spectroscopy is denoted as A, and the content of O element as determined by elemental analysis is denoted as B, and the carbonaceous material satisfies A / B≥3 and 5wt%≤A≤20wt%.

[0006] The inventors of this application made a surprising discovery during their research: when the carbonaceous material satisfies A / B≥3 and 5wt%≤A≤20wt%, the secondary battery can exhibit significantly improved cycle performance and rate performance. The carbonaceous material provided in this application has a high content of oxygen (O) on its surface. During charging (i.e., before the formation of the SEI film), negative charges can accumulate at the O atom sites on the carbonaceous material surface, thereby inducing the rapid decomposition of organic solvents such as esters or ethers in the electrolyte, and thus increasing the content of organic components in the SEI film. The inventors of this application also discovered during their research that these organic components have numerous advantages over inorganic components: First, the organic components in the SEI film have higher flexibility, which can improve the SEI film's resistance to deformation and maintain its stability during long-term cycling, thereby reducing the consumption of active ions during cycling and further improving the cycle performance of the secondary battery; Second, the organic components in the SEI film can increase the ionic conductivity on the negative electrode side, which is beneficial to further improving the rate performance of the secondary battery, while also preventing the reduction and precipitation of active ions on the negative electrode side during cycling, thus further improving the cycle performance of the secondary battery; Third, the O atoms on the surface of the carbonaceous material can also participate in the formation of the SEI film, which is beneficial to improving the adhesion of the SEI film to the surface of the carbonaceous material particles, and is beneficial to the high stability of the SEI film during long-term cycling, thereby reducing the consumption of active ions during cycling and further improving the cycle performance of the secondary battery.

[0007] In any embodiment of this application, 3 ≤ A / B ≤ 10, and optionally, 6 ≤ A / B ≤ 9.2. This helps to further improve the cycle performance and rate performance of the secondary battery.

[0008] In any embodiment of this application, 5wt%≤A≤16wt%, and optionally, 10wt%≤A≤16wt%. This helps to further improve the cycle performance and rate performance of the secondary battery.

[0009] In any embodiment of this application, 1.5wt%≤B≤6wt%, and optionally, 1.5wt%≤B≤3wt%. This helps to further improve the cycle performance and rate performance of the secondary battery.

[0010] In any embodiment of this application, the specific surface area of ​​the carbonaceous material is ≤10m². 2 / g, can be selected as 0.1m 2 / g-10m 2 / g. The carbonaceous material provided in this application has a low specific surface area, which helps to reduce the surface activity of the carbonaceous material, reduce the formation of SEI film, and thus reduce the irreversible consumption of active ions. As a result, the carbonaceous material can have higher specific capacity and first coulombic efficiency at the same time, and also enable the secondary battery to have better cycle performance and rate performance.

[0011] In any embodiment of this application, the carbonaceous material comprises a plurality of nanoporous structures.

[0012] In any embodiment of this application, in the Raman spectrum of the carbonaceous material, I d / I g The value is 0.90-1.25, and can be selected as 0.95-1.10. d This indicates that the Raman displacement is within 1350±50cm. -1 The d-peak intensity within the range, I g This indicates that the Raman displacement is within 1580±50cm. -1 The g-peak intensity is within the specified range. At this point, carbonaceous materials exhibit higher specific capacity and higher initial coulombic efficiency, while also possessing excellent rate performance.

[0013] In any embodiment of this application, the interlayer spacing of the (002) crystal plane of the carbonaceous material is ≥0.37nm, and can be selected as 0.37nm-0.42nm.

[0014] In any embodiment of this application, in the X-ray diffraction spectrum of the carbonaceous material, the 2θ value corresponding to the (002) crystal plane peak is between 22° and 24°.

[0015] In any embodiment of this application, the volumetric particle size Dv50 of the carbonaceous material is 3μm-15μm, and can be selected as 4μm-6μm.

[0016] In any embodiment of this application, the volumetric particle size Dv90 of the carbonaceous material is 8μm-30μm, and can be selected as 9μm-12μm.

[0017] When the volumetric particle size Dv50 and / or Dv90 of carbonaceous materials are within a suitable range, it is beneficial to improve the active ion and electron transport performance, thereby further improving the cycle performance and rate performance of secondary batteries.

[0018] In any embodiment of this application, the compacted density of the carbonaceous material powder under a force of 50,000 N is 0.92 g / cm³. 3 -1.05g / cm 3 The option is 0.95g / cm³. 3 -1.02g / cm 3 When the compaction density of carbonaceous material powder is within a suitable range, the compaction density of the negative electrode sheet can be increased, thereby improving the energy density of the secondary battery.

[0019] In any embodiment of this application, the tap density of the carbonaceous material is 0.80 g / cm³. 3 -0.95g / cm3 0.85g / cm³ is an optional value. 3 -0.90g / cm 3 When the tap density of carbonaceous materials is within a suitable range, the tap density of the negative electrode sheet can be increased, thereby improving the energy density of the secondary battery.

[0020] The second aspect of this application provides a method for preparing a carbonaceous material, comprising the following steps: S10, providing raw materials, the raw materials including hard carbon materials; S20, grinding the raw materials with a grinding media and an oxidizing solution in a grinding mill; S30, washing and drying the product obtained from grinding to obtain a carbonaceous material, wherein the O element content of the carbonaceous material as measured by X-ray photoelectron spectroscopy is denoted as A, and the O element content as measured by elemental analysis is denoted as B, and the carbonaceous material satisfies A / B≥3 and 5wt%≤A≤20wt%.

[0021] Currently, the cycle performance and rate performance of commercially available hard carbon materials are not ideal. The preparation method provided in this application can significantly optimize the cycle performance and rate performance of the raw materials (i.e., hard carbon materials), and the preparation method provided in this application has universality.

[0022] In any embodiment of this application, in S20, the dry weight ratio of the raw material to the mass of the grinding media is ≤1, and can be selected as 0.2-1. This improves production efficiency and ensures that the surface of the obtained carbonaceous material has a suitable content of oxygen-containing functional groups. Furthermore, the carbonaceous material can significantly improve the cycle performance and rate performance of the secondary battery.

[0023] In any embodiment of this application, in S20, the mass ratio of the dry weight of the raw material to the mass of the oxidizing solution is ≤0.6, and can be selected as 0.1-0.6. This can improve production efficiency on the one hand, and ensure that the surface of the obtained carbonaceous material has a suitable content of oxygen-containing functional groups on the other hand, and the carbonaceous material can also significantly improve the cycle performance and rate performance of the secondary battery.

[0024] In any embodiment of this application, in S20, the concentration of the oxidizing solution is ≥0.1 mol / L, and can be selected as 0.1 mol / L-10 mol / L. This improves production efficiency and ensures safe production, while also ensuring that the surface of the obtained carbonaceous material has a suitable content of oxygen-containing functional groups. Furthermore, the carbonaceous material can significantly improve the cycle performance and rate performance of the secondary battery.

[0025] In any embodiment of this application, in S20, the grinding time is 1h-24h, optionally 4h-16h. This allows the obtained carbonaceous material surface to have a suitable content of oxygen-containing functional groups, and the carbonaceous material can also significantly improve the cycle performance and rate performance of the secondary battery.

[0026] In any embodiment of this application, in S20, the solute in the oxidizing solution includes one or more selected from nitric acid, sulfuric acid, and perchloric acid, and the solvent includes water. This ensures that the surface of the obtained carbonaceous material has a suitable content of oxygen-containing functional groups, while avoiding the introduction of other impurity elements, thereby reducing the irreversible consumption of active ions.

[0027] In any embodiment of this application, in S20, the grinding speed is 100rpm-1200rpm.

[0028] In any embodiment of this application, in S20, the grinding instrument includes a ball mill.

[0029] In any embodiment of this application, in S20, the volume percentage of all materials in the grinder is 1 / 5 to 3 / 4, based on the volumetric capacity of the grinder. This improves both production efficiency and the wet grinding effect.

[0030] In any embodiment of this application, in S10, the volumetric particle size Dv50 of the raw material is 3μm-15μm, and can be selected as 4μm-6μm.

[0031] In any embodiment of this application, in S10, the volumetric particle size Dv90 of the raw material is 8μm-30μm, and can be selected as 9μm-12μm.

[0032] By adjusting the volumetric particle size Dv50 and / or Dv90 of the raw materials within a suitable range, it is beneficial to improve the active ion and electron transport performance of the obtained carbonaceous materials, thereby further improving the cycle performance and rate performance of the secondary battery.

[0033] In any embodiment of this application, the raw material is prepared by the following method: heating a carbon source to 1000℃-1600℃ at a rate of ≤10℃ / min under a protective gas atmosphere and holding it at that temperature for 1h-24h, and then crushing it to obtain the raw material.

[0034] A third aspect of this application provides a secondary battery comprising a negative electrode, wherein the negative electrode comprises the carbonaceous material of the first aspect of this application or the carbonaceous material prepared by the method of the second aspect of this application.

[0035] The fourth aspect of this application provides an electrical device that includes the secondary battery of the third aspect of this application.

[0036] The carbonaceous material provided in this application enables secondary batteries to have significantly improved cycle performance and rate performance. The electrical device of this application includes the secondary battery provided in this application, and therefore has at least the same advantages as the secondary battery. Attached Figure Description

[0037] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly described below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of one embodiment of the battery cell of this application.

[0039] Figure 2 This is an exploded view of one embodiment of the battery cell of this application.

[0040] Figure 3 This is a schematic diagram of one embodiment of the battery module of this application.

[0041] Figure 4 This is a schematic diagram of one embodiment of the battery pack of this application.

[0042] Figure 5 yes Figure 4 An exploded view of an embodiment of the battery pack shown.

[0043] Figure 6 This is a schematic diagram of one embodiment of an electrical device that uses a secondary battery as a power source, as described in this application.

[0044] The accompanying drawings are not necessarily drawn to scale. The reference numerals are explained as follows: 1 Battery pack, 2 Upper casing, 3 Lower casing, 4 Battery module, 5 Individual battery cell, 51 Housing, 52 Electrode assembly, 53 Cover plate. Detailed Implementation

[0045] The carbonaceous material and its preparation method, as well as embodiments of secondary batteries and power-consuming devices containing the same, are disclosed in detail below with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0046] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0047] Unless otherwise specified, all embodiments and optional embodiments of this application may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this application.

[0048] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions, and such technical solutions shall be deemed to be included in the disclosure of this application.

[0049] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0050] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0051] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0052] Unless otherwise specified, the terms used in this application have the common meanings as commonly understood by those skilled in the art.

[0053] Unless otherwise specified, the values ​​of the parameters mentioned in this application can be determined using various testing methods commonly used in the art, for example, according to the testing methods given in this application.

[0054] Unless otherwise specified, in this application, the term "active ion" refers to ions that can be inserted and extracted back and forth between the positive and negative electrodes of a secondary battery, including but not limited to lithium ions, sodium ions, etc.

[0055] In this application, the terms "multiple" or "various" refer to two or more kinds.

[0056] carbonaceous materials The first aspect of this application provides a carbonaceous material in which the content of O element measured by X-ray photoelectron spectroscopy (XPS) is denoted as A, and the content of O element measured by elemental analysis (EA) is denoted as B. The carbonaceous material satisfies A / B≥3 and 5wt%≤A≤20wt%.

[0057] The oxygen content measured by X-ray photoelectron spectroscopy is the oxygen content on the surface of the carbonaceous material, while the oxygen content measured by elemental analysis is the oxygen content of the entire carbonaceous material sample. Before X-ray photoelectron spectroscopy and elemental analysis, the carbonaceous material needs to be vacuum dried at 120°C for 12 hours and then sealed and stored in an aluminum-plastic bag.

[0058] X-ray photoelectron spectroscopy (XPS) is performed using an XPS spectrometer. A Thermo Fisher Scientific Nexsa / EscaLab 250Xi XPS spectrometer can be used.

[0059] Elemental analysis was performed using an elemental analyzer in O mode. This involved pyrolyzing the sample in a H2 / He mixture at 1150℃, followed by carbon reduction to CO, with the O content determined by thermal conductivity. Samples with a mass of 30 mg or more could be tested. Suitable instruments included the Elementar Vario Macro Cube (Germany) or Thermo Fisher Scientific Flash 2000 / Flash Smart (USA).

[0060] The inventors of this application made a surprising discovery during their research: when the carbonaceous material satisfies A / B≥3 and 5wt%≤A≤20wt%, the secondary battery can exhibit significantly improved cycle performance and rate performance. The carbonaceous material provided in this application has a high content of oxygen (O) on its surface. During charging (i.e., before the formation of the SEI film), negative charges can accumulate at the O atom sites on the carbonaceous material surface, thereby inducing the rapid decomposition of organic solvents such as esters or ethers in the electrolyte, and thus increasing the content of organic components in the SEI film. The inventors of this application also discovered during their research that these organic components have numerous advantages over inorganic components: First, the organic components in the SEI film have higher flexibility, which can improve the SEI film's resistance to deformation and maintain its stability during long-term cycling, thereby reducing the consumption of active ions during cycling and further improving the cycle performance of the secondary battery; Second, the organic components in the SEI film can increase the ionic conductivity on the negative electrode side, which is beneficial to further improving the rate performance of the secondary battery, while also preventing the reduction and precipitation of active ions on the negative electrode side during cycling, thus further improving the cycle performance of the secondary battery; Third, the O atoms on the surface of the carbonaceous material can also participate in the formation of the SEI film, which is beneficial to improving the adhesion of the SEI film to the surface of the carbonaceous material particles, and is beneficial to the high stability of the SEI film during long-term cycling, thereby reducing the consumption of active ions during cycling and further improving the cycle performance of the secondary battery.

[0061] When the ratio of oxygen (A / B) is less than 3 or A is less than 5 wt%, the oxygen content on the surface of the carbonaceous material is low, which is not conducive to the formation of a high-performance SEI film, resulting in less than ideal cycle performance and rate performance of the secondary battery. When A is greater than 20 wt%, the oxygen content on the surface of the carbonaceous material is too high. At this point, the hydrogen bonding between oxygen atoms and water molecules is too strong, leading to excessive water molecule clusters clogging the surface of the carbonaceous material, hindering the insertion and extraction of active ions, and thus resulting in less than ideal cycle performance and rate performance of the secondary battery. In addition, when the oxygen content on the surface of the carbonaceous material is too high, too many active ions are captured by oxygen atoms, which also hinders the continuity of active ion transport on the particle surface. At this time, the kinetic properties of the carbonaceous material deteriorate, which also leads to less than ideal cycle performance and rate performance of the secondary battery.

[0062] In some embodiments, optionally, 3 ≤ A / B ≤ 10, 4 ≤ A / B ≤ 10, 5 ≤ A / B ≤ 9.5, and 6 ≤ A / B ≤ 9.2. This helps to further improve the cycle performance and rate performance of the secondary battery.

[0063] In some embodiments, optionally, 5wt%≤A≤18wt%, 5wt%≤A≤16wt%, 6wt%≤A≤16wt%, 7wt%≤A≤16wt%, 8wt%≤A≤16wt%, 9wt%≤A≤16wt%, and 10wt%≤A≤16wt%. This helps to further improve the cycle performance and rate performance of the secondary battery.

[0064] The inventors of this application also discovered during their research that the oxygen (O) content of the entire carbonaceous material sample also affects the cycle performance and rate performance of the secondary battery. Since O atoms cannot reversibly intercalate or deintercalate with active ions after binding, a higher O content in the entire carbonaceous material sample leads to higher irreversible consumption of active ions, thereby reducing the energy density of the secondary battery and affecting its cycle performance. In some embodiments, 0 < B ≤ 6 wt%, 1.5 wt% ≤ B ≤ 6 wt%, 1.5 wt% ≤ B ≤ 5 wt%, 1.5 wt% ≤ B ≤ 4 wt%, and 1.5 wt% ≤ B ≤ 3 wt%. This helps to further improve the cycle performance and rate performance of the secondary battery.

[0065] In some embodiments, the carbonaceous material satisfies 6 ≤ A / B ≤ 9.2, 10 wt% ≤ A ≤ 16 wt%, and 1.5 wt% ≤ B ≤ 3 wt%. The inventors of this application also discovered during their research that, in this case, the secondary battery can simultaneously possess better cycle performance and rate performance.

[0066] In some embodiments, the specific surface area of ​​the carbonaceous material is ≤10m². 2 / g, can be selected as 0.1m 2 / g-10m2 / g, 1m 2 / g-10m 2 / g, 2m 2 / g-10m 2 / g, 3m 2 / g-10m 2 / g, 4m 2 / g-10m 2 / g, 4m 2 / g-9m 2 / g, 4m 2 / g-8.5m 2 / g, 4m 2 / g-8.2m 2 / g, 4m 2 / g-8m 2 / g, 4m 2 / g-7.8m 2 / g, 4m 2 / g-7.6m 2 / g, 4.5m 2 / g-7.6m 2 / g, 5m 2 / g-7.6m 2 / g. The carbonaceous material provided in this application has a low specific surface area, which helps to reduce the surface activity of the carbonaceous material, reduce the formation of the SEI film, and thus reduce the irreversible consumption of active ions. This allows the carbonaceous material to simultaneously possess higher specific capacity and initial coulombic efficiency, while also enabling the secondary battery to have better cycle performance and rate performance. When the specific surface area of ​​the carbonaceous material is high, more binder needs to be added during the electrode preparation process to bond the particles. However, binders are generally insulating materials, which can cause an increase in battery internal resistance and a decrease in ionic conductivity and electronic conductivity, thereby leading to a deterioration in the cycle performance and rate performance of the secondary battery.

[0067] In this application, the specific surface area of ​​carbonaceous materials has a meaning known in the art and can be measured using instruments and methods known in the art. For example, it can be measured using the nitrogen adsorption specific surface area analysis method according to GB / T 19587-2017 and calculated using the BET (Brunauer Emmett Teller) method. The nitrogen adsorption specific surface area analysis can be performed using the ASAP 3020 surface area and pore size analyzer from Micromeritics, Inc., USA.

[0068] In some embodiments, the carbonaceous material includes a plurality of nanoporous structures.

[0069] In some embodiments, the carbonaceous material may have a regular or irregular morphology; for example, the morphology of the carbonaceous material may be an irregular polygonal shape.

[0070] In some embodiments, the carbonaceous material contains a low content of impurity elements, primarily Na. In some embodiments, the Na content is ≤0.011 wt%, optionally ≤0.005 wt%. In some embodiments, in the Raman spectrum of the carbonaceous material, I d / I g The value is 0.90-1.25, I d This indicates that the Raman displacement is within 1350±50cm. -1 The d-peak intensity within the range, I g This indicates that the Raman displacement is within 1580±50cm. -1 The intensity of the g peak within the range. For example, I d / I g It can be a range consisting of any values ​​of 0.90, 0.95, 1.00, 1.05, 1.10, 1.15, 1.20, 1.25, or higher. Optionally, I d / I g It can be 0.95-1.10.

[0071] The Raman spectra of carbonaceous materials can be measured using a Raman spectrometer. During the test, the d-peak and g-peak intensities at 100 points are acquired, and the Ig at these 100 points is calculated. d / I g Remove the largest and smallest 30 I's. d / I g 40 I's remaining d / I g The average value is used as the I of carbonaceous materials d / I g The testing instrument can be a Horiba LabRAM HR800 Raman spectrometer. The testing conditions can be: excitation wavelength 532 nm, grating 600 lines, objective lens 50x, integration time 10 s, cumulative count 3, area scan.

[0072] The d-peak originates from lattice defects in carbon atoms, while the g-peak originates from in-plane vibrations of sp2 carbon atoms. In carbonaceous materials, the intensity of the d-peak is related to the number of defects in the structure, and the intensity of the g-peak is related to the number of graphite crystallites. Therefore, I d / I g It can characterize the degree of order in the structure of carbonaceous materials. d / I gThe smaller the value, the higher the orderliness of the carbonaceous material structure, the higher the integrity of the carbon plane, and the higher the initial coulombic efficiency of the carbonaceous material, but the specific capacity decreases and the rate performance deteriorates. The carbonaceous material of this application satisfies I... d / I g The value is 0.90-1.25. At this value, the orderliness of the carbonaceous material structure is moderate, resulting in higher specific capacity and higher first coulombic efficiency, as well as excellent rate performance.

[0073] In some embodiments, the interlayer spacing of the (002) crystal plane of the carbonaceous material is ≥0.37nm, and can be selected as 0.37nm-0.42nm.

[0074] In some embodiments, in the X-ray diffraction spectrum of the carbonaceous material, the 2θ value corresponding to the (002) crystal plane peak is between 22° and 24°.

[0075] In this application, the interlayer spacing of the (002) crystal plane of the carbonaceous material can be measured using an X-ray diffractometer, referring to JIS K 0131-1996 and JB / T4220-2011. The measuring instrument can be a Bruker D8 Discover X-ray diffractometer.

[0076] In some embodiments, the volumetric particle size Dv50 of the carbonaceous material is 3μm-15μm, and can be selected as 4μm-6μm.

[0077] In some embodiments, the volumetric particle size Dv90 of the carbonaceous material is 8μm-30μm, and can be selected as 9μm-12μm.

[0078] In some embodiments, the carbonaceous material simultaneously satisfies a volumetric particle size Dv50 of 3 μm-15 μm and a volumetric particle size Dv90 of 8 μm-30 μm. Optionally, the carbonaceous material simultaneously satisfies a volumetric particle size Dv50 of 4 μm-6 μm and a volumetric particle size Dv90 of 9 μm-12 μm.

[0079] When the volumetric particle size Dv50 and / or Dv90 of carbonaceous materials are within a suitable range, it is beneficial to improve the active ion and electron transport performance, thereby further improving the cycle performance and rate performance of secondary batteries.

[0080] In this application, the volumetric particle sizes Dv50 and Dv90 of carbonaceous materials have meanings known in the art, representing the particle size corresponding to a cumulative volumetric distribution percentage of 50% and 90%, respectively, and can be determined using instruments and methods known in the art. For example, they can be conveniently determined using a laser particle size analyzer, referring to GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method. The testing instrument can be a Mastersizer 2000E laser particle size analyzer from Malvern Instruments Ltd., UK.

[0081] In some embodiments, the compacted density of the carbonaceous material powder under a force of 50,000 N is 0.92 g / cm³. 3 -1.05g / cm 3 The option is 0.95g / cm³. 3 -1.02g / cm 3 When the compaction density of carbonaceous material powder is within a suitable range, the compaction density of the negative electrode sheet can be increased, thereby improving the energy density of the secondary battery.

[0082] In this application, the compacted density of carbonaceous material powder has a meaning known in the art and can be determined using instruments and methods known in the art. For example, it can be determined using an electronic pressure testing machine (e.g., a UTM7305 model) in accordance with standard GB / T24533-2009. An exemplary test method is as follows: Weigh 1g of carbonaceous material powder and add it to a container with a bottom area of ​​1.327cm². 2 In the mold, the pressure is increased to 5000 kg (equivalent to 50000 N), held for 30 seconds, then depressurized and held for 10 seconds. The compaction density of the carbonaceous material under a force of 50000 N is then recorded and calculated.

[0083] In some embodiments, the tap density of the carbonaceous material is 0.80 g / cm³. 3 -0.95g / cm 3 0.85g / cm³ is an optional value. 3 -0.90g / cm 3 When the tap density of carbonaceous materials is within a suitable range, the tap density of the negative electrode sheet can be increased, thereby improving the energy density of the secondary battery.

[0084] In this application, the tap density of carbonaceous materials has a meaning known in the art and can be determined using instruments and methods known in the art. For example, it can be determined using a powder tap density tester according to GB / T 5162-2006. The testing instrument can be the Dandong Baite BT-301.

[0085] Preparation methods of carbonaceous materials The second aspect of this application provides a method for preparing a carbonaceous material, which is capable of preparing the carbonaceous material of any embodiment of the first aspect of this application.

[0086] The preparation method includes the following steps: S10, providing raw materials, the raw materials including hard carbon materials; S20, grinding the raw materials with grinding media and oxidizing solution in a grinding mill; S30, washing and drying the product obtained from grinding to obtain carbonaceous materials, wherein the O element content of the carbonaceous materials tested by X-ray photoelectron spectroscopy is denoted as A, and the O element content tested by elemental analysis is denoted as B, and the carbonaceous materials satisfy A / B≥3 and 5wt%≤A≤20wt%.

[0087] This application utilizes a wet grinding process to introduce a suitable amount of oxygen-containing functional groups onto the surface of a hard carbon material, thereby obtaining a carbonaceous material that satisfies A / B ≥ 3 and 5wt% ≤ A ≤ 20wt%. In this application, the oxygen-containing functional groups may include one or more of phenolic, etheric, quinone, carbonyl, acid anhydride, ester, hydroxyl, and carboxyl groups. The inventors of this application discovered during their research that during charging (i.e., before the formation of the SEI film), negative charges can accumulate on the oxygen-containing functional groups on the surface of the carbonaceous material, thereby inducing the rapid decomposition of organic solvents such as esters or ethers in the electrolyte, and thus increasing the content of organic components in the SEI film.

[0088] The inventors of this application also discovered during their research that these organic components have numerous advantages over inorganic components: First, the organic components in the SEI film have higher flexibility, which can improve the SEI film's resistance to deformation and maintain its stability during long-term cycling, thereby reducing the consumption of active ions during cycling and further improving the cycle performance of the secondary battery; Second, the organic components in the SEI film can increase the ionic conductivity on the negative electrode side, which is beneficial to further improving the rate performance of the secondary battery, while also preventing the reduction and precipitation of active ions on the negative electrode side during cycling, thus further improving the cycle performance of the secondary battery; Third, the O atoms on the surface of the carbonaceous material can also participate in the formation of the SEI film, which is beneficial to improving the adhesion of the SEI film to the surface of the carbonaceous material particles, and is beneficial to the high stability of the SEI film during long-term cycling, thereby reducing the consumption of active ions during cycling and further improving the cycle performance of the secondary battery.

[0089] Therefore, the carbonaceous material obtained by the preparation method of this application exhibits excellent cycling performance and rate performance. The preparation method of the carbonaceous material provided in this application is simple and suitable for commercial production.

[0090] Currently, the cycle performance and rate performance of commercially available hard carbon materials are not ideal. The preparation method provided in this application can significantly optimize the cycle performance and rate performance of the raw materials (i.e., hard carbon materials). Moreover, the preparation method provided in this application is universal, as the raw materials can be obtained commercially or prepared according to the method provided in this application.

[0091] In some embodiments, the raw material is prepared by the following method: heating a carbon source to 1000℃-1600℃ at a rate of ≤10℃ / min under a protective gas atmosphere, holding at that temperature for 1h-24h, and then crushing to obtain the raw material. The carbon source may include one or more of polymers, resins, and biomass materials, and the protective gas may include nitrogen, argon, or a combination thereof.

[0092] In some embodiments, in S10, the volumetric particle size Dv50 of the raw material can be 3μm-15μm, optionally 4μm-6μm. In some embodiments, in S10, the volumetric particle size Dv90 of the raw material can be 8μm-30μm, optionally 9μm-12μm. In some embodiments, in S10, the volumetric particle size Dv50 of the raw material is 3μm-15μm and the volumetric particle size Dv90 is 8μm-30μm; optionally, the volumetric particle size Dv50 of the raw material is 4μm-6μm and the volumetric particle size Dv90 is 9μm-12μm. By adjusting the volumetric particle size Dv50 and / or Dv90 of the raw material to a suitable range, it is beneficial to improve the active ion and electron transport performance of the obtained carbonaceous material, thereby further improving the cycle performance and rate performance of the secondary battery.

[0093] In some embodiments, in S20, the dry weight ratio of the raw material to the mass of the grinding media is ≤1, for example, it can be ≤0.9, ≤0.8, ≤0.7, ≤0.6, or ≤0.5.

[0094] During grinding, the grinding media exerts a significant shear force on the raw material particles. Under this shear force, the covalent bonds on the surface of the particles are easily broken. These broken bond sites are then prone to react with oxidizing solutions, introducing oxygen-containing functional groups. When the dry weight of the raw material is too high compared to the mass ratio of the grinding media, there will be too few grinding media applying the shear force. Consequently, only a few covalent bonds on the surface of the raw material particles will be broken, introducing oxygen-containing functional groups. This results in fewer oxygen-containing functional groups introduced onto the surface of the carbonaceous material particles, leading to poor cycle performance and rate performance of the secondary battery. In this case, the carbonaceous material exhibits a low oxygen content as measured by X-ray photoelectron spectroscopy.

[0095] The design of the dry weight ratio of raw materials to the mass of grinding media also needs to consider the actual volume of the grinder and the wet grinding effect. Furthermore, the dry weight ratio of raw materials to the mass of grinding media should not be too small. When the volume of material in the grinder is the same, a small dry weight ratio will result in insufficient raw material to be processed per grinding cycle, affecting production efficiency. Conversely, a small dry weight ratio will lead to an excessively large mass of grinding media, resulting in too much material in the grinder and affecting the wet grinding effect. Additionally, it may lead to a significant increase in the specific surface area of ​​the obtained carbonaceous material and / or the introduction of more oxygen-containing functional groups on the surface of the carbonaceous material particles, resulting in a higher O content as measured by X-ray photoelectron spectroscopy, which in turn worsens the optimization effect on the cycle performance and rate performance of the secondary battery.

[0096] In some embodiments, in S20, the dry weight ratio of the raw material to the mass of the grinding media can be 0.2-1, 0.3-0.9, 0.4-0.8, or 0.4-0.7. This improves production efficiency and ensures the obtained carbonaceous material has a suitable content of oxygen-containing functional groups on its surface. Furthermore, the carbonaceous material significantly enhances the cycle performance and rate performance of the secondary battery.

[0097] In some embodiments, in S20, the mass ratio of the dry weight of the raw material to the mass of the oxidizing solution is ≤0.6, for example, it can be ≤0.55, ≤0.5, ≤0.45, ≤0.4, ≤0.35, ≤0.3, ≤0.25, or ≤0.2.

[0098] When the covalent bonds on the surface of raw material particles are broken by the grinding media, these broken bond sites can react with the oxidizing solution and introduce oxygen-containing functional groups. When the dry weight to oxidizing solution mass ratio is too high, there is too little oxidizing solution, preventing the material in the grinder from forming a slurry. This results in uneven contact between the oxidizing solution and the raw material particles, with some particles failing to reach the oxidizing solution. Consequently, the distribution area of ​​introduced oxygen-containing functional groups on the surface of the resulting carbonaceous material particles is limited. The areas on the surface of these particles lacking oxygen-containing functional groups exhibit poor cycle performance and rate performance, leading to poor overall cycle and rate performance of the secondary battery. Conversely, when the dry weight to oxidizing solution mass ratio is also too high, there is too little oxidizing solution, resulting in overly dry and essentially flocculent material in the grinder. This leads to poor wet grinding, resulting in a lower amount of oxygen-containing functional groups introduced onto the surface of the carbonaceous material particles, thus diminishing the optimization effect on the cycle and rate performance of the secondary battery. At this point, carbonaceous materials exhibit a low O content as measured by X-ray photoelectron spectroscopy.

[0099] The design of the dry weight ratio of raw materials to oxidizing solution also needs to consider the actual volume of the grinder and the wet grinding effect. Furthermore, the dry weight ratio of raw materials to oxidizing solution should not be too small. When the volume of material in the grinder is the same, a small dry weight ratio will result in insufficient raw material to be processed per grinding cycle, affecting production efficiency. Conversely, a small dry weight ratio will lead to an excessively large oxidizing solution, resulting in too much material in the grinder, which will affect the wet grinding effect. Additionally, it may introduce more oxygen-containing functional groups onto the surface of the obtained carbonaceous material particles, leading to a higher O content as measured by X-ray photoelectron spectroscopy, which in turn worsens the optimization effect on the cycle performance and rate performance of the secondary battery.

[0100] In some embodiments, in S20, the mass ratio of the dry weight of the raw material to the oxidizing solution can be 0.1-0.6, 0.1-0.5, 0.1-0.5, or 0.1-0.4. This improves production efficiency and ensures that the surface of the obtained carbonaceous material has a suitable content of oxygen-containing functional groups. Furthermore, the carbonaceous material can significantly enhance the cycle performance and rate performance of the secondary battery.

[0101] In some embodiments, in S20, the concentration of the oxidizing solution is ≥0.1 mol / L.

[0102] When the concentration of the oxidizing solution is too low, although many covalent bonds on the surface of the raw material particles are broken during grinding, due to the low solute content and weak oxidizing ability, only a small number of broken covalent bonds eventually transform into oxygen-containing functional groups. The remaining broken bond positions are retained and will subsequently serve as sites for capturing active ions. This leads to the obstruction of the transport continuity of active ions on the surface of the obtained carbonaceous material particles, resulting in poor kinetic performance of the carbonaceous material, which in turn deteriorates cycling performance and rate performance. In this case, the carbonaceous material exhibits a low O content as measured by X-ray photoelectron spectroscopy.

[0103] Furthermore, the concentration of the oxidizing solution should not be too high. On the one hand, it will increase safety risks, and on the other hand, it may introduce more oxygen-containing functional groups on the surface of the obtained carbonaceous material particles, resulting in the carbonaceous material exhibiting a high O content as measured by X-ray photoelectron spectroscopy, which in turn leads to a deterioration in the optimization effect on the cycle performance and rate performance of the secondary battery.

[0104] In some embodiments, the concentration of the oxidizing solution is 0.1 mol / L-10 mol / L, 0.2 mol / L-8 mol / L, 0.3 mol / L-5 mol / L, 0.4 mol / L-2.5 mol / L, or 0.5 mol / L-1.5 mol / L. This improves production efficiency and ensures safe production, while also ensuring the obtained carbonaceous material has a suitable content of oxygen-containing functional groups on its surface. Furthermore, the carbonaceous material significantly enhances the cycle performance and rate performance of the secondary battery.

[0105] In some embodiments, during S20, the grinding time is 1-24 hours, for example, it can be a range of 2 hours, 4 hours, 6 hours, 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, 24 hours, or any combination thereof. Optionally, the grinding time is 2-20 hours, 4-16 hours, or 6-12 hours. This allows the obtained carbonaceous material surface to have a suitable content of oxygen-containing functional groups, and the carbonaceous material can also significantly improve the cycle performance and rate performance of the secondary battery.

[0106] During grinding, the grinding media exerts a significant shear force on the raw material particles. If the grinding time is too long, this shear force persists for an extended period, potentially causing particle breakage. This leads to a substantial increase in the specific surface area of ​​the resulting carbonaceous material. During electrode fabrication, a large amount of binder is required to bond the particles. However, binders are typically insulating materials, which can increase the battery's internal resistance and decrease ionic and electronic conductivity, ultimately degrading the cycle performance and rate capability of the secondary battery. In this case, the carbonaceous material exhibits a high oxygen (O) content as measured by X-ray photoelectron spectroscopy.

[0107] During grinding, the covalent bonds on the surface of the raw material particles are easily broken under shear force. Then, the broken bond sites are prone to react with oxidizing solutions, thereby introducing oxygen-containing functional groups. When the grinding time is too short, fewer oxygen-containing functional groups are introduced on the surface of the carbonaceous material particles, which will also lead to poor cycle performance and rate performance of the secondary battery. In this case, the carbonaceous material shows a low O content as measured by X-ray photoelectron spectroscopy.

[0108] In this application, an oxidizing solution refers to a solution obtained by uniformly mixing an oxidizing solute with a solvent that has oxidizing ability and can introduce oxygen-containing functional groups onto the particle surface. In some embodiments, in S20, the solute in the oxidizing solution includes one or more selected from nitric acid, sulfuric acid, and perchloric acid, and the solvent includes water.

[0109] Therefore, on the one hand, it can ensure that the surface of the obtained carbonaceous material has an appropriate content of oxygen-containing functional groups, and on the other hand, it can avoid the introduction of other impurity elements, thereby reducing the irreversible consumption of active ions.

[0110] In some embodiments, in S20, the grinding speed is 100rpm-1200rpm.

[0111] In some embodiments, in S20, the grinding instrument includes a ball mill.

[0112] In some embodiments, in S20, the grinding media includes grinding balls, such as zirconium oxide balls. Optionally, the diameter of the grinding balls may be 2mm-16mm. This helps to improve the grinding effect and significantly improve the cycle performance and rate performance of the secondary battery.

[0113] In some embodiments, during S20, the volume percentage of all materials (including grinding media, raw materials, and oxidizing solution) in the grinder can be 1 / 5 to 3 / 4, based on the volume of the grinder (e.g., the volume of the grinding jar in a ball mill). This can improve both production efficiency and the wet grinding effect.

[0114] In some embodiments, in S30, the washing may be a water wash. The water wash may be performed once or more until the pH of the filtrate is 7 ± 0.5.

[0115] In some embodiments, in S30, the drying may be vacuum drying. Optionally, the drying temperature is 60°C-120°C. Optionally, the drying time is 1 hour-24 hours.

[0116] In some embodiments, the preparation method includes the following steps: S10, providing raw materials, the raw materials including hard carbon materials; S20, grinding the raw materials with a grinding media and an oxidizing solution in a grinder, wherein the dry weight ratio of the raw materials to the grinding media is ≤1, optionally 0.2-1, the dry weight ratio of the raw materials to the oxidizing solution is ≤0.6, optionally 0.1-0.6, the concentration of the oxidizing solution is ≥0.1 mol / L, optionally 0.1 mol / L-10 mol / L, and the grinding time is 1 h-24 h, optionally 4 h-16 h; S30, washing and drying the product obtained from grinding to obtain a carbonaceous material. At this point, the carbonaceous material obtained by the preparation method of this application can significantly improve the cycle performance and rate performance of the secondary battery.

[0117] Secondary batteries The third aspect of this application provides a secondary battery.

[0118] The secondary battery mentioned in the embodiments or implementations of this application refers to a single physical module comprising one or more battery cells to provide higher voltage and capacity. For example, the secondary battery mentioned in this application may include battery cells, battery modules, or battery packs. A battery cell is the smallest unit constituting a secondary battery, capable of charging and discharging independently. This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. Figure 1 The example shown is a square-structured battery cell 5.

[0119] 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. The material of the flexible package can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0120] 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.

[0121] 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.

[0122] 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.

[0123] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0124] 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 5 As shown, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3. The upper body 2 covers the lower body 3, forming a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0125] [Negative electrode plate] In some embodiments, the negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector. For example, the negative current collector has two surfaces opposite each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative current collector.

[0126] In some embodiments, the negative electrode film layer comprises a carbonaceous material according to the first aspect of this application or a carbonaceous material prepared by the method described in the second aspect of this application. This can significantly improve the cycle performance and rate performance of the secondary battery.

[0127] In some embodiments, the negative electrode film layer may further include other negative electrode active materials besides the carbonaceous materials described above. In some embodiments, the other negative electrode active materials include, but are not limited to, one or more of natural graphite, artificial graphite, soft carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based materials may include one or more of elemental silicon, silicon oxide, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based materials may include one or more of elemental tin, tin oxide, and tin alloys.

[0128] In some embodiments, the negative electrode film layer may optionally include a negative electrode conductive agent. This application does not impose any particular limitation on the type of negative electrode conductive agent. As an example, the negative electrode conductive agent may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0129] In some embodiments, the negative electrode film layer may optionally include a negative electrode binder. This application does not impose any particular limitation on the type of negative electrode binder. As an example, the negative electrode binder may include one or more of the following: styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0130] In some embodiments, the negative electrode film may optionally include other additives. As an example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc.

[0131] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, copper foil may be used. The composite current collector may include a polymeric material substrate and a metal material layer formed on at least one surface of the polymeric material substrate. As an example, the metal material may include one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymeric material substrate may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0132] The negative electrode film layer is typically formed by coating a negative electrode slurry onto a negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry is typically formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional additives in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to these.

[0133] The negative electrode sheet does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode sheet of this application further includes a conductive undercoat layer (e.g., composed of a conductive agent and an adhesive) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector; in some embodiments, the negative electrode sheet of this application further includes a protective layer covering the surface of the negative electrode film layer.

[0134] [Positive electrode plate] In some embodiments, the positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector. For example, the positive current collector has two surfaces opposite each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0135] The positive electrode current collector can be a metal foil or a composite current collector. As an example of a metal foil, aluminum foil can be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0136] The positive electrode film typically comprises a positive electrode active material, an optional binder, and an optional conductive agent. The positive electrode film is typically formed by coating a positive electrode slurry onto the positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is typically formed by dispersing the positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent and stirring until homogeneous. The solvent may be N-methylpyrrolidone (NMP), but is not limited to this. As an example, the binder used for the positive electrode film may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins. As an example, the conductive agent used for the positive electrode film includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0137] The positive electrode active material may be a positive electrode active material known in the art for use in secondary batteries.

[0138] When the secondary battery of this application is a lithium-ion battery, the positive electrode active material may include, but is not limited to, one or more of lithium transition metal oxides, lithium phosphates, and their respective modified compounds. Examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxides, lithium nickel oxides, lithium manganese oxides, lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides, lithium nickel cobalt aluminum oxides, and their respective modified compounds. Examples of lithium phosphates may include, but are not limited to, lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, lithium manganese iron phosphate and carbon composites, and their respective modified compounds.

[0139] In some embodiments, to further improve the energy density of secondary batteries, the positive electrode active material for lithium-ion batteries may include materials with the general formula Li. a Ni bCo c 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.

[0140] 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.

[0141] 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.

[0142] 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. In general formula X p M' q (PO4) r O x Y 3-x In the given condition, 0 < p ≤ 4, 0 < q ≤ 2, 1 ≤ r ≤ 3, 0 ≤ x ≤ 2, and X includes elements selected from H. + Li + Na + K + and NH4 + One or more of the following, M' is a transition metal cation, which may be selected from one or more of V, Ti, Mn, Fe, Co, Ni, Cu and Zn, and Y is a halide anion, which may be selected from one or more of F, Cl and Br.

[0143] In this application, the modified compounds of the above-mentioned positive electrode active materials may be those that have undergone doping modification and / or surface coating modification of the positive electrode active materials.

[0144] [Electrolytes] This application does not impose any particular limitation on the type of electrolyte, which can be selected according to actual needs. For example, the electrolyte can be selected from at least one of solid electrolytes and liquid electrolytes (i.e., electrolyte solutions).

[0145] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0146] The type of electrolyte salt is not specifically limited and can be selected according to actual needs.

[0147] When the secondary battery of this application is a lithium-ion battery, as an example, the electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0148] When the secondary battery of this application is a sodium-ion battery, the electrolyte salt may include one or more of the following: sodium hexafluorophosphate (NaPF6), sodium tetrafluoroborate (NaBF4), sodium perchlorate (NaClO4), sodium hexafluoroarsenate (NaAsF6), sodium bis(fluorosulfonyl)imide (NaFSI), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), sodium trifluoromethanesulfonate (NaTFS), sodium difluorooxalate borate (NaDFOB), sodium dioxalate borate (NaBOB), sodium difluorophosphate (NaPO2F2), sodium difluorodioxalate phosphate (NaDFOP), and sodium tetrafluorooxalate phosphate (NaTFOP).

[0149] The type of solvent is not specifically limited and can be selected according to actual needs. In some embodiments, as an example, the solvent may include one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl ethylene 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).

[0150] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature power performance.

[0151] [Isolation membrane] Secondary batteries using electrolytes, and some secondary batteries using solid electrolytes, also include a separator. The separator is disposed between the positive electrode and the negative electrode, serving as a barrier. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0152] In some embodiments, the material of the separator may include one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer may be the same or different.

[0153] [Preparation Method] The method for preparing the secondary battery described in this application is well known. In some embodiments, a positive electrode, a separator, a negative electrode, and an electrolyte can be assembled to form a secondary battery. As an example, the positive electrode, separator, and negative electrode can be formed into an electrode assembly through a winding process and / or a stacking process. The electrode assembly is placed in an outer packaging, dried, and then injected with an electrolyte. After vacuum sealing, settling, formation, and shaping processes, a battery cell is obtained. Multiple battery cells can be further connected in series, parallel, or a combination thereof to form a battery module. Multiple battery modules can also be connected in series, parallel, or a combination thereof to form a battery pack. In some embodiments, multiple battery cells can also be directly assembled into a battery pack.

[0154] Electrical appliances A fourth aspect of this application provides an electrical device, which includes the secondary battery described in this application. The secondary battery can be used as a power source for the electrical device or as an energy storage unit. The electrical device can be, but is not limited to, mobile devices (e.g., mobile phones, tablets, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0155] The electrical device can select the specific type of secondary battery according to its usage requirements, such as a battery cell, battery module, or battery pack.

[0156] Figure 6 This is a schematic diagram illustrating an example of an electrical device. This device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the device's requirements for high power and high energy density, a battery pack or battery module can be used as the power source.

[0157] Another example of an electrical device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0158] Example The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0159] Example 1 Using phenolic resin as the carbon source, the temperature was raised to 1400℃ at a rate of 5℃ / min under a nitrogen atmosphere and held for 12 hours. The resulting material was then ball-milled to obtain a hard carbon material with a Dv50 of 6±0.5μm. The hard carbon material, along with zirconium oxide balls and an oxidizing solution, was placed in the ball mill jar of a planetary ball mill and ball-milled at 600 rpm for 10 hours. After washing and drying, the carbonaceous material was obtained. The dry weight ratio of the hard carbon material to the grinding media was 0.6, and the dry weight ratio of the hard carbon material to the oxidizing solution was 0.2. The concentration of the oxidizing solution was 0.1 mol / L, the solute was perchloric acid, and the solvent was deionized water.

[0160] After vacuum drying the carbonaceous material at 120℃ for 12 hours, it was sealed and stored in an aluminum-plastic bag. The oxygen content was then measured using an X-ray photoelectron spectrometer (XPS) and recorded as A, and the oxygen content was measured using an elemental analyzer and recorded as B. The testing instruments used were the Thermo Fisher Scientific Nexsa / EscaLab 250Xi XPS and the Thermo Fisher Scientific Flash 2000 / Flash Smart elemental analyzer.

[0161] The BET specific surface area of ​​carbonaceous materials was determined using the nitrogen adsorption specific surface area analysis method, in accordance with GB / T 19587-2017. The testing instrument can be the ASAP 3020 surface area and pore size analyzer from Micromeritics, USA.

[0162] Examples 2-16 and Comparative Examples 3-7 The preparation method of carbonaceous materials is similar to that in Example 1, except that the preparation process parameters of carbonaceous materials are adjusted, as detailed in Table 1.

[0163] Comparative Example 1 Using phenolic resin as a carbon source, the temperature was raised to 1400℃ at a rate of 5℃ / min under a nitrogen atmosphere and held for 12h. The material was then crushed by ball milling to obtain a hard carbon material with a Dv50 of 6±0.5μm, which was used as a carbonaceous material.

[0164] Comparative Example 2 Using phenolic resin as a carbon source, the temperature was increased to 1400℃ at a rate of 5℃ / min under a nitrogen atmosphere and held for 12 h. The resulting material was then ball-milled to obtain a hard carbon material with a Dv50 of 6 ± 0.5 μm. The hard carbon material was then immersed in a 1 mol / L perchloric acid aqueous solution for 48 h, followed by washing and drying to obtain the carbonaceous material. The mass ratio of the dry weight of the hard carbon material to the perchloric acid aqueous solution was 0.1.

[0165] Preparation of secondary batteries The aforementioned carbonaceous material, conductive carbon black (Super P), binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose were thoroughly mixed in an appropriate amount of deionized water at a weight ratio of 96:1:1:2 to form a negative electrode slurry. The negative electrode slurry was coated onto both surfaces of the negative electrode current collector copper foil, and after drying and cold pressing, a negative electrode sheet was obtained.

[0166] NaNi, the positive electrode active material 1 / 3 Co 1 / 3 Mn 1 / 3 O2 is mixed with conductive carbon black and polyvinylidene fluoride in a weight ratio of 96:2.5:1.5, and an appropriate amount of NMP solvent is added. The mixture is stirred until homogeneous to obtain a positive electrode slurry. The positive electrode slurry is coated onto both surfaces of the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet is obtained.

[0167] Ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC) were mixed uniformly in a volume ratio of 1:1:1 to obtain an organic solvent. Then, NaPF6 was added to the organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0168] A 12μm thick polypropylene film is used as a separator. It is placed in sequence with the positive and negative electrode sheets prepared above, so that the separator is in the middle of the positive and negative electrode sheets to play a role in isolation. Then, the electrode assembly is wound to obtain the electrode assembly. The electrode assembly is placed in the outer packaging, dried, and then injected with the electrolyte prepared above. After vacuum sealing, standing, formation, capacity testing and other processes, a secondary battery is obtained.

[0169] Performance testing (1) Cyclic performance test of secondary battery at 25℃ At 25°C, the secondary battery was charged at a constant current of 1C to a voltage of 4.0V, then charged at a constant voltage to a current of 0.05C. After resting for 5 minutes, the secondary battery was discharged at a constant current of 1C to a voltage of 1.5V. This constitutes one charge-discharge cycle, and the discharge capacity of this cycle is the discharge capacity of the secondary battery after the first cycle. The aforementioned charge-discharge cycle was repeated until the discharge capacity decreased to 80% of the discharge capacity after the first cycle, and the number of cycles completed by the secondary battery at this point was recorded.

[0170] (2) Cyclic performance test of secondary battery at 45℃ At 45°C, the secondary battery is charged at a constant current of 1C to a voltage of 4.0V, then charged at a constant voltage to a current of 0.05C. After resting for 5 minutes, the secondary battery is discharged at a constant current of 1C to a voltage of 1.5V. This constitutes one charge-discharge cycle, and the discharge capacity recorded is the discharge capacity of the secondary battery after the first cycle. The aforementioned charge-discharge cycle is repeated until the discharge capacity decreases to 80% of the discharge capacity after the first cycle, and the number of cycles completed by the secondary battery at this point is recorded.

[0171] (3) Rate performance test of secondary battery at 25℃ At 25°C, the secondary battery is charged at a constant current of 0.33C to a voltage of 4.0V, then charged at a constant voltage to a current of 0.05C. After standing for 5 minutes, the secondary battery is discharged at a constant current of 0.33C to a voltage of 1.5V. The discharge capacity at this point is the discharge capacity of the secondary battery at 0.33C.

[0172] At 25°C, the secondary battery is charged at a constant current of 1C to a voltage of 4.0V, then charged at a constant voltage to a current of 0.05C. After standing for 5 minutes, the secondary battery is discharged at a constant current of 1C to a voltage of 1.5V. The discharge capacity at this time is the discharge capacity of the secondary battery at 1C.

[0173] The rate performance of a secondary battery is characterized by the ratio of its discharge capacity at 1C to its discharge capacity at 0.33C.

[0174] Based on the test results in Table 1, it can be seen that when the O content A measured by X-ray photoelectron spectroscopy and the O content B measured by elemental analysis satisfy A / B≥3 and 5wt%≤A≤20wt% respectively, the cycle performance and rate performance of the secondary battery can be significantly optimized.

[0175] The carbonaceous material provided in this application is obtained by wet milling the hard carbon material provided in Comparative Example 1, thereby introducing an appropriate amount of oxygen-containing functional groups onto the surface of the hard carbon material provided in Comparative Example 1. During the research process, the inventors of this application discovered that during charging (i.e., before the formation of the SEI film), negative charges can accumulate on the oxygen-containing functional groups on the surface of the carbonaceous material, thereby inducing the rapid decomposition of ester organic solvents in the electrolyte, and thus increasing the content of organic components in the SEI film. The organic components in the SEI film have higher flexibility, which can improve the deformation resistance of the SEI film and maintain its stability during long-term cycling, thereby reducing the consumption of active ions during cycling; the organic components in the SEI film can improve the ionic conductivity on the negative electrode side, while also preventing the reduction and precipitation of active ions on the negative electrode side during cycling; the O atoms on the surface of the carbonaceous material can also participate in the formation of the SEI film, which is beneficial to improving the adhesion of the SEI film to the surface of the carbonaceous material particles, and is conducive to the high stability of the SEI film during long-term cycling, thereby reducing the consumption of active ions during cycling. Therefore, the secondary battery using the carbonaceous material provided in this application can have significantly improved cycle performance and rate performance. The test results from Examples 1-16 also show that when the carbonaceous material further satisfies 6≤A / B≤9.2, 10wt%≤A≤16wt%, and 1.5wt%≤B≤3wt%, the optimization effect on the cycle performance and rate performance of the secondary battery is even better.

[0176] Comparative Example 2 also introduced oxygen-containing functional groups onto the surface of the hard carbon material provided in Comparative Example 1 by immersion in an oxidizing solution. However, the amount of oxygen-containing functional groups introduced was small, resulting in an insignificant improvement in the cycle performance and rate performance of the secondary battery.

[0177] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

[0178] Table 1

Claims

1. A method for preparing a carbonaceous material, comprising the following steps: S10, providing raw materials, the raw materials comprising hard carbon materials; S20, grinding the raw materials with a grinding media and an oxidizing solution in a grinding mill, wherein the dry weight ratio of the raw materials to the grinding media is ≤0.6, and the dry weight ratio of the raw materials to the oxidizing solution is ≤0.4; S30, washing and drying the product obtained from the grinding to obtain the carbonaceous material, wherein... The carbonaceous material has an O content measured by X-ray photoelectron spectroscopy, denoted as A, and an O content measured by elemental analysis, denoted as B. The carbonaceous material satisfies A / B≥3.

2. The method according to claim 1, wherein, 5wt%≤A≤20wt%; In S20, The dry weight ratio of the raw material to the mass of the grinding media is 0.2-0.6; and / or, The dry weight ratio of the raw material to the oxidizing solution is 0.1-0.4; and / or, The concentration of the oxidizing solution is ≥0.1 mol / L; and / or, The grinding time is 1 hour to 24 hours.

3. The method according to any one of claims 1-2, wherein, In S20, the concentration of the oxidizing solution is 0.1 mol / L to 10 mol / L; and / or, The grinding time is 4h-16h.

4. The method according to any one of claims 1-3, wherein, In S20, the solute in the oxidizing solution includes one or more selected from nitric acid, sulfuric acid and perchloric acid, and the solvent includes water.

5. The method according to any one of claims 1-4, wherein, In S20, the grinding speed is 100rpm-1200rpm.

6. The method according to any one of claims 1-5, wherein, In S20, the grinding instrument includes a ball mill.

7. The method according to any one of claims 1-6, wherein, In S20, the total volume ratio of all materials in the grinder is 1 / 5 to 3 / 4, based on the volumetric capacity of the grinder.

8. The method according to any one of claims 1-7, wherein, In S10, the volumetric particle size Dv50 of the raw material is 3μm-15μm; and / or, In S10, the volumetric particle size Dv90 of the raw material is 8μm-30μm.

9. The method according to claim 8, wherein, In S10, the volumetric particle size Dv50 of the raw material is 4μm-6μm; and / or, In S10, the volumetric particle size Dv90 of the raw material is 9μm-12μm.

10. The method according to any one of claims 1-8, wherein, The raw material is prepared by the following method: the carbon source is heated to 1000℃-1600℃ at a rate of ≤10℃ / min under a protective gas atmosphere and held at that temperature for 1h-24h, and then crushed to obtain the raw material.

11. A secondary battery, comprising a negative electrode, said negative electrode comprising a carbonaceous material prepared by the method of any one of claims 1-10.

12. An electrical device comprising the secondary battery as described in claim 11.

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