A residue-derived hard carbon anode material, its preparation method and a lithium-ion battery

Abstract

The present invention provides a residue-derived hard carbon anode material, a preparation method thereof, and a lithium-ion battery. Wherein, the preparation method includes: using vacuum residue as a raw material, performing low-temperature cracking and coking in a nitrogen-containing atmosphere to obtain a nitrogen-containing coke precursor; under the catalytic action of an external catalyst, subjecting the nitrogen-containing coke precursor to high-temperature catalytic pyrolysis, cross-linking, and polycondensation reactions to obtain a carbon precursor material; infiltrating the carbon precursor material into an organic solution containing an organic lithium salt and then adding an anion source to perform surface modification on it to obtain the residue-derived hard carbon anode material. Using the residue-derived hard carbon anode material provided by the present invention as the anode material of a lithium-ion battery, it has excellent performance and exhibits high-capacity, high first Coulomb efficiency, high-rate, and long-cycle electrochemical performance.

Description

Technical Field

[0001] The present invention relates to a residue-derived hard carbon anode material, a preparation method thereof, and a lithium-ion battery, belonging to the technical field of battery materials, and more specifically to the technical field of lithium-ion battery anode materials. Background Art

[0002] Due to characteristics such as large interlayer spacing, low cost, and relatively simple synthesis methods, hard carbon materials have received extensive attention in the field of lithium-ion battery anode materials. The main factors limiting their commercial application are the insufficient first-cycle Coulombic efficiency, long-cycle stability, and poor rate performance of the hard carbon anode materials used in the prior art.

[0003] In view of the above deficiencies, some existing solutions include using different carbon sources or changing the heat treatment process of the materials to improve the performance of hard carbon. However, these solutions often fail to effectively improve the first-cycle Coulombic efficiency, long-cycle stability, and rate performance of hard carbon anode materials, and may increase their production costs.

[0004] In addition, current hard carbon materials often require complex post-treatment techniques to improve their surface characteristics. These complex post-treatment techniques are costly and have limited efficiency. Therefore, developing hard carbon anode materials with lower costs and better performance still has important industrial application value and market potential. Summary of the Invention

[0005] In order to solve the above-mentioned disadvantages and deficiencies, an object of the present invention is to provide a preparation method for a residue-derived hard carbon anode material.

[0006] Another object of the present invention is to provide a residue-derived hard carbon anode material prepared by the above-mentioned preparation method for a residue-derived hard carbon anode material.

[0007] Still another object of the present invention is to provide a lithium-ion battery, the anode material of which includes the above-mentioned residue-derived hard carbon anode material.

[0008] In order to achieve the above objects, on the one hand, the present invention provides a preparation method for a residue-derived hard carbon anode material, wherein the preparation method includes:

[0009] Step (a): Using vacuum residue as a raw material, performing low-temperature cracking coking in a nitrogen-containing atmosphere to obtain a nitrogen-containing coke precursor;

[0010] Step (b): Under the catalytic action of an external catalyst, subjecting the nitrogen-containing coke precursor to high-temperature catalytic pyrolysis, cross-linking, polycondensation and other reactions to obtain a carbon precursor material;

[0011] Step (c): Immerse the carbon precursor material in an organic solution containing an organolithium salt, and then add an anion source to perform surface modification thereon, i.e., surface defect shielding and liquid-phase lithium supplementation, to obtain a residue-derived hard carbon anode material.

[0012] As a specific embodiment of the above preparation method of the present invention, in step (a), the vacuum residue is a vacuum residue with a high carbon-hydrogen ratio, and its carbon-hydrogen weight percentage > 18. Additionally, on the basis of the carbon-hydrogen weight percentage > 18, its volatile matter weight percentage can be further controlled to be less than 16%.

[0013] As a specific embodiment of the above preparation method of the present invention, in step (a), the nitrogen-containing atmosphere includes one or a combination of several of nitrogen, nitric oxide, nitrogen dioxide, ammonia gas, etc.

[0014] As a specific embodiment of the above preparation method of the present invention, in step (a), the temperature of the low-temperature cracking coking is 400 - 550 °C, and the time is 12 - 36 h to ensure that the raw material is fully coked and an exogenous component, i.e., a nitrogen component, is introduced.

[0015] As a specific embodiment of the above preparation method of the present invention, in step (b), the exogenous catalyst can effectively promote high-temperature pyrolysis, cross-linking, and polycondensation reactions, and it is a transition metal salt, etc.

[0016] Preferably, the transition metal salt includes one or a combination of several of nickel sulfate, copper sulfate, zinc sulfate, chromium chloride, etc.

[0017] As a specific embodiment of the above preparation method of the present invention, in step (b), the temperature of the high-temperature catalytic pyrolysis, cross-linking, polycondensation, etc. reactions is 900 - 1200 °C, and the time is 0.5 - 4 h.

[0018] In step (b) of the above preparation method of the present invention, using a transition metal salt, etc. as an exogenous catalyst can regulate the aromatic units, side-chain structures, and the size of the graphite crystal domain in the nitrogen-containing coke precursor, generate a carbon precursor material with the characteristics of an ordered and disordered phase structure, and further regulate the pore structure of the carbon precursor material.

[0019] As a specific embodiment of the above preparation method of the present invention, in step (c), the organolithium salt includes one or a combination of several of lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl)imide, lithium tetrahydrofuran carboxylate, and lithium tris(trifluoromethylsulfonyl)methyl, etc.

[0020] As a specific embodiment of the above preparation method of the present invention, in step (c), the organic solution containing an organolithium salt includes a toluene or dichloromethane solution containing an organolithium salt.

[0021] As a specific embodiment of the preparation method described above of the present invention, in step (c), the anion source includes one or a combination of several of sulfate ions, chloride ions, bromide ions, etc.

[0022] As a specific embodiment of the preparation method described above of the present invention, in step (c), the temperature of the surface modification is 90 - 150 °C, and the time is 1 - 5 h.

[0023] In step (c) of the preparation method described above of the present invention, the carbon precursor material is infiltrated into an organic solution containing an organolithium salt, and then an anion source is added. The anion source undergoes a substitution reaction with the organic anion in the organolithium salt to generate a lithium salt of the corresponding anion on the surface of the carbon precursor material, so as to repair the pores and defects on the surface of the carbon precursor material, and at the same time increase the lithium content in the electrode material, thereby obtaining a hard carbon negative electrode material with a lithium-containing and defect-free surface.

[0024] On the other hand, the present invention also provides a residue-derived hard carbon negative electrode material, wherein the residue-derived hard carbon negative electrode material is prepared by the preparation method of the residue-derived hard carbon negative electrode material described above, nitrogen atoms are in-situ filled in its carbon matrix, the surface has no defects and is rich in lithium, and the interior is full of pores.

[0025] As a specific embodiment of the residue-derived hard carbon negative electrode material described above of the present invention, calculated based on the total weight of the residue-derived hard carbon negative electrode material being 100%, the lithium content on its surface > 0.5 wt%, and the closed pore volume > 0.8 cm 3 / g.

[0026] The residue-derived hard carbon negative electrode material having a defect-free and lithium-rich surface can improve the Coulomb efficiency during the charge and discharge process of the hard carbon negative electrode material. The interior being full of pores can improve the conductivity and structural stability of the hard carbon negative electrode material, thereby improving the rate performance and cycle stability.

[0027] On yet another aspect, the present invention also provides a lithium-ion battery, wherein the negative electrode material of the lithium-ion battery includes the residue-derived hard carbon negative electrode material described above. The lithium-ion battery whose negative electrode material contains the residue-derived hard carbon negative electrode material provided by the present invention exhibits excellent electrochemical properties such as high energy density, high rate discharge capacity, and long cycle life.

[0028] Compared with the prior art, the beneficial technical effects that the present invention can achieve include:

[0029] 1. The present invention performs low-temperature cracking and coking of a vacuum residue oil feedstock in a nitrogen-containing atmosphere, and the nitrogen atoms in the nitrogen-containing atmosphere are "filled" into the carbon matrix in situ (when the nitrogen-containing atmosphere also contains oxygen, such as when the nitrogen-containing atmosphere is NOx, the oxygen combines with the hydrogen component in the feedstock to form water overflow during the cracking and coking process; when the nitrogen-containing atmosphere is NH3, the hydrogen contained in the nitrogen-containing atmosphere combines with the oxygen component in the vacuum residue oil feedstock to form water overflow during the cracking and coking process). Exogenous components are introduced during the cracking and coking, and the coke precursor is modified, which is conducive to forming an efficient and fast conductive network and lithium ion "pathway" in the hard carbon negative electrode material, thereby achieving high rate performance.

[0030] 2. The present invention uses transition metal salts as exogenous catalysts to regulate the high-temperature catalytic pyrolysis, cross-linking and polycondensation processes, thereby regulating the pore structure of the carbon precursor material; at the same time, the exogenous catalyst can also regulate the aromatic units, side chain structures and graphite crystal domain sizes in the nitrogen-containing coke precursor to generate a carbon precursor material with both ordered and disordered phase structures, so that the final hard carbon negative electrode material can achieve high capacity while achieving excellent material stability.

[0031] 3. The present invention allows lithium ions to be uniformly deposited on the surface of the residual oil-derived hard carbon negative electrode material to repair the surface open pore structure, surface defects, etc., reduce the surface defects of the hard carbon negative electrode material, and at the same time introduce a certain amount of lithium supplement, thereby increasing the lithium content in the electrode; this is beneficial to reducing the side reaction activity on the surface of the hard carbon negative electrode material, achieving high cycle stability and high first coulomb efficiency.

[0032] 4. The preparation method provided by the present invention has low cost and can significantly improve the electrochemical performance of hard carbon negative electrode materials. It also provides a new way for the efficient utilization of vacuum residue oil, which is beneficial to environmental protection and resource recycling.

[0033] In summary, the preparation method of the residue oil-derived hard carbon negative electrode material provided by the present invention adopts the three strategies of "low-temperature cracking coking-high-temperature catalytic pyrolysis-organic lithium salt modification" to prepare the residue oil-derived hard carbon negative electrode material in synergy. The three strategies in the preparation method are indispensable and the order cannot be reversed; the carbon matrix of the residue oil-derived hard carbon negative electrode material thus prepared is in situ filled with nitrogen atoms, the surface is defect-free and lithium-rich and the interior is full of pores; the residue oil-derived hard carbon negative electrode material is used as the negative electrode material of lithium-ion batteries, and its performance is superior, showing high first library, high rate and long cycle electrochemical properties. For example, in some embodiments of the present invention, the residue oil-derived hard carbon negative electrode material has an initial reversible specific capacity greater than 420mAh / g, an initial coulomb efficiency greater than 80%, and has a high rate (≥10C) and long cycle performance (≥2000 times), which can greatly improve its application performance in lithium-ion batteries, and solve the problems of high surface side reaction activity, low initial coulomb efficiency and poor cycle performance of existing hard carbon negative electrode materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0035] Figure 1 It is a transmission electron microscope image of the hard carbon anode material derived from residual oil provided in Embodiment 1 of the present invention.

[0036] Figure 2 It is the first-cycle charge-discharge curve of the hard carbon anode material derived from residual oil provided in Embodiment 1 of the present invention.

[0037] Figure 3 It is the rate performance diagram of the hard carbon anode material derived from residual oil provided in Embodiment 1 of the present invention.

[0038] Figure 4 It is the cycle performance diagram of the hard carbon anode material derived from residual oil provided in Embodiment 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] It should be noted that the term "comprising" and any variations thereof in the description and claims of the present invention and the above drawings are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or are inherent to these processes, methods, products or devices.

[0040] The "ranges" disclosed in the present invention are given in the form of lower and upper limits. There can be one or more lower limits and one or more upper limits respectively. A given range is defined by selecting a lower limit and an upper limit. The selected lower limit and upper limit define the boundary of a particular range. All ranges defined in this way are combinable, 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 particular parameter, it is understood that ranges of 60 - 110 and 80 - 120 are also expected. In addition, if the minimum range values listed are 1 and 2, and the maximum range values listed are 3, 4 and 5, then the following ranges are all expected: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4 and 2 - 5.

[0041] In the present invention, unless otherwise specified, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where both a and b are real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" are fully listed in the present invention, and "0 - 5" is just an abbreviated representation of these numerical combinations.

[0042] In the present invention, if there is no special instruction, all the embodiments and preferred embodiments mentioned in the present invention can be combined with each other to form a new technical solution.

[0043] In the present invention, if there is no special instruction, all the technical features and preferred features mentioned in the present invention can be combined with each other to form a new technical solution.

[0044] In order to make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below in combination with the attached tables, drawings and embodiments. The following described embodiments are some embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention. For those conditions not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments whose manufacturers are not specified, they are all conventional products that can be obtained through commercial purchase.

[0045] Example 1

[0046] This example provides a hard carbon anode material derived from residue oil, which is prepared by a preparation method including the following specific steps:

[0047] Step (a): Take 200 g of vacuum residue with a carbon-hydrogen weight percentage greater than 18 as the raw material, and perform low-temperature cracking coking treatment at 480 °C for 24 hours in a mixed atmosphere containing N2 and NO2 (N2:NO2 = 95 v%:5 v%) to obtain a nitrogen-containing coke precursor, which is a black solid;

[0048] Step (b): Mechanically mix the nitrogen-containing coke precursor obtained in step (a) with 20 g of nickel sulfate, perform catalytic pyrolysis at 1000 °C for 2 hours, then repeatedly wash it 3 times with deionized water, and then dry it at 60 °C for 12 hours to obtain a carbon precursor material;

[0049] Step (c): Immerse the carbon precursor material obtained in step (b) in 1 L of a toluene solution (2 M) containing lithium trifluoromethanesulfonate, and then slowly add 20 mL of concentrated sulfuric acid as a sulfate anion source. Conduct an oil bath at 120 °C for 4 hours to achieve surface modification treatment of the carbon surface, and finally prepare a residue-derived hard carbon anode material, denoted as HC-480-1000-120.

[0050] Example 2

[0051] This example provides a residue-derived hard carbon anode material, which is prepared by a preparation method including the following specific steps:

[0052] Step (a): Take 150 g of vacuum residue with a carbon-hydrogen weight percentage greater than 18 as a raw material, and conduct low-temperature cracking coking treatment at 500 °C for 26 hours in a single atmosphere containing N2 to obtain a nitrogen-containing coke precursor, which is a black solid;

[0053] Step (b): Mechanically mix the nitrogen-containing coke precursor obtained in step (a) with 15 g of copper sulfate, conduct catalytic pyrolysis at a high temperature of 1100 °C for 3 hours, then wash it repeatedly with deionized water 3 times, and then dry it at 60 °C for 12 hours to obtain a carbon precursor material;

[0054] Step (c): Immerse the carbon precursor material obtained in step (b) in 1 L of a toluene solution (2 M) containing lithium trifluoromethanesulfonate, slowly add 20 mL of concentrated hydrochloric acid as a chloride anion source, conduct an oil bath at 120 °C for 4 hours to achieve surface modification treatment of the carbon surface, and finally prepare a residue-derived hard carbon anode material, denoted as HC-500-1100-120.

[0055] Example 3

[0056] This example provides a residue-derived hard carbon anode material, which is prepared by a preparation method including the following specific steps:

[0057] Step (a): Take 150 g of vacuum residue with a carbon-hydrogen weight percentage greater than 18 as a raw material, and conduct low-temperature coking treatment at 450 °C for 26 hours in a mixed gas of N2 and nitric oxide (NO) (N2:NO = 97 v%:3 v%) to obtain a nitrogen-containing coke precursor, which is a black solid;

[0058] Step (b): Mechanically mix the nitrogen-containing coke precursor obtained in step (a) with 15 g of copper sulfate, conduct catalytic pyrolysis at a high temperature of 950 °C for 3 hours, then wash it repeatedly with deionized water 3 times, and then dry it at 60 °C for 12 hours to obtain a carbon precursor material;

[0059] Step (c): Immerse the carbon precursor material obtained in step (b) in 1 L of toluene solution (2 M) containing lithium trifluoromethanesulfonate, slowly add 20 mL of concentrated hydrochloric acid as a chloride anion source, and carry out a surface modification treatment on the carbon surface in an oil bath at 110 °C for 4 hours, finally obtaining a residue-derived hard carbon anode material, denoted as HC-450-950-110.

[0060] Example 4

[0061] This example provides a residue-derived hard carbon anode material, which is prepared by a preparation method including the following specific steps:

[0062] Step (a): Take 150 g of vacuum residue with a carbon-hydrogen weight percentage greater than 18 as the raw material, and carry out a low-temperature coking treatment at 530 °C for 26 hours in a mixed gas containing N2 and ammonia (NH3) (N2:NH3 = 92 v%:8 v%), obtaining a nitrogen-containing coke precursor, which is a black solid;

[0063] Step (b): Mechanically mix the nitrogen-containing coke precursor obtained in step (a) with 15 g of copper sulfate, carry out catalytic pyrolysis at a high temperature of 1080 °C for 3 hours, then wash it repeatedly with deionized water 3 times, and then dry it at 60 °C for 12 hours to obtain a carbon precursor material;

[0064] Step (c): Immerse the carbon precursor material obtained in step (b) in 1 L of toluene solution (2 M) containing lithium trifluoromethanesulfonate, slowly add 20 mL of concentrated hydrochloric acid as a chloride anion source, and carry out a surface modification treatment on the carbon surface in an oil bath at 130 °C for 4 hours, finally obtaining a residue-derived hard carbon anode material, denoted as HC-530-1080-130.

[0065] Example 5

[0066] This example provides a residue-derived hard carbon anode material, which is prepared by a preparation method including the following specific steps:

[0067] Step (a): Take 150 g of vacuum residue with a carbon-hydrogen weight percentage greater than 18 as the raw material, and carry out a low-temperature cracking coking treatment at 440 °C for 26 hours in a gas containing single nitric oxide, obtaining a nitrogen-containing coke precursor, which is a black solid;

[0068] Step (b): Mechanically mix the nitrogen-containing coke precursor obtained in step (a) with 15 g of copper sulfate, carry out catalytic pyrolysis at a high temperature of 970 °C for 3 hours, then wash it repeatedly with deionized water 3 times, and then dry it at 60 °C for 12 hours to obtain a carbon precursor material;

[0069] Step (c): Immerse the carbon precursor material obtained in step (b) in 1 L of toluene solution (2 M) containing lithium trifluoromethanesulfonate, slowly add 20 mL of concentrated hydrochloric acid as a chloride anion source, and perform a surface modification treatment on the carbon surface in an oil bath at 130 °C for 4 hours. Finally, a residue-derived hard carbon anode material is prepared and denoted as HC-440-970-130.

[0070] Example 6

[0071] This example provides a residue-derived hard carbon anode material, which is prepared by a preparation method including the following specific steps:

[0072] Step (a): Take 150 g of vacuum residue with a carbon-hydrogen weight percentage greater than 18 as the raw material, and perform low-temperature cracking coking treatment at 460 °C for 26 hours in a mixed gas of nitrogen and ammonia (N2:NH3 = 94 v%:6 v%) to obtain a nitrogen-containing coke precursor, which is a black solid.

[0073] Step (b): Mechanically mix the nitrogen-containing coke precursor obtained in step (a) with 15 g of copper sulfate, perform catalytic pyrolysis at a high temperature of 1000 °C for 3 hours, then repeatedly wash with deionized water 3 times, and then dry at 60 °C for 12 hours to obtain a carbon precursor material.

[0074] Step (c): Immerse the carbon precursor material obtained in step (b) in 1 L of toluene solution (2 M) containing lithium trifluoromethanesulfonate, slowly add 20 mL of concentrated hydrochloric acid as a chloride anion source, and perform a surface modification treatment on the carbon surface in an oil bath at 120 °C for 4 hours. Finally, a residue-derived hard carbon anode material is obtained and denoted as HC-460-1000-120.

[0075] Example 7

[0076] This example provides a residue-derived hard carbon anode material, which is prepared by a preparation method including the following specific steps:

[0077] Step (a): Take 150 g of vacuum residue with a carbon-hydrogen weight percentage greater than 18 as the raw material, and perform low-temperature cracking coking treatment at 550 °C for 26 hours in a mixed gas of nitrogen and argon (N2:Ar = 90 v%:10 v%) to obtain a nitrogen-containing coke precursor, which is a black solid.

[0078] Step (b): Mechanically mix the nitrogen-containing coke precursor obtained in step (a) with 15 g of copper sulfate, perform catalytic pyrolysis at a high temperature of 1000 °C for 3 hours, then repeatedly wash with deionized water 3 times, and then dry at 60 °C for 12 hours to obtain a carbon precursor material.

[0079] Step (c): Immerse the carbon precursor material obtained in step (b) in 1 L of a toluene solution (2 M) containing lithium trifluoromethanesulfonate, slowly add 20 mL of concentrated hydrochloric acid as a chloride anion source, and perform an oil bath at 140 °C for 4 hours to achieve surface modification treatment of the carbon surface, finally obtaining a residue-derived hard carbon anode material, denoted as HC-550-1000-140.

[0080] Example 8

[0081] This example provides a residue-derived hard carbon anode material, which is prepared by a preparation method including the following specific steps:

[0082] Step (a): Take 150 g of vacuum residue with a carbon-hydrogen weight percentage greater than 18 as the raw material, perform low-temperature cracking coking treatment at 480 °C in pure nitrogen dioxide for 26 hours to obtain a nitrogen-containing coke precursor, which is a black solid;

[0083] Step (b): Mechanically mix the coke precursor obtained in step (a) with 15 g of copper sulfate, perform catalytic pyrolysis at a high temperature of 1000 °C for 3 hours, then wash it repeatedly with deionized water 3 times, and then dry it at 60 °C for 12 hours to obtain a carbon precursor material;

[0084] Step (c): Immerse the carbon precursor material obtained in step (b) in 1 L of a toluene solution (2 M) containing lithium trifluoromethanesulfonate, slowly add 20 mL of concentrated hydrochloric acid as a chloride anion source, and perform an oil bath at 120 °C for 4 hours to achieve surface modification treatment of the carbon surface, finally obtaining a residue-derived hard carbon anode material, denoted as HC-480-1000-120.

[0085] Comparative Example 1

[0086] This comparative example provides a hard carbon anode material, which is different from Example 1 only in that: step (b) is omitted, that is, high-temperature catalytic pyrolysis is not carried out. The hard carbon anode material prepared in this comparative example is denoted as Comparative Sample 1.

[0087] Comparative Example 2

[0088] This comparative example provides a hard carbon anode material, which is different from Example 1 only in that: the coke precursor used is a coke precursor purchased on the market and not obtained by low-temperature cracking coking in a nitrogen-containing atmosphere. The hard carbon anode material prepared in this comparative example is denoted as Comparative Sample 2.

[0089] Comparative Example 3

[0090] This comparative example provides a hard carbon anode material, which is different from Example 1 only in that: step (c) is omitted, that is, surface modification treatment of the carbon surface is not carried out. The hard carbon anode material prepared in this comparative example is denoted as Comparative Sample 3.

[0091] Characterization test example

[0092] This characterization test example conducts transmission electron microscopy analysis on the residual oil-derived hard carbon anode material provided in Example 1 of the present invention. The obtained transmission electron micrograph is as shown in Figure 1 . It can be seen from Figure 1 that in the residual oil-derived hard carbon anode material, the ordered regions and disordered regions are intertwined with each other, and the interior is filled with pore structures but there are no defects on the surface.

[0093] Electrochemical performance test example

[0094] In this test example, the residual oil-derived hard carbon anode materials provided in Examples 1-8 of the present invention and the hard carbon anode materials provided in Comparative Examples 1-3 are respectively applied to CR2032-type batteries to investigate their electrochemical performance, specifically including:

[0095] First, mix the hard carbon anode material, polyvinylidene fluoride (PVDF), and conductive carbon black (Super P) in a mass ratio of 90:5:5, add an appropriate amount of N-methylpyrrolidone, and the solid content of the obtained slurry after mixing is 33% to make a viscous and uniform slurry;

[0096] Second, uniformly coat the obtained slurry on the copper foil and vacuum dry it at 80 °C for 12 hours to obtain a pole piece;

[0097] Third, use the above-prepared pole piece as the negative electrode, select a pure lithium piece as the counter electrode, use a 1 mol / L LiPF6 solution as the electrolyte, the solvent of this electrolyte is composed of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) mixed in a volume ratio of 1:1:1, use polypropylene fiber as the separator, and complete the assembly of the button battery in an anhydrous and oxygen-free glove box;

[0098] Finally, in the charge and discharge test, the battery is tested for rate performance at a rate of 0.1C - 10C within a voltage range of 0.001 to 3.0V; after being activated 10 times at 0.1C, it is cycled 2000 times at 3C to test the cycle performance. The experimental data are shown in Table 1 and Figures 2 - 4 as shown.

[0099] Table 1 Performance test results of batteries prepared from different hard carbon anode materials

[0100]

[0101] From Table 1 and Figures 2 - 4Data analysis shows that the lithium-ion batteries with the anode materials containing the hard carbon anode materials derived from residual oil provided in Examples 1-8 of the present invention exhibit excellent first reversible specific capacity, high first Coulombic efficiency, and good cycling performance. If any link in the preparation method is changed, such as the coking pyrolysis treatment, catalytic pyrolysis, or surface modification step, it will directly affect the first Coulombic efficiency and cycle life of the battery, resulting in a significant decrease in these parameters. In the comparative experiments, such as Comparative Example 1 and Comparative Example 2 in which the key high-temperature catalytic pyrolysis and low-temperature coking pyrolysis treatments of the present invention are respectively omitted, the first reversible specific capacity, first Coulombic efficiency, and cycling stability of the prepared hard carbon anode materials are much lower than those of the hard carbon anode materials derived from residual oil provided in Example 1 of the present invention. At the same time, due to excessive side reactions caused by no surface modification in Comparative Example 3, its first Coulombic efficiency and cycling performance are also far inferior to those of the hard carbon anode materials derived from residual oil provided in Example 1 of the present invention. The above experimental data and related descriptions fully prove the key and indispensable nature of each operation step in the preparation process of the present invention for improving battery performance.

[0102] As described above, the above are only specific embodiments of the present invention and cannot be used to limit the scope of the invention implementation. Therefore, the replacement of equivalent components or equivalent changes and modifications made according to the protection scope of the present invention patent should still fall within the scope covered by this patent. In addition, the technical features in the present invention can be freely combined and used among technical features, between technical features and technical inventions, and between technical inventions.

Claims

1. A preparation method of a residue-derived hard carbon anode material, characterized in that, The preparation method includes: Step (a): Using vacuum residue as raw material, performing low-temperature cracking coking at 400 - 550 °C in a nitrogen-containing atmosphere to obtain a nitrogen-containing coke precursor; Step (b): Under the catalytic action of an external catalyst, subjecting the nitrogen-containing coke precursor to high-temperature catalytic pyrolysis, cross-linking, and polycondensation reactions at 900 - 1200 °C to obtain a carbon precursor material; Step (c): Immersing the carbon precursor material in an organic solution containing an organic lithium salt and then adding an anion source to perform surface modification on it at 90 - 150 °C to obtain a vacuum residue-derived hard carbon anode material.

2. The preparation method according to claim 1, characterized in that, In step (a), the vacuum residue is a vacuum residue with a high carbon-hydrogen ratio, and its carbon-hydrogen weight percentage > 18.

3. The preparation method according to claim 1 or 2, characterized in that, In step (a), the nitrogen-containing atmosphere includes one or a combination of several of nitrogen, nitric oxide, nitrogen dioxide, and ammonia.

4. The preparation method according to claim 1 or 2, characterized in that, In step (a), the time for the low-temperature cracking coking is 12 - 36 h.

5. The preparation method according to claim 1, characterized in that, In step (b), the external catalyst is a transition metal salt.

6. The preparation method according to claim 5, wherein The transition metal salt includes one or a combination of several of nickel sulfate, copper sulfate, zinc sulfate, and chromium chloride.

7. The preparation method according to any one of claims 1 and 5 to 6, characterized in that In step (b), the temperature for the high-temperature catalytic pyrolysis, cross-linking, and polycondensation reactions is, and the time is 0.5 - 4 h.

8. The preparation method according to claim 1, characterized in that, In step (c), the organic lithium salt includes one or a combination of several of lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl)imide, lithium tetrahydrofuran carboxylate, and lithium tris(trifluoromethylsulfonyl)methyl.

9. The preparation method according to claim 1 or 8, characterized in that, The anion source includes one or a combination of several of sulfate ions, chloride ions, and bromide ions.

10. The preparation method according to any one of claims 1, 8 - 9, characterized in that, In step (c), the time for the surface modification is 1 - 5 h.

11. A hard carbon anode material derived from residual oil, characterized in that, The vacuum residue-derived hard carbon anode material is prepared by the preparation method of the vacuum residue-derived hard carbon anode material according to any one of claims 1 - 10. Nitrogen atoms are in-situ filled in its carbon matrix, the surface has no defects and is rich in lithium, and the interior is full of pores.

12. The hard carbon anode material derived from residual oil according to claim 11, wherein, Based on the total weight of the residue-derived hard carbon anode material being 100%, the content of lithium on its surface is > 0.5 wt%, and the closed pore volume is > 0.8 cm 3 / g.

13. A lithium-ion battery, characterized in that, The anode material of the lithium-ion battery includes the vacuum residue-derived hard carbon anode material according to claim 11 or 12.

Images