A soft carbon and graphite composite negative electrode material, a preparation method thereof and a lithium ion battery

Abstract

The embodiment provides a soft carbon and graphite composite negative electrode material, a preparation method thereof and a lithium ion battery. The composite negative electrode material comprises soft carbon and graphite balls dispersed on the surface of the soft carbon, and part of the graphite balls is embedded in the interior of the soft carbon. The preparation method comprises the following steps: (1) coating a catalyst solution on the surface of a carbon material to obtain a mixture through first drying; (2) performing carbonization treatment on the mixture in step (1) to obtain carbonized material; (3) sequentially performing acid washing treatment and water washing treatment on the carbonized material in step (2), and obtaining the soft carbon and graphite composite negative electrode material after second drying. The soft carbon and graphite composite negative electrode material prepared by the method is embedded and combined, has excellent kinetic performance, high negative electrode material capacity and high initial efficiency.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion batteries, and to a composite anode material of soft carbon and graphite, and more particularly to a composite anode material of soft carbon and graphite, its preparation method, and a lithium-ion battery thereof. Background Technology

[0002] With the continuous development of the new energy industry, lithium-ion batteries, as green and environmentally friendly new energy batteries, have experienced exceptionally rapid growth. As the application fields of lithium batteries expand, higher requirements are being placed on their energy density, rate performance, cycle performance, high and low temperature performance, and safety performance.

[0003] Among existing lithium-ion batteries, the most widely used are those with graphite as the negative electrode system. Due to its high degree of graphitization and highly oriented layered structure, it has poor compatibility with existing organic electrolyte systems. During the first charge and discharge process, lithium co-intercalation with organic solvents, graphite layer expansion and peeling, and graphite particle breakage and pulverization occur, resulting in electrode structure damage, poor charge and discharge cycle performance, and battery safety issues.

[0004] However, soft carbon and hard carbon anode materials exhibit a disordered multi-microporous structure and have a higher lithium potential than graphite. This characteristic enables them to quickly store and de-lithium and has low impedance during charging and discharging. Therefore, composite anode materials of soft carbon and hard carbon have become the direction for the application of lithium-ion battery anode materials.

[0005] CN105261734B discloses a method for directly physically mixing soft carbon and graphite in a certain proportion to obtain composite anode materials. This method requires the separate preparation of the desired soft carbon and graphite, involves many preparation steps, high energy consumption, and a long cycle.

[0006] CN106252596B discloses a method for preparing a soft carbon-graphite composite anode material. The method involves impregnating natural spherical graphite with pitch through heating and pressurization into the graphite pores, followed by carbonization and cooling to obtain an intermediate product. This intermediate product is then carbonized, pulverized, and graded to obtain the soft carbon-graphite composite anode material. This method, in addition to conventional carbonization, involves high-pressure impregnation, which places high demands on equipment and poses significant safety risks due to the high pressure. Furthermore, the carbonized sample agglomerates, requiring pulverization and grading to obtain the target product. This step reduces the yield and increases production costs.

[0007] CN110407204A discloses a method for preparing natural coal char at low temperature. This method involves dissolving a metal chloride salt in an organic solvent to obtain a catalyst-containing solution, then adding natural coal char powder and stirring at low temperature. The solution is then vacuum freeze-dried to obtain a carbon / metal composite material, followed by heat treatment at 1400℃, and finally acid washing to remove impurities to obtain battery-grade graphite material. This method involves low-temperature stirring and vacuum freeze-drying, as well as the use of a large proportion of organic solvents. Solvent removal requires high energy consumption and poses certain safety hazards, making it unsuitable for industrial-scale production.

[0008] Therefore, how to mass-produce a soft carbon and graphite composite anode material with high safety and electronic conductivity at low cost is an important research direction in this field. Summary of the Invention

[0009] The purpose of this invention is to provide a soft carbon and graphite composite anode material with high safety and electronic conductivity, its preparation method, and a lithium-ion battery.

[0010] To achieve this objective, the present invention adopts the following technical solution:

[0011] One of the objectives of this invention is to provide a composite anode material of soft carbon and graphite, wherein the composite anode material comprises soft carbon and graphite spheres dispersed on the surface of the soft carbon, and a portion of the graphite spheres are embedded inside the soft carbon.

[0012] In this invention, graphite is spherical and embedded with soft carbon. A portion of each graphite sphere is independently embedded in the soft carbon, while the other portion is on the surface of the soft carbon. Overall, the graphite spheres are uniformly dispersed in and on the surface of the soft carbon.

[0013] As a preferred technical solution of the present invention, the diameter of the graphite sphere is 0.01 to 10 μm, wherein the diameter can be 0.01 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable. Preferably, it is 0.01 to 2 μm, and more preferably, it is 0.01 to 0.5 μm.

[0014] In this invention, when the diameter of the graphite spheres is small, the internal pore structure is also correspondingly smaller, resulting in stronger capillary forces, which is more conducive to the adsorption of electrolyte and accelerates the liquid-phase diffusion of lithium ions. In addition, the smaller the size of the graphite spheres, the smaller the ratio of their particle size to that of soft carbon, making them less susceptible to peeling caused by external mechanical forces.

[0015] Preferably, the graphite spheres have a hollow structure.

[0016] Preferably, the XRD pattern of the negative electrode composite material has two peaks, which are a soft carbon peak and a graphite peak.

[0017] Preferably, the peak intensity value at the peak vertex of the soft carbon peak is h, and the peak intensity value at the peak vertex of the graphite peak is H, where r = H / h, 0 < r ≤ 12. The value of r can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12, etc., but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable. Preferably, 0.8 ≤ r ≤ 8.

[0018] In the present invention, the characteristic of the graphite (002) peak is 2θ G ∈(26.2, 26.6), and the full width at half maximum of this graphite characteristic peak is denoted as FWHM G , FWHM G ∈(0.1, 0.4), and the interlayer spacing of graphite is denoted as G-d 002 , G-d 002 ∈(0.3354, 0.3400), and the graphitization degree of graphite is 70% ≤ g < 100%; the characteristic of the soft carbon (002) peak is 2θ S ∈(25.0, 26.2), and the full width at half maximum of this soft carbon characteristic peak is denoted as FWHM S , FWHM S ∈(0.4, 2.0), and the interlayer spacing of soft carbon is denoted as S-d 002 , S-d 002 ∈(0.3400, 0.3599); the difference between 2θ of the graphite (002) peak and 2θ of the soft carbon (002) peak is 0° < 2θ G -2θ S <1.6°.

[0019] H is the height of the graphite (002) peak. The specific calculation method of this height is the shortest vertical distance from the peak vertex to the bottom where the peak intensity is 0, and it can also be expressed by the peak intensity value of this peak vertex. h is the height of the soft carbon (002) peak. The specific calculation method of this height is the shortest vertical distance from the peak vertex to the bottom where the peak intensity is 0, and it can also be expressed by the peak intensity value of this peak vertex. r = H / h (both H and h are represented by the vertical distance or the peak intensity value at the same time), r ∈ (0, 12].

[0020] The above 2θ, FWHM, and peak intensity are obtained by analyzing the XRD spectrum of the sample using analysis software such as HighScore Plus and jade.

[0021] In this invention, when r is too small, the catalytic conversion rate is too low, and the capacity, first-efficiency, and kinetic performance of the composite anode material are not good enough; when r is too large, it indicates that the catalytic conversion rate is too high, and the uniformity of the composite anode material is poor and the kinetic performance is not good enough. As a preferred technical solution of this invention, the soft carbon includes any one of asphalt, coal, or petroleum-based carbon materials.

[0022] A second objective of this invention is to provide a method for preparing a composite anode material of soft carbon and graphite as described in the first objective, the method comprising the following steps:

[0023] (1) The catalyst solution is coated on the surface of the carbon material and dried to obtain a mixture;

[0024] (2) The mixture described in step (1) is subjected to carbonization treatment to obtain carbonized material;

[0025] (3) The carbonized material described in step (2) is subjected to acid washing and water washing in sequence, and after a second drying, the composite negative electrode material of soft carbon and graphite is obtained.

[0026] The composite anode material prepared by this invention is a composite anode material of soft carbon and graphite. It is not simply obtained by physically mixing soft carbon and graphite, nor is it formed by bonding soft carbon and graphite with a binder. Instead, a portion of the soft carbon particles (asphalt, coal, petroleum-based carbon materials) is catalytically converted into graphite by a catalyst. Subsequently, the catalyst is removed by acid washing, and then washed with water to obtain a neutral composite anode material of soft carbon and graphite, wherein the graphite is hollow spherical. For a single graphite sphere, part of the graphite sphere is embedded in the soft carbon, and the other part is on the surface of the soft carbon. Therefore, the graphite spheres are uniformly dispersed on the surface of the soft carbon in an embedded state.

[0027] As a preferred technical solution of the present invention, the catalyst solution in step (1) includes any one of the salt solutions of vanadium, chromium, manganese, iron, cobalt, nickel or copper.

[0028] Preferably, the salt solution includes an organic salt solution or an inorganic salt solution.

[0029] Preferably, the catalyst solution comprises any one of cobalt chloride solution, nickel chloride solution, ferric chloride solution, nickel sulfate solution, cobalt nitrate solution, cobalt sulfate solution, or ferric sulfate solution.

[0030] Preferably, the carbon material in step (1) includes any one or a combination of at least two of the following: coal tar pitch calcined coke powder, petroleum pitch calcined coke powder, high-purity coal powder, high-purity coal-based metallurgical coke powder, coal tar pitch calcined raw coke powder, or petroleum pitch calcined raw coke powder. The combination may be a combination of coal tar pitch calcined coke powder and high-purity coal-based metallurgical coke powder, a combination of high-purity coal-based metallurgical coke powder and petroleum pitch calcined raw coke powder, or a combination of coal tar pitch calcined coke powder and petroleum pitch calcined raw coke powder, etc.

[0031] As a preferred technical solution of the present invention, the preparation method of the catalyst solution in step (1) includes: mixing a dispersant, salt and water to obtain the catalyst solution.

[0032] Preferably, the dispersant comprises any one or a combination of at least two of PEG, PVA, SDBS, CMC, CTAB, or PAM, wherein typical but non-limiting examples of the combination include: a combination of PEG and PVA, a combination of PVA and SDBS, a combination of SDBS and CMC, a combination of CMC and CTAB, or a combination of CTAB and PAM, etc.

[0033] Preferably, the salt comprises an organic or inorganic salt of vanadium, chromium, manganese, iron, cobalt, nickel, or copper.

[0034] Preferably, the salt comprises any one of cobalt chloride, nickel chloride, ferric chloride, nickel sulfate, cobalt nitrate, cobalt sulfate, or ferric sulfate.

[0035] Preferably, the mass ratio of the dispersant, salt, and water is (0.03–0.1):(0.7–2):1, wherein the mass ratio can be 0.03:0.7:1, 0.05:0.7:1, 0.09:0.7:1, 0.1:1:1, 0.03:1:1, 0.05:1:1, 0.09:1:1, 0.1:1:1, 0.03:1.5:1, 0.05:1.5:1, 0.09:1.5:1, 0.1:1.5:1, 0.03:2:1, 0.05:2:1, 0.09:2:1, or 0.1:2:1, etc., but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0036] As a preferred embodiment of the present invention, the particle size D50 of the soft carbon in step (1) is 3-30 μm, wherein the particle size D... V 50 can be 3μm, 5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm, 9.5μm, 10μm, 11μm, 13μm, 15μm, 20μm, 25μm or 30μm, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0037] Preferably, the mass ratio of the catalyst solution and soft carbon in step (1) is (0.5 to 2):1, wherein the mass ratio can be 0.5:1, 0.8:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1 or 2:1, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0038] In this invention, if the mass ratio of catalyst solution to soft carbon is too high and the carbonization temperature is too high, it is easy to cause the degree of catalytic conversion to be too high, which will reduce the kinetic performance of the composite anode material. In addition, it will also increase the production cost and reduce the production efficiency. If the mass ratio of catalyst solution to soft carbon is too low, the catalyst cannot catalyze the soft carbon into hollow graphite spheres, resulting in lower capacity, lower first-time efficiency, and poorer kinetic performance of the composite anode material.

[0039] Preferably, the temperature of the first drying step (1) is 120 to 170°C, wherein the temperature can be 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C or 170°C, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0040] Preferably, the drying time in step (1) is 1.5 to 2.5 hours, wherein the time can be 1.5 hours, 1.6 hours, 1.7 hours, 1.8 hours, 1.9 hours, 2.0 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours or 2.5 hours, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0041] As a preferred technical solution of the present invention, the atmosphere of the carbonization treatment in step (2) includes any one or at least two of nitrogen, argon or helium, wherein typical but non-limiting examples of the combination include: a combination of nitrogen and argon, a combination of argon and helium or a combination of nitrogen and helium, etc.

[0042] Preferably, the carbonization temperature is 1100–1300°C, wherein the temperature can be 1100°C, 1120°C, 1140°C, 1160°C, 1180°C, 1200°C, 1220°C, 1240°C, 1260°C, 1280°C, or 1300°C, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0043] The carbonization temperature of this invention is too high, resulting in an excessively high degree of catalytic conversion, which reduces the kinetic performance of the composite anode material. Furthermore, it increases production costs and reduces production efficiency. Conversely, if the carbonization temperature is too low, the catalyst cannot effectively convert soft carbon into hollow graphite spheres, leading to lower capacity, lower initial efficiency, and poorer kinetic performance of the composite anode material.

[0044] Preferably, the carbonized material is obtained by cooling after the carbonization treatment in step (2).

[0045] As a preferred technical solution of the present invention, the acid solution used in the acid washing in step (3) includes hydrochloric acid.

[0046] Preferably, the concentration of the acid solution is 0.8 to 1.2 mol / L, wherein the concentration may be 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, 1.1 mol / L or 1.2 mol / L, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0047] Preferably, the temperature of the second drying step (3) is 120 to 170°C, wherein the temperature can be 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C or 170°C, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0048] Preferably, the drying time in step (1) is 1.5 to 2.5 hours, wherein the time can be 1.5 hours, 1.6 hours, 1.7 hours, 1.8 hours, 1.9 hours, 2.0 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours or 2.5 hours, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0049] As a preferred technical solution of the present invention, the preparation method includes the following steps:

[0050] (1) The catalyst solution is coated on the surface of the carbon material and dried at 120-170°C for 1.5-2.5 h to obtain a mixture;

[0051] (2) The mixture described in step (1) is subjected to carbonization treatment at a temperature of 1100-1300℃ to obtain carbonized material;

[0052] (3) The carbonized material described in step (2) is subjected to acid washing treatment and water washing treatment with a concentration of 0.8 to 1.2 mol / L in sequence, and then dried for 1.5 to 2.5 h at a temperature of 120 to 170 °C to obtain the composite negative electrode material of soft carbon and graphite.

[0053] A third objective of this invention is to provide a lithium-ion battery, the lithium-ion battery comprising a positive electrode material and a negative electrode material, the negative electrode material comprising a composite negative electrode material of soft carbon and graphite as described in one objective.

[0054] Compared with the prior art, the present invention has the following beneficial effects:

[0055] The composite anode material prepared by this invention exhibits excellent kinetic performance, high anode material capacity, and high initial efficiency when applied in lithium-ion batteries. The capacity can reach over 350 mAh / g, the initial efficiency can reach over 92%, and the 2C / 0.2C ratio can be as high as over 88%. Attached Figure Description

[0056] Figure 1 This is the XRD pattern of the soft carbon and graphite composite anode material in Example 1 of the present invention.

[0057] Figure 2 This is a SEM image of the soft carbon and graphite composite anode material in Example 1 of this invention.

[0058] Figure 3 This is a Raman 2D image and its SEM image of the soft carbon and graphite composite negative electrode material in Example 1 of this invention.

[0059] Figure 4 This is a single-point Raman spectrum of graphite particles in the soft carbon and graphite composite negative electrode material in Example 1 of the present invention.

[0060] Figure 5 This is a single-point Raman spectrum of the soft carbon in the soft carbon and graphite composite negative electrode material of Embodiment 1 of the present invention.

[0061] Figure 6 This is the XRD spectrum of the soft carbon and graphite composite anode material in Example 2 of the present invention.

[0062] Figure 7 This is a cross-sectional morphology diagram of the soft carbon and graphite composite negative electrode material in Embodiment 2 of the present invention.

[0063] Figure 8 This is the XRD pattern of the soft carbon and graphite composite anode material in Example 3 of the present invention.

[0064] Figure 9 This is the XRD spectrum of the soft carbon and graphite composite anode material in Example 4 of this invention.

[0065] Figure 10 This is the XRD spectrum of the soft carbon and graphite composite anode material in Example 5 of the present invention.

[0066] Figure 11 This is the graphite single-point Raman spectrum of the soft carbon and graphite composite negative electrode material in Example 5 of the present invention.

[0067] Figure 12 This is a single-point Raman spectrum of the soft carbon composite negative electrode material in Example 5 of the present invention.

[0068] Figure 13 This is the XRD spectrum of the soft carbon and graphite composite anode material in Example 6 of the present invention.

[0069] Figure 14 This is the XRD pattern of the soft carbon and graphite composite anode material in Example 7 of this invention.

[0070] Figure 15 This is the XRD spectrum of the soft carbon and graphite composite anode material in Example 8 of the present invention.

[0071] Figure 16 This is the XRD spectrum of the soft carbon and graphite composite anode material in Example 9 of the present invention.

[0072] Figure 17 This is the XRD pattern of the soft carbon and graphite composite anode material in Example 10 of the present invention.

[0073] Figure 18 This is the XRD pattern of the soft carbon in Comparative Example 2 of this invention.

[0074] Figure 19 This is the XRD pattern of the soft carbon in Comparative Example 3 of this invention.

[0075] Figure 20 This is a cross-sectional morphology diagram of the soft carbon anode material in Comparative Example 3 of the present invention after argon ion cutting and grinding.

[0076] Figure 21 This is the XRD pattern of the composite anode material obtained by physically mixing soft carbon and graphite in Comparative Example 4 of this invention. Detailed Implementation

[0077] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention.

[0078] Example 1

[0079] This embodiment provides a soft carbon and graphite composite anode material and its preparation method:

[0080] (1) Prepare a catalyst solution by mixing PEG, nickel chloride, and water in a ratio of 0.1:2:1. Coat the catalyst solution onto particles with a particle size of D using mechanical force. V The surface of petroleum asphalt-based raw coke powder with a thickness of 10 μm was 50. The mass ratio of catalyst solution to coke powder was 1:1. The mixture was first dried at 150℃ for 2 hours to obtain a mixture.

[0081] (2) The mixture described in step (1) is subjected to carbonization treatment at a temperature of 1300°C in a nitrogen atmosphere roller kiln, and then the carbonized material is cooled to room temperature to obtain carbonized material.

[0082] (3) The carbonized material described in step (2) is subjected to acid washing treatment with 1 mol / L hydrochloric acid solution and water washing treatment until neutral. After drying at 150°C for 2 hours, the composite negative electrode material of soft carbon and graphite is obtained.

[0083] The soft carbon and graphite anode material prepared in this embodiment has a hollow spherical graphite in the composite anode material. Part of the graphite sphere is embedded in the soft carbon, and the other part is on the surface of the soft carbon. The XRD pattern of the composite anode material has a double peak feature at the (002) peak. The smaller 2θ peak is the (002) peak of the soft carbon, and the other is the (002) peak of the graphite. The peak intensity of the graphite (002) peak is H, and the peak intensity of the soft carbon (002) peak is h. The ratio of the two is r = H / h. The r value is shown in Table 1.

[0084] The XRD pattern of the soft carbon and graphite composite anode material prepared in this embodiment is shown below. Figure 1 As shown, the SEM image of the composite anode material is as follows: Figure 2 As shown, the composite anode material was subjected to SEM coupled with laser Raman spectroscopy. The resulting Raman 2D image and its SEM image are shown below. Figure 3 As shown, the single-point Raman spectrum of graphite particles in the composite anode material is as follows. Figure 4 As shown, the single-point Raman spectrum of soft carbon in the composite anode material is as follows. Figure 5 As shown.

[0085] Example 2

[0086] This embodiment provides a soft carbon and graphite composite anode material and its preparation method:

[0087] (1) Prepare a catalyst solution by mixing PEG, nickel chloride, and water in a ratio of 0.1:2:1. Coat the catalyst solution onto particles with a particle size of D using mechanical force. V The surface of petroleum asphalt-based raw coke powder with a thickness of 10 μm was 50. The mass ratio of catalyst solution to coke powder was 0.5:1. The mixture was first dried at 150℃ for 2 hours to obtain a mixture.

[0088] (2) The mixture described in step (1) is subjected to carbonization treatment at a temperature of 1100°C in a nitrogen atmosphere roller kiln, and then the carbonized material is cooled to room temperature to obtain carbonized material.

[0089] (3) The carbonized material described in step (2) is subjected to acid washing treatment with 1 mol / L hydrochloric acid solution and water washing treatment until neutral. After drying at 150°C for 2 hours, the composite negative electrode material of soft carbon and graphite is obtained.

[0090] The soft carbon and graphite composite anode material prepared in this embodiment has a hollow spherical graphite in it. Part of the graphite sphere is embedded in the soft carbon, and the other part is on the surface of the soft carbon. The XRD pattern of the composite anode material has a double peak feature at the (002) peak. The smaller 2θ peak is the (002) peak of the soft carbon, and the other is the (002) peak of the graphite. The peak intensity of the graphite (002) peak is H, and the peak intensity of the soft carbon (002) peak is h. The ratio of the two is r = H / h. The r value is shown in Table 1.

[0091] The XRD pattern of the soft carbon and graphite composite anode material in this embodiment is as follows: Figure 6 As shown, the cross-sectional morphology of the prepared soft carbon and graphite composite anode material after argon ion milling was observed using SEM. Figure 7 As shown.

[0092] Example 3

[0093] This embodiment provides a soft carbon and graphite composite anode material and its preparation method:

[0094] (1) Prepare a catalyst solution by mixing PEG, cobalt chloride, and water in a ratio of 0.1:2:1. Coagulate the catalyst solution onto particles with a particle size of D using mechanical force. V The surface of coal tar pitch-based raw coke powder with a thickness of 9 μm was 50. The mass ratio of catalyst solution to coke powder was 1:1. The mixture was first dried at 150℃ for 2 hours to obtain a mixture.

[0095] (2) The mixture described in step (1) is subjected to carbonization treatment at a temperature of 1100°C in a nitrogen atmosphere roller kiln, and then the carbonized material is cooled to room temperature to obtain carbonized material.

[0096] (3) The carbonized material described in step (2) is subjected to acid washing treatment with 1 mol / L hydrochloric acid solution and water washing treatment until neutral. After drying at 150°C for 2 hours, the composite negative electrode material of soft carbon and graphite is obtained.

[0097] The soft carbon and graphite composite anode material prepared in this embodiment has a hollow spherical graphite in it. Part of the graphite sphere is embedded in the soft carbon, and the other part is on the surface of the soft carbon. The XRD pattern of the composite anode material has a double peak feature at the (002) peak. The smaller 2θ peak is the (002) peak of the soft carbon, and the other is the (002) peak of the graphite. The peak intensity of the graphite (002) peak is H, and the peak intensity of the soft carbon (002) peak is h. The ratio of the two is r = H / h. The r value is shown in Table 1.

[0098] The XRD pattern of the soft carbon and graphite composite anode material prepared in this embodiment is shown in the figure below. Figure 8 As shown.

[0099] Example 4

[0100] This embodiment provides a soft carbon and graphite composite anode material and its preparation method:

[0101] (1) Prepare a catalyst solution by mixing SDBS, ferric chloride, and water at a ratio of 0.03:2:1. Coat the catalyst solution onto particles with a particle size of D using mechanical force. V The surface of coal tar pitch-based raw coke powder with a thickness of 7 μm was 50. The mass ratio of catalyst solution to coke powder was 1:1. The mixture was first dried at 150℃ for 2 hours to obtain a mixture.

[0102] (2) The mixture described in step (1) is subjected to carbonization treatment at a temperature of 1300°C in a nitrogen atmosphere roller kiln, and then the carbonized material is cooled to room temperature to obtain carbonized material.

[0103] (3) The carbonized material described in step (2) is subjected to acid washing treatment with 1 mol / L hydrochloric acid solution and water washing treatment until neutral. After drying at 150°C for 2 hours, the composite negative electrode material of soft carbon and graphite is obtained.

[0104] The soft carbon and graphite composite anode material prepared in this embodiment has a hollow spherical graphite in it. Part of the graphite sphere is embedded in the soft carbon, and the other part is on the surface of the soft carbon. The XRD pattern of the composite anode material has a double peak feature at the (002) peak. The smaller 2θ peak is the (002) peak of the soft carbon, and the other is the (002) peak of the graphite. The peak intensity of the graphite (002) peak is H, and the peak intensity of the soft carbon (002) peak is h. The ratio of the two is r = H / h. The r value is shown in Table 1.

[0105] The XRD pattern of the soft carbon and graphite composite anode material prepared in this embodiment is shown in the figure below. Figure 9 As shown.

[0106] Example 5

[0107] This embodiment provides a soft carbon and graphite composite anode material and its preparation method:

[0108] (1) Prepare a catalyst solution by mixing SDBS, ferric chloride, and water at a ratio of 0.03:1:1. Coat the catalyst solution onto particles with a particle size of D using mechanical force. V The surface of coal tar pitch-based raw coke powder with a thickness of 10 μm was 50. The mass ratio of catalyst solution to coke powder was 2:1. The mixture was first dried at 150℃ for 2 hours to obtain a mixture.

[0109] (2) The mixture described in step (1) is subjected to carbonization treatment at a temperature of 1300°C in a nitrogen atmosphere roller kiln, and then the carbonized material is cooled to room temperature to obtain carbonized material.

[0110] (3) The carbonized material described in step (2) is subjected to acid washing treatment with 1 mol / L hydrochloric acid solution and water washing treatment until neutral. After drying at 150°C for 2 hours, the composite negative electrode material of soft carbon and graphite is obtained.

[0111] The soft carbon and graphite composite anode material prepared in this embodiment has a hollow spherical graphite in it. Part of the graphite sphere is embedded in the soft carbon, and the other part is on the surface of the soft carbon. The XRD pattern of the composite anode material has a double peak feature at the (002) peak. The smaller 2θ peak is the (002) peak of the soft carbon, and the other is the (002) peak of the graphite. The peak intensity of the graphite (002) peak is H, and the peak intensity of the soft carbon (002) peak is h. The ratio of the two is r = H / h. The r value is shown in Table 1.

[0112] The XRD pattern of the soft carbon and graphite composite anode material prepared in this embodiment is shown in the figure below. Figure 10 As shown. The single-point Raman spectrum of graphite in the composite anode material is as follows. Figure 11 As shown, the single-point Raman spectrum of soft carbon in the composite anode material is as follows. Figure 12 As shown.

[0113] Example 6

[0114] This embodiment provides a soft carbon and graphite composite anode material and its preparation method:

[0115] (1) Prepare a catalyst solution by mixing CMC, cobalt nitrate, and water at a ratio of 0.03:0.7:1. Coagulate the catalyst solution onto particles with a particle size of D using mechanical force. V The surface of coal tar pitch-based raw coke powder with a thickness of 3 μm was 50. The mass ratio of catalyst solution to coke powder was 0.6:1. The mixture was first dried at 150℃ for 2 hours to obtain a mixture.

[0116] (2) The mixture described in step (1) is subjected to carbonization treatment at a temperature of 1200°C in a nitrogen atmosphere roller kiln, and then the carbonized material is cooled to room temperature to obtain carbonized material.

[0117] (3) The carbonized material described in step (2) is subjected to acid washing treatment with 1 mol / L hydrochloric acid solution and water washing treatment until neutral. After drying at 150°C for 2 hours, the composite negative electrode material of soft carbon and graphite is obtained.

[0118] The soft carbon and graphite composite anode material prepared in this embodiment has a hollow spherical graphite in it. Part of the graphite sphere is embedded in the soft carbon, and the other part is on the surface of the soft carbon. The XRD pattern of the composite anode material has a double peak feature at the (002) peak. The smaller 2θ peak is the (002) peak of the soft carbon, and the other is the (002) peak of the graphite. The peak intensity of the graphite (002) peak is H, and the peak intensity of the soft carbon (002) peak is h. The ratio of the two is r = H / h. The r value is shown in Table 1.

[0119] The XRD pattern of the soft carbon and graphite composite anode material prepared in this embodiment is shown in the figure below. Figure 13 As shown.

[0120] Example 7

[0121] This embodiment provides a soft carbon and graphite composite anode material and its preparation method:

[0122] (1) Prepare a catalyst solution by mixing CTAB, cobalt sulfate, and water at a ratio of 0.05:1.5:1. Coagulate the catalyst solution onto particles with a particle size of D using mechanical force. V The surface of high-purity coal-based metallurgical coke powder with a thickness of 8 μm was 50. The mass ratio of catalyst solution to coke powder was 1:1. The mixture was first dried at 150℃ for 2 hours to obtain a mixture.

[0123] (2) The mixture described in step (1) is subjected to carbonization treatment at a temperature of 1300°C in a nitrogen atmosphere roller kiln, and then the carbonized material is cooled to room temperature to obtain carbonized material.

[0124] (3) The carbonized material described in step (2) is subjected to acid washing treatment with 1 mol / L hydrochloric acid solution and water washing treatment until neutral. After drying at 150°C for 2 hours, the composite negative electrode material of soft carbon and graphite is obtained.

[0125] The soft carbon and graphite composite anode material prepared in this embodiment has a hollow spherical graphite in it. Part of the graphite sphere is embedded in the soft carbon, and the other part is on the surface of the soft carbon. The XRD pattern of the composite anode material has a double peak feature at the (002) peak. The smaller 2θ peak is the (002) peak of the soft carbon, and the other is the (002) peak of the graphite. The peak intensity of the graphite (002) peak is H, and the peak intensity of the soft carbon (002) peak is h. The ratio of the two is r = H / h. The r value is shown in Table 1.

[0126] The XRD pattern of the soft carbon and graphite composite anode material prepared in this embodiment is shown in the figure below. Figure 14 As shown.

[0127] Example 8

[0128] This embodiment provides a soft carbon and graphite composite anode material and its preparation method:

[0129] (1) Prepare a catalyst solution by mixing PAM, ferric sulfate, and water at a ratio of 0.05:1:1. Coat the catalyst solution onto particles with a particle size of D using mechanical force. V The surface of high-purity coal-based metallurgical coke powder with a thickness of 28 μm was 50. The mass ratio of catalyst solution to coke powder was 1:1. The mixture was first dried at 150℃ for 2 hours to obtain a mixture.

[0130] (2) The mixture described in step (1) is subjected to carbonization treatment at a temperature of 1100°C in a nitrogen atmosphere roller kiln, and then the carbonized material is cooled to room temperature to obtain carbonized material.

[0131] (3) The carbonized material described in step (2) is subjected to acid washing treatment with 1 mol / L hydrochloric acid solution and water washing treatment until neutral. After drying at 150°C for 2 hours, the composite negative electrode material of soft carbon and graphite is obtained.

[0132] The soft carbon and graphite composite anode material prepared in this embodiment has a hollow spherical graphite in it. Part of the graphite sphere is embedded in the soft carbon, and the other part is on the surface of the soft carbon. The XRD pattern of the composite anode material has a double peak feature at the (002) peak. The smaller 2θ peak is the (002) peak of the soft carbon, and the other is the (002) peak of the graphite. The peak intensity of the graphite (002) peak is H, and the peak intensity of the soft carbon (002) peak is h. The ratio of the two is r = H / h. The r value is shown in Table 1.

[0133] The XRD pattern of the soft carbon and graphite composite anode material prepared in this embodiment is shown in the figure below. Figure 15 As shown.

[0134] Example 9

[0135] Except for the absence of PEG additives during catalyst solution preparation, all other conditions in this embodiment are the same as in Example 1. The XRD pattern of the soft carbon and graphite composite anode material prepared in this embodiment is shown below. Figure 16 As shown.

[0136] Example 10

[0137] In this embodiment, all conditions are the same as in Example 1, except that the carbonization temperature in step (2) is replaced with 900℃. The XRD pattern of the soft carbon and graphite composite material prepared in this embodiment is shown below. Figure 17 As shown.

[0138] Comparative Example 1

[0139] The conditions for this comparative example were the same as in Example 1, except that no catalyst solution was prepared. The XRD pattern of the soft carbon prepared in this comparative example is shown below. Figure 18 As shown.

[0140] Comparative Example 2

[0141] The conditions for this comparative example were the same as in Example 2, except that no catalyst solution was prepared. The XRD pattern of the soft carbon prepared in this comparative example is shown below. Figure 19 As shown, the cross-sectional morphology of the soft carbon anode material after argon ion milling is illustrated by SEM. Figure 20 As shown, the particles are densely packed inside.

[0142] Comparative Example 3

[0143] This comparative example provides a method for preparing a composite anode material that physically mixes soft carbon and graphite:

[0144] (1) The particle size D V 50 10μm petroleum asphalt-based raw coke powder was carbonized in a nitrogen atmosphere roller kiln at a carbonization temperature of 1100℃. The carbonized material was then cooled to room temperature to obtain carbonized material A.

[0145] (2) The particle size D V 50 10μm petroleum pitch-based raw coke powder was graphitized in a graphitization furnace at a graphitization temperature of 2900℃, and then the material was cooled to room temperature to obtain graphite material B.

[0146] (3) The carbon material A and the graphite material B are mixed evenly in a mixer to obtain the soft carbon and graphite composite negative electrode material C, with the mass ratio of A to B being 1:1.

[0147] The XRD pattern of the composite anode material in this comparative example is shown below. Figure 21 As shown.

[0148] The negative electrode materials provided in Examples 1-10 and Comparative Examples 1-3 were tested, and the test results are shown in Table 1. The tests included:

[0149] (1) XRD pattern scanning was performed on the composite negative electrode sample. The X-ray diffractometer used a copper target with a wavelength of 0.154056 nm and a scanning speed of approximately 4° / min. Spectral information, such as the full width at half maximum (FWHM) and 2θ corresponding to the (002) peak, and the interlayer spacing (d) were obtained using analysis software such as HighScore Plus and Jade. 002 ) etc. The 2θ corresponding to the (002) peak of soft carbon is represented by 2θ. S This indicates that the 2θ corresponding to the (002) peak of graphite is represented by 2θ. G The full width at half maximum (FWHM) of the soft carbon (002) peak is indicated using FWHM. S The full width at half maximum (FWHM) of the graphite (002) peak is indicated by FWHM. G The interlayer spacing of soft carbon is represented by Sd. 002 The interlayer spacing of graphite is represented by Gd. 002The difference between the 2θ peak corresponding to the (002) peak of graphite and the 2θ peak corresponding to the (002) peak of soft carbon is represented by 2θ. G -2θ S The degree of graphitization of graphite is represented by g and calculated using the Mering-Maire formula: g = (0.3440 - d) / (2π) 002 ) / (0.3440-0.3354)×100%;

[0150] (2) The morphology of the composite negative electrode material was observed by scanning electron microscopy;

[0151] (3) Adhering to the principle of not damaging or ablating the sample, a scanning electron microscope combined with a laser Raman spectrometer was used to perform micro-area analysis on the composite negative electrode material. The laser wavelength was 532 nm. Laser Raman spectroscopy tests were performed on the surface of graphite micro-areas and soft carbon micro-areas, respectively. The obtained Raman spectra were analyzed, and Rs = I D / I G Or R G =I D / I G I D I represents the peak intensity value of peak D. G The peak intensity of peak G is given, and the Raman shift of peak D is at 1350 cm⁻¹. -1 Nearby, the Raman shift of peak G is at 1580 cm⁻¹. -1 Nearby; R S R G The results are shown as laser Raman test results for soft carbon and graphite, respectively. To facilitate observation and differentiation between soft carbon and graphite, the composite particles to be analyzed were first selected using SEM. Then, the sample area was scanned using Raman 2D imaging, i.e., the Raman area scanning function. This area is actually composed of 400 single-point Raman spectra. The instrument's built-in function calculates the R values ​​of the above 400 single-point laser Raman spectra and obtains a color cloud map of the distribution of R values ​​in the measured area. Color bars are used on the right side of the cloud map to represent the R values ​​represented by different colors in the cloud map.

[0152] (4) Argon ion beam cutting and polishing were performed on the composite negative electrode material to prepare samples, and the internal structure of graphite and soft carbon was observed by scanning electron microscopy.

[0153] (5) Electrochemical performance testing: The composite anode materials provided in Examples 1-10 and Comparative Examples 1-3 were prepared by slurry preparation according to the ratio of composite anode material:CMC:SP:SBR = 93.5:1.5:2:3, followed by coating, drying, and rolling to obtain anode sheets, thereby preparing CR2430 type coin cell half-cells with lithium metal sheets as the counter electrode. The capacity, first efficiency, and rate performance of the composite anode materials were tested. The coin cell half-cell was discharged to 0.005V at 0.1C, allowed to stand for 10 min, discharged to 0.005V at 0.01C, allowed to stand for 10 min, and then charged to 2V at 0.1C to end the test. The first lithium insertion capacity and the first lithium extraction capacity were obtained respectively. The ratio of the first lithium extraction capacity to the first lithium insertion capacity is the first coulombic efficiency, i.e., the first efficiency. The lithium intercalation capacity under 0.2C and 2C conditions was obtained by discharging to 0.01V at 0.2C, discharging to 0.01C at 0.01V constant voltage, and letting it stand for 10s; charging to 1.5V at 0.2C, letting it stand for 10s, discharging to 0.01V at 2C, discharging to 0.01C at 0.01V constant voltage, and charging to 1.5V at 2C.

[0154] Table 1

[0155]

[0156]

[0157] As shown in the tables above, Examples 1-10 demonstrate that increasing the catalyst ratio and carbonization temperature leads to an increase in the r-value, capacity, first-efficiency, and kinetic performance of the prepared composite anode. Furthermore, the SEM image in Example 1 shows that graphite is uniformly dispersed within the soft carbon particles, and the graphite particles are observed to be spherically embedded within them. This is due to the catalyst catalytically converting a portion of the soft carbon into graphite. The uniform dispersion of the catalyst on the soft carbon surface results in the uniform dispersion and embedding of graphite spheres within the soft carbon surface. The R-value cloud map obtained by combining SEM and Raman spectroscopy in Example 1 allows for rapid differentiation between the soft carbon and graphite regions, further indicating that graphite is uniformly dispersed on the soft carbon surface.

[0158] The data from Examples 1 and 9 show that the absence of a dispersant in the catalyst solution leads to uneven catalyst dispersion, which prevents effective utilization of the catalyst and is detrimental to the improvement of the capacity, first-efficiency, and kinetic performance of the composite anode material.

[0159] The data from Examples 1 and 10 show that when the heat treatment temperature is too low, the catalyst cannot effectively catalytically convert soft carbon into hollow graphite spheres, resulting in lower capacity, lower initial efficiency, and poorer kinetic performance of the composite anode material.

[0160] A comparison of the data results from Example 1 and Comparative Examples 1-2 shows that without the addition of a catalyst, the conversion of graphite cannot be achieved at the carbonization temperature, and the capacity, first efficiency, and kinetic performance of the composite anode material are significantly reduced. This indicates that the addition of a catalyst is a necessary condition for converting a portion of the soft carbon into hollow graphite spheres.

[0161] The data from Example 1 and Comparative Example 3 show that the conventional soft carbon and graphite composite anode material has poorer capacity and kinetic performance compared with the soft carbon and graphite composite anode material prepared in this invention.

[0162] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A composite anode material of soft carbon and graphite, characterized in that, The composite negative electrode material includes soft carbon and graphite spheres dispersed on the surface of the soft carbon, with a portion of the graphite spheres embedded inside the soft carbon. The preparation method of the composite anode material of soft carbon and graphite includes the following steps: (1) The catalyst solution is coated on the surface of the carbon material and dried to obtain a mixture; (2) The mixture described in step (1) is subjected to carbonization treatment to obtain carbonized material; (3) The carbonized material described in step (2) is subjected to acid washing and water washing in sequence, and after a second drying, the composite negative electrode material of soft carbon and graphite is obtained. The method for preparing the catalyst solution in step (1) includes: mixing a dispersant, salt, and water to obtain the catalyst solution; The mass ratio of the dispersant, salt, and water is (0.03~0.1):(0.7~2):1; The salts include organic or inorganic salts of vanadium, chromium, manganese, iron, cobalt, nickel, or copper.

2. The composite negative electrode material according to claim 1, characterized in that, The diameter of the graphite spheres is 0.01~10 μm.

3. The composite negative electrode material according to claim 1, characterized in that, The graphite spheres are hollow.

4. The composite negative electrode material according to claim 1, characterized in that, The XRD pattern of the composite anode material has two peaks, which are a soft carbon peak and a graphite peak. The peak intensity value at the apex of the soft carbon peak is h, and the peak intensity value at the apex of the graphite peak is H, where r = H / h, 0 <r≤12。 5. The composite negative electrode material according to claim 1, characterized in that, The particle size D of the carbon material in step (1) V 50 is 3~30µm.

6. The composite negative electrode material according to claim 1, characterized in that, The mass ratio of the catalyst solution to the carbon material in step (1) is (0.5~2):

1.

7. The composite negative electrode material according to claim 1, characterized in that, The atmosphere for the carbonization process in step (2) includes any one or a combination of at least two of nitrogen, argon, or helium.

8. The composite negative electrode material according to claim 1, characterized in that, The carbonization process is carried out at a temperature of 1100~1300℃.

9. The composite negative electrode material according to claim 1, characterized in that, The carbonized material is obtained by cooling after carbonization treatment in step (2).

10. The composite negative electrode material according to claim 1, characterized in that, The acid solution used in the acid washing process in step (3) includes hydrochloric acid; The concentration of the acid solution is 0.8~1.2 mol / L.

11. The composite negative electrode material according to claim 1, characterized in that, The preparation method includes the following steps: (1) The catalyst solution is coated on the surface of the carbon material and dried at 120~170℃ for 1.5~2.5h to obtain a mixture; (2) The mixture described in step (1) is subjected to carbonization treatment at a temperature of 1100~1300℃ to obtain carbonized material; (3) The carbonized material described in step (2) is subjected to acid washing treatment and water washing treatment with a concentration of 0.8~1.2mol / L in sequence, and then dried for 1.5~2.5h at a temperature of 120~170℃ to obtain the composite negative electrode material of soft carbon and graphite.

12. A lithium-ion battery, characterized in that, The lithium-ion battery includes a positive electrode material and a negative electrode material, wherein the negative electrode material includes a composite negative electrode material of soft carbon and graphite as described in any one of claims 1-11.

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