Performance-adjustable lithium battery negative electrode material co-production silicon-carbon negative electrode material and preparation method thereof

Abstract

The preparation method comprises the following steps: carrying out distillation treatment on coal tar, and then carrying out solid-liquid separation treatment; extracting and separating the heavy oil centrifugate to obtain a soluble phase and an insoluble phase, recovering the soluble phase through a solvent, distilling to obtain purified heavy oil, and carbonizing to obtain an artificial graphite precursor; the precursor is respectively subjected to graphitization treatment and granulation treatment to obtain capacity type and rate type lithium battery negative electrode materials; drying, activating, oxidizing, stabilizing and carbonizing the insoluble phase, mixing with silicon powder, grinding, mixing with coated asphalt, coating to obtain a silicon-carbon negative electrode precursor, and roasting to obtain the core-shell type silicon-carbon negative electrode material. The negative electrode material is mixed with capacity type and rate type lithium battery negative electrode materials. The preparation method has the advantages that the performance-adjustable negative electrode material is provided, capacity type and rate type lithium battery negative electrode materials, core-shell type silicon-carbon negative electrode materials and various raw material oils are co-produced, the preparation process is simple, and the cost is relatively low.

Description

Technical Field

[0001] The present invention belongs to the technical field of silicon-carbon negative electrode materials, and in particular relates to a performance-adjustable lithium battery negative electrode material co-produced with silicon-carbon negative electrode materials and a preparation method thereof. Background Art

[0002] With the development of society and technology, and the need for more multifunctional products, people are placing increasingly higher demands on lithium-ion batteries for battery life, safety, and fast charging performance. Electrode materials are a core factor in determining lithium-ion battery performance and a major factor affecting their cost.

[0003] Lithium battery anode materials are mainly divided into carbon-based materials and non-carbon-based materials. Carbon-based materials include natural graphite anodes, artificial graphite anodes, mesocarbon microbeads (MCMB), soft carbon (such as coke) anodes, hard carbon anodes, carbon nanotubes, graphene, and carbon fibers. Non-carbon-based materials are mainly divided into silicon-based and its composite materials, nitride anodes, tin-based materials, lithium titanate, and alloy materials.

[0004] In lithium-ion batteries, the anode material acts as a carrier of lithium ions and electrons during the charging process, responsible for energy storage and release. This material accounts for approximately 8% of the battery's manufacturing cost. Currently, graphite is the primary commercial anode material, and the theoretical specific capacity of graphite-based anodes in lithium-ion batteries is only 372 mAh / g. The actual specific capacity of commercial high-end graphite materials is 360-365 mAh / g, which is very close to its theoretical specific capacity. Improving and perfecting graphite anode materials has very limited potential to increase the energy density of lithium-ion batteries. Silicon (Si) is considered one of the most promising anode materials for lithium-ion batteries. Elemental Si has a theoretical specific capacity of 3579 mAh / g at room temperature, making it a lithium-ion battery anode material with an extremely high theoretical specific capacity.

[0005] Currently, commercialized silicon-based anode materials primarily include carbon-coated silicon oxide, nano-silicon carbon, silicon nanowires, and amorphous silicon alloys. Carbon-coated silicon oxide and nano-silicon carbon are the most commercially successful, both doped with graphite at a specific ratio (5%-10%). In recent years, silicon-based anodes have gradually moved toward industrial production, but this has been relatively recent, and relatively few companies are capable of mass production.

[0006] Silicon-based anode materials are primarily composed of silicon and graphite. Silicon offers significant advantages as a lithium-ion battery anode material. First, silicon alloys with lithium at room temperature, achieving a theoretical specific capacity of 4200 mAh / g, over ten times that of current graphite-based anode materials. Second, compared to graphite, silicon is abundant and widely distributed in the Earth's crust, comprising 25.8% of its mass, making it the second most abundant element in the crust. Third, silicon has a slightly higher potential plateau than graphite (approximately 0.4V, Li / Li+), eliminating the risk of lithium plating and enhancing safety. Fourth, silicon-based anode materials offer superior low-temperature performance compared to graphite. Fifth, they provide channels for lithium ion insertion and extraction from various directions, resulting in excellent fast-charging performance. Silicon anodes are expected to become an ideal alternative to graphite anodes. Summary of the Invention

[0007] In order to overcome the shortcomings of the existing technology, the purpose of the present invention is to provide a performance-adjustable lithium battery negative electrode material that co-produces silicon-carbon negative electrode material and a preparation method. The performance-adjustable lithium battery negative electrode material has a high initial efficiency, excellent cycle performance, and a low volume expansion rate. During the preparation process, capacity-type negative electrode materials, rate-type negative electrode materials, core-shell silicon-carbon negative electrode materials and a variety of high-quality raw material oils are co-produced, thereby reducing the production cost of deep processing of coal tar.

[0008] To achieve the above object, the present invention is implemented through the following technical solutions:

[0009] A method for preparing a lithium battery negative electrode material with adjustable performance and co-producing a silicon-carbon negative electrode material comprises the following steps:

[0010] 1) Distilling coal tar to remove light oil and obtain coal tar heavy oil;

[0011] 2) performing solid-liquid separation on the coal tar heavy oil to obtain heavy oil residue and heavy oil centrifuge liquid;

[0012] 3) The heavy oil centrifuge liquid is mixed with an extractant, and subjected to extraction and separation treatment to obtain a soluble phase and an insoluble phase, respectively. The soluble phase is recovered by solvent and distilled to obtain purified heavy oil;

[0013] 4) Carbonizing the purified heavy oil to obtain an artificial graphite precursor;

[0014] 5) The artificial graphite precursor is graphitized to obtain a capacity-type lithium battery negative electrode material; the artificial graphite precursor is granulated to obtain a rate-type lithium battery negative electrode material;

[0015] 6) The insoluble phase obtained in step 3) is sequentially dried, activated, oxidatively stabilized, and carbonized, and then mixed with silicon powder, ground, and then mixed with coated asphalt, and a silicon-carbon negative electrode precursor is obtained by coating;

[0016] 7) The silicon-carbon anode precursor is calcined to obtain a core-shell silicon-carbon anode material;

[0017] 8) The core-shell silicon-carbon negative electrode material is mixed with the capacity-type lithium battery negative electrode material and the rate-type lithium battery negative electrode material obtained in step 5) to obtain a lithium battery negative electrode material with adjustable gram-specific capacity, first efficiency and rate.

[0018] In step 1), the coal tar is high-temperature coal tar, and the quinoline insoluble matter content is 1% to 15%;

[0019] The reaction conditions of the distillation treatment are: the tower bottom temperature is controlled at 250-360°C, the tower top temperature is controlled at 100-240°C, and the vacuum degree is controlled at 0.01-0.09 MPa;

[0020] The light oil is the front distillate oil with a temperature of 260-320°C in high-temperature coal tar;

[0021] The quinoline insoluble matter content in the coal tar heavy oil is 1% to 20%, and the density is 1.13 to 1.3 g / cm 3 .

[0022] In step 2), the reaction conditions of the solid-liquid separation treatment are: separation temperature 60-150° C., separation time 0.5-10 h, centrifugal speed 800-2000 rad / min, and sieve mesh size 100-900 mesh;

[0023] The content of quinoline insoluble matter in the heavy oil centrifuge liquid is 0-0.1%.

[0024] In step 3), the extractant is one or a mixture of two or more of acetone, benzene, toluene, xylene, pyridine, and quinoline;

[0025] The mass ratio of the extractant to the heavy oil centrifuge liquid is (1-5):1;

[0026] The reaction conditions of the extraction and separation treatment are: extraction temperature 20-150° C., extraction time 0.5-10 h, and sieve mesh size 300-1200 mesh;

[0027] The reaction conditions for the solvent recovery are: gas phase temperature of 60-160° C., kettle bottom temperature of 100-280° C., vacuum degree of 0.01-0.09 MPa, and residence time of 0.5-2 h.

[0028] The reaction conditions of the distillation are: gas phase temperature of 160-280° C., kettle bottom temperature of 320-380° C., vacuum degree of 0.01-0.06 MPa, and residence time of 2-4 h.

[0029] The purified heavy oil has a quinoline insoluble matter content of 0-0.01%, an ash content of <0.05%, and a density of 1.05-1.2 g / cm 3 , the fraction before 300℃ is ≤10%.

[0030] In step 4), the carbonization reaction conditions are: under nitrogen protection, a nitrogen flow rate of 300-1200 ml / min, a heating rate of 1-10°C / min, a carbonization final temperature of 700-2000°C, and a final temperature constant time of 1-20 hours;

[0031] The indicators of the artificial graphite precursor are: mesophase content ≥85%, ash content ≤0.01%.

[0032] In step 5), the reaction conditions of the graphitization treatment are: under argon protection, a heating rate of 1-20°C / min, a final graphitization temperature of 2500-3000°C, and a final temperature holding time of 1-10 hours;

[0033] The granulation process comprises: adding coating asphalt to the artificial graphite precursor, wherein the coating asphalt addition ratio is 5wt% to 15wt%, the reaction temperature is 600 to 900°C, and the reaction time is 2 to 10 hours;

[0034] The index of the capacity type lithium battery negative electrode material is: D 10 :6~15μm, D 50 :15~24μm, D 90 ≤40.0μm, D max ≤50.0μm, specific surface area 0.9~2.0m 2 / g, tap density ≥0.92g / cm 3 , fixed carbon content ≥99.9%, graphitization degree ≥94.0%, first discharge specific capacity ≥372.0mAh / g, first coulombic efficiency ≥90%;

[0035] The index of the rate-type lithium battery negative electrode material is: D 10 :6~15μm, D 50 :15~24μm, D 90 ≤40.0μm, D max ≤50.0μm, specific surface area 0.9~2.0m 2 / g, tap density ≥0.92g / cm 3 , fixed carbon content ≥99.9%, graphitization degree ≥94.0%, first discharge specific capacity ≥340.0mAh / g, and cycle retention rate ≥80% after 600 cycles at 3C rate.

[0036] In step 6), the toluene insoluble matter content in the insoluble phase is 40% to 90%, and the ash content is less than 0.05%;

[0037] The drying conditions are as follows: drying temperature is 160-320°C, and drying time is 0.5-5h;

[0038] The activation reaction conditions are as follows: the activation reaction temperature is 500-1000°C, the reaction atmosphere is one of oxygen, air, and carbon dioxide, the flow rate is 60-300 L / h, and the activation time is 0.5-15h;

[0039] The reaction conditions of the oxidation stabilization are: air temperature of 160-340°C, air flow of 1-10m 3 / h, processing time is 1~5h;

[0040] The carbonization reaction conditions are as follows: under nitrogen protection, a nitrogen flow rate of 300-1200 ml / min, a heating rate of 1-10°C / min, a carbonization final temperature of 700-2000°C, and a final temperature constant time of 1-20h;

[0041] The particle size D of the silicon powder 50 The particle size is 0.1~200nm; the silicon powder accounts for 1%~20% of the mass of the insoluble phase after treatment;

[0042] The grinding process comprises: stirring at a speed of 100 to 3000 rad / min for 1 to 20 hours;

[0043] The coating asphalt has a softening point of 110-280° C. and a coking value of 20-80; the coating asphalt accounts for 5%-20% of the mass of the mixture of silicon powder and the treated insoluble phase;

[0044] The reaction conditions of the coating treatment are: under 0.1-0.5 L / min nitrogen protection, heating rate of 2-10°C / min, final temperature of 360-650°C, time of 1-8 hours, and converter frequency of 20-80 Hz;

[0045] The indicators of the silicon-carbon negative electrode precursor are: specific surface area: 0.7~3m 2 / g, tap density: 0.6~1.15g / cm 3 , ash content <0.05%.

[0046] In step 7), the reaction conditions of the calcination treatment are: under nitrogen protection, a nitrogen flow rate of 300-1200 ml / min, a heating rate of 1-10°C / min, a final calcination temperature of 700-1200°C, and a final temperature hold time of 1-30 hours;

[0047] The core-shell silicon-carbon negative electrode material has the following indexes: particle size distribution D 10 :6~12μm、D 50 :15~24μm、D90 : 28~45μm, true density ≥2.24g / cm 3 , tap density ≥0.9g / cm 3 , the powder compaction density is ≥1.55g / cm 3 , ash content ≤ 0.01%, first coulombic efficiency ≥ 80%, first discharge specific capacity ≥ 450mAh / g, 100 times 0.1C cycle capacity retention rate ≥ 80%, cycle performance ≥ 400 cycles, rate performance 2C / 0.2C ≥ 80%.

[0048] In step 8), the core-shell silicon-carbon negative electrode material, the capacity-type lithium battery negative electrode material, and the rate-type lithium battery negative electrode material are mixed in a mass ratio of 10:(1-20):(1-10).

[0049] A performance-adjustable lithium battery negative electrode material co-produced with a silicon-carbon negative electrode material, wherein the performance-adjustable lithium battery negative electrode material has the following indicators: ash content ≤ 0.01%, first discharge specific capacity ≥ 400 mAh / g, first coulombic efficiency ≥ 85%, 100 0.2C cycle capacity retention rate ≥ 80%, cycle performance ≥ 400 cycles, and rate performance 2C / 0.2C ≥ 80%.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] 1. The performance of the lithium battery negative electrode material of the present invention is adjustable, with high initial efficiency, excellent cycle performance, and low volume expansion rate. Its indicators are: ash content ≤ 0.01%, specific surface area ≤ 1.8m 2 / g, first discharge specific capacity ≥400mAh / g, first coulombic efficiency ≥85%, 100 times 0.2C cycle capacity retention rate ≥80%, cycle performance ≥400 cycles, rate performance (2C / 0.2C) ≥80%.

[0052] 2. The present invention not only provides excellent performance-adjustable negative electrode material products for the lithium battery field, but also co-produces capacity-type lithium battery negative electrode materials, rate-type lithium battery negative electrode materials, core-shell silicon-carbon negative electrode materials and a variety of high-quality raw oils. Among them, the capacity-type lithium battery negative electrode material can be used as the main raw material for high-capacity lithium battery negative electrode materials, and its indicators are: D 10 :6~15μm, D 50 :15~24μm, D 90 ≤40.0μm, D max ≤50.0μm, specific surface area: 0.9~2.0m 2 / g, tap density ≥0.92g / cm 3, fixed carbon content ≥ 99.9%, graphitization degree ≥ 94.0%, first discharge specific capacity ≥ 372.0mAh / g, first coulombic efficiency ≥ 90%. Rate-type lithium battery negative electrode materials can be used as the main raw materials for high-rate lithium battery negative electrode materials. Its indicators are: D 10 :6~15μm, D 50 :15~24μm, D 90 ≤40.0μm, D max ≤50.0μm, specific surface area: 0.9~2.0m 2 / g, tap density ≥0.92g / cm 3 , fixed carbon content ≥ 99.9%, graphitization degree ≥ 94.0%, first discharge specific capacity ≥ 340.0mAh / g, cycle retention rate ≥ 80% after 600 cycles at 3C rate. Core-shell silicon-carbon negative electrode materials can be used as the main raw materials for silicon-carbon negative electrode materials with low volume expansion rate and high / super capacity. Its indicators are: particle size distribution D 10 :6~12μm、D 50 :15~24μm、D 90 : 28~45μm, true density ≥2.24g / cm 3 , tap density ≥0.9g / cm 3 , the powder compaction density is ≥1.55g / cm 3 , ash content ≤ 0.01%, specific surface area ≤ 1.8m 2 / g, first coulombic efficiency ≥80%, first discharge specific capacity ≥450mAh / g, 100 times 0.1C cycle capacity retention rate ≥80%, cycle performance ≥400 cycles, rate performance (2C / 0.2C) ≥80%. Purified heavy oil can be used as raw material for the production of coal-based spinnable asphalt, mesophase asphalt and needle coke; heavy oil residue can be used as asphalt additive for modified asphalt and adhesive. The indicators of purified heavy oil are: quinoline insoluble matter content of 0~0.01%, ash content <0.05%, and density (20℃) of 0.95~1.3g / cm 3 , the fraction before 300℃ is ≤10%.

[0053] 3. The present invention not only provides excellent performance-adjustable negative electrode material products for the lithium battery field, but also co-produces capacity-type negative electrode materials, rate-type negative electrode materials, core-shell silicon-carbon negative electrode materials and a variety of high-quality raw oils. The preparation process is simple, the manufacturing cost is low, and it is safe, reliable and pollution-free. It reduces the production cost of deep processing of coal tar, improves the comprehensive competitiveness of lithium battery negative electrode material products and silicon-carbon negative electrode material products, and solves the problem of efficient and high value-added utilization of coal tar. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 It is the charge and discharge curve of the performance-adjustable lithium battery negative electrode material.

[0055] Figure 2 It is a cycle curve diagram of lithium battery negative electrode materials with adjustable performance.

[0056] Figure 3 This is a scanning electron microscope structure diagram of the core-shell silicon-carbon negative electrode material.

[0057] Figure 4 This is a polarized microstructure diagram of the core-shell silicon-carbon negative electrode material. DETAILED DESCRIPTION

[0058] The present invention will be described in detail below, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0059] A method for preparing a lithium battery negative electrode material with adjustable performance and co-producing a silicon-carbon negative electrode material comprises the following steps:

[0060] 1) Coal tar is distilled to remove light oil and obtain coal tar heavy oil.

[0061] The coal tar is high-temperature coal tar, and the quinoline insoluble content is 1% to 15%. The reaction conditions for the distillation treatment are: the tower bottom temperature is controlled at 250 to 360°C, the tower top temperature is controlled at 100 to 240°C, and the vacuum degree is controlled at 0.01 to 0.09 MPa. The light oil is the front distillate oil at 260 to 320°C in the high-temperature coal tar. The quinoline insoluble content of the obtained coal tar heavy oil is 1% to 20%, and the density (20°C) is 1.13 to 1.3 g / cm 3 .

[0062] 2) performing solid-liquid separation on the coal tar heavy oil to obtain heavy oil residue and heavy oil centrifuge liquid;

[0063] The solid-liquid separation process is carried out under the following conditions: a separation temperature of 60-150°C, a separation time of 0.5-10 hours, a centrifugal speed of 800-2000 rad / min, and a screen size of 100-900 mesh. The resulting heavy oil centrifuge contains 0-0.1% quinoline-insoluble matter. The resulting heavy oil residue can be used as an asphalt additive for modified asphalt and binders.

[0064] 3) The heavy oil centrifuge liquid is mixed with an extractant and subjected to extraction separation to obtain a soluble phase and an insoluble phase, respectively. The soluble phase is recovered through solvent recovery and distillation to obtain purified heavy oil. The purified heavy oil can be used as a feedstock for the production of coal-based spinnable pitch, mesophase pitch, or needle coke.

[0065] The reaction conditions for the extraction and separation treatment are as follows: extraction temperature 20-150°C, extraction time 0.5-10 hours, mesh size 300-1200 mesh; the extractant is one or a mixture of two or more of acetone, benzene, toluene, xylene, pyridine, and quinoline; the mass ratio of the extractant to the heavy oil centrifuge liquid is (1-5):1;

[0066] The reaction conditions for solvent recovery are: gas phase temperature 60-160°C, kettle bottom temperature 100-280°C, vacuum degree 0.01-0.09 MPa, and residence time 0.5-2 h.

[0067] The reaction conditions of distillation are: gas phase temperature 160-280°C, kettle bottom temperature 320-380°C, vacuum degree 0.01-0.06 MPa, and residence time 2-4 h.

[0068] The purified heavy oil has a quinoline insoluble content of 0-0.01%, an ash content of <0.05%, and a density (20°C) of 1.05-1.2 g / cm 3 , 300℃ front fraction ≤10%. Purified heavy oil can be used as raw material for producing coal-based spinnable pitch, mesophase pitch and needle coke.

[0069] 4) Carbonizing the purified heavy oil to obtain an artificial graphite precursor. The carbonization reaction conditions are: under nitrogen protection, a nitrogen flow rate of 300-1200 ml / min, a heating rate of 1-10°C / min, a final carbonization temperature of 700-2000°C, and a holding time of 1-20 hours. The obtained artificial graphite precursor has the following specifications: mesophase content ≥85% and ash content ≤0.01%.

[0070] 5) The artificial graphite precursor is graphitized to obtain a capacity-type lithium battery negative electrode material; the artificial graphite precursor is granulated to obtain a rate-type lithium battery negative electrode material.

[0071] The reaction conditions of graphitization treatment are: under argon protection, heating rate 1~20℃ / min, final graphitization temperature 2500~3000℃, and final temperature constant time 1~10h; granulation treatment is: adding coated asphalt to the artificial graphite precursor, the coating asphalt addition ratio is 5wt%~15wt%, reaction temperature 600~900℃, and reaction time 2~10h.

[0072] The index of the obtained capacity type lithium battery negative electrode material is: D 10 :6~15μm, D 50 :15~24μm, D 90 ≤40.0μm, D max ≤50.0μm, specific surface area 0.9~2.0m 2 / g, tap density ≥0.92g / cm 3, fixed carbon content ≥99.9%, graphitization degree ≥94.0%, first discharge specific capacity ≥372.0mAh / g, first coulombic efficiency ≥90%.

[0073] The index of the obtained rate-type lithium battery negative electrode material is: D 10 :6~15μm, D 50 :15~24μm, D 90 ≤40.0μm, D max ≤50.0μm, specific surface area 0.9~2.0m 2 / g, tap density ≥0.92g / cm 3 , fixed carbon content ≥99.9%, graphitization degree ≥94.0%, first discharge specific capacity ≥340.0mAh / g, and cycle retention rate ≥80% after 600 cycles at 3C rate.

[0074] 6) The insoluble phase obtained in step 3) is dried, activated, oxidatively stabilized, and carbonized in sequence, and then mixed with silicon powder. After grinding, the mixture is mixed with coated asphalt, and a silicon-carbon negative electrode precursor is obtained through coating.

[0075] Among them, the content of toluene insoluble matter in the insoluble phase is 40%~90%, and the ash content is <0.05%. The drying conditions are: drying temperature is 160~320℃, and drying time is 0.5~5h. The activation reaction conditions are: activation reaction temperature is 500~1000℃, reaction atmosphere is one of oxygen, air, and carbon dioxide, flow rate is 60~300L / h, and activation time is 0.5~15h. The reaction conditions of oxidation stabilization are: air temperature is 160~340℃, air flow rate is 1~10m 3 / h, the treatment time is 1~5h. The reaction conditions of carbonization are: under nitrogen protection, nitrogen flow rate is 300~1200ml / min, heating rate is 1~10℃ / min, carbonization final temperature is 700~2000℃, and final temperature constant time is 1~20h. 50 The particle size is 0.1~200nm; silicon powder accounts for 1%~20% of the mass of the insoluble phase after treatment. The grinding treatment is: stirring at a speed of 100~3000rad / min, and the stirring time is 1~20h. The softening point of the coated asphalt is 110~280℃, and the coking value is 20~80; the coated asphalt accounts for 5%~20% of the mass of the mixture of silicon powder and the insoluble phase after treatment. The reaction conditions of the coating treatment are: under 0.1~0.5L / min nitrogen protection, the heating rate is 2~10℃ / min, the final temperature is 360~650℃, the time is 1~8h, and the converter frequency is 20~80Hz. The indicators of the obtained silicon-carbon negative electrode precursor are: specific surface area: 0.7~3m 2 / g, tap density: 0.6~1.15g / cm 3, ash content <0.05%.

[0076] 7) The silicon-carbon anode precursor is calcined to obtain a core-shell silicon-carbon anode material. The calcination reaction conditions are: under nitrogen protection, a nitrogen flow rate of 300-1200 ml / min, a heating rate of 1-10°C / min, a final calcination temperature of 700-1200°C, and a final temperature hold time of 1-30 hours. Figure 3 、 Figure 4 The index of the core-shell silicon-carbon negative electrode material obtained is: particle size distribution is D 10 :6~12μm、D 50 :15~24μm、D 90 : 28~45μm, true density ≥2.24g / cm 3 , tap density ≥0.9g / cm 3 , the powder compaction density is ≥1.55g / cm 3 , ash content ≤ 0.01%, first coulombic efficiency ≥ 80%, first discharge specific capacity ≥ 450mAh / g, 100 times 0.1C cycle capacity retention rate ≥ 80%, cycle performance ≥ 400 cycles, rate performance (2C / 0.2C) ≥ 80%.

[0077] 8) The core-shell silicon-carbon negative electrode material is mixed with the capacity-type lithium battery negative electrode material and the rate-type lithium battery negative electrode material obtained in step 5) in a mass ratio of 10:(1-20):(1-10) to obtain a lithium battery negative electrode material with adjustable gram-specific capacity, first efficiency and rate.

[0078] The indicators of performance-adjustable lithium battery negative electrode materials are: ash content ≤ 0.01%, first discharge specific capacity ≥ 400mAh / g, first coulombic efficiency ≥ 85%, 100 times 0.2C cycle capacity retention rate ≥ 80%, cycle performance ≥ 400 cycles, rate performance (2C / 0.2C) ≥ 80%, see Figure 1 、 Figure 2 .

[0079] Example 1:

[0080] Tables 1 to 5 show the co-production of silicon-carbon negative electrode materials using a performance-controlled lithium battery negative electrode material and the preparation process parameters and test results.

[0081] Table 1 Preparation process and indicators of artificial graphite precursor

[0082]

[0083] Table 2 Preparation process and indicators of capacity-type lithium battery negative electrode materials

[0084]

[0085] Table 3 Preparation process and indicators of rate-type lithium battery negative electrode materials

[0086]

[0087] Table 4 Preparation process and indicators of core-shell silicon-carbon negative electrode materials

[0088]

[0089]

[0090] Table 5 Performance-adjustable lithium battery negative electrode material indicators

[0091]

[0092] The present invention not only provides the lithium battery field with a performance-adjustable negative electrode material product with high first efficiency, excellent cycle performance and low volume expansion rate, but also co-produces capacity-type negative electrode materials, rate-type negative electrode materials, core-shell silicon-carbon negative electrode materials and a variety of high-quality raw oils. The preparation process is simple, the manufacturing cost is low, and it is safe, reliable and pollution-free. It reduces the production cost of deep processing of coal tar, improves the comprehensive competitiveness of lithium battery negative electrode material products and silicon-carbon negative electrode material products, and solves the problem of efficient and high value-added utilization of coal tar.

Claims

1. A method for preparing a lithium battery negative electrode material with adjustable performance and co-producing a silicon-carbon negative electrode material, characterized in that: The following steps are involved: 1) Distilling coal tar to remove light oil and obtain coal tar heavy oil; 2) performing solid-liquid separation on the coal tar heavy oil to obtain heavy oil residue and heavy oil centrifuge liquid; 3) The heavy oil centrifuge liquid is mixed with an extractant, and subjected to extraction and separation treatment to obtain a soluble phase and an insoluble phase, respectively. The soluble phase is recovered by solvent and distilled to obtain purified heavy oil; 4) Carbonizing the purified heavy oil to obtain an artificial graphite precursor; 5) The artificial graphite precursor is graphitized to obtain a capacity-type lithium battery negative electrode material; the artificial graphite precursor is granulated to obtain a rate-type lithium battery negative electrode material; 6) The insoluble phase obtained in step 3) is sequentially dried, activated, oxidatively stabilized, and carbonized, and then mixed with silicon powder, ground, and then mixed with coated asphalt, and a silicon-carbon negative electrode precursor is obtained by coating; 7) The silicon-carbon anode precursor is calcined to obtain a core-shell silicon-carbon anode material; 8) The core-shell silicon-carbon negative electrode material is mixed with the capacity-type lithium battery negative electrode material and the rate-type lithium battery negative electrode material obtained in step 5) to obtain a lithium battery negative electrode material with adjustable gram-specific capacity, first efficiency and rate.

2. The method for preparing a performance-adjustable lithium battery negative electrode material and a silicon-carbon negative electrode material according to claim 1, characterized in that: In step 1), the coal tar is high-temperature coal tar, and the quinoline insoluble matter content is 1% to 15%; The reaction conditions of the distillation treatment are: the tower bottom temperature is controlled at 250-360°C, the tower top temperature is controlled at 100-240°C, and the vacuum degree is controlled at 0.01-0.09 MPa; The light oil is the front distillate oil with a temperature of 260-320°C in high-temperature coal tar; The quinoline insoluble matter content in the coal tar heavy oil is 1% to 20%, and the density is 1.13 to 1.3 g / cm 3 .

3. The method for preparing a performance-adjustable lithium battery negative electrode material and a co-production of a silicon-carbon negative electrode material according to claim 1, characterized in that: In step 2), the reaction conditions of the solid-liquid separation treatment are: separation temperature 60-150° C., separation time 0.5-10 h, centrifugal speed 800-2000 rad / min, and sieve mesh size 100-900 mesh; The content of quinoline insoluble matter in the heavy oil centrifuge liquid is 0-0.1%.

4. The method for preparing a performance-adjustable lithium battery negative electrode material and a silicon-carbon negative electrode material according to claim 1, characterized in that: In step 3), the extractant is one or a mixture of two or more of acetone, benzene, toluene, xylene, pyridine, and quinoline; The mass ratio of the extractant to the heavy oil centrifuge liquid is (1-5):1; The reaction conditions of the extraction and separation treatment are: extraction temperature 20-150° C., extraction time 0.5-10 h, and sieve mesh size 300-1200 mesh; The reaction conditions for solvent recovery are: gas phase temperature 60-160°C, kettle bottom temperature 100-280°C, vacuum degree 0.01-0.09 MPa, and residence time 0.5-2 h; The reaction conditions of the distillation are: gas phase temperature 160-280°C, kettle bottom temperature 320-380°C, vacuum degree 0.01-0.06 MPa, and residence time 2-4 hours; The purified heavy oil has a quinoline insoluble matter content of 0-0.01%, an ash content of <0.05%, and a density of 1.05-1.2 g / cm 3 , the fraction before 300℃ is ≤10%.

5. The method for preparing a performance-adjustable lithium battery negative electrode material and co-producing a silicon-carbon negative electrode material according to claim 1, characterized in that: In step 4), the carbonization reaction conditions are: under nitrogen protection, a nitrogen flow rate of 300-1200 ml / min, a heating rate of 1-10°C / min, a carbonization final temperature of 700-2000°C, and a final temperature constant time of 1-20 hours; The indicators of the artificial graphite precursor are: mesophase content ≥85%, ash content ≤0.01%.

6. The method for preparing a performance-adjustable lithium battery negative electrode material and co-producing a silicon-carbon negative electrode material according to claim 1, characterized in that: In step 5), the reaction conditions of the graphitization treatment are: under argon protection, a heating rate of 1-20°C / min, a final graphitization temperature of 2500-3000°C, and a final temperature holding time of 1-10 hours; The granulation process comprises: adding coating asphalt to the artificial graphite precursor, wherein the coating asphalt addition ratio is 5wt% to 15wt%, the reaction temperature is 600 to 900°C, and the reaction time is 2 to 10 hours; The index of the capacity type lithium battery negative electrode material is: D 10 :6~15μm, D 50 :15~24μm, D 90 ≤40.0μm, D max ≤50.0μm, specific surface area 0.9~2.0m 2 / g, tap density ≥0.92g / cm 3 , fixed carbon content ≥ 99.9%, graphitization degree ≥ 94.0%, first discharge specific capacity ≥ 372.0mAh / g, first coulombic efficiency ≥ 90%; The index of the rate-type lithium battery negative electrode material is: D 10 :6~15μm, D 50 :15~24μm, D 90 ≤40.0μm, D max ≤50.0μm, specific surface area 0.9~2.0m 2 / g, tap density ≥0.92g / cm 3 , fixed carbon content ≥99.9%, graphitization degree ≥94.0%, first discharge specific capacity ≥340.0mAh / g, and cycle retention rate ≥80% after 600 cycles at 3C rate.

7. The method for preparing a performance-adjustable lithium battery negative electrode material and co-producing a silicon-carbon negative electrode material according to claim 1, characterized in that: In step 6), the toluene insoluble matter content in the insoluble phase is 40% to 90%, and the ash content is less than 0.05%; The drying conditions are as follows: drying temperature is 160-320°C, and drying time is 0.5-5h; The activation reaction conditions are as follows: the activation reaction temperature is 500-1000°C, the reaction atmosphere is one of oxygen, air, and carbon dioxide, the flow rate is 60-300 L / h, and the activation time is 0.5-15h; The reaction conditions of the oxidation stabilization are: air temperature of 160-340°C, air flow of 1-10m 3 / h, processing time is 1~5h; The carbonization reaction conditions are as follows: under nitrogen protection, a nitrogen flow rate of 300-1200 ml / min, a heating rate of 1-10°C / min, a carbonization final temperature of 700-2000°C, and a final temperature constant time of 1-20h; The particle size D of the silicon powder 50 The particle size is 0.1~200nm; the silicon powder accounts for 1%~20% of the mass of the insoluble phase after treatment; The grinding process comprises: stirring at a speed of 100 to 3000 rad / min for 1 to 20 hours; The coating asphalt has a softening point of 110-280° C. and a coking value of 20-80; the coating asphalt accounts for 5%-20% of the mass of the mixture of silicon powder and the treated insoluble phase; The reaction conditions of the coating treatment are: under 0.1-0.5 L / min nitrogen protection, heating rate of 2-10°C / min, final temperature of 360-650°C, time of 1-8 hours, and converter frequency of 20-80 Hz; The indicators of the silicon-carbon negative electrode precursor are: specific surface area: 0.7~3m 2 / g, tap density: 0.6~1.15g / cm 3 , ash content <0.05%.

8. The method for preparing a performance-adjustable lithium battery negative electrode material and co-producing a silicon-carbon negative electrode material according to claim 1, characterized in that: In step 7), the reaction conditions of the calcination treatment are: under nitrogen protection, a nitrogen flow rate of 300-1200 ml / min, a heating rate of 1-10°C / min, a final calcination temperature of 700-1200°C, and a final temperature hold time of 1-30 hours; The core-shell silicon-carbon negative electrode material has the following indexes: particle size distribution D 10 :6~12μm、D 50 :15~24μm、D 90 : 28~45μm, true density ≥2.24g / cm 3 , tap density ≥0.9g / cm 3 , the powder compaction density is ≥1.55g / cm 3 , ash content ≤ 0.01%, first coulombic efficiency ≥ 80%, first discharge specific capacity ≥ 450mAh / g, 100 times 0.1C cycle capacity retention rate ≥ 80%, cycle performance ≥ 400 cycles, rate performance 2C / 0.2C ≥ 80%.

9. The method for preparing a performance-adjustable lithium battery negative electrode material and co-producing a silicon-carbon negative electrode material according to claim 1, characterized in that: In step 8), the core-shell silicon-carbon negative electrode material, the capacity-type lithium battery negative electrode material, and the rate-type lithium battery negative electrode material are mixed in a mass ratio of 10:(1-20):(1-10).

10. A performance-adjustable lithium battery negative electrode material co-produced with silicon-carbon negative electrode material prepared by the preparation method according to claim 1, characterized in that: The indicators of the performance-adjustable lithium battery negative electrode material are: ash content ≤ 0.01%, first discharge specific capacity ≥ 400 mAh / g, first coulombic efficiency ≥ 85%, 100 0.2C cycle capacity retention rate ≥ 80%, cycle performance ≥ 400 cycles, and rate performance 2C / 0.2C ≥ 80%.

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