CN114455578A - Novel graphitization method for graphite negative electrode material of lithium ion battery - Google Patents
Novel graphitization method for graphite negative electrode material of lithium ion battery Download PDFInfo
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- 238000005087 graphitization Methods 0.000 title claims abstract description 90
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 69
- 229910002804 graphite Inorganic materials 0.000 title claims abstract description 57
- 239000010439 graphite Substances 0.000 title claims abstract description 57
- 238000000034 method Methods 0.000 title claims abstract description 43
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 32
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 32
- 239000007773 negative electrode material Substances 0.000 title claims description 22
- 239000000463 material Substances 0.000 claims abstract description 57
- 239000002243 precursor Substances 0.000 claims abstract description 47
- 238000003723 Smelting Methods 0.000 claims abstract description 32
- 239000010406 cathode material Substances 0.000 claims abstract description 18
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 14
- 238000001816 cooling Methods 0.000 claims abstract description 9
- 238000007599 discharging Methods 0.000 claims abstract description 7
- 239000012774 insulation material Substances 0.000 claims abstract description 6
- 238000009413 insulation Methods 0.000 claims abstract description 5
- 230000009466 transformation Effects 0.000 claims abstract description 3
- 238000000465 moulding Methods 0.000 claims description 18
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 claims description 18
- 229910010271 silicon carbide Inorganic materials 0.000 claims description 18
- 230000005611 electricity Effects 0.000 claims description 12
- 239000000843 powder Substances 0.000 claims description 11
- 238000002156 mixing Methods 0.000 claims description 9
- 238000003825 pressing Methods 0.000 claims description 9
- 238000001125 extrusion Methods 0.000 claims description 7
- 238000000748 compression moulding Methods 0.000 claims description 6
- 238000000462 isostatic pressing Methods 0.000 claims description 5
- 239000002008 calcined petroleum coke Substances 0.000 claims description 4
- 239000011810 insulating material Substances 0.000 claims description 4
- 239000000571 coke Substances 0.000 claims description 3
- 239000006229 carbon black Substances 0.000 claims description 2
- 239000011331 needle coke Substances 0.000 claims description 2
- 239000006253 pitch coke Substances 0.000 claims description 2
- 239000010405 anode material Substances 0.000 claims 2
- 238000004321 preservation Methods 0.000 abstract description 13
- 230000000694 effects Effects 0.000 abstract description 12
- 239000002245 particle Substances 0.000 abstract description 5
- 238000010438 heat treatment Methods 0.000 description 24
- 238000004519 manufacturing process Methods 0.000 description 12
- 230000008569 process Effects 0.000 description 12
- 230000005540 biological transmission Effects 0.000 description 8
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 7
- 238000011161 development Methods 0.000 description 7
- 229910052744 lithium Inorganic materials 0.000 description 7
- 238000011160 research Methods 0.000 description 5
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- 238000012360 testing method Methods 0.000 description 4
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- 238000002360 preparation method Methods 0.000 description 3
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- 239000010426 asphalt Substances 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000007580 dry-mixing Methods 0.000 description 2
- 238000004898 kneading Methods 0.000 description 2
- 239000012778 molding material Substances 0.000 description 2
- 238000006386 neutralization reaction Methods 0.000 description 2
- 239000002006 petroleum coke Substances 0.000 description 2
- 238000004663 powder metallurgy Methods 0.000 description 2
- 238000003908 quality control method Methods 0.000 description 2
- 230000002159 abnormal effect Effects 0.000 description 1
- 239000002194 amorphous carbon material Substances 0.000 description 1
- 239000002969 artificial stone Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000003763 carbonization Methods 0.000 description 1
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- 238000006243 chemical reaction Methods 0.000 description 1
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- 238000004146 energy storage Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
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Abstract
The invention discloses a novel graphitization method for a graphite cathode material of a lithium ion battery, which comprises the following steps of: preparing a graphite negative electrode precursor into a block-shaped precursor; placing a plurality of the massive precursors in a conductive cross section area in a smelting furnace from a furnace head to a furnace tail of the smelting furnace; adding a resistance material between adjacent block-shaped precursors to serve as a drainage layer, and paving a heat insulation material on the periphery of the conductive cross section area to form a heat insulation layer; the smelting furnace is electrified and heated to graphitize the blocky precursor; after the graphitization transformation, cooling and discharging. After the graphite cathode precursor is pressed and formed, the distance between material particles is small, the density is high, the heat conduction is fast, the charging quantity is high, the heat preservation effect is good, the performance of the graphitized product is high, the cost is only half of the cost of the same industry, and the method is a novel energy-saving, low-carbon, efficient and low-cost graphitizing method.
Description
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a novel energy-saving, low-carbon and high-efficiency graphitization method for a graphite cathode material of a lithium ion battery.
Background
The terminal market applications of lithium ion batteries are consumer electronics, power battery markets and energy storage battery markets. Lithium electricity cathode material is as one kind of lithium electricity consumptive material, along with the continuous promotion of lithium ion battery output, cathode material shipment volume also is in high-speed the growth. According to main target requirements of development plans of energy-saving and new energy automobile industries (2012-2020) (hereinafter referred to as "industry development plans") issued by state offices, the production capacity of pure electric vehicles and plug-in hybrid electric vehicles reaches 200 thousands and the accumulated output and sales volume exceeds 500 thousands in 2020. 37 thousands of new energy automobiles are produced in the middle of 2015, the distance from the target of industrial development planning is still far, and the future development space is huge.
According to the data arrangement of GGII and the research institute of the Chinese and commercial industries, the market scale of the lithium battery negative electrode material in China is increased from 64.6 hundred million yuan in 2016 to 140.2 hundred million yuan in 2020, and the annual composite growth rate is 21.4%. The research institute of the middle-commercial industry predicts that the market scale of the negative electrode material in China in 2021 can reach 159.1 hundred million yuan.
From the demand end, in 2016-. The research institute of the medium-business industry predicts that the demand of the negative electrode material of the lithium battery in 2021 year in China will reach 40.1 ten thousand tons.
The lithium ion battery cathode material is in the core link of the lithium battery industry chain, and the coke is used as the raw material to prepare powder and perform heat treatment to produce the powdery artificial stone black material with the largest consumption at present. The process principle is that carbon and graphite precursors are subjected to high-temperature oxygen-free sintering on the material at high temperature, amorphous carbon materials are converted to an ordered graphitized structure, long-range order of material lattices is guaranteed, the specific surface of the material is controlled, the density of the material is improved, and finally the material meets the process requirements of the use of a lithium battery cathode.
Graphitization is used as a high-energy-consumption industry, under the background of double control of energy consumption and carbon neutralization, the production capacity and the operating rate are limited, the landing difficulty of newly increased production capacity is increased, the scarcity of graphitized assets is remarkable, and the graphitized assets become a bottleneck link of negative electrode production expansion. The graphite electrode output in China is about 65 ten thousand tons/year, and the total graphite electrode capacity is about 100 ten thousand tons/year by adding the Acheson furnace independently constructed in part of factories. According to the prior art, the crucible-loaded negative electrode material is used for high-temperature modification, the utilization rate of the capacity of the Acheson furnace is about 25%, and the surplus capacity of the existing graphitized electrode is completely used for processing the negative electrode material, so that the existing requirements can not be met.
At present, the domestic graphitization productivity exceeds 80 ten thousand tons, namely, the newly increased productivity in 2021 years is only about 10 ten thousand tons. However, the domestic negative electrode yield reaches 43 ten thousand tons 8 months before 2021, the yield is increased by 115 percent on a year-by-year basis and is close to the annual level of 20 years, and the annual negative electrode yield is estimated to exceed 70 ten thousand tons.
The electricity charge accounts for higher graphitized production cost, so the graphitized energy is generally selected from areas with lower industrial and commercial electricity charges, and the graphitized energy is mainly concentrated in electricity price depression areas such as Nemeng, Sichuan, Shaanxi, Qinghai, Hunan and the like. The national development and improvement committee issues a notice of market reformation of the on-line electricity price in 10 months, and the market trading electricity price of the high-energy-consumption enterprise is not limited by upward floating by 20%. Graphitization is a high energy consuming industry and the cost of electricity will rise further. When the electricity price rises by 0.1 yuan/degree, the graphitization production cost is increased by about 1000 yuan/ton.
The production process of the cathode material at home and abroad comprises the procedures of raw material treatment, powder preparation, carbonization, graphitization and the like, wherein the graphitization method is a core technology of various enterprises and is also a key procedure for controlling the product cost. The cathode material is an ultrafine powder product, the material density is less than 1g/cm3, the volume is large, the charging amount is very low, the power consumption of each ton of product is high, and the average level of the industry is that the power consumption of each ton of product reaches 16000 ℃; the method accounts for more than 50% of the product cost, and the process is a key process for changing the quality level of the cathode material.
However, in China, few enterprises have the own Acheson furnace for graphitization treatment, most enterprises entrust external enterprises to process, the cost is high, the outsourcing transportation cost is increased, the quality control risk is increased, comprehensive utilization cannot be realized, a complete industrial chain is formed, the graphitization process is a key link in the production of the lithium battery negative electrode material, and the quality control in the production process is directly related to the application performance of the negative electrode material. On the premise of ensuring the electrochemical performance of the processed product, how to improve the charging quantity and reduce the electricity consumption is a problem which needs to be solved urgently by negative electrode material production enterprises and carbon enterprises in China.
Disclosure of Invention
In order to solve the problems, the invention provides a novel graphitization method for a graphite negative electrode material of a lithium ion battery.
The technical scheme of the invention is as follows:
a novel graphitization method for a graphite cathode material of a lithium ion battery comprises the following steps:
s1, preparing the graphite cathode precursor into a block precursor;
s2, placing a plurality of block-shaped precursors in a conductive section area in the smelting furnace from the furnace head to the furnace tail of the smelting furnace;
s3, adding a resistance material between the adjacent blocky precursors to serve as a drainage layer, and paving a heat insulation material on the periphery of the conductive cross section area to form a heat insulation layer;
s4, feeding electricity to the smelting furnace to raise the temperature so as to graphitize the blocky precursor;
and S5, cooling and discharging after graphitization transformation.
The invention prepares the precursor of the cathode material (graphite cathode precursor) to be graphitized into blocks with certain shapes (such as square, cylinder and other shapes) according to different properties, and then the block precursors are arranged in a smelting furnace from the furnace head to the furnace tail and positioned in the area of the conductive cross section, and can be arranged in different stacks along the length direction.
According to the invention, the furnace resistor capable of realizing the graphitization effect is achieved by conducting according to the resistance and the shape of the block material to be graphitized and the certain conduction layer matched with the resistance and the material characteristic of the block material to be graphitized according to the requirement, then the heat preservation material is paved outside the conduction section to achieve the heat preservation effect, and finally the power transmission curve is set according to the material characteristic, the furnace resistor after furnace charging and other conditions to transmit power to achieve the graphitization effect.
According to the invention, different types of drainage layers can be designed according to the resistance, granularity and the like of different materials, a heat insulation layer with certain thickness, resistance and the like can be laid according to the characteristics of the materials, and then power is transmitted according to the requirements of different materials to carry out power transmission and heating treatment (generally, the temperature is increased to ensure that the furnace temperature reaches at least 2500 ℃) so as to complete graphitization conversion of the negative electrode block material.
After the graphite cathode precursor is pressed and formed, the distance between material particles is small, the density is high, the heat conduction is fast, the charging amount is high, the heat preservation effect is good, the performance of graphitized products is high, the cost is only half of the same industry cost, and the petroleum coke heat preservation material used as the smelting petroleum coke heat preservation material can be used as the raw material of the lithium ion battery cathode, can be recycled and can also be used as a carbon product, so the method is a novel energy-saving, low-carbon, high-efficiency and low-cost graphitization method.
The method for producing the bulk precursor of the present invention may be various, and may be obtained by various methods, and preferably, the bulk precursor is obtained by directly press-molding the graphite negative electrode precursor in step S1. The invention can adopt a direct compression molding mode, and is simple and quick.
Preferably, in step S1, a molding material for easy molding is added to the graphite negative electrode precursor, and after uniform mixing, the bulk precursor is obtained by press molding. In order to ensure successful forming of the block precursor, the graphite negative electrode precursor and the formed product (such as the binder and the additive) are mixed by a mixing mode such as wet mixing, dry mixing, kneading and the like, and finally pressed into the block by a mode such as extrusion, isostatic pressing, mould pressing, vibration forming and the like.
The press molding method in the present invention is preferably extrusion molding, press molding, isostatic pressing or vibration molding.
As can be seen from the above, the block precursor of the present invention can be molded in various ways, for example, directly by compression molding or by compression molding with a molding material (binder and/or additive) added thereto.
The resistance material in the invention can be various substances, and in order not to cause the performance change of the final material, the resistance material is preferably carbon products with different resistance sizes or different components, or is a powdery graphite negative electrode precursor.
Preferably, the electric resistance material is in a granular shape, a powder shape or a block shape.
The heat insulating material can be various, preferably, the heat insulating material is at least one of calcined petroleum coke, metallurgical coke, pitch coke, carbon black, needle coke and a negative electrode precursor.
Preferably, the smelting furnace is a silicon carbide smelting furnace.
The silicon carbide smelting furnace is not suitable for the way of graphitizing the negative electrode powder in the graphite negative electrode industry at present due to the characteristics of small current, high furnace resistance, high voltage and the like, and the characteristics of small furnace loading amount, high cost and the like, and the silicon carbide capacity is surplus, so that a plurality of silicon carbide smelting furnaces are idle at present. The graphitization process is a key link of carbon product production, and a large amount of idle silicon carbide smelting furnaces at present can be used as the graphitization heat treatment furnace for the graphite cathode material of the lithium ion battery, so that the silicon carbide smelting furnace can be successfully transformed, and the problem of capacity limitation caused by the shortage of graphitization resources in the graphite cathode industry at present is solved; meanwhile, the negative electrode powder to be graphitized is pressed and molded for graphitization, and a high-performance graphite negative electrode material can be obtained by using unique graphitization processes such as a drainage layer and the like.
According to the invention, the high-performance graphite cathode material is obtained, and the capacity of graphitization heat treatment can be improved by more than one time under the same condition, so that the cost of the graphite cathode for the lithium ion battery is fundamentally and greatly reduced, the national energy-saving and emission-reduction plan is met, the development targets of carbon neutralization and carbon peak reaching proposed by the country are met, and finally, good conditions are provided for further development of lithium ion battery industrialization.
In summary, the principle of the graphitization method of the present invention is as follows:
(1) pressing the material to be graphitized into a block according to the conditions of the volatile matter, the resistance, the adhesion and the like of the material:
directly pressing and molding a precursor of the negative electrode material to be graphitized by adopting a pressing mode such as extrusion, mould pressing, isostatic pressing, vibration molding and the like or pressing and molding by adding a binder and an additive, namely mixing the negative electrode material to be graphitized with the binder, the additive and the like in a mixing mode such as wet mixing, dry mixing, mixing and kneading, and finally pressing into a block by adopting a mode such as extrusion, isostatic pressing, mould pressing, vibration molding and the like;
(2) design of charging mode
Designing a furnace core section for graphitizing by using a silicon carbide smelting furnace according to the required graphitized material condition and the actual condition of the smelting furnace;
designing a charging mode after the cross section of the furnace core is designed, designing the charging mode of the material according to the resistance, ash content and volatile indexes of the graphitized material as required, wherein the charging mode comprises the steps of how blocks are placed, how a drainage layer is laid, the material requirement of the drainage layer, the material requirement of a heat insulation material, the power transmission requirement and the like. In the placing process of the blocky precursor, gaps among the blocks are filled with the drainage layer, and the situations of virtual connection, gaps and the like cannot occur, so that the abnormal power transmission caused by the influence on furnace resistance is prevented.
(3) Charging according to design requirements:
and charging according to a designed mode.
(4) Graphitization heat treatment of silicon carbide smelting furnace
And carrying out heat treatment according to the actual condition of the graphitized material, the graphitization requirement and the actual condition of the silicon carbide smelting furnace. For example, in a silicon carbide smelting furnace, graphite powder is adopted in the center of a furnace core for drainage, then a powdery precursor for smelting silicon carbide is filled around the furnace core, and a heat-insulating material is filled around the outermost part for heat insulation, so that the temperature of the furnace core reaches 2800 ℃ or higher at about 2000 ℃ of the outer side.
(5) Cooling and discharging:
and cooling, discharging and the like are carried out according to a conventional graphitization mode.
Compared with the prior art, the invention has the beneficial effects that:
(1) the invention adopts the block which is pressed and formed by the negative electrode precursor powder needing graphitization, and the block is arranged in the conductive section of the furnace core of the smelting furnace and is matched with the drainage layer with certain resistance for charging, so that the proper furnace resistance is achieved, under certain voltage, the current in the furnace meets the Joule Lenz law, the negative electrode block reaches the temperature required by graphitization heat treatment, the graphitization of the product is finally realized, and the comprehensive performance of the product is comprehensively improved.
(2) The cost of the invention is reduced to less than half:
the unique graphitization process enables the silicon carbide smelting furnace to be used as a graphitization heat furnace treatment furnace, and the silicon carbide smelting furnace can be used as a graphitization heat treatment furnace, so that the problem of price rise caused by shortage of the traditional graphitization furnace is solved;
the material needing graphitization is subjected to compression molding heat treatment, the volume density is increased as well, the charging amount is doubled compared with the charging mode of powder in the prior industry, and the cost is obviously reduced.
(3) The comprehensive performance is improved:
according to the invention, the heat treatment is carried out after the negative electrode needing graphitization heat treatment is pressed and formed, the distance between material particles is small, the density is high, the heat conduction is fast, the heat preservation effect is good, the performance of the product after the final graphitization heat treatment is higher, the capacity is improved by more than or equal to 3mAh/g, and the graphitization degree is increased by more than 2%.
Drawings
FIG. 1 is a schematic view of a charging structure in an embodiment of the present invention (see FIG. 2 for explanation of reference numerals in the figure).
FIG. 2 is a schematic sectional view of a charging structure in an embodiment of the present invention.
Fig. 3 is a test report of the graphitization degree of the graphite negative electrode material in the embodiment of the present invention.
Fig. 4 is a test report of the graphitization degree of the same type of graphite negative electrode material after being graphitized by the heat treatment of the conventional Acheson graphitization furnace.
Detailed Description
In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention.
Example 1
The embodiment is a novel energy-saving, low-carbon, efficient and low-cost graphitization method for a graphite cathode material of a lithium ion battery, which specifically comprises the following steps:
(1) preparation of graphite negative electrode block requiring graphitization (making graphite negative electrode precursor into block precursor):
mixing 30 tons of graphite cathode precursors to be graphitized with 3 tons of asphalt (the softening point is 90-94 ℃, and the carbon residue is 55%);
and carrying out compression molding on the mixed material by using a molding press, wherein the molding shape is a cuboid, and the molding size is 350 mm-150 mm.
The model and batch are marked on the upper right corner of each face of the block by a marking machine, and the model batch used at this time is SC331AH 1101.
(2) Designing a furnace charging mode:
the case of the process of silicon carbide smelting furnace is described as follows:
a transformer: 8000kVA
Secondary side maximum current: 40000A
The highest voltage: 300V
Conductive cross-sectional size: width: not less than 1.1 m, height: not less than 1.1 m; conductive cross-sectional area: 1.1 × 1.1 ═ 1.21 square meters.
Average charge per furnace: 25 tons; width of the furnace body: 4.0 m, and the length of the furnace body is 30 m; the height of the furnace body is as follows: 4 meters.
The charging diagram is designed according to the situation of the material requiring graphitization of the furnace (see fig. 1 and fig. 2), and the actual charging situation is as follows:
graphitizing the product:
the total number of the graphitized blocks 1491 in the furnace is 71 rows, each row has 21 blocks, the upper layer and the lower layer have 7 layers, and each layer has 3 blocks.
Because contact resistance exists between blocks, powder for a current guiding layer with 200 resistance is embedded in a gap between the blocks, and meanwhile, the current guiding layer with 200 resistance is added in the middle of 3 rows to adjust the whole furnace resistance so as to ensure smooth power transmission, and the specific charging details are shown in figures 1 and 2.
Because the graphite cathode precursor is carbonized and the volatile components are low, the fastest graphitization temperature rise curve, namely the temperature rise curve of 100 ℃/hour, is adopted.
Laying a heat preservation material:
and paving 600mm thick heat insulation materials around the furnace core filled with the materials.
The specification of the heat preservation material is 2-5mm of calcined petroleum coke particles.
(3) Charging according to the designed graphitization condition in the second step: and charging according to a designed mode.
(4) Graphitization:
heating according to the design requirement, and keeping the temperature at 2800 ℃ for 10 hours according to the heating rate of 100 ℃/hour.
And setting a reasonable power transmission curve according to the required temperature curve.
(5) Cooling and discharging:
and after the heat preservation is finished, cooling along with the furnace temperature.
And (3) testing:
after graphitization, the graphitization degree is mainly tested to see the graphitization effect of the graphite negative electrode;
in the present embodiment, the indexes of the graphitized heat-treated material and the same material after graphitizing heat treatment by using a conventional acheson graphitizing furnace are shown in table 1:
TABLE 1
| Numbering | Average degree of graphitization | Specific surface area | Gram capacity of half cell | First time efficiency |
| Example 1 | 97.1％ | 1.25m2/g | 363mAh/g | 94.3％ |
| Comparison of conventional | 96.9％ | 1.32m2/g | 360mAh/g | 94.1％ |
Remarking: the average graphitization degree is tested by the powder metallurgy research institute of the university of Central and south entrusted, and the specific surface, the gram capacity of the half cell and the first efficiency are detected according to a detection method of corresponding indexes in the national standard GB/T245633-2009 lithium ion battery graphite cathode material.
As can be seen from the above Table 1, the material index of the present example is significantly better than that of the conventional graphitization method.
According to the situation of example 1, it can be seen that under the technical conditions of the present invention, the graphitization heat treatment of the graphite negative electrode for the lithium ion battery by using the silicon carbide smelting furnace can meet the graphitization heat treatment requirement of the graphite negative electrode for the lithium ion battery, and the effect is better than the graphitization effect of the Acheson graphitization furnace currently used.
Example 2
The embodiment is a novel energy-saving, low-carbon, efficient and low-cost graphitization method for a graphite cathode material of a lithium ion battery, which specifically comprises the following steps:
(1) preparation of graphite negative electrode block requiring graphitization:
30 tons of graphite cathode precursors needing graphitization are kneaded with 3 tons of asphalt (the softening point is 90-94 ℃, and the carbon residue is 55%);
and (3) carrying out extrusion molding on the kneaded material by using an extrusion molding device, wherein the molded shape is a cylinder, and the size of a molded block is phi 600mm x 1000 mm.
The model and batch are marked on the upper right corner of each face of the block by a marking machine, and the model batch used at this time is SC331AH 1106.
(2) Designing a furnace charging mode:
the case of the process of silicon carbide smelting furnace is described as follows:
a transformer: 8000kVA
Secondary side maximum current: 40000A
The highest voltage: 300V
Conductive cross-sectional size: width: not less than 1.1 m, height: not less than 1.1 m; conductive cross-sectional area: 1.1 × 1.1 ═ 1.21 square meters.
Average charge per furnace: 30 tons; width of the furnace body: 4.0 m, and the length of the furnace body is 30 m; the height of the furnace body is as follows: 4 meters.
A charging diagram is designed according to the situation of the material required to be graphitized in the furnace (see the attached drawing in detail), and the actual charging situation is as follows:
graphitizing the product:
the total number of the graphitized blocks in the furnace is 120, 30 rows of blocks are arranged, 4 blocks in each row are arranged, 2 layers are arranged up and down, and 2 blocks are arranged in each layer.
Because contact resistance exists between blocks, powder for a current guiding layer with 200 resistance is embedded in a gap between the blocks, and meanwhile, the current guiding layer with 200 resistance is added in the middle to adjust the whole furnace resistance so as to ensure smooth power transmission.
Because the graphite cathode precursor is carbonized and the volatile components are low, the fastest graphitization temperature rise curve, namely the temperature rise curve of 100 ℃/hour, is adopted.
Laying a heat preservation material:
and paving 600mm thick heat insulation materials around the furnace core filled with the materials.
The specification of the heat preservation material is 2-5mm of calcined petroleum coke particles.
(3) Charging according to the designed graphitization condition in the second step: and charging according to a designed mode.
(4) Graphitization:
heating according to the design requirement, and keeping the temperature at 2800 ℃ for 10 hours according to the heating rate of 100 ℃/hour.
And setting a reasonable power transmission curve according to the required temperature curve.
(5) Cooling and discharging:
and after the heat preservation is finished, cooling along with the furnace temperature.
And (3) testing:
after graphitization, the graphitization degree is mainly tested to see the graphitization effect of the graphite negative electrode;
in this example, the indexes of the graphitized material after the graphitization heat treatment are shown in table 2, compared with the same material after the graphitization heat treatment by using a conventional acheson graphitization furnace:
TABLE 2
| Number of | Average degree of graphitization | Specific surface area | Gram capacity of half cell | First time efficiency |
| Example 2 | 98.5％ | 1.13m2/g | 365mAh/g | 94.5％ |
| Comparison of conventional | 96.9％ | 1.32m2/g | 360mAh/g | 94.1％ |
Remarking: the average graphitization degree is tested by the powder metallurgy research institute of the university of China, and the specific surface, the gram capacity of the half cell and the first efficiency are detected according to a detection method of corresponding indexes in the national standard GB/T243354-2009 lithium ion battery graphite cathode material.
As can be seen from the above Table 2, the material index of the present example is significantly better than that of the conventional graphitization method.
According to the conditions of the embodiment, the graphitization heat treatment of the graphite negative electrode for the lithium ion battery by using the silicon carbide smelting furnace can meet the requirement of the graphitization heat treatment of the graphite negative electrode for the lithium ion battery under the technical conditions of the invention, and the effect is better than the graphitization effect of the Acheson graphitization furnace currently used.
It is to be understood that the embodiments described herein are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Claims (10)
1. A novel graphitization method for a graphite cathode material of a lithium ion battery is characterized by comprising the following steps:
s1, preparing the graphite cathode precursor into a block precursor;
s2, placing a plurality of block-shaped precursors in a conductive section area in the smelting furnace from the furnace head to the furnace tail of the smelting furnace;
s3, adding a resistance material between the adjacent blocky precursors to serve as a drainage layer, and paving a heat insulation material on the periphery of the conductive cross section area to form a heat insulation layer;
s4, feeding electricity to the smelting furnace to raise the temperature so as to graphitize the blocky precursor;
and S5, cooling and discharging after graphitization transformation.
2. The novel graphitization method for graphite negative electrode material of lithium ion battery as claimed in claim 1, wherein the block precursor is obtained by directly pressing graphite negative electrode precursor in step S1.
3. The novel graphitization method for the graphite anode material of the lithium ion battery as claimed in claim 1, wherein in the step S1, a molding matter convenient for molding is added into a graphite anode precursor, and after uniform mixing, the block-shaped precursor is obtained by press molding.
4. The novel graphitization method for the graphite anode material of the lithium ion battery as claimed in claim 2 or 3, wherein the compression molding mode is extrusion molding, compression molding, isostatic pressing or vibration molding.
5. The novel graphitization method for the graphite negative electrode material of the lithium ion battery as claimed in claim 1, wherein the electric resistance material is a carbon product with different resistance sizes or different components.
6. The novel graphitization method for the graphite negative electrode material of the lithium ion battery as claimed in claim 1, wherein the resistance material is a powdered graphite negative electrode precursor.
7. The novel graphitization method for the graphite negative electrode material of the lithium ion battery as claimed in claim 1, wherein the electric resistance material is in a granular shape, a powder shape or a block shape.
8. The novel graphitization method for the graphite negative electrode material of the lithium ion battery as claimed in claim 1, wherein the heat insulating material is at least one of calcined petroleum coke, metallurgical coke, pitch coke, carbon black, needle coke and a negative electrode precursor.
9. The novel graphitization method for graphite negative electrode material of lithium ion battery as claimed in claim 1, wherein in step S4, temperature is raised to an oven temperature of at least 2500 ℃.
10. The novel graphitization method for graphite cathode material of lithium ion battery as claimed in claim 1, wherein the smelting furnace is a silicon carbide smelting furnace.
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