A method for preparing a lithium ion battery negative electrode material based on a square crucible

Abstract

The application discloses a method for preparing a lithium ion battery negative electrode material based on a square crucible, and comprises the following steps: removing coke powder, laying a heat preservation layer, surrounding a core plate, laying a cushion layer, loading the crucible, filling resistance material, building a core wall, laying a heat insulation layer, laying a top layer, exhausting, supplying power, cooling and unloading. The vertical production of the square crucible is adopted, the yield of single furnace is improved, and the cost is reduced. Meanwhile, through a three-dimensional heat preservation and insulation system, a furnace layer temperature difference is reduced, the space between the crucibles is optimized, and the power supply curve is optimized, so that the problem of small specific surface area of the product caused by the vertical placement of the square crucible is solved, and the high-quality and low-cost negative electrode material with large specific surface area is produced.

Description

Technical Field

[0001] This invention belongs to the field of graphite material manufacturing and processing, and specifically relates to a method for preparing lithium-ion battery anode materials based on a square crucible. Background Technology

[0002] Graphitization is a crucial step in the production of lithium-ion battery anode materials. After heat treatment at temperatures exceeding 2300℃, it determines the physicochemical properties of the graphite products. In the calcined graphite, the carbon atoms transform from a thermodynamically unstable "two-dimensional disordered overlap" arrangement to a "three-dimensional ordered overlap" arrangement through thermal activation. This further improves the product's thermoelectric conductivity, thermal shock resistance, chemical stability, oxidation resistance, lubricity, and wear resistance, while also eliminating impurities to increase purity and reducing hardness for easier machining. Specifically, the process involves filling the calcined carbonized material with coke, indirectly applying electricity to utilize the resistance heating of the coke, ultimately causing the heated material itself to undergo resistance heating, resulting in graphitization. Graphitization accounts for over 50% of the total production cost of anode materials. Currently, graphitization production mainly uses an Atchison-style crucible furnace with horizontal crucible loading, which is costly, suffers from severely uneven furnace temperatures, and produces products with small specific surface areas, making it unsuitable for producing high-quality anode materials. Summary of the Invention

[0003] The technical problem to be solved by this invention is how to produce artificial graphite anode materials in a U-shaped internal string graphitization furnace using a square crucible and a vertical crucible loading method, while increasing production capacity and reducing production costs, producing high-quality anode materials with a small specific surface area, and expanding the variety of anode graphitization products. This invention provides a method for preparing lithium-ion battery anode materials based on a square crucible to overcome the above-mentioned technical problems.

[0004] To address the aforementioned technical problems, the technical solution of the present invention, a method for preparing lithium-ion battery anode materials based on a square crucible, is as follows:

[0005] A method for preparing lithium-ion battery anode materials based on a square crucible includes an internally connected graphitization furnace, a crucible, and a power supply device. The internally connected graphitization furnace includes a left furnace wall, a right furnace wall, a front conductive wall, a rear conductive wall, a furnace bottom, and a pad layer. Graphite electrodes are mounted on both the front and rear conductive walls. The furnace bottom includes a carbon black layer. The method is characterized by the following features: a heat insulation layer is laid on top of the carbon black layer; two core walls are laid on top of the heat insulation layer and between the front and rear conductive walls. The core walls are vertically divided into three layers: core wall I, core wall II, and core wall III. The two core walls divide the furnace into three regions: region I, region II, and region III. From the left furnace wall to the right furnace wall, the areas are divided into Region I, Region II, and Region III. Within Region II, starting from the foundation layer, a foundation layer and a material layer are laid vertically upwards. The material layer is divided into three layers vertically: Material Layer I, Material Layer II, and Material Layer III. Similarly, the crucible is divided into three layers vertically: Crucible I, Crucible II, and Crucible III. Material Layer I includes Crucible I and Resistance Material I; Material Layer II includes Crucible II and Resistance Material II; and Material Layer III includes Crucible III and Resistance Material III. In Regions I and III, a heat insulation layer is laid, consisting of three layers: Heat Insulation Layer I, Heat Insulation Layer II, and Heat Insulation Layer III.

[0006] Starting from the material layer, the furnace top layer and the exhaust layer are laid vertically upwards in sequence. The furnace top layer covers the resistance material III, the furnace core wall III, the heat insulation layer III, and the crucible III. The exhaust layer covers the furnace top layer.

[0007] The exhaust layer is also provided with exhaust holes, which are arranged along the length of the furnace core wall. There are two rows of exhaust holes, with each row of exhaust holes being adjacent to the two furnace core walls and 60mm away from the furnace core walls. The spacing between the exhaust holes is 1500mm. The exhaust layer is surrounded by a 40-50 degree slope.

[0008] The method for preparing lithium-ion battery anode materials based on a square crucible further includes the following steps:

[0009] (1) Remove coke powder: Remove the coke powder from the bottom of the furnace down to the carbon black layer;

[0010] (2) Laying the insulation layer: Based on the lower edge of the graphite electrode, sink 180mm and lay the insulation layer flat;

[0011] (3) Furnace core plate: The furnace core plate includes a left furnace core plate and a right furnace core plate. The left furnace core plate and the right furnace core plate are arranged between the front conductive wall and the rear conductive wall. The left furnace core plate and the right furnace core plate are distributed symmetrically about the central axis. The left furnace core plate includes a left plate I and a right plate I. The width of the cavity I formed by the left plate I and the right plate I is 400mm. The right furnace core plate includes a left plate II and a right plate II. The width of the cavity II formed by the left plate II and the right plate II is 400mm. The distance between the right plate I of the left furnace core plate and the left plate II of the right furnace core plate is 2900mm. The left plate I of the left furnace core plate, the right plate I of the left furnace core plate, the left plate II of the right furnace core plate and the right plate II of the right furnace core plate are composed of three detachable sections and are used to construct the furnace core wall I, the furnace core wall II and the furnace core wall III respectively.

[0012] The wall thickness of the right furnace core plate is 400mm, and the distance between the right plate of the left furnace core plate and the left plate of the right furnace core plate is 2900mm.

[0013] The furnace core wall has a width of 2.9 meters.

[0014] Furnace core plate: Using the centerline of the conductive wall as a reference, a furnace core plate with a width of 2.9 meters is formed and fixed with clips. Insert plates are placed at the four corners to support the furnace core plate.

[0015] (4) Subbase layer: A subbase layer is laid in area II;

[0016] (5) Loading crucible I:

[0017] In region II, crucible I is placed vertically, and the remaining space in region II is filled with resistive material I and compacted. Then, calcined coke is laid in cavity I and cavity II to form furnace core wall I. Graphitized coke is laid in region I and region III to form heat insulation layer I. The resistive material I, furnace core wall I, heat insulation layer I and crucible I are at the same height.

[0018] Then, the portions of the left plate I, right plate I, left plate II, and right plate II corresponding to the furnace core wall I are pulled out and removed respectively.

[0019] (6) Loading crucible II:

[0020] Crucible II is placed vertically on crucible I in region II. The remaining space in region II is filled with resistive material II and compacted. Then, calcined coke is laid in cavity I and cavity II to form the furnace core wall II. Graphitized coke is laid in region I and region III to form the heat insulation layer II. The resistive material II, furnace core wall II, and heat insulation layer II are at the same height as crucible II.

[0021] Then, pull out and remove the portions of the left plate I, right plate I, left plate II, and right plate II corresponding to the furnace core wall II respectively;

[0022] (7) Loading crucible III:

[0023] Crucible III is placed vertically on crucible II in region II. The remaining space in region II is filled with resistive material III and compacted. Then, calcined coke is laid in cavity I and cavity II to form the furnace core wall III. Graphitized coke is laid in region I and region III to form the heat insulation layer III. The resistive material III, furnace core wall III, and heat insulation layer III are at the same height as crucible III.

[0024] Then, the portions of the left plate I, right plate I, left plate II, and right plate II corresponding to the furnace core wall I are pulled out and removed respectively.

[0025] In steps (5), (6) and (7) above, the layer spacing between crucible I and crucible II is 0, the layer spacing between crucible II and crucible III is 0, the spacing between crucibles in each layer is 55-70 mm, and the shape of crucible I, crucible II and crucible III is a cube.

[0026] (8) Laying the furnace top layer: The furnace top layer is formed by spreading graphitized coke on crucible III;

[0027] (9) Laying the exhaust layer: Place an exhaust pipe on the top of the furnace, then lay the calcined coke to form the exhaust layer, and then remove the exhaust pipe to form the exhaust hole;

[0028] (10) Power supply;

[0029] (11) Cooling and unloading.

[0030] Preferably, the carbon black layer meets the following requirements: ash content ≤ 0.5%, moisture content ≤ 0.5%, volatile matter ≤ 1.2%, carbon content ≥ 98%, sulfur content ≤ 0.5%, and resistivity ≥ 1800 μΩ·m.

[0031] Preferably, the heat insulation layer is laid 180 mm away from the lower edge of the graphite electrode, and the heat insulation layer is calcined coke with a particle size of 0-2 mm.

[0032] Preferably, the height of the padding layer is 50 mm, and the padding layer is calcined coke with a particle size of 8-12 mm.

[0033] Preferably, the resistive material I is calcined coke with a particle size of 3-8 mm, the resistive material II is calcined coke with a particle size of 8-16 mm, and the resistive material III is calcined coke with a particle size of 16-25 mm.

[0034] Preferably, the furnace core wall I, furnace core wall II and furnace core wall III are all calcined coke with a particle size of 0-2 mm.

[0035] Preferably, the heat insulation layer I, heat insulation layer II and heat insulation layer III are all graphitized coke with a particle size of 0 to 3 mm.

[0036] Preferably, the top layer of the furnace is graphitized coke with a height of 100 mm and a particle size of 8-12 mm.

[0037] Preferably, the exhaust layer is calcined coke with a height of 50 mm and a particle size of 3-8 mm.

[0038] Preferably, the power supply curve during power supply in step (9) is as follows: preheating power 0-3000kW, preheating power rise is 500kW / h; first stage power 3000-7000kW, first stage power rise is 200kW / h; second stage power 7000-8000kW, second stage power rise is 500kW / h; third stage power 8000-22000kW, third stage power rise is 2000kW / h, and after reaching 22000kW, it is maintained for 10h.

[0039] Compared with the prior art, the beneficial effects of this invention are as follows: the use of vertical production with square crucibles increases the output per furnace and reduces costs. At the same time, by using a three-dimensional heat insulation system, reducing the temperature difference between furnace layers, optimizing the spacing between crucibles, and optimizing the power delivery curve, the problem of small specific surface area of ​​products caused by the vertical placement of square crucibles is solved, and high-quality, low-cost anode materials with large specific surface area are produced. Attached Figure Description

[0040] Figure 1 A schematic diagram of the main view of the crucible loading structure;

[0041] Figure 2 A top view of the crucible loading structure;

[0042] Figure 3 A schematic diagram of the cross-section AA of the crucible loading structure;

[0043] Figure 4 Schematic diagram of the cross-section of the crucible loading structure (BB);

[0044] The above Figures 1-4In the middle: 1-Power supply device, 2-Graphite electrode, 3-Front conductive wall, 4-Rear conductive wall, 5-Left furnace wall, 6-Right furnace wall, 7-Carbon black layer, 8-Insulation layer, 9-Padded layer, 10-Resistant material I, 11-Resistant material II, 12-Resistant material III, 13-Furnace core wall I, 14-Furnace core wall II, 15-Furnace core wall III, 16-Insulation layer I, 17-Insulation layer II, 18-Insulation layer III, 19-Furnace top layer, 20-Exhaust layer, 21-Exhaust hole, 22-Crucible I, 23-Crucible II, 24-Crucible III, 25-Region I, 26-Region II, 27-Region III, 28-Lower edge of graphite electrode, 29-Central axis, 30-Left plate I, 31-Right plate I, 32-Cavity I, 33-Left plate II, 34-Right plate II, 35-Cavity II. Detailed Implementation

[0045] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0046] A method for preparing lithium-ion battery anode materials based on a square crucible includes an inner-string graphitization furnace, a crucible, and a power supply device 1. The inner-string graphitization furnace has an inner cavity width of 2900 mm and a length of 3000 mm. The inner-string graphitization furnace includes a left furnace wall 5, a right furnace wall 6, a front conductive wall 3, a rear conductive wall 4, and a furnace bottom. Graphite electrodes 2 are installed on both the front and rear conductive walls. The graphite electrodes 2 consist of 3 rows of 5 graphite electrodes each. The furnace bottom includes a carbon black layer 7. The method is characterized by a heat insulation layer 8 laid on the carbon black layer 7, and two furnace core walls laid on the heat insulation layer 8 and between the front conductive wall 3 and the rear conductive wall 4. The furnace core walls are vertically divided into three layers: furnace core wall I13, furnace core wall II14, and furnace core wall III15. The two furnace core walls divide the furnace into region I25 and region I25. There are three zones: I26 and III27. From the left furnace wall 5 to the right furnace wall 6, these zones are I25, II26, and III27, respectively. In zone II, starting from the insulation layer 8, a pad layer 9 and a material layer are laid vertically upwards. The material layer is divided into three layers: material layer I, material layer II, and material layer III. The crucible is also divided into three layers: crucible I22, crucible II23, and crucible III24. Material layer I includes crucible I22 and resistance material I10, material layer II includes crucible II23 and resistance material II11, and material layer III includes crucible III24 and resistance material III12. Insulation layers are laid in zones I25 and III26, and these insulation layers are divided into three layers: insulation layer I16, insulation layer II17, and insulation layer III18.

[0047] Starting from the material layer, a furnace top layer 19 and an exhaust layer 20 are laid vertically upwards. The furnace top layer 19 covers the resistance material III12, the furnace core wall III15, the heat insulation layer III18, and the crucible III24. The exhaust layer 20 covers the furnace top layer 19.

[0048] The exhaust layer 20 is also provided with exhaust holes 21, which are arranged along the length of the furnace core wall. There are two rows of exhaust holes 21, with each row of exhaust holes being adjacent to the two furnace core walls and 60mm away from the furnace core walls. The spacing between the exhaust holes 21 is 1500mm. The distance between the hole walls of the first and last two exhaust holes in each row and the front conductive wall 3 and the rear conductive wall 4 is greater than 1500mm. The exhaust layer 21 is provided with a 40-50 degree slope around its perimeter.

[0049] The method for preparing lithium-ion battery anode materials based on a square crucible further includes the following steps:

[0050] (1) Remove coke powder: Remove coke powder from the bottom of the furnace down to the carbon black layer 7. Each batch of carbon black must be sampled and tested to meet the following requirements: ash content ≤0.5%, moisture content ≤0.5%, volatile matter ≤1.2%, carbon content ≥98%, sulfur ≤0.5%, resistivity ≥1800μΩ·m.

[0051] (2) Laying the insulation layer 8: Laying the insulation layer 8 flat, the insulation layer is laid to a distance of 180 mm from the lower edge of the graphite electrode. The insulation layer is calcined coke with a particle size of 0-2 mm, and it is required to be flat without unevenness.

[0052] (3) Furnace core plate: The furnace core plate includes a left furnace core plate and a right furnace core plate, which are surrounded between the front conductive wall 3 and the rear conductive wall 4. The left and right furnace core plates are distributed symmetrically about the central axis 29. The left and right furnace core plates adopt a common building timber formwork structure. The left furnace core plate includes a left plate I30 and a right plate I31. The cavity I32 formed by the left plate I30 and the right plate I31 has a width of 400mm. The right furnace core plate includes a left plate II33 and a right plate II34. The cavity I32 formed by the left plate II33 and the right plate II34 has a width of 400mm. The width of cavity II35 is 400mm; the distance between right plate I31 and left plate II33 is 2900mm; the left plate I30, right plate I31, left plate II33 and right plate II34 are composed of 3 detachable sections and are used to construct furnace core wall I13, furnace core wall II14 and furnace core wall III15 respectively. The left plate I30, right plate I31, left plate II33 and right plate II34 are fixed with clips and supported by insert plates at the four corners. The left plate I30, right plate I31, left plate II33 and right plate II34 are all made of plywood.

[0053] (4) Padding layer: Padding layer 9 is laid in area II26. The height of padding layer 9 is 50mm. Padding layer 9 is calcined coke with a particle size of 8-12mm.

[0054] (5) Loading crucible I:

[0055] A crucible I22 is placed vertically in region II26, and then the remaining space in region II26 is filled with resistive material I10 and compacted. The resistive material I10 is calcined coke with a particle size of 3-8mm.

[0056] Then, calcined coke with a particle size of 0-2 mm is laid in the cavity I32 and cavity II35 to form the furnace core wall I13;

[0057] In regions I25 and III, graphitized coke with a particle size of 0-3 mm is laid to form the heat insulation layer I16.

[0058] The resistance material I10, the furnace core wall I13, the heat insulation layer I16 are at the same height as the crucible I22;

[0059] Then, the portions of the left plate I30, right plate I31, left plate II33 and right plate II34 corresponding to the furnace core wall I13 are pulled out and removed respectively.

[0060] (6) Loading crucible II:

[0061] Place crucible II23 vertically on crucible I22 in region II26, and then fill the remaining space in region II26 with resistive material II11 and pack it firmly. The resistive material II10 is calcined coke with a particle size of 8-16mm.

[0062] Then, calcined coke with a particle size of 0-2 mm is laid in the cavity I32 and cavity II35 to form the furnace core wall II14;

[0063] The heat insulation layer II17 is formed by laying graphitized coke with a particle size of 0-3 mm in regions I25 and III27.

[0064] The resistance material II11, the furnace core wall II14, the heat insulation layer II17 are at the same height as the crucible II23;

[0065] Then, the portions of the left plate I30, right plate I31, left plate II33 and right plate II34 corresponding to the furnace core wall II14 are pulled out and removed respectively.

[0066] (7) Loading crucible III:

[0067] Place crucible III24 vertically on crucible II23 in region II26, and then fill the remaining space in region II26 with resistive material III12 and pack it firmly. The resistive material III10 is calcined coke with a particle size of 16-25mm.

[0068] Then, calcined coke with a particle size of 0-2 mm is laid in the cavity I32 and cavity II35 to form the furnace core wall III15;

[0069] The heat insulation layer III18 is formed by laying graphitized coke with a particle size of 0-3 mm in regions I25 and III27.

[0070] The resistance material III12, the furnace core wall III15, the heat insulation layer III18 are at the same height as the crucible III24;

[0071] Then, the portions of the left plate I30, right plate I31, left plate II33 and right plate II34 corresponding to the furnace core wall I15 are pulled out and removed respectively.

[0072] In steps (5), (6), and (7) above, the interlayer spacing between crucible I22 and crucible II23 is 0, and the interlayer spacing between crucible II23 and crucible III24 is 0. The spacing between crucibles in each layer is 55-70 mm. Experimental studies have shown that this spacing is one of the key factors affecting the surface area of ​​the product. The distances between the four edges of each crucible and the two furnace core walls, the front conductive wall 3, and the rear conductive wall 4 are all greater than 60 mm. The crucibles I22, II23, and III24 are all cubes, and these cube crucibles are also called square crucibles.

[0073] (8) Laying the top layer 19: Graphitized coke with a height of 100 mm and a particle size of 8-12 mm is laid flat on the crucible III24 to form the top layer 19 of the furnace. The top layer 19 of the furnace covers the entire inner-string graphitization furnace and covers the resistance material III12, the furnace core wall III15, the heat insulation layer III18 and the crucible III24.

[0074] (9) Laying the exhaust layer 20: Place an exhaust pipe on the top layer 19 of the furnace, and then lay calcined coke with a height of 50 mm and a particle size of 3-8 mm to form the exhaust layer 20. The exhaust layer 20 covers the top layer 19 of the furnace, and then remove the exhaust pipe to form the exhaust hole 21.

[0075] (10) Power supply: Power is supplied to the inner-string graphitization furnace through power supply device 1. The power supply curve is as follows: preheating power is 0 to 3000 kW, and the preheating power rise is 500 kW / h; the first stage power is 3000 to 7000 kW, and the first stage power rise is 200 kW / h; the second stage power is 7000 to 8000 kW, and the second stage power rise is 500 kW / h; the third stage power is 8000 to 22000 kW, and the third stage power rise is 2000 kW / h. After reaching 22000 kW, it is maintained for 10 hours. The power supply curve is also one of the key factors affecting the surface area of ​​the product, and at the same time, it is also one of the key factors affecting the product cost.

[0076] (11) Cooling and unloading.

[0077] The graphitized coke involved in this invention is calcined coke that has been used once.

[0078] This invention, by employing a square vertical placement method, can increase the output per furnace batch by approximately 20-40% or more, but it suffers from a large product specific surface area. A three-dimensional heat insulation system, composed of an insulation layer, a pad layer, a furnace core wall, a heat insulation layer, a furnace top layer, and an exhaust layer, is used. The temperature difference between furnace layers is reduced by utilizing the different resistivity of resistive materials I, II, and III due to their varying particle sizes. An optimized power delivery curve further reduces the temperature difference between furnace layers. Optimizing the spacing between crucibles within each layer to 55-70 mm further reduces the product specific surface area.

[0079] In summary, by reducing the temperature difference between furnace layers through a three-dimensional thermal insulation system, optimizing the spacing between crucibles, and optimizing the power delivery curve, the problem of small specific surface area of ​​products caused by the vertical placement of square crucibles has been solved, resulting in the production of high-quality, low-cost anode materials.

[0080] The above embodiments are the main structural and shape parameters of the present invention. Other structural details are designed and selected in accordance with common technical knowledge and conventional technical means in this professional field.

Claims

1. A method for preparing a lithium ion battery negative electrode material based on a square crucible, comprising an inner series graphitization furnace, a crucible and a power transmission device, the inner series graphitization furnace comprises a left furnace wall, a right furnace wall, a front conductive wall, a rear conductive wall, a furnace bottom and a cushion layer, the front conductive wall and the rear conductive wall are both installed with a graphite electrode, and the furnace bottom comprises a carbon black layer, characterized in that, A heat preservation layer is laid on the carbon black layer, and two furnace core walls are laid on the heat preservation layer and between the front and rear conductive walls, which are divided into three layers in the vertical direction, i.e., furnace core wall I, furnace core wall II and furnace core wall III; the two furnace core walls divide the furnace into three areas, i.e., area I, area II and area III, which are area I, area II and area III from left to right; a cushion layer and a work material layer are laid in area II from the heat preservation layer in the vertical direction; the work material layer is divided into three layers in the vertical direction, i.e., work material layer I, work material layer II and work material layer III, the crucible is divided into three layers in the vertical direction, i.e., crucible I, crucible II and crucible III, the work material layer I includes crucible I and resistance material I, the work material layer II includes crucible II and resistance material II, and the work material layer III includes crucible III and resistance material III; a heat insulation layer is laid in area I and area III, which is divided into three layers, i.e., heat insulation layer I, heat insulation layer II and heat insulation layer III; A furnace top layer and an exhaust layer are laid in the vertical direction from the work material layer, the furnace top layer covers the resistance material III, furnace core wall III, heat insulation layer III and crucible III, and the exhaust layer covers the furnace top layer; The exhaust layer is also provided with exhaust holes, the exhaust holes are arranged along the length direction of the furnace core wall, the exhaust holes are arranged in two rows, each row of exhaust holes is arranged close to the two furnace core walls and is 60mm away from the furnace core wall, and the hole spacing of the exhaust holes is 1500mm; a 40-50 degree slope is arranged around the exhaust layer; The method for preparing the negative electrode material of the lithium ion battery based on the square crucible further includes the following steps: (1) removing coke powder: removing coke powder from the bottom of the furnace to the carbon black layer; (2) laying a heat preservation layer: sinking 180mm from the lower edge of the graphite electrode as a benchmark, and laying a heat preservation layer; (3) surrounding the furnace core plate: the furnace core plate includes a left furnace core plate and a right furnace core plate, which are surrounded between the front and rear conductive walls, and the left and right furnace core plates are distributed left and right with the center axis as the axis of symmetry, the left furnace core plate includes left plate I and right plate I, the width of the cavity I surrounded by the left plate I and the right plate I is 400mm, the right furnace core plate includes left plate II and right plate II, the width of the cavity II surrounded by the left plate II and the right plate II is 400mm, and the distance between the right plate I of the left furnace core plate and the left plate II of the right furnace core plate is 2900mm; the left plate I of the left furnace core plate, the right plate I of the left furnace core plate, the left plate II of the right furnace core plate and the right plate II of the right furnace core plate are composed of three detachable sections and are used to build furnace core wall I, furnace core wall II and furnace core wall III respectively; The wall thickness of the left furnace core plate and the right furnace core plate is 400mm, and the distance between the right plate of the left furnace core plate and the left plate of the right furnace core plate is 2900mm; Surrounding the furnace core wall with a width of 2.9 meters Surrounding the furnace core plate: taking the center axis of the conductive wall as a benchmark, surrounding the furnace core plate with a width of 2.9 meters, and fixing it with a clip, and supporting the furnace core plate with a plug plate at the four corners; (4) laying a cushion layer: laying a cushion layer in the area II; (5) installing crucible I: In the area II, the crucible I is vertically placed, the remaining space in the area II is filled with the resistance material I and then inserted, the calcined coke is laid in the cavities I and II to form the furnace core wall I, the graphitized coke is laid in the area I and area III to form the heat insulation layer I, and the crucible I, the resistance material I and the furnace core wall I are in the same height; Then the parts of the left plate I, the right plate I, the left plate II and the right plate II corresponding to the furnace core wall I are pulled out and removed respectively; (6) Installing the crucible II: In the area II, the crucible II is vertically placed on the crucible I, the remaining space in the area II is filled with the resistance material II and then inserted, the calcined coke is laid in the cavities I and II to form the furnace core wall II, the graphitized coke is laid in the area I and area III to form the heat insulation layer II, and the crucible II, the resistance material II and the furnace core wall II are in the same height; Then the parts of the left plate I, the right plate I, the left plate II and the right plate II corresponding to the furnace core wall II are pulled out and removed respectively; (7) Installing the crucible III: In the area II, the crucible III is vertically placed on the crucible II, the remaining space in the area II is filled with the resistance material III and then inserted, the calcined coke is laid in the cavities I and II to form the furnace core wall III, the graphitized coke is laid in the area I and area III to form the heat insulation layer III, and the crucible III, the resistance material III and the furnace core wall III are in the same height; Then the parts of the left plate I, the right plate I, the left plate II and the right plate II corresponding to the furnace core wall III are pulled out and removed respectively; In the above steps (5), (6) and (7), the layer spacing between the crucible I and the crucible II is 0, the layer spacing between the crucible II and the crucible III is 0, the spacing between the crucibles in each layer is 55-70 mm, and the shape of the crucible I, the crucible II and the crucible III is a cube; (8) Laying the top layer: the graphitized coke is laid on the crucible III to form the top layer; (9) Laying the exhaust layer: the exhaust cylinder is placed on the top layer, the calcined coke is laid to form the exhaust layer, and then the exhaust cylinder is taken out to form the exhaust hole; (10) Power supply; (11) Cooling and discharging.

2. The method for preparing a negative material for lithium ion batteries based on a square crucible according to claim 1, characterized in that, The carbon black layer meets the following requirements: ash content ≤0.5%, moisture content ≤0.5%, volatile content ≤1.2%, carbon content ≥98%, sulfur ≤0.5%, and resistivity ≥1800 μΩ·m. 3.The method for preparing a negative material for lithium ion batteries based on a square crucible according to claim 1, characterized in that, The heat preservation layer is laid at a distance of 180 mm from the lower edge of the graphite electrode, and the heat preservation layer is calcined coke with a particle size of 0-2 mm. 4.The method for preparing a negative material for lithium ion batteries based on a square crucible according to claim 1, characterized in that, The height of the cushion layer is 50 mm, and the cushion layer is calcined coke with a particle size of 8-12 mm.

5. The method for preparing a negative material for lithium ion batteries based on a square crucible according to claim 1, characterized in that, The resistance material I is calcined coke with a particle size of 3-8 mm, the resistance material II is calcined coke with a particle size of 8-16 mm, and the resistance material III is calcined coke with a particle size of 16-25 mm.

6. The method for preparing a negative material for lithium ion batteries based on a square crucible according to claim 1, characterized in that, The furnace core wall I, the furnace core wall II and the furnace core wall III are all calcined coke with a particle size of 0-2 mm.

7. The method for preparing a negative material for lithium ion batteries based on a square crucible according to claim 1, characterized in that, The heat insulation layer I, the heat insulation layer II and the heat insulation layer III are all graphitized coke with a particle size of 0-3 mm. 8.The method for preparing a negative material for lithium ion batteries based on a square crucible according to claim 1, characterized in that, The top layer is graphitized coke with a height of 100 mm and a particle size of 8-12 mm. 9.The method for preparing a negative material for lithium ion batteries based on a square crucible according to claim 1, characterized in that, The exhaust layer is calcined coke with a height of 50 mm and a particle size of 3-8 mm.

10. The method for preparing a negative material for lithium ion batteries based on a square crucible according to claim 1, characterized in that, The power curve during the power transmission in step (9) is as follows: preheating power is 0-3000 kW, preheating rising power is 500 kW / h; first stage power is 3000-7000 kW, first stage rising power is 200 kW / h; second stage power is 7000-8000 kW, second stage rising power is 500 kW / h; third stage power is 8000-22000 kW, third stage rising power is 2000 kW / h, and 22000 kW is maintained for 10 h after reaching 22000 kW.

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