Carbonization treatment method and carbonization furnace for lithium ion battery negative electrode material

Abstract

The carbonization treatment method of lithium ion battery negative electrode material of the present invention comprises the following steps: a. laying a heat insulation pad in a carbonization furnace; b. abutting one end of a first conductive graphite felt against the inner wall of a furnace head of the carbonization furnace and separating the other end from the inner wall of a furnace tail of the carbonization furnace; c. evenly placing graphite crucibles filled with a first negative electrode material at the same interval on the first conductive graphite felt, and filling a second negative electrode material between the graphite crucible and the side wall of the carbonization furnace; d. laying a second conductive graphite felt on the graphite crucible layer, abutting one end of the second conductive graphite felt against the inner wall of the furnace tail of the carbonization furnace and separating the other end from the inner wall of the furnace head of the carbonization furnace; e. laying a furnace roof on the second conductive graphite felt; f. supplying power to the carbonization furnace; g. monitoring the temperature field of the carbonization furnace; h. stopping power supply, dissipating heat and cooling; i. completing the carbonization treatment of the first negative electrode material, and collecting the second negative electrode material as the first negative electrode material for the next carbonization treatment.

Description

Technical Field

[0001] The invention relates to a carbonization treatment method for negative electrode materials of lithium ion batteries and also relates to a carbonization furnace. Background Art

[0002] In the industrial production of carbon negative electrode materials for lithium-ion batteries, powdered carbon intermediates are often subjected to heat treatment at 900℃-1400℃, which is usually called carbonization treatment in the industry, and the corresponding equipment is called a carbonization furnace. After carbonization treatment, some types of carbon intermediates can be used or sold directly as negative electrode materials, while some types of carbon intermediates need to be graphitized at a higher temperature before they can be used. Graphitization treatment is a high-energy consumption and high-cost production process. Pre-carbonization treatment of them before graphitization will significantly increase the material packing density, increase the output of a single graphitization furnace, and reduce the production cost of graphitization treatment.

[0003] The traditional carbonization treatment device inserts a heating plate into the negative electrode material, energizes both ends of the heating plate, heats the heating plate, and then heats and carbonizes the negative electrode material on both sides of the heating plate. However, due to the thickness of the negative electrode material, the degree of carbonization of the negative electrode material at different thickness positions is different, and a large range of negative electrode materials are carbonized at the same time, which consumes a lot of energy and takes a long time. In addition, due to its rigidity, the heating plate is not in close contact with the negative electrode material, resulting in low carbonization efficiency. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a carbonization treatment method for lithium ion battery negative electrode materials with lower energy consumption, shorter cycle and higher efficiency, and also provide a carbonization furnace for implementing the method.

[0005] In order to solve the above technical problems, the carbonization treatment method of the negative electrode material of a lithium ion battery of the present invention comprises the following steps:

[0006] a. Lay heat insulation pads in the carbonization furnace;

[0007] b. Laying a first conductive graphite felt on the heat insulation pad, with one end of the first conductive graphite felt abutting against the inner wall of the furnace head of the carbonization furnace and the other end being spaced apart from the inner wall of the furnace tail of the carbonization furnace;

[0008] c. Place graphite crucibles filled with the first negative electrode material evenly at the same intervals on the first conductive graphite felt, open the graphite crucible upward, and fill the second negative electrode material between the graphite crucibles and between the graphite crucibles and the side wall of the carbonization furnace to form a graphite crucible layer;

[0009] d. Laying a second conductive graphite felt on the graphite crucible layer, covering the graphite crucible opening of the graphite crucible layer, abutting one end of the second conductive graphite felt against the inner wall of the tail of the carbonization furnace and the other end of the second conductive graphite felt with the inner wall of the furnace head of the carbonization furnace spaced apart;

[0010] e. Laying a refractory fiber felt roof with an exhaust port on the second conductive graphite felt;

[0011] f. Supply electricity to the carbonization furnace so that the current passes through the furnace head, the first conductive graphite felt, the graphite crucible layer, the second conductive graphite felt, and the furnace tail in sequence to electrically heat the carbonization furnace;

[0012] g. Use platinum-rhodium thermocouples at the temperature measuring points of the carbonization furnace to monitor the temperature field of the carbonization furnace;

[0013] h. When the temperature field reaches the process requirements, stop supplying power, remove the furnace roof, and dissipate heat to cool down;

[0014] i. Take out the second conductive graphite felt, graphite crucible, first conductive graphite felt and thermal insulation pad, complete the carbonization treatment of the first negative electrode material, and collect the second negative electrode material as the first negative electrode material for the next carbonization treatment.

[0015] After step d, steps a to d are repeated to form a multi-layer graphite crucible in the carbonization furnace.

[0016] The method also includes the steps of collecting waste gas from the exhaust port on the furnace top and performing harmless treatment.

[0017] The method also includes the steps of arranging two layers of furnace tops and staggering the exhaust ports of the two layers of furnace tops.

[0018] The method also includes the steps of reserving a first abutting portion at one end of the first conductive graphite felt for parallel abutment with the inner wall of the furnace head, and reserving a second abutting portion at one end of the second conductive graphite felt for parallel abutment with the inner wall of the furnace tail.

[0019] In order to solve the above technical problems, the carbonization furnace of the present invention comprises a furnace head, a furnace tail, a furnace top, a furnace bottom, a furnace side wall, a heat-insulating pad, a first conductive graphite felt, a graphite crucible and a second conductive graphite felt; the furnace head and the furnace tail are both built of graphite bricks supplemented with a conductive adhesive; the outer walls of the furnace head and the furnace tail are respectively provided with graphite electrodes; the furnace bottom and the furnace side walls are both built of insulating refractory bricks supplemented with refractory cement; a cubic furnace cavity is formed between the furnace head, the furnace tail, the furnace top, the furnace bottom and the furnace side walls; the heat-insulating pad is horizontally laid on the bottom wall of the furnace cavity; the first conductive graphite felt is laid on the heat-insulating pad in the furnace cavity, one end of the first conductive graphite felt is in contact with the inner wall of the furnace head and the other end is separated from the inner wall of the furnace tail; the graphite crucible The graphite crucibles are evenly placed on the first conductive graphite felt in the furnace chamber at the same interval, and the opening of the graphite crucible faces upward; the gaps between the graphite crucibles and between the graphite crucibles and the furnace side walls are used for preliminary carbonization of the negative electrode material, and the inner cavity of the graphite crucible is used for further carbonization of the negative electrode material; the second conductive graphite felt is laid on the graphite crucible in the furnace chamber and covers the opening of the graphite crucible, one end of the second conductive graphite felt is in contact with the inner wall of the furnace tail and the other end is spaced apart from the inner wall of the furnace head; the furnace top is covered on the second conductive graphite felt, and the furnace top is a refractory fiber felt provided with an exhaust port; the carbonization furnace is provided with a plurality of temperature measuring points, and the temperature measuring points are provided with platinum-rhodium thermocouples, and the platinum-rhodium thermocouples are connected to a temperature field monitoring system.

[0020] The heat-insulating pad, the first conductive graphite felt, the graphite crucible and the second conductive graphite felt are sequentially arranged from bottom to top to form a set of carbonization treatment layers, and a plurality of sets of carbonization treatment layers are arranged in the furnace chamber from bottom to top.

[0021] A gas collecting hood is also arranged above the exhaust port of the furnace top, the gas collecting hood is connected to an induced draft fan, and the induced draft fan is connected to an exhaust gas purification system.

[0022] The furnace roof is provided with two layers, and the exhaust ports of the two layers of the furnace roof are staggered with each other.

[0023] One end of the first conductive graphite felt is provided with a first abutting portion for abutting parallel to the inner wall of the furnace head, and one end of the second conductive graphite felt is provided with a second abutting portion for abutting parallel to the inner wall of the furnace tail, the first abutting portion faces upward, and the second abutting portion faces downward.

[0024] By adopting the method and structure of the present invention, two pieces of conductive graphite felt are used in the carbonization furnace to energize the graphite crucible from the upper and lower ends respectively. The conductive graphite felt has a smaller resistance, so that the graphite crucible is fully heated between the upper and lower conductive graphite felts. The conductive graphite felt has stable performance, can be reused, and will not mix with the negative electrode material to be carbonized; the second negative electrode material to be carbonized is filled in the gap outside the graphite crucible, and the second negative electrode material can fully absorb the waste heat in the carbonization furnace for preliminary carbonization, which is more energy-saving; the second negative electrode material in the previous carbonization process is used as the first negative electrode material in this carbonization process to fill the graphite crucible with heat and carbonize, and the carbonization cycle is shorter; the top opening of the graphite crucible is covered with the second conductive graphite felt, which can not only prevent the first negative electrode material in the graphite crucible from mixing with the second negative electrode material , the graphite crucible can be made more air permeable, and the second conductive graphite felt can be in contact with the first negative electrode material in the graphite crucible and energized, so that the first negative electrode material itself is energized to actively generate heat and carbonize, with higher carbonization efficiency and more uniform carbonization; the graphite crucible is evenly arranged at the same interval between the two layers of conductive graphite felt, and multiple sets of carbonization treatment layers are laid from bottom to top in the carbonization furnace, so that the carbonization output each time is larger; the furnace top is double-layered, and the exhaust ports of the two layers of furnace top are staggered, which can reduce heat loss and better keep warm; a first abutting portion for parallel abutting against the inner wall of the furnace head is reserved at one end of the first conductive graphite felt, and a second abutting portion for parallel abutting against the inner wall of the furnace tail is reserved at one end of the second conductive graphite felt, so that the first conductive graphite felt is more closely connected to the furnace head, and the second conductive graphite felt is more closely connected to the furnace tail. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a structural schematic diagram of the carbonization furnace of the present invention.

[0026] In the figure: 1-graphite electrode, 2-furnace head, 3-furnace side wall, 4-furnace bottom, 5-thermal insulation pad, 6-first conductive graphite felt, 7-graphite crucible, 8-second conductive graphite felt, 9-furnace tail, 10-graphite electrode, 11-exhaust port, 12-furnace top. DETAILED DESCRIPTION

[0027] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] The carbonization treatment method of the negative electrode material of a lithium ion battery of the present invention comprises the following steps:

[0029] a. Lay heat insulation pads in the carbonization furnace; the heat insulation pads can be made of ceramic fiber refractory wool or refractory insulation bricks, which not only keep heat and insulate, but also have better adaptability and cushioning properties.

[0030] b. Lay the first conductive graphite felt on the heat insulation pad, with one end of the first conductive graphite felt in contact with the inner wall of the furnace head of the carbonization furnace and the other end separated from the inner wall of the furnace tail of the carbonization furnace; the first conductive graphite felt is used to connect the current of the furnace head to the bottom of the graphite crucible. The conductive graphite felt can be laid as a whole sheet or multiple sheets overlapped end to end; the conductive graphite felt is thin, occupies little space, can be elastically deformed well, and is convenient for close connection with the graphite crucible and the negative electrode material.

[0031] c. Graphite crucibles filled with the first negative electrode material are evenly placed on the first conductive graphite felt at the same intervals, the opening of the graphite crucible is facing upward, and the second negative electrode material is filled between the graphite crucibles and between the graphite crucible and the side wall of the carbonization furnace to form a graphite crucible layer; the resistance of the graphite crucible is greater than the resistance of the first conductive graphite felt and the resistance of the second conductive graphite felt, and the average carbonization degree of the first negative electrode material is higher than the average carbonization degree of the second negative electrode material, which is convenient for the first negative electrode material to be heated and carbonized preferentially; the top of the graphite crucible is open, which is not only convenient for air permeability, but also convenient for the first negative electrode material to directly contact and energize the second conductive graphite felt, so that the first negative electrode material can not only be heated and carbonized by the graphite crucible, but also can actively heat and carbonize by energizing itself, so that the carbonization of the first negative electrode material is more sufficient and more uniform; the second negative electrode material can play the role of filling, supporting and heat preservation, and at the same time fully absorb the heat radiated outward by the graphite crucible, the first conductive graphite felt and the second conductive graphite felt for preliminary carbonization, which is more energy-saving.

[0032] d. Lay a second conductive graphite felt on the graphite crucible layer, cover the graphite crucible opening of the graphite crucible layer, support the graphite crucible and the second negative electrode material filled on the side of the graphite crucible, and abut one end of the second conductive graphite felt against the inner wall of the furnace tail of the carbonization furnace and the other end is separated from the inner wall of the furnace head of the carbonization furnace; the second conductive graphite felt is used to connect the current at the furnace tail to the top of the graphite crucible. The material and conductive properties of the second conductive graphite felt are the same as those of the first conductive graphite felt; the second conductive graphite felt covers the top opening of the graphite crucible, which can prevent the second negative electrode material from mixing with the first negative electrode material in the crucible, so that the first negative electrode material is independently carbonized in the graphite crucible, and the carbonization degree of the first negative electrode material is more uniform.

[0033] e. A refractory fiber felt furnace roof with an exhaust port is laid on the second conductive graphite felt; the refractory fiber felt can be graphite felt, carbon felt, or ceramic fiber wool, etc. The refractory fiber felt has good thermal insulation performance and is lightweight; the exhaust port is used to discharge volatile gases generated during the heating and carbonization process of the negative electrode material.

[0034] f. Supply power to the carbonization furnace, preferably direct current, and apply a variable voltage according to the carbonization demand, so that the current passes through the furnace head, the first conductive graphite felt, the graphite crucible layer, the second conductive graphite felt, and the furnace tail in sequence to electrically heat the carbonization furnace; the current mainly passes through the furnace head, the first conductive graphite felt, the graphite crucible layer, the second conductive graphite felt, and the furnace tail, and then passes through the first negative electrode material, and the current passing through the second negative electrode material is the least; the graphite crucible is heated first, and the first negative electrode material in the graphite crucible is carbonized first.

[0035] g. Use platinum-rhodium thermocouples at the temperature measuring points of the carbonization furnace to monitor the temperature field of the carbonization furnace; the temperature field monitoring system is connected to the platinum-rhodium thermocouples to collect the temperature field data of the carbonization furnace; the temperature measuring points are used to monitor the temperature of the graphite crucible, the temperature of the conductive graphite felt, the temperature of the negative electrode material, and the temperature of the inner wall of the furnace.

[0036] h. When the temperature field reaches the process requirements, stop supplying electricity, remove the furnace roof, and dissipate heat to cool down;

[0037] i. Take out the second conductive graphite felt, graphite crucible, first conductive graphite felt, thermal insulation pad and second negative electrode material layer by layer from top to bottom, take out the first negative electrode material from the graphite crucible, complete the carbonization treatment of the first negative electrode material, take out the second negative electrode material from the carbonization furnace, and collect the second negative electrode material as the first negative electrode material for the next carbonization treatment.

[0038] After step d, steps a to d are repeated to form a multi-layer graphite crucible layer in the carbonization furnace. That is, a first conductive graphite felt and a heat-insulating pad are provided at the bottom of each graphite crucible layer and a second conductive graphite felt is provided at the top, and each graphite crucible layer is heated and carbonized relatively independently. Multi-layer graphite crucible layers are provided in the carbonization furnace for carbonization, so that the single carbonization output of the carbonization furnace is larger. In the structure of the multi-layer graphite crucible layer, due to the filling of the second negative electrode material, it can also play a better supporting and stabilizing role, and can reduce collapse.

[0039] It also includes the steps of collecting exhaust gas from the exhaust port on the top of the furnace and treating it harmlessly. The harmless treatment mainly includes cyclone dust removal, water washing and cooling, etc., which can reduce air pollution and be more environmentally friendly.

[0040] The method also includes the steps of setting two layers of furnace tops and staggering the exhaust ports of the two layers of furnace tops, so as to retain some dust and avoid the carbonization furnace door being wide open, thereby reducing heat loss.

[0041] The method further includes the steps of reserving a first abutting portion at one end of the first conductive graphite felt for parallel abutment with the inner wall of the furnace head, and reserving a second abutting portion at one end of the second conductive graphite felt for parallel abutment with the inner wall of the furnace tail. The first abutting portion at the end of the first conductive graphite felt abuts parallel to the inner wall of the furnace head, and the second abutting portion at the end of the second conductive graphite felt abuts parallel to the inner wall of the furnace tail, so that the contact surface is larger, the electrical performance is better and more stable, and as a reserve for abutment, the disconnection of the abutment due to the sinking of the second negative electrode material can be avoided.

[0042] like Figure 1 As shown, the carbonization furnace for realizing carbonization treatment of negative electrode materials of lithium-ion batteries of the present invention comprises a furnace head, a furnace tail, a furnace top, a furnace bottom, a furnace side wall, a heat insulation pad, a first conductive graphite felt, a graphite crucible and a second conductive graphite felt. The furnace head and the furnace tail are located at both ends of the carbonization furnace, the furnace side walls are located on both sides of the carbonization furnace, the furnace top is located at the top of the carbonization furnace, and the furnace top is located at the bottom of the carbonization furnace. The furnace head, the furnace tail and the furnace side walls are all fixedly connected to the furnace bottom. The graphite crucible is a rectangular or cylindrical can with a circular can mouth at the top.

[0043] The furnace head and furnace tail are built with graphite bricks supplemented with conductive adhesives; the inner walls of the furnace head and furnace tail are conductive; the outer walls of the furnace head and furnace tail are respectively provided with graphite electrodes for connecting the power supply; the furnace bottom and furnace side walls are built with insulating refractory bricks supplemented with refractory cement; a cubic furnace cavity is formed between the furnace head, furnace tail, furnace top, furnace bottom and furnace side walls;

[0044] The bottom layer of thermal insulation pad is laid horizontally on the bottom wall of the furnace cavity; the thermal insulation pad can be made of ceramic fiber refractory wool or refractory insulation bricks, which not only keeps heat and insulates, but also has better adaptability and cushioning properties.

[0045] The first conductive graphite felt is laid on the heat insulation pad in the furnace cavity, one end of the first conductive graphite felt is in contact with the inner wall of the furnace head and the other end is separated from the inner wall of the furnace tail; the first conductive graphite felt is used to connect the current of the furnace head to the bottom of the graphite crucible. The conductive graphite felt can be laid in one piece or in multiple pieces overlapped end to end; the conductive graphite felt is thin, occupies little space, can be elastically deformed well, and is convenient for close connection with the graphite crucible and the negative electrode material.

[0046] The graphite crucibles are evenly placed on the first conductive graphite felt in the furnace chamber at the same intervals, with the opening of the graphite crucible facing upward; the gaps between the graphite crucibles and between the graphite crucible and the furnace side wall are used for the preliminary carbonization of the negative electrode material, and the inner cavity of the graphite crucible is used for further carbonization of the negative electrode material; when in use, the negative electrode material is filled inside and outside the graphite crucible, but the negative electrode material filled in the graphite crucible is the negative electrode material filled in the gap outside the graphite crucible during the last carbonization process. The resistance of the graphite crucible is greater than the resistance of the first conductive graphite felt and the resistance of the second conductive graphite felt. The average carbonization degree of the first negative electrode material in the graphite crucible is higher than the average carbonization degree of the second negative electrode material outside the graphite crucible, which facilitates the first negative electrode material to be heated and carbonized preferentially; the top of the graphite crucible is open, which is not only convenient for air permeability, but also convenient for the first negative electrode material to directly contact and energize with the second conductive graphite felt, so that the first negative electrode material can not only be heated and carbonized by the graphite crucible, but also can actively generate heat and carbonize by energizing itself, so that the carbonization of the first negative electrode material is more sufficient and more uniform; the second negative electrode material can play the role of filling, supporting and heat preservation, and at the same time fully absorb the heat radiated outward by the graphite crucible, the first conductive graphite felt and the second conductive graphite felt for preliminary carbonization, which is more energy-saving.

[0047] The second conductive graphite felt is laid on the graphite crucible in the furnace chamber and covers the opening of the graphite crucible. One end of the second conductive graphite felt abuts against the inner wall of the furnace tail and the other end is separated from the inner wall of the furnace head. The second conductive graphite felt is used to connect the current of the furnace tail to the top of the graphite crucible. The material and conductive properties of the second conductive graphite felt are the same as those of the first conductive graphite felt. The second conductive graphite felt covers the top opening of the graphite crucible, which can prevent the second negative electrode material from mixing with the first negative electrode material in the crucible, so that the first negative electrode material is independently carbonized in the graphite crucible, and the carbonization degree of the first negative electrode material is more uniform.

[0048] The furnace top is covered on the second conductive graphite felt, and the furnace top is a refractory fiber felt with an exhaust port; the refractory fiber felt can be graphite felt, carbon felt or ceramic fiber wool, etc.; the refractory fiber felt has good thermal insulation performance and is light in weight; the exhaust port is used to discharge the volatile gas generated by the negative electrode material during the heating and carbonization process. The carbonization furnace is provided with multiple temperature measuring points, which are respectively set on the side and the top. The temperature measuring points are provided with platinum-rhodium thermocouples for collecting the temperature field data of the carbonization furnace, and the platinum-rhodium thermocouples are connected to the temperature field monitoring system.

[0049] When in use, power is supplied to the carbonization furnace, preferably direct current, and a variable voltage is applied according to the carbonization requirements, so that the current passes through the furnace head, the first conductive graphite felt, the graphite crucible layer, the second conductive graphite felt, and the furnace tail in sequence, and the carbonization furnace is heated electrically; the current mainly passes through the furnace head, the first conductive graphite felt, the graphite crucible layer, the second conductive graphite felt, and the furnace tail, and then passes through the first negative electrode material, and the current passing through the second negative electrode material is the least; the graphite crucible is heated first, and the first negative electrode material in the graphite crucible is carbonized first. When the temperature field reaches the process requirements, stop supplying power, remove the furnace top, dissipate heat and cool down; take out the second conductive graphite felt, graphite crucible, first conductive graphite felt, thermal insulation pad, and second negative electrode material layer by layer from top to bottom, take out the first negative electrode material from the graphite crucible, complete the carbonization treatment of the first negative electrode material, take out the second negative electrode material from the carbonization furnace, and collect the second negative electrode material as the first negative electrode material for the next carbonization treatment.

[0050] like Figure 1 As shown, the heat insulation pad, the first conductive graphite felt, the graphite crucible and the second conductive graphite felt are sequentially arranged from bottom to top to form a set of carbonization treatment layers, and multiple sets of carbonization treatment layers are arranged from bottom to top in the furnace chamber. Each set of carbonization treatment layers is heated and carbonized relatively independently. Multiple sets of carbonization treatment layers are arranged in the carbonization furnace for carbonization treatment, so that the single carbonization treatment output of the carbonization furnace is larger. In the structure of the multi-layer carbonization treatment layer, due to the filling and support of the second negative electrode material, the stability is better and the collapse can be reduced.

[0051] like Figure 1 As shown, a gas collection hood is also arranged above the exhaust port on the furnace roof, the gas collection hood is connected to an induced draft fan, and the induced draft fan is connected to an exhaust gas purification system. The exhaust gas purification system includes a cyclone dust collector, a water washing and cooling center and other equipment, which can reduce air pollution and be more environmentally friendly.

[0052] like Figure 1 As shown, the furnace top is provided with two layers and the exhaust ports of the two layers of the furnace top are staggered with each other, which can retain some dust and avoid the carbonization furnace door being wide open, thereby reducing heat loss.

[0053] like Figure 1 As shown, one end of the first conductive graphite felt is provided with a first abutting portion for parallel abutment with the inner wall of the furnace head, and one end of the second conductive graphite felt is provided with a second abutting portion for parallel abutment with the inner wall of the furnace tail, the first abutting portion faces upward, and the second abutting portion faces downward. Parallel abutment makes the contact surface larger, and the electrical performance is better and more stable. The first abutting portion and the second abutting portion are reserved for abutment, which can avoid the disconnection of abutment due to the sinking of the second negative electrode material.

Claims

1. A method for carbonizing negative electrode materials of lithium ion batteries, characterized in that The steps include: a. Lay heat insulation pads in the carbonization furnace; b. Laying a first conductive graphite felt on the heat insulation pad, with one end of the first conductive graphite felt abutting against the inner wall of the furnace head of the carbonization furnace and the other end being spaced apart from the inner wall of the furnace tail of the carbonization furnace; c. Place graphite crucibles filled with the first negative electrode material evenly at the same intervals on the first conductive graphite felt, open the graphite crucible upward, and fill the second negative electrode material between the graphite crucibles and between the graphite crucibles and the side wall of the carbonization furnace to form a graphite crucible layer; d. Laying a second conductive graphite felt on the graphite crucible layer, covering the graphite crucible opening of the graphite crucible layer, abutting one end of the second conductive graphite felt against the inner wall of the tail of the carbonization furnace and the other end of the second conductive graphite felt with the inner wall of the furnace head of the carbonization furnace spaced apart; e. Laying a refractory fiber felt roof with an exhaust port on the second conductive graphite felt; f. Supply electricity to the carbonization furnace so that the current passes through the furnace head, the first conductive graphite felt, the graphite crucible layer, the second conductive graphite felt, and the furnace tail in sequence to electrically heat the carbonization furnace; g. Use platinum-rhodium thermocouples at the temperature measuring points of the carbonization furnace to monitor the temperature field of the carbonization furnace; h. When the temperature field reaches the process requirements, stop supplying power, remove the furnace roof, and dissipate heat to cool down; i. Take out the second conductive graphite felt, graphite crucible, first conductive graphite felt and thermal insulation pad, complete the carbonization of the first negative electrode material, collect the second negative electrode material as the first negative electrode material for the next carbonization treatment; The method also includes the steps of arranging two layers of furnace tops and staggering the exhaust ports of the two layers of furnace tops.

2. The method for carbonizing negative electrode materials of lithium ion batteries according to claim 1, characterized in that: After step d, steps a to d are repeated to form a multi-layer graphite crucible in the carbonization furnace.

3. The method for carbonizing negative electrode materials of lithium ion batteries according to claim 1, characterized in that: The method also includes the steps of collecting waste gas from the exhaust port on the furnace top and performing harmless treatment.

4. The method for carbonizing negative electrode materials of lithium ion batteries according to claim 1, characterized in that: The method also includes the steps of reserving a first abutting portion at one end of the first conductive graphite felt for parallel abutment with the inner wall of the furnace head, and reserving a second abutting portion at one end of the second conductive graphite felt for parallel abutment with the inner wall of the furnace tail.

5. A carbonization furnace for implementing the method of claim 1, characterized in that: It includes a furnace head, a furnace tail, a furnace top, a furnace bottom, a furnace side wall, a heat insulation pad, a first conductive graphite felt, a graphite crucible and a second conductive graphite felt; The furnace head and furnace tail are both built with graphite bricks supplemented with conductive adhesives; the outer side walls of the furnace head and furnace tail are respectively provided with graphite electrodes; the furnace bottom and furnace side walls are both built with insulating refractory bricks supplemented with refractory cement; a cubic furnace cavity is formed between the furnace head, furnace tail, furnace top, furnace bottom and furnace side walls; The heat insulation pad is horizontally laid on the bottom wall of the furnace cavity; The first conductive graphite felt is laid on the heat insulation pad in the furnace cavity, one end of the first conductive graphite felt is in contact with the inner wall of the furnace head and the other end is separated from the inner wall of the furnace tail; The graphite crucibles are evenly placed on the first conductive graphite felt in the furnace chamber at the same intervals, and the opening of the graphite crucible faces upward; the gaps between the graphite crucibles and between the graphite crucible and the furnace side wall are used for preliminary carbonization of the negative electrode material, and the inner cavity of the graphite crucible is used for further carbonization of the negative electrode material; The second conductive graphite felt is laid on the graphite crucible in the furnace chamber and covers the opening of the graphite crucible, one end of the second conductive graphite felt is in contact with the inner wall of the furnace tail and the other end is spaced apart from the inner wall of the furnace head; The furnace top is covered on the second conductive graphite felt, and the furnace top is a refractory fiber felt provided with an exhaust port; the carbonization furnace is provided with a plurality of temperature measuring points, and the temperature measuring points are provided with platinum-rhodium thermocouples, and the platinum-rhodium thermocouples are connected to a temperature field monitoring system.

6. The carbonization furnace according to claim 5, characterized in that: The heat-insulating pad, the first conductive graphite felt, the graphite crucible and the second conductive graphite felt are sequentially arranged from bottom to top to form a set of carbonization treatment layers, and a plurality of sets of carbonization treatment layers are arranged in the furnace chamber from bottom to top.

7. The carbonization furnace according to claim 5, characterized in that: A gas collecting hood is also provided above the exhaust port of the furnace top, the gas collecting hood is connected to an induced draft fan, and the induced draft fan is connected to an exhaust gas purification system.

8. The carbonization furnace according to claim 5, characterized in that: The furnace roof is provided with two layers, and the exhaust ports of the two layers of the furnace roof are staggered with each other.

9. The carbonization furnace according to claim 5, characterized in that: One end of the first conductive graphite felt is provided with a first abutting portion for abutting parallel to the inner wall of the furnace head, and one end of the second conductive graphite felt is provided with a second abutting portion for abutting parallel to the inner wall of the furnace tail, the first abutting portion faces upward, and the second abutting portion faces downward.

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