Process for generating isotropic carbonaceous precursor aggregates
A novel process for producing isotropic carbonaceous precursor aggregates using a water-soluble binder at room temperature addresses scalability and health risks, enabling efficient, low-cost production of high-density graphite electrodes for lithium-ion batteries and electric vehicles.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- レイン カーボン ジャーマニー ジーエムビーエイチ
- Filing Date
- 2024-06-07
- Publication Date
- 2026-06-16
AI Technical Summary
Conventional methods for producing isotropic graphite aggregates are costly, require complex high-temperature reactors, and pose health risks due to carcinogenic pitch binders, limiting scalability and efficiency.
A process involving mixing coke particles with a water-soluble temporary binder, followed by drying and carbonizing, eliminates the need for high-temperature reactors and reduces health risks by using a volatile binder that decomposes during carbonization, forming high-density, isotropic aggregates.
The process achieves scalable, low-cost production of isotropic carbonaceous precursor aggregates with reduced health hazards, suitable for high-density isotropic graphite electrodes in lithium-ion batteries and electric vehicles.
Smart Images
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Abstract
Description
Technical Field
[0001] The present invention generally relates to a process for producing carbonaceous precursor aggregates, particularly isotropic carbonaceous precursor aggregates. These aggregates can be particularly useful as precursors for isotropic graphite.
[0002] Furthermore, the present invention also relates to a process for producing an isotropic graphite electrode material for battery electrodes, particularly for Li-Ion batteries and EV (electric vehicle) batteries.
Background Art
[0003] The negative electrodes of lithium-ion batteries mainly contain isotropic natural graphite and / or synthetic graphite. Isotropic synthetic graphite materials are regarded as premium negative electrode materials particularly in Li-ion batteries because they enable improved charge and discharge performance and cycle stability with isotropic synthetic graphite.
[0004] Furthermore, in order to increase the energy density of battery cells, particles of silicon, silicon oxide, or silicon alloy are often added to negative battery electrodes in the form of secondary particle composites with graphite or carbon.
[0005] Conventionally, in order to obtain an advantageous structure of porous electrode materials, fine graphite primary particles are aggregated to form equiangular-shaped aggregates. These isotropic synthetic graphite aggregates are produced from coke by aggregation of fine coke with molten coal tar pitch and / or petroleum pitch. The carbon component is homogeneously mixed with a finely pulverized solid pitch binder, and the mixture is further processed in a high-temperature reactor where the coke particles are aggregated by molten pitch.
[0006] The common drawbacks of the high-temperature flocculation process described above are that it requires complex high-temperature reactors and upscaling is only possible to a certain limit. Due to the long residence time in the heat treatment process, upscaling requires operating several reactors in parallel to obtain an industrially suitable quantity, as the flocculation and initial heat treatment processes are carried out in the same apparatus and are not separated from each other. Clearly, such upscaling significantly increases the cost of the flocculated product. Furthermore, in larger thermal batch reactors where the powder is fluidized with the assistance of screw or mother mixer type devices, high temperature gradients and temperature uniformity become problematic.
[0007] A second drawback of the conventional process described above is that the pitch binder needs to be precisely ground, and because some of the polyaromatic hydrocarbons it contains are carcinogenic, special measures are required for handling and containing the pitch powder.
[0008] Another conventional method for producing isometric aggregates of graphite particles is spray granulation (as proposed in US2018 / 0183060A1). However, this method is not very desirable due to the high cost of the spray drying process. In addition, the particles formed during the spray drying process are often hollow and exhibit relatively low density and mechanical strength when compressed.
[0009] Considering the above, the general object of the present invention is to provide a process for producing isotropic carbonaceous precursor aggregates that does not require complex equipment and processing and has lower processing costs.
[0010] Another objective of the present invention is to provide a process for generating isotropic carbonaceous precursor aggregates that can be more easily scaled to industrial scale.
[0011] Furthermore, it is also an object of the present invention to provide a process for producing isotropic carbonaceous precursor aggregates that have a lower risk of being involved in the carcinogenicity of polyaromatic hydrocarbons contained in the pitch binder.
[0012] Furthermore, an object of the present invention is also to provide an advantageous process for producing isotropic graphite electrode materials for battery electrodes, particularly porous electrode materials, and even more particularly for Li-ion batteries, EV (electric vehicle) batteries, and stationary batteries for battery energy storage. [Overview of the project]
[0013] The present invention provides a process for generating isotropic carbonaceous precursor aggregates, the process being i. A step of providing coke particles with an average particle size of less than 50 μm, wherein the particles have a volatile substance (VM) content of 4% to 20% by weight, ii. A step of mixing coke particles with water and a water-soluble temporary binder, thereby causing the coke particles to aggregate within the mixture. iii. A step of drying the mixture at least partially, iv. A step of carbonizing the mixture, and
[0014] Furthermore, the present invention provides a process for producing isotropic graphite electrode materials for battery electrodes, particularly for lithium-ion batteries, the process comprising a process for producing isotropic carbonaceous precursor aggregates according to the present invention, and further a process for graphitizing the aggregates to form an electrode material. [Modes for carrying out the invention]
[0015] The present invention relates to the production of carbonaceous precursor aggregates having an average aggregate particle size of less than 2000 microns, preferably less than 1000 microns, high isotropy, high density, low BET specific surface area, and low porosity. The aggregates can be used as precursors for the production of isotropic graphite-like electrode materials used in lithium-ion batteries, particularly in batteries for electric vehicles (EVs) or battery energy storage applications. The carbonaceous aggregates consist of primary coke particles randomly oriented in a secondary particle structure.
[0016] In relation to the present invention, an isotropic aggregate is understood as an aggregate in which primary particles are randomly oriented, resulting in a high degree of isotropy within the aggregate and a high degree of uniformity in physical properties and characteristics in all directions of the aggregate.
[0017] According to the present invention, the process for generating isotropic carbonaceous precursor aggregates is: i. A step of providing coke particles with an average particle size of less than 50 μm, wherein the particles have a volatile substance (VM) content of 4% to 20% by weight, ii. A step of mixing coke particles with water and a water-soluble temporary binder, thereby causing the coke particles to aggregate within the mixture. iii. A step of drying the mixture at least partially, iv. A step of carbonizing the mixture, and
[0018] Coke particles with an average particle size of less than 50 μm can be obtained by applying a milling process. Preferably, the coke particles have an average particle size of 1 to 20 μm.
[0019] According to the present invention, the coke particles may be uncalcined coke particles.
[0020] In one embodiment, the coke particles may be green needle coke, or other forms of green petroleum coke, preferably green petroleum coke having a sulfur level of less than 2% by weight, or pitch coke. In addition to the green or unfired state, needle coke, petroleum coke, or pitch coke may also be used up to a certain amount in a fired state.
[0021] In another embodiment of the present invention, coke particles can be mixed with other carbonaceous materials, such as natural or synthetic graphite, calcined petroleum coke powder, carbonaceous additives, carbonaceous waste, recycled materials, or combinations thereof. Recycled materials may include recycled graphite.
[0022] In one embodiment of the present invention, the concentration of uncalcined coke particles in the total mixture of primary particles can be at least 40% by weight, preferably at least 50% by weight, and even more preferably at least 60% by weight. Those skilled in the art will understand that the minimum required concentration of uncalcined coke particles in the total mixture of primary particles depends on its VM content.
[0023] Other additives can be nano-sized and micron-sized metal silicon, silicon oxide, tin or aluminum metal particles, or combinations thereof.
[0024] Preferably, the coke particles can have an ash content of less than 5000 ppm, more preferably less than 2000 ppm.
[0025] Preferably, the coke particles, particularly the uncalcined coke particles, can have a volatile matter (VM) level of 4% to 20% by weight, preferably 5% to 18% by weight, preferably 6% to 15% by weight. Comparing the carbon content of the coke particles with the carbon content of the pitch-based product, those skilled in the art will understand that a VM level of 4% to 20% is comparable to the coking value of 80 to 95% of ALCAN.
[0026] In one embodiment, the water-soluble temporary binder added in the mixing and agglomeration steps can include any suitable water-soluble natural or synthetic polymer such as starch, sugar, lignosulfonate, humin, polyvinyl acetate (PVA), carboxymethyl cellulose (CMC), citric acid, methyl cellulose or carboxymethyl cellulose (CMC) reacted with hemicellulose, or derivatives thereof.
[0027] Those skilled in the art will understand that, in relation to the present invention, the term “temporary” means that the water-soluble temporary binder is selected based on its ability to volatilize at least partially, preferably substantially completely, during the carbonization process. Volatilization refers to the process of (at least partially) evaporating the temporary binder, as opposed to the case where a non-temporary binder is used and devolatilization is performed during the carbonization process with respect to the removal of volatile components from the non-temporary binder.
[0028] In addition to a water-soluble temporary binder, the mixture may be modified by adding a pitch product, a composition of a pitch product and a dispersant, a pitch product-water slurry, or an emulsion of a pitch product containing pitch product particles dispersed in water in the presence of an emulsifier such as a fatty acid or resin acid. The pitch product may be coal tar-based, petroleum-based, derivatives thereof, or combinations thereof. Adding a pitch product to the mixture may strengthen the aggregates.
[0029] The water-soluble temporary binder can be used in an amount of 0 to 50% by weight of water and the water-soluble temporary binder mixture, preferably 0 to 30% by weight, and more preferably 0 to 15% by weight.
[0030] The mixture of water and water-soluble temporary binder may be used in an amount of 0 to 50% by weight, preferably 0 to 45% by weight, and more preferably 0 to 30% by weight, of the total mixture of primary particles, water, and water-soluble temporary binder.
[0031] After the coagulation step, the mixture is at least partially dried. In a preferred embodiment, the dried mixture contains less than 2% by weight, preferably less than 1% by weight, of water.
[0032] In one embodiment, after the drying step of the mixture and before carbonization, the dried mixture may contain 0 to 10% by weight, or 0 to 8% by weight, or 1 to 4% by weight of a water-soluble temporary binder in the aggregate.
[0033] In one embodiment of the process of the present invention, the mixing and coagulation of coke particles with water and a water-soluble primary binder is carried out at a temperature below 70°C, more preferably below 50°C, and most preferably at room temperature. The advantages of the method according to the present invention are that it is carried out at a low processing temperature, preferably even at room temperature, thereby eliminating the need for high-temperature reactors, and furthermore, the occupational health and safety risks when using this method are significantly lower.
[0034] The mixing and agglomeration steps can be carried out in any type of mixing apparatus capable of mixing and agglomerating at room temperature, preferably a high-shear mixer, high-strength mixer, or pelletizing mixer. Disc pelletizers, pin mixers, or pin agglomers can also be used.
[0035] Instead of conventional high-temperature bonding with coal tar or petroleum pitch-based precursors, using a combination of a water-soluble transient binder and the volatile substances of coke particles as a binder can reduce the amount of volatile substances in the aggregates before carbonization, potentially resulting in a higher density, lower BET specific surface area (BET SSA) structure, and reduced porosity. Furthermore, the flocculation process can be carried out at room temperature, thus avoiding the complexity of operating conventional high-temperature flocculation processes using potentially harmful pitch binder materials.
[0036] To generate an aggregated structure, a water-soluble temporary binder is used for the initial (mechanical) aggregation of primary particles (e.g., finely ground green coke of different origins, such as petroleum coke or pitch coke, mixed with other types of particles such as silicon dioxide, graphite, or metal particles), the particles having a particle size of less than 50 microns, the coke particles having a volatile matter (VM) content of less than 5% by weight, preferably an ash content of less than 5000 ppm and a sulfur content of less than 2%.
[0037] In the subsequent carbonization process, the transient binder is largely, or preferably substantially completely, decomposed into gaseous products, i.e., at least partially, or preferably substantially completely volatilized, and the intrinsic VM in the coke particles, particularly uncalcined coke particles, undergoes devolatilization and coking, i.e., the VM is activated and then carbonized to form an in-situ binder that binds the primary particles ((uncalcined) coke particles, or possibly mixtures of coke particles and other types of particles) together, forming high-density aggregates with a size of less than 2000 microns, or less than 1000 microns, or less than 500 microns, preferably less than 100 microns, having a low porosity and low BET specific surface area. For a sufficient binding effect, the VM content of the coke particles used must be more than 5% by weight. The volatile components form a tar-like binder-active component during the initial stages of carbonization, which acts like an adhesive that binds the primary particles together. Without being bound by any theory, when working with an aqueous system of water-soluble temporary binder material dissolved in water, the water component assists in particle aggregation, and the water-soluble temporary binder material then stabilizes the green aggregates after the drying process. However, in the subsequent carbonization process, the temporary binder, which is usually used at low concentrations, is largely decomposed. The VM of the coke particles acts as the actual binding material for the aggregates. Since the resulting carbon has excellent graphitizing ability, a higher degree of graphitization can be obtained in the subsequent graphitization of the carbonized particles.
[0038] Depending on the target size of the carbonaceous precursor aggregates, the particle size of the aggregates may be further adjusted for use by light mechanical grinding, sieving, and / or classification.
[0039] The carbonaceous precursor aggregates produced by the process of the present invention may be very suitable as precursors for isotropic graphite. In further embodiments of the present invention, the process may include further coating and binding, further impregnation and graphitization of the generated isotropic carbonaceous precursor aggregates, thereby achieving isotropic graphite electrode materials for battery electrodes, particularly lithium-ion batteries and EV batteries.
[0040] The isotropic carbonaceous precursor aggregates produced by the process of the present invention are 0.5 to 4 m 2 It may have a BET SSA in the range of / g.
[0041] Furthermore, the final agglomeration products may have an agglomeration size distribution of d50: 1 to 50 microns, and / or d90: 15 to 75 microns, and / or d100: less than 100 microns.
[0042] Furthermore, the sized aggregates may have a tap density in the range of 0.7 to 1.4 g / cm³, preferably 0.9 to 1.4 g / cm³.
[0043] The sized isotropic carbonaceous precursor aggregates produced by the process of the present invention, exhibiting a low BET specific surface area and high tap bulk density, may be advantageous precursors for producing premium isotropic graphite in subsequent graphitization processes in the manufacture of lithium-ion battery anode applications.
[0044] The graphite electrodes produced from the isotropic carbonaceous precursor aggregates generated by the process of the present invention may have the following characteristics: -d50: Graphite aggregate size distribution of 3-30 microns and / or d90: 20-80 microns, - Crystallinity: d002 and / or Lc of 0.3354~0.3370 microns and / or a20~500 nm -1~4m 2 BET SSA in the range of / g -0.8~1.4 g / cm³ 3 Tap density within the range -2.22~2.67 g / cm³ 3 Effective density within the range Reversible capacity in the range of -320~370mAh / g
[0045] In addition to using the aggregates produced as carbonaceous precursor products for battery electrodes, these aggregates can be used in fluidized bed technology, for example, as carbon or graphite pellets in the purification process.
[0046] Examples of the process according to the present invention: Isotropic carbon precursor 1 was produced using green petroleum coke (GPC) with a VM content of 11.7%. The material was milled to a particle size d50 of 7 μm. The milled GPC was then agglomerated in a high-intensity mixer using an aqueous binder system (lignosulfonate) until micropellets were formed. These were collected from the mixer and then dried. The resulting micropellets were then carbonized at a temperature of 1100°C under a nitrogen stream. The material was further gently milled to the desired particle size as shown below.
[0047] Isotropic carbon precursor 2 was produced from green coke with a d50 particle size of 6.2 μm and a VM content of 10.8%. The milled material was then agglomerated in a high-strength mixer using an aqueous binder system and subsequently dried. The resulting micropellets were carbonized to a temperature of 1050°C under a nitrogen flow and then gently milled to the desired particle size (shown below).
[0048] Calcined petroleum coke 1-3 are examples of raw crushed and sized calcined petroleum coke that have not undergone any kind of pelletizing process. Those skilled in the art will understand that the isotropic carbon precursors produced according to the present invention exhibit a higher tap density than raw crushed and sized calcined petroleum coke with a relatively low surface area. JPEG2026519629000001.jpg48159
[0049] The following is a list of analytical procedures for the product parameters used in this document. - Particle size distribution (μm): Laser diffraction, Malvern3000 (dry dispersion) -VM(%):ASTM D7582 - Actual density (g / cm³) 3 ):ASTM D2638 -Sulfur (%): ASTM D6376 -BET surface area (m 2 / g):ISO9277 - Tap bulk density (g / cm³) 3 ): Internal method according to DIN51916
Claims
1. A process for generating isotropic carbonaceous precursor aggregates, i. A step of providing coke particles having an average particle size of less than 50 μm, wherein the particles have a volatile substance (VM) content of 4% to 20%, and ii. A step of mixing the coke particles with water and a water-soluble temporary binder, thereby causing the coke particles to aggregate in the mixture, iii. A step of drying the mixture at least partially, iv. The process comprising the step of carbonizing the mixture.
2. The process according to claim 1, wherein the coke particles have an average particle size of 1 to 20 μm.
3. The process according to claim 1, wherein the coke particles have an ash content of less than 5,000 ppm.
4. The process according to claim 1, wherein the coke particles comprise at least 40% by weight of uncalcined coke particles.
5. The process according to claim 1, wherein the coke particles are needle coke and / or other forms of green petroleum coke or pitch coke.
6. The process according to claim 4 or 5, wherein natural or synthetic graphite, calcined petroleum coke powder, carbonaceous additives, carbonaceous waste materials, nano- and micron-sized metallic silicon, silicon oxide, tin or aluminum metal particles, recycled materials, or combinations thereof are added to the mixture.
7. The process according to claim 6, wherein the recycled material includes recycled graphite.
8. The process according to claim 1, wherein the mixing and agglomeration are carried out by a high-shear mixer, a high-strength mixer, or a pelletizing mixer.
9. The process according to claim 1, wherein the mixing and aggregation are carried out at a temperature of less than 70°C.
10. The process according to claim 1, wherein the water-soluble temporary binder is CMC obtained by reacting starch, sugar, lignosulfonate, PVA, CMC, citric acid, humic acid, methylcellulose or hemicellulose, or a derivative thereof.
11. The process according to claim 1, wherein, in addition to the water-soluble temporary binder, a composition comprising a pitch product and a dispersant, or a pitch product-water slurry, or a pitch product emulsion is added to the mixture.
12. A process for producing an isotropic graphite electrode material for battery electrodes, particularly for lithium-ion batteries, the process comprising a process for producing an isotropic carbonaceous precursor aggregate according to any of the above claims, and further a process for graphitizing the aggregate to make it an electrode material.