Method for Manufacturing High-Safety Carbon Materials
Coating carbon materials with chitosan or sulfonated chitosan forms a stable A-SEI film, addressing thermal runaway risks in lithium-ion batteries by reducing heat generation and improving safety and performance.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- CPC CORPORATION
- Filing Date
- 2025-02-17
- Publication Date
- 2026-07-08
Smart Images
Figure 2026114878000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a method for manufacturing a carbon material with high safety.
Background Art
[0002] In recent years, carbon materials such as soft carbon and artificial graphite have attracted attention as negative electrode materials used in battery materials, particularly lithium-ion batteries, because they have characteristics such as high capacitance and long life.
[0003] Next, in the first charge-discharge process of a lithium-ion battery, when the electrode material and the electrolyte react at the solid-liquid interface, a passivation layer having the characteristics of a solid electrolyte, generally called a solid electrolyte interface (SEI) film (abbreviated as SEI film), may be formed, which greatly helps to improve the cycle life of the battery.
Summary of the Invention
Problems to be Solved by the Invention
[0004] On the other hand, in the process of developing a high-energy or high-capacity lithium-ion battery, the safety of battery use is an issue that cannot be ignored. The phenomenon of a battery catching fire or exploding is theoretically known as thermal runaway, which has a significant impact on the safety of battery use.
[0005] Generally, thermal runaway means that a battery generates abnormal heat during the charging and discharging processes due to a short circuit or electrical imbalance (such as too low capacity or too high internal resistance). When the battery exceeds the limit temperature of the thermal runaway reaction (usually about 150 °C), a heat generation reaction of thermal decomposition is gradually caused in the materials inside the battery. In particular, when thermal decomposition occurs in the SEI film, the SEI film is decomposed and a large amount of heat is generated, which in turn causes the entire thermal runaway mechanism.
[0006] Therefore, there is still room for improvement in how to reduce the large amount of heat released when the SEI film decomposes, prevent the heat resulting from thermal decomposition from causing the SEI film to undergo a thermal runaway mechanism, and ultimately improve the safety of using the negative electrode material in batteries. [Means for solving the problem]
[0007] Furthermore, the inventors have discovered that by adding chitosan or sulfonated chitosan as a polymer coating material, it is possible to coat the surface of a carbon material with a commercially viable artificial solid electrolyte interface (A-SEI) film (abbreviated as A-SEI film), and that a highly safe carbon material can be obtained. This highly safe carbon material is useful in improving the rapid charging capability and cycle life (capacity retention rate) of lithium-ion batteries during rapid charging. Moreover, it reduces the large amount of heat released when the SEI film decomposes, preventing the heat generated by the decomposition of the SEI film from causing an overall thermal runaway mechanism, and thus improving the safety of use of the negative electrode material of the battery, leading to the present invention.
[0008] Specifically, in order to solve the above problems, one aspect of the present invention is a method for producing a high-safety carbon material, comprising the steps of: (A) mixing a carbon material which is soft carbon and / or artificial graphite, a coating material which is chitosan and / or sulfated chitosan, glutaraldehyde, and a solution in a weight ratio of 100:2~6:0.2~0.6:100~300 to form a mixed slurry; (B) uniformly stirring the mixed slurry and heating it at 70°C to 90°C to form a steam-dried slurry; and (C) heating the steam-dried slurry at 70°C to 90°C for 24 hours or more, and then cooling it to room temperature to form a high-safety carbon material.
[0009] In one embodiment, the process is further followed by a step (D) in which the high-safety carbon material is sieved using a sieve with a mesh size of 38 microns or less to obtain the sieved material.
[0010] In one embodiment, the high-safety carbon material improves the capacity retention rate after 120 charge-discharge cycles at 5C by at least 40% compared to the carbon material.
[0011] In one embodiment, the high-safety carbon material exhibits a heat generation of less than 7.5 J / g at the SEI exothermic peak after 120 charge-discharge cycles at 5C.
[0012] In one embodiment, the highly safe carbon material obtained by using the sulfated chitosan as a coating material in step (A) exhibits a heat generation of less than 5.5 J / g at the SEI exothermic peak after 120 charge-discharge cycles at 5C.
[0013] In one embodiment, the high-safety carbon material improves the fast charging capability under 2C fast charging conditions by at least 3% and the fast charging capability under 5C fast charging conditions by at least 3% compared to the carbon material.
[0014] In one embodiment, the high-safety carbon material exhibits an Accumulated Irreversible Efficiency (AIE) of less than 88.5% after 200 charge-discharge cycles at 0.3C.
[0015] In one embodiment, the high-safety carbon material improves the capacity retention rate after 100 charge-discharge cycles at 0.3C by at least 2% compared to the carbon material.
[0016] In one embodiment, when testing according to the SAE J2464 standard under conditions of a puncture needle diameter of 3 mm, a puncture speed of 8 cm / min, and a minimum puncture depth of puncturing a battery cell, LiNi is used for the positive electrode. 0.8 Mn 0.1 Co 0.1 A soft-pack battery with a capacity of 1Ah, using O2 and employing the aforementioned high-safety carbon material for the negative electrode, passes the puncture test.
[0017] In one embodiment, in the step (A), the solution is water or water containing 2% by volume of acetic acid.
Advantages of the Invention
[0018] The present invention has been made in view of the above-described conventional problems, and an object thereof is to provide a method for producing a highly safe carbon material that can improve the use safety of a negative electrode material of a battery. Specifically, by adding chitosan or sulfated chitosan as a polymer coating material, an A-SEI film can be coated on the surface of the carbon material, reducing a large amount of heat released when the SEI film is decomposed, and preventing the heat caused by the decomposition of the SEI film from triggering the overall thermal runaway mechanism, and further improving the use safety of the negative electrode material of the battery.
Brief Description of the Drawings
[0019] [Figure 1] It is a flowchart showing a method for producing a highly safe carbon material according to the present invention. [Figure 2] It is a photograph showing the state 10 seconds after the puncture test in Comparative Example 1. [Figure 3] It is a photograph showing the state 18 seconds after the puncture test in Test Example 1.
Embodiments for Carrying Out the Invention
[0020] The following describes the implementation manner of the present invention through specific examples, and those skilled in the art can understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through different examples, and the details of this specification can be variously modified and changed based on different viewpoints and applications without departing from the gist of the present invention.
[0021] Unless otherwise specified in this document, the term "A to B" used in the specification and claims includes the meaning of "A or more and B or less". For example, the term "10 to 40% by weight" includes the meaning of "10% by weight or more and 40% by weight or less".
[0022] First, please refer to FIG. 1. FIG. 1 is a flowchart showing a method for producing a high-safety carbon material according to the present invention. As shown in FIG. 1, the method for producing a high-safety carbon material according to the present invention includes steps (A) to (C). Further, in one embodiment, if necessary, after step (C), step (D) is further included. The following is a detailed description of each step.
[0023] [Step (A)] Step (A) is a step for forming a mixed slurry by mixing a carbon material, a coating material, glutaraldehyde, and a solution at a weight ratio of 100:2 to 6:0.2 to 0.6:100 to 300. Here, the carbon material may be granular soft carbon and / or artificial graphite, and the coating material may be chitosan and / or sulfated chitosan. Chitosan and / or sulfated chitosan are polymers with excellent thermal stability, and the sulfonic acid groups generated after sulfonation are useful for the movement of lithium ions. By using glutaraldehyde (Glutaraldehyde, GA) as a cross-linking agent and blending, chitosan or sulfated chitosan and glutaraldehyde can be cross-linked to form a stable polymer artificial solid electrolyte interface (Artificial Solid Electrolyte Interface, A-SEI) film covering the carbon material.
[0024] In one specific example, the weight ratio of carbon material:chitosan:glutaraldehyde:solution may be 100:2:0.2:100, 100:4:0.4:100, or 100:6:0.6:100. On the other hand, in another specific example, the weight ratio of carbon material:sulfated chitosan:glutaraldehyde:solution may be 100:2:0.2:300, or 100:4:0.4:300. Furthermore, from the viewpoint of facilitating uniform mixing, the weight ratio of carbon material to solution (carbon material:solution) is preferably 1:1 to 1:3.
[0025] Furthermore, the solution may be water or water containing 2% by volume of acetic acid. Also, the carbon material, chitosan, sulfated chitosan, glutaraldehyde, and solution can all be commercially available products, such as soft carbon from CPC Corporation of Taiwan or artificial graphite (trade name: MGP) purchased from CHINA STEEL CHEMICAL Corporation, and are not particularly limited. Step (A) allows for the uniform dispersion of the carbon material in the solution, and subsequent steps allow for the crosslinking of chitosan or sulfated chitosan with glutaraldehyde to form an A-SEI film coated with the carbon material.
[0026] [Process (B)] Step (B) is a step for uniformly stirring the mixed slurry obtained in step (A) and heating it at 70°C to 90°C to form a steam-dried slurry. Specifically, step (B) may be a step for forming a steam-dried slurry by placing the mixed slurry obtained in step (A) in a round-bottom flask, placing it on a heating plate, uniformly stirring it at a rotation speed of 300 rpm, and heating it at 80°C until the slurry is completely evaporated (the solution is removed). Step (B) allows the carbon material to be coated with chitosan or sulfated chitosan.
[0027] [Process (C)] Step (C) is a process for forming a highly safe carbon material by heating the steam-dried slurry obtained in step (B) at 70°C to 90°C for 24 hours or more, and then cooling it to room temperature. Specifically, step (C) may be a process for further obtaining a highly safe carbon material by removing the carbon material (evaporated slurry) coated with chitosan or sulfated chitosan from a round-bottom flask, drying it in a vacuum oven at 80°C for 24 hours (or treating it in a horizontal furnace tube filled with nitrogen, raising the temperature to 80°C at a rate of 10°C / min for 24 hours), and then cooling it to room temperature (which may be natural cooling or cooling by lowering the temperature), thereby forming an A-SEI film coated on the carbon material. By step (C), it is possible to crosslink chitosan or sulfated chitosan with glutaraldehyde and form a highly safe carbon material having a stable A-SEI film on the carbon material.
[0028] [Process (D)] Step (D) is an optional step for selecting high-safety carbon material with an appropriate particle size to facilitate its subsequent use as a negative electrode material. Specifically, step (D) may be a step for sieving the high-safety carbon material with a sieve with a mesh size of 38 microns (400 meshes) or less to obtain the sieved material. [Examples]
[0029] The present invention will be further described below through examples and comparative examples, but the present invention is not limited to these examples and comparative examples.
[0030] <Manufacturing of high-safety carbon materials> <Production Example 1> High-safety carbon material 1 of manufacturing example 1 was obtained according to steps (A) to (C) described above. Here, in step (A), the weight ratio of soft carbon:chitosan:glutaraldehyde:solution is 100:2:0.2:100. The soft carbon used is PPSC series soft carbon purchased from CPC Corporation of Taiwan, the chitosan used is product number 419419 purchased from SIGMA-ALDRICH, the glutaraldehyde used is product number 49629 purchased from SIGMA-ALDRICH, and the solution is water containing 2% by volume of acetic acid.
[0031] <Production Examples 2-3> High-safety carbon materials 2 and 3 were obtained in the same manner as in Fabrication Example 1, except that the weight ratios of soft carbon, chitosan, glutaraldehyde, and solution were changed to 100:4:0.4:100 and 100:6:0.6:100, respectively.
[0032] <Production Example 4> High-safety carbon material 4 of production example 4 was obtained according to steps (A) to (C) described above. Here, in step (A), the weight ratio of soft carbon:sulfated chitosan:glutaraldehyde:solution is 100:2:0.2:300. Furthermore, the soft carbon used was PPSC series soft carbon purchased from CPC Taiwan Ltd., the sulfated chitosan used was chitosan (product number 419419) purchased from SIGMA-ALDRICH Corporation which was modified by the user, the glutaraldehyde used was product number 49629 purchased from SIGMA-ALDRICH Corporation, and water was used as the solution.
[0033] <Production Example 5> A highly safe carbon material 5 was obtained in the same manner as in Fabrication Example 4, except that the weight ratio of soft carbon, sulfated chitosan, glutaraldehyde, and solution was changed to 100:4:0.4:300.
[0034] <Reference example 1> Soft carbon is used as carbon material A in Reference Example 1.
[0035] <Example 1> Using the high-safety carbon material 1 from Example 1, the negative electrode material 1 from Example 1 was fabricated through the above process (D).
[0036] Specifically, in the preparation of negative electrode material 1, 950g of high-safety carbon material 1, 30g of sodium alginate (purchased from ACROS, product number: 177772500), and 20g of conductive additive (conductive carbon black, purchased from Timcal, product name: Super P) were uniformly mixed to form the negative electrode material. Subsequently, the negative electrode material was mixed with 1233g to 1438g of N-methylpyrrolidone (NMP) to obtain a mixture. This mixture was then applied to a copper foil with a thickness of 14μm and dried at 85°C for 0.5 hours to remove moisture and NMP, thereby obtaining the negative electrode for the entire battery. Here, the negative electrode has a copper foil and a conductive layer formed on the copper foil with a thickness of 100μm to 110μm. Next, using artificial laminate, the negative electrode, positive electrode, electrolyte, and separator membrane (brand: Celgard, material: PP, thickness: 20 μm) were assembled to create a complete battery (length x width x height: 4 cm x 2 cm x 0.2 cm, battery core capacity: 0.15 Ah to 0.2 Ah).
[0037] On the other hand, the positive electrode of the battery comprises an aluminum foil as a conductive carrier and a conductive film formed on the surface of the aluminum foil. The conductive film of the positive electrode of the battery comprises 92.5% by weight of lithium nickel cobalt manganese oxide (LNMC, capacity ≥ 150 mAh / g), 2.5% by weight of PVDF, and 5% by weight of conductive carbon black (purchased from Timcal, product name: Super P). The electrolyte comprises 97% by weight of a 1.2 M LiPF6 solution, 1% by weight of vinylene carbonate (VC), and 2% by weight of 1,3-propanesultone (PS). The LiPF6 solution comprises LiPF6, EC, EMC, and dimethyl carbonate (DMC), and the volume ratio of EC:EMC:DMC is 1:3:2. Next, using a charger / discharger (manufacturer: Maccor, model number: Series 4000), the capacity retention rate and rapid charging capability (rapid charging conditions: charge / discharge: constant current, charge / discharge rate (C-rate): constant current / 0.1C (constant current + constant voltage)) were measured for charge / discharge cycles at 2C and 5C, respectively, and the measurement results are summarized in Tables 1 and 2 below.
[0038] <Examples 2-5> Aside from using the high-safety carbon materials 2-5 from Examples 2-5, all batteries for Examples 2-5 were obtained in the same manner as in Example 1. Next, the capacity retention rate and rapid charging capability were measured for Examples 2-5, and the measurement results are summarized in Tables 1 and 2 below.
[0039] <Comparative Example 1> A complete battery for Comparative Example 1 was obtained in the same manner as in Example 1, except that carbon material A from Reference Example 1 was used. Next, the capacity retention rate and rapid charging capability were measured for Comparative Example 1, and the measurement results are summarized in Tables 1 and 2 below.
[0040] [Table 1]
[0041] [Table 2]
[0042] As can be seen from Table 1 above, compared to the carbon material A of Comparative Example 1, which has a rapid charging capacity of 56% (capable of charging 56% of the battery capacity) under rapid charging conditions at 2C, the high-safety carbon materials 1 to 3 of Examples 1 to 3 have a rapid charging capacity of 60% or more under rapid charging conditions at 2C. In other words, the high-safety carbon materials 1 to 3 of Examples 1 to 3, which are carbon materials coated with chitosan, show an improvement of at least 3% in rapid charging capacity under rapid charging conditions at 2C, and even an improvement of approximately 7%. Furthermore, compared to the carbon material A of Comparative Example 1, which has a rapid charging capacity of 38% under rapid charging conditions at 5C, the high-safety carbon materials 1 to 3 of Examples 1 to 3 show a rapid charging capacity of 40% or more under rapid charging conditions at 5C, and can even reach 50%. In other words, as can be seen from Table 1 above, compared to Comparative Example 1 which used carbon material A, the high-safety carbon materials 1 to 3 of Examples 1 to 3, in which the carbon material was coated with chitosan, showed an improvement of at least 3% and even approximately 12% in rapid charging capacity under 5C rapid charging conditions.
[0043] Furthermore, as can be seen from Table 2 above, after 120 charge-discharge cycles at 5C, the capacity retention rate of carbon material A in Comparative Example 1 is 25%, while the high-safety carbon materials 2, 4, and 5 in Examples 2, 4, and 5 have a capacity retention rate of 40% or more after 120 charge-discharge cycles at 5C. In Examples 4 and 5, which use sulfated chitosan, the capacity retention rate can reach 70% or more. Therefore, it can be seen that using sulfated chitosan is more effective than using chitosan.
[0044] Furthermore, as can be seen from Table 2 above, compared to Comparative Example 1 using carbon material A, the high-safety carbon materials 4 and 5 of Examples 4 and 5, in which the carbon material was coated with sulfated chitosan, showed an improvement of at least 40% and even approximately 50% in capacity retention after 120 charge-discharge cycles at 5C.
[0045] [Measurement of heat output at the SEI fever peak] For all batteries in Comparative Example 1 and Examples 2, 4, and 5, the amount of heat generated at the SEI heat peak after 120 charge-discharge cycles at 5C (fully charged) at a heating rate of 5°C / min was calculated, and the results are summarized in Table 3 below. Here, the amount of heat generated is the heat output per unit mass, which is the integral over time. For example, when measuring heat generation with a DSC, the heat output (flow rate) Cp differs at temperatures T1 and T2, so the unit of heat output (flow rate) Cp is J / min × g. If the heating rate is 5°C / min, T1 corresponds to time t1, T2 corresponds to time t2, and the heat generation ΔH =
number
[0046] [Table 3]
[0047] As can be seen from Table 3 above, compared to the carbon material A of Comparative Example 1, which has a heat generation of 46.9 J / g, the high-safety carbon materials 2, 4-5 of Examples 2, 4-5 have a heat generation of less than 7.5 J / g at the SEI heat generation peak after 120 charge-discharge cycles at 5C, and furthermore, Examples 4-5, which use sulfated chitosan, exhibit excellent effects with a heat generation of less than 5.5 J / g. Therefore, it can be seen that the present invention can significantly reduce the large amount of heat released when the SEI film decomposes.
[0048] [Accumulative irreversible capacity (AIE) measurement] For all batteries in Comparative Example 1 and Examples 4-5, the AIE was measured after 200 charge-discharge cycles at 0.3C with a heating rate of 5°C / min. That is, the Coulomb efficiency for each cycle was accumulated, and then the lost Coulomb efficiency was added to determine the total. The results are summarized in Table 4 below.
[0049] [Table 4]
[0050] As can be seen from Table 4 above, compared to the AIE of carbon material A in Comparative Example 1, which is 88.8%, the high-safety carbon materials 4 and 5 in Examples 4 and 5 achieve an AIE of less than 88.5% after 200 charge-discharge cycles at 0.3C, and can even reach an excellent result of approximately 77.7%.
[0051] <Production Example 6> First, following steps (A) to (C) above, the high-safety carbon material 6 of production example 6 was obtained. Here, in step (A), the weight ratio of artificial graphite:sulfated chitosan:glutaraldehyde:solution is 100:2:0.2:300. Furthermore, the artificial graphite used was YPG01 graphite or CY92S graphite purchased from CPC Taiwan Ltd., the sulfated chitosan used was chitosan (product number 419419) purchased from SIGMA-ALDRICH Company, which had been further modified, the glutaraldehyde used was product number 49629 purchased from SIGMA-ALDRICH Company, and the solution used was water.
[0052] <Production Example 7> A highly safe carbon material 7 was obtained in the same manner as in example 6, except that the weight ratio of artificial graphite, sulfated chitosan, glutaraldehyde, and solution was changed to 100:4:0.4:300.
[0053] <Reference example 2> Artificial graphite is used as carbon material B in Reference Example 2.
[0054] <Examples 6-7> Except for using the high-safety carbon materials 6-7 from Fabrication Examples 6-7, all batteries for Examples 6-7 were obtained in the same manner as in Example 1. Next, the capacity retention rate of the charge-discharge cycle at 0.3C was measured using a charge / discharge machine (manufacturer: Maccor, model: Series 4000), and the measurement results are summarized in Table 5 below.
[0055] <Comparative Example 2> A complete battery for Comparative Example 2 was obtained in the same manner as in Example 1, except that carbon material B from Reference Example 2 was used. Next, as described above, the capacity retention rate was measured for Comparative Example 2, and the measurement results are summarized in Table 5 below.
[0056] [Table 5]
[0057] As can be seen from Table 5 above, compared to the carbon material B of Comparative Example 2, which has a capacitance retention rate of 89.6%, the high-safety carbon materials 6 and 7 of Examples 6 and 7 can achieve a capacitance retention rate of 91% or more after 100 charge-discharge cycles at 0.3C. From this, it can be seen that applying sulfated chitosan (or chitosan) not only to soft carbon but also to artificial graphite has the effect of improving capacitance retention and significantly reducing the large amount of heat released when the SEI film decomposes. Furthermore, as can be seen from Table 5 above, compared to Comparative Example 2 using carbon material B, the high-safety carbon materials 6 and 7 of Examples 6 and 7, which are coated with sulfated chitosan, show an improvement of at least 2% in capacitance retention after 100 charge-discharge cycles at 0.3C, and even an improvement of approximately 3%.
[0058] [Puncture test] <Example 1> The test will be conducted according to the SAE J2464 standard, under the conditions of a puncture needle diameter of 3 mm, a puncture speed of 8 cm / min, and a minimum puncture depth of puncturing the battery cell. Here, in a 1 Ah soft pack battery, the positive electrode is LiNi 0.8 Mn 0.1 Co 0.1O2 (theoretical capacitance of 200 mAh / g) was used, 90% by weight artificial graphite + 10% by weight soft carbon was used for the negative electrode, PE was used for the separator membrane, and the electrolyte was the same as the electrolyte used in Example 1 above. As a result of the puncture test, as shown in Figure 2, the negative electrode of Control Example 1 showed ignition, explosion and combustion after 10 seconds, which means that it failed the puncture test. Here, Figure 2 is a photograph showing the state of Control Example 1 10 seconds after the puncture test. <Test Example 1> Except for using 90% by weight of high-safety carbon material 6 from Fabrication Example 6 and 10% by weight of high-safety carbon material 4 from Fabrication Example 4 for the negative electrode, the test was conducted according to the SAE J2464 standard, just like in Control Example 1. As a result of the puncture test, as shown in Figure 3, the negative electrode of Test Example 1 still did not ignite after 18 seconds, which means that the puncture test was passed. Here, Figure 3 is a photograph showing the state of Test Example 1 18 seconds after the puncture test.
[0059] From this, it can be seen that whether the substrate is artificial graphite or soft carbon, a stable A-SEI film can be formed by crosslinking chitosan or sulfated chitosan with glutaraldehyde, thereby coating carbon materials such as artificial graphite or soft carbon. Therefore, the highly safe carbon material produced by the present invention will pass the puncture test.
[0060] Therefore, according to the method of the present invention, a highly safe carbon material can be obtained that significantly reduces the large amount of heat released when the SEI film decomposes, helps prevent the heat generated by the decomposition of the SEI film from causing an overall thermal runaway mechanism, and ultimately improves the safety of use of the negative electrode material of a battery.
[0061] The present invention is not limited to the embodiments described above, and various modifications can be made within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included within the technical scope of the present invention. [Explanation of Symbols]
[0062] (A)~(C) Project
Claims
1. Step (A) involves mixing a carbon material, which is soft carbon and / or artificial graphite, a coating material, which is chitosan and / or sulfated chitosan, glutaraldehyde, and a solution in a weight ratio of 100:2 to 6:0.2 to 0.6:100 to 300 to form a mixed slurry. Step (B) involves uniformly stirring the mixed slurry and heating it at 70°C to 90°C to form a steam-dried slurry. Step (C) involves heating the steam-dried slurry at 70°C to 90°C for 24 hours or more, and then cooling it to room temperature to form a highly safe carbon material. A method for producing high-safety carbon materials, including [specific material].
2. The method for producing a high-safety carbon material according to claim 1, further comprising the step (D) of sieving the high-safety carbon material with a sieve having a mesh size of 38 microns or less after the above step (C) to obtain the sieved material.
3. The method for producing a high-safety carbon material according to claim 1 or 2, wherein the high-safety carbon material improves the capacity retention rate after 120 charge-discharge cycles at 5C by at least 40% compared to the carbon material.
4. The method for producing a high-safety carbon material according to claim 1 or 2, wherein the high-safety carbon material has a heat generation amount of less than 7.5 J / g at the SEI heat generation peak after 120 charge-discharge cycles at 5C.
5. A method for producing a high-safety carbon material according to claim 1 or 2, wherein the high-safety carbon material obtained by using the sulfated chitosan as a coating material in step (A) has a heat generation amount of less than 5.5 J / g at the SEI exothermic peak after 120 charge-discharge cycles at 5C.
6. A method for producing a high-safety carbon material according to claim 1 or 2, wherein the high-safety carbon material improves the rapid charging capacity under 2C rapid charging conditions by at least 3% compared to the carbon material, and improves the rapid charging capacity under 5C rapid charging conditions by at least 3%.
7. The method for producing a high-safety carbon material according to claim 1 or 2, wherein the high-safety carbon material has an accumulated irreversible capacity (AIE) of less than 88.5% after 200 charge-discharge cycles at 0.3C.
8. The method for producing a high-safety carbon material according to claim 1 or 2, wherein the high-safety carbon material improves the capacity retention rate after 100 charge-discharge cycles at 0.3C by at least 2% compared to the carbon material.
9. When testing according to the SAE J2464 standard, under the conditions of a puncture needle diameter of 3 mm, a puncture speed of 8 cm / min, and a minimum puncture depth of puncturing a battery cell, LiNi is used for the positive electrode. ０．８ Mn ０．１ Co ０．１ O ２ A method for producing a high-safety carbon material according to claim 1 or 2, wherein a soft pack battery with a capacity of 1 Ah, using the high-safety carbon material for the negative electrode, passes a puncture test.
10. The method for producing a high-safety carbon material according to claim 1 or 2, wherein in step (A), the solution is water or water containing 2% by volume of acetic acid.