Modified oxidized chitosan bio-based phenolic resin, preparation and application thereof, negative electrode and battery

Abstract

The invention belongs to the field of graphite negative electrode materials, and particularly relates to modified oxidized chitosan bio-based phenolic resin, preparation and application of the modified oxidized chitosan bio-based phenolic resin, a negative electrode and a battery. The preparation method comprises the following steps: polymerizing aldehyde chitosan and aromatic phenol to obtain chitosan-phenolic resin; the modified oxidized chitosan bio-based phenolic resin is prepared by carrying out graft modification on chitosan-phenolic resin, a formula 1 (shown in the description) and a formula 2 (shown in the description). A brand new carbon source is prepared, the carbon source is innovatively used for coating modification of graphite, the carbonization difficulty can be synergistically reduced, carbonization can be realized at a relatively low temperature, in addition, the low-temperature conductivity, the quick charge performance and the safety of the prepared graphite material can be remarkably improved, in addition, the material can be endowed with good self-healing capability, and the carbon source has a good application prospect. And the long cycle performance can be enhanced.

Description

BACKGROUND

[0001] The present application belongs to the field of battery materials, and particularly relates to the field of modified graphite negative electrodes. TECHNICAL FIELD

[0002] Graphite has excellent electrical conductivity, but it has poor active ion intercalation capability. For this reason, the prior art often uses amorphous carbon to modify graphite by coating.

[0003] The existing graphite carbon coating process mainly includes chemical vapor deposition, sol-gel method, pyrolysis method, etc. The chemical vapor deposition method is to decompose the carbon source gas at high temperature to deposit a carbon layer on the surface of graphite. The sol-gel method is to carbonize the composite of graphite powder and carbon source precursor to obtain a carbon coating layer. The pyrolysis method is to mix graphite with carbon source, and then pyrolyze at carbonization temperature to form a carbon layer on the surface of graphite.

[0004] For the pyrolysis method, different carbon sources will affect the physicochemical structure of the carbon coating layer, and will greatly affect the performance of the modified graphite. The main carbon sources in the prior art include sugars, polymers, etc.

[0005] For example, the patent document with publication number CN119517950A discloses a preparation method of carbon-coated graphite composite material, which comprises mixing and treating an alkaline mixed solution containing graphite materials, main carbon sources for coating, collaborative carbon sources for coating, and additives to obtain a dispersion liquid; drying and carbonizing the dispersion liquid under preset conditions to form a carbon-coated graphite precursor; and carbonizing the carbon-coated graphite precursor in a protective gas environment to obtain a carbon-coated graphite composite material; the main carbon sources for coating include sugars; and the collaborative carbon sources for coating include compounds containing non-carbon heteroatoms.

[0006] For another example, the patent document with publication number CN117393737A discloses a preparation method of nitrogen-doped carbon-coated graphite negative electrode material, which comprises hydrothermal reaction and carbonization of a mixed solution containing carbon source, nitrogen source, template agent, and graphite to obtain a nitrogen-doped carbon-coated graphite negative electrode material.

[0007] For another example, the patent document with publication number CN115986091A discloses a carbon-coated graphite negative electrode material, a preparation method thereof, and a battery, which comprises the following steps: performing an oxidation polymerization reaction on a mixed solution containing artificial graphite, coating agent monomers, organic acid, and oxidizing agent to obtain a solid; and performing carbonization treatment on the solid to obtain a carbon-coated graphite negative electrode material.

[0008] In summary, the prior art has many schemes for coating graphite by carbonization of carbon sources, but the existing carbon coating function is still lacking in low-temperature performance and fast-charging performance, and the low-temperature, fast-charging, safety, and long-cycle performance still need to be further improved. SUMMARY

[0009] To address the problems existing in the prior art, the primary objective of this invention is to provide a method for preparing modified oxidized chitosan bio-based phenolic resin, which aims to prepare a graphite-modified carbon source that can effectively improve the low-temperature, fast-charging performance and safety of graphite, and has a certain self-healing ability.

[0010] The second objective of this invention is to provide a modified oxidized chitosan bio-based phenolic resin prepared by the aforementioned method and its application in graphite modification.

[0011] A third objective of this invention is to provide modified graphite prepared using the modified oxidized chitosan bio-based phenolic resin, a modification method, and the resulting battery.

[0012] A method for preparing modified oxidized chitosan bio-based phenolic resin involves oxidizing chitosan to obtain aldehyde-modified chitosan; then polymerizing the aldehyde-modified chitosan with aromatic phenols to obtain chitosan-phenolic resin.

[0013] Modified oxidized chitosan bio-based phenolic resin is prepared by grafting chitosan-phenolic resin with Formula 1 and Formula 2 (also known as modification).

[0014] Formula 1

[0015] Formula 2

[0016] In Formula 1, R1 and R2 are individually H, C1~C3 alkyl or amino groups.

[0017] This invention innovatively pre-treats chitosan with aldehyde oxidation, then uses it to polymerize with aromatic phenols to obtain chitosan-phenolic resin. Based on the surface structure characteristics of chitosan-phenolic resin and Formulas 1 and 2, graft modification is performed, thus obtaining a novel carbon source. This carbon source is innovatively used for the coating modification of graphite, which can synergistically reduce the difficulty of carbonization and achieve carbonization at a lower temperature. In addition, it can significantly improve the low-temperature conductivity, fast-charging performance, and safety of the obtained graphite material. Furthermore, it can endow the material with good self-healing ability and enhance its long-cycle performance.

[0018] In this invention, the oxidant for chitosan oxidation can be any oxidizing component capable of converting the hydroxyl groups in chitosan into aldehyde groups, such as periodate, or more specifically, sodium periodate, potassium periodate, etc.

[0019] Preferably, the weight ratio of chitosan to oxidant is 1:0.005~0.02; more preferably, it is 1:0.008~0.015; and even more preferably, it is 1:0.009~0.011. At these preferred amounts, the structure can be further optimized, which helps to further improve the fast-charging, low-temperature, and long-cycle properties of the prepared material.

[0020] Preferably, the oxidation reaction temperature is 15~35℃, and more preferably 20~30℃.

[0021] Preferably, the oxidation reaction takes 5 to 15 hours, and more preferably 8 to 12 hours.

[0022] In this invention, the aromatic phenol can be a compound having 1 to 2 phenolic hydroxyl groups on a five- or six-membered aromatic ring.

[0023] In this invention, aromatic phenols are compounds having the structure of Formula 3;

[0024] Formula 3

[0025] In Formula 3, R3 is H, a C1-C3 alkyl group, a C1-C3 alkoxy group, or a hydroxyl group.

[0026] Preferably, the mass ratio of aldehyde-modified chitosan to Formula 3 is 1:0.5~1.5; more preferably, it is 1:0.6~1.1; and even more preferably, it is 1:0.85~0.95. At these preferred amounts, the structure can be further optimized, which helps to further improve the fast-charging, low-temperature, and long-cycle properties of the prepared material.

[0027] Preferably, the polymerization reaction is carried out under acidic conditions.

[0028] Preferably, the pH of the polymerization reaction process is 4 to 7; further, it can be 4.5 to 6.5, and even more preferably 4.9 to 5.1.

[0029] Preferably, the polymerization temperature is 45~85℃, and more preferably 50~80℃. The polymerization time is 2~8 hours; more preferably 3~6 hours.

[0030] In this invention, aldehyde-modified chitosan and aromatic phenol are polymerized to obtain oxidized chitosan-phenolic resin with chitosan as the target center. Furthermore, the oxidized chitosan-phenolic resin is used as the target center and grafted onto it using Formula 1 and Formula 2. This can synergistically improve the performance of graphite modification, and improve the low-temperature conductivity, fast charging, safety and long-cycle stability of graphite.

[0031] In this invention, in Formula 1, R1 and R2 are both amino groups.

[0032] Preferably, the mass ratio of chitosan-phenolic resin, Formula 1, and Formula 2 is 1:0.1~0.45:0.1~0.65; more preferably, it can be 1:0.15~0.4:0.15~0.6; and most preferably, it is 1:0.25~0.35:0.35~0.45. At these preferred amounts, the structure can be further optimized, which helps to further improve the fast-charging, low-temperature, and long-cycle properties of the prepared material.

[0033] In this invention, the grafting modification process is carried out under Lewis acid catalysis.

[0034] Preferably, the Lewis acid includes at least one of aluminum chloride, aluminum sulfate, and zinc chloride.

[0035] Preferably, the weight ratio of chitosan-phenolic resin to Lewis acid is 1:0.005~0.015.

[0036] Preferably, the reaction temperature for graft modification is 70~140℃, more preferably 80~120℃, and the reaction time is 2~8 hours; more preferably 3~6 hours.

[0037] The present invention also provides a modified oxidized chitosan bio-based phenolic resin prepared by the preparation method described above.

[0038] In this invention, the preparation method can endow the prepared material with special physicochemical properties, and the material with these properties has unexpected advantages in graphite modification, such as improving the low-temperature conductivity, fast charging, safety and long-cycle performance of modified graphite.

[0039] The present invention also provides an application of the modified oxidized chitosan bio-based phenolic resin obtained by the preparation method described above, wherein the modified chitosan is carbonized after being compounded with graphite to obtain modified graphite.

[0040] In this invention, the weight ratio of the modified oxidized chitosan bio-based phenolic resin to graphite is 0.02~0.2:1, and can be further 0.05~0.15:1.

[0041] Preferably, the carbonization temperature is above 650°C, further preferably 700~1000°C, and even more preferably 750~850°C. In this invention, thanks to the innovative use of the modified oxidized chitosan bio-based phenolic resin, excellent graphite modification effects can be obtained at lower temperatures, resulting in excellent low-temperature conductivity, fast charging, safety, and long cycle life.

[0042] Preferably, the carbonization time is 2 to 8 hours, and more preferably 3 to 6 hours.

[0043] In this invention, modified oxidized chitosan bio-based phenolic resin and graphite can be mixed and compounded based on known methods. For example, it can be a conventional fusion coating compound with fusion parameters of 400-800 rpm and 4-6 min.

[0044] The present invention also provides a negative electrode comprising the modified graphite described herein.

[0045] The negative electrode of this invention, apart from containing the modified graphite described herein, may have other known components and structures. For example, it may contain a current collector and a negative electrode material composited on the current collector. The negative electrode material may include a negative electrode active material, a conductive agent, and a binder, wherein the negative electrode active material contains the modified graphite described herein. In this invention, the weight ratio of the negative electrode active material, the conductive agent, and the binder may be 65~95:1~15:1~15.

[0046] The present invention also provides a battery comprising the negative electrode of the present invention comprising the modified graphite.

[0047] The battery described in this method, except for the negative electrode as described in this invention, may have other known components and structural relationships. For example, it may include a battery cell comprising a positive electrode, a barrier layer, and a negative electrode sequentially laminated together. The barrier layer may be a solid electrolyte and / or a separator. When a separator is included, an electrolyte solution for soaking the battery cell may also be added to the battery.

[0048] Beneficial effects

[0049] This invention polymerizes oxidized chitosan and aromatic phenols, and then modifies them in combination with Formula 1 and Formula 2 to obtain a novel modified oxidized chitosan bio-based phenolic resin. This resin is innovatively used to modify graphite, enabling beneficial carbonization at lower temperatures, thereby improving the low-temperature conductivity, fast charging, safety, and long-cycle properties of the modified graphite.

[0050] For example, the modified oxidized chitosan bio-based phenolic resin of this invention uses chitosan polysaccharide as a framework, enabling the coating layer to retain elasticity at low temperatures and buffering the volume expansion / contraction of the electrode material. Furthermore, the combined modification using formulas 1 and 2 of this invention exhibits electron-rich properties, promoting the transition of electrons from the electrode active material to the current collector; it also weakens the binding energy between active ions such as lithium ions and solvent molecules, accelerating the transport of active ions at the electrode / electrolyte interface. In addition, the modified oxidized chitosan bio-based phenolic resin and the low-temperature modified carbon layer of this invention exhibit dynamic -C=N- on their surface. During low-temperature charge and discharge, the reversible breakage and recombination of bonds can release local stress, repair microcracks caused by lithium dendrites or volume changes, and maintain the continuity of the conductive network and ion channels.

[0051] Low temperature performance: Electrical conductivity increased by 110% at -20℃ (compared to traditional asphalt coating materials).

[0052] Cycle life: The fast charging cycle retention rate can reach 85% after 800 cycles at low temperature 3C, and 95% after 800 cycles at room temperature 3C.

[0053] Safety: The resin has an LOI ≥ 32%, exhibiting excellent safety.

[0054] Environmental friendliness: Bio-based content ≥40%, no formaldehyde release during production process. Attached Figure Description

[0055] Figure 1 This is a SEM image of Example 3;

[0056] Figure 2 To compare with the SEM image of Case 6. Detailed Implementation

[0057] This invention provides an optional method for preparing a modified oxidized chitosan bio-based phenolic resin (also simply referred to as resin), the steps of which are as follows:

[0058] (1) Preparation of oxidized chitosan:

[0059] Chitosan is dissolved in an acidic solution (e.g., a 0.5-5% acetic acid solution), an oxidizing agent (such as periodate) is added, and the mixture is purified after reacting in the dark to obtain aldehyde-containing oxidized chitosan, denoted as OCS.

[0060] (2) Preparation of oxidized chitosan phenolic resin:

[0061] The OCS obtained in step (1) is mixed with aromatic phenol (such as phenol) at a mass ratio of 1:0.5~1.5, and heated and stirred under acidic conditions to obtain oxidized chitosan phenolic resin, denoted as OCSPF;

[0062] (3) Grafting modification:

[0063] The OCSPF obtained in step (2) is mixed with Formula 1 and Formula 2 at a mass ratio of 1:0.1~0.45:0.1~0.65, and polycondensation is carried out under the catalysis of Lewis acid (e.g., aluminum salt) to obtain grafted modified OCSPF.

[0064] The periodate mentioned in step (1) is at least one of sodium periodate or potassium periodate, the weight ratio of chitosan to periodate is 1:0.005~0.02, the oxidation reaction temperature is 15~35℃, and the reaction time is 8~12 hours.

[0065] The pH value of the reaction system in step (2) is 4.5~6.5, the reaction temperature is 45~85℃, the reaction time is 3~6 hours, and the resin is diluted with ethanol to control the resin solid content at 45%.

[0066] The reaction temperature in step (3) is 70~140℃ and the reaction time is 3~6 hours.

[0067] This invention provides an optional method for preparing modified graphite using the modified chitosan bio-based phenolic resin.

[0068] The grafted modified OCSPF (carbon source) obtained in step (3) is mixed with artificial graphite, and the resin is uniformly coated on the graphite surface by fusion. Then, a carbon layer is formed by low-temperature carbonization. After depolymerization, demagnetization, and sieving, the finished product is obtained, denoted as CP. The fusion method can be a conventional thermal fusion method, for example, the temperature of thermal fusion can be 200~400℃.

[0069] The weight ratio of artificial graphite to resin is 1:0.02~0.2; the fusion coating parameters are: rotation speed 400~800 rpm, time 4~6 min; the maximum low-temperature carbonization temperature is 700~1000℃, and the holding time is 3~6 h.

[0070] Example 1

[0071] (1) Preparation of oxidized chitosan:

[0072] Chitosan was dissolved in 1% acetic acid solution, and an oxidant (sodium periodate) was added. The weight ratio of chitosan to oxidant was 1:0.008. The oxidation reaction temperature was 30℃ and the reaction time was 12h. After the reaction was carried out in the dark, impurities were removed to obtain aldehyde-containing oxidized chitosan, which was designated as OCS-1.

[0073] (2) Preparation of oxidized chitosan phenolic resin:

[0074] The OCS-1 obtained in step (1) was mixed with phenol at a mass ratio of 1:0.68 and heated and stirred at pH=4.5 for 3 hours. After the reaction time was reached, the solid content was adjusted to 45% with ethanol to obtain oxidized chitosan phenolic resin, denoted as OCSPF-1.

[0075] (3) Nitrogen and phosphorus co-modification:

[0076] The OCSPF-1 obtained in step (2) is mixed with Formula 1A (R1 and R2 are both amino groups) and Formula 2 at a mass ratio of 1:0.15:0.6. Aluminum sulfate with a weight ratio of 1:0.005 of OCSPF-1 resin is added. The reaction temperature is 80℃ and the reaction time is 6h. The reaction forms a nitrogen-phosphorus co-modified resin, which is called grafted modified GOCSPF-1.

[0077] (4) Coated modified artificial graphite:

[0078] The carbon source (grafted modified GOCSPF-1 obtained in step (3)) was mixed with artificial graphite. The weight ratio of artificial graphite to GOCSPF-1 resin was 1:0.05. The mixture was mixed by fusion (800 rpm, 4 min). Then, it was kept at 700℃ for 6 h in a nitrogen atmosphere to form a carbonized layer. After depolymerization, demagnetization and sieving, the negative electrode active material product was obtained and was named CP-1.

[0079] Example 2

[0080] (1) Preparation of oxidized chitosan:

[0081] Chitosan was dissolved in 1% acetic acid solution, and sodium periodate oxidant was added. The mass ratio of chitosan to sodium periodate was 1:0.015. The oxidation reaction temperature was 20℃ and the reaction time was 8h. After the reaction was carried out in the dark, impurities were removed to obtain aldehyde-containing oxidized chitosan, which was designated as OCS-2.

[0082] (2) Preparation of oxidized chitosan phenolic resin:

[0083] The OCS-2 obtained in step (1) was mixed with phenol at a mass ratio of 1:1.02 and heated and stirred at pH=6.5 for 50°C and 6 hours. After the reaction time was reached, the solid content was adjusted to 45% with ethanol to obtain oxidized chitosan phenolic resin, denoted as OCSPF-2.

[0084] (3) Nitrogen and phosphorus co-modification:

[0085] The OCSPF-2 obtained in step (2) is mixed with Formula 1A and Formula 2 at a mass ratio of 1:0.4:0.15, and aluminum sulfate with a resin weight ratio of 1:0.015 is added. The reaction temperature is 120℃ and the reaction time is 3h to form a nitrogen-phosphorus co-modified resin, which is called grafted modified GOCSPF-2.

[0086] (4) Coated modified artificial graphite:

[0087] The GOCSPF-2 obtained in step (3) is mixed with artificial graphite at a weight ratio of 1:0.15. The mixture is then fused (400 rpm for 6 min) and kept at 1000℃ for 3 h in a nitrogen atmosphere to form a carbonized layer. After depolymerization, demagnetization, and sieving, the negative electrode active material is obtained and is denoted as CP-2.

[0088] Example 3

[0089] (1) Preparation of oxidized chitosan:

[0090] Chitosan was dissolved in 1% acetic acid solution, and sodium periodate oxidant was added. The mass ratio of chitosan to sodium periodate was 1:0.01. The oxidation reaction temperature was 25℃ and the reaction time was 10h. After the reaction was carried out in the dark, impurities were removed to obtain aldehyde-containing oxidized chitosan, which was designated as OCS-3.

[0091] (2) Preparation of oxidized chitosan phenolic resin:

[0092] The OCS-3 obtained in step (1) was mixed with phenol at a mass ratio of 1:0.90 and heated and stirred at pH=5 for 6 hours. After the reaction time was reached, the solid content was adjusted to 45% with ethanol to obtain oxidized chitosan phenolic resin, denoted as OCSPF-3.

[0093] (3) Nitrogen and phosphorus co-modification:

[0094] The OCSPF-3 obtained in step (2) was mixed with Formula 1A and Formula 2 at a mass ratio of 1:0.3:0.4 and reacted under the catalysis of aluminum sulfate. Aluminum chloride with a resin weight ratio of 1:0.01 was added. The reaction temperature was 100℃ and the reaction time was 4.5h to form a nitrogen-phosphorus co-modified resin, which is called grafted modified GOCSPF-3.

[0095] (4) Coated modified artificial graphite:

[0096] The grafted modified GOCSPF-3 (carbon source) obtained in step (3) is mixed with artificial graphite. The weight ratio of artificial graphite to resin is 1:0.1. The mixture is mixed by fusion (600 rpm, 5 min). Then, it is kept at 800℃ for 4 h in a nitrogen atmosphere to form a carbonized layer. After depolymerization, demagnetization and sieving, the negative electrode active material product is obtained and is denoted as CP-3.

[0097] Comparative Example 1

[0098] Compared with Example 3, the only difference is that in step 3, Formula 2 is missing. The missing Formula 2 is supplemented by Formula 1A in equal weight. All other operations and parameters are the same as in Example 3. The obtained material is labeled DB-1.

[0099] Comparative Example 2

[0100] Compared with Example 3, the only difference is that in step 3, Formula 1A is missing, and the missing Formula 1A is supplemented by Formula 2 in equal weight. All other operations and parameters are the same as in Example 3. The resulting material is labeled DB-2.

[0101] Comparative Example 3

[0102] Compared to Example 3, the only difference is that step 3 is omitted, and the oxidized chitosan phenolic resin prepared in step 2 is directly used as the carbon source in step 4. All other operations and parameters are the same as in Example 3. The resulting material is labeled DB-3.

[0103] Comparative Example 4

[0104] Compared to Example 3, the only difference is that step 3 is omitted. Instead, the oxidized chitosan phenolic resin prepared in step 2 and the physical mixture of Formula 1A and Formula 2 (with the same proportions as in step 3 of Example 3) are used directly as the carbon source in step 4. All other operations and parameters are the same as in Example 3. The resulting material is labeled DB-4.

[0105] Comparative Example 5

[0106] Compared to Example 3, the only difference is that step 2 is omitted. Instead, the OCS-3 obtained in step 1 is directly physically mixed with commercial phenolic resin (the weight ratio of OCS-3 to phenolic resin is 1:0.9), and this mixture replaces the OCSPF-3 in step 3 for step 3 and subsequent processing. All other operations and parameters are the same as in Example 3. The resulting material is designated DB-5.

[0107] Comparative Example 6

[0108] Compared with Example 3, the only difference is that steps 1 to 3 are not performed, and in step 4, conventional asphalt is used as the carbon source. All other operations and parameters are the same as in Example 1, and the resulting material is labeled DB-6.

[0109] Comparative Example 7

[0110] Compared with Example 1, the only difference is that chitosan is not processed in step 1, but is directly used as a raw material for step 2 and subsequent processing. The resulting material is labeled DB-7.

[0111] test:

[0112] Positive electrode: LiFePO4, acetylene black and PVDF are mixed in a weight ratio of 90:5:5 to obtain a positive electrode material, which is then composited onto a current collector to obtain an LFP positive electrode.

[0113] Negative electrode: The materials finally obtained in each case are used as negative electrode active materials. The negative electrode active material, acetylene black and PVDF are mixed in a weight ratio of 90:5:5 to obtain the negative electrode material, and then composited on the current collector to obtain the negative electrode.

[0114] The full-electric test used a pouch cell, which was assembled with 3 positive electrodes and 4 negative electrodes, using LFP positive and negative electrodes. The electrodes were cut to 35 mm × 52 mm and 39 mm × 56 mm, respectively. The electrodes were laminated to the PP separator in a zigzag pattern (negative electrode-sealant-positive electrode-sealant-negative electrode-sealant-positive electrode-sealant-negative electrode-sealant-positive electrode-sealant-negative electrode). Due to the small size of the battery, no additional venting bag was required. After removing moisture from the battery, 2.0 g of 1 M LiTFSI electrolyte was injected according to an appropriate E / C ratio (electrolyte / capacity = 4.0 g Ah⁻¹). To further analyze the cycling performance of the materials, the pouch cell was first activated at a rate of 0.1 C for 3 cycles, and then charged and discharged at a rate of 3 C within a voltage window of 1.0–2.5 V in an air-conditioned environment of 293 ± 2 K. The specific capacity of the pouch cell was calculated based on the mass of the LiFePO4 active material. The test was conducted at a pressure of 0.3 MPa, with pressure applied using a limit clamp.

[0115]

[0116] As shown in Table 1, the bio-based content of the resin prepared by the method of the present invention is ≥40%, no toxic formaldehyde is used, the environmental friendliness is improved, and it has excellent safety.

[0117]

[0118]

[0119] The conductivity improvement rate in Table 3 is the improvement amount compared to the blank sample, with Comparative Example 6 as the blank sample.

[0120]

[0121] This invention polymerizes oxidized chitosan and aromatic phenols, and then modifies them in combination with Formula 1 and Formula 2 to obtain a novel modified oxidized chitosan bio-based phenolic resin. This resin is innovatively used to modify graphite, enabling beneficial carbonization at lower temperatures, thereby improving the low-temperature conductivity, fast charging, safety, and long-cycle properties of the modified graphite.

Claims

1. A method for preparing modified oxidized chitosan bio-based phenolic resin, characterized in that, Chitosan is oxidized to obtain aldehyde-modified chitosan; aldehyde-modified chitosan and aromatic phenols are polymerized to obtain chitosan-phenolic resin; Modified oxidized chitosan bio-based phenolic resin was prepared by grafting chitosan-phenolic resin with Formula 1 and Formula 2. Formula 1 Formula 2 In Formula 1, R1 and R2 are individually H, C1~C3 alkyl or amino groups.

2. The method for preparing the modified oxidized chitosan bio-based phenolic resin as described in claim 1, characterized in that, The oxidizing agent for chitosan oxidation is periodate; Preferably, the mass ratio of chitosan to oxidant is 1:0.005~0.02; Preferably, the oxidation reaction temperature is 15~35℃; Preferably, the oxidation reaction takes 5 to 15 hours.

3. The method for preparing the modified oxidized chitosan bio-based phenolic resin as described in claim 1, characterized in that, Aromatic phenols are compounds having a structure of formula 3; Formula 3 In Formula 3, R3 is H, a C1-C3 alkyl group, a C1-C3 alkoxy group, or a hydroxyl group; Preferably, the mass ratio of aldehyde-modified chitosan to Formula 3 is 1:0.5~1.5; Preferably, the polymerization reaction is carried out under acidic conditions; Preferably, the pH of the polymerization reaction process is 4-7; Preferably, the polymerization reaction temperature is 45~85℃ and the polymerization reaction time is 2~8 hours.

4. The method for preparing the modified oxidized chitosan bio-based phenolic resin as described in claim 1, characterized in that, In Formula 1, R1 and R2 are both amino groups; Preferably, the mass ratio of chitosan-phenolic resin, Formula 1 and Formula 2 is 1:0.1~0.45:0.1~0.

65.

5. The method for preparing the modified oxidized chitosan bio-based phenolic resin as described in claim 1 or 4, characterized in that, The grafting modification process was carried out under Lewis acid catalysis; Preferably, the Lewis acid includes at least one of aluminum chloride, aluminum sulfate, and zinc chloride; Preferably, the mass ratio of chitosan-phenolic resin to Lewis acid is 1:0.005~0.015; Preferably, the reaction temperature for graft modification is 70~140℃, and the reaction time is 2~8 hours.

6. A modified oxidized chitosan bio-based phenolic resin prepared by the preparation method according to any one of claims 1 to 5.

7. The application of a modified oxidized chitosan bio-based phenolic resin prepared by the preparation method according to any one of claims 1 to 5, characterized in that, Modified graphite is obtained by combining it with graphite and then carbonizing it.

8. The application as described in claim 7, characterized in that, The weight ratio of the modified oxidized chitosan bio-based phenolic resin to graphite is 0.02~0.2:1; Preferably, the carbonization temperature is above 650°C, and more preferably it is 700~1000°C; Preferably, the carbonization time is 2 to 8 hours.

9. A negative electrode, characterized in that, It includes the modified graphite prepared in the application described in claim 7 or 8.

10. A battery, characterized in that, It includes the negative electrode as described in claim 9.

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