A lignin derivative composite binder, a preparation method and application of a silicon-based negative electrode sheet thereof
By preparing a composite binder of polyacrylic acid and polyethylene glycol grafted lignin, a flexible and controllable three-dimensional network structure was constructed, which solved the problem of insufficient cycle performance and rate performance of existing lithium-ion battery anode binders, and achieved efficient and stable operation of the battery.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- GUANGDONG UNIV OF TECH
- Filing Date
- 2025-03-31
- Publication Date
- 2026-06-16
AI Technical Summary
Existing lithium-ion battery anode binders are still not very effective in improving battery cycle performance and rate performance. Furthermore, traditional binders are complex to construct and easily damaged when building three-dimensional cross-linked network structures, which leads to a decline in electrochemical performance.
A lignin derivative composite binder was prepared by heating and reacting lignin grafted with polyacrylic acid and polyethylene glycol in a solvent. By constructing a flexible and controllable three-dimensional network structure, the conductivity and stress dissipation capacity of the binder were improved, and the stability of the electrode was enhanced.
It significantly improves the cycle performance and rate performance of lithium-ion batteries, enhances the mechanical strength of electrodes and the stability of conductive networks, promotes rapid lithium-ion transport, and improves the overall performance of the battery.
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Figure CN120137591B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of battery materials technology, and more specifically, to a lignin derivative composite binder and its preparation method and application in silicon-based anode sheets. Background Technology
[0002] With the rapid development of the new energy vehicle industry, the demand for power batteries is constantly increasing, and the demand for high-energy-density lithium-ion batteries is also growing accordingly. Although lithium-ion batteries have made significant progress in the field of energy storage, the energy density of their electrode materials is still limited. In order to further improve the energy storage capacity of lithium-ion batteries, researchers are constantly exploring new electrode materials and innovative technologies in order to achieve high-energy-density lithium-ion batteries in practical applications. They are working hard to find and optimize electrode materials with higher energy density. Silicon-based materials, with their excellent high theoretical specific capacity, are highly anticipated by researchers and are considered to be the ideal anode material for high-energy-density lithium-ion batteries.
[0003] However, during battery charging and discharging, silicon-based materials experience problems such as large volume expansion, active material pulverization, and instability of the solid electrolyte interface film. To promote the widespread application of silicon-based materials in lithium-ion batteries, researchers are actively studying and exploring effective ways to solve these problems.
[0004] Binders play a significant role in maintaining the integrity of electrode structure and conductive network. Therefore, addressing the volume effect problem in silicon-based materials by focusing on binders is the simplest and lowest-cost approach. Traditional binders, however, have adhesive properties and mechanical properties that are ill-suited to the volume effect of silicon-based materials, making it difficult to maintain the long-term cycle stability of the electrode. Therefore, it is necessary to develop novel binders, such as three-dimensional crosslinking binders, self-healing binders, and conductive binders. Thus, developing multifunctional three-dimensional binders holds promise for comprehensively solving the cycle stability problem of silicon-based anodes in lithium-ion batteries.
[0005] Developing novel silicon-based anode binders has become a research hotspot, and a series of binders have been successfully designed. However, the process of constructing the three-dimensional cross-linked network structure with these binders is complex, and they break down and are difficult to repair when they reach their strength limit, leading to a sharp decline in electrochemical performance. Meanwhile, the low conductivity of silicon-based materials requires the addition of more conductive agents to ensure the coverage of the conductive network. Excessive addition of conductive agents can compromise the cycle stability of electrodes with high active material loading, thus hindering the achievement of high-energy-density lithium-ion batteries.
[0006] Existing technology discloses a lignin-based aqueous composite battery binder and its preparation method and application in silicon-based anode sheets. The preparation method of the silicon-based anode sheet based on the lignin-based aqueous battery binder includes the following steps: dissolving polyacrylic acid, sulfonated lignin, sodium thiooctanoate, silicon-based active materials, and conductive materials in water, mixing them evenly to obtain a negative electrode slurry, then coating the negative electrode slurry onto a substrate, and finally drying and thermally esterifying at high temperature to obtain the anode sheet. This silicon-based anode sheet based on the lignin-based aqueous binder has strong adhesion and effectively suppresses the volume effect of the silicon-based anode sheet during charge and discharge, improving the cycle performance of the silicon-based anode sheet. At a current density of 0.2 A / g, after 100 cycles, the prepared silicon suboxide electrode still retains a discharge specific capacity of 1192 mAh / g. However, its cycle performance is still relatively low and needs further improvement. Summary of the Invention
[0007] The technical problem to be solved by the present invention is to overcome the shortcomings of existing binders for lithium-ion battery anodes, which still have a relatively low improvement in battery cycle performance. The invention provides a lignin derivative composite binder that can not only significantly improve the cycle performance of the battery, but also improve the rate performance of the battery.
[0008] Another object of the present invention is to provide a lithium-ion battery negative electrode slurry.
[0009] Another object of the present invention is to provide a lithium-ion battery negative electrode sheet.
[0010] Another object of the present invention is to provide a lithium-ion battery.
[0011] The above-mentioned objective of this invention is achieved through the following technical solution:
[0012] A lignin derivative composite adhesive is prepared by the following method: polyacrylic acid and polyethylene glycol grafted lignin are heated and reacted in a solvent to obtain the lignin derivative composite adhesive; wherein the weight of polyethylene glycol grafted lignin is 5-55% of the total weight of polyacrylic acid and polyethylene glycol grafted lignin, and the reaction temperature of the heating reaction is 70-170℃.
[0013] Lignin has multifunctional group characteristics and a natural three-dimensional skeleton structure. By introducing polyethylene glycol segments through grafting modification, the phenolic hydroxyl groups of lignin can be converted into alcoholic hydroxyl groups, thereby improving the hydroxyl activity of lignin.
[0014] A flexible and controllable three-dimensional network lignin is constructed using the elastic polymer polyethylene glycol (PEG) as the crosslinking chain, and then combined with the rigid polymer polyacrylic acid to prepare a three-dimensional structural binder with high ionic conductivity. The crosslinking network functionalization of lignin addresses the problem of low functional group reactivity caused by lignin cohesion. Simultaneously, the coiling and straightening of the PEG covalent crosslinking chains also assists in stress dissipation and the elastic stretching and contraction of the crosslinking network. The continuous ether bonds on PEG also facilitate the directional transport of lithium ions, and have a positive effect on improving the rate performance of SiO electrodes and overcoming lithium ion transport barriers caused by thickness issues at high loads. Therefore, the lignin derivative composite binder of this invention can improve the cycle performance and rate performance of lithium-ion batteries.
[0015] Lignin is a renewable biological resource, which can save resources and energy to a certain extent, thus responding to the goal of green and sustainable development.
[0016] Polyacrylic acid can be obtained commercially or made at home.
[0017] Polyacrylic acid can be synthesized by thermally initiated free radical polymerization.
[0018] Preferably, the solvent can be 1,4-dioxane.
[0019] In this invention, the weight of polyethylene glycol grafted lignin can be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or 55% of the total weight of polyacrylic acid and polyethylene glycol grafted lignin.
[0020] In this invention, the reaction temperature of the heating reaction can be 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, or 170℃.
[0021] Preferably, the weight of polyethylene glycol grafted lignin is 10-30% of the total weight of polyacrylic acid and polyethylene glycol grafted lignin.
[0022] The weight of polyethylene glycol grafted lignin accounts for a slightly smaller proportion of the total weight of polyacrylic acid and polyethylene glycol grafted lignin, which is more conducive to improving the cycle performance and rate performance of silicon-based anode lithium-ion batteries.
[0023] Preferably, the reaction temperature of the heating reaction is 100–165°C. A higher heating temperature is beneficial for the thermal esterification reaction of lignin grafted with polyacrylic acid and polyethylene glycol, resulting in a binder that improves the cycle performance and rate performance of silicon-based lithium-ion batteries.
[0024] Preferably, the reaction time for the heating reaction can be 6 to 10 hours.
[0025] Preferably, the preparation method of the polyethylene glycol grafted modified lignin includes the following steps: heating and reacting lignin and polyethylene glycol in concentrated sulfuric acid to obtain the polyethylene glycol grafted modified lignin.
[0026] Concentrated sulfuric acid acts as a catalyst and dehydrates the reaction in this process. As a strong acid, it significantly lowers the activation energy and accelerates the cross-linking reaction between lignin and PEG. Through protonation, it makes the active sites of the reactants more susceptible to nucleophilic attack, thus promoting the formation of ether bonds (-COC-). Lignin molecules contain numerous hydroxyl (-OH) groups, which concentrated sulfuric acid can protonate, making them more readily react with other molecules. Furthermore, concentrated sulfuric acid has strong dehydrating properties, removing water from the reaction system and driving the reaction towards the formation of cross-linked products. This dehydration helps form stable ether bonds, further promoting the formation of the cross-linked network.
[0027] Preferably, after the reaction is complete, the reactants can be dropped into water to form a flocculent precipitate. After centrifugation, the precipitate is washed with water several times and then dried in a vacuum oven to obtain polyethylene glycol grafted lignin.
[0028] Preferably, the lignin is alkali lignin.
[0029] Preferably, the mass ratio of lignin to polyethylene glycol is 1:(4-6).
[0030] Preferably, in the method for preparing polyethylene glycol grafted modified lignin, the heating reaction time is 4-5 hours and the heating reaction temperature is 150-160°C.
[0031] This invention also protects a lithium-ion battery negative electrode slurry, comprising a negative electrode active material, a conductive agent, and a negative electrode binder, wherein the negative electrode binder is a lignin derivative composite binder as described above.
[0032] The negative electrode active material can be silicon suboxide or silicon.
[0033] In the preparation of lithium-ion battery negative electrode slurry, the negative electrode active material SiO and the conductive agent conductive carbon black are mixed at a certain mass ratio, and a suitable mass is weighed into an agate ball mill jar, with the material volume not exceeding 1 / 2 of the ball mill jar. The SiO and conductive carbon black mixture is ball milled at a certain speed. Then, the active material, conductive agent, and binder are prepared into a lithium-ion battery negative electrode slurry according to a certain mass ratio.
[0034] Among them, ball milling not only reduces the particle size of SiO, making it finer, but also helps conductive carbon black to be evenly distributed on the surface of SiO, thereby constructing a highly efficient conductive network.
[0035] In the negative electrode slurry, the mass fraction of the conductive agent can be 10-20%.
[0036] This invention also protects a silicon-based negative electrode sheet for a lithium-ion battery, comprising a negative electrode current collector and a negative electrode active material layer disposed on the surface of the negative electrode current collector, wherein the negative electrode active material layer is obtained by drying the aforementioned lithium-ion battery negative electrode slurry.
[0037] The present invention also protects a lithium-ion battery, comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte, wherein the negative electrode is the lithium-ion battery negative electrode described above.
[0038] Compared with the prior art, the beneficial effects of the present invention are:
[0039] This invention discloses a lignin derivative composite binder, prepared by heating lignin grafted with polyacrylic acid and polyethylene glycol in a solvent. The polyethylene glycol-grafted lignin is a flexible, controllable three-dimensional network lignin constructed using the elastic polymer polyethylene glycol as the crosslinking chain. This network is further prepared by reacting it with the rigid polymer polyacrylic acid to obtain a highly ionicly conductive three-dimensional lignin derivative composite binder. The introduction of lignin improves rate performance, and the polyethylene glycol grafted onto the lignin facilitates the rapid directional transport of lithium ions, significantly enhancing the rate performance and long-cycle performance at high current densities of silicon-based lithium-ion batteries. Attached Figure Description
[0040] Figure 1 Peel-off performance diagram of negative electrode sheets prepared with different binders at 180°.
[0041] Figure 2 0.5Ag -1 Cyclic diagrams of batteries prepared with different binders at different current densities.
[0042] Figure 3 Rate capability diagrams of batteries prepared with different binders.
[0043] Figure 4 Impedance diagrams of batteries prepared with different binders after 5 cycles. Detailed Implementation
[0044] The present invention will be further described below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise stated, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents.
[0045] Alkali lignin was provided by Zhejiang Jiefa Technology Co., Ltd.
[0046] Example 1
[0047] A lignin derivative composite adhesive is prepared by the following method:
[0048] Preparation of polyethylene glycol grafted lignin (LPEG):
[0049] The polymerization inhibitor was removed from the acrylic monomer by column chromatography. 50g of purified acrylic acid and 100g of deionized water were placed in a three-necked flask, and 0.25g of ammonium persulfate (APS) was added as a thermal initiator. The reaction was carried out under a nitrogen atmosphere at 60°C with high-speed stirring for 3 hours to obtain high-viscosity polyacrylic acid. The product was cut into small pieces, washed repeatedly with water, and then freeze-dried to obtain polyacrylic acid.
[0050] 5g of alkali lignin and 25g of polyethylene glycol were placed in a flask. After the lignin was completely dispersed in the polyethylene glycol, 200μL of concentrated sulfuric acid was added at 160℃ and the reaction was carried out for 4h. The reactants were then added dropwise to 2L of deionized water to form a flocculent precipitate. After centrifugation, the precipitate was washed several times with deionized water and then dried in a vacuum oven at 60℃ to obtain polyethylene glycol grafted lignin (LPEG).
[0051] A binder solution was prepared by dissolving polyacrylic acid and polyethylene glycol grafted lignin in a 9:1 ratio in 1,4-dioxane. After stirring evenly, the solution was heated and dried at 150°C for 8 hours to obtain a lignin derivative composite binder with high ionic conductivity. At this point, the weight of polyethylene glycol grafted lignin was 10% of the total weight of polyacrylic acid and polyethylene glycol grafted lignin.
[0052] Preparation of negative electrode slurry: The negative electrode active material SiO and conductive carbon black were mixed at a mass ratio of 7:2, and the mixture was ball-milled at 400 r / min for 10 h. The negative electrode active material, conductive agent, and binder were then prepared into a negative electrode slurry at a mass ratio of 7:2:1.
[0053] Preparation of the negative electrode sheet: After stirring the negative electrode slurry for 5-6 hours to ensure thorough mixing, the slurry is then coated using a scraper to obtain an active material loading of 1.0 mg / cm³. -2 The wetted electrode was placed in a 60°C forced-air drying oven for 1-2 hours to remove most of the solvent, followed by drying in an 80°C vacuum drying oven for 10 hours to completely remove any remaining solvent. The dried electrode sheet was then cut into 12 mm diameter pieces using a slicer.
[0054] Lithium-ion battery fabrication: Polypropylene was used as the battery separator, and a mixed electrolyte of ethylene carbonate and diethyl carbonate containing 1 mol LiPF6, 10 wt% fluoroethylene carbonate, and 1 wt% vinylene carbonate was used as the battery electrolyte, with a volume ratio of ethylene carbonate to diethyl carbonate of 1:1. CR2032 coin cell assembly was performed in an argon-filled glove box.
[0055] Example 2
[0056] A lignin derivative composite adhesive is prepared by the following method:
[0057] A binder solution was prepared by dissolving polyacrylic acid and polyethylene glycol grafted lignin in a 9:1 ratio in 1,4-dioxane. After stirring evenly, the solution was heated and dried at 80°C for 8 hours to obtain a lignin derivative composite binder with high ionic conductivity. The weight of the polyethylene glycol grafted lignin was 10% of the total weight of the polyacrylic acid and polyethylene glycol grafted lignin.
[0058] The difference from Example 1 is that the reaction temperature of the heating reaction is 80°C.
[0059] The rest is the same as in Example 1, and will not be repeated here.
[0060] Example 3
[0061] A lignin derivative composite adhesive is prepared by the following method:
[0062] A binder solution was prepared by dissolving polyacrylic acid and polyethylene glycol grafted lignin in a 7:3 ratio in 1,4-dioxane, stirring until homogeneous, and then heating and drying at 80°C for 8 hours to obtain a lignin derivative composite binder with high ionic conductivity.
[0063] The difference from Example 1 is that the weight of polyethylene glycol grafted lignin is 30% of the total weight of polyacrylic acid and polyethylene glycol grafted lignin. The reaction temperature for the heating reaction is 80°C.
[0064] The rest is the same as in Example 1, and will not be repeated here.
[0065] Example 4
[0066] A lignin derivative composite adhesive is prepared by the following method:
[0067] A binder solution was prepared by dissolving polyacrylic acid and polyethylene glycol grafted lignin in a 5:5 ratio in 1,4-dioxane, stirring until homogeneous, and then heating and drying at 80°C for 8 hours to obtain a lignin derivative composite binder with high ionic conductivity.
[0068] The difference from Example 1 is that the weight of polyethylene glycol grafted lignin is 50% of the total weight of polyacrylic acid and polyethylene glycol grafted lignin. The reaction temperature for the heating reaction is 80°C.
[0069] The rest is the same as in Example 1, and will not be repeated here.
[0070] Comparative Example 1
[0071] A silicon-based anode binder for lithium-ion batteries is prepared by the following method: polyacrylic acid is dissolved in 1,4-dioxane to prepare a binder solution, which is stirred evenly and then dried for 8 hours to obtain binder PAA.
[0072] The preparation method of polyacrylic acid is the same as that of polyacrylic acid in Example 1.
[0073] Comparative Example 2
[0074] A silicon-based anode binder for lithium-ion batteries is prepared by the following method: polyacrylic acid and polyethylene glycol are compounded and dissolved in 1,4-dioxane in a ratio of 9:1 to prepare a binder solution. After stirring evenly, the solution is dried at 80°C for 8 hours to obtain a lignin derivative composite binder with high ionic conductivity.
[0075] The rest is the same as in Example 1, and will not be repeated here.
[0076] Result detection
[0077] The binders used in Examples 2-4 and Comparative Examples 1-2 were used to prepare lithium-ion battery negative electrode sheets using the same method as in Example 1. The following mechanical properties were then tested: A 180° peel test was performed using a CMT6203 microcomputer-controlled electronic universal testing machine from Shenzhen Sansi Experimental Instrument Co., Ltd. The electrode sheet was cut into a 50mm × 18mm rectangle, and 18mm wide 3M tape was adhered to the coated surface of the electrode sheet. The peel test was conducted at 100mm min... -1 The peeling rate was tested at 180°.
[0078] Test results are as follows Figure 1 As shown:
[0079] The adhesive in Example 2 achieved a maximum bond strength of 4.0 N. This was due to the synergistic effect of multi-layered and multi-directional synergy when the ratio of polyacrylic acid to polyethylene glycol-grafted lignin reached 9:1. Furthermore, the electrode material was less prone to detachment during battery cycling. In contrast, the adhesive in Comparative Example 1 had a bond strength of 3.5 N.
[0080] Peel strength tests demonstrated the role of network-structured alkali lignin in improving bond strength. The addition of polyethylene glycol-grafted lignin increases the elasticity and toughness of the material, aiding stress dissipation and network resilience; however, increasing its content reduces the stress of the composite material. As shown in the attached figures, the peel strength of the electrode sheet in Example 2 is significantly improved. Example 2 demonstrates the formation of a stable bonding interface, providing multi-directional bonding sites, thereby enhancing bond strength. Furthermore, electrode material detachment is less likely to occur during battery cycling.
[0081] Lithium-ion batteries were prepared using the binders from Examples 2-4 and Comparative Examples 1-2 respectively, following the same method as in Example 1, and their performance was tested as follows:
[0082] (1) Constant current charge-discharge test: The constant current charge-discharge test records the battery's cycle performance and rate performance data under a constant current density. The test uses the Xinwei charge-discharge test system to test the battery's cycle performance and rate performance. The battery test conditions are a constant temperature of 25℃. The battery needs to be left to stand for 10 hours before cycling and activated once with a small current before the constant current charge-discharge test is performed.
[0083] Cyclic performance: Each example was tested at 0.5 Ag. -1 Constant current charge-discharge tests were performed at a current density of [value missing].
[0084] The specific test results of the cycling performance of each embodiment and comparative example are shown in Table 1 below. Figure 2 As shown:
[0085] Table 1
[0086] Group Number of cycles <![CDATA[Discharge specific capacity (mAh g -1 )]]> Example 1 500 1053.73 Example 2 500 682.99 Example 3 500 321.65 Example 4 370 78.01 Comparative Example 1 200 418.82
[0087] The specific test results of the rate performance of each embodiment and comparative example are shown in Table 2 below. Figure 3 As shown:
[0088] Table 2
[0089]
[0090] After thermal esterification crosslinking, the electrode prepared with the binder of Example 1 was subjected to 1Ag... -1 The current density is still 788.21 mAh g. -1 The capacity. When the current density returns to 0.2Ag. -1 At that time, the electrode prepared with the binder in Example 1 still had 1739.98 mAh g. -1 The capacity indicates that the electrode in this embodiment of the invention has excellent rate performance.
[0091] The charge-discharge cycle test results show that the lignin derivative composite binder of the present invention has excellent cycle performance and rate performance, and the discharge specific capacity decreases less under stepped current density; in constant current charge-discharge, it exhibits excellent performance at a high current density of 0.5 Ag. -1 Under these conditions, it maintained a high specific capacity for long-term cycling.
[0092] As can be seen from Examples 1 and 2, Example 1 uses a high-temperature thermal esterification crosslinking reaction, resulting in a higher discharge specific capacity. This is because after thermal esterification crosslinking, polyacrylic acid and polyethylene glycol grafted modified lignin form a more robust covalent crosslinking network. The covalent-non-covalent crosslinking network formed by the binder in Example 1 has greater structural stability than the hydrogen bond crosslinking network formed by the binder in Example 2, thereby improving the cycle life and electrochemical performance of the electrode.
[0093] As can be seen from Examples 2-4, in the preparation method of lignin-based binders, the weight of polyethylene glycol grafted modified lignin is 10-30% of the total weight of polyacrylic acid and polyethylene glycol grafted modified lignin, and the prepared lignin derivative composite binder has better cycle performance and rate performance.
[0094] The SiO electrode prepared by the binder without cross-linked lignin in Comparative Example 1 was subjected to a 0.5 Ag... -1 It can only cycle 200 times at a current density and has a capacity of only 418.82 mAh g. -1 The capacity is in 1Ag -1 At a current density of only 146 mAh g -1 The low capacity is likely due to the lack of a lignin-supported three-dimensional framework, which makes it difficult to maintain the integrity of the electrode, leading to contact failure of the conductive network during rapidly changing rate tests. The SiO electrode in Comparative Example 2 also exhibits poor rate performance.
[0095] It is evident that lignin can improve rate performance, and the introduction of the lithium-conducting segment PEG helps to synergize with lignin for rapid and directional transport of lithium ions, thereby achieving higher and more stable rate performance.
[0096] (2) Ionic conductivity, interfacial impedance and ion diffusion rate
[0097] Electrochemical impedance spectroscopy (EIS): EIS involves applying a sinusoidally varying cross-linking perturbation voltage to the electrode, causing the electrode voltage to change according to a sinusoidal wave pattern. This allows for the generation of an impedance spectrum, which can then be used to study electrode kinetics and ion diffusion mechanisms. The test was conducted using an electrochemical workstation, applying a sinusoidal AC voltage with an amplitude of 5 mV to the battery within a frequency range of 0.01 Hz to 100 kHz at room temperature.
[0098] Electrochemical impedance spectroscopy was performed on half-cells with different binders, and the test results are as follows: Figure 4 As shown. From the appendix Figure 4 It can be seen that after five cycles, Example 1 has the lowest impedance, which is 30.29Ω, Example 2 is 45.58Ω, and Comparative Example 1 is 63.45Ω, indicating that the binder has a good wetting effect on the electrolyte. The slope of the low-frequency region of Examples 1 and 2 is higher than that of Comparative Example 1, indicating that the electrode can maintain the stability of the electrode and the integrity of the conductive network during cycling, and a stable SEI is generated, resulting in better charge transfer effect. The introduction of polyethylene glycol grafted modified lignin also improves the ion diffusion rate and ionic conductivity, thereby reducing impedance.
[0099] It can be seen that the ionic conductivity and ion diffusion rate of the embodiments of the present invention are significantly improved, and the electrodes prepared therefrom have a smaller interfacial impedance.
[0100] The results above show that the lignin derivative composite binder of the present invention, due to its certain mechanical properties, reduces the volume effect during the charging and discharging process of the SiO negative electrode, and promotes the transport of lithium ions while maintaining the integrity of the conductive network, thus significantly improving its rate performance and long-cycle performance at high current density.
[0101] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.
Claims
1. A lignin derivative composite binder, characterized in that, The lignin-derived composite binder is prepared by heating polyacrylic acid and polyethylene glycol grafted lignin in a solvent to obtain a lignin-derived composite binder; wherein the weight of polyethylene glycol grafted lignin is 5-55% of the total weight of polyacrylic acid and polyethylene glycol grafted lignin, and the reaction temperature of the heating reaction is 70-170℃.
2. The lignin derivative composite binder as described in claim 1, characterized in that, The weight of polyethylene glycol grafted lignin is 10-30% of the total weight of polyacrylic acid and polyethylene glycol grafted lignin.
3. The lignin derivative composite binder as described in claim 1, characterized in that, The reaction temperature of the heating reaction is 100–165°C.
4. The lignin derivative composite binder as described in claim 1, characterized in that, The preparation method of the polyethylene glycol grafted modified lignin includes the following steps: heating lignin and polyethylene glycol in concentrated sulfuric acid to obtain the polyethylene glycol grafted modified lignin.
5. The lignin derivative composite adhesive as described in claim 4, characterized in that, The lignin is alkali lignin.
6. The lignin derivative composite binder as described in claim 4, characterized in that, The mass ratio of lignin to polyethylene glycol is 1:(4-6).
7. The lignin derivative composite binder as described in claim 4, characterized in that, In the preparation method of the polyethylene glycol grafted modified lignin, the heating reaction time is 4-5 hours and the heating reaction temperature is 150-160℃.
8. A lithium-ion battery negative electrode slurry, characterized in that, It includes a negative electrode active material, a conductive agent, and a negative electrode binder, wherein the negative electrode binder is the lignin derivative composite binder according to any one of claims 1 to 7.
9. A lithium-ion battery negative electrode sheet, characterized in that, It includes a negative electrode current collector and a negative electrode active material layer disposed on the surface of the negative electrode current collector, wherein the negative electrode active material layer is obtained by drying the lithium-ion battery negative electrode slurry according to claim 8.
10. A lithium-ion battery, characterized in that, It includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte, wherein the negative electrode is the lithium-ion battery negative electrode as described in claim 9.