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CN-121975455-A - Preparation method and application of crosslinked nanocellulose lithium battery binder

CN121975455ACN 121975455 ACN121975455 ACN 121975455ACN-121975455-A

Abstract

The invention discloses a preparation method and application of a crosslinked nanocellulose lithium battery binder, and belongs to the technical field of lithium ion battery binders. The preparation method comprises the steps of introducing a rigid crystalline nano body TOCNF as an enhancement phase in the preparation process of the crosslinking nano cellulose lithium battery binder, adopting calcium citrate, citric acid or phytic acid as a green crosslinking agent, forming a multiple hydrogen bond effect and a chemical crosslinking structure in a system in a synergistic manner, constructing a stable three-dimensional network, effectively inhibiting expansion and cracking of a silicon-based electrode, remarkably improving the circulation stability and capacity retention rate of the silicon-based electrode, constructing a full-aqueous system by taking a plant source TOCNF as a core and matching with a green biodegradable crosslinking agent, discarding a toxic organic solvent, and conforming to the environmental protection and circulation economy concepts. When the silicon-based lithium ion battery negative electrode plate material is prepared, a collaborative three-dimensional network is constructed by introducing TOCNF and a cross-linking agent, and the volume expansion and the electrode plate cracking of SiOx are effectively inhibited by combining SBR elastic buffering, so that the cycling stability and the capacity retention rate of the silicon-based electrode are remarkably improved.

Inventors

  • WANG HUIQING
  • LI XIANG
  • GUO ZHICAI

Assignees

  • 合肥工业大学

Dates

Publication Date
20260505
Application Date
20260202

Claims (10)

  1. 1. The preparation method of the crosslinking nanocellulose lithium battery binder is characterized by comprising the following steps of: Sequentially adding CMC powder and a crosslinking agent into a TOCNF suspension containing TOCNF, stirring and mixing uniformly, and performing ultrasonic dispersion to obtain the crosslinking nanocellulose lithium battery binder, wherein the mass ratio of TOCNF to the crosslinking agent in the CMC powder and TOCNF suspension is 6-10:2-6:5-10.
  2. 2. The preparation method of the crosslinked nanocellulose lithium battery binder according to claim 1, wherein the viscosity of CMC powder is 1200-4500 mPa.s, the weight average molecular weight is 300000-700000, the substitution degree is 0.8-1.4, and the purity is more than or equal to 99.5% at 25 ℃ in a 1wt% aqueous solution.
  3. 3. The preparation method of the crosslinked nanocellulose lithium battery binder is characterized in that the crosslinking agent is a crosslinking system based on polyvalent metal salts or phosphate esters of polybasic organic acids, the polybasic organic acids are citric acid, the polyvalent metal salts are aluminum citrate or calcium citrate, and the phosphate esters are phytic acid.
  4. 4. The preparation method of the crosslinked nanocellulose lithium battery binder according to claim 1, wherein the TOCNF has an aspect ratio of 200-2000, a diameter of 1-20 nm and a carboxyl content of 1.3-2.5 mmol/g.
  5. 5. The method for preparing the crosslinked nanocellulose lithium battery binder as claimed in claim 1 wherein said TOCNF suspension is prepared by the steps of: Preparing cellulose oxidized by TEMPO into slurry with the solid content of 0.8% -1.2% by using deionized water, homogenizing for 6-10 times by using 150-200 mpa pressure in a high-pressure homogenizer, stripping the cellulose oxidized by TEMPO into cellulose nanofibers, and regulating the cellulose nanofibers to the solid content of 0.2% -0.8% by using deionized water to obtain TOCNF suspension.
  6. 6. The method for preparing the crosslinking nano-cellulose lithium battery binder according to claim 5, wherein the TEMPO oxidized cellulose is prepared by the following steps: Adding TEMPO and NaBr into deionized water in sequence, stirring and dissolving at 15-25 ℃, adding crushed and dried cellulose raw materials into a reaction system, stirring and dispersing, adding NaClO solution into the system, dripping NaOH solution with the concentration of 0.4-0.6 mol/L, regulating the pH value of the reaction system to 10.5-11, reacting for 4-7 h, centrifugally washing the product, and washing the product with deionized water for 5-8 times to obtain the cellulose oxidized by TEMPO.
  7. 7. The preparation method of the crosslinked nanocellulose lithium battery binder according to claim 6 is characterized in that the effective chlorine content in NaClO solution is 6-14wt%, and the dosage ratio of TEMPO, naBr, deionized water, dried cellulose fiber raw material and NaClO solution is 0.8g:5 g:4500-4800 mL:46-49 g:372-374g.
  8. 8. The application of the cross-linked nano-cellulose lithium battery binder in the silicon-based lithium ion battery negative electrode plate material is characterized in that the cross-linked nano-cellulose lithium battery binder is prepared by the preparation method of any one of claims 1-7.
  9. 9. The use according to claim 8, wherein the silicon-based lithium ion battery negative electrode sheet material is prepared by: Adding a crosslinking nano cellulose lithium battery binder, a conductive agent and silicon oxide powder into a homogenizing kettle in sequence, mixing and dispersing for 5-6 hours at 700-900 rpm to obtain a negative electrode slurry, coating the negative electrode slurry on a copper foil, carrying out vacuum preheating for 2-3 hours at 60-90 ℃, and carrying out vacuum drying for 12-14 hours at the vacuum degree of-0.1 MPa and the temperature of 60-90 ℃ to obtain the silicon-based lithium ion battery negative electrode plate material.
  10. 10. The use according to claim 8, wherein the silicon-based lithium ion battery negative electrode sheet material is prepared by: Adding a crosslinking nano cellulose lithium battery binder, a conductive agent and silicon oxide powder into a homogenizing kettle in sequence, mixing and dispersing for 5-6 hours at 700-900 rpm, adding SBR, mixing for 0.5-1 hour at 500-600 rpm to obtain a negative electrode slurry, coating the negative electrode slurry on a current collector, carrying out vacuum preheating for 2-3 hours at 60-90 ℃, and carrying out vacuum drying for 12-14 hours at the vacuum degree of-0.1 MPa and the temperature of 60-90 ℃ to obtain the silicon-based lithium ion battery negative electrode plate material.

Description

Preparation method and application of crosslinked nanocellulose lithium battery binder Technical Field The invention belongs to the technical field of battery binders, and particularly relates to a preparation method and application of a crosslinked nanocellulose lithium battery binder. Background Lithium ion batteries are currently the mainstream energy storage devices, and the improvement of energy density is always the core research topic in industry and academia. Silicon-based materials, particularly silicon oxide powders (SiOx), are significantly higher than the theoretical specific capacity of conventional graphite (about 950 mAh-g -1). However, siOx materials undergo a great volume expansion during charge and discharge, which causes the active material particles to be easily pulverized, the electrode structure to be damaged, and the solid electrolyte interface film (SEI) to be repeatedly broken and regenerated, and the process can irreversibly consume the electrolyte and the lithium source, resulting in rapid degradation of the battery capacity and rapid shortening of the cycle life, thereby impeding the commercialized application process. To address the challenges described above, the development of high performance binder systems is considered one of the key strategies to inhibit volumetric expansion of silicon-based cathodes. Aqueous binders, such as sodium carboxymethyl cellulose (CMC) and Styrene Butadiene Rubber (SBR) composite systems, have gradually replaced the conventional polyvinylidene fluoride (PVDF) due to their excellent binding properties and environmental friendly characteristics. The polar functional groups on the CMC molecular chain can interact with the SiOx surface through hydrogen bonds to provide rigid support, and SBR serves as an elastic component to buffer stress. However, under the severe volume change for a long time, the mechanical strength and toughness of the CMC/SBR system are still insufficient, the pole piece is still easy to crack, the electrode structure is still likely to be damaged in the later period of circulation, the circulation stability is poor, and the capacity retention rate is low. Therefore, developing a new binder capable of constructing a more stable and stronger three-dimensional crosslinked network to more effectively solve the problem of rapid decrease of specific capacity caused by volume expansion of SiOx negative electrode becomes a technical bottleneck to be broken through in the field. Disclosure of Invention The invention aims to provide a preparation method and application of a cross-linked nanocellulose lithium battery binder, wherein the preparation method and application of the cross-linked nanocellulose lithium battery binder take calcium citrate/aluminum citrate/citric acid/phytic acid as a green cross-linking agent by introducing carboxyl-rich rigidity TOCNF as a reinforcing phase, and the cross-linked nanocellulose lithium battery binder is applied to a high-capacity lithium battery silicon-based electrode, and cooperates with a TOCNF crystal skeleton, hydrogen bonding and chemical cross-linking to jointly strengthen a more stable three-dimensional network structure, so that the circulation stability and capacity retention rate of the silicon-based electrode can be remarkably improved, and the cracking of a pole piece can be inhibited. The aim of the invention can be achieved by the following technical scheme: the preparation method of the crosslinking nanocellulose lithium battery binder comprises the following steps: And adding CMC powder and cross-linking agent powder into TOCNF suspension liquid successively, and stirring and mixing uniformly to obtain the cross-linked nano cellulose lithium battery binder. Further, the mass ratio of TOCNF to the cross-linking agent in the CMC powder and TOCNF suspension is 6-10:2-6:5-10. Further, the crosslinking agent is a crosslinking system based on polyvalent metal salt or phosphate of a polybasic organic acid, the polybasic organic acid is citric acid, the polyvalent metal salt is aluminum citrate or calcium citrate, and the phosphate is phytic acid. Further, the CMC powder has a viscosity of 1200-4500 mPas (1% aqueous solution, 25 ℃) and a weight average molecular weight of 300000-700000, a substitution degree of 0.8-1.4, and a purity of not less than 99.5%. Further, TOCNF has an aspect ratio of 200 to 2000, a diameter of 1 to 20nm, and a carboxyl content of 1.3mmol/g to 2.5mmol/g. Further, TEMPO nanocellulose suspensions were prepared by the following steps: Preparing cellulose oxidized by TEMPO into slurry with the solid content of 0.8% -1.2% by using deionized water, homogenizing for 6-10 times by using 150-200 mpa pressure in a high-pressure homogenizer, stripping the cellulose oxidized by TEMPO into cellulose nanofibers, and regulating the cellulose nanofibers to the solid content of 0.2% -0.8% by using deionized water to obtain TOCNF suspension. Further, TEMPO nanocellulose was prepar