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CN-121975456-A - Preparation method and application of nanocellulose-based silicon negative electrode binder

CN121975456ACN 121975456 ACN121975456 ACN 121975456ACN-121975456-A

Abstract

The invention discloses a preparation method and application of a nano-cellulose-based silicon negative electrode binder, which belong to the technical field of lithium ion batteries, wherein CMC powder and TOCNF suspension are uniformly mixed at room temperature and dispersed by ultrasonic to obtain the nano-cellulose-based silicon negative electrode binder, TEMPO nano-cellulose is used as one of binder components to assist a common CMC binder to maintain stable circulation performance of a silicon oxide negative electrode material, high length-diameter ratio rigidity TOCNF is introduced into a traditional CMC system, stable hydrogen bonds are formed between surface carboxyl groups and a silicon-based material, interfacial adhesion is enhanced, a three-dimensional supporting network is constructed, when the adhesive is used for a silicon-based lithium ion battery negative electrode plate material, the adhesive is cooperated with SBR to buffer stress, expansion and cracking of a plate are effectively inhibited, the circulation stability of a high-capacity silicon oxide battery is improved, and the nano-cellulose is nontoxic and harmless and biodegradable when the battery is recovered, thereby conforming to the green circulation concept and having great commercial application prospect.

Inventors

  • LI FENGHE
  • WANG HUIQING
  • YAO RISHENG
  • LI XIANG

Assignees

  • 安徽安生生物化工科技有限责任公司
  • 合肥工业大学

Dates

Publication Date
20260505
Application Date
20260202

Claims (10)

  1. 1. The preparation method of the nano-cellulose-based silicon negative electrode binder is characterized by comprising the following steps of: Adding CMC powder into TOCNF suspension, stirring and mixing uniformly to obtain nano cellulose base silicon negative electrode adhesive; The mass ratio of the CMC powder to TOCNF in TOCNF suspension is 6-10:2-6.
  2. 2. The preparation method of the nanocellulose-based silicon negative electrode 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 nanocellulose-based silicon negative electrode binder according to claim 1, wherein the TOCNF length-diameter ratio is 200-2000, the diameter is 1-20 nm, and the carboxyl content is 1.3-2.5 mmol/g.
  4. 4. The method for preparing a nanocellulose-based silicon negative electrode 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% -1.5% by using deionized water, homogenizing for 6-10 times by using 160-200 mpa pressure in a high-pressure homogenizer, stripping the cellulose oxidized by TEMPO into cellulose nanofibers, and regulating the cellulose nanofibers to TOCNF with deionized water to have the solid content of 0.2% -0.6%, so as to obtain TOCNF suspension.
  5. 5. The method for preparing the nano-cellulose-based silicon negative electrode binder according to claim 4, wherein the TEMPO oxidized cellulose is prepared by the steps of: adding TEMPO and NaBr into deionized water in sequence, stirring and dissolving at 15-25 ℃, adding crushed and dried cellulose fiber 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 4-6 h, centrifugally washing the product, washing the product with deionized water for 4-8 times, and drying to constant weight to obtain the cellulose oxidized by TEMPO.
  6. 6. The preparation method of the nanocellulose-based silicon negative electrode binder 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 materials and NaClO solution is 0.8g:5 g:4500-4800 mL:48-50 g:372-375g.
  7. 7. The application of the nano-cellulose-based silicon anode binder in the anode piece material of the silicon-based lithium ion battery is characterized in that the nano-cellulose-based silicon anode binder is prepared by the preparation method of the nano-cellulose-based silicon anode binder according to any one of claims 1-6.
  8. 8. The use according to claim 7, wherein the silicon-based lithium ion battery negative electrode sheet material is prepared by: The silicon-based lithium ion battery negative electrode plate material is prepared through the following steps: The preparation method comprises the steps of adding a nano-cellulose-based silicon negative electrode binder, a conductive agent and silicon oxide powder into a stirring kettle, stirring and dispersing for 5-8 hours at 700-900 rpm to obtain negative electrode slurry, coating the negative electrode slurry on a copper foil, carrying out vacuum preheating for 2-3 hours at 80-90 ℃, and carrying out vacuum drying for 12-14 hours at the vacuum degree of-0.1 MPa and the temperature of 80-90 ℃ to obtain the silicon-based lithium ion battery negative electrode plate material.
  9. 9. The use according to claim 8, wherein the mass ratio of the silicon oxide powder, the nanocellulose-based silicon negative electrode binder and the conductive agent is 90-95:2.5-5:2.5-5.
  10. 10. The use according to claim 7, wherein the silicon-based lithium ion battery negative electrode sheet material is prepared by: Adding a nano cellulose-based silicon negative electrode binder, a conductive agent and silicon oxide powder into a stirring kettle, stirring and dispersing for 5-8 hours at 700-900 rpm, adding SBR, stirring for 0.5-1 hour at 500-600 rpm to obtain negative electrode slurry, coating the negative electrode slurry on a current collector, vacuum-preheating for 2-3 hours at 80-90 ℃, and vacuum-drying for 12-14 hours at the vacuum degree of-0.1 MPa and the temperature of 80-90 ℃ to obtain a silicon-based lithium ion battery negative electrode plate material; the mass ratio of the silicon oxide powder to the nano-cellulose-based silicon negative electrode binder to the SBR to the conductive agent is 90-94:2-3.4:2-3.3:2-3.3.

Description

Preparation method and application of nanocellulose-based silicon negative electrode binder Technical Field The invention belongs to the technical field of lithium ion batteries, and particularly relates to a preparation method and application of a nanocellulose-based silicon negative electrode binder. Background Lithium Ion Batteries (LIBs) have become the most popular energy storage devices to power consumer electronics and electric automobiles today, however, conventional graphite anode lithium batteries are limited by the upper limit of energy density and cannot meet market demands in terms of battery capacity. SiOx is considered as the next-generation negative electrode material of a high-energy lithium ion battery because it has a higher theoretical capacity (950 mah·g -1), a smaller volume change than that of elemental Si, a suitable oxidation-reduction potential, a rich reserve, and a low cost. However, during the charge and discharge process of the battery, as the lithium removal reaction and the lithium intercalation reaction proceed, the silicon-based material undergoes huge volume expansion, so that the active material is separated from the conductive network, the surface SEI film is continuously broken and regenerated, the capacity attenuation and the coulombic efficiency are reduced, and in the silicon negative electrode, the adhesive has strong viscoelasticity and structural strength, which can cause the silicon particles to separate from the conductive network, thereby affecting the performance of the battery. SiOx950 anode lithium batteries also face silicon-like anode bottlenecks in suppressing anode volume expansion and extending their service life, which hinders their commercial implementation. In order to solve the limitations of the silicon-based electrode, an effective method is to develop an advanced functional binder, which plays an important role in uniformly dispersing active materials, and by bonding all materials with a current collector, not only separation and pulverization of the active materials can be reduced, but also formation of an unstable SEI film can be prevented, thereby enhancing contact of an electrode material with the current collector, and finally maintaining a high capacity and excellent cycle stability of the battery. It is therefore critical to solve this problem to find a suitable negative electrode binder. Disclosure of Invention The invention aims to provide a preparation method and application of a nano cellulose-based silicon negative electrode binder, which have good mechanical properties and a network crosslinking structure, and effectively inhibit the volume expansion and rebound phenomena of a silicon negative electrode in the charging and discharging process and remarkably improve the stability of the silicon negative electrode in the long-cycle process through the hydroxyl hydrogen bond crosslinking action of the binder and the surface of silicon oxide. The aim of the invention can be achieved by the following technical scheme: a nano-cellulose-based silicon negative electrode binder is prepared by the following method: adding CMC powder into TOCNF suspension, stirring and mixing evenly to obtain the nano-cellulose-based silicon negative electrode binder. Further, the mass ratio of CMC powder to TOCNF in TOCNF suspension is 6-10:2-6. 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, TOCNF suspensions were prepared by the following steps: Preparing cellulose oxidized by TEMPO into slurry with the solid content of 0.8% -1.5% by using deionized water, homogenizing for 6-10 times by using 160-200 mpa pressure in a high-pressure homogenizer, stripping the cellulose oxidized by TEMPO into cellulose nanofibers, and regulating the cellulose nanofibers to TOCNF with deionized water to have the solid content of 0.2% -0.6%, so as to obtain TOCNF suspension. Further, TEMPO oxidized cellulose was 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 fiber 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 4-6 h, centrifugally washing the product, washing the product with deionized water for 4-8 times, and drying to constant weight to obtain the cellulose oxidized by TEMPO. Further, the cellulose sources include, but are not limited to, cotton sources (refined linters, long linters, combed cotton), wood sources (softwood pulp board, hardwood pulp board, bamboo pulp board), at least