CN117334828A - Self-supporting thick electrode without current collector based on conductive nanocellulose, preparation method and application thereof - Google Patents

Self-supporting thick electrode without current collector based on conductive nanocellulose, preparation method and application thereof Download PDF

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CN117334828A
CN117334828A CN202311342473.5A CN202311342473A CN117334828A CN 117334828 A CN117334828 A CN 117334828A CN 202311342473 A CN202311342473 A CN 202311342473A CN 117334828 A CN117334828 A CN 117334828A
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nanocellulose
electrode
conductive
current collector
self
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汪朝晖
解思达
陈宁昕
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Hunan University
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/36—Accumulators not provided for in groups H01M10/05-H01M10/34
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/043—Processes of manufacture in general involving compressing or compaction
    • H01M4/0433—Molding
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0471—Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/022—Electrodes made of one single microscopic fiber
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes

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  • Chemical Kinetics & Catalysis (AREA)
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  • Battery Electrode And Active Subsutance (AREA)

Abstract

The invention discloses a self-supporting thick electrode without current collector based on conductive nanocellulose, a preparation method and application thereof, and belongs to the technical field of battery electrode materials. The electrode of the invention takes the battery active material as an active substance, the conductive polymer composite nanocellulose as a dispersing agent, a conductive agent and a film forming medium, and the flexible self-supporting secondary battery thick electrode without adhesive and current collector with good mechanical property, high conductivity and high environmental protection is obtained through the steps of ultrasonic treatment, stirring, vacuum suction filtration, drying, solvent post-treatment and compaction. The invention is simple and easy to implement, is easy for large-scale production, has wide sources, is green and safe, does not pollute the environment, and can greatly improve the ion transmission rate of the battery and enhance the cycle stability due to the unique high conductivity and excellent mechanical property.

Description

Self-supporting thick electrode without current collector based on conductive nanocellulose, preparation method and application thereof
Technical Field
The invention relates to the technical field of battery electrode materials, in particular to a self-supporting thick electrode without current collector based on conductive nanocellulose, a preparation method and application thereof.
Background
Lithium ion batteries, which are the most widely used secondary rechargeable batteries today, have the advantages of high theoretical energy density, long cycle life, no memory effect, etc., and are fully applied to personal portable devices. However, with the great development of portable devices and the continuous improvement of the national environmental protection standards, the electrode materials of secondary batteries are urgently required to be further developed, so that the secondary batteries are safe, stable, environment-friendly, reliable, higher in energy density, higher in power density and longer in cycle life. In order to meet the above requirements, more intensive studies on the secondary battery electrode are necessary.
The nanocellulose serving as a natural polymer fiber material with the widest distribution and the highest content in the nature has excellent mechanical property, dispersibility and papermaking film forming characteristics, has great application potential in the field of batteries, and is used for preparing cellulose paper-based electrode materials. However, the nano-cellulose material is intrinsically electrically insulated, and can only be compounded with conductive carbon nanotubes, conductive carbon black and the like to construct a conductive nano-fiber network, so that the nano-cellulose material is used for loading electrode materials. The paper-based electrode material based on the nanocellulose/conductive additive is uneven in distribution and difficult to continue, so that the electron transmission of an electrode is blocked, and the paper-based electrode material can only be used under the conditions of low active material loading and low active material content. This patent is from electrically conductive nanocellulose, namely: endowing the intrinsic electric insulating nano cellulose with electronic conductive characteristics to form a continuous and uniform three-dimensional conductive nano fiber network. In particular, the conductive polymer (PPy, PANI, PEDOT, etc.) can be uniformly coated on the functionalized nanocellulose, such as carboxylated cellulose, to form the conductive nanocellulose, and meanwhile, the intrinsic dispersibility, mechanical property and film forming property of the nanocellulose are reserved. The electrode system is applied to a secondary battery, active material particles are loaded on a conductive nanofiber network through a simple suction filtration film forming process, and a paper-based electrode with controllable thickness is formed. Therefore, on one hand, the active material can be uniformly dispersed, on the other hand, the defect of poor conductive performance of the active material and cellulose can be overcome, the electron transmission performance with an external circuit is enhanced, and when the content of the active material exceeds 90wt%, the high structural stability and the high electron transmission characteristic are kept. In addition, we also utilized solvent post-treatment to increase the conductivity of the conductive fibers, combined with compaction step to increase their volumetric capacity and energy density, further optimizing the electrochemical performance of the secondary battery.
Disclosure of Invention
In view of the above-mentioned shortcomings existing at present, the invention provides a self-supporting, current collector-free thick electrode of a secondary battery based on conductive nanocellulose, a preparation method and application thereof. The electrode of the present invention does not use conventional PVDF as a binder, that is, the electrode is a binder-free electrode, and the electrode has a characteristic of self-supporting without a conventional metal current collector. The electrode structure of the invention has a gradient structure, one surface is an active material-rich surface, the active material-rich surface contacts electrolyte for rapid intercalation/deintercalation of lithium ions, the other surface is a conductive fiber-rich surface (realized by vacuum filtration) with good conductivity, the contact current collector is favorable for rapid transmission of electrons, the three-dimensional conductive network is in a gradient distribution state as a whole, the problem of low electronic/ionic conductivity of the active material is comprehensively solved, and thus the battery performance is comprehensively improved, and the battery performance is improved in the aspects of cycle life, cycle stability, multiplying power performance, energy density and the like.
In order to achieve the above purpose, the invention provides a self-supporting, current collector-free thick electrode of a secondary battery based on conductive nanocellulose, wherein the electrode is a paper-based electrode, and the paper-based electrode comprises the conductive nanocellulose and an active substance; one surface of the paper-based electrode is enriched with conductive nanocellulose, and the other surface of the paper-based electrode is enriched with active substances; the gradient of the conductive nanocellulose from the surface enriched with the conductive nanocellulose to the surface enriched with the active substance decreases, and the gradient of the active substance from the surface enriched with the conductive nanocellulose to the surface enriched with the active substance increases; wherein, the conductive nanocellulose specifically comprises: the conductive polymer coats the functionalized nanocellulose.
According to one aspect of the invention, the conductive polymer comprises any one or more of PPy, PANI, PEDOT; the active substance comprises any one or more of lithium iron phosphate, active carbon, lithium manganate and graphite.
According to one aspect of the invention, the functionalized nanocellulose includes either or both of carboxylated nanocellulose, sulfonated nanocellulose.
According to one aspect of the invention, the porosity of the paper-based electrode is 20-70%, the mass ratio of the conductive nanocellulose in the paper-based electrode is 5-12%, and the mass ratio of the active substance in the paper-based electrode is 88-95%; the stress of the paper-based electrode is 1-20 MPa, and the strain is 1-10%.
Based on the same inventive concept, the invention also provides a preparation method of the self-supporting non-current collector secondary battery thick electrode based on the conductive nanocellulose, which comprises the following steps:
step 1: preparing functionalized nanocellulose into suspension, adding a certain amount of conductive polymer solution, and carrying out ultrasonic oscillation to obtain conductive nanocellulose suspension;
step 2: adding a certain amount of active substances into the conductive nanocellulose suspension, uniformly mixing by magnetic stirring, and then carrying out vacuum suction filtration and drying to obtain the conductive nanocellulose paper-based thick electrode material;
step 3: soaking the conductive nano cellulose paper-based thick electrode material in a certain volume of solvent for treatment, heating, taking out and then annealing to obtain the electrode material subjected to solvent post-treatment;
the annealing treatment was performed to remove the excess solvent.
It should be noted that the conductive fiber network after the solvent treatment has a delamination phenomenon.
Step 4: and compacting the electrode material subjected to solvent post-treatment by a tablet press to obtain the self-supporting thick electrode without current collector based on the conductive nanocellulose.
According to one aspect of the invention, in step 1, the concentration of suspended matter in the suspension is 2-20 mg/mL, and the concentration of suspended matter in the conductive nanocellulose suspension is 4-40 mg/mL; the power of the ultrasonic oscillation is 100-500W, and the time of the oscillation is 10-60 min.
According to one aspect of the invention, in the step 2, the rotation speed of the magnetic stirring is 100-2000 rpm, and the time of the magnetic stirring is 1-4 hours; the drying temperature is 40-90 ℃, and the drying time is 2-12 h; the vacuum degree of the vacuum suction filtration is 0.01-0.098 MPa, and the time is 0.5-24 h.
According to one aspect of the present invention, in step 3, the treating solvent is a polar solvent; the temperature of the heating treatment is 80-140 ℃, and the time of the heating treatment is 1-5 h; the annealing treatment temperature is 90-150 ℃, and the annealing time is 0.5-6 h. Preferably, the polar solvent is any one or two of ethylene glycol and dimethyl sulfoxide.
In accordance with one aspect of the present invention, in step 4, the compacting pressure is 5 to 60MPa and the compacting time is 1 to 15min; the thickness before compaction is 20-900 mu m, and the loading capacity is 1-105 mg/cm 2 The thickness after compaction is 10-600 μm.
Based on the same inventive concept, the invention also provides an application of the self-supporting non-current collector secondary battery thick electrode based on the conductive nanocellulose or the preparation method of the self-supporting non-current collector secondary battery thick electrode based on the conductive nanocellulose prepared by the preparation method in the positive electrode materials of lithium ion batteries and zinc ion batteries.
The invention has the beneficial effects that:
the self-supporting secondary battery electrode realizes the effects of no binder and no current collector through the dispersibility of the nanocellulose and the unique self-gradient structure of the electrode. The charged groups of the conductive polymer and the functional groups (such as hydroxyl, carboxyl and the like) of the functionalized cellulose have strong electrostatic and hydrogen bond interaction, so that the conductive polymer can coat the nano cellulose to form high-conductivity nano fibers, and a three-dimensional conductive nano fiber network is further constructed. And then mixing and stirring the three-dimensional conductive nanofiber solution and electrode active substances, and performing vacuum suction filtration to prepare the self-supporting electrode without the binder. The invention skillfully utilizes the settleability of the active substance in the solution, and the concentration, the vacuum degree and other factors are regulated, so that the concentration of the active substance in the prepared electrode is in gradient distribution, and the electrode surface containing the relatively high conductive nanocellulose layer can be regarded as a conductive current collector layer, thus the electrode does not need a conventional current collector, the overall electrode quality can be lightened, and the light-weight characteristic is presented. Meanwhile, the self-gradient distribution electrode with the active material loading and the conductive network content has the effects of reducing electrode polarization and optimizing electron and ion transmission capacity, and can improve the rate capability and the cycle performance of an electrode material.
The patent starts from the thought of constructing a paper electrode by using the high-conductivity nanocellulose, endows the nanocellulose with intrinsic electric insulation and electronic conductivity, and simultaneously keeps the intrinsic dispersibility, mechanical property and film forming property of the nanocellulose. The conductive nanocellulose network is used for replacing a paper electrode preparation method based on a conductive carbon additive/nanocellulose, so that the continuity and conductivity of the conductive fiber network are improved essentially, and the conductive nanocellulose network can be used for constructing a thick electrode with high loading and high active substance content, and is favorable for improving the energy density of a battery by retaining excellent electron and ion transmission paths.
In addition, the conductivity of the conductive nanocellulose can be optimized through simple post-soaking treatment of a polar solvent, the treatment can effectively regulate and control the phase structure of the conductive polymer coating through the interaction between the polar group of the polar solvent and the conductive polymer chain (for example, the phase separation of the PEDOT and the PSS can be increased by using the DMSO polar solvent to treat the conductive polymer PEDOT: PSS, so that the PEDOT is converted from a benzene state to a quinoline state, the crystallinity of the PEDOT is improved, and the conductivity of the PEDOT is improved), and the conductivity of the conductive nanocellulose material is improved, and the conductivity of a thick electrode is further improved; likewise, the electrodes produced by this method can also be increased in their volumetric capacity and volumetric energy density in a battery system by a simple compaction step without adversely affecting their mechanical integrity and electrochemical performance.
Drawings
FIG. 1 shows 20mg/cm of the extract obtained in example 1 of the present invention 2 The thick electrode and the Li metal negative electrode are matched and assembled into a combined image of the cycle performance, the optical photograph of the bending test and the surface scanning electron microscope image of the lithium battery;
FIG. 2 shows 20mg/cm of the extract obtained in example 1 of the present invention 2 The thick electrode and the Li metal negative electrode are assembled into the multiplying power performance of the lithium battery in a matching way;
FIG. 3 shows 20mg/cm of the extract obtained in example 1 of the present invention 2 The thick electrode and the Li metal negative electrode are assembled into an electrochemical impedance diagram of the lithium battery in a matching way;
FIG. 4 shows 105mg/cm of the extract obtained in example 2 of the present invention 2 The thick electrode and the Li metal negative electrode are matched and assembled into the lithium battery with the thickness of 0.5mA cm -2 A charge-discharge curve graph at current density;
FIG. 5 shows 20mg/cm of the extract obtained in example 3 of the present invention 2 A combined graph of a cross-section scanning electron microscope graph and the cycle performance of the water-based zinc ion battery assembled by matching the thick electrode and the Zn metal negative electrode;
fig. 6 is a graph showing the comparison of the rate performance of lithium batteries assembled by matching the positive electrode material of the paper-based electrode obtained in example 1 and comparative example 1 with the negative electrode of Li metal;
fig. 7 is a graph showing the comparison of the rate performance of lithium batteries assembled by matching the positive electrode materials of the paper-based electrodes obtained in example 1 and comparative example 2 with the negative electrode of Li metal;
FIG. 8 is a graph showing the cycle performance of lithium batteries assembled by matching the paper-based electrode positive electrode materials prepared in example 1, comparative example 1 and comparative example 2 with Li metal negative electrodes;
Detailed Description
In order that the invention may be more readily understood, the invention will be further described with reference to the following examples. It should be understood that these examples are intended to illustrate the invention and not to limit the scope of the invention, and that the described embodiments are merely some, but not all, of the embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention. Unless defined otherwise, the terms of art used hereinafter are consistent with the meanings understood by those skilled in the art; unless otherwise indicated, all the materials and reagents referred to herein are commercially available or may be prepared by well-known methods.
Example 1
Preparation of conductive nanocellulose: taking 35.5mg of TEMPO oxidized carboxylated nanocellulose, adding a proper amount of deionized water, performing ultrasonic dispersion for 15 minutes, adding 50mg of conductive polymer PEDOT: PSS (conductive polymer solution), and performing ultrasonic dispersion for 20 minutes to obtain self-assembled conductive nanocellulose suspension.
Preparation of conductive nanocellulose paper-based thick electrode: adding 770mg of lithium iron phosphate powder into the conductive nanocellulose suspension, and stirring for 3 hours; setting up a vacuum filtration device, carrying out suction filtration to form a film, drying and heating in an oven after completion, and peeling to obtain a flexible self-supporting lithium iron phosphate electrode, wherein the thickness of the flexible self-supporting lithium iron phosphate electrode is about 120 mu m, and the mass load of the lithium iron phosphate is about 20mg/cm 2 。
Dimethyl sulfoxide post-treatment of conductive nanocellulose paper-based thick electrode: the electrode material is firstly fully soaked in dimethyl sulfoxide solution, then the electrode material is heated for 15 minutes at 100 ℃, and is annealed for 15 minutes at 130 ℃ after being taken out, so that the electrode material treated by dimethyl sulfoxide is obtained, and the thickness of the electrode material is almost unchanged.
Compacting the conductive nanocellulose paper-based thick electrode: and (3) carrying out static pressure on the electrode slice subjected to dimethyl sulfoxide treatment for 1 minute by using a tablet press at a pressure of 20MPa, and then taking out to finally obtain the electrode slice subjected to dimethyl sulfoxide treatment and compaction, wherein the thickness variation range of the electrode slice is within a range of 5-60%.
Example 2
Preparation of conductive nanocellulose: (1) 224.5mg of TEMPO oxidized carboxylated nanocellulose is measured, a proper amount of deionized water is added, ultrasonic dispersion is carried out for 15 minutes, and 310mg of conductive polymer PPy PSS is added, ultrasonic dispersion is carried out for 20 minutes, thus obtaining self-assembled conductive nanocellulose suspension.
Preparation of conductive nanocellulose paper-based thick electrode: adding into the conductive nanocellulose suspension4040.9mg of lithium iron phosphate powder, stirred for 3 hours; setting up a vacuum suction filtration device for suction filtration to form a film, drying and heating in an oven after the film is completed, and obtaining a self-supporting lithium iron phosphate anode after peeling, wherein the carrying capacity is about 105mg/cm 2 The thickness is about 700um.
Glycol post-treatment of conductive nanocellulose paper-based thick electrode: the electrode material is completely soaked in the glycol solution, then the electrode material is heated for 15 minutes at 100 ℃, taken out and annealed for 15 minutes at 130 ℃ to obtain the glycol-treated electrode material, and the thickness of the glycol-treated electrode material is almost unchanged.
Compacting the conductive nanocellulose paper-based thick electrode: and (3) carrying out static pressure on the electrode slice subjected to the ethylene glycol treatment for 5 minutes by using a tablet press under the pressure of 10MPa, and then taking out to finally obtain the electrode slice subjected to the ethylene glycol treatment and compaction, wherein the thickness variation range of the electrode slice is between 5% and 60%.
Example 3
Preparation of conductive nanocellulose: (1) 38.5mg of TEMPO oxidized carboxylated nanocellulose is measured, a proper amount of deionized water is added, ultrasonic dispersion is carried out for 15 minutes, 50mg of conductive polymer PEDOT: PSS is added, ultrasonic dispersion is carried out for 20 minutes, and self-assembled conductive nanocellulose suspension is obtained.
Preparation of conductive nanocellulose paper-based thick electrode: weighing 38.5mg of TEMPO oxidized carboxylated nanocellulose, adding a proper amount of deionized water, performing ultrasonic dispersion for 15 minutes, adding 54mg of conductive polymer PEDOT (PSS), performing ultrasonic dispersion for 20 minutes, finally adding 770mg of active carbon powder, and stirring for 3 hours; setting up a vacuum suction filtration device for suction filtration to form a film, drying and heating in an oven after completion, and peeling to obtain a flexible self-supporting active carbon electrode, wherein the thickness of the active carbon electrode is about 650 mu m, and the mass load of the active carbon is about 20mg/cm 2 。
Dimethyl sulfoxide post-treatment of conductive nanocellulose paper-based thick electrode: the electrode material is firstly fully soaked in dimethyl sulfoxide solution, then the electrode material is heated for 15 minutes at 100 ℃, and is annealed for 15 minutes at 130 ℃ after being taken out, so that the electrode material treated by dimethyl sulfoxide is obtained, and the thickness of the electrode material is almost unchanged.
Compacting the conductive nanocellulose paper-based thick electrode: and (3) carrying out static pressure on the electrode slice subjected to dimethyl sulfoxide treatment for 5 minutes by using a tablet press at a pressure of 40MPa, and then taking out to finally obtain the electrode slice subjected to dimethyl sulfoxide treatment and compaction, wherein the thickness variation range of the electrode slice is within a range of 5-80%.
Comparative example 1
The difference between this comparative example and example 1 is: the concentration of active material was varied, and the active material concentration of the example was about 26mg/mL, while the active material concentration of the comparative example was about 52mg/mL (2 times that of example 1), other steps and parameters were the same as in example 1.
Comparative example 2
The difference between this comparative example and example 1 is: the solvent post-treatment of the conductive nanocellulose paper-based thick electrode was not performed, other steps and parameters were the same as in example 1.
Performance inspection and result analysis
The electrode sheets obtained in examples 1-3 and comparative examples 1-2 were applied to lithium ion batteries and zinc ion battery systems, cycle life, rate performance, electrochemical impedance tests of the batteries were performed, and microscopic scale characterization was performed on the electrode materials and the positive electrode of the batteries after the cycling using a scanning electron microscope. The paper-based electrode positive electrode materials obtained in examples 1 and 2 and comparative examples 1 and 2 were assembled with a Li metal negative electrode in a matching manner and applied to lithium batteries, and electrochemical performance was tested using a commercial lithium hexafluorophosphate electrolyte. The paper-based electrode positive electrode material obtained in example 3 is assembled with a Zn metal negative electrode in a matching way and applied to a water-based zinc ion battery, and electrochemical performance is tested by adopting commercial zinc sulfate electrolyte.
As can be seen from FIG. 1, the electrode of example 1 exhibited better cycle performance, and its specific capacity was substantially maintained at 160mAh g after 60 cycles -1 Is unchanged. In addition, the plastic has good bending performance, shows better flexibility and can still maintain the original state after being bent for approximately 180 degrees. Meanwhile, the scanning electron microscope in the figure shows that the two surfaces of the electrode show different morphologies, one surface is mainly a lithium iron phosphate-rich surface, the surface is contacted with electrolyte to facilitate the extraction/intercalation of lithium ions, the other surface is mainly a conductive fiber-rich surface with good conductivity to contact a collector to facilitate the current collectionIn the rapid transmission of electrons, the three-dimensional conductive nanofiber network is in a gradient distribution state, so that the problem of low conductivity of lithium iron phosphate electrons/ions can be comprehensively solved.
As can be seen from the rate capability of FIG. 2, the current density of the electrode cell of example 1 was from 0.5mA cm -2 Gradually increase to 1, 2, 5 and 10mA cm -2 Finally, the temperature is reduced to 0.5mA cm -2 The discharge specific capacities of the last cycle at each multiplying power are 164.3, 160.2, 151.8, 124.7, 52.9 and 165.2mAh g in sequence -1 The cycle stability is good under the low current density, and the specific capacity of the lithium ion battery is reduced within the expected range under the high current density, so that the lithium ion battery shows good multiplying power performance, and the lithium ion battery has relatively small electrochemical impedance and comprehensively shows excellent ion transmission performance in combination with fig. 3.
For 105mg cm -2 As can be seen from fig. 4, the charge-discharge curve of the fifth cycle shows good charge-discharge plateau and specific capacity performance, indicating that the electrode of example 2 still has excellent electrochemical performance at high load.
The cycling performance and cross-sectional scanning electron microscopy of the activated carbon electrode of example 3 is shown in FIG. 5, which shows the electrode at 0.5mA cm -2 The initial discharge specific capacity under the current density is 187.1mAh g -1 The specific discharge capacity after 35 cycles is kept at 125.3mAh g -1 The capacity retention was 70%. The cross-sectional thickness in the combined figures is 413um, and the electrode still maintains good cycling performance at higher thicknesses and higher loadings. Meanwhile, the method disclosed by the patent is applied to different active substances and different battery systems, and has good electrochemical performance and excellent compatibility and migration.
As can be seen from comparison of example 1 and comparative example 1 (FIG. 6), the electrode sheet prepared in comparative example 1 has a significantly lower specific capacity during the first cycle, which indicates that the self-gradient-free structure caused by increasing the concentration of the active material can seriously affect the deintercalation of lithium ions, and the conductive fiber with too much near electrolyte end of the electrode can not well increase the transmission rate of lithium ions under the condition of high multiplying powerIt is more evident at 5mA cm -2 The specific capacity is only 53mAh g under the current density -1 Even less than half of the self-gradient electrode. As can be seen from fig. 8, the cycling performance of the self-gradient electrode (example 1) was more excellent than that of the non-self-gradient electrode (comparative example 1).
Comparing the remainder of example 1 with comparative example 2 (FIG. 7), the rate performance and cycle performance of the self-gradient electrode after DMSO and compaction treatment were significantly improved over the solvent-free treated electrode. The method is largely related to the fact that after PSS is treated by DMSO, part of PSS is removed, the segment structure of the PEDOT is changed, the benzene state is changed into the quinoline state, the crystallinity of the PEDOT is greatly improved, and the conductivity of the PEDOT is further enhanced. The conductivity of the conductive fiber is improved, so that on one hand, the electron conductivity of the electrode and an external circuit can be improved, and on the other hand, the extraction and intercalation of lithium ions in active substances in the electrode can be accelerated, and the lithium ion transmission rate can be improved.
The foregoing is merely illustrative of the present invention, and the present invention is not limited thereto, and any changes or substitutions easily contemplated by those skilled in the art within the technical scope of the present invention should be included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims (10)

1. The self-supporting thick electrode of the secondary battery without the current collector based on the conductive nanocellulose is characterized in that the electrode is a paper-based electrode, and the paper-based electrode comprises the conductive nanocellulose and an active substance; one surface of the paper-based electrode is enriched with conductive nanocellulose, and the other surface of the paper-based electrode is enriched with active substances; the gradient of the conductive nanocellulose from the surface enriched with the conductive nanocellulose to the surface enriched with the active substance decreases, and the gradient of the active substance from the surface enriched with the conductive nanocellulose to the surface enriched with the active substance increases; wherein, the conductive nanocellulose specifically comprises: the conductive polymer coats the functionalized nanocellulose.
2. The conductive nanocellulose-based self-supporting, current collector-free secondary battery thick electrode of claim 1, wherein said conductive polymer comprises any one or more of PPy, PANI, PEDOT; the active substance comprises any one or more of lithium iron phosphate, active carbon, lithium manganate and graphite.
3. The conductive nanocellulose-based self-supporting, current collector-free secondary battery thick electrode of claim 1, wherein said functionalized nanocellulose comprises either one or both of carboxylated nanocellulose, sulfonated nanocellulose.
4. The self-supporting, current collector-free secondary battery thick electrode based on conductive nanocellulose as claimed in claim 1 wherein the porosity of the paper-based electrode is 20-70%, the mass ratio of conductive nanocellulose in the paper-based electrode is 5-12%, and the mass ratio of active substance in the paper-based electrode is 88-95%; the stress of the paper-based electrode is 1-20 MPa, and the strain is 1-10%.
5. The method for preparing a thick electrode for a self-supporting, current collector-free secondary battery based on conductive nanocellulose as claimed in any one of claims 1 to 4, comprising the steps of:
step 1: preparing functionalized nanocellulose into suspension, adding a certain amount of conductive polymer solution, and carrying out ultrasonic oscillation to obtain conductive nanocellulose suspension;
step 2: adding a certain amount of active substances into the conductive nanocellulose suspension, uniformly mixing by magnetic stirring, and then carrying out vacuum suction filtration and drying to obtain the conductive nanocellulose paper-based thick electrode material;
step 3: soaking the conductive nano cellulose paper-based thick electrode material in a certain volume of solvent for treatment, heating, taking out and then annealing to obtain the electrode material subjected to solvent post-treatment;
step 4: and compacting the electrode material subjected to solvent post-treatment by a tablet press to obtain the self-supporting thick electrode without current collector based on the conductive nanocellulose.
6. The conductive nanocellulose based self-supporting, current collector-free secondary battery thick electrode of claim 5, wherein in step 1, the concentration of suspended matter in said suspension is 2-20 mg/mL, and the concentration of suspended matter in said conductive nanocellulose suspension is 4-40 mg/mL; the power of the ultrasonic oscillation is 100-500W, and the time of the oscillation is 10-60 min.
7. The method for preparing a thick electrode of a self-supporting, current collector-free secondary battery based on conductive nanocellulose as claimed in claim 5, wherein in step 2, the rotation speed of the magnetic stirring is 100-2000 rpm, and the time of the magnetic stirring is 1-4 hours; the drying temperature is 40-90 ℃, and the drying time is 2-12 h; the vacuum degree of the vacuum suction filtration is 0.01-0.098 MPa, and the time is 0.5-24 h.
8. The method for preparing a thick electrode for a secondary battery based on conductive nanocellulose as claimed in claim 5, wherein in step 3, said treating solvent is a polar solvent; the temperature of the heating treatment is 80-140 ℃, and the time of the heating treatment is 1-5 h; the annealing treatment temperature is 90-150 ℃, and the annealing time is 0.5-6 h.
9. The method for preparing a thick electrode of a secondary battery based on conductive nanocellulose and free of current collector as claimed in claim 5, wherein in step 4, the compacting pressure is 5-60 MPa and the compacting time is 1-15 min; the thickness before compaction is 20-900 mu m, and the loading capacity is 1-105 mg/cm 2 The thickness after compaction is 10-600 μm.
10. Use of the self-supporting, current collector-free thick electrode of a secondary battery based on conductive nanocellulose according to any one of claims 1-4 or the self-supporting, current collector-free thick electrode of a secondary battery based on conductive nanocellulose prepared by the preparation method according to any one of claims 5-9 in a positive electrode material of a lithium ion battery or a zinc ion battery.
CN202311342473.5A 2023-10-17 2023-10-17 Self-supporting thick electrode without current collector based on conductive nanocellulose, preparation method and application thereof Pending CN117334828A (en)

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