CN111740075A - Flexible electrodes and flexible batteries based on carbonized silk fabrics - Google Patents

Abstract

The present invention provides a flexible electrode based on carbonized silk fabric, comprising carbonized silk fabric and an electrode active material compounded with the carbonized silk fabric. The flexible electrodes of the present invention are especially flexible lithium negative electrodes and flexible sulfur positive electrodes. The present invention also provides a flexible battery comprising the flexible electrode, especially a flexible lithium-sulfur battery. The flexible electrode and flexible battery of the invention have the following advantages: the carbonized silk fabric has a wide source of raw materials, the preparation process is simple, green and environmentally friendly, and the cost is low; the carbonized silk fabric has a three-dimensional spatial structure, good flexibility and conductivity, and there are abundant nitrogen oxides The doping structure has better affinity for polysulfides and metal lithium, which can inhibit the growth of lithium dendrites, inhibit the "shuttle effect" of polysulfides in lithium-sulfur batteries, and improve the cycle stability of the battery; The surface quality of carbonized silk fabric is lighter, which is beneficial to improve the energy density of the battery.

Description

Flexible electrodes and flexible batteries based on carbonized silk fabrics

technical field

The invention belongs to the technical field of batteries, in particular to a flexible electrode and a flexible battery based on carbonized silk fabrics, and more particularly to a flexible electrode comprising carbonized silk fabrics, especially a flexible lithium negative electrode and a flexible sulfur positive electrode, and a flexible electrode comprising the carbonized silk fabric Flexible batteries with flexible electrodes, especially flexible lithium-sulfur batteries.

Background technique

In recent years, with the rapid development and emerging applications of flexible wearable electronic products such as scroll-type displays, electronic textiles, soft robots, Internet of Things systems, and bioelectronic products, there is an urgent need to develop a thin, flexible, flexible, high-energy density The battery with stable performance provides power for various wearable and flexible electronic devices. At present, rigid lithium-ion batteries that use metal foils as current collectors will suffer fatigue fracture and active material peeling when they are repeatedly bent, which is easy to cause electrochemical and mechanical performance degradation. It is not high and needs to use thicker electrodes, so it is difficult to achieve the excellent flexibility and high energy density of lithium batteries.

Lithium-sulfur battery, as the next generation of lithium battery technology, uses sulfur and metal lithium as the positive and negative electrode materials of the battery, and has the theoretical advantage of extremely high specific capacity (lithium: 3860mAh/kg; sulfur: 1675mAh/kg). The application of wearable and flexible electronic device products has attracted extensive attention at home and abroad. However, the application of lithium-sulfur batteries still faces many challenges. On the negative electrode side, the huge volume change and lithium dendrite growth during the charging and discharging process of lithium metal can easily lead to the continuous destruction of the SEI film on the negative electrode surface and the continuous consumption of electrolyte; Polysulfides (such as Li ₂ S ₄ , Li ₂ S ₆ , Li ₂ S ₈ , etc.), which can dissolve in the electrolyte and pass through the battery separator, resulting in continuous loss of active sulfur during cycling and electrolyte consumption . It can be seen that the above factors will lead to the unstable electrochemical performance of lithium-sulfur batteries.

Replacing metal foils with high-specific-area flexible conductive substrates as current collectors is an important way to improve the electrochemical performance and mechanical flexibility of lithium-sulfur batteries. At present, there are mainly two types of flexible current collector substrates for lithium-sulfur electrodes, one is carbon nanotubes, graphene, and cellulose carbon paper, and the other is carbon fabrics. Carbon paper has the characteristics of light weight and high conductivity. Lithium-sulfur active materials can be directly deposited on thin-film carbon paper to prepare flexible electrodes, and then light and flexible lithium-sulfur batteries can be assembled. However, such flexible lithium-sulfur batteries generally have higher energy density. Low, poor bending stability. Carbon fabrics have the advantages of high flexibility, porous network structure and good chemical stability, and the lithium-sulfur electrodes prepared by using them have excellent mechanical flexibility. Research teams at home and abroad have tried to use vacuum filtration, liquid impregnation, electrodeposition, hot melting, etc. to load highly active lithium-sulfur substances on the surface of carbon fabrics to realize the preparation of flexible lithium-sulfur electrodes. However, commercial carbonized fabrics have high surface mass density and poor affinity for polysulfides and metallic lithium, which cannot effectively inhibit the shuttle effect of polysulfides and the growth of lithium dendrites, which often results in the failure of carbon fabrics for lithium-sulfur batteries. Electrochemical and mechanical stability is poor. Although a large number of previous works have improved the electrochemical and mechanical stability of carbonized fabric lithium-sulfur batteries through surface modification (such as heteroatom doping, metal sulfide modification, transition metal coating, etc.), most surface modification processes are cumbersome and complicated. and poor interface stability. Therefore, it is still challenging to realize high-performance flexible lithium-sulfur electrodes and full batteries using simple and effective methods.

SUMMARY OF THE INVENTION

The purpose of the present invention is to solve the above-mentioned technical problems existing in the existing carbonized fabric and carbonized fabric lithium-sulfur batteries, and achieve the above-mentioned purpose through the innovative technical scheme of the flexible electrode and flexible battery based on the carbonized silk fabric.

Specifically, in a first aspect, the present invention provides a flexible electrode comprising a carbonized silk fabric and an electrode active material compounded with the carbonized silk fabric.

Further, the carbonized silk fabric is prepared by the following method: under the protection of an inert gas, the silk fabric is dehydrated at a first temperature, pre-cyclized at a second temperature, and carbonized at a third temperature. treatment to obtain the carbonized silk fabric.

Further, under the protection of inert gas, the silk fabric is dehydrated at a first temperature between 100°C and 200°C for 1-2 hours, and then cyclized at a second temperature between 300°C and 400°C. Treated for 2-3h, then carbonized at a third temperature between 950℃-1100℃ for 1-2h, the heating rate of the silk fabric to the first temperature, the second temperature and the third temperature was independently 2℃- 10°C/min.

In one embodiment of the flexible electrode of the present invention, the electrode active material is a negative electrode active material, and the negative electrode active material is lithium metal, silicon, graphite or metal oxide. Preferably, the negative electrode active material is lithium metal, and the flexible electrode is a flexible lithium negative electrode.

Further, the flexible lithium negative electrode is prepared by the following method: cutting the carbonized silk fabric into a carbonized silk fabric pole piece of suitable size, matching with the lithium metal electrode, and assembling it into a half-cell; under the condition of constant current, the lithium Metal is quantitatively deposited on the carbonized silk fabric pole piece; then the carbonized silk fabric pole piece deposited with lithium metal is taken out, rinsed with an organic solvent, and dried to obtain the flexible lithium negative electrode.

Further, the current magnitude is in the range of 0.1-1 mA cm- ² , and the deposition amount of lithium metal is in the range of 1-20 mAh cm- ² .

In other embodiments of the flexible electrode of the present invention, the electrode active material is a positive electrode active material, the positive electrode active material comprises elemental sulfur, and the flexible electrode is a flexible sulfur positive electrode.

Further, the flexible electrode is prepared by the following method: mixing sulfur powder and conductive additive according to the mass ratio of (2-3): 1 and fully grinding, and carrying out the grinding process at 150-160° C. under the protection of inert gas The hydrothermal reaction is carried out for 12-16h to obtain a sulfur compound; the obtained sulfur compound and the binder are fully mixed in an appropriate amount of solvent according to the mass ratio of (8-9):1 to obtain a positive electrode slurry; then the obtained The positive electrode slurry is coated on the carbonized silk fabric, and vacuum-dried at 60° C.-80° C. for 12-16 hours to remove the solvent to obtain the flexible electrode, that is, a flexible sulfur positive electrode.

Further, the conductive additive is one or more of acetylene black, Ketjen black, Super P, Super C45, carbon nanotubes, and graphene, and the binder is a water-based binder or an organic solvent-based binder.

In still other embodiments of the flexible electrode of the present invention, the electrode active material is a positive electrode active material, and the positive electrode active material is a nickel-cobalt-manganese ternary material (NCM), lithium cobalt oxide (LCO), lithium iron phosphate (LFP) , one or more of nickel-cobalt-aluminum ternary material (NCA), lithium manganate (LMO), and lithium nickelate (LNO).

Further, the flexible electrode is prepared by the following method: the positive electrode active material, the conductive additive and the binder are uniformly mixed in an appropriate amount of solvent according to the mass ratio of (4-9):(1-2):1 to obtain a positive electrode slurry; then uniformly coat the obtained positive electrode slurry on the carbonized silk fabric, and vacuum dry at 60°C-80°C for 12-16 hours to remove the solvent to obtain the flexible electrode.

Further, the conductive additive is one or more of acetylene black, Ketjen black, Super P, Super C45, carbon nanotubes, and graphene, and the binder is a water-based binder or an organic solvent-based binder.

In another aspect, the present invention provides a flexible battery comprising an electrode, a separator and an electrolyte, the electrode comprising a positive electrode and a negative electrode, the separator being positioned between the positive electrode and the negative electrode, the electrode comprising the flexible electrode according to the first aspect of the present invention .

In some embodiments of the flexible battery of the present invention, the negative electrode is a flexible lithium negative electrode according to the first aspect of the present invention.

In other embodiments of the flexible battery of the present invention, the positive electrode is a flexible sulfur positive electrode according to the first aspect of the present invention.

In further embodiments of the flexible battery of the present invention, the negative electrode is a flexible lithium negative electrode according to the first aspect of the present invention, the positive electrode is a flexible sulfur positive electrode according to the first aspect of the present invention, and the flexible battery is a flexible lithium-sulfur battery.

Beneficial effects of the present invention:

In the present invention, carbonized silk fabrics derived from carbonization of silk fabrics are used as flexible carbon-based materials, and carbonized silk fabrics are applied to the preparation of flexible electrodes (including flexible positive electrodes and flexible negative electrodes) and flexible batteries for the first time, including preferred flexible lithium negative electrodes and flexible sulfur positive electrodes. , and the preferred flexible lithium-sulfur battery, with the following beneficial effects:

(1) The raw materials of carbonized silk fabrics are widely sourced, the preparation process is simple, green and environmentally friendly, and the cost is low.

(2) The carbonized silk fabric has a three-dimensional spatial structure, good flexibility and electrical conductivity, and has abundant nitrogen-oxygen doping structure. Compared with commercial carbonized fabrics, it has better affinity for polysulfides and metallic lithium. Therefore, when carbonized silk fabric is used for lithium anode, it can reduce the local current density, guide the uniform nucleation of lithium metal, and inhibit the growth of lithium dendrites; when used in sulfur cathode, it can buffer the stress caused by the change of sulfur volume during battery cycling and adsorb sulfur The polysulfides generated on the positive electrode inhibit the "shuttle effect" of lithium-sulfur batteries, thereby improving the battery's cycle stability.

(3) Compared with the commonly used commercial carbon cloth, the surface quality of carbonized silk fabric is lighter (the surface quality of commercial carbon cloth is usually 12.6 mg cm ^-2 , and the surface quality of carbonized silk fabric is 1.8-6.3 mg cm ^-2 ) , which is beneficial to improve the energy density of the battery.

(4) The flexible lithium negative electrode and the flexible sulfur positive electrode of the present invention exhibit good flexibility and cycle stability, and can be matched with each other or matched with other flexible electrodes to form a flexible battery, so as to improve the energy density and cycle performance of the flexible battery, and have good flexibility. application prospects.

Description of drawings

Figure 1 shows the SEM images of the carbonized silk cloth prepared in Examples 1 and 2 of the present invention, wherein (a) and (b) show the SEM images of the carbonized silk cloth prepared in Example 1, and (c) and (d) show The SEM image of the carbonized silk cloth obtained in Example 2;

Fig. 2 shows the XPS diagram of nitrogen element of the carbonized silk cloth obtained in Example 1 of the present invention;

Fig. 3 shows the XPS diagram of oxygen element of the carbonized silk cloth obtained in Example 1 of the present invention;

Fig. 4 shows the SEM image of the carbonized silk cloth prepared in Example 1 of the present invention after depositing 3mAh cm ^-2 lithium metal;

Fig. 5 shows the Coulomb efficiency diagram of the carbonized silk cloth obtained in Example 1 of the present invention;

Fig. 6 shows the cycle stability test result of the symmetrical battery assembled with the carbonized silk cloth composite lithium electrode prepared in Example 1 of the present invention;

Fig. 7 shows the SEM image of the sulfur positive electrode with carbonized silk cloth as the current collector in Example 1 of the present invention, wherein (a) is a front view, and (b) is a cross-sectional view;

FIG. 8 shows the cycle performance diagram of the lithium-sulfur battery assembled in Example 1 of the present invention;

Fig. 9 shows the cycle performance diagram of the lithium-sulfur battery using carbonized silk cloth as the current collector under higher load in Example 1 of the present invention;

Figure 10 shows the cycle performance diagram of the flexible soft-pack lithium-sulfur battery using carbonized silk cloth as the current collector in Example 1 of the present invention;

FIG. 11 shows the cycle performance diagram of the flexible soft-pack lithium-sulfur battery using carbonized silk cloth as the current collector in Example 1 of the present invention.

Detailed ways

In order to make the technical problems solved by the present invention, the technical solutions adopted and the beneficial effects obtained more clearly, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

A first aspect of the present invention provides a flexible electrode comprising a carbonized silk fabric and an electrode active material compounded with the carbonized silk fabric.

The invention innovatively uses the carbonized silk fabric as a base material to compound the electrode active material, and utilizes the flexibility and conductivity of the carbonized silk fabric to make a flexible electrode. It can be compounded with positive active materials to make flexible positive electrodes, and can also be combined with negative active materials to make flexible negative electrodes. The prepared flexible positive electrode or flexible positive electrode can be further used to fabricate a flexible battery. The term "composite" as used herein should be understood in a broad sense to include any means of electrically combining a carbonized silk fabric with an electrode active material. For example, the flexible lithium anodes described below are prepared by depositing lithium metal on carbonized silk fabrics, in which case the carbonized silk fabrics are composited with electrode active materials by deposition. For another example, the flexible sulfur positive electrode described below is prepared by preparing a positive electrode active material, a conductive additive and a binder into a positive electrode slurry, and then coating the positive electrode slurry on the carbonized silk fabric, in this case, by coating The carbonized silk fabric is compounded with the electrode active material by the coating method.

Silk is spit out by silkworms in the dormant period before becoming silkworm moths. According to the variety of silkworms, silks include mulberry silk, tussah silk, castor silk and cassava silk, etc. The commonly used ones are mulberry silk and tussah silk. Silk is a kind of natural protein fiber, which is composed of sericin in the outer layer and silk fibroin (fibroin) in the inner layer. The silk is small in diameter, smooth, shiny and elastic. It does not need to be spun when used in fabrics. It only requires two strands to be combined and then twisted to form a continuous rope-like filament. Elegant, comfortable and aesthetically pleasing, silk fabrics have been the material of high-end apparel for thousands of years. Because silk fabrics are rich in carbon elements, soft and thin, with the rise of flexible batteries and flexible wearable devices, silk fabrics have also attracted great interest as a raw material for flexible conductive materials.

The term "silk fabric" as used herein includes both common silk fabric cloths and regenerated silk fibroin fibers prepared by electrospinning. The term "carbonized silk fabric" as used herein refers to a flexible conductive material obtained by subjecting the silk fabric to high temperature heat treatment and the like.

Usually, the carbonized silk fabric is prepared by the following method: under the protection of an inert gas, the silk fabric is subjected to dehydration treatment at a first temperature, cyclization treatment at a second temperature, and carbonization treatment at a third temperature to obtain The carbonized silk fabric.

Without being limited by theory, it is believed that after the fibroin in silk fabrics is heated by gradient heating, intramolecular dehydration occurs between adjacent peptide chains, followed by aromatization or cyclization to form hexagonal carbocyclic rings, and finally even highly ordered graphite structure.

It can be understood that the first temperature is the temperature suitable for dehydrating the silk fabric, the second temperature is the temperature at which the amino and carboxyl groups in the protein in the silk fabric undergo cyclization reaction to form a nitrogen-oxygen doped structure, and the third temperature It is the temperature suitable for carbonization of silk fabrics. It can be understood that the second temperature is higher than the first temperature, the third temperature is higher than the second temperature, and the first temperature, the second temperature and the third temperature are processed for the appropriate time, and the transition from the first temperature to the second temperature and The transition from the second temperature to the third temperature is at a suitable ramp rate.

In some embodiments of the present invention, the carbonized silk fabric is prepared by the following method: under the protection of inert gas, the silk fabric is subjected to a dehydration treatment at a first temperature between 100 ° C and 200 ° C for 1-2 h, and then at 300 ° C. The cyclization treatment is carried out at the second temperature between ℃-400℃ for 2-3h, and then the carbonization treatment is carried out at the third temperature between 950℃-1100℃ for 1-2h, and the silk fabric is heated to the first temperature, the second temperature The ramp rates of the temperature and the third temperature are independently 2°C to 10°C/min.

The above-mentioned inert gas is an inert gas commonly used in chemical and chemical reactions, such as argon, neon, nitrogen or their mixtures. In addition, an appropriate amount of hydrogen or ammonia can also be mixed into the inert gas, that is, the reaction atmosphere can be a mixed gas of an inert gas and hydrogen or ammonia. The mixed hydrogen and argon have reducing properties, which can reduce the oxygen doping content of the final carbonized silk fabric and improve its electrical conductivity.

In the above-mentioned carbonization method, when a large piece of silk fabric (eg, silk cloth) is used, it is usually cut into squares of suitable size and then processed. And, generally preferably, the silk fabric can be ultrasonicated for 15-20 min each with deionized water and absolute ethanol, and then dried at 60° C. for subsequent treatment.

The present invention has no specific limitation on the material of the silk fabric, but usually pure mulberry silk or tussah silk is preferred. The fabric is plain crepe mulberry silk of 22 mm.

In some embodiments of the flexible electrodes of the present invention, the electrode active material is a negative electrode active material. In the battery field, non-limiting examples of negative electrode active materials include lithium metal, silicon, graphite, metal oxides, and the like. For silicon, graphite, and metal oxide negative electrode active materials, it can usually be uniformly mixed with a binder and conductive additives in a certain ratio (eg (8-9):1:1) in an appropriate amount of solvent to obtain a negative electrode slurry Then, the negative electrode slurry is coated on the carbonized silk fabric, and the solvent is removed by vacuum drying to obtain a composite flexible negative electrode.

Further, in a preferred embodiment, the negative electrode active material is lithium metal, and the flexible electrode is correspondingly a flexible lithium negative electrode. The flexible and flexible lithium negative electrode is prepared by the following methods: cutting carbonized silk fabric into carbonized silk fabric pole pieces of suitable size, matching with lithium metal electrodes, and assembling a half-cell; under the condition of constant current, quantitatively depositing lithium metal onto the carbonized silk fabric pole piece; then take out the carbonized silk fabric pole piece deposited with lithium metal, rinse with an organic solvent, and dry to obtain a flexible lithium negative electrode. The drying method can be natural drying, low temperature drying, or other suitable drying methods. Usually, the current size is set in the range of 0.1-1 mA cm ^-2 , and the deposition amount of lithium metal is in the range of 1-20 mAh cm- ² . The organic solvent used can be, for example, dimethyl carbonate (DMC), 1,3-dioxolane (DOL) or dimethoxyethane (DME). It should be pointed out that although the electrodeposition method is used to composite lithium metal and carbonized silk fabric to prepare flexible lithium negative electrode, other composite methods known in the art such as lithium hot melt method can also be used to prepare flexible lithium negative electrode.

In other embodiments of the flexible electrodes of the present invention, the electrode active material is a positive electrode active material. In the battery field, non-limiting examples of positive active materials generally include nickel cobalt manganese ternary material (NCM), lithium cobalt oxide (LCO), lithium iron phosphate (LFP), nickel cobalt aluminum ternary material (NCA), manganese Lithium oxide (LMO) and lithium nickelate (LNO), etc.; and in metal-sulfur batteries such as lithium-sulfur batteries, the positive electrode active material is a positive electrode active material containing sulfur, such as elemental sulfur, sulfur composites (such as sulfur carbon, sulfur selenium or sulfur-tellurium complexes, etc.) or polysulfide compounds (such as Li ₂ S ₈ , Li ₂ S ₆ , etc.).

Further, in some preferred embodiments, the electrode active material is a positive electrode active material, and the positive electrode active material is one of nickel-cobalt-manganese ternary material (NCM), lithium cobalt oxide (LCO) and lithium iron phosphate (LFP). one or more. The flexible electrode is prepared by the following method: the positive electrode active material, the conductive additive and the binder are uniformly mixed in an appropriate amount of solvent according to the mass ratio of (4-9):(1-2):1 to obtain a positive electrode slurry; Then, the obtained positive electrode slurry is uniformly coated on the carbonized silk fabric, and vacuum-dried at 60° C.-80° C. for 12-16 hours to remove the solvent to obtain the flexible electrode. The conductive additives used are one or more of acetylene black, Ketjen black, Super P, Super C45, carbon nanotubes, and graphene, and the binder is a water-based binder (such as PAA, LA123, sericin) Or an organic solvent based binder (eg PVDF).

Further, in some other preferred embodiments, the electrode active material is a positive electrode active material, the positive electrode active material contains sulfur element, and the flexible electrode is correspondingly a flexible sulfur positive electrode. In simple terms, for elemental sulfur or sulfur complex, it can be mixed with conductive additives and binders in an appropriate amount of solvent to obtain a positive electrode slurry, and then the obtained positive electrode slurry can be uniformly coated on the carbonized silk fabric. , and vacuum drying to remove the solvent to obtain a flexible sulfur electrode; for polysulfide, it can be dissolved in the electrolyte, and then the electrolyte can be dropped onto the carbonized silk fabric to obtain a flexible sulfur electrode.

In a preferred embodiment for preparing a flexible sulfur positive electrode with simple sulfur, the flexible sulfur positive electrode is prepared by the following method: mixing sulfur powder and conductive additive in a mass ratio of (2-3):1 and fully grinding, and grinding the ground The mixture is subjected to a hydrothermal reaction at 150-160 ° C for 12-16 h under the protection of inert gas to obtain a sulfur compound; the obtained sulfur compound and binder are mixed in an appropriate amount of solvent according to the mass ratio of (8-9): 1 Then, the obtained positive electrode slurry is coated on the carbonized silk fabric, and vacuum-dried at 60°C-80°C for 12-16 hours to remove the solvent to obtain a flexible sulfur positive electrode. The conductive additive used is one or more of acetylene black, Ketjen black, Super P, Super C45, carbon nanotube, and graphene, and the binder is a water-based binder or an organic solvent-based binder.

The solvents used in the preparation of the above-mentioned flexible electrodes include organic solvents and water, and the specific solvents are subject to the binder used. For example, when an organic solvent-based binder (eg PVDF) is used as the binder, the solvent is an organic solvent; when a water-based binder (eg, LA123) is used as the binder, the solvent is water.

A second aspect of the present invention provides a flexible battery, which includes an electrode, a separator and an electrolyte, the electrode includes a positive electrode and a negative electrode, the separator is located between the positive electrode and the negative electrode, and the electrode includes the flexible electrode according to the first aspect of the present invention.

As described above, the flexible electrode of the present invention includes a flexible positive electrode and a flexible negative electrode, a preferred example of the flexible positive electrode is a flexible sulfur positive electrode, and a preferred example of the flexible negative electrode is a flexible lithium negative electrode. In some embodiments of the present invention, the flexible battery of the present invention comprises the flexible positive electrode of the present invention and other flexible negative electrodes in the battery field. In other embodiments of the present invention, the flexible battery of the present invention comprises the flexible negative electrode of the present invention and other flexible positive electrodes in the battery field. In yet other embodiments of the present invention, the flexible battery of the present invention comprises a flexible negative electrode of the present invention and a flexible positive electrode of the present invention. It should be pointed out that the innovation of the present invention lies in the flexible electrodes and the flexible batteries comprising the flexible electrodes. The separators and electrolytes in the flexible batteries can adopt the separators and electrolytes commonly used in the battery field or more specifically in the field of flexible batteries, which are not described in this paper. Repeat.

In some preferred embodiments of the flexible battery of the present invention, the negative electrode adopts the flexible lithium negative electrode of the first aspect of the present invention, and the flexible battery is correspondingly a flexible lithium battery. In other preferred embodiments of the flexible battery of the present invention, the positive electrode adopts the flexible sulfur positive electrode of the first aspect of the present invention, and the flexible battery is correspondingly a flexible sulfur battery. In further preferred embodiments of the flexible battery of the present invention, the negative electrode adopts the flexible lithium negative electrode of the first aspect of the present invention, and the positive electrode adopts the flexible sulfur positive electrode of the first aspect of the present invention, and the flexible battery is correspondingly a flexible lithium-sulfur battery.

The present invention will be further described in detail below through specific embodiments. It should be noted that these examples are intended to illustrate the invention and are not intended to limit the scope of the invention in any way.

Example 1

(1) Preparation and characterization of carbonized silk cloth

Cut the 22 mm plain crepe mulberry silk cloth into 4cm*6cm squares, pre-treat with deionized water and absolute ethanol by ultrasonic for 15min each, and then dry at 60°C for later use.

The pretreated silk was placed in a tube furnace, and under the protection of argon, the carbonization was carried out by gradient heating. To 350°C (heating rate 2°C/min), constant temperature for 3h; 350°C to 950°C (heating rate 3°C/min), constant temperature for 1h, to obtain carbonized silk cloth.

The SEM images of the prepared carbonized silk cloth are shown in Figures 1(a) and (b). It can be seen from the figures that the fiber structure of the carbonized silk cloth is complete and uniform, which contributes to good electrical conductivity.

The XPS diagram of nitrogen element of the prepared carbonized silk cloth is shown in Figure 2. It can be seen that the carbonized silk cloth is rich in nitrogen-doped structure, which is helpful for the adsorption of polysulfides when used in a flexible sulfur cathode, and inhibits the effect of polysulfides in sulfur batteries. The shuttle effect on the separator also makes the carbonized silk cloth have good lithophilicity, which can inhibit the generation of lithium dendrites when used in the lithium negative electrode.

The XPS diagram of the oxygen element of the prepared carbonized silk cloth is shown in Figure 3. It can be seen that the oxygen-rich doped structure is used for the flexible sulfur cathode, which is helpful for the adsorption of polysulfides and inhibits the "polysulfide" in lithium-sulfur batteries. Shuttle Effect".

(2) Preparation and characterization of flexible lithium anode

The carbonized silk cloth prepared above was cut into pole pieces of suitable size, matched with lithium metal electrodes (Tianjin Zhongneng Lithium Industry), and assembled into a half-cell in a glove box. Using the NewareCT2001A battery test system, 1-20mAh cm ^-2 lithium metal was quantitatively deposited on the carbonized silk cloth under the condition of a current density of 1mAcm ^-2 . After the end, the battery was disassembled in the glove box, and the carbonized silk cloth electrode deposited with lithium metal was taken out, rinsed three times with dimethoxyethane (DME), and air-dried to obtain a flexible lithium negative electrode.

The carbonized silk cloth composite lithium anode with 3 mAh cm ^-2 lithium metal deposited therein was characterized by SEM, and the results are shown in Figure 4. Compared with Fig. 1, it can be seen that lithium metal is evenly coated on the surface of carbonized silk cloth fibers. This is because carbonized silk cloth has a rich nitrogen-doped structure, which has good lithophilicity and can guide lithium metal to nucleate uniformly, thereby Inhibit the formation of lithium dendrites.

The carbonized silk cloth without lithium deposition was matched with lithium metal, the button-type half-cell was assembled, and the Coulomb efficiency test was carried out. Nitrogen-oxygen doping, similar to carbon cloth), the results are shown in Figure 5. It can be seen from the figure that the coulombic efficiency of carbonized silk cloth is obviously better than that of carbon felt (CF) and copper foil (Cu). Reduce the loss of lithium and improve the cycle stability of the battery.

A symmetrical battery was assembled with a carbonized silk cloth composite lithium negative electrode with 10mAh cm ^-2 of lithium metal deposited in it, and the cycle stability test was carried out. The control samples were still copper foil (Cu) and carbon felt (CF), both of which also deposited 10mAh. cm ^-2 Li metal, the results are shown in Figure 6. It can be seen from the figure that under the condition of 2mA cm ^-2 -2mAh cm ^-2 , the symmetric battery assembled with carbonized silk cloth composite lithium anode can stably cycle for 550h, showing excellent cycle stability, while copper foil (Cu) The symmetric battery assembled with carbon felt (CF) composite lithium anode can only cycle stably for about 300-340 h, respectively, because the three-dimensional structure of carbonized silk cloth can reduce the local current density, and the abundant nitrogen-doped structure can guide the lithium metal Uniform nucleation, thereby inhibiting the growth of lithium dendrites and improving the cycling stability of the battery.

(3) Preparation and characterization of flexible sulfur cathode

Mix sulfur powder and Ketjen black in a mass ratio of 3:1, and grind thoroughly. Then, the ground mixture was placed in a hydrothermal reactor, and under the protection of argon, the temperature was kept at 155 °C for 16 h to obtain a sulfur-carbon composite. Using water as a solvent and sericin as a binder, the sulfur-carbon composite and the binder are fully mixed according to a mass ratio of 9:1 to obtain an aqueous electrode slurry. The electrode slurry was coated on the carbonized silk cloth prepared above, and vacuum-dried at 60° C. for 16 h to remove the solvent to obtain a flexible sulfur positive electrode. The SEM morphology is shown in FIG. 7 . It can be seen from the figure that with carbonized silk cloth as the current collector, the slurry can fully penetrate into the three-dimensional structure of carbonized silk cloth, which is conducive to the uniform distribution of active substances. Not easy to powder.

In the same way, a sulfur cathode with carbon felt CF (three-dimensional material, no nitrogen and oxygen doping, similar to carbon cloth) and graphite sheet GF (two-dimensional material) as current collectors was prepared as a comparison sample.

The prepared flexible sulfur cathode and comparative sulfur cathode were matched with lithium metal in a glove box, respectively, and assembled into half-cells for electrochemical performance tests. The battery cycle performance is shown in Figures 8 and 9. Figure 8 shows the flexible sulfur cathode prepared based on carbonized silk cloth, under the condition of sulfur loading of 2.55 mg cm ^-2 , after 200 cycles, the specific capacity is 784 mAh g ^-1 , the capacity retention rate is 79.5%, and the average Coulombic efficiency is as high as 98.95% , the performance is significantly better than that of carbon felt (CF) and graphite sheet (GF) as the control. This is because the three-dimensional structure of carbonized silk cloth can buffer the stress caused by the volume change of sulfur, and the rich nitrogen-oxygen doped structure can adsorb polysulfides, inhibit the shuttle effect of polysulfides on the sulfur battery separator, and the cycle performance of lithium-sulfur batteries. be improved. Figure 9 shows that when the sulfur loading is increased, the lithium ^- sulfur battery with carbonized silk ^cloth as the current collector can still cycle stably. The flexible sulfur cathode is suitable for fabricating high areal capacity lithium-sulfur batteries.

(4) Preparation of flexible lithium-sulfur batteries

The above-prepared flexible lithium anode and flexible sulfur cathode were cut to the size of 2cm*4cm, respectively. In the glove box, the two electrodes were matched, using Celgard's polypropylene separator and conventional lithium-sulfur electrolyte (composition: 1.0M LiTFSI/DME: DOL=1:1 Vol%, adding 2.0% LiNO ₃ , company: Suzhou Duoduo Chemical Reagent Co., Ltd.), using aluminum-plastic film as a package to assemble a soft-pack battery to obtain a flexible lithium-sulfur battery based on carbonized silk cloth.

Figure 10 shows the cycle performance diagram of the flexible soft ^- pack lithium ^- sulfur full battery assembled based on carbonized silk cloth. Good stability, the average Coulomb efficiency of the first 150 cycles is as high as 98.9%, after 150 cycles, after 1000 cycles of bending under the condition of a curvature radius of 5mm, the battery capacity is only slightly attenuated, and it can still be cycled stably, and the Coulomb efficiency remains basically unchanged. .

Figure 11 is also a graph of the cycle performance of the flexible soft ^- packed lithium ^- sulfur full battery assembled based on carbonized silk cloth. Bending 1000 times under the condition of a radius of 5mm, the battery can still cycle stably, and the overall average Coulomb efficiency is as high as 98.4%.

Both Figure 10 and Figure 11 show that the flexible soft-packed lithium-sulfur full battery assembled based on carbonized silk cloth has excellent flexibility and cycle stability, and has a good application prospect.

Example 2

(1) Preparation and characterization of carbonized silk cloth

Cut 30 mm plain crepe mulberry silk cloth into squares of 4 cm*6 cm, pre-treated with deionized water and absolute ethanol by ultrasonic for 15 min each, and then dried at 60°C for use.

The pretreated silk was placed in a tube furnace, and under the protection of argon, the carbonization was carried out by gradient heating. To 400°C (heating rate 3°C/min), constant temperature for 3h; 400°C to 1000°C (heating rate 3°C/min), constant temperature for 1h, to obtain carbonized silk cloth.

The SEM images of the obtained carbonized silk cloth are shown in Figures 1(c) and (d). It can be seen from the figures that the fibers of the carbonized silk cloth are complete in structure and uniform in distribution, which contributes to good electrical conductivity.

(2) Preparation of flexible lithium anode

The carbonized silk cloth prepared above was cut into pole pieces of suitable size, matched with lithium metal electrodes (Tianjin Zhongneng Lithium Industry), and assembled into a half-cell in a glove box. Using the NewareCT2001A battery test system, under the condition of a current density of 0.5mAcm ^-2 , 3-20mAh cm ^-2 lithium metal was quantitatively deposited on the carbonized silk cloth. After the end, the battery was disassembled in the glove box, and the carbonized silk cloth electrode deposited with lithium metal was taken out, rinsed three times with 1,3-dioxolane (DOL), and dried naturally to obtain a flexible lithium negative electrode.

(3) Preparation of flexible sulfur cathode

Mix sulfur powder and super P in a mass ratio of 3:1, and grind them thoroughly. Then, the ground mixture was placed in a hydrothermal reactor, and under the protection of argon, the temperature was kept at 155 °C for 12 h to obtain a sulfur-carbon composite. Using N-methylpyrrolidone (NMP) as a solvent and polyvinylidene tetrafluoroethylene (PVDF) as a binder, the sulfur-carbon composite and the binder are fully mixed in a mass ratio of 9:1 to obtain an organic solvent-based electrode slurry . The electrode slurry was coated on the carbonized silk cloth prepared above, and vacuum-dried at 80° C. for 12 h to remove the solvent to obtain a flexible sulfur positive electrode.

(4) Preparation of flexible lithium-sulfur batteries

The above-prepared flexible lithium anode and flexible sulfur cathode were cut to the size of 2cm*4cm, respectively. In the glove box, the two electrodes were matched, using Celgard's polypropylene separator and conventional lithium-sulfur electrolyte (composition: 1.0M LiTFSI/DME: DOL=1:1 Vol%, adding 2.0% LiNO ₃ , company: Suzhou Duoduo Chemical Reagent Co., Ltd.), using aluminum-plastic film as a package to assemble a soft-pack battery to obtain a flexible lithium-sulfur battery based on carbonized silk cloth.

Example 3

(1) Preparation of carbonized silk cloth

Cut 40 mm plain crepe mulberry silk cloth into squares of 4 cm*6 cm, pre-treat with deionized water and absolute ethanol for 20 min each by ultrasonic, and then dry at 60°C for use.

The pretreated silk was placed in a tube furnace, and under the protection of neon gas, the carbonization was carried out by gradient heating. To 350°C (heating rate 5°C/min), constant temperature for 2h; 350°C to 950°C (heating rate 5°C/min), constant temperature for 2h, to obtain carbonized silk cloth.

(2) Preparation of flexible lithium anode

The carbonized silk cloth prepared above was cut into pole pieces of suitable size, matched with lithium metal electrodes (Tianjin Zhongneng Lithium Industry), and assembled into a half-cell in a glove box. Using the NewareCT2001A battery test system, 5-15mAh cm ^-2 of lithium metal was quantitatively deposited on the carbonized silk cloth under the condition of a current density of 1 mAcm ^-2 . After the end, the battery was disassembled in the glove box, and the carbonized silk cloth electrode deposited with lithium metal was taken out, rinsed three times with dimethoxyethane (DME), and air-dried to obtain a flexible lithium negative electrode.

(3) Preparation of flexible lithium cobalt oxide cathode

In an appropriate amount of N-methylpyrrolidone (NMP) solvent, LCO (lithium cobaltate), super P (conductive additive), PVDF (binder) are fully mixed in a mass ratio of 93:3:2 to obtain a uniform electrode paste. The electrode slurry was coated on the carbonized silk cloth prepared above, and vacuum-dried at 80° C. for 12 h to obtain a flexible lithium cobalt oxide positive electrode.

(4) Preparation of flexible lithium battery

The flexible lithium negative electrode and flexible lithium cobalt oxide positive electrode prepared above were cut into sizes of 2cm*4cm, respectively. In a glove box, the two electrodes were matched using a polypropylene separator from Celgard and a conventional lithium-sulfur electrolyte (composition: 1.0M LiTFSI/DME:DOL=1:1 Vol% with 2.0% LiNO ₃ added, Inc.: Suzhou Duoduo Chemical Reagent Co., Ltd.), using aluminum-plastic film as a package, assembling a soft pack battery, and obtaining a flexible lithium battery based on carbonized silk cloth with flexible lithium cobalt oxide as the positive electrode material.

Example 4

(1) Preparation of carbonized silk cloth

Cut the 23-momi tussah silk cloth into 4cm*6cm squares, sonicate with deionized water and absolute ethanol for 20 minutes each, and then dry at 60°C for later use.

The pretreated silk was arranged in a tube furnace, and under the protection of an argon-hydrogen mixture (the volume ratio of argon and hydrogen was 9:1), the carbonization was carried out by gradient heating, and the temperature control program was: the temperature was raised to 100 ° C ( Heating rate of 5°C/min), constant temperature for 1h; 100°C to 300°C (heating rate of 5°C/min), constant temperature for 2h; 300°C to 1050°C (heating rate of 5°C/min), constant temperature for 1h, to obtain carbonization Silk cloth.

(2) Preparation of flexible lithium anode

The carbonized silk cloth prepared above was cut into pole pieces of suitable size, matched with lithium metal electrodes (Tianjin Zhongneng Lithium Industry), and assembled into a half-cell in a glove box. Using NewareCT2001A battery test system, under the condition of current density of 0.8mAcm ^-2 , 5-15mAh cm ^-2 lithium metal was quantitatively deposited on carbonized silk cloth. After the end, the battery was disassembled in the glove box, and the carbonized silk cloth electrode deposited with lithium metal was taken out, rinsed three times with dimethoxyethane (DME), and air-dried to obtain a flexible lithium negative electrode.

(3) Preparation of flexible nickel-cobalt-manganese cathode

In an appropriate amount of N-methylpyrrolidone (NMP) solvent, NCM (nickel-cobalt-manganese ternary material), super P (conductive additive), PVDF (binder) are thoroughly mixed in a mass ratio of 80:10:10 , to obtain a uniform electrode paste. The electrode slurry was coated on the carbonized silk cloth prepared above, and vacuum-dried at 80° C. for 12 h to obtain a flexible nickel-cobalt-manganese positive electrode.

(4) Preparation of flexible lithium battery

The flexible lithium anode and flexible nickel-cobalt-manganese cathode prepared above were cut into sizes of 2cm*4cm, respectively. In a glove box, the two electrodes were matched using a polypropylene separator from Celgard and a conventional lithium-sulfur electrolyte (composition: 1.0M LiTFSI/DME:DOL=1:1 Vol% with 2.0% LiNO ₃ added, Inc.: Suzhou Duoduo Chemical Reagent Co., Ltd.), used aluminum-plastic film as a package, assembled a soft-pack battery, and obtained a flexible lithium battery based on carbonized silk cloth with flexible nickel-cobalt-manganese as the positive electrode material.

Example 5

(1) Preparation of carbonized silk cloth

Cut the 12-mummy tussah silk cloth into 4cm*6cm squares, sonicate with deionized water and absolute ethanol for 15min each, and then dry at 60°C for later use.

Arrange the pretreated silk in a tube furnace, and under the protection of argon-ammonia mixture (the volume ratio of argon and ammonia is 9:1), the carbonization is carried out by gradient heating, and the temperature control program is: the temperature is raised to 150 ° C (heating rate 5°C/min), constant temperature for 1.5h; heating from 150°C to 400°C (heating rate 3°C/min), constant temperature for 2.5h; heating from 400°C to 1100°C (heating rate 5°C/min), constant temperature for 1h, Carbonized silk cloth was obtained.

(2) Preparation of flexible lithium anode

The carbonized silk cloth prepared above was cut into pole pieces of suitable size, matched with lithium metal electrodes (Tianjin Zhongneng Lithium Industry), and assembled into a half-cell in a glove box. The NewareCT2001A battery test system was used to quantitatively deposit 3-10mAh cm ^-2 of lithium metal onto the carbonized silk cloth under the condition of a current density of 0.5mAcm ^-2 . After the end, the battery was disassembled in the glove box, and the carbonized silk cloth electrode deposited with lithium metal was taken out, rinsed three times with dimethoxyethane (DME), and air-dried to obtain a flexible lithium negative electrode.

(3) Preparation of flexible lithium iron phosphate cathode

In an appropriate amount of N-methylpyrrolidone (NMP) solvent, LiFePO ₄ (lithium iron phosphate), acetylene black (conductive additive), and PVDF (binder) were thoroughly mixed in a mass ratio of 70:15:15 to obtain Homogeneous electrode paste. The electrode slurry was coated on the carbonized silk cloth prepared above, and vacuum-dried at 80° C. for 16 h to obtain a flexible lithium iron phosphate positive electrode.

(4) Preparation of flexible lithium battery

The flexible lithium anode and flexible lithium iron phosphate cathode prepared above were cut into sizes of 2cm*4cm, respectively. In a glove box, the two electrodes were matched using a polypropylene separator from Celgard and a conventional lithium-sulfur electrolyte (composition: 1.0M LiTFSI/DME:DOL=1:1 Vol% with 2.0% LiNO ₃ added, Inc.: Suzhou Duoduo Chemical Reagent Co., Ltd.), using aluminum-plastic film as a package, assembling a soft-pack battery, and obtaining a flexible lithium battery based on carbonized silk cloth with flexible lithium iron phosphate as the positive electrode material.

The present invention has been described above using specific examples, which are only used to help understand the present invention, and are not intended to limit the present invention. Those skilled in the art to which the present invention pertains can also make some simple deductions, modifications or substitutions according to the concept of the present invention. These deductions, modifications or alternatives also fall within the scope of the claims of the present invention.

Claims (10)

1. A flexible electrode, characterized in that the flexible electrode comprises a carbonized silk fabric and an electrode active material compounded with the carbonized silk fabric. 2. The flexible electrode according to claim 1, wherein the carbonized silk fabric is prepared by the following method: under the protection of an inert gas, the silk fabric is dehydrated at a first temperature, and at a second temperature Carry out pre-cyclization treatment, and carry out carbonization treatment at the third temperature to obtain the carbonized silk fabric; Preferably, under the protection of inert gas, the silk fabric is subjected to dehydration treatment at a first temperature between 100°C and 200°C for 1-2 hours, and then cyclized at a second temperature between 300°C and 400°C. 2-3h, then carbonization treatment at a third temperature between 950℃-1100℃ for 1-2h, the heating rate of the silk fabric to the first temperature, the second temperature and the third temperature is independently 2℃-10 °C/min. 3. The flexible electrode according to claim 1 or 2, wherein the electrode active material is a negative electrode active material, and the negative electrode active material is lithium metal, silicon, graphite or metal oxide; preferably, the The negative active material is lithium metal, and the flexible electrode is a flexible lithium negative electrode. 4. The flexible electrode according to claim 3, wherein the flexible lithium negative electrode is prepared by the following method: cutting the carbonized silk fabric into a carbonized silk fabric pole piece of suitable size, which is matched with the lithium metal electrode, Assembled into a half-cell; under the condition of constant current, quantitatively deposit lithium metal on the carbonized silk fabric pole piece; then take out the carbonized silk fabric pole piece deposited with lithium metal, rinse with organic solvent, and dry to obtain the flexible lithium negative electrode. 5 . The flexible electrode according to claim 4 , wherein the magnitude of the current is in the range of 0.1-1 mA cm ^-2 , and the deposition amount of the lithium metal is in the range of 1-20 mAh cm ^-2 . 6 . 6. The flexible electrode according to claim 1 or 2, wherein the electrode active material is a positive electrode active material, the positive electrode active material comprises elemental sulfur, and the flexible electrode is a flexible sulfur positive electrode. 7. The flexible electrode according to claim 6, characterized in that, the flexible electrode is prepared by the following method: mixing sulfur powder and conductive additive according to the mass ratio of (2-3): 1 and fully grinding, and grinding well The mixture is subjected to a hydrothermal reaction at 150-160 ° C for 12-16 h under the protection of inert gas to obtain a sulfur compound; the obtained sulfur compound and binder are in a solvent according to the mass ratio of (8-9): 1. Mixing thoroughly to obtain a positive electrode slurry; then coating the obtained positive electrode slurry on the carbonized silk fabric, and vacuum drying at 60°C-80°C for 12-16 hours to remove the solvent to obtain the flexible electrode; Preferably, the conductive additive is one or more of acetylene black, Ketjen black, Super P, Super C45, carbon nanotubes, and graphene, and the binder is a water-based binder or an organic solvent-based binder binding agent. 8. The flexible electrode according to claim 1 or 2, wherein the electrode active material is a positive electrode active material, and the positive electrode active material is a nickel-cobalt-manganese ternary material, lithium cobalt oxide, lithium iron phosphate, nickel One or more of cobalt-aluminum ternary material, lithium manganate, and lithium nickelate. 9. The flexible electrode according to claim 8, characterized in that, the flexible electrode is prepared by the following method: combining the positive electrode active material with conductive additive and binder according to (4-9): (1-2) The mass ratio of : 1 was evenly mixed in the solvent to obtain a positive electrode slurry; then the obtained positive electrode slurry was uniformly coated on the carbonized silk fabric, and vacuum-dried at 60 ℃-80 ℃ for 12-16h to remove the solvent, obtaining the flexible electrode; Preferably, the conductive additive is one or more of acetylene black, Ketjen black, Super P, Super C45, carbon nanotubes, and graphene, and the binder is a water-based binder or an organic solvent-based binder binding agent. 10. A flexible battery comprising an electrode, a separator and an electrolyte, the electrode comprising a positive electrode and a negative electrode, and the separator is located between the positive electrode and the negative electrode, characterized in that the electrode comprises the electrode according to claim 1- The flexible electrode of any one of 9; Preferably, the negative electrode is the flexible electrode according to any one of claims 3-5, that is, a flexible lithium negative electrode; Preferably, the positive electrode is the flexible electrode according to any one of claims 6-7, that is, a flexible sulfur positive electrode; More preferably, the negative electrode is the flexible electrode according to any one of claims 3-5, that is, a flexible lithium negative electrode, and the positive electrode is the flexible electrode according to any one of claims 6-7, that is, a flexible lithium negative electrode. A flexible sulfur cathode, the flexible battery is a flexible lithium-sulfur battery.

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