阅读说明：本技术 基于碳化蚕丝织物的柔性电极和柔性电池 (Flexible electrode and flexible battery based on carbonized silk fabric ) 是由 邓永红 常建 安亚楠 王朝阳 罗超 于 2020-06-16 设计创作，主要内容包括：本发明提供一种基于碳化蚕丝织物的柔性电极,包含碳化蚕丝织物和与该碳化蚕丝织物复合的电极活性材料。本发明的柔性电极尤其为柔性锂负极和柔性硫正极。本发明还提供一种包含该柔性电极的柔性电池,尤其是柔性锂硫电池。本发明的柔性电极和柔性电池具有以下优点：碳化蚕丝织物的原材料来源广,制备过程简单,绿色环保,成本低；碳化蚕丝织物具有三维空间结构,柔性和导电性良好,且存在丰富的氮氧掺杂结构,对多硫化物和金属锂均具更好的亲和性,可以抑制锂枝晶的生长,抑制多硫化物在锂硫电池中的“穿梭效应”,提高电池的循环稳定性；碳化蚕丝织物的面质量较轻,有利于提高电池的能量密度。(The invention provides a flexible electrode based on a carbonized silk fabric, which comprises the carbonized silk fabric and an electrode active material compounded with the carbonized silk fabric. The flexible electrodes of the invention are in particular flexible lithium cathodes and flexible sulfur anodes. The invention also provides a flexible battery, in particular a flexible lithium-sulfur battery, comprising the flexible electrode. The flexible electrode and the flexible battery have the following advantages: the carbonized silk fabric has wide raw material sources, simple preparation process, environmental protection and low cost; the carbonized silk fabric has a three-dimensional structure, is good in flexibility and conductivity, has rich nitrogen-oxygen doped structures, has better affinity to polysulfide and metal lithium, can inhibit the growth of lithium dendrite, inhibits the shuttle effect of polysulfide in a lithium-sulfur battery, and improves the cycling stability of the battery; the carbonized silk fabric has light surface weight and is beneficial to improving the energy density of the battery.)

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 of claim 1, wherein the carbonized silk fabric is prepared by a method comprising: under the protection of inert gas, dehydrating the silk fabric at a first temperature, performing pre-cyclization treatment at a second temperature, and performing carbonization treatment at a third temperature to obtain the carbonized silk fabric;

preferably, under the protection of inert gas, the silk fabric is dehydrated for 1-2h at a first temperature of 100-200 ℃, then cyclized for 2-3h at a second temperature of 300-400 ℃, and then carbonized for 1-2h at a third temperature of 950-1100 ℃, and the heating rates of the silk fabric to the first temperature, the second temperature and the third temperature are independently 2-10 ℃/min.

3. The flexible electrode of claim 1 or 2, wherein the electrode active material is a negative active material that is lithium metal, silicon, graphite, or a metal oxide; preferably, the negative active material is lithium metal and the flexible electrode is a flexible lithium negative electrode.

4. The flexible electrode of claim 3, wherein the flexible lithium negative electrode is prepared by: cutting the carbonized silk fabric into carbonized silk fabric pole pieces with proper sizes, matching the carbonized silk fabric pole pieces with the lithium metal electrodes, and assembling the carbonized silk fabric pole pieces into a half-cell; quantitatively depositing lithium metal on the carbonized silk fabric pole piece under the condition of constant current; and then taking out the carbonized silk fabric pole piece deposited with the lithium metal, washing with an organic solvent, and drying to obtain the flexible lithium negative electrode.

5. The flexible electrode of claim 4 wherein the current level is between 0.1 and 1mA cm^-2In the range of 1 to 20mAh cm^-2Within the range of (1).

6. The flexible electrode according to claim 1 or 2, wherein the electrode active material is a positive electrode active material comprising elemental sulfur, and the flexible electrode is a flexible sulfur positive electrode.

7. The flexible electrode of claim 6, wherein the flexible electrode is prepared by: mixing and fully grinding sulfur powder and a conductive additive according to the mass ratio of (2-3) to 1, and carrying out hydrothermal reaction on the ground mixture at the temperature of 150-160 ℃ for 12-16h under the protection of inert gas to obtain a sulfur compound; fully mixing the obtained sulfur compound and the binder in a solvent according to the mass ratio of (8-9) to 1 to obtain anode slurry; coating the obtained positive electrode slurry on the carbonized silk fabric, and performing vacuum drying at the temperature of 60-80 ℃ for 12-16h 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 an aqueous binder or an organic solvent binder.

8. The flexible electrode of claim 1 or 2, wherein the electrode active material is a positive electrode active material, and the positive electrode active material is one or more of nickel cobalt manganese ternary material, lithium cobaltate, lithium iron phosphate, nickel cobalt aluminum ternary material, lithium manganate, and lithium nickelate.

9. The flexible electrode of claim 8, wherein the flexible electrode is prepared by: uniformly mixing the positive electrode active material, a conductive additive and a binder in a solvent according to the mass ratio of (4-9) to (1-2) to 1 to obtain positive electrode slurry; then uniformly coating the obtained positive electrode slurry on the carbonized silk fabric, and performing vacuum drying at the temperature of 60-80 ℃ for 12-16h 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 an aqueous binder or an organic solvent binder.

10. A flexible battery comprising an electrode, a separator and an electrolyte, the electrode comprising a positive electrode and a negative electrode, the separator being located between the positive electrode and the negative electrode, characterized in that the electrode comprises a flexible electrode according to any one of claims 1-9;

preferably, the negative electrode is a flexible electrode according to any one of claims 3 to 5, i.e. a flexible lithium negative electrode;

preferably, the positive electrode is a flexible electrode according to any one of claims 6-7, i.e. a flexible sulfur positive electrode;

more preferably, the negative electrode is a flexible electrode according to any one of claims 3 to 5, i.e. a flexible lithium negative electrode, the positive electrode is a flexible electrode according to any one of claims 6 to 7, i.e. a flexible sulfur positive electrode, and the flexible battery is a flexible lithium sulfur battery.

Technical Field

The invention belongs to the technical field of batteries, and particularly relates to a flexible electrode and a flexible battery based on a carbonized silk fabric, in particular to a flexible electrode containing a carbonized silk fabric, especially a flexible lithium negative electrode and a flexible sulfur positive electrode, and a flexible battery containing the flexible electrode, especially a flexible lithium sulfur battery.

Background

In recent years, with the rapid development and emerging application of flexible wearable electronic products such as scroll display screens, electronic textiles, soft robots, internet of things systems, and bioelectronic products, a battery which is light, thin, flexible, bendable, high in energy density, and stable in performance is urgently needed to be developed to provide power for various wearable and flexible electronic devices. At present, a rigid lithium ion battery adopting metal foil as a current collector can generate fatigue fracture and active substance stripping when being repeatedly bent, and is easy to cause the attenuation of electrochemical and mechanical properties; meanwhile, the lithium ion battery adopts a layered lithium-embedded active material with low theoretical specific capacity, and a thicker electrode is needed, so that the excellent flexibility and high energy density of the lithium battery are difficult to realize.

The lithium-sulfur battery is used as a next-generation lithium battery technology, sulfur and metal lithium are respectively used as anode and cathode materials of the battery, the lithium-sulfur battery has the theoretical advantage of extremely high specific capacity (lithium: 3860 mAh/kg; sulfur: 1675mAh/kg), and the lithium-sulfur battery is very suitable for application of wearable and flexible electronic device products and draws wide attention at home and abroad. However, the application of lithium sulfur batteries still faces numerous challenges. In the aspect of a negative electrode, the SEI film on the surface of the negative electrode is easy to continuously damage and the electrolyte is continuously consumed due to huge volume change and lithium dendrite growth in the lithium metal charging and discharging process; on the positive electrode side, the sulfur elution of the positive electrode occurs during the use of the battery, and polysulfides (e.g., Li) are produced₂S₄、Li₂S₆、Li₂S₈Etc.) that can dissolve in the electrolyte and pass through the battery separator, resulting in the continual loss of active sulfur during cycling and electrolyte consumption. It can be seen that the above factors all result in unstable electrochemical performance of the lithium-sulfur battery.

The adoption of the flexible conductive substrate with a high specific area to replace a metal foil as a current collector is an important way for improving the electrochemical performance and mechanical flexibility of the lithium-sulfur battery. At present, flexible current collector substrates of lithium-sulfur electrodes mainly comprise two types, one type is carbon nanotubes, graphene and cellulose carbon paper, and the other type is carbon fabric. The carbon paper has the characteristics of light weight, high conductivity and the like, and the lithium sulfur active substance can be directly deposited on the thin-film carbon paper to prepare the flexible electrode, so that the light flexible lithium sulfur battery can be assembled, but the flexible lithium sulfur battery is generally low in energy density and poor in bending stability. The carbon fabric has the advantages of high flexibility, a porous net structure, good chemical stability and the like, and the lithium sulfur electrode prepared by using the carbon fabric has excellent mechanical flexibility. Research teams at home and abroad try to load high-activity lithium sulfur substances on the surface of carbon fabric by using vacuum filtration, liquid impregnation, electrodeposition, hot melting and other modes to realize the preparation of the flexible lithium sulfur electrode. However, commercial carbon fabric has high areal mass density and poor affinity to both polysulfide and lithium metal, and cannot effectively inhibit the shuttle effect and lithium dendrite growth of polysulfide, so that the electrochemical and mechanical stability of the carbon fabric lithium-sulfur battery is often poor. Although a great deal of previous work improves the electrochemical and mechanical stability of the lithium-sulfur battery with the fabric carbide through surface modification (such as heterogeneous atom doping, metal sulfide modification, transition metal coating and the like), most of the surface modification processes are complicated and the interface stability is poor. Therefore, it remains a great challenge to realize high performance flexible lithium sulfur electrodes and full cells using a simple and efficient method.

Disclosure of Invention

The invention aims to solve the technical problems of the existing carbonized fabric and carbonized fabric lithium-sulfur batteries, and the aim is achieved by the innovative technical scheme of the flexible electrode and the flexible battery based on the carbonized silk fabric.

In particular, 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 inert gas, the silk fabric is dehydrated at a first temperature, pre-cyclized at a second temperature and carbonized at a third temperature to obtain the carbonized silk fabric.

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

In one embodiment of the flexible electrode of the present invention, the electrode active material is a negative active material, and the negative active material is lithium metal, silicon, graphite, or a metal oxide. Preferably, the negative 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 carbonized silk fabric pole pieces with proper sizes, matching the carbonized silk fabric pole pieces with lithium metal electrodes, and assembling the carbonized silk fabric pole pieces into a half-cell; quantitatively depositing lithium metal on the carbonized silk fabric pole piece under the condition of constant current; and then taking out the carbonized silk fabric pole piece deposited with the lithium metal, washing with an organic solvent, and drying to obtain the flexible lithium negative electrode.

Further, the current is 0.1-1mA cm-²In the range of 1-20mAh cm-²Within the range of (1).

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

Further, the flexible electrode is prepared by the following method: mixing and fully grinding sulfur powder and a conductive additive according to the mass ratio of (2-3) to 1, and carrying out hydrothermal reaction on the ground mixture at the temperature of 150-160 ℃ for 12-16h under the protection of inert gas to obtain a sulfur compound; fully mixing the obtained sulfur compound and the binder in a proper amount of solvent according to the mass ratio of (8-9) to 1 to obtain anode slurry; and coating the obtained positive electrode slurry on the carbonized silk fabric, and performing vacuum drying at 60-80 ℃ for 12-16h to remove the solvent to obtain the flexible electrode, namely the 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 that is one or more of nickel cobalt manganese ternary material (NCM), Lithium Cobaltate (LCO), lithium iron phosphate (LFP), nickel cobalt aluminum ternary material (NCA), Lithium Manganate (LMO), Lithium Nickelate (LNO).

Further, the flexible electrode is prepared by the following method: uniformly mixing the positive electrode active material, a conductive additive and a binder in a proper amount of solvent according to the mass ratio of (4-9) to (1-2) to 1 to obtain positive electrode slurry; and then uniformly coating the obtained positive electrode slurry on the carbonized silk fabric, and performing vacuum drying at the temperature of 60-80 ℃ for 12-16h 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 located between the positive and negative electrodes, the electrode comprising a flexible electrode according to the first aspect of the invention.

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

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

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

The invention has the beneficial effects that:

the invention takes the carbonized silk fabric derived based on silk fabric carbonization as the flexible carbon-based material, and the carbonized silk fabric is applied to the preparation of flexible electrodes (including flexible anodes and flexible cathodes) and flexible batteries for the first time, including preferred flexible lithium cathodes and flexible sulfur anodes and preferred flexible lithium sulfur batteries, so that the invention has the following beneficial effects:

(1) the carbonized silk fabric has the advantages of wide raw material source, simple preparation process, environmental protection and low cost.

(2) The carbonized silk fabric has a three-dimensional space structure, is good in flexibility and conductivity, has rich nitrogen-oxygen doped structures, and has better affinity to polysulfide and metal lithium compared with commercial carbonized fabrics. Therefore, when the carbonized silk fabric is used for the lithium cathode, the local current density can be reduced, lithium metal is guided to be uniformly nucleated, and the growth of lithium dendrites is inhibited; the sulfur-containing lithium sulfur battery anode can buffer the stress caused by the volume change of sulfur in the battery cycle process, adsorb polysulfide generated on the sulfur anode, and inhibit the shuttle effect of the lithium sulfur battery, thereby improving the cycle stability of the battery.

(3) The surface weight of the carbonized silk fabric is light compared to the conventional commercial carbon cloth (the surface weight of the commercial carbon cloth is usually 12.6mg cm)^-2The surface mass of the carbonized silk fabric is 1.8-6.3mg cm^-2) And the energy density of the battery is improved.

(4) The flexible lithium cathode and the flexible sulfur anode of the invention show good flexibility and cycling stability, can be matched with each other or matched with other flexible electrodes to assemble a flexible battery, so as to improve the energy density and the cycling performance of the flexible battery, and have good application prospect.

Drawings

Fig. 1 shows SEM images of carbonized silk cloths obtained in examples 1 and 2 of the present invention, wherein (a) and (b) show SEM images of carbonized silk cloths obtained in example 1, and (c) and (d) show SEM images of carbonized silk cloths obtained in example 2;

FIG. 2 shows an XPS chart of nitrogen element of a carbonized silk cloth obtained in example 1 of the present invention;

FIG. 3 shows an XPS chart of oxygen element of a carbonized silk cloth obtained in example 1 of the present invention;

FIG. 4 shows the deposition of 3mAh cm of the carbonized silk cloth obtained in example 1 of the present invention^-2SEM images after lithium metal;

FIG. 5 shows a coulombic efficiency chart of a carbonized silk cloth obtained in example 1 of the present invention;

fig. 6 shows the results of the cycling stability test of a symmetric battery assembled by the carbonized silk cloth composite lithium electrode prepared in example 1 of the present invention;

fig. 7 shows an SEM image of a sulfur positive electrode using a carbonized silk cloth as a current collector in example 1 of the present invention, in which (a) is a front view and (b) is a sectional view;

FIG. 8 is a graph showing the cycle performance of the lithium sulfur battery assembled in example 1 of the present invention;

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

fig. 10 shows a cycle performance chart of the flexible soft-package lithium-sulfur battery using the carbonized silk cloth as the current collector in example 1 of the present invention;

fig. 11 shows a cycle performance chart of the flexible soft package lithium-sulfur battery using the carbonized silk cloth as the current collector in example 1 of the present invention.

Detailed Description

In order to make the technical problems solved by the present invention, the technical solutions adopted and the advantages obtained by the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and the specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

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

The invention creatively compounds the carbonized silk fabric as a base material and an electrode active material, and utilizes the flexibility and the conductivity of the carbonized silk fabric to manufacture the flexible electrode. The composite material can be compounded with a positive active material to manufacture a flexible positive electrode, and can also be compounded with a negative active material to manufacture a flexible negative electrode. The prepared flexible positive electrode or the flexible positive electrode can be further used for manufacturing flexible batteries. The term "composite" as used herein is to be understood in a broad sense including any way of electrically combining the carbonized silk fabric with the electrode active material. For example, a flexible lithium negative electrode described below is prepared by depositing lithium metal on a carbonized silk fabric, in which case the carbonized silk fabric is composited with an electrode active material by deposition. As 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 a carbonized silk fabric, in which case the carbonized silk fabric is combined with the electrode active material by a coating method.

The silk is spun by silkworm in the dormancy stage before the silkworm becomes a silkworm moth, and the silk comprises mulberry silk, tussah silk, castor-oil plant silk, cassava silk and the like according to the varieties of the silkworm, and the mulberry silk and the tussah silk are commonly used. Silk is one of natural protein fibers, and consists of sericin at the outer layer and fibroin (fibroin) at the inner layer. The silk has small diameter, smoothness, luster and elasticity, and can be used for fabrics without spinning, and the silk can be formed into continuous rope-shaped filaments only by merging and twisting two strands. Silk fabrics are elegant in appearance, comfortable to wear, and have aesthetic value, and have been the material of high-end apparel for thousands of years. Because silk fabric is rich in carbon element, soft frivolous, along with the rise of flexible battery, flexible wearable equipment, silk fabric has also aroused people's very big interest as flexible conducting material's raw materials.

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

Generally, carbonized silk fabrics are made by the following process: under the protection of inert gas, dehydrating the silk fabric at a first temperature, cyclizing at a second temperature, and carbonizing at a third temperature to obtain the carbonized silk fabric.

Without being limited by theory, it is believed that after the fibroin in the silk fabric is heated at a gradient temperature, intramolecular dehydration occurs between adjacent peptide chains, followed by aromatization or cyclization to form a hexagonal carbon ring, and finally even a highly ordered graphite structure is generated.

It will be appreciated that the first temperature is a temperature suitable for dehydrating the silk fabric, the second temperature is a temperature at which amino and carboxyl groups in the proteins in the silk fabric undergo a cyclization reaction to form a nitrogen-oxygen doped structure, and the third temperature is a temperature suitable for carbonizing the silk fabric. It will be appreciated that the second temperature is higher than the first temperature, the third temperature is higher than the second temperature, the process is conducted at the first temperature, the second temperature and the third temperature for a suitable time, and the transition from the first temperature to the second temperature and the transition from the second temperature to the third temperature are at a suitable ramp rate.

In some embodiments of the invention, the carbonized silk fabric is prepared by: under the protection of inert gas, dehydrating the silk fabric at a first temperature of between 100 and 200 ℃ for 1 to 2 hours, then cyclizing at a second temperature of between 300 and 400 ℃ for 2 to 3 hours, and then carbonizing at a third temperature of between 950 and 1100 ℃ for 1 to 2 hours, wherein the heating rates of the silk fabric to the first temperature, the second temperature and the third temperature are independently 2 to 10 ℃/min.

The inert gas is an inert gas commonly used in chemical and chemical reactions, such as argon, neon, nitrogen or a mixture thereof. In addition, an appropriate amount of hydrogen or ammonia may be mixed into the inert gas, that is, the reaction atmosphere may be a mixed gas of the inert gas and hydrogen or ammonia. The mixed hydrogen and argon have reducibility, so that the oxygen doping content of the final carbonized silk fabric can be reduced, and the conductivity of the final carbonized silk fabric can be improved.

In the above carbonization method, when a large piece of silk fabric (for example, silk cloth) is used, it is generally cut into a square having an appropriate size and then processed. Also, it is generally preferred that the silk fabric is first sonicated with deionized water and absolute ethanol for 15-20min each, and then dried at 60 ℃ for subsequent processing.

The material of the silk fabric is not particularly limited, but pure mulberry silk or tussah silk is generally preferred, the weaving mode comprises double-crepe, plain crepe, ghost crepe and electric spinning, the thickness is 8-46 mm, and further preferably, the silk fabric is plain crepe mulberry silk fabric of 22 mm.

In some embodiments of the flexible electrode of the present invention, the electrode active material is a negative electrode active material. In the field of batteries, non-limiting examples of the anode active material include lithium metal, silicon, graphite, metal oxides, and the like. For silicon, graphite and metal oxide negative active materials, the silicon, graphite and metal oxide negative active materials can be uniformly mixed with a binder and a conductive additive in a proper amount of solvent according to a certain ratio (for example, (8-9):1:1) to obtain negative slurry, then the negative slurry is coated on a carbonized silk fabric, and the solvent is removed through vacuum drying to obtain a well-compounded flexible negative electrode.

Further, in a preferred embodiment, the negative active material is lithium metal and the flexible electrode is correspondingly a flexible lithium negative electrode. The flexible lithium negative electrode is prepared by the following method: cutting the carbonized silk fabric into carbonized silk fabric pole pieces with proper sizes, matching the carbonized silk fabric pole pieces with the lithium metal electrodes, and assembling the carbonized silk fabric pole pieces into a half-cell; quantitatively depositing lithium metal on the carbonized silk fabric pole piece under the condition of constant current; and then taking out the carbonized silk fabric pole piece deposited with the lithium metal, washing with an organic solvent, and drying to obtain the flexible lithium cathode. The drying mode can be natural drying, or low-temperature drying, or other suitable dryingAnd (4) drying. Usually, the current is set to 0.1-1mA cm^-2In the range of 1 to 20mAhcm of lithium metal^-2Within the range of (1). The organic solvent used may be, for example, dimethyl carbonate (DMC), 1, 3-Dioxolane (DOL) or Dimethoxyethane (DME). It should be noted that although an electrodeposition process is used herein to compound lithium metal with a carbonized silk fabric to prepare a flexible lithium negative electrode, other compounding processes known in the art, such as a lithium hot melt process, may also be used to prepare a flexible lithium negative electrode.

In other embodiments of the flexible electrode of the present invention, the electrode active material is a positive electrode active material. In the field of batteries, non-limiting examples of the positive active material generally include nickel cobalt manganese ternary material (NCM), Lithium Cobaltate (LCO), lithium iron phosphate (LFP), nickel cobalt aluminum ternary material (NCA), Lithium Manganate (LMO), Lithium Nickelate (LNO), and the like; in a metal-sulfur battery such as a lithium-sulfur battery, the positive electrode active material is a positive electrode active material containing elemental sulfur, such as elemental sulfur, a sulfur compound (e.g., a sulfur-carbon, sulfur-selenium, or sulfur-tellurium compound, etc.), or a polysulfide compound (e.g., Li₂S₈、Li₂S₆Etc.).

Further, in some preferred embodiments, the electrode active material is a positive electrode active material that is one or more of a nickel cobalt manganese ternary material (NCM), Lithium Cobaltate (LCO), and lithium iron phosphate (LFP). The flexible electrode is prepared by the following method: uniformly mixing the positive electrode active material, a conductive additive and a binder in a proper amount of solvent according to the mass ratio of (4-9) to (1-2) to 1 to obtain positive electrode slurry; and then uniformly coating the obtained positive electrode slurry on the carbonized silk fabric, and performing vacuum drying at the temperature of 60-80 ℃ for 12-16h to remove the solvent to obtain the flexible electrode. The conductive additive is one or more of acetylene black, Ketjen black, Super P, Super C45, carbon nanotube and graphene, and the binder is water-based binder (such as PAA, LA123 and sericin) or organic solvent-based binder (such as PVDF).

Still further, in other preferred embodiments, the electrode active material is a positive electrode active material comprising elemental sulfur, and the flexible electrode is correspondingly a flexible sulfur positive electrode. Simply, for elemental sulfur or a sulfur compound, the elemental sulfur or the sulfur compound, a conductive additive and an adhesive can be uniformly mixed in a proper amount of a solvent to obtain positive electrode slurry, then the obtained positive electrode slurry is uniformly coated on a carbonized silk fabric, and the solvent is removed by vacuum drying to obtain a flexible sulfur electrode; in the case of polysulfide, the polysulfide can be dissolved in electrolyte, and then the electrolyte is dripped on the carbonized silk fabric to obtain the flexible sulfur electrode.

In a preferred embodiment of preparing the flexible sulfur positive electrode from elemental sulfur, the flexible sulfur positive electrode is prepared by the following method: mixing and fully grinding sulfur powder and a conductive additive according to the mass ratio of (2-3) to 1, and carrying out hydrothermal reaction on the ground mixture at the temperature of 150-160 ℃ for 12-16h under the protection of inert gas to obtain a sulfur compound; fully mixing the obtained sulfur compound and the binder in a proper amount of solvent according to the mass ratio of (8-9) to 1 to obtain anode slurry; and coating the obtained positive electrode slurry on the carbonized silk fabric, and performing vacuum drying at the temperature of 60-80 ℃ for 12-16h to remove the solvent to obtain the flexible sulfur positive electrode. 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.

The solvent used in the preparation of the flexible electrode comprises an organic solvent and water, and the specific solvent is based on the used binder. For example, when an organic solvent-based binder (e.g., PVDF) is used as the binder, the solvent is an organic solvent; when an aqueous binder (for example, LA123) is used as the binder, the solvent is water.

In a second aspect the 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 located between the positive and negative electrodes, the electrode comprising a flexible electrode according to the first aspect of the invention.

As described above, the flexible electrode of the present invention includes a flexible positive electrode and a flexible negative electrode, and 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 invention, the flexible battery of the invention comprises a flexible positive electrode of the invention and other flexible negative electrodes of the battery field. In other embodiments of the invention, the flexible battery of the invention comprises the flexible negative electrode of the invention and other flexible positive electrodes of the battery field. In still further embodiments of the invention, a flexible battery of the invention comprises a flexible negative electrode of the invention and a flexible positive electrode of the invention. It should be noted that the innovation of the present invention resides in a flexible electrode and a flexible battery comprising the flexible electrode, and the separator and the electrolyte in the flexible battery may be those commonly used in the battery field or more specifically in the flexible battery field, and will not be described herein in detail.

In some preferred embodiments of the flexible battery of the invention, the negative electrode employs the flexible lithium negative electrode of the first aspect of the invention, which is accordingly a flexible lithium battery. In other preferred embodiments of the flexible battery of the invention, the positive electrode employs the flexible sulfur positive electrode of the first aspect of the invention, which is accordingly a flexible sulfur battery. In further preferred embodiments of the flexible battery of the invention, the negative electrode employs the flexible lithium negative electrode of the first aspect of the invention and the positive electrode employs the flexible sulfur positive electrode of the first aspect of the invention, the flexible battery accordingly being a flexible lithium sulfur battery.

The present invention will be further specifically described below with reference to specific examples. 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.