Titanium-based carbon nanofiber membrane, preparation method thereof, lithium-sulfur battery negative electrode and positive electrode prepared from titanium-based carbon nanofiber membrane and lithium-sulfur battery prepared from titanium-based carbon nanofiber membrane

Abstract

The invention relates to a titanium-based carbon nanofiber membrane and a preparation method thereof, which are used for preparing a negative electrode and a positive electrode of a lithium-sulfur battery and the lithium-sulfur battery. The titanium (Ti)-based carbon nanofiber membrane of the present invention comprises carbon fibers and a titanium (Ti)-based compound, the carbon fibers form a membrane shape by free interweaving, and the carbon fibers have a microstructure containing voids and are loaded with the titanium (Ti)-based compound, in addition to titanium (Ti) and carbon (C), the titanium (Ti)-based carbon nanofiber membrane is formed by free interweaving of the carbon fibers and the titanium (Ti)-based compound. The titanium (Ti)-based carbon nanofiber film may further contain at least one element selected from the group consisting of oxygen (O), nitrogen (N), phosphorus (P), sulfur (S), selenium (Se), boron (B), and tellurium (Te), and the range of the specific surface area of the titanium (Ti)-based carbon nanofiber film is 30 m2 / g or more. The negative electrode and the positive electrode for the lithium-sulfur battery and the lithium-sulfur battery use the titanium (Ti)-based carbon nanofiber membrane.

Description

Technical Field

[0001] The present invention relates to the field of lithium-sulfur batteries, and particularly to a titanium-based nanofiber carbon membrane and a preparation method thereof, a negative electrode, a positive electrode and a lithium-sulfur battery for lithium-sulfur batteries. Background Art

[0002] A lithium-sulfur battery is a battery system that uses a sulfur-based material having sulfur-sulfur (S-S) bonds as a positive electrode active material and uses lithium metal as a negative electrode active material. Sulfur, which is the main component of the positive electrode active material, is abundant in nature and can be widely found worldwide. It is non-toxic and has a low atomic weight.

[0003] Since secondary batteries are widely used in various applications, especially in scenarios with higher requirements for energy storage performance such as electric vehicles and energy storage systems. Therefore, compared with lithium-ion secondary batteries (energy storage density of about 250 Wh / kg), lithium-sulfur batteries with higher theoretical energy storage density are attracting attention. To obtain an excellent theoretical specific capacity of 1672 mAh / g and an outstanding energy density of 2600 Wh / kg, lithium-sulfur batteries have to undergo more than 16e multi-electron and solid-liquid-solid multiphase evolution, corresponding to multiple-step charge chemical transfer reactions. However, from a thermodynamic perspective, it is found that in the conversion process of , almost every stage needs to overcome a certain reaction energy barrier, especially the nucleation and decomposition of the insoluble product Li2S are the most difficult, which is the so-called rate-determining step. At the same time, the inherently low electron / ion conductivity characteristics of various sulfur species such as solid-phase S8, liquid-phase LiPSs and solid-phase Li2S2 / Li2S lead to slow chemical conversion kinetics during the solid-liquid conversion process. Therefore, the complex chemical conversion reaction and slow chemical conversion kinetics have caused the notorious "shuttle effect" and "dead sulfur" phenomena, and are also the fundamental reasons for the low effective utilization rate of active sulfur and poor cycle life.

[0004] Therefore, for the positive electrode of a lithium-sulfur battery, a strategy that is mainly explored is to rationally design and construct an electrocatalyst to improve chemical conversion kinetics through the synergistic effect of adsorption-catalysis-diffusion. Therefore, it is desirable to more reasonably and effectively construct high-performance lithium-sulfur batteries by using transition metal compounds (oxides, nitrides, borides, phosphides, sulfides, selenides, tellurides) catalysts as hosts, current collectors, and intermediate layers respectively, and use excellent electrocatalytic performance to promote efficient solid-liquid-solid chemical conversion.

[0005] Patent Document 1 provides a preparation method of a zirconium-based flexible nanofiber carbon membrane, and this zirconium-based flexible nanofiber carbon membrane can be used as a positive electrode membrane reactor. However, the performance of this positive electrode membrane reactor needs to be improved. In addition, Patent Document 1 does not pay attention to the loading of other transition metal compounds on the carbon fiber membrane.

[0006] In addition, for the negative electrode of a lithium-sulfur battery, the uneven distribution of the space charge and current density on the lithium metal surface leads to uncontrollable lithium ion (Li + ) stripping and deposition and uneven distribution of Li + , triggering the growth of lithium dendrites and inducing safety hazards. Moreover, the shuttle effect induces an irreversible corrosion side reaction at the interface between soluble LiPSs and the Li metal, damaging the solid-electrolyte interface (SEI) film, promoting the continuous consumption of the electrolyte and the lithium metal, and leading to a sharp decline in the discharge capacity and cycle stability. Therefore, tracing back to the source, the above-mentioned slow redox conversion kinetics and uneven deposition of Li + are the root causes of the above-mentioned fatal problems.

[0007] Therefore, the rational design of an advanced negative electrode structure is considered an important condition for achieving uniform Li deposition. Among them, the introduction of an artificial SEI with a high electron / ion conductivity network, a low diffusion barrier, and abundant nucleation sites has received attention.

[0008] Therefore, there is a need for a multifunctional highly active catalyst for the positive electrode that integrates excellent electronic conductivity, abundant and uniform catalytic active sites, sufficient ion transport channels, strong lithium / sulfur affinity characteristics, and for an artificial SEI that can accelerate the lithium-sulfur redox chemical conversion kinetics while synchronously regulating the lithium deposition behavior.

[0009] <Prior Art Documents>

[0010] Patent Document 1: CN 118048731 A Summary of the Invention

[0011] <Problems to be Solved by the Invention>

[0012] In view of the above situation, the object of the present invention is to provide a titanium-based nanofiber carbon membrane, which has improved lithium-sulfur chemical conversion ability, electron transfer ability, ion diffusion ability, and Li + deposition / stripping ability, that is, it can be used in the positive electrode reactor or as an artificial SEI for the negative electrode. The lithium-sulfur battery using this titanium-based nanofiber carbon membrane significantly curbs the shuttle effect and dead sulfur phenomenon, and / or the growth of lithium dendrites, and can even obtain an outstanding sulfur utilization efficiency of more than 80.0% and a high-rate specific capacity of more than 700 mAh / g at 5C.

[0013] The object of the present invention is also to provide a method for preparing a titanium-based nanofiber carbon membrane. Through this method, the titanium-based nanofiber carbon membrane can be easily prepared at low cost, and this titanium-based nanofiber carbon membrane has improved lithium-sulfur chemical conversion ability, electron transfer ability, ion diffusion ability, and Li + deposition / stripping ability, that is, it can be used in the positive electrode reactor or as an artificial SEI for the negative electrode.

[0014] It is still an object of the present invention to provide a positive electrode for a lithium-sulfur battery, which has improved lithium-sulfur chemical conversion ability, electron transfer ability, and ion diffusion ability. The lithium-sulfur battery using this positive electrode can achieve efficient synergistic adsorption-conversion-diffusion, significantly curbing the shuttle effect, dead sulfur phenomenon, etc.

[0015] It is still an object of the present invention to provide a negative electrode for a lithium-sulfur battery, which has improved electron transfer ability, ion diffusion ability, and Li + deposition / stripping ability. The lithium-sulfur battery using this negative electrode can improve the uniformity of lithium deposition and inhibit the growth of lithium dendrites.

[0016] It is still an object of the present invention to provide a lithium-sulfur battery, which significantly curbs the shuttle effect, dead sulfur phenomenon, and / or lithium dendrite growth, and can even obtain an outstanding sulfur utilization efficiency of more than 80.0% and a high-rate specific capacity of more than 700 mAh / g at 5C.

[0017] <Solution to the problem>

[0018] According to the intensive research of the inventors of the present invention, it is found that by implementing the following technical solutions, the above technical problems can be solved:

[0019] [1]. A titanium (Ti)-based nanocarbon fiber membrane, which comprises: carbon fibers and a titanium (Ti)-based compound,

[0020] The carbon fibers are formed into a membrane shape by free interweaving, and the carbon fibers have a microscopic morphology structure containing voids and the carbon fibers are loaded with the titanium (Ti)-based compound,

[0021] In addition to titanium (Ti) and carbon (C), the titanium (Ti)-based nanocarbon fiber membrane optionally further comprises at least one element selected from oxygen (O), nitrogen (N), phosphorus (P), sulfur (S), selenium (Se), boron (B), and tellurium (Te),

[0022] The specific surface area of the titanium (Ti)-based nanocarbon fiber membrane ranges from 30 m 2 / g or more.

[0023] [2]. The titanium (Ti)-based nanocarbon fiber membrane according to [1], wherein the microscopic diameter of the carbon fibers is 10 nm to 1000 nm; and / or

[0024] The microscopic morphology structure of the carbon fibers includes at least one selected from a core-shell structure, a hollow structure, a porous structure, a single-channel hollow pipe structure, a double-channel hollow pipe structure, and a multi-channel hollow pipe structure.

[0025] [3]. The titanium (Ti)-based nanocarbon fiber film according to [1] or [2], wherein the metal bonds in the titanium (Ti)-based nanocarbon fiber film include at least one selected from Ti-O bond, Ti-N bond, Ti-C bond, Ti-P bond, Ti-S bond, Ti-Se bond, Ti-B bond, and Ti-Te bond.

[0026] [4]. The titanium (Ti)-based nanocarbon fiber film according to any one of [1] to [3], wherein in the titanium (Ti)-based nanocarbon fiber film, the mass percentage content of Ti is 45 to 75%, the mass percentage content of C is 30 to 65%, the mass percentage content of O is 0 to 65%, the mass percentage content of N is 0 to 65%, the mass percentage content of Se is 0 to 60%, the mass percentage content of S is 0 to 65%, the mass percentage content of B is 0 to 65%, and the mass percentage content of Te is 0 to 65%.

[0027] [5]. The titanium (Ti)-based nanocarbon fiber film according to any one of [1] to [4], wherein the specific surface area of the titanium (Ti)-based nanocarbon fiber film ranges from 60 to 1000 m 2 / g; and / or

[0028] The titanium (Ti)-based nanocarbon fiber film has a micro-mesoporous structure with a pore size range of 2 nm to 100 nm.

[0029] [6]. A method for preparing a titanium (Ti)-based nanocarbon fiber film, the method comprising:

[0030] (1) Preparing an electrospinning outer shaft solution, the electrospinning outer shaft solution comprising a titanium (Ti) source, a polymer, and a solvent A;

[0031] (2) Preparing an electrospinning inner shaft solution, the electrospinning inner shaft solution comprising a sacrificial agent and a solvent B;

[0032] (3) Using the electrospinning outer shaft solution and the electrospinning inner shaft solution, performing coaxial electrospinning under a voltage condition of negative voltage ≤ -0.1 KV and positive voltage ≥ 5 KV to obtain a precursor fiber film,

[0033] (4) Carbonizing the precursor fiber film in a carbonizing atmosphere, the carbonizing atmosphere comprising at least one selected from inert gas, hydrogen, and an atmosphere containing other elements, and the other elements being at least one selected from carbon (C), phosphorus (P), sulfur (S), selenium (Se), boron (B), and tellurium (Te).

[0034] [7]. The preparation method according to [6], wherein the titanium (Ti) source comprises at least one selected from tetrabutyl titanate (C 16 H 36O4Ti), titanium tetrachloride (TiCl4), titanium oxalate (Ti(C2O4)2), tetramethanol titanate (C4H 12 O4Ti2), sodium metatitanate (Na2Ti3O7), or at least one of them,

[0035] The polymer includes at least one selected from polyacrylonitrile (PAN), polyvinylpyrrolidone (PVP), and polyvinyl alcohol (PEO),

[0036] The sacrificial agent includes at least one selected from polyvinylpyrrolidone (PVP), polystyrene (PS), polymethyl methacrylate (PMMA), and paraffin wax.

[0037] Each of the solvent A and the solvent B includes at least one selected from N-methylpyrrolidone (NMP) and N,N-dimethylformamide (DMF).

[0038] [8]. The preparation method according to [6] or [7], wherein in the electrospinning outer-axis solution, the dosage ratio of the titanium (Ti) source, the polymer, and the solvent A satisfies: the titanium (Ti) source: the polymer: the solvent A = 0.1 g to 20 g: 0.2 g to 6 g: 4 ml to 20 ml;

[0039] In the electrospinning inner-axis solution, the dosage ratio of the sacrificial agent and the solvent B satisfies: the sacrificial agent: the solvent B = 0.1 g to 3.0 g: 1 ml to 20 ml.

[0040] [9]. The preparation method according to any one of [6] to [8], wherein the carbonization atmosphere is nitrogen, argon, a mixture of hydrogen and argon, a mixture of hydrogen, argon and a C-containing atmosphere, a mixture of hydrogen, argon and a Se-containing atmosphere, a mixture of hydrogen, argon and a Te-containing atmosphere, a mixture of hydrogen, argon and an S-containing atmosphere, or a mixture of hydrogen, argon and a B-containing atmosphere;

[0041] During the carbonization, the carbonization temperature is 200 °C to 1800 °C, and / or; the carbonization time is 0.5 to 24 h, and / or; the heating rate to the carbonization temperature is 0.2 °C / min to 10 °C / min.

[0042]

[10] . A positive electrode for a lithium-sulfur battery, the positive electrode includes a membrane reactor, and the membrane reactor is made using: the titanium (Ti)-based nanofiber membrane according to any one of [1] to [5], or the titanium (Ti)-based nanofiber membrane prepared by the method according to any one of [6] to [9].

[0043]

[11] . A negative electrode for a lithium-sulfur battery, the negative electrode including an artificial SEI for the negative electrode, and the artificial SEI for the negative electrode is made using the following: a titanium (Ti)-based nanofiber membrane according to any one of [1] to [5], or a titanium (Ti)-based nanofiber membrane prepared by the method according to any one of [6] to [9].

[0044]

[12] . A lithium-sulfur battery, characterized in that the lithium-sulfur battery includes a positive electrode, a negative electrode, a separator between the positive electrode and the negative electrode, and an electrolyte;

[0045] The positive electrode is the positive electrode according to

[10] , and / or

[0046] The negative electrode is the negative electrode according to

[11] .

[0047] <Effects of the Invention>

[0048] In the present invention, through the above technical solution, the following technical effects are achieved.

[0049] Due to having the above specific composition and structure, a large number of uniformly loaded Ti ions with different valence states exist in the titanium-based nanofiber membrane of the present invention, supplying sufficient electrocatalytic active sites and sulfurophilic / lithiophilic active sites. The titanium-based nanofiber membrane of the present invention has excellent electronic conductivity due to its carbon fiber skeleton. Moreover, the carbon fibers in the titanium-based nanofiber membrane of the present invention have a microstructure containing voids (in particular, a rich tubular porous structure), and the titanium-based nanofiber membrane exhibits a large specific surface area, thereby providing sufficient ion transport channels.

[0050] More specifically, for the scenario of the positive electrode membrane reactor, the strong electrocatalytic activity of the Ti-based compound promotes the high-speed chemical conversion of solid-phase S8 - liquid-phase LiPSs - solid-phase Li2S - solid-phase S8, realizing the efficient synergistic effect of adsorption - conversion - diffusion. The excellent electronic conductivity provides a strong driving force for the electron transfer between the membrane reactor and polysulfide species. The above microstructure containing voids and large specific surface area enable the high-speed shuttle of Li + ions.

[0051] For the scenario of the negative electrode artificial SEI, the use of rich electrochemically active sites such as oxygen (O), nitrogen (N), fluorine (F), phosphorus (P), sulfur (S), selenium (Se), boron (B), and tellurium (Te) can induce the uniform nucleation growth of lithium ions, and the microstructure containing voids can contribute to the uniform deposition of Li + ions. The above strong lithiophilic property and large specific surface area can reduce the nucleation overpotential and local current density, promoting more uniform lithium deposition.

[0052] Therefore, the titanium-based nanofiber carbon membrane of the present invention can be used in the membrane reactor included in the positive electrode of a lithium-sulfur battery and can also be used in the artificial SEI included in the negative electrode of a lithium-sulfur battery. Furthermore, the positive electrode and the negative electrode of the lithium-sulfur battery of the present invention each exhibit improved performance.

[0053] In a lithium-sulfur battery using the titanium-based nanofiber carbon membrane of the present invention in the positive electrode and / or the negative electrode, the shuttle effect, the dead sulfur phenomenon, and / or the growth of lithium dendrites are significantly suppressed, and an outstanding sulfur utilization efficiency of more than 80.0% and a high rate specific capacity of more than 700 mAh / g at 5C can even be obtained.

[0054] In particular, when the positive electrode and the negative electrode of the present invention are used simultaneously, that is, when the titanium (Ti)-based nanofiber carbon membrane of the present invention is used as both the positive electrode membrane reactor and the negative electrode artificial SEI in a lithium-sulfur battery, a superior areal capacity of at least 10 mAh / cm 2 can be achieved, which is significantly better than the areal capacity of 4 mAh / cm 2 of a conventional lithium-ion (LIBs) battery. Description of the Drawings

[0055] Figure 1 TEM test diagram of the multifunctional titanium (Ti)-based nanofiber carbon membrane prepared in Example 1.

[0056] Figure 2 XRD test diagram of the multifunctional titanium (Ti)-based nanofiber carbon membrane prepared in Example 2.

[0057] Figure 3 Cyclic voltammetry test curve of the lithium-sulfur battery constructed with the multifunctional titanium (Ti)-based nanofiber carbon membrane prepared in Example 3 as the positive electrode membrane reactor.

[0058] Figure 4 Lithium negative electrode cyclic stability test results of the lithium-sulfur battery constructed with the multifunctional titanium (Ti)-based nanofiber carbon membrane prepared in Example 4 as the negative electrode artificial SEI.

[0059] Figure 5 Rate test curve of the lithium-sulfur battery constructed with the multifunctional titanium (Ti)-based nanofiber carbon membrane prepared in Example 5 as the positive electrode membrane reactor and the negative electrode artificial SEI.

[0060] Figure 6 200-cycle test curve of the lithium-sulfur battery constructed with the multifunctional titanium (Ti)-based nanofiber carbon membrane prepared in Example 6 as the positive electrode membrane reactor and the negative electrode artificial SEI.

[0061] Figure 7 Charge-discharge curve of the lithium-sulfur battery constructed with the multifunctional titanium (Ti)-based nanofiber carbon membrane prepared in Example 7 as the positive electrode membrane reactor and the negative electrode artificial SEI.

[0062] Figure 8 Electrochemical impedance test curve of a lithium-sulfur battery constructed with the multifunctional titanium (Ti)-based nanofiber carbon membrane prepared in Example 8 as the positive electrode membrane reactor.

[0063] Figure 9 Nitrogen adsorption specific surface area test results of the multifunctional titanium (Ti)-based nanofiber carbon membrane prepared in Comparative Example 1.

[0064] Figure 10 Lithium negative electrode cycle stability test results of a lithium-sulfur battery constructed with the multifunctional titanium (Ti)-based nanofiber carbon membrane prepared in Comparative Example 1 as the negative electrode artificial SEI.

[0065] Figure 11 Rate test curve of a lithium-sulfur battery constructed with the multifunctional titanium (Ti)-based nanofiber carbon membrane prepared in Example 2 as the positive electrode membrane reactor and the negative electrode artificial SEI.

[0066] Figure 12 Rate test curve of a lithium-sulfur battery constructed with the multifunctional titanium (Ti)-based nanofiber carbon membrane prepared in Example 12 as the positive electrode membrane reactor and the negative electrode artificial SEI. Detailed implementation manners

[0067] The various exemplary embodiments, features, and aspects of the present invention will be described in detail below. The special term "exemplary" here means "serving as an example, embodiment, or illustration". Any embodiment described as "exemplary" here does not necessarily have to be construed as superior to or better than other embodiments.

[0068] In addition, in order to better illustrate the present invention, numerous specific details are given in the following detailed implementation manners. Those skilled in the art should understand that the present invention can also be implemented without certain specific details. In other instances, methods, means, equipment, and steps well-known to those skilled in the art are not described in detail in order to highlight the gist of the present invention.

[0069] Unless otherwise stated, the units used in this specification are all international standard units, and the numerical values and numerical ranges appearing in the present invention should be understood to include the inevitable systematic errors in industrial production.

[0070] In this specification, the meaning expressed by using "may" includes both meanings of performing a certain process and not performing a certain process.

[0071] In this specification, the "some specific / preferred embodiments", "other specific / preferred embodiments", "embodiments", etc. mentioned refer to the specific elements (e.g., features, structures, properties, and / or characteristics) related to such embodiments, which are included in at least one of the embodiments described herein, and may or may not be present in other embodiments. Additionally, it should be understood that the elements can be combined in various embodiments in any suitable manner.

[0072] In this specification, the numerical range represented by "numerical value A to numerical value B" refers to the range including the endpoint numerical values A and B. In this specification, the numerical range represented by "above" and "below" refers to the range including the endpoint numerical values. In this specification, the numerical range represented by "greater than" and "less than" refers to the range not including the endpoint numerical values.

[0073] In this specification, "optional" or "optionally" means that the subsequent described event or situation may or may not occur, and this description includes the situation where the event occurs and the situation where the event does not occur.

[0074] <Titanium (Ti)-based nanocarbon fiber membrane>

[0075] The titanium (Ti)-based nanocarbon fiber membrane of the present invention includes: carbon fibers and a titanium (Ti)-based compound. The carbon fibers form a membrane shape by freely intertwining, and the carbon fibers have a microscopic morphological structure containing voids and the carbon fibers are loaded with the titanium (Ti)-based compound. In the present invention, the titanium (Ti)-based compound can serve as a catalytic unit.

[0076] In addition, there is no particular limitation on the composition and structure of the titanium-based compound, and the Ti in the titanium-based compound can exhibit the valence states it can exhibit, including divalent, trivalent, tetravalent, etc.

[0077] The titanium (Ti)-based nanocarbon fiber membrane also optionally contains at least one element selected from oxygen (O), nitrogen (N), phosphorus (P), sulfur (S), selenium (Se), boron (B), and tellurium (Te).

[0078] In the present invention, the term "the carbon fibers form a membrane shape by freely intertwining" means that the product formed by randomly and freely intertwining the carbon fibers exhibits a macroscopic membrane morphology, that is, it can be confirmed with the naked eye that the product as a whole presents a membrane morphology. In the present invention, the carbon fibers forming the membrane are loaded with a titanium (Ti)-based compound, and there is no particular limitation on the loading position. For example, it can be on the surface of the carbon fibers or loaded inside the carbon fibers (e.g., embedded or entrapped in the carbon fibers). Preferably, at least a part of the titanium (Ti)-based compound is exposed on the surface of the carbon fibers.

[0079] In the present invention, there is no particular limitation on the size of the carbon fiber itself. In some preferred embodiments, the micro-diameter of the carbon fiber (i.e., the fiber diameter of the carbon fiber) is preferably 10 nm to 1000 nm, more preferably 50 nm to 500 nm.

[0080] In the present invention, there is no particular limitation on the micro-morphology structure of the carbon fiber itself, as long as it contains voids. In some preferred embodiments, the micro-morphology structure of the carbon fiber includes at least one selected from the group consisting of core-shell structure, hollowed-out structure, porous structure, single-channel hollow pipe structure, double-channel hollow pipe structure, and multi-channel hollow pipe structure.

[0081] In addition, in some specific embodiments, the carbon fibers of different diameter sizes form a film shape by freely intertwining. In other specific embodiments, the carbon fibers of different micro-morphology structures form a film shape by freely intertwining.

[0082] In addition, the specific surface area of the titanium (Ti)-based carbon nanofiber film ranges from 30 m 2 / g or more. In the present invention, there is no particular limitation on the upper limit of the specific surface area of the titanium (Ti)-based carbon nanofiber film, and generally, the larger the better is expected. However, in some preferred embodiments, from the perspective of more easily obtaining the titanium (Ti)-based carbon nanofiber film of the present invention, the specific surface area of the titanium (Ti)-based carbon nanofiber film of the present invention preferably ranges from 60 to 1000 m 2 / g, more preferably from 70 to 800 m 2 / g, and further preferably from 200 to 600 m 2 / g. In the present invention, the specific surface area is the specific surface area measured by the nitrogen adsorption method.

[0083] In some other preferred embodiments, from the overall view of the film, the titanium (Ti)-based carbon nanofiber film of the present invention preferably has a micro-mesoporous structure, and more preferably, the titanium (Ti)-based carbon nanofiber film has a micro-mesoporous structure with a pore size range of 2 nm to 100 nm.

[0084] In addition, there is no particular limitation on the thickness of the titanium (Ti)-based carbon nanofiber film of the present invention, which can be 1 μm to 5000 μm, preferably 5 μm to 3000 μm, more preferably 20 μm to 2500 μm, and further preferably 50 μm to 1500 μm.

[0085] As described above, in order to ensure that the present invention achieves the desired technical effects, in addition to carbon (C) and titanium (Ti), the titanium (Ti)-based nanocarbon fiber film optionally further contains at least one element selected from oxygen (O), nitrogen (N), phosphorus (P), sulfur (S), selenium (Se), boron (B), and tellurium (Te) (hereinafter sometimes simply referred to as other elements). In some preferred embodiments, the other element is at least one element selected from nitrogen (N), oxygen (O), sulfur (S), selenium (Se), boron (B), and tellurium (Te).

[0086] In some preferred embodiments, from the perspective of more easily achieving the desired effects of the present invention, the titanium (Ti)-based nanocarbon fiber film contains the above-mentioned other elements.

[0087] In some preferred embodiments, the metal bonds in the titanium (Ti)-based nanocarbon fiber film preferably include at least one selected from Ti-O bond, Ti-N bond, Ti-C bond, Ti-P bond, Ti-S bond, Ti-Se bond, Ti-B bond, and Ti-Te bond, and more preferably contain at least one selected from Ti-O bond, Ti-N bond, Ti-S bond, Ti-Se bond, Ti-B bond, and Ti-Te bond. In this case, the role of the titanium (Ti)-based compound as a catalytic unit can be better exerted.

[0088] In addition, for example, in addition to the C═C bond, the titanium (Ti)-based nanocarbon fiber film may further contain other non-metal bonds, such as C-O bond, N-O bond, etc.

[0089] In some preferred embodiments, from the perspective of more easily achieving the desired technical effects of the present invention, the titanium (Ti)-based compound preferably includes at least one selected from titanium oxides, titanium nitrides, titanium carbides, titanium phosphides, titanium sulfides, titanium selenides, titanium borides, and titanium tellurides, and more preferably contains at least one selected from titanium monoxide (TiO), tetra titanium heptoxide (Ti4O7), tri titanium pentoxide (Ti3O5), titanium dioxide (TiO2), titanium carbide (TiC), titanium nitride (TiN), titanium selenide (TiSe2), titanium telluride (TiTe2), titanium sulfide (TiS2), and titanium diboride (TiB2).

[0090] In the present invention, there is no particular limitation on the content of each element in the titanium (Ti)-based nanocarbon fiber film, and it can be appropriately adjusted as needed.

[0091] In some preferred embodiments, from the perspective of better achieving the desired effects of the present invention and reducing costs, in the titanium (Ti)-based nanocarbon fiber film, the mass percentage content of Ti is preferably 45-75%, more preferably 50-72%, and further preferably 52-70%.

[0092] In some preferred embodiments, from the perspective of better achieving the desired effects of the present invention and reducing costs, in the titanium (Ti)-based nanocarbon fiber membrane, the mass percentage content of C is preferably 30 to 65%, more preferably 35 to 60%, and further preferably 38 to 58%.

[0093] In some preferred embodiments, the mass percentage content of O is preferably 0 to 65%. In some specific embodiments, when O is included, the mass percentage content of O is preferably 5 to 65%, more preferably 7 to 60%.

[0094] In some preferred embodiments, the mass percentage content of N is preferably 0 to 65%. In some specific embodiments, when N is included, the mass percentage content of N is preferably 3 to 65%, more preferably 5 to 60%.

[0095] In some preferred embodiments, the mass percentage content of Se is preferably 0 to 60%. In some specific embodiments, when Se is included, the mass percentage content of Se is preferably 3 to 60%, more preferably 5 to 55%.

[0096] In some preferred embodiments, the mass percentage content of S is preferably 0 to 65%. In some specific embodiments, when S is included, the mass percentage content of S is preferably 3 to 65%, more preferably 5 to 60%.

[0097] In some preferred embodiments, the mass percentage content of B is preferably 0 to 65%. In some specific embodiments, when B is included, the mass percentage content of B is preferably 3 to 65%, more preferably 5 to 60%.

[0098] In some preferred embodiments, the mass percentage content of Te is preferably 0 to 65%. In some specific embodiments, when Te is included, the mass percentage content of Te is preferably 3 to 65%, more preferably 5 to 60%.

[0099] In the present invention, there is no particular limitation on the preparation method of the titanium (Ti)-based nanocarbon fiber membrane, and various methods known in the art can be adopted. For example, first form a nanocarbon fiber membrane, and then load a titanium (Ti)-based compound therein by a conventional method in the art, or use a raw material including a titanium (Ti) source to prepare a nanocarbon fiber membrane, etc. In some preferred embodiments, the titanium (Ti)-based nanocarbon fiber membrane of the present invention is obtained by the method described hereinafter in the present invention.

[0100] <Preparation Method of Titanium (Ti)-Based Nanocarbon Fiber Membrane>

[0101] The method for preparing the titanium (Ti)-based nanofiber carbon film of the present invention comprises: (1) preparing an electrospinning outer-axis solution, which contains a titanium (Ti) source, a high molecular polymer, and a solvent A; (2) preparing an electrospinning inner-axis solution, which contains a sacrificial agent and a solvent B; (3) using the electrospinning outer-axis solution and the electrospinning inner-axis solution to perform coaxial electrospinning under a voltage condition where the negative voltage ≤ -0.1 KV and the positive voltage ≥ 5 KV to obtain a precursor fiber film; (4) carbonizing the precursor fiber film in a carbonizing atmosphere, which contains an inert gas and optionally other elements, and the other elements are at least one selected from carbon (C), phosphorus (P), sulfur (S), selenium (Se), boron (B), and tellurium (Te).

[0102] In step (1), there is no particular limitation on the titanium (Ti) source. Preferably, it includes an organic titanium (Ti) source and / or an inorganic titanium (Ti) source, and more preferably, it is an organic or inorganic salt containing titanium. Examples of the organic salt containing titanium include, but are not limited to, titanium tetraols such as titanium tetramethanolate and tetrabutyl titanate (general formula: Ti(OR)4, where R can be an alkyl group, preferably a C1-C12 alkyl group), and titanium carboxylates with more than one carboxyl group such as titanium acetate and titanium oxalate (for example, preferably titanium dicarboxylate). Examples of the inorganic salt containing titanium include, but are not limited to, titanium halides such as titanium tetrachloride, metal metatitanates such as sodium metatitanate (for example, alkali metal or alkaline earth metal salts), and metal titanates such as sodium titanate (for example, alkali metal or alkaline earth metal salts), etc.

[0103] In some preferred embodiments, from the perspective of more easily obtaining the titanium (Ti)-based nanofiber carbon film of the present invention, the titanium (Ti) source contains at least one selected from 16 H 36 butyl titanate (C 12 O4Ti), titanium tetrachloride (TiCl4), titanium oxalate (Ti(C2O4)2), titanium tetramethanolate (C4H

[0104] In step (1), there is no particular limitation on the high molecular polymer. Those that can usually be used as precursor fiber films in the art can be adopted. For example, acrylonitrile-based copolymers such as homopolymers and copolymers of acrylonitrile, vinyl pyrrolidone-based polymers such as homopolymers and copolymers of vinyl pyrrolidone-based monomers, vinyl alcohol-based polymers such as homopolymers and copolymers of vinyl alcohol-based monomers, (meth)acrylate-based polymers, pitches such as petroleum pitch and coal pitch, cellulose-based compounds, etc. In some preferred embodiments, the high molecular polymer preferably contains at least one selected from acrylonitrile-based copolymers, pyrrolidone-based polymers, and vinyl alcohol-based polymers, and more preferably contains at least one selected from polyacrylonitrile (PAN: [C3H3N] n)、Polyvinylpyrrolidone (PVP: [C6H9NO] n )、at least one of polyvinyl alcohol (PEO: [C2H4O]n).

[0105] In step (1), there is no particular limitation on solvent A, and those that can dissolve the above-mentioned polymer of the present invention and are commonly known in the art can be used. For example, fluorinated alcohols such as trifluoroethanol and hexafluoroisopropanol, fluorinated carboxylic acids such as trifluoroacetic acid, ketones such as cyclohexanone, acetone, and butanone, ethers such as tetrahydrofuran, fluorinated alkanes such as chloroform, pyrrolidones such as pyrrolidone and N-methylpyrrolidone (NMP), and amides such as N,N-dimethylformamide (DMF), N-methylformamide, and N,N-diethylformamide. In some preferred embodiments, solvent A preferably contains at least one selected from pyrrolidone solvents and amide solvents, and more preferably contains at least one selected from N-methylpyrrolidone (NMP) and N,N-dimethylformamide (DMF).

[0106] In step (1), there is no particular limitation on the proportion of each component in the electrospinning outer shaft solution, and it can be appropriately adjusted according to specific needs such as actual equipment and raw materials. In some preferred embodiments, in the electrospinning outer shaft solution, the dosage ratio of the titanium (Ti) source, polymer, and solvent A preferably satisfies: titanium (Ti) source (in terms of mass conversion): polymer (in terms of mass conversion): solvent A (in terms of volume conversion) = 0.1 g to 20 g: 0.2 g to 6 g: 4 ml to 20 ml, and more preferably satisfies: titanium (Ti) source: polymer: solvent A = 1 g to 8 g: 0.8 g to 4 g: 9 ml to 15 ml.

[0107] In addition, in step (1), in the electrospinning outer shaft solution, in addition to the titanium (Ti) source, polymer, and solvent A, other components can also be included as needed, such as pore formers, other metal sources (such as zirconium sources, etc.), surfactants, catalysts, etc. There is no particular limitation on the content of these other components. For example, it is 10% by mass or less, or 5% by mass or less relative to 100% by mass of the polymer.

[0108] In step (1), the preparation of the electrospinning outer shaft solution can be carried out by various methods known in the art. The temperature for mixing the titanium (Ti) source, polymer, and solvent A is preferably room temperature (10 - 40 °C), the time is preferably 0.5 - 20 h, and more preferably 1 - 15 h; the mixing of the titanium (Ti) source, polymer, and solvent A is preferably carried out under stirring conditions.

[0109] In step (2), there is no particular limitation on the sacrificial agent, and it preferably includes polyvinylpyrrolidone (PVP: [C6H9NO] n) Polystyrene (PS: [C8H8] n ) Polymethyl methacrylate (PMMA: [C5O2H8] n ) at least one of paraffin wax.

[0110] In step (2), there is no particular limitation on solvent B, and those that can dissolve the above-mentioned high molecular polymers of the present invention and are commonly known in the art can be used. For example, fluorinated alcohols such as trifluoroethanol and hexafluoroisopropanol, fluorinated carboxylic acids such as trifluoroacetic acid, ketones such as cyclohexanone, acetone, and butanone, ethers such as tetrahydrofuran, fluorinated alkanes such as chloroform, pyrrolidone solvents such as pyrrolidone and N-methylpyrrolidone (NMP), and amide solvents such as N,N-dimethylformamide (DMF), N-methylformamide, and N,N-diethylformamide. In some preferred embodiments, solvent B preferably contains at least one selected from pyrrolidone solvents and amide solvents, and more preferably contains at least one selected from N-methylpyrrolidone (NMP) and N,N-dimethylformamide (DMF).

[0111] In step (2), there is no particular limitation on the proportion of each component in the electrospinning inner shaft solution, and it can be appropriately adjusted according to specific needs such as actual equipment and raw materials. In some preferred embodiments, in the electrospinning inner shaft solution, the dosage ratio of the sacrificial agent to solvent B satisfies: sacrificial agent: solvent B = 0.1 g to 3.0 g: 1 ml to 20 ml, and more preferably satisfies: sacrificial agent: solvent B = 0.8 g to 2 g: 8 ml to 12 ml.

[0112] In step (2), the electrospinning inner shaft solution can be prepared by various methods known in the art. The temperature for mixing the sacrificial agent and solvent B is preferably room temperature (10 - 40 °C), the time is preferably 0.5 - 20 h, and more preferably 1 - 15 h; the mixing of the sacrificial agent and solvent B is preferably carried out under stirring conditions.

[0113] In step (3), the electrospinning method is used to obtain the precursor fiber membrane. The principle of electrospinning is that during the electrospinning process, a high voltage is applied to the polymer liquid to introduce charges into the liquid. When the charges in the liquid accumulate to a certain amount, the liquid will form a Taylor cone at the nozzle, and under the action of the external electric field force, the surface tension is overcome to form a liquid jet. Then, under the combined action of electrostatic repulsion, Coulomb force, and surface tension, the polymer jet moves along an irregular spiral trajectory. The jet is stretched by traction in a very short time, and as the solvent volatilizes or heat dissipates, the polymer jet solidifies to form micro / nano fibers.

[0114] It is a new method developed on the basis of traditional electrospinning technology, which can prepare continuous nanomaterials with a void structure. During electrospinning, the inner and outer axis spinning solutions are respectively loaded into two different syringes and connected to a spinneret system composed of two coaxial needles with different inner diameters. Under the action of a high-voltage electric field, the outer axis solution of electrospinning flows out and converges with the inner axis solution of electrospinning, and the two liquids will not mix together before solidification.

[0115] In step (3), the above-mentioned outer axis solution of electrospinning and the above-mentioned inner axis solution of electrospinning are used. More specifically, the above-mentioned outer axis solution of electrospinning and the above-mentioned inner axis solution of electrospinning are respectively added to the inner cavity and the outer cavity of a coaxial electrospinning device, and coaxial electrospinning is carried out under the voltage condition of negative voltage ≤ -0.1 KV and positive voltage ≥ 5 KV to obtain a precursor fiber membrane. When the above voltage range is adopted, the preparation of the precursor fiber membrane can be ensured.

[0116] In some preferred embodiments, the voltage condition of electrospinning is preferably -10 KV ≤ negative voltage ≤ -0.1 KV, 30 KV ≥ positive voltage ≥ 5 KV, and more preferably -5 KV ≤ negative voltage ≤ -0.5 KV, 20 KV ≥ positive voltage ≥ 10 KV.

[0117] In step (3), the present invention has no special requirements for the coaxial electrospinning method, and it can be a common coaxial electrospinning method in the art. In addition, except for the voltage, there are no special restrictions on other process parameters of coaxial electrospinning. By controlling the process parameters, nanofiber membranes with different sizes, morphologies and structures can be prepared.

[0118] In addition, in step (3), in some specific embodiments, the spinning temperature can be the ambient temperature, such as 10 - 60 °C, such as 15 - 40 °C. In some specific embodiments, the spinning humidity can be below 80% RH, such as below 60% RH, such as below 40% RH. In some specific embodiments, the product collection distance can be 5 cm - 20 cm. In some specific embodiments, the injection rates of the two solutions can independently be 0.4 - 1 ml / h.

[0119] In step (4), the precursor fiber membrane is carbonized in a carbonization atmosphere to obtain the titanium (Ti)-based carbon nanofiber membrane of the present invention.

[0120] In step (4), as described above, the carbonization atmosphere includes at least one selected from inert gases, hydrogen and atmospheres containing other elements, and the other elements are at least one selected from carbon (C), phosphorus (P), sulfur (S), selenium (Se), boron (B) and tellurium (Te), and more preferably at least one selected from sulfur (S), selenium (Se), boron (B) and tellurium (Te).

[0121] In the present invention, there is no particular limitation on the type of inert gas, including but not limited to nitrogen, helium, argon, etc.

[0122] In step (4), according to the type of the desired titanium (Ti)-based compound, the composition of a suitable carbonization atmosphere is selected. In some preferred embodiments, the carbonization atmosphere is nitrogen, argon, a mixture of hydrogen and argon, a mixture of hydrogen, argon and a C-containing atmosphere, a mixture of hydrogen, argon and a Se-containing atmosphere, a mixture of hydrogen, argon and a Te-containing atmosphere, a mixture of hydrogen, argon and an S-containing atmosphere, or a mixture of hydrogen, argon and a B-containing atmosphere.

[0123] In the present invention, preferably, the C-containing atmosphere is a gas containing carbon alkanes such as methane, ethane, etc. Preferably, the Se-containing atmosphere is a vapor obtained by heating Se powder. Preferably, the Te-containing atmosphere is a vapor obtained by heating Te powder. Preferably, the S-containing atmosphere is a vapor obtained by heating S powder. Preferably, the B-containing atmosphere is a vapor obtained by heating a boron-containing compound (such as but not limited to: tetraborates such as sodium tetraborate (Na2B4O7), borates such as sodium borate (Na3BO3), metaborates such as sodium metaborate (NaBO2), perborates such as sodium perborate (NaBO3), etc.).

[0124] In addition, in the present invention, there is no particular limitation on the content of other elements in each atmosphere. For example, the content of other elements can be saturated, that is, the mass ratio of other elements (especially Se, Te) to the precursor film to be carbonized is greater than 1. When there are two or more other elements, the content of other elements is the total content of each element.

[0125] In step (4), during carbonization, as long as carbonization can be carried out, there is no particular limitation on the carbonization temperature. In some preferred embodiments, the carbonization temperature is preferably 200°C to 1800°C, more preferably 220°C to 1400°C.

[0126] In step (4), during carbonization, as long as carbonization can be carried out, there is no particular limitation on the carbonization time. In some preferred embodiments, the carbonization time is preferably 0.5 to 24 h, more preferably 1 to 15 h.

[0127] In step (4), during carbonization, there is no particular limitation on the heating rate for raising the temperature to the carbonization temperature. In some preferred embodiments, the heating rate for raising the temperature to the carbonization temperature is preferably 0.2°C / min to 10°C / min.

[0128] In addition to the above steps (1) to (4), the preparation method of the present invention may optionally include other steps known in the art for preparing carbon fiber membranes, such as oxidation treatment of the precursor membrane.

[0129] In some particularly specific embodiments, the method for preparing a titanium (Ti)-based carbon nanofiber film of the present invention comprises the following steps:

[0130] (1) Titanium (Ti)-containing inorganic / organic salts, high molecular weight polymers, and solvents are selected and mixed in appropriate proportions and stirred for several hours to form an electrospinning outer axis solution. Similarly, a sacrificial agent and solvent are mixed in appropriate proportions and stirred for several hours to obtain an electrospinning inner axis solution. All operations are completed at room temperature.

[0131] (2) According to the requirements of the microstructure of nanocarbon fibers, different inner axis solutions and coaxial electrospinning needles are selected, combined with the outer axis solution, and the electrospinning products are collected at a high voltage of -10KV to 30KV;

[0132] (3) Select a suitable carbonization atmosphere according to the requirements of the Ti compound, heat the temperature to 200°C~1700°C (473K~1973K) at a heating rate of 0.2°C / min~10°C / min (273.2K~283K), and carbonize for 1~10h; after cooling, a nanocarbon fiber membrane with titanium (Ti)-based compounds as catalytic units is obtained.

[0133] <Positive electrode for lithium-sulfur batteries>

[0134] The positive electrode for lithium-sulfur batteries of the present invention comprises a membrane reactor, which is made using the titanium (Ti)-based nanocarbon fiber membrane of the present invention or the titanium (Ti)-based nanocarbon fiber membrane prepared by the method of the present invention.

[0135] The positive electrode for the lithium-sulfur battery of the present invention may include one or more titanium (Ti)-based carbon nanofiber films, for example, which may be stacked with electrode material layers in any structure.

[0136] The electrode material layer included in the lithium-sulfur battery positive electrode of the present invention includes an electrode material, a binder, and optionally a conductive material, etc. In addition, the lithium-sulfur battery positive electrode of the present invention may further include a positive electrode current collector.

[0137] The electrode material in the positive electrode for the lithium-sulfur battery of the present invention is a sulfur-containing material, which can be elemental sulfur, a sulfur-containing composite material such as a carbon-sulfur composite material, or a mixture thereof.

[0138] The binder is a component that helps the binding between electrode materials, between electrode materials and conductive materials, and the binding to the current collector, and can be, for example, but not limited to, at least one selected from the following: polyvinylidene fluoride (PVdF), polyvinylidene fluoride - hexafluoropropylene copolymer (PVdF / HFP), polyvinyl acetate, polyvinyl alcohol, polyvinyl ether, polyethylene, poly(ethylene oxide), alkylated poly(ethylene oxide), polypropylene, poly(methyl)acrylate methyl ester, poly(methyl)acrylate ethyl ester, polytetrafluoroethylene (PTFE), polyvinyl chloride, polyacrylonitrile, polyvinyl pyridine, polyvinyl pyrrolidone, styrene - butadiene rubber, nitrile rubber, ethylene - propylene - diene monomer (EPDM) rubber, sulfonated EPDM rubber, styrene - butene rubber, fluororubber, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, and their mixtures, etc.

[0139] There is no particular limitation on the conductive material contained in the positive electrode, as long as the conductive material does not cause side reactions in the internal environment of the battery and has excellent electrical conductivity without causing chemical changes in the battery. As the conductive material, at least one selected from the following can be used: graphite or conductive carbon, carbon nanotubes, conductive fibers such as carbon fibers and metal fibers, fluorocarbons, metal powders such as aluminum powder and nickel powder, conductive whiskers such as zinc oxide and potassium titanate, conductive oxides such as titanium oxide, conductive polymers, etc.

[0140] The positive electrode current collector can be, but not necessarily limited to: platinum (Pt), gold (Au), palladium (Pd), iridium (Ir), silver (Ag), ruthenium (Ru), nickel (Ni), stainless steel (STS), aluminum (Al), molybdenum (Mo), chromium (Cr), carbon (C), titanium (Ti), tungsten (W), ITO (In - doped SnO2), FTO (F - doped SnO2), or their alloys; or aluminum (Al) or stainless steel whose surface is treated with carbon (C), nickel (Ni), titanium (Ti), or silver (Ag), etc.

[0141] The content of each of the above - mentioned components in the electrode material layer can be the amount commonly used in the art. In addition, the electrode material layer can be obtained by methods known in the art. For example, the electrode material, binder, optional conductive material, etc. are dispersed and mixed in a suitable dispersion medium (organic solvent or water) to form a slurry, and the slurry can be coated on the positive electrode current collector, and then dried and rolled to prepare the positive electrode.

[0142] In addition, the positive electrode for the lithium - sulfur battery of the present invention can further contain other components known in the art, such as a protective layer, etc.

[0143] <Negative electrode for lithium - sulfur battery>

[0144] The negative electrode for the lithium-sulfur battery of the present invention includes an artificial SEI for the negative electrode, and the artificial SEI for the negative electrode is made of the following: the above-mentioned titanium (Ti)-based nanofiber membrane of the present invention, or the titanium (Ti)-based nanofiber membrane prepared by the method of the present invention.

[0145] The electrode material in the negative electrode for the lithium-sulfur battery of the present invention is a lithium-based metal. In addition, the negative electrode for the lithium-sulfur battery of the present invention may further include a negative electrode current collector.

[0146] The lithium-based metal may be lithium or a lithium alloy. In such a case, the lithium alloy contains elements capable of alloying with lithium. Specifically, the lithium alloy may be an alloy of lithium and at least one selected from the following: Si, Sn, C, Pt, Ir, Ni, Cu, Ti, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Sb, Pb, In, Zn, Ba, Ra, Ge, and Al.

[0147] The lithium-based metal may be in the form of a sheet or foil. In some cases, it may be in the form in which lithium or a lithium alloy is deposited or coated on the current collector by a dry method, or may be in the form in which metals and alloys in the particle phase are deposited or coated by a wet method, etc.

[0148] As the current collector, a negative electrode current collector can be used. There is no particular limitation on the negative electrode current collector as long as the negative electrode current collector has high conductivity and does not cause chemical changes in the battery. The negative electrode current collector can be selected from copper, aluminum, stainless steel, zinc, titanium, silver, palladium, nickel, iron, chromium, their alloys, and their combinations. The stainless steel can be surface-treated with carbon, nickel, titanium, or silver. As the alloy, an aluminum-cadmium alloy can be used. In addition, calcined carbon, a non-conductive polymer surface-treated with a conductive material, or a conductive polymer can be used. Generally, a thin copper plate is used as the negative electrode current collector.

[0149] In addition, the negative electrode for the lithium-sulfur battery of the present invention may further include other components known in the art, such as a protective layer, etc.

[0150] <Lithium-sulfur battery>

[0151] The lithium-sulfur battery of the present invention includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte. The negative electrode is the above-mentioned negative electrode of the present invention, and / or the positive electrode is the above-mentioned positive electrode of the present invention. When the negative electrode is the above-mentioned negative electrode of the present invention, or the positive electrode is the above-mentioned positive electrode of the present invention, the positive electrode compatible with the negative electrode of the present invention and the negative electrode compatible with the positive electrode of the present invention can be those known in the art, respectively.

[0152] The present invention does not specifically limit the materials of the electrolyte and the separator, and the electrolytes and separators well-known to those skilled in the art can be used.

[0153] In the present invention, the lithium-sulfur battery is preferably a button-type lithium-sulfur battery, a soft-pack lithium-sulfur battery or a columnar lithium-sulfur battery. In addition, the present invention does not specifically limit the assembly method of the positive electrode, lithium negative electrode, electrolyte and separator, and those skilled in the art can set it according to actual needs.

[0154] Example

[0155] The embodiments of the present invention will be described in detail below in conjunction with examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. For those not specified in the examples, they are carried out under conventional conditions or conditions recommended by the manufacturer. Those reagents or instruments not specified by the manufacturer can be obtained as conventional products through commercial purchase.

[0156] <Example 1>

[0157] Select 5 g of tetrabutyl titanate (CHO4Ti), 10 ml of N-methylpyrrolidone (NMP: C5H9NO), and 1.2 g of polyacrylonitrile (PAN: [C3H3N] n ) and dissolve them together in a 25 ml beaker. Stir rapidly at room temperature and seal for 8 hours until completely dissolved into a viscous solution as the coaxial electrospinning outer-axis solution. Select a mixed solution of 1 g of polyvinylpyrrolidone (PVP: [C6H9NO] n ) and 6 ml of N-methylpyrrolidone (NMP: C5H9NO) as the inner-axis solution. At room temperature, with a humidity below 35% RH, using coaxial electrospinning technology, apply a positive voltage of 16 KV and a negative voltage of -3 KV to obtain a Ti ion-containing nanofiber membrane, and then carbonize it at 250 °C (1 h, heating rate 1 °C / min) and 900 °C (1 h, heating rate 5 °C / min) in an atmosphere of high-purity argon. After reaching room temperature, a nanofiber carbon membrane with TiO2 as the catalytic unit is obtained (specific surface area is 120 m 2 / g, and the mass percentage of Ti in the nanofiber carbon membrane is 48.6%).

[0158] Subsequently, cut the obtained nanofiber carbon membrane into circular electrodes with a diameter of 12 - 14 mm and use them as the membrane reactor for the positive electrode and the artificial SEI for the negative electrode to match the commercial lithium-sulfur battery electrolyte and separator to construct a high-performance button-type lithium-sulfur battery.

[0159] The composition of the electrolyte is: LiTFSI (1.0 M) is dissolved in a mixed solvent of DOL and DME (DOL:DME = 1:1 Vol%), and 2% LiNO3 is added.

[0160] The battery separator is a PP-based separator celgard 2400.

[0161] The positive electrode is prepared as follows: S powder and activated carbon are ball-milled, and after heat treatment, an S / C composite material is formed. It is ball-milled with a binder (PVDF) and a conductive agent in proportion, and then blended into a paste by modulation with a solvent (NMP), and then evenly coated on the surface of carbon-coated aluminum foil. After vacuum drying at 50 °C to 80 °C, the sulfur positive electrode active material layer is obtained. The ratio of the S / C composite material, the binder (PVDF or PTFE), and the conductive material as the electrode material is 7:2:1. Furthermore, the obtained nanofiber carbon film is laminated on the sulfur positive electrode active material layer.

[0162] The lithium negative electrode uses a smooth lithium metal sheet with a thickness of about 450 μm. The obtained nanofiber carbon film is laminated on the lithium negative electrode.

[0163] <Example 2>

[0164] 15 g of tetrabutyl titanate (CHO4Ti), 12 ml of N-methylpyrrolidone (NMP: C5H9NO), and 1.5 g of polyacrylonitrile (PAN: n ) are dissolved together in a 25 ml beaker, and rapidly stirred at room temperature and sealed for 8 hours until completely dissolved into a viscous solution as the coaxial electrospinning outer-axis solution. A mixed solution of 1.5 g of polystyrene (PS: n ) and 6 ml of N-methylpyrrolidone (NMP: C5H9NO) is used as the inner-axis solution. At room temperature and with a humidity below 35% RH, using coaxial electrospinning technology, with a positive voltage of 18 KV and a negative voltage of -2 KV, a nanofiber carbon film containing Ti ions is obtained. Subsequently, it is carbonized in an atmosphere of high-purity hydrogen / argon mixture (H2 / Ar) at 250 °C (2 h, heating rate 1.5 °C / min) and 1000 °C (1 h, heating rate 5 °C / min). After reaching room temperature, a nanofiber carbon film with Ti4O7 as the catalytic unit is obtained (specific surface area is 149 m 2 / g, and the mass percentage content of Ti in the nanofiber carbon film is 70.3%).

[0165] Subsequently, the obtained nanofiber carbon film is cut into circular electrodes with a diameter of 12 - 14 mm and used as the membrane reactor for the positive electrode and the artificial SEI for the negative electrode respectively. Furthermore, a high-performance button lithium-sulfur battery is constructed by matching a commercial lithium-sulfur battery electrolyte and separator in the same manner as in Example 1.

[0166] <Example 3>

[0167] 5 g of tetrabutyl titanate (CHO4Ti), 8 ml of N-methylpyrrolidone (NMP: C5H9NO), and 1.5 g of polyacrylonitrile (PAN: n)1.2 g is co-dissolved in a 25 ml beaker, and rapidly stirred at room temperature and sealed for 8 hours until it is completely dissolved into a viscous solution as the electrospinning outer axis solution. 1.2 g of polystyrene (PS: [C8H8] n ) and a mixed solution of 5 ml of N-methylpyrrolidone (NMP: C5H9NO) are used as the inner axis solution. At room temperature, with a humidity below 35% RH, using coaxial electrospinning technology, a positive voltage of 18 kV and a negative voltage of -2 kV are applied to obtain a nanofiber membrane containing Ti ions. Subsequently, it is carbonized at 250 °C (2 h, heating rate 1 °C / min) and 1000 °C (6 h, heating rate 5 °C / min) in an atmosphere of high-purity nitrogen. After reaching room temperature, a nanofiber carbon membrane with TiN as the catalytic unit is obtained (specific surface area is 191 m 2 / g, and the mass percentage of Ti in the nanofiber carbon membrane is 49.5%).

[0168] Subsequently, the obtained nanofiber carbon membrane is cut into circular electrodes with a diameter of 12 - 14 mm as the positive electrode membrane reactor. Furthermore, except for not using the negative artificial SEI, a high-performance button lithium-sulfur battery is constructed by matching the commercial lithium-sulfur battery electrolyte and separator in the same manner as in Example 1.

[0169] <Example 4>

[0170] 6 g of tetrabutyl titanate (CHO4Ti), 10 ml of N-methylpyrrolidone (NMP: C5H9NO), and 1.5 g of polyacrylonitrile (PAN: [C3H3N] n ) are co-dissolved in a 25 ml beaker, and rapidly stirred at room temperature and sealed for 8 hours until it is completely dissolved into a viscous solution as the electrospinning outer axis solution. 1.5 g of polystyrene (PS: [C8H8] n ) and a mixed solution of 6 ml of N-methylpyrrolidone (NMP: C5H9NO) are used as the inner axis solution. At room temperature, with a humidity below 35% RH, using coaxial electrospinning technology, a positive voltage of 17 kV and a negative voltage of -3 kV are applied to obtain a nanofiber membrane containing Ti ions. Subsequently, it is carbonized at 250 °C (2 h, heating rate 1 °C / min) and 800 °C (2 h, heating rate 2.5 °C / min) in an atmosphere of Se powder vapor accompanied by a high-purity hydrogen / argon mixture. After reaching room temperature, a nanofiber carbon membrane with TiSe2 as the catalytic unit is obtained (specific surface area is 154 m 2 / g, and the mass percentage of Ti in the nanofiber carbon membrane is 56.8 mass%).

[0171] Subsequently, the obtained carbon nanofiber membrane was sheared into circular electrodes with a diameter of 12-14 mm as artificial SEI for the negative electrode. Furthermore, except for not using the positive electrode membrane reactor, a high-performance button lithium-sulfur battery was constructed by matching a commercial lithium-sulfur battery electrolyte and separator in the same manner as in Example 1.

[0172] <Example 5>

[0173] 8 g of tetrabutyl titanate (CHO4Ti), 15 ml of N-methylpyrrolidone (NMP: C5H9NO), and 2 g of polyacrylonitrile (PAN: [C3H3N] n ) were co-dissolved in a 25 ml beaker and rapidly stirred at room temperature for 10 hours until completely dissolved into a viscous solution as the outer-axis solution for electrospinning. A mixed solution of 1.8 g of polystyrene (PS: [C8H8] n ) and 8 ml of N-methylpyrrolidone (NMP: C5H9NO) was used as the inner-axis solution. At room temperature and with a humidity below 35% RH, using coaxial electrospinning technology, a positive voltage of 16 kV and a negative voltage of -3 kV were applied to obtain a Ti-ion-containing nanofiber membrane, which was then carbonized at 250 °C (3 h, heating rate 1 °C / min) and 800 °C (12 h, heating rate 2 °C / min) in an atmosphere of Te powder vapor accompanied by a high-purity hydrogen / argon mixture. After reaching room temperature, a carbon nanofiber membrane with TiTe2 as the catalytic unit was obtained (specific surface area: 217 m 2 / g, mass percentage of Ti in the carbon nanofiber membrane: 60.6%).

[0174] Subsequently, the obtained carbon nanofiber membrane was sheared into circular electrodes with a diameter of 12-14 mm as the membrane reactor for the positive electrode and artificial SEI for the negative electrode, respectively. Furthermore, a high-performance button lithium-sulfur battery was constructed by matching a commercial lithium-sulfur battery electrolyte and separator in the same manner as in Example 1.

[0175] <Example 6>

[0176] 10 g of tetrabutyl titanate (CHO4Ti), 18 ml of N-methylpyrrolidone (NMP: C5H9NO), and 3 g of polyacrylonitrile (PAN: [C3H3N] n ) were co-dissolved in a 25 ml beaker and rapidly stirred at room temperature for 12 hours until completely dissolved into a viscous solution as the outer-axis solution for electrospinning. 1.6 g of polystyrene (PS: [C8H8] n) A mixed solution with 7 ml of N-methylpyrrolidone (NMP: C5H9NO) is used as the inner-axis solution. At room temperature with a humidity below 35% RH, using coaxial electrospinning technology, a positive voltage of 19 KV and a negative voltage of -2 KV are applied to obtain a nanofiber membrane containing Ti ions. Subsequently, it is carbonized at 250 °C (1 h, heating rate 1 °C / min) and 700 °C (4 h, heating rate 5 °C / min) in an atmosphere of S powder vapor accompanied by a high-purity hydrogen / argon gas mixture. After reaching room temperature, a nanofiber carbon membrane with TiS2 as the catalytic unit is obtained (specific surface area is 316 m 2 / g, and the mass percentage of Ti in the nanofiber carbon membrane is 65.1%).

[0177] Subsequently, the obtained nanofiber carbon membrane is cut into 50 mm × 80 mm rectangular modules to be used as the membrane reactor for the positive electrode and the artificial SEI for the negative electrode respectively, and the same positive electrode, negative electrode, commercial lithium-sulfur battery electrolyte, and separator as in Example 1 are used to construct a high-performance soft-pack lithium-sulfur battery.

[0178] <Example 7>

[0179] 6 g of tetrabutyl titanate (CHO4Ti), 12 ml of N-methylpyrrolidone (NMP: C5H9NO), and 1.5 g of polyacrylonitrile (PAN: [C3H3N] n ) are co-dissolved in a 25 ml beaker. At room temperature, it is sealed and rapidly stirred for 8 hours until it is completely dissolved into a viscous solution as the electrospinning outer-axis solution. A mixed solution of 1.4 g of polystyrene (PS: [C8H8] n ) and 5 ml of N-methylpyrrolidone (NMP: C5H9NO) is used as the inner-axis solution. At room temperature with a humidity below 35% RH, using coaxial electrospinning technology, a positive voltage of 15 KV and a negative voltage of -3 KV are applied to obtain a nanofiber membrane containing Ti ions. Subsequently, it is carbonized at 250 °C (1 h, heating rate 0.8 °C / min) and 1200 °C (4 h, heating rate 4 °C / min) in an atmosphere of B (sodium tetraborate: Na2B4O7) vapor accompanied by a high-purity hydrogen / argon gas mixture. After reaching room temperature, a nanofiber carbon membrane with TiB2 as the catalytic unit is obtained (specific surface area is 3 June 6 m 2 / g, and the mass percentage of Ti in the nanofiber carbon membrane is 54.9%).

[0180] Subsequently, the obtained nanofiber carbon membrane is cut into 50 mm × 80 mm rectangular modules to be used as the membrane reactor for the positive electrode and the artificial SEI for the negative electrode respectively, and then a high-performance soft-pack lithium-sulfur battery is constructed in the same manner as in Example 6 by matching the commercial lithium-sulfur battery electrolyte and separator.

[0181] <Example 8>

[0182] Select 5 g of tetrabutyl titanate (CHO4Ti), 8 ml of N-methylpyrrolidone (NMP: C5H9NO), and 1.2 g of polyacrylonitrile (PAN: [C3H3N] n ) and dissolve them together in a 25 ml beaker. Stir rapidly and seal at room temperature for 8 hours until completely dissolved into a viscous solution as the coaxial electrospinning outer-axis solution. Select a mixed solution of 1.2 g of polystyrene (PS: [C8H8] n ) and 5 ml of N-methylpyrrolidone (NMP: C5H9NO) as the inner-axis solution. At room temperature with a humidity below 35% RH, use coaxial electrospinning technology with a positive voltage of 18 KV and a negative voltage of -2 KV to obtain a Ti-ion-containing nanofiber membrane, and then carbonize it at 250 °C (2 h, heating rate 1 °C / min) and 1700 °C (3 h, heating rate 5 °C / min) under a high-purity argon atmosphere. After reaching room temperature, a nanofiber carbon membrane with TiC as the catalytic unit is obtained (specific surface area is 256 m 2 / g, and the mass percentage of Ti in the nanofiber carbon membrane is 51.6%).

[0183] Subsequently, cut the obtained nanofiber carbon membrane into circular electrodes with a diameter of 12 - 14 mm as the positive electrode for the membrane reactor. Then, except for not using the negative artificial SEI, construct a high-performance button lithium-sulfur battery by matching the commercial lithium-sulfur battery electrolyte and separator in the same manner as in Example 1.

[0184] <Example 9>

[0185] Select 8 g of tetrabutyl titanate (CHO4Ti), 9 ml of N-methylpyrrolidone (NMP: C5H9NO), and 1.5 g of polyacrylonitrile (PAN: [C3H3N] n ) and dissolve them together in a 25 ml beaker. Stir rapidly and seal at room temperature for 8 hours until completely dissolved into a viscous solution as the coaxial electrospinning outer-axis solution. Select a mixed solution of 1.0 g of polystyrene (PS: [C8H8] n ) and 4 ml of N-methylpyrrolidone (NMP: C5H9NO) as the inner-axis solution. At room temperature with a humidity below 35% RH, use coaxial electrospinning technology with a positive voltage of 16 KV and a negative voltage of -3 KV to obtain a Ti-ion-containing nanofiber membrane, and then carbonize it at 270 °C (2 h, heating rate 1 °C / min) and 1000 °C (6 h, heating rate 5 °C / min) under a high-purity nitrogen atmosphere. After reaching room temperature, a nanofiber carbon membrane with TiN as the catalytic unit is obtained (specific surface area is 195 m 2 / g, and the mass percentage of Ti in the nanofiber carbon membrane is 61.2%).

[0186] Subsequently, it is cut into circular electrodes with a diameter of 12 - 14 mm as the artificial SEI for the negative electrode. Furthermore, except for not using the membrane reactor for the positive electrode, a high-performance button lithium-sulfur battery is constructed by matching a commercial lithium-sulfur battery electrolyte and separator.

[0187] <Example 10>

[0188] Select 10 g of tetrabutyl titanate (CHO4Ti), 10 ml of N-methylpyrrolidone (NMP: C5H9NO), and 1.0 g of polyacrylonitrile (PAN: [C3H3N] n ) and dissolve them together in a 25-ml beaker. Stir rapidly at room temperature and seal for 8 hours until it is completely dissolved into a viscous solution as the outer-axis solution for electrospinning. Select a mixed solution of 1.0 g of polystyrene (PS: [C8H8] n ) and 4 ml of N-methylpyrrolidone (NMP: C5H9NO) as the inner-axis solution. At room temperature and with a humidity below 35% RH, using coaxial electrospinning technology, apply a positive voltage of 16 kV and a negative voltage of -3 kV to obtain a nanofiber membrane containing Ti ions. Subsequently, carbonize it in an atmosphere of high-purity argon at 270 °C (2 h, heating rate 1 °C / min) and 1600 °C (5 h, heating rate 5 °C / min). After reaching room temperature, a nanofiber carbon membrane with TiC as the catalytic unit is obtained (specific surface area is 197 m 2 / g, and the mass percentage of Ti in the nanofiber carbon membrane is 64.6%).

[0189] Subsequently, it is cut into circular electrodes with a diameter of 12 - 14 mm as the artificial SEI for the negative electrode. Furthermore, except for not using the positive electrode membrane reactor, a high-performance button lithium-sulfur battery is constructed in the same manner as in Example 1 by matching a commercial lithium-sulfur battery electrolyte and separator.

[0190] <Example 11>

[0191] Select 3 g of tetrabutyl titanate (CHO4Ti), 10 ml of N-methylpyrrolidone (NMP: C5H9NO), and 0.9 g of polyacrylonitrile (PAN: [C3H3N] n ) and dissolve them together in a 25-ml beaker. Stir rapidly at room temperature and seal for 8 hours until it is completely dissolved into a viscous solution as the outer-axis solution for electrospinning. Select 1.2 g of polystyrene (PS: [C8H8] n) The mixed solution with 5 ml of N-methylpyrrolidone (NMP: C5H9NO) is used as the inner-axis solution. At room temperature with a humidity below 35% RH, using coaxial electrospinning technology, a positive voltage of 17 KV and a negative voltage of -2 KV are applied to obtain a nanofiber membrane containing Ti ions. Subsequently, it is carbonized at 270 °C (for 2 h with a heating rate of 1 °C / min) and 1100 °C (for 5 h with a heating rate of 5 °C / min) in an atmosphere of high-purity nitrogen. After reaching room temperature, a nanofiber carbon membrane with TiN as the catalytic unit is obtained (specific surface area is 206 m 2 / g, and the mass percentage content of Ti in the nanofiber carbon membrane is 30%).

[0192] Subsequently, it is cut into circular electrodes with a diameter of 12 - 14 mm as the artificial SEI for the negative electrode. Then, except for not using the membrane reactor for the positive electrode, a high-performance button lithium-sulfur battery is constructed by matching the commercial lithium-sulfur battery electrolyte and separator in the same manner as in Example 1.

[0193] <Example 12>

[0194] 18 g of tetrabutyl titanate (CHO4Ti), 15 ml of N-methylpyrrolidone (NMP: C5H9NO), and 1.2 g of polyacrylonitrile (PAN: [C3H3N] n ) are co-dissolved in a 25 ml beaker. At room temperature, it is sealed and rapidly stirred for 8 hours until it is completely dissolved into a viscous solution as the electrospinning outer-axis solution. A mixed solution of 1.2 g of polystyrene (PS: [C8H8] n ) and 6 ml of N-methylpyrrolidone (NMP: C5H9NO) is used as the inner-axis solution. At room temperature with a humidity below 35% RH, using coaxial electrospinning technology, a positive voltage of 18 KV and a negative voltage of -3 KV are applied to obtain a nanofiber membrane containing Ti ions. Subsequently, it is carbonized at 250 °C (for 2 h with a heating rate of 1.5 °C / min) and 1000 °C (for 1.5 h with a heating rate of 5 °C / min) in an atmosphere of high-purity hydrogen / argon mixture (H2 / Ar). After reaching room temperature, a nanofiber carbon membrane with Ti4O7 as the catalytic unit is obtained (specific surface area is 155 m 2 / g, and the mass percentage content of Ti in the nanofiber carbon membrane is 75%).

[0195] Subsequently, the obtained nanofiber carbon membrane is cut into circular electrodes with a diameter of 12 - 14 mm as the membrane reactor for the positive electrode and the artificial SEI for the negative electrode respectively. Then, a high-performance button lithium-sulfur battery is constructed by matching the commercial lithium-sulfur battery electrolyte and separator in the same manner as in Example 1.

[0196] <Comparative Example 1>

[0197] 8 ml of N-methylpyrrolidone (NMP: C5H9NO) and polyacrylonitrile (PAN: [C3H3N]n ) 1.2 g and 2 g of tetrabutyl titanate (C₁₆H₃₆O₄Ti) were dissolved together in a 25 ml beaker. Under room temperature and sealed conditions, rapid stirring was carried out for 8 hours until it was completely dissolved into a viscous solution to serve as the electrospinning solution. Under room temperature environment with humidity below 35% RH, using traditional electrospinning technology (instead of coaxial electrospinning), with a positive voltage of 15 KV and a negative voltage of -3 KV, a nanofiber membrane was obtained. Subsequently, it was carbonized at 250 °C (for 2 h, heating rate 1 °C / min) and 800 °C (for 2 h, heating rate 2.5 °C / min) in an atmosphere of Se powder vapor accompanied by a high-purity hydrogen / argon mixture. After reaching room temperature, a nanofiber carbon membrane with TiSe₂ as the catalytic unit was obtained (the specific surface area was 9 m 2 ² / g, and the mass percentage content of Ti in the nanofiber carbon membrane was 57.2%).

[0198] Subsequently, the obtained nanofiber carbon membrane was cut into circular electrodes with a diameter of 12 - 14 mm as the artificial SEI for the negative electrode. Furthermore, except for not using the positive electrode membrane reactor, a high-performance button lithium-sulfur battery was constructed by matching the commercial lithium-sulfur battery electrolyte and separator in the same manner as in Example 1.

[0199] Experimental results showed that the carbonized carbon fiber did not have the desired membrane flexibility, and the specific surface area was only 9 m 2 ² / g, as shown Figure 9 in.

[0200] <Test Methods>

[0201] The test methods adopted in the present invention are described in detail below.

[0202] (Transmission Electron Microscopy Characterization)

[0203] The prepared nanofiber carbon membrane (2 mg) was ultrasonically dispersed in 10 ml of ethanol solution, and its microscopic morphology and the embedded titanium-based compounds were observed through a high-resolution transmission electron microscope. Figure 1 Obtained through transmission electron microscopy characterization.

[0204] (Crystal Structure Analysis)

[0205] The prepared nanofiber carbon membrane (100 mg) was tested using an X-ray diffractometer, with the test range of 10° - 90° and a scanning rate of 5° / min. Figure 2 Obtained through this crystal structure analysis.

[0206] (Electrochemical Workstation Test)

[0207] An electrochemical workstation test device was used to test the assembled lithium-sulfur battery using the cyclic voltammetry test method, with the voltage test range of 1.6 V - 2.8 V and a scanning rate of 0.1 mV / s.Figure 3 Obtained through this test.

[0208] (Lithium Anode Cycle Stability Test)

[0209] Using a battery test system testing equipment, the assembled battery was subjected to a lithium anode cycle stability test. The test conditions were: the current density was 0.5 mA / cm 2 , and the lithium ion deposition capacity was 0.5 mAh / cm 2 . Figure 4 and Figure 10 were each obtained through this lithium anode cycle stability test.

[0210] The inventor of the present invention found that for the battery obtained in Comparative Example 1 ( Figure 10 ), short circuit occurred after cycling for 200 h, which was significantly inferior to Example 4 ( Figure 4 ).

[0211] (Charge and Discharge Performance Test under Non-constant Current Density)

[0212] Using a battery test system testing equipment, the assembled lithium-sulfur battery was subjected to a charge and discharge performance test to obtain the charge specific capacity and the discharge specific capacity. The test conditions were: the voltage test range was 1.6 V to 2.8 V, the current density was selected as 0.1C, 0.2C, 0.5C, 1C, 2C, 3C, 4C, and the high rate 5C, and the number of cycles was 40 times. Figure 5 , Figure 11 and Figure 12 were obtained through this test, where Figure 11 and Figure 12 only show the discharge specific capacity.

[0213] In addition, for the battery obtained in Example 2 and the battery obtained in Example 12, the sulfur effective utilization rate was also calculated. The sulfur effective utilization rate is the ratio of the discharge specific capacity to the theoretical specific capacity of sulfur (discharge specific capacity / theoretical specific capacity of sulfur). The sulfur effective utilization rates of the battery obtained in Example 2 and the battery obtained in Example 12 were both greater than 80.0%. In addition, compared with Example 12, the active sulfur effective utilization rate of the battery obtained in Example 2 was further increased by 8%.

[0214] (Cycling Test under Constant Current Density (1))

[0215] Using a battery test system testing equipment, the assembled lithium-sulfur battery was subjected to a high rate cycle stability test to obtain the charge specific capacity and the discharge specific capacity at different charge and discharge times. The test conditions were: the voltage test range was 1.6 V to 2.8 V, the current density was selected as the high rate 5C, and the number of cycles was 200 times.

[0216] In the present invention, the cyclic test (1) was performed on Example 6, Example 9, Example 10, and Example 11.

[0217] Figure 6 The test results of the battery obtained in Example 6 are shown, where the right vertical axis shows the Coulomb efficiency (unit: %), and the left vertical axis shows the charge specific capacity and discharge specific capacity.

[0218] The Coulomb efficiency refers to the percentage of the discharge capacity to the charge capacity of the battery under charge-discharge conditions (discharge capacity / charge capacity × 100%). The Coulomb efficiency is an index for evaluating the cycle reversibility of the battery.

[0219] Regarding the battery obtained in Example 9, through electrochemical performance analysis, after 200 stable cycles, the Coulomb efficiency is as high as 99.8%.

[0220] Regarding the battery obtained in Example 10, through electrochemical performance analysis, after 200 stable cycles, the Coulomb efficiency is as high as 98.1%.

[0221] Regarding the battery obtained in Example 11, through electrochemical performance analysis, after 200 stable cycles, the Coulomb efficiency is as high as 96.3%.

[0222] (Cyclic test (2) under constant current density)

[0223] Using a battery test system testing device, the assembled lithium-sulfur battery was subjected to a cyclic test to obtain the charge specific capacity and discharge specific capacity at different charge-discharge times. The test conditions were: the voltage test range was 1.6 V to 2.8 V, the current density was 0.1 C, and the number of cycles was 50 times. Figure 7 Obtained through this test.

[0224] (Electrochemical impedance test)

[0225] Using a battery test system testing device, the assembled lithium-sulfur battery was subjected to an electrochemical impedance test. The test conditions were: the voltage test range was 1.6 V to 2.8 V, the open circuit voltage was greater than 2.3 V, the test frequency was 10 -2 Hz to 10 6 Hz, and the electrochemical impedance spectrum of the battery was obtained. Figure 8 Obtained through this test.

[0226] (Specific surface area test method)

[0227] To measure the specific surface area of the powder, the powder sample after drying and degassing treatment was placed in liquid nitrogen, 100 mg of the titanium-based nanofiber membrane powder was used as the test object, and the specific surface area (surface area (SA)) of the powder was calculated by converting the value of the gas molecules required on the powder surface, with the unit of m 2 / g.

[0228] It should be noted that although the technical solutions of the present invention are introduced by specific examples, those skilled in the art can understand that the present invention should not be limited thereto.

[0229] The above has described the embodiments of the present invention. The above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations are obvious to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The choice of terms used herein is intended to best explain the principles of the embodiments, practical applications, or improvements to technologies in the market, or to enable other ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A titanium (Ti)-based nanofiber carbon membrane, characterized in that, It includes: carbon fiber and titanium (Ti)-based compounds, the carbon fibers are formed into a film shape by free interweaving, and the carbon fibers have a microscopic morphological structure containing voids and the carbon fibers are loaded with the titanium (Ti)-based compounds, in addition to titanium (Ti) and carbon (C), the titanium (Ti)-based carbon nanofiber film optionally further contains at least one element selected from oxygen (O), nitrogen (N), phosphorus (P), sulfur (S), selenium (Se), boron (B) and tellurium (Te), The specific surface area of the titanium (Ti)-based nanofiber carbon film ranges from 30 m 2 / g or more.

2. The titanium (Ti)-based nanometer carbon fiber film according to claim 1, characterized in that, the microscopic diameter of the carbon fibers is 10 nm to 1000 nm; and / or the microscopic morphological structure of the carbon fibers includes at least one selected from core-shell structure, hollowed-out structure, porous structure, single-channel hollow pipe structure, double-channel hollow pipe structure and multi-channel hollow pipe structure.

3. The titanium (Ti)-based nanocarbon fiber membrane according to claim 1 or 2, characterized in that, The metal bonds in the titanium (Ti)-based carbon nanofiber film include at least one selected from Ti-O bond, Ti-N bond, Ti-C bond, Ti-P bond, Ti-S bond, Ti-Se bond, Ti-B bond and Ti-Te bond.

4. The titanium (Ti)-based nanofiber carbon membrane according to any one of claims 1 to 3, characterized in that, In the titanium (Ti)-based carbon nanofiber film, the mass percentage content of Ti is 45 to 75%, the mass percentage content of C is 30 to 65%, the mass percentage content of O is 0 to 65%, the mass percentage content of N is 0 to 65%, the mass percentage content of Se is 0 to 60%, the mass percentage content of S is 0 to 65%, the mass percentage content of B is 0 to 65%, and the mass percentage content of Te is 0 to 65%.

5. The titanium (Ti)-based nanometer carbon fiber film according to any one of claims 1 to 4, characterized in that, The specific surface area of the titanium (Ti)-based nanofiber carbon membrane ranges from 60 to 1000 m 2 / g; and / or The titanium (Ti)-based carbon nanofiber film has a micro-mesoporous structure with a pore size range of 2 nm to 100 nm.

6. A preparation method of a titanium (Ti)-based nanofiber carbon film, characterized in that, The method includes: (1) Preparing an electrospinning outer-axis solution, the electrospinning outer-axis solution containing a titanium (Ti) source, a polymer, and solvent A; (2) Preparing an electrospinning inner-axis solution, the electrospinning inner-axis solution containing a sacrificial agent and solvent B; (3) Using the electrospinning outer-axis solution and the electrospinning inner-axis solution, under a voltage condition of negative voltage ≤ -0.1 KV and positive voltage ≥ 5 KV, performing coaxial electrospinning to obtain a precursor fiber film, (4) Carbonizing the precursor fiber film in a carbonizing atmosphere, the carbonizing atmosphere containing at least one selected from inert gas, hydrogen and an atmosphere containing other elements, the other elements being at least one selected from carbon (C), phosphorus (P), sulfur (S), selenium (Se), boron (B) and tellurium (Te).

7. The preparation method according to claim 6, characterized in that, The titanium (Ti) source includes at least one selected from tetrabutyl titanate (C 16 H 36 O4Ti), titanium tetrachloride (TiCl4), titanium oxalate (Ti(C2O4)2), tetramethanol titanium (C4H 12 O4Ti2), sodium metatitanate (Na2Ti3O7). The polymer includes at least one selected from polyacrylonitrile (PAN), polyvinylpyrrolidone (PVP), and polyvinyl alcohol (PEO), the sacrificial agent includes at least one selected from polyvinylpyrrolidone (PVP), polystyrene (PS), polymethyl methacrylate (PMMA), and paraffin wax, solvent A and solvent B each contain at least one selected from N-methylpyrrolidone (NMP) and N,N-dimethylformamide (DMF).

8. The preparation method according to claim 6 or 7, characterized in that, In the electrospinning outer-axis solution, the dosage ratio of the titanium (Ti) source, the polymer, and the solvent A satisfies: titanium (Ti) source: polymer: solvent A = 0.1 g to 20 g: 0.2 g to 6 g: 4 ml to 20 ml; In the electrospinning inner-axis solution, the dosage ratio of the sacrificial agent and the solvent B satisfies: sacrificial agent: solvent B = 0.1 g to 3.0 g: 1 ml to 20 ml.

9. The preparation method according to any one of claims 6 to 8, characterized in that, The carbonization atmosphere is nitrogen, argon, a mixture of hydrogen and argon, a mixture of hydrogen, argon and a C-containing atmosphere, a mixture of hydrogen, argon and a Se-containing atmosphere, a mixture of hydrogen, argon and a Te-containing atmosphere, a mixture of hydrogen, argon and an S-containing atmosphere, or a mixture of hydrogen, argon and a B-containing atmosphere; During the carbonization, the carbonization temperature is 200 °C to 1800 °C, and / or; the carbonization time is 0.5 to 24 h, and / or; the heating rate to the carbonization temperature is 0.2 °C / min to 10 °C / min.

10. A positive electrode for a lithium-sulfur battery, characterized in that, The positive electrode includes a membrane reactor, and the membrane reactor is made of the following: The titanium (Ti)-based nanofiber membrane according to any one of claims 1 to 5, or the titanium (Ti)-based nanofiber membrane prepared by the method according to any one of claims 6 to 9.

11. A negative electrode for a lithium-sulfur battery, characterized in that, The negative electrode includes an artificial SEI for the negative electrode, and the artificial SEI for the negative electrode is made of the following: The titanium (Ti)-based nanofiber membrane according to any one of claims 1 to 5, or the titanium (Ti)-based nanofiber membrane prepared by the method according to any one of claims 6 to 9.

12. A lithium-sulfur battery, characterized in that, The lithium-sulfur battery includes a positive electrode, a negative electrode, a separator between the positive electrode and the negative electrode, and an electrolyte; The positive electrode is the positive electrode according to claim 10, and / or The negative electrode is the negative electrode according to claim 11.

Images