CN114678579A

CN114678579A - Lithium-sulfur battery electrolyte containing selenophenol additive and lithium-sulfur battery

Info

Publication number: CN114678579A
Application number: CN202210233538.1A
Authority: CN
Inventors: 郭玮; 孙俊鹏; 郑思辰; 付永柱
Original assignee: Zhengzhou University
Current assignee: Zhengzhou University
Priority date: 2022-03-10
Filing date: 2022-03-10
Publication date: 2022-06-28
Anticipated expiration: 2042-03-10
Also published as: CN114678579B

Abstract

The invention discloses a lithium-sulfur battery electrolyte containing a phenylselenol (PhSeH) additive and a lithium-sulfur battery. The electrolyte comprises an ether solvent, lithium salt and an additive, wherein the additive is benzene selenol. According to the electrolyte of the lithium-sulfur battery, organic small-molecular selenol phenylselenophenol is used as an additive, S atoms are fixed through Se-S bonds, an intermediate product PhSeSSePh is generated in the charging and discharging process, the sulfur elementary substance state is returned in the later stage of the charging process, the original redox path of the battery is changed, the battery process is completely reversible, the high-capacity characteristic of the lithium-sulfur battery is fully realized, and the cycle stability of the lithium-sulfur battery is greatly improved.

Description

Lithium-sulfur battery electrolyte containing selenophenol additive and lithium-sulfur battery

Technical Field

The invention belongs to the technical field of lithium-sulfur battery electrolyte, and particularly relates to lithium-sulfur battery electrolyte containing a selenophenol additive and a lithium-sulfur battery.

Background

With the rapid development of portable electronic devices, the society is concerned more and more about the development of lithium batteries. 372mAh g of lithium ion battery^-1The theoretical specific capacity of (a) has not been able to meet the demands of the public. Meanwhile, the lithium-sulfur battery has 2600Wh kg ^-1The energy density of (2) and the abundant sulfur resource reserves in the crust are favored by researchers. During the discharge process, S₈Accepting 8 electrons and 8 Li⁺Corresponding to 1675mAh g^-1Theoretical ratio of (A)Capacity. However, lithium sulfur batteries also face these challenges: (1) severe shuttling effects: the high-order lithium polysulfide has high solubility in an ether electrolyte system used in a lithium sulfur battery, so that the lithium polysulfide is transferred in the battery mainly by concentration gradient and chemical potential, and then the lithium polysulfide is diffused to a negative electrode and reacts with a lithium sheet, and the problems of loss of active substance sulfur, corrosion of the lithium sheet, reduction of coulombic efficiency and even safety are caused. (2) Due to S₈And the charge and discharge products thereof have lower ionic conductivity and electronic conductivity, the reaction kinetics of the battery is slower, and the utilization rate of active substances is lower. Therefore, to improve the electrochemical performance of the battery, the current work is mainly focused on suppressing the shuttle effect of sulfide, improving the conductivity of the positive electrode material, and replacing the conventional electrolyte components. The organic sulfur compound is a novel lithium sulfur battery positive electrode material which can be used for replacing elemental sulfur. If the element Se participates in the composition of the electrode material, the cell will exhibit lower voltage hysteresis due to its higher ionic conductivity.

The addition of the electrolyte additive may form a separator near the positive electrode by changing the kind of active material, catalyze disproportionation of lithium polysulfide, react with lithium polysulfide, or change the composition of the SEI film to help form a denser SEI film, but at the same time inevitably reduces the energy density of the battery, and may sometimes pose serious challenges with respect to the flammability, toxicity, viscosity, ionic conductivity, etc. of the electrolyte. Therefore, it is urgent to find an electrolyte additive that can improve the electrochemical performance of a battery while suppressing the formation of lithium polysulfide.

Disclosure of Invention

The invention aims to provide lithium-sulfur battery electrolyte containing a selenophenol additive and a lithium-sulfur battery. The additive phenylselenol realizes fixation of S atoms through Se-S bonds, generates an intermediate product PhSeSSePh in the charging and discharging process, returns to a sulfur simple substance state in the later stage of the charging process, changes the original redox path of the battery, is completely reversible in the battery process, fully realizes the high-capacity characteristic of the lithium-sulfur battery, and greatly improves the cycling stability of the lithium-sulfur battery.

In order to solve the technical problems, the invention provides the following technical scheme:

The lithium-sulfur battery electrolyte containing the phenylselenol additive comprises an ether solvent, lithium salt and the additive, wherein the additive is phenylselenol.

According to the scheme, the concentration of the phenylselenophenol in the electrolyte is 0.05-1.0 mol/L.

According to the scheme, the ether solvent is a mixed solution of DME (ethylene glycol dimethyl ether) and DOL (1, 3-dioxolane), wherein the volume ratio of DME to DOL solvent is (0.8-1.2): 1.

According to the scheme, the lithium salt is LiTFSI (lithium bis (trifluoromethyl sulfonyl) imide) and LiNO₃The mixture comprises LiTFSI with the concentration of 1.0-1.5 mol/L and LiNO₃The concentration of (b) is 0.15-0.25 mol/L.

The lithium-sulfur battery comprises a positive electrode material, a negative electrode material, a diaphragm and the lithium-sulfur battery electrolyte containing the selenophene additive.

According to the scheme, the positive electrode material is multi-wall carbon nano tube paper loaded with sulfur simple substances.

Preferably, the sulfur loading is 0.88-1.15 mg cm^-2The diameter of the carbon nanotube paper is 11-13 mm.

According to the scheme, the preparation method of the cathode material comprises the following steps: dissolving a certain amount of sulfur simple substance in a proper amount of carbon disulfide, after the sulfur simple substance is completely dissolved, taking a proper amount of solution to be dripped on the multi-wall carbon nano tube paper, and then drying the multi-wall carbon nano tube paper in a blast oven at the temperature of 60-65 ℃ for 12-13 hours to completely volatilize the solvent.

According to the scheme, the negative electrode material is a lithium metal sheet.

The septum was Celgard 2400 according to the protocol above.

According to the scheme, the electrolyte containing the phenylselenol additive is dripped on two sides of the diaphragm to be in full contact with the positive electrode and the negative electrode, and the lithium-sulfur battery is assembled.

Provides the application of the phenylselenol serving as an additive in the electrolyte of the lithium-sulfur battery.

The application of the lithium-sulfur battery electrolyte containing the phenylselenol additive in the lithium-sulfur battery is provided, wherein:

when the lithium-sulfur battery is a button battery, the concentration of the phenylselenol in the electrolyte is 0.5-1.0 mol/L;

when the lithium-sulfur battery is a soft package battery, the concentration of the phenylselenol in the electrolyte is 0.05-0.30 mol/L.

When the lithium-sulfur battery electrolyte containing the selenophenol additive is used for a lithium-sulfur battery, the charge-discharge redox reaction path of the battery is changed, the generation and shuttling of long-chain polysulfide in the charge-discharge process are avoided, the loss of positive active substances is reduced, and the battery performance is improved; wherein: during the discharging process, the phenylselenophenol reacts with elemental sulfur to generate an intermediate product PhSeSSePh, and finally lithium phenylselenophosphate (PhSeLi) and lithium sulfide (Li) are generated₂S), the generation of long-chain polysulfide is avoided; during charging, the phenylselenium free radical is combined with the sulfur free radical to generate an intermediate product PhSeSSePh, but because the Se-S bond energy is low, the Se-S bond is broken at high voltage, the PhSeSSePh generated during charging is decomposed and returns to S again ₈And the elementary substance state makes the battery process more reversible. In conclusion, after the phenylselenol is introduced into a lithium-sulfur battery system as an electrolyte additive, the reaction path of the traditional lithium-sulfur battery is changed, the generation of lithium polysulfide is reduced, and the shuttle effect is inhibited, so that the utilization rate of active substances is improved, and the electrochemical performance of the battery is improved.

The beneficial effects of the invention are as follows:

the lithium-sulfur battery electrolyte provided by the invention takes organic micromolecular phenylselenol as an electrolyte additive, the phenylselenol realizes the fixation of an S atom through a Se-S bond, PhSeSSePh is generated in the charging and discharging process, and the S atom is returned to S in the later stage of the charging process₈The generation and shuttling of long-chain polysulfide in the charging and discharging processes are avoided, the utilization rate of active substances is improved, and the battery is more reversible; meanwhile, the overall overpotential of the battery is reduced due to the higher ionic conductivity of the Se element; when the electrolyte is used for a lithium-sulfur battery, the electrochemical performance is excellent, and 1436mAh g is achieved at the multiplying power of 0.5C^-1The maximum specific discharge capacity of the lithium ion battery can still maintain 1300mAh g after 200 cycles of circulation^-1The reversible specific capacity of (2) has a capacity retention rate of 91.86%, and is sufficientThe high-capacity characteristic of the lithium-sulfur battery is realized, the cycling stability of the lithium-sulfur battery is greatly improved, and the potential of the lithium-sulfur battery in commercial application is improved.

Drawings

FIG. 1 is a graph of the long cycle performance at 1C rate of a lithium sulfur CR2032 coin cell of example 1 of the present invention containing 0.50mol/L phenylselenol additive.

Fig. 2 is a voltage-capacity curve of the coin cell 1C multiplying power of the lithium sulfur CR2032 containing the phenylselenol additive of 0.50mol/L in example 1 of the present invention.

Fig. 3 is a long cycle performance diagram of the lithium sulfur CR2032 coin cell of example 2 of the invention at 1C rate containing 0.70mol/L phenylselenol additive.

Fig. 4 is a voltage-capacity curve of the coin cell 1C multiplying power of the lithium sulfur CR2032 containing 0.70mol/L of the phenylselenol additive in example 2 of the present invention.

FIG. 5 is a graph of the long cycle performance at 1C rate of a lithium sulfur CR2032 coin cell of example 3 containing 1.0mol/L phenylselenol additive.

FIG. 6 is a voltage-capacity curve at 1C rate for a lithium sulfur CR2032 coin cell of example 3 containing 1.0mol/L phenylselenol additive.

Fig. 7 is a voltage-capacity curve of 0.5C magnification of the lithium sulfur CR2032 coin cell corresponding to the matrix electrolyte and the lithium sulfur CR2032 coin cell containing 0.70mol/L of the phenylselenol additive in example 4 of the present invention.

FIG. 8 is a comparison graph of long cycle performance at 0.5C rate of a lithium sulfur CR2032 coin cell containing 0.70mol/L phenylselenol additive and a matrix electrolyte in example 4 of the present invention.

FIG. 9 is a graph of the rate performance of a lithium sulfur CR2032 coin cell of example 4 containing 0.70mol/L phenylselenol additive.

Fig. 10 is a graph of the cycle performance of the lithium sulfur pouch battery containing 0.10mol/L phenylselenol additive in example 5 of the present invention.

Fig. 11 is a mass spectrum of phenylselenol (PhSeH) generated after lithium in the discharging product lithium phenylselenol (PhSeLi) of the lithium sulfur CR2032 coin cell containing 0.70mol/L phenylselenol additive in example 4 of the present invention is replaced by proton hydrogen.

FIG. 12 is a mass spectrum of diphenyl diselenide (PhSeSePh) as a charging product of lithium sulfur CR2032 coin cell in example 4 of the present invention containing 0.70mol/L phenylselenol additive.

FIG. 13 is a mass spectrum of the product PhSeSSePh (DPDSES) of the charging of the lithium sulfur CR2032 coin cell containing 0.70mol/L phenylselenol additive in example 4 of the present invention.

FIG. 14 is a comparison of UV-Vis of the positive electrode when the button cell of the invention example 4, which contains 0.70mol/L phenylselenol additive, and the button cell of the matrix electrolyte, which corresponds to the button cell of the lithium-sulfur CR2032, are discharged to 2.1V.

FIG. 15 is an in-situ Raman spectrum of the first-cycle discharge process of the lithium-sulfur CR2032 coin cell of example 4 of the present invention containing 0.70mol/L phenylselenol additive.

FIG. 16 is an in-situ Raman spectrum of a lithium sulfur CR2032 coin cell charging process containing 0.70mol/L phenylselenol additive in example 4 of the present invention.

FIG. 17 is a XPS plot (S2 p) of the charged positive electrode of a lithium sulfur CR2032 coin cell battery of example 4 of the present invention containing 0.70mol/L of a phenylselenol additive.

FIG. 18 is an XPS plot (Se 3d) of the positive electrode of a charged lithium sulfur CR2032 coin cell battery of example 4 of the invention containing 0.70mol/L of a phenylselenol additive.

FIG. 19 is an XPS plot (Se 3d) of the positive electrode after discharge of a lithium sulfur CR2032 coin cell battery of example 4 of the invention containing 0.70mol/L of a phenylselenol additive.

FIG. 20 is a FT-IR spectrum of phenylselenol and the reaction mixture of elemental sulfur and phenylselenol of example 4 of the present invention.

FIG. 21 is an ex-situ Raman spectrum of elemental sulfur and phenylselenol raw materials and a reaction mixture thereof in example 4 of the present invention.

FIG. 22 is an SEM image of a charged sulfur positive electrode of a lithium sulfur CR2032 coin cell battery of the invention in example 4 containing 0.70mol/L phenylselenol additive.

FIG. 23 is an SEM image of the sulfur positive electrode after discharge of a lithium sulfur CR2032 coin cell containing 0.70mol/L phenylselenol additive in example 4 of the invention.

FIG. 24 is a TEM image of a charged sulfur positive electrode of a lithium sulfur CR2032 coin cell containing 0.70mol/L phenylselenol additive of example 4 of the present invention.

Detailed Description

In order to make the technical solutions of the present invention better understood, the present invention is further described in detail below with reference to the accompanying drawings.

Example 1

The lithium-sulfur battery electrolyte containing the phenylselenol additive comprises an ether solvent, lithium salt and the additive; wherein the ether solvent is a mixed solution of DOL and DME with the volume ratio of 1:1, and the lithium salt LiTFSI and LiNO are₃LiTFSI concentration of 1mol/L, LiNO₃The concentration is 0.15mol/L, the additive is benzene selenol (PhSeH), and the concentration is 0.50 mol/L.

The lithium-sulfur battery electrolyte containing the selenophene additive obtained in the embodiment, a carbon nanotube anode loaded with elemental sulfur, a diaphragm and a lithium metal cathode are assembled together to form the CR2032 button battery.

In the carbon nano tube anode loaded with the sulfur simple substance, the sulfur loading is 1mg, and the diameter of the carbon nano tube paper is 11 mm. The sulfur-containing carbon nano tube paper is prepared by dissolving sulfur solid powder in a carbon disulfide solvent, then dropwise adding the carbon nano tube paper on the carbon nano tube paper, and drying the carbon nano tube paper for 12 to 13 hours in a blast drying oven at the temperature of between 60 and 65 ℃ to volatilize the solvent.

The septum was Celgard-2400 with a diameter of 19 mm.

The lithium metal negative electrode had a thickness of 450 μm and a diameter of 15.6 mm.

Electrochemical tests were performed on the above-described lithium sulfur CR2032 coin cells containing 0.50mol/L of phenylselenophenol electrolyte.

FIG. 1 is a long cycle performance curve of the lithium-sulfur CR2032 coin cell containing 0.50mol/L phenylselenophenol obtained in the example at a magnification of 1C, and the reversible specific capacity of the coin cell reaches 1100mAh g ^-1The coulomb efficiency is as high as 99%, and the capacity and coulomb efficiency are almost not attenuated after circulating for 100 circles.

Fig. 2 is a voltage-capacity curve of the lithium sulfur CR2032 button cell containing 0.50mol/L of phenylselenol obtained in this example at a magnification of 1C, and three obvious discharge platforms can be seen, and the cell overpotential is small.

Example 2

The lithium-sulfur battery electrolyte containing the phenylselenol additive comprises an ether solvent, lithium salt and the additive; wherein the ether solvent is a mixed solution of DOL and DME with the volume ratio of 1:1, and the lithium salt LiTFSI and LiNO are₃LiTFSI concentration of 1mol/L, LiNO₃The concentration is 0.15mol/L, the additive is benzene selenol (PhSeH), and the concentration is 0.70 mol/L.

The septum was Celgard-2400 with a diameter of 19 mm.

And carrying out electrochemical test on the lithium sulfur CR2032 coin cell containing 0.70mol/L of phenylselenol electrolyte.

FIG. 3 is a long cycle performance curve of the lithium sulfur CR2032 coin cell containing 0.70mol/L phenylselenol obtained in this example at a 1C rate, with a maximum specific discharge capacity of 1248mAh g^-1。

Fig. 4 is a voltage-capacity curve of the lithium sulfur CR2032 coin cell containing 0.70mol/L phenylselenol obtained in this example at a magnification of 1C, and it can be seen that three more obvious discharge platforms are present, and the cell overpotential is small.

Example 3

The lithium-sulfur battery electrolyte containing the phenylselenol additive comprises an ether solvent, lithium salt and the additive; wherein the ether solvent is a mixed solution of DOL and DME with the volume ratio of 1:1, and the lithium salt LiTFSI and the LiNO are₃LiTFSI concentration of 1mol/L, LiNO₃The concentration is 0.15mol/L, the additive is benzene selenol (PhSeH), and the concentrations are respectively 1.0 mol/L.

The septum was Celgard-2400 with a diameter of 19 mm.

And carrying out electrochemical test on the lithium sulfur CR2032 coin cell containing the 1.0mol/L phenylselenol electrolyte.

FIG. 5 is a long cycle performance curve of the lithium sulfur CR2032 coin cell containing 1.0mol/L phenylselenol obtained in the embodiment at a magnification of 1C, and the reversible specific capacity reaches 1100mAh g after 40 cycles^-1The coulomb efficiency is as high as 99%, and the capacity and coulomb efficiency are almost not attenuated after circulating for 100 circles.

Fig. 6 is a voltage-capacity curve of the lithium sulfur CR2032 coin cell containing 1.0mol/L phenylselenol obtained in this example at 1C magnification, and it can be seen that three more obvious discharge platforms are present, and the cell overpotential is small.

Example 4

The lithium-sulfur battery electrolyte containing the phenylselenol additive comprises an ether solvent, lithium salt and the additive; wherein the ether solvent is a mixed solution of DOL and DME with the volume ratio of 1:1, and the lithium salt LiTFSI and the LiNO are₃LiTFSI concentration of 1mol/L, LiNO₃The concentration is 0.15mol/L, the additive is benzene selenol (PhSeH), and the concentration is 0.70 mol/L.

Preparing a matrix lithium-sulfur electrolyte, wherein the matrix lithium-sulfur electrolyte contains 1mol/L LiTFSI and 0.15mol/L LiNO ₃Of DOL and DME (DOL to DME volume ratio of 1: 1). The matrix lithium sulfur electrolyte was used as a comparative example for setting up a control group.

The lithium-sulfur battery electrolyte or matrix lithium-sulfur electrolyte containing the selenophene additive obtained in the embodiment and the carbon nanotube anode, the diaphragm and the lithium metal cathode loaded with the elemental sulfur are assembled together to form the CR2032 button battery, so as to obtain an experimental group and a control group respectively.

The septum was Celgard-2400 with a diameter of 19 mm.

The electrochemical test is carried out on the lithium sulfur CR2032 button cell (experimental group) containing 0.70mol/L of the phenylselenophenol electrolyte and the lithium sulfur CR2032 button cell (control group) containing the matrix electrolyte, and the liquid phase-mass spectrum (LC-MS), ultraviolet-visible spectrum characterization (UV-Vis), in-situ and ex-situ Raman spectra (Raman), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared absorption spectrum (FT-IR), Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) characterization is carried out on the circulated anode.

Fig. 7 is a voltage-capacity curve of the lithium-sulfur CR2032 coin cells of the experimental group and the control group obtained in the present example at 0.5C magnification, wherein the data marked in the graph are the voltage hysteresis of the cells of the experimental group and the control group, respectively. It can be seen that the voltage hysteresis of the experimental group is only 0.22V relative to the 0.28V of the control group, and the voltage hysteresis is significantly reduced.

Fig. 8 is a graph of long cycle performance of the experimental and control groups of lithium sulfur CR2032 coin cells obtained in this example at 0.5C rate. The maximum discharge specific capacity of the experimental group lithium-sulfur battery is 1436mAh g^-1While the control group was only 800mAh g^-1. After 200 circles, the experimental group can still maintain 1300mAh g^-1The specific capacity and the capacity retention rate are 91.86%, and compared with a control group, the cycle performance of the composite material is obviously improved.

Fig. 9 is a graph of rate performance of the experimental lithium sulfur CR2032 coin cells obtained in this example. At 0.1, 0.2, 0.5, 1.2, 1, 0.5, 0.2 and 0.1C magnificationThe specific discharge capacity of the battery is 1450,1380,1300,1180,1050,1170,1250,1330,1360mAh g respectively^-1. After this time, the cell remained at about 1100mAh g after 70 cycles of recirculation at 0.5C rate^-1The specific capacity of the electrolyte shows that the rate performance of the battery is good.

Fig. 11 is a mass spectrum of the positive electrode of the experimental group of lithium sulfur CR2032 coin cell obtained in this example in the discharged state, and the discharged product lithium phenylselenium (PhSeLi) is detected. Since lithium ions were replaced by hydrogen protons during the detection, phenylselenol (PhSeH) was actually detected, and its mass-to-charge ratio was 157.9600.

FIG. 12 is a mass spectrum of the positive electrode of the experimental group of lithium-sulfur CR2032 coin cell obtained in this example in the charged state, and the charged product C is detected₁₂H₁₀Se₂The mass/charge ratio was 313.9184.

FIG. 13 is a mass spectrum of the positive electrode of the experimental group of lithium-sulfur CR2032 coin cell obtained in this example in the charged state, wherein the charged product C is detected₁₂H₁₀Se₂S, its mass-to-charge ratio is 345.8857. This indicates that phenylselenophenol combines with elemental sulfur during charging to generate PhSeSSePh (DPDPDPSeS) containing Se-S bond, which changes the original redox pathway of lithium-sulfur battery and further reduces the generation and shuttle of polysulfide.

Fig. 14 shows UV-vis tests performed on the positive electrode when the experimental group of lithium sulfur CR2032 coin cells and the control group of lithium sulfur CR2032 coin cells obtained in this example were discharged to 2.1V. It is shown that polysulfide S is detected when the lithium sulfur battery of the control group is discharged to 2.1V₄ ^2-/S₆ ^2-A characteristic peak at 275nm, indicating the production of polysulfides during discharge. When the lithium sulfur battery containing the additive in the experimental group is discharged to 2.1V, no characteristic peak of polysulfide is detected, and the additive is proved to change the charge-discharge process of sulfur simple substance, so that the generation of polysulfide is limited.

FIG. 15 is an in-situ Raman spectrum of the first-cycle discharge process of the lithium sulfur CR2032 coin cell obtained in the experimental group of this example, first, elemental sulfur (S) ₈) Located at 150cm^-1，215cm^-1And 470cm^-1The disappearance of characteristic peaks indicatesS₈The molecule reacts. 340cm^-1The strong peak at the position belongs to Se-S bond, and the phenylselenophenol and S are illustrated before the discharge process starts₈A chemical combination reaction between them and the formation of DPDSeS. The peak intensity continuously decreases during the discharge, and almost completely disappears until the first discharge (2.05V) is completed.

Fig. 16 is an in-situ Raman spectrum of the first-cycle charging of the lithium sulfur CR2032 coin cell of the experimental group obtained in the present example. Se-S bond 340cm^-1The characteristic peak is gradually increased along with the charging, the signal is strongest when the charging is carried out to 2.35V, and the generation of Se-S bonds in the charging process is proved to be consistent with the generation of DPDSSeS detected by the LC-MS in the charging process. Upon charging to 2.41V, the characteristic peak of Se-S bond gradually decreased, indicating the cleavage of Se-S bond. When the charging is carried out to 3.00V, the characteristic peak of Se-S bond is completely disappeared, and the sulfur (S) is simple substance₈) Located at 150cm^-1，215cm^-1And 470cm^-1The appearance of characteristic peak indicates S₈The molecule is regenerated. In-situ Raman analysis shows that sulfur free radicals are captured by the free radicals of the benzene selenium to form Se-S bonds in the charging process, so that the formation and shuttling of polysulfide are avoided; in the later stage of the charging process, the Se-S bond is broken to generate elemental sulfur, and the state is consistent with that at the beginning of discharging, which shows that the charging and discharging process of the battery is highly reversible.

Fig. 17 is an XPS chart of the positive electrode after charging the lithium sulfur CR2032 coin cell of the experimental group obtained in the present example (S2 p). Detection of the Charge product S₈Non-polar S-S bonds (162.2/160.8 eV).

Fig. 18 is an XPS chart of the positive electrode after charging the lithium sulfur CR2032 coin cell of the experimental group obtained in the present example (Se 3 d). Se-Se bonds (165.08/158.59eV) were detected for the charged product PhSeSePh.

Fig. 19 is an XPS (Se 3d) of the positive electrode after discharging the lithium sulfur CR2032 coin cell of the experimental group obtained in the present example. Se-Li bonds (54.73/55.77eV) were detected in the final discharge product lithium phenylselenium (PhSeLi).

FIG. 20 is a FT-IR spectrum of phenylselenol and a reaction mixture of elemental sulfur and phenylselenol. 2300cm^-1The disappearance of the Se-H signal indicates that the phenylselenol reacts with elemental sulfur and the content is reduced.

FIG. 21 is a Raman spectrum of elemental sulfur and phenylselenol feedstocks and reaction mixtures thereof. Elemental sulfur (S)₈) Raman shift of (2) at 150cm^-1，215cm^-1And 470cm^-1. The Raman shift of the sulfur simple substance in the reaction mixture disappears and is positioned at 360cm^-1The occurrence of a Raman shift at Se-S confirms the formation of a molecule containing a Se-S bond. The results are consistent with the actual battery cycling PhSeSSePh (DPDSeS) generation detected by the LC-MS.

Fig. 22 is an SEM image of the positive electrode after charging the lithium sulfur CR2032 coin cell of the experimental group obtained in the present example. The charged product is uniformly distributed in the carbon nano tube network, is tightly attached to the periphery of the carbon nano tube and presents a three-dimensional globular deposition form.

Fig. 23 is an SEM image of the positive electrode after discharging the lithium sulfur CR2032 coin cell of the experimental group obtained in the present example. It can be seen that the charged product has similar appearance and is dispersedly and uniformly deposited on the carbon nano tube in a small ball shape.

Fig. 24 is a TEM image of the positive electrode of the experimental group obtained in this example after charging the lithium sulfur CR2032 coin cell, which is consistent with the SEM image in morphology, and is a spherical three-dimensional deposit with uniform distribution.

Example 5

The lithium-sulfur battery electrolyte containing the phenylselenol additive comprises an ether solvent, lithium salt and the additive; wherein the ether solvent is a mixed solution of DOL and DME with the volume ratio of 1:1, and the lithium salt LiTFSI and the LiNO are₃LiTFSI concentration of 1mol/L, LiNO₃The concentration is 0.15mol/L, the additive is benzene selenol (PhSeH), and the concentration is 0.10 mol/L.

Here, it should be noted that, when the concentration of the phenylselenol in the pouch battery is too high, the formation of the lithium negative electrode SEI layer of the pouch battery is not facilitated to a certain extent, and therefore, compared with the button battery, the reduction of the concentration of the phenylselenol is favorable for improving the long cycle performance of the pouch battery. In the soft package battery, the applicable concentration of the phenylselenol is 0.05-0.30 mol/L. In practical applications, the optimum concentration of the phenylselenol should be selected according to the battery performance.

And injecting the electrolyte into the lithium-sulfur soft package battery to assemble the lithium-sulfur soft package battery. The pouch cells were purchased from Hunan vision New Material Technology co., LTD, and had a total sulfur loading of 1.2g, and were used for testing only in the examples.

Fig. 10 is a graph of the cycle performance of the lithium sulfur pouch battery containing the 0.10mol/L phenylselenol additive obtained in this example at 50mA current. The maximum discharge capacity of the battery is 1398 mAh.

It is apparent that the above embodiments are only examples for clearly illustrating, and are not limiting to the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. This need not be, nor should it be exhaustive of all embodiments. And obvious variations or modifications are therefore intended to be included within the scope of the invention as claimed.

Claims

1. The lithium-sulfur battery electrolyte containing the phenylselenol additive is characterized by comprising an ether solvent, lithium salt and the additive, wherein the additive is phenylselenol.

2. The electrolyte of claim 1, wherein the concentration of the phenylselenophenol in the electrolyte is 0.05-1.0 mol/L.

3. The electrolyte according to claim 1, wherein the ether solvent is a mixture of DME and DOL, and the volume ratio of DME to DOL is (0.8-1.2): 1.

4. The electrolyte of claim 1, wherein the lithium salt is LiTFSI and LiNO₃The mixture, wherein the concentration of LiTFSI is 1.0-1.5 mol/L, LiNO₃The concentration of (b) is 0.15 to 0.25 mol/L.

5. A lithium-sulfur battery comprising a positive electrode material, a negative electrode material, a separator and the lithium-sulfur battery electrolyte containing a phenylselenol additive of any one of claims 1-4.

6. The lithium sulfur battery of claim 5, wherein the positive electrode material is multi-walled carbon nanotube paper loaded with elemental sulfur.

7. The lithium sulfur battery of claim 6 wherein the sulfur loading is 0.88 to 1.15mg cm^-2。

8. The lithium sulfur battery of claim 5, wherein the negative electrode material is a lithium metal sheet; the septum was Celgard 2400.

9. The application of the phenylselenol as an additive in the electrolyte of the lithium-sulfur battery.

10. Use of a lithium-sulfur battery electrolyte containing a phenylselenol additive as claimed in any one of claims 1 to 4 in a lithium-sulfur battery, wherein: