High-performance lithium-containing organic sulfur electrode material and preparation method of integrated flexible electrode

Abstract

The present invention provides a high-performance lithium-containing organic sulfur electrode material and a preparation method of an integrated flexible electrode. According to the present invention, 1,3-diisopropenyl benzene with diene bonds and Li2S6 are used as precursors to react to generate the lithium-containing organic sulfide Poly (Li2S6-r-DIB) through an in-situ polymerization method. The synthesized lithium-containing organic sulfide Poly (Li2S6-r-DIB) can be directly attached to a flexible conductive carbon cloth to prepare the integrated flexible electrode due to its good viscosity when heated to a certain temperature. The obtained flexible electrode has the advantages of high capacity, high flexibility, stable structure and the like.

Claims

1. A preparation method of a high-performance lithium-containing organic sulfur electrode material, characterized by comprising: Step 1, taking Li.sub.2S and sublimed sulfur as raw materials and tetrahydrofuran as a medium, reacting the Li.sub.2S and the sublimed sulfur in a molar ratio of 1:5 for 24 hours under an inert gas environment of 40-60° C. to obtain a Li.sub.2S.sub.6 solution in the THF; Step 2, adding 1, 3-diisopropenyl benzene (DIB) into the Li.sub.2S.sub.6 solution in the THF obtained in step 1, and reacting for 30-60 min at 130-150° C. to cause polymerization to obtain a lithium-containing organic sulfide Poly (Li.sub.2S.sub.6-r-DIB); and Step 3, heating the lithium-containing organic sulfide Poly (Li.sub.2S.sub.6-r-DIB) solution obtained in step 2 to 70-80° C., and evaporating and separating the THF solvent under vacuum to finally obtain an asphaltic-like black lithium-containing organic sulfide Poly (Li.sub.2S.sub.6-r-DIB).

2. The preparation method of the high-performance lithium-containing organic sulfur electrode material of claim 1, characterized in that, the mass fraction of 1, 3-diisopropenyl benzene is one of 5%, 10%, 15%, 20%, 25%, 30%, and 50%.

3. A preparation method of an integrated flexible electrode, characterized by comprising: heating the black lithium-containing organic sulfide Poly (Li.sub.2S.sub.6-r-DIB) obtained by the preparation method of claim 2 to 50-70° C., and directly and uniformly coating onto a flexible conductive cloth by a coating method to obtain an integrated organic sulfur electrode.

4. The preparation method of the integrated flexible electrode of claim 3, characterized in that the conductive cloth is a carbon fiber braid.

5. An integrated flexible electrode, characterized by being prepared by a preparation method of claim 4.

6. An integrated flexible electrode, characterized by being prepared by a preparation method of claim 3.

7. An integrated flexible electrode, characterized by being prepared by a preparation method of claim 2.

8. An integrated flexible electrode, characterized by being prepared by a preparation method of claim 1.

9. A preparation method of an integrated flexible electrode, characterized by comprising: heating the black lithium-containing organic sulfide Poly (Li.sub.2S.sub.6-r-DIB) obtained by the preparation method of claims 1 to 50-70° C., and directly and uniformly coating onto a flexible conductive cloth by a coating method to obtain an integrated organic sulfur electrode.

10. The preparation method of the integrated flexible electrode of claim 9, characterized in that the conductive cloth is a carbon fiber braid.

11. An integrated flexible electrode, characterized by being prepared by a preparation method of claim 10.

12. An integrated flexible electrode, characterized by being prepared by a preparation method of claim 9.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows curves of capacity and charge-discharge efficiency of a battery manufactured by using a lithium-containing organic sulfide integrated flexible electrode as a cathode and a pure lithium sheet as an anode according to an embodiment of the present invention.

(2) FIG. 2 shows a curve of discharge capacity at charge-discharge current densities of 0.1 A g.sup.−1 to 2 A g.sup.−1 of a battery manufactured by using a lithium-containing organic sulfide integrated flexible electrode as a cathode and a pure lithium sheet as an anode according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(3) The technical scheme adopted by the present invention will be further described with reference to the schematic drawings.

(4) Example 1: a high-performance lithium-containing organic sulfur electrode material was prepared by a method including: 1) Li.sub.2S and sublimed sulfur were taken as raw materials and tetrahydrofuran as a medium, and Li.sub.2S and sublimed sulfur were reacted in a molar ratio of 1:5 for 24 hours under an inert gas environment of 40-60° C. to obtain a Li.sub.2S.sub.6 solution in THF;

(5) 2) a certain amount of 1,3-diisopropenyl benzene (DIB) was added into the Li.sub.2S.sub.6 solution in THF prepared in step 1, and a reaction was occurred for 30-60 min at 130-150° C. to cause polymerization to obtain a lithium-containing organic sulfide Poly (Li.sub.2S.sub.6-r-DIB), wherein the mass fraction of the DIB can be adjusted arbitrarily within a certain range;

(6) 3) the lithium-containing organic sulfide Poly (Li.sub.2S.sub.6-r-DIB) solution prepared in step 2 was heated to 70-80° C., and the THF solvent was evaporated and separated under vacuum to finally obtain an asphaltic-like black lithium-containing organic sulfide Poly (Li.sub.2S.sub.6-r-DIB), i.e. the high-performance lithium-containing organic sulfur electrode material.

(7) Example 2: an integrated flexible electrode was prepared by a method on the basis of the method of Example 1 and further including:

(8) 4) The lithium-containing organic sulfide Poly (Li.sub.2S.sub.6-r-DIB) prepared in step 3 of Example 1 was heated to 50-70° C. to exhibit a good adhesion, and it was directly and uniformly coated on a flexible conductive carbon cloth by a coating method to prepare an integrated organic sulfur electrode having excellent flexibility, and the prepared electrode doesn't require the heating of a binder and conductive carbon.

(9) The conductive carbon cloth in this example is one of commercial carbon fiber braids.

(10) The DIB in this example shows different physical and electrochemical properties with different contents of 5%, 10%, 15%, 20%, 25%, 30%, 50%, and one having the best electrical properties is one of them.

(11) The sulfur content of lithium-containing organic sulfide was measured by an elemental analyzer under the model of Vario EL Cube manufactured by a Germany company. The structure characterization through a nuclear magnetic resonance apparatus under the model of AV500 MHz manufactured by Bruker Advance in Germany can prove that the polymerization reaction of Li.sub.2S.sub.6 and DIB occurs, and the sulfur atoms are fixed in the polymer in the form of chemical bonds.

(12) The electrode material of the example of the present invention was made into a cathode of a lithium battery, which was then used as a test object, and an electrochemical performance test was carried out on the test object by using a multi-channel battery tester under the model of CT2001A manufactured by Wuhan LAND Electronic Co., Ltd; the measured charge-discharge voltage window is 1.5-3 V, the charge-discharge current is 100 mA g.sup.−1, and the measured capacity and charge-discharge efficiency curves are shown in FIG. 1, wherein the horizontal axis of FIG. 1 is a cycle number axis, the right vertical axis of FIG. 1 is a coulomb efficiency number axis, the left vertical axis of FIG. 1 is a capacity number axis, curve S1 of FIG. 1 is a coulomb efficiency curve, and curve S2 in FIG. 1 is a capacity curve. It can be seen from FIG. 1 that the first discharge capacity of the test object is about 1200 mAh g.sup.−1. After 140 charge-discharge cycles, the capacity of the test object is stabilized at 760.9 mAh g.sup.−1, and the coulombic efficiency is always maintained above 97%. Therefore, the test object has high capacity and excellent cycle stability.

(13) The electrode material of the example of the present invention was made into a cathode of a lithium battery, which was then used as a test object, and an electrochemical performance test was carried out on the test object by using a multi-channel battery tester under the model of CT2001A manufactured by Wuhan LAND Electronic Co., Ltd; and the measured discharge capacity curve under the charge-discharge current densities of 0.1 A g.sup.−1-2.0 A g.sup.−1 is as shown in FIG. 2. It can be seen from FIG. 2 that the test object still has a high capacity at different current densities. The battery still has a capacity of 720 mAh g.sup.−1 especially at a current density as high as 2.0 A g.sup.−1, and then the reduced current density can be completely restored to a capacity of about 1100 mAh g.sup.−1.

(14) In summary, according to the present invention, 1,3-diisopropenyl benzene with diene bonds and Li.sub.2S.sub.6 are used as precursors to react to generate the lithium-containing organic sulfide Poly (Li.sub.2S.sub.6-r-DIB) through an in-situ polymerization method. The synthesized lithium-containing organic sulfide Poly (Li.sub.2S.sub.6-r-DIB) can be directly attached to a flexible conductive carbon cloth to prepare the integrated flexible electrode due to its good viscosity when heated to a certain temperature. The obtained flexible electrode has the advantages of high capacity, high flexibility, stable structure and the like. As the traditional S/C composite material is used as the cathode of the lithium-sulfur battery, a large amount of conductive agent needs to be added, resulting in a low volume specific capacity, and the electrode material through the physical coating will cause the structure to collapse until failure during the charge and discharge cycles; on the other hand, organic sulfur as a cathode material is easily dissolved in an ether electrolyte, so that a part of lithium ions are required to participate in the formation of the SEI film in the initial charge-discharge cycle, resulting a larger initial capacity loss. According to the lithium-containing organic sulfide flexible electrode prepared by the present invention, due to the three-dimensional conductive carbon cloth as a substrate and the rheological property of the material itself, the addition of an additional conductive agent and a bonding agent is not needed, which greatly improves the volume specific capacity of the battery. Meanwhile, due to the introduction of lithium ions, the transmission and migration of lithium ions of the anode are reduced in the initial circulation process, so that the initial cycle capacity can be basically maintained. The lithium-containing organic sulfide electrode material and the integrated electrode obtained by the method have the characteristics of good flexibility, high specific capacity and good cycle stability.

(15) The above are only preferred embodiments of the present invention, and do not play any limiting effect on the present invention. Any person skilled in the art, without departing from the technical solution of the present invention, can make any form of equivalent substitution or modification of the technical solution and the technical content disclosed in the present invention, which still fall within the scope of the present invention without departing from the technical solution of the present invention.