Ferroelectric material modified all-solid-state sulfur composite electrode material as well as preparation method and application thereof

Abstract

The invention discloses a ferroelectric material modified all-solid-state sulfur composite electrode material and a preparation method and application thereof, the ferroelectric material modified all-solid-state sulfur composite electrode material comprises the following raw materials by mass: 10%-30% of an active sulfur substance, 10%-20% of an electronic conductor, 1%-10% of a lithium supplement agent, 40%-60% of a sulfide electrolyte and 1%-10% of a ferroelectric material; the ferroelectric material is added into the lithium-sulfur composite material and serves as a sulfur composite positive electrode in the all-solid-state lithium-sulfur battery, the ferroelectric material generates a built-in electric field due to self polarization, the lithium ion concentration between the positive electrode of the all-solid-state lithium-sulfur battery and a solid electrolyte is readjusted, dissociation of a lithium salt in the solid electrolyte is promoted, and the lithium-sulfur composite material is used as a sulfur composite positive electrode in the all-solid-state lithium-sulfur battery. And the formation of a space charge layer at the interface of the positive electrode and the solid electrolyte of the all-solid-state lithium-sulfur battery is inhibited, so that the transmission efficiency of lithium ions is improved, the battery obtains higher charge-discharge specific capacity and better cycle stability, and a brand new reference is provided for the development of the all-solid-state lithium-sulfur battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional materials, relates to an all-solid-state sulfur composite electrode material, and particularly relates to an all-solid-state sulfur composite electrode material modified by a ferroelectric material, and a preparation method and application thereof. Background Art

[0002] All-solid-state lithium-based batteries have received wide attention due to their excellent safety. Lithium-sulfur batteries have the advantages of high theoretical specific capacity (1675 mAh g -1 ), high theoretical energy density (2600 Wh kg -1 ), rich sulfur resource reserves, low electrode cost, environmental friendliness, etc., and have become one of the ideal choices for a new generation of energy storage devices.

[0003] However, complex interface problems pose significant limitations to the development and practical application of all-solid-state batteries. Problems such as interface side reactions, dendrite formation, and charge space layers seriously hinder the effective transport of ions, leading to direct battery failure. In particular, the problem of the formation of a space charge layer caused by the large chemical difference between the carriers at the positive sulfur and the solid electrolyte restricts the ion migration efficiency. Therefore, it is particularly important to redistribute the lithium ion concentration between the positive electrode and the solid electrolyte to alleviate the formation of the space charge layer. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide an all-solid-state sulfur composite electrode material modified by a ferroelectric material, and a preparation method and application thereof. By adding a ferroelectric material, the polarization generates an internal electric field to re-adjust the lithium ion concentration between the positive electrode and the solid electrolyte of the all-solid-state lithium-selenium-sulfur battery, inhibits the formation of a space charge layer at the interface between the positive electrode and the solid electrolyte of the all-solid-state lithium-sulfur battery, and enables the battery to obtain higher charge-discharge specific capacity and better cycle stability.

[0005] In order to achieve the above purpose, the present invention adopts the following technical solutions to achieve:

[0006] An all-solid-state sulfur composite electrode material modified by a ferroelectric material, the raw materials are in mass percentages, including 10% - 30% of active sulfur substances, 10% - 20% of electronic conductors, 1% - 10% of lithium supplement agents, 40% - 60% of sulfide electrolytes, and 1% - 10% of ferroelectric materials.

[0007] The present invention also has the following technical features:

[0008] Preferably, the active sulfur substance includes any one of elemental sulfur, lithium disulfide, and hydrogen sulfide.

[0009] Preferably, the electronic conductor includes a mixture of any proportion of two of BP2000, CNTs, and Super P.

[0010] Preferably, the lithium supplement includes any one of LiI, LNO, and LFO.

[0011] Preferably, the sulfide electrolyte includes Li 10 GeP 2 S 12 、Li 6 PS 5 Cl and Li 7 P 3 Any one of S11.

[0012] Preferably, the ferroelectric material includes any one of barium titanate, strontium titanate, barium strontium titanate, lithium niobate, and calcium copper titanate.

[0013] The present invention also protects a method for preparing a ferroelectric material-modified all-solid-state sulfur composite electrode material as described above, including the following steps:

[0014] Step 1: Under an argon atmosphere, take the active sulfur substance and the electronic conductor according to the mass ratio and ball mill for 8 - 24 h to obtain powder A. Dissolve powder A in a carbon disulfide solution, stir evenly, and then place it in a fume hood to air dry to obtain powder B;

[0015] Step 2: Under an argon atmosphere, take the sulfide electrolyte, the ferroelectric material, and the lithium supplement according to the mass ratio and manually grind them together with composite material B for 30 - 60 min to obtain composite positive electrode material C.

[0016] Preferably, the ball-to-material ratio of the ball milling in Step 1 is 30:1, and the ball milling speed is 500 - 3000 rpm / min.

[0017] The present invention also protects the application of a ferroelectric material-modified all-solid-state sulfur composite electrode material as described above as a sulfur composite positive electrode in an all-solid-state lithium-sulfur battery.

[0018] Compared with the prior art, the present invention has the following technical effects:

[0019] The present invention adds a ferroelectric material to a lithium-sulfur composite material, which serves as a sulfur composite cathode in an all-solid-state lithium-sulfur battery. Due to its own polarization, the ferroelectric material generates an internal electric field, which readjusts the lithium ion concentration between the cathode of the all-solid-state lithium-sulfur battery and the solid electrolyte, promotes the dissociation of the lithium salt in the solid electrolyte, and inhibits the formation of a space charge layer at the interface between the cathode of the all-solid-state lithium-sulfur battery and the solid electrolyte. Thereby, the transfer efficiency of lithium ions is improved, and the battery obtains a higher charge-discharge specific capacity and better cycle stability. The solid-state full battery assembled with this cathode obtains a high initial discharge specific capacity of 1267 mAh g -1 and a capacity retention rate higher than 85% after 95 cycles, providing a new reference for the development of all-solid-state lithium-sulfur batteries. Description of the Drawings

[0020] Figure 1 X-ray diffraction analysis pattern of the composite material prepared in Example 1;

[0021] Figure 2 SEM image and EDS of the composite material in Example 1;

[0022] Figure 3 Impedance of the all-solid-state lithium-sulfur batteries before cycling in Example 1 and Comparative Example 1;

[0023] Figure 4 Charge-discharge curves of the all-solid-state lithium-sulfur battery in Example 1 at the 1st, 3rd, 5th, 10th, and 15th cycles;

[0024] Figure 5 Capacity and Coulomb efficiency diagrams of the all-solid-state lithium-sulfur battery in Example 1 under long cycling;

[0025] Figure 6 Capacity and Coulomb efficiency diagrams of the all-solid-state lithium-sulfur battery in Comparative Example 1 under long cycling;

[0026] Figure 7 Capacity and Coulomb efficiency diagrams of the all-solid-state lithium-sulfur battery in Example 1 under long cycling at 60 °C. Detailed Embodiments

[0027] The following further elaborates on the specific content of the present invention in conjunction with examples.

[0028] Those skilled in the art can obtain the raw materials used in the present invention through the preparation or purchase of published literature;

[0029] In the following examples, BP2000 is BLACK PEARLS2000 carbon black, and the manufacturer is Guangdong Zhuguang New Energy Technology Co., Ltd.;

[0030] The CNTs are 99% hexagonal crystal system carbon nanotubes, and the manufacturer is Shenzhen Deheng Technology Co., Ltd.;

[0031] Super P is small particle conductive carbon black, and the manufacturer is Shenzhen Deheng Technology Co., Ltd.;

[0032] Li 10 GeP 2 S 12 (LGPS), Li 6 PS 5 Cl (LPSCl), Li 7 P 3 S 11 (LPS) is manufactured by Hubei Solide New Energy Technology Co., Ltd.;

[0033] LiI, LNO (LiNiO 2 ), LFO (Li 5 FeO 4 ) is manufactured by Sinopharm Chemical Reagent Co., Ltd.;

[0034] Barium titanate, strontium titanate, strontium barium titanate, lithium niobate and calcium copper titanate are manufactured by Shanghai Macklin Biochemical Co., Ltd.

[0035] Example 1

[0036] This example provides a ferroelectric material modified all-solid-state sulfur composite electrode material, and the raw material components and their mass percentage ratios are S: LGPS: BP2000: CNTs: LiI: BaTiO 3 = 10:50:10:10:10:10;

[0037] The preparation method steps are as follows:

[0038] Step 1: Under an argon atmosphere, take S, BP2000, and CNTs and perform ball milling to obtain powder A. The ball-to-material ratio is 30:1, the ball milling speed is 1000 rpm / min, and the ball milling time is 12 h; dissolve powder A in carbon disulfide solution, stir for 10 min until uniform, and finally place the stirred solution in a fume hood to air dry for 48 h to obtain powder B;

[0039] Step 2: Under an argon atmosphere, weigh LGPS, LiI, and BaTiO according to the mass ratio 3 Manually grind it together with composite material B for 30 min to obtain a ferroelectric material modified all-solid-state sulfur composite electrode material.

[0040] Test the ferroelectric material modified all-solid-state sulfur composite electrode material prepared in Example 1, and the results are as follows:

[0041] Figure 1 X-ray diffraction analysis pattern of the composite material in Example 1; Figure 1 As can be seen from [Figure / Graph] Figure 1 , the composite cathode material in Example 1 has typical characteristic peaks of elemental sulfur and BaTiO 3 , indicating that the preparation method of the composite cathode material is feasible.

[0042] Figure 2 SEM image and EDS map of the composite material in Example 1; Figure 2 As can be seen from [Figure / Graph] Figure 2 , the particle size is relatively uniform before cycling, and different elements can be observed in each part, indicating that various materials are evenly distributed.

[0043] The ferroelectric material-modified all-solid-state sulfur composite electrode material prepared in Example 1 was used to prepare an all-solid-state lithium-sulfur battery, and the preparation method is as follows:

[0044] Use a scraper to repeatedly remove the black uneven area on the surface of the lithium sheet to make it flat and shiny, and use a hole punch to cut it into a lithium sheet with a diameter of 0.8 mm;

[0045] Use a hole punch to cut the purchased indium sheet into a thin sheet with a diameter of 1 mm, place the cut lithium sheet on the indium sheet and press it flat;

[0046] Weigh 100 - 120 mg of LGPS electrolyte into a polytetrafluoroethylene solid-state battery mold, apply a force of 2.0 Tons and maintain it for 2 min; then weigh 3 - 5 mg of composite cathode material C and place it above the LGPS, and gently rotate it with the ejector rod of the mold to spread it evenly on the surface, apply a force of 2.0 Tons and maintain it for 2 min; finally, place the surface-treated lithium-indium thin sheet below the LGPS, blow off the uncompacted powder on the surface with an ear syringe, apply a force of 0.5 Tons and maintain it for about 15 s to obtain an all-solid-state lithium-sulfur battery; in order to achieve the effect of applying a constant voltage to the battery, a force of 0.5 Tons needs to be applied to the assembled battery.

[0047] The preparation process of the all-solid-state lithium-sulfur battery is carried out in a glove box filled with inert gas Ar;

[0048] Place the assembled all-solid-state lithium-sulfur battery at room temperature and let it stand for more than 2 h, and then conduct tests.

[0049] Example 2

[0050] This example provides a ferroelectric material-modified all-solid-state sulfur composite electrode material, and the raw material components and their mass percentage ratios are Li 2 S:LPSCl:BP2000:Super P:LNO:SrTiO 3 =29:40:10:10:10:1;

[0051] The preparation method steps are as follows:

[0052] Step 1: Under an argon atmosphere, take Li 2 S and BP2000, Super P and perform ball milling to obtain powder A. The ball-to-material ratio is 30:1, the ball milling speed is 500 rpm / min, and the ball milling time is 24 h; dissolve powder A in a carbon disulfide solution, stir for 12 h until uniform, and finally place the stirred solution in a fume hood to air dry for 24 h to obtain powder B;

[0053] Step 2: Under an argon atmosphere, weigh LPSCl, LNO and SrTiO according to the mass ratio 3 And grind it together with composite material B by hand for 30 min to obtain a ferroelectric material-modified all-solid-state sulfur composite electrode material.

[0054] Example 3

[0055] This example provides a ferroelectric material-modified all-solid-state sulfur composite electrode material, and the raw material components and their mass percentage ratios are H 2 S: LPS: CNTs: Super P: LFO: BaO 6 SrTi 2 = 30:54:8:2:1:5;

[0056] The preparation method steps are as follows:

[0057] Step 1: Under an argon atmosphere, take H2S and CNTs, Super P and perform ball milling to obtain powder A. The ball-to-material ratio is 30:1, the ball milling speed is 3000 rpm / min, and the ball milling time is 8 h; dissolve powder A in a carbon disulfide solution, stir for 18 h until uniform, and finally place the stirred solution in a fume hood to air dry for 48 h to obtain powder B;

[0058] Step 2: Under an argon atmosphere, weigh LPS, LFO and BaO according to the mass ratio 6 SrTi 2 And grind it together with composite material B by hand for 50 min to obtain a ferroelectric material-modified all-solid-state sulfur composite electrode material.

[0059] Example 4

[0060] This example provides a ferroelectric material-modified all-solid-state sulfur composite electrode material, and the raw material components and their mass percentage ratios are S: LGPS: BP2000: CNTs: LiI: LiNbO 3 = 20:55:10:5:3:7;

[0061] The preparation method steps are as follows:

[0062] Step 1: Under an argon atmosphere, take S, BP2000, and CNTs and perform ball milling to obtain powder A. The ball-to-material ratio is 30:1, the ball milling speed is 2000 rpm / min, and the ball milling time is 10 h. Dissolve powder A in a carbon disulfide solution and stir for 15 h until homogeneous. Finally, place the stirred solution in a fume hood and air-dry it for 36 h to obtain powder B.

[0063] Step 2: Under an argon atmosphere, weigh LGPS, LiI, and LiNbO according to the mass ratio 3 And grind it manually with composite material B for 60 min to obtain a ferroelectric material-modified all-solid-state sulfur composite electrode material.

[0064] Example 5

[0065] This example provides a ferroelectric material-modified all-solid-state sulfur composite electrode material. The raw material components and their mass percentage ratios are S: LGPS: BP2000: CNTs: LiI: CaCuO 6 Ti 2 = 15: 60: 5: 10: 5: 5;

[0066] The preparation method steps are as follows:

[0067] Step 1: Under an argon atmosphere, take S, BP2000, and CNTs and perform ball milling to obtain powder A. The ball-to-material ratio is 30:1, the ball milling speed is 1500 rpm / min, and the ball milling time is 15 h. Dissolve powder A in a carbon disulfide solution and stir for 12 h until homogeneous. Finally, place the stirred solution in a fume hood and air-dry it for 48 h to obtain powder B.

[0068] Step 2: Under an argon atmosphere, weigh LGPS, LiI, and CaCuO according to the mass ratio 6 Ti 2 And grind it manually with composite material B for 30 min to obtain a ferroelectric material-modified all-solid-state sulfur composite electrode material.

[0069] Comparative Example 1

[0070] For the all-solid-state sulfur composite electrode material of Comparative Example 1, the raw material components and their mass percentage ratios are S: LGPS: BP2000: CNTs: LiI = 10: 60: 10: 10: 10, and the remaining steps are the same as those in Example 1.

[0071] Comparative Example 2

[0072] For the all-solid-state sulfur composite electrode material of Comparative Example 2, the raw material components and their mass percentage ratios are S: LPSCL: BP2000: CNTs: LiI = 10: 60: 10: 10: 10, and the remaining steps are the same as those in Example 1.

[0073] Figure 3 Impedance diagrams of the all-solid-state lithium-sulfur batteries before cycling for Example 1 and Comparative Example 1; From Figure 3 it can be seen that for the battery with the addition of the ferroelectric material BaTiO 3 , due to the reasonable regulation of the lithium-ion concentration at the interface between the positive electrode and the electrolyte, a smaller resistance is obtained, and it has better charge transfer kinetics.

[0074] Figure 4 Charge-discharge curves of the all-solid-state lithium-sulfur battery of Example 1 at the 1st, 3rd, 5th, 10th, and 15th cycles; From Figure 4 it can be seen that due to the addition of the ferroelectric material BaTiO 3 , the polarization of the battery in the first cycle is 680 mV, but the polarization continuously decreases as the reaction proceeds. And the initial discharge specific capacity is 1267 mAh g -1 . Compared with the lithium-sulfur battery without the addition of the ferroelectric material, the polarization is smaller and the initial discharge specific capacity is higher, indicating that the addition of the ferroelectric material BaTiO 3 can effectively improve the performance of the battery.

[0075] Figure 5 Capacity and Coulomb efficiency diagrams of the all-solid-state lithium-sulfur battery of Example 1 under long cycling; From Figure 5 it can be seen that due to the addition of the ferroelectric material BaTiO 3 , after 95 cycles, the overall capacity retention rate of the battery reaches 85%; the average Coulomb efficiency exceeds 95%, which also proves the stability of the battery under long-term cycling.

[0076] Figure 6 Capacity and Coulomb efficiency diagrams of the all-solid-state lithium-sulfur battery of Comparative Example 1 under long cycling; From Figure 6 it can be seen that due to the addition of the ferroelectric material BaTiO 3 , after 95 cycles, the overall capacity retention rate of the battery reaches 85%, and the initial discharge capacity reaches 1267 mAh g -1 . The capacity retention rate of the lithium-sulfur battery without the addition of the ferroelectric material is only 67% after 95 cycles, and its initial discharge capacity is lower, only 677 mAh g -1 . This further illustrates the important role of the addition of the ferroelectric material BaTiO 3 in improving the performance of the battery under long cycling.

[0077] Figure 7 Capacity and Coulomb efficiency diagrams of the all-solid-state lithium-sulfur battery of Example 1 under long cycling at 60 °C; From Figure 7 it can be seen that under the constant temperature condition of 60 °C, the battery still has excellent electrochemical performance and long cycling stability. After 300 cycles, it still has a capacity of more than 300 mAh g -1The discharge specific capacity, which proves the feasibility of the development of this cathode material under extreme conditions and provides the possibility for the development of new cathode materials for all-solid-state lithium-sulfur batteries.

Claims

1. A ferroelectric material modified all-solid sulfur composite electrode material, characterized in that: The raw materials include, by mass percentage, 10% to 30% of active sulfur material, 10% to 20% of electronic conductor, 1% to 10% of lithium supplement, 40% to 60% of sulfide electrolyte and 1% to 10% of ferroelectric material.

2. The all-solid-state sulfur composite electrode material modified by ferroelectric material according to claim 1, characterized in that: The active sulfur includes any one of elemental sulfur, lithium disulfide and hydrogen sulfide.

3. The all-solid-state sulfur composite electrode material modified by ferroelectric material according to claim 1, characterized in that: The electronic conductor comprises a mixture of two of BP2000, CNTs and Super P in any proportion.

4. The all-solid-state sulfur composite electrode material modified by ferroelectric material according to claim 1, characterized in that: The lithium supplement includes any one of LiI, LNO and LFO.

5. The all-solid-state sulfur composite electrode material modified by ferroelectric material according to claim 1, characterized in that: The sulfide electrolyte includes Li 10 GeP2S 12 , Li6PS5Cl and Li7P3S11.

6. The all-solid-state sulfur composite electrode material modified by ferroelectric material according to claim 1, characterized in that: The ferroelectric material includes any one of barium titanate, strontium titanate, barium strontium titanate, lithium niobate and calcium copper titanate.

7. A method for preparing a ferroelectric material modified all-solid sulfur composite electrode material according to any one of claims 1 to 6, characterized in that: The following steps are involved: Step 1: Under an argon atmosphere, take an active sulfur material and an electronic conductor according to a mass ratio and ball-mill for 8 to 24 hours to obtain powder A, dissolve powder A in a carbon disulfide solution, stir evenly, and then air-dry in a fume hood to obtain powder B; Step 2: Under an argon atmosphere, take the sulfide electrolyte, ferroelectric material and lithium supplement agent according to the mass ratio and grind them together with the composite material B by hand for 30 to 60 minutes to obtain the composite positive electrode material C.

8. The method for preparing the ferroelectric material modified all-solid sulfur composite electrode material according to claim 7, characterized in that: The ball-to-material ratio of the ball mill in step 1 is 30:1, and the ball mill rotation speed is 500-3000 rpm / min.

9. Use of the ferroelectric material modified all-solid-state sulfur composite electrode material as claimed in any one of claims 1 to 6 as a sulfur composite positive electrode in an all-solid-state lithium-sulfur battery.

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