阅读说明：本技术 苯并二噻吩-4, 8-二酮在锂氧电池中的应用及利用其得到的锂氧电池 (Application of benzodithiophene-4, 8-diketone in lithium-oxygen battery and lithium-oxygen battery obtained by using same ) 是由 赵勇 刘肖 宋晓胜 何晓峰 韩庆 王�华 于 2019-08-02 设计创作，主要内容包括：本申请公开一种苯并二噻吩-4,8-二酮在锂氧电池中的应用及利用其得到的锂氧电池,苯并[1,2-b:4,5-b’]二噻吩-4,8-二酮(BDTD)应用于锂氧电池中,放电时BDTD首先从电极表面接受电子变成BDTD<Sup>-</Sup>,然后与锂离子结合形成BDTDLi,BDTDLi还原溶液中的氧气生成BDTDLiO<Sub>2</Sub>中间体,BDTDLiO<Sub>2</Sub>被另一分子的BDTDLi还原或两分子BDTDLiO<Sub>2</Sub>歧化生成Li<Sub>2</Sub>O<Sub>2</Sub>,同时再生BDTD继续从电极表面得到电子还原溶液中氧气,如此反复。在使用不同碳和金属氧化物为正极组装的锂空气电池中,BDTD的存在使电池容量和循环性能提高数倍以上,是迄今为止最先进的可溶性氧化还原介质。(The application discloses application of benzodithiophene-4, 8-diketone in lithium oxygen battery and lithium oxygen battery obtained by using same, wherein benzo [1,2-b:4,5-b']Dithiophene-4, 8-dione (BDTD) is applied to a lithium-oxygen battery, and when the BDTD discharges, the BDTD firstly accepts electrons from the surface of an electrode to change into the BDTD ‑ Then combining with lithium ion to form BDTDLi, BDTDLi reducing oxygen in solution to form BDTDLiO 2 Intermediate, BDTDLiO 2 Reduced by another molecule of BDTDLi or two molecules of BDTDLiO 2 Disproportionation to produce Li 2 O 2 And meanwhile, regenerating BDTD to continuously obtain oxygen in the electron reduction solution from the surface of the electrode, and repeating the steps. In lithium air batteries assembled using different carbons and metal oxides as the positive electrode, the presence of BDTD increased the battery capacity and cycling performance by more than a few times, being the most advanced soluble redox mediator to date.)

1. A benzo [1,2-b:4,5-b ' ] dithiophene-4, 8-dione lithium oxygen battery electrolyte is characterized in that the preparation process comprises the step of dissolving benzo [1,2-b:4,5-b ' ] dithiophene-4, 8-dione and lithium salt in an organic solvent to obtain the electrolyte, wherein the concentrations of the benzo [1,2-b:4,5-b ' ] dithiophene-4, 8-dione and lithium salt in the organic solvent are respectively 0.05 ~ 25 mmol/L and 1 ~ 4 mol/L, the lithium salt is one or more of lithium hexafluorophosphate, lithium tetrafluorophosphate, lithium perchlorate, lithium hexafluoroarsenate (V), lithium trifluoromethanesulfonate, lithium bis (trifluoromethylsulfonyl) imide, lithium tris (trifluoromethylsulfonyl) methyl or lithium bis (oxalato borate, and the organic solvent is one or more of ethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, N, N-dimethylacetamide, dimethyl sulfoxide, butanone, dioxolane, tetrahydrofuran or 1-methylimidazole.

2. The method for preparing the lithium-oxygen battery by using the benzo [1,2-b:4,5-b '] dithiophene-4, 8-diketone lithium-oxygen battery electrolyte as claimed in claim 1 is characterized in that lithium is selected as a negative electrode, a conductive substrate loaded with carbon materials, metal oxides, metal nitrides, metal carbides, metal sulfides, metal phosphides or metal selenide materials is selected as a positive electrode, the positive electrode and the negative electrode are separated by a diaphragm adsorbed with the benzo [1,2-b:4,5-b' ] dithiophene-4, 8-diketone lithium-oxygen battery electrolyte, and the lithium-oxygen battery is obtained by packaging after assembly.

3. The method of claim 2, wherein the carbon material is one or more of carbon paper, carbon cloth, carbon nanotube, graphene and carbon black, and the metal oxide is MnO₂、Co₃O₄、Fe₂O₃、V₂O₅And NiO, the metal carbide is tungsten carbide or molybdenum carbide, the metal nitride is tungsten nitride or molybdenum nitride, the metal sulfide is molybdenum sulfide or iron sulfide, and the metal phosphide is cobalt phosphide, iron phosphide, selenium phosphide or nickel phosphide.

4. The method of claim 3, wherein the positive electrode is loaded with α -MnO₂The carbon paper electrode is prepared by the following specific steps: 307mg of potassium permanganate is dissolved in 35 ml of deionized water under stirring, then 500 mul of concentrated hydrochloric acid is added and stirred to form a precursor solution, and then the precursor solution is transferred into a polytetrafluoroethylene lining autoclave with a 1 cm piece²Vertically fixing carbon paper in a reaction kettle, sealing, carrying out hydrothermal reaction at 140 ℃ for 8 h, naturally cooling to room temperature, washing with deionized water, and treating at 300 ℃ for 2 h in air to obtain the supported alpha-MnO₂The carbon paper electrode of (1).

5. The method for preparing a lithium-oxygen battery according to claim 2, wherein the supported carbon material positive electrode is prepared by the following steps: and uniformly mixing the carbon nano tube and the polymer binder in N-methyl-2-pyrrolidone, coating the mixture on a conductive substrate, and drying in vacuum to obtain the conductive carbon nano tube.

6. The method of claim 5, wherein the carbon nanotubes comprise 5 ~ 90 wt% of the total weight of the carbon nanotubes and the polyvinylidene fluoride.

7. The method for preparing a lithium-oxygen battery according to claim 2, wherein the separator is a glass fiber porous membrane or a polymer fiber porous membrane.

8. The lithium-oxygen battery obtained by the preparation method of claims 2 to 7.

9. Benzo [1,2-b:4,5-b']Use of dithiophene-4, 8-diones in lithium-oxygen batteries, characterized in that, on discharge, the first electron acceptance from the electrode surface is converted into BDTD^-Then combining with lithium ion to form BDTDLi, BDTDLi reducing oxygen in solution to form BDTDLiO₂Intermediate, BDTDLiO₂Reduced by another molecule of BDTDLi or two molecules of BDTDLiO₂Disproportionation to produce Li₂O₂While regenerating BDTD to continuously obtain oxygen in the electron reduction solution from the surface of the electrode, repeating the steps, wherein benzo [1,2-b:4,5-b']Dithiophene-4, 8-dione is abbreviated as BDTD.

Technical Field

The invention belongs to the technical field of lithium-oxygen batteries, and particularly relates to application of benzo [1,2-b:4,5-b '] dithiophene-4, 8-diketone in a lithium-oxygen battery and a benzo [1,2-b:4,5-b' ] dithiophene-4, 8-diketone lithium-oxygen battery obtained by using the same.

Background

The theoretical energy density of the organic lithium oxygen battery is up to 3500 Wh kg^-1The energy density of the lithium ion battery is higher by one order of magnitude than that of the current commercial lithium ion battery, so that the lithium ion battery has wide application prospect in the fields of electric automobiles, portable power supplies and the like.

In a lithium oxygen cell with an aprotic solvent, the reduction reaction (ORR) of oxygen on discharge is Li-O₂Basic process of battery, which is accompanied by LiO₂And (5) generation of an intermediate. LiO in the state of adsorption on the surface of the positive electrode₂The intermediate not only initiates compact and insulating Li₂O₂Film, but also with electrolyte to form LiOH and Li₂CO₃And the like, resulting in a decrease in the practical capacity of the battery and deterioration in cycle stability.

The introduction of a soluble Redox Mediator (RM) into the electrolyte can partially convert the catalytic oxygen reduction reaction on the surface of the electrode into a liquid-phase catalytic oxygen reduction reaction, and delay the adsorption state LiO₂And generating process, thereby improving the capacity of the battery. Wherein, the quinone molecule (RM) not only acts as a medium for electron transfer in the process of catalyzing the oxygen reduction process, but also generates stable RM-LiO₂Intermediate of (2), reduction of LiO₂Thereby reducing the extent of side reactions. For example 2, 5-di-tert-butyl-1, 4-benzoquinone (DBBQ) (nat. Mater. 2016, 15, 882), coenzyme Q₁₀ (adv. mater. 2018, 30, 1705571) showing their ability to transfer oxygen reduction reaction sites from the electrode surface into the electrolyte and reduce by-products.

It is speculated from the principle of lithium oxygen battery discharge that the catalytic oxygen reduction of these quinone molecules and the catalytic oxygen reduction on the electrode surface are a competitive process. When the oxidation-reduction potential of the quinone molecule is low, the catalytic oxygen reduction capability of the quinone molecule is weak, so that the catalytic oxygen reduction on the surface of the electrode is dominant to generate adsorbed LiO₂The intermediate causes a decrease in battery capacity and decomposition of the electrolyte. On the contrary, when the oxidation-reduction potential of the quinone molecule is high, oxygen is inThe possibility of reduction at the electrode surface is reduced and the production of LiO by catalytic oxygen reduction at the electrode surface₂However, the best performance of the liquid-phase catalytic oxygen reduction reported in the prior art is quinone molecule 2, 5-di-tert-butyl-1, 4-benzoquinone (DBBQ), which has a catalytic oxygen reduction half-wave potential of ~ 2.61.61V vs Li in a stable ether electrolyte⁺/Li, with Li₂O₂/O₂Theoretical reversible potential of (2.96V vs Li)⁺/Li) differs by 0.35V, the increase in the discharge potential of the Li-oxygen battery is not only limited, but also insufficient to inhibit the catalytic oxygen reduction process at the electrode surface. Furthermore, the DBBQ molecule contains two tert-butyl functional groups, which may lead to low diffusion coefficient and electrochemical decomposition. DBBQ can form DBBQ-LiO in the catalytic oxygen reduction process₂Intermediate for reducing LiO₂Oxidation activity towards electrolytes, but the deficiencies of DBBQ described above make it unsuitable for discussing solution catalyzed oxygen reduction process towards Li-O₂The effect of the cycling stability of the cell.

In the present application, benzo [1,2-b:4,5-b 'is used']Dithiophene-4, 8-dione (BDTD) quinone molecule as liquid phase catalyst to study Li-O pair in solution-catalyzed oxygen reduction and electrode surface-catalyzed oxygen reduction processes₂The half-wave potential and the molecular diffusion coefficient of BDTD molecular catalytic oxygen reduction are ~ 2.63.63 vs Li respectively⁺Li and 5.05X 10^-7 cm² s^-1All higher than the corresponding parameters of DBBQ (2.61 vs Li)⁺Li and 2.89X 10^-7 cm² s^-1) Thus ensuring a higher ORR reaction rate. In addition, BDTD has a plane-conjugated symmetrical structure, thereby showing high electrochemical stability, which makes BDTD-LiO₂Composite structure ratio DBBQ-LiO₂Is more stable. Thus, Li-O assembled with BDTD molecules₂The battery exhibits high discharge potential and capacity, and good cycle stability. This application demonstrates for the first time, by using Li-O₂Quinone molecules in the cell modulate the solution-mediated ORR process, substantially inhibiting discharge side reactions.

Disclosure of Invention

The invention aims to provide application of benzo [1,2-b:4,5-b' ] dithiophene-4, 8-diketone molecules in a lithium-oxygen battery and the lithium-oxygen battery obtained by using the same.

Based on the purpose, the invention adopts the following technical scheme:

benzo [1,2-b:4,5-b']The dithienyl-4, 8-diketone lithium-oxygen battery electrolyte is prepared by the following steps: benzo [1,2-b:4,5-b']Dissolving dithiophene-4, 8-diketone and lithium salt in an organic solvent to obtain an electrolyte; benzo [1,2-b:4,5-b']The concentrations of dithiophene-4, 8-diketone and lithium salt in the organic solvent are respectively 0.05 ~ 25 mmol/L and 1 ~ 4 mol/L, wherein the lithium salt is lithium hexafluorophosphate (LiPF)₆) Lithium tetrafluorophosphate (LiPF)₄) Lithium perchlorate (LiClO)₄) Lithium hexafluoroarsenate (V) (LiAsF)₆) Lithium trifluoromethanesulfonate (LiCF)₃SO₃) Lithium bis (trifluoromethylsulfonyl) imide (LiN (CF)₃SO₂)₂) Tris (trifluoromethylsulfonyl) methyllithium (LiC (SO)₂CF₃)₃) Or one or more of lithium bis (oxalato) borate (LiBOB), wherein the organic solvent is one or more of ethylene glycol monomethyl ether, tetraethylene glycol dimethyl ether, N, N-dimethylacetamide, dimethyl sulfoxide, butanone, dioxolane, tetrahydrofuran or dimethyl carbonate. The preferred organic solvent is tetraethylene glycol dimethyl ether.

The method for preparing the benzo [1,2-b:4,5-b ' ] dithiophene-4, 8-diketone lithium-oxygen battery by using the benzo [1,2-b:4,5-b ' ] dithiophene-4, 8-diketone lithium-oxygen battery electrolyte selects lithium as a negative electrode, a conductive substrate loaded with carbon materials, metal oxides, metal nitrides, metal carbides, metal sulfides, metal phosphides or metal selenide materials as a positive electrode, the positive electrode and the negative electrode are separated by a diaphragm adsorbed with the electrolyte, and the benzo [1,2-b:4,5-b ' ] dithiophene-4, 8-diketone lithium-oxygen battery is obtained after the assembly is carried out and the packaging is carried out.

The membrane is a porous membrane, such as glass fiber (1 cm)²) Or dissolving polymer fiber in the above electrolyte to soak the glass fiber, and taking out (adsorbing 50 ~ 100 μ L electrolyte) to obtain the separator with electrolyte.

The substrate can be universal to the battery fieldThe electrode area is the common electrode area, such as 1 cm². The carbon material loaded on the substrate can be a carbon material commonly used in the field of batteries, specifically, carbon nanotubes, ketjen black, graphene, carbon paper, carbon cloth, and taking carbon nanotubes as an example, the preparation process of the carbon nanotube-loaded positive electrode is as follows: mixing carbon nanotube and polyvinylidene fluoride in N-methyl-2-pyrrolidone, coating on stainless steel substrate, and placing electrode at 110 deg.C^oC. Heating for 10 hours under vacuum condition, and obtaining the carbon nano tube and the polyvinylidene fluoride in any proportion, wherein the carbon nano tube accounts for 5 ~ 90 wt% of the total weight of the carbon nano tube and the polyvinylidene fluoride, the load mass of the carbon nano tube can be selected according to batteries of different types, for example, when a 2032 button battery is used, the load capacity of the carbon nano tube is controlled at 0.7 +/-0.2 mg/square centimeter.

The preparation of the metal oxide, metal nitride, metal carbide, metal sulfide, metal phosphide or metal selenide material substrate can adopt a known hydrothermal or electrodeposition method.

Wherein the metal oxide may be MnO₂、Co₃O₄、Fe₂O₃、V₂O₅NiO, and the like, wherein the carbide can be tungsten carbide, molybdenum carbide and other common carbides, the nitride is tungsten nitride, molybdenum nitride and other common nitrides, and the sulfide is molybdenum sulfide, iron sulfide and other common sulfides. The metal phosphide is cobalt phosphide, iron phosphide, selenium phosphide or nickel phosphide. With alpha-MnO₂For example, the preparation process of the positive electrode is as follows: dissolving 307mg potassium permanganate in 35 ml deionized water under stirring, adding 500 μ L commercial concentrated hydrochloric acid, stirring for 2 min to obtain precursor solution, transferring into polytetrafluoroethylene-lined autoclave with 1 cm piece²Vertically fixing the carbon paper in a reaction kettle, sealing, performing hydrothermal reaction at 140 ℃ for 8 hours, and naturally cooling to room temperature to obtain CP-alpha-MnO₂Washing with deionized water for several times, treating at 300 deg.C for 2 hr to obtain carbon paper electrode loaded with manganese dioxide, and calculating the capacity of corresponding cell by geometric areaAmount of the compound (A).

The benzo [1,2-b:4,5-b' ] dithiophene-4, 8-dione lithium-oxygen battery is obtained by the method.

Benzo [1,2-b:4,5-b']Use of dithiophene-4, 8-diones (BDTD) in lithium-oxygen batteries, the BDTD first accepting electrons from the electrode surface on discharge to become BDTD^-Then combining with lithium ion to form BDTDLi, BDTDLi reducing oxygen in solution to form BDTDLiO₂Intermediate, BDTDLiO₂Reduced by another molecule of BDTDLi or two molecules of BDTDLiO₂Disproportionation to produce Li₂O₂And meanwhile, regenerating BDTD to continuously obtain oxygen in the electron reduction solution from the surface of the electrode, and repeating the steps.

The invention adopts BDTD molecules as liquid phase catalysts to research the oxygen reduction reaction catalyzed by a solution phase and the oxygen reduction reaction process catalyzed by the surface of an electrode to Li-O₂The BDTD has higher oxidation-reduction potential and diffusion coefficient, and the inhibition degree of the catalytic reduction process of oxygen on the surface of the electrode is far higher than that of a DBBQ system under certain current density, so that LiO is generated by the reduction of oxygen on the surface of the electrode₂The side reactions initiated are also correspondingly suppressed. In lithium oxygen batteries assembled using different carbons and metal oxides as the positive electrode, the presence of BDTD increases the battery capacity by several times or more, being the most advanced soluble redox mediator to date.

Drawings

FIG. 1: molecular structures of BDTD and DBBQ.

FIG. 2: (a, b) cyclic voltammetry curves of 20 mmol/L BDTD, DBBQ/TEGDME electrolyte respectively; wherein, black represents the presence or absence of BDTD or DBBQ in the presence of oxygen, red represents the presence or absence of BDTD or DBBQ in the presence of oxygen, and blue represents the presence or absence of BDTD or DBBQ in the presence of oxygen; and (c and d) are respectively 20 mmol/L BDTD, the CV curve of DBBQ/TEGDME electrolyte is shown in the drawing in a local magnification mode under the condition of argon/oxygen, and the electrolyte is tetraethylene glycol dimethyl ether dissolved with 1M LiTFSI.

FIG. 3: (a, b) are respectively 20 mmol/L BDTD, DBBQ/TEGDME electrolyte cyclic voltammograms at different scanning rates; and (c, d) calculating the diffusion coefficients of BDTD and DBBQ, wherein the electrolyte is the tetraglyme dissolved with 1M LiTFSI.

FIG. 4: (a, b) are respectively 20 mmol/L BDTD, and CV curves of DBBQ/TEGDME electrolyte after 200 cycles, wherein the electrolyte is tetraglyme dissolved with 1M LiTFSI.

Fig. 5 is the effect of BDTD, DBBQ on the capacity and stability of the cell on the carbon paper electrode; (a) discharge curves of li-oxygen cells at different current densities with BDTD (solid line), DBBQ (dashed line) and no liquid phase catalyst (dotted line) added in 1.0M lithium bis (trifluoromethylsulfonyl) imide (LiTFSI)/Tetraglyme (TEGDME) electrolyte; (b) difference of discharge potential under addition of BDTD (red), DBBQ (blue) and liquid-phase-free catalyst (black); (c) BDTD, DBBQ and different discharge capacities (0.5,1.0, 1.5 mAh cm) without liquid phase catalyst^-2) Raman wave propagation; (d) BDTD, DBBQ and the circulation stability without liquid phase catalyst; the electrolyte was 1M LiTFSI/TEGDME, with BDTD, DBBQ, at a concentration of 20 mmole/liter (units) in the electrolyte.

FIG. 6 is a graph of simulations (a) DBBQ and (b) BDTD vs LiO₂Adsorption case of (c) BDTD-LiO₂Charge distribution in the complex (red spheres for "O", green for "Li", pink for "H", brown for "C").

FIG. 7 is a graph of the effect of BDTD, DBBQ on the capacity and stability of a cell on a carbon nanotube electrode; (a) the lithium-oxygen cell in 1.0M LiTFSI/TEGDME electrolyte was charged with the discharge curves at different current densities at BDTD (red), DBBQ (blue) and no liquid phase catalyst (black); (b) BDTD (red), DBBQ (blue) and liquid-phase-free catalyst (black) are added to lower the discharging potential difference; (c) BDTD, DBBQ and different discharge capacities (0.5,1.0, 1.5 mAh cm) without liquid phase catalyst^-2) Raman wave propagation; (d) BDTD, DBBQ and circulation stability without liquid phase catalyst. The electrolyte is tetraethylene glycol dimethyl ether dissolved with 1M LiTFSI, and when BDTD and DBBQ exist, the concentration of the electrolyte is 20 millimole/liter (unit), and the current density is 200 milliampere/gram.

Fig. 8 shows DEMS results of BDTD, DBBQ during battery charging and discharging. In the mixed gas O₂(a) liquid-phase-free catalysis under the conditions of/Ar (4/1, v/v) and current 1500 muAOxidant, (b) BDTD, (c) DBBQ catalyzed lithium-oxygen cell discharge process. Under Ar conditions and current of 500 muA, (d) no liquid phase catalyst, (e) BDTD, (f) DBBQ catalyzed lithium-oxygen battery charging process.

FIG. 9 is BDTD with DBBQ at alpha-MnO₂The effect on the electrode on the capacity and stability of the battery. (a) Lithium oxygen cells add discharge curves at different current densities at BDTD (solid line), DBBQ (dashed line) and no liquid phase catalyst (dotted line); (b) difference of discharge potential under addition of BDTD (red), DBBQ (blue) and liquid-phase-free catalyst (black); (c) BDTD, DBBQ and different discharge capacities (0.5,1.0, 1.5 mAh cm) without liquid phase catalyst^-2) An XRD pattern; (d) BDTD, DBBQ and cycle stability without liquid phase catalyst; the electrolyte was 1M LiTFSI-dissolved tetraethylene glycol dimethyl ether, and when BDTD and DBBQ were present, the concentration thereof in the electrolyte was 20 mmol/L (unit).

FIG. 10 shows competition between quinone catalyzed solution phase oxygen reduction (left) and solid electrode catalyzed surface oxygen reduction (right) reactions. Due to the higher oxidation-reduction potential of quinone molecules and the formation of stable RM-LiO₂ Composite structure, adsorbed LiO₂The induced side reaction is inhibited, and the cycling stability of the battery is improved. In contrast, the oxygen reduction process catalyzed by the electrode surface is due to the formation of highly active LiO₂Resulting in electrode corrosion and electrolyte decomposition.

Fig. 11 is a schematic diagram of a lithium-oxygen battery catalyzed oxygen-reduction reaction.

Detailed Description

In order to make the technical purpose, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention are further described below with reference to the accompanying drawings and specific embodiments.

Material sources are as follows: anhydrous tetraethylene glycol dimethyl ether (TEGDME), lithium bis (trifluoromethane) sulfonimide (LiTFSI) was purchased directly from duo chemicals ltd, suzhou, china. The water content of the solvent is less than 20 ppm, and the water content of the lithium salt is less than 40 ppm. Benzo [1,2-b:4,5-b']Dithiophene-4, 8-dione was purchased from Michelin and 2, 5-di-tert-butyl-1, 4-benzoquinone was purchased from Alantin. Potassium permanganate and concentrated hydrochloric acid were purchased from LuoyangAnd (4) taking the Chinese patent medicine as a Hao Hua. The glass fiber is Whatman glass fiber, type: 1822-047. Carbon paper (Toray, TDP-H060) was purchased from Shanghai and Senen electric Co., Ltd, China. Carbon nanotubes purchased from Tianjin Iversson chemical technology, Inc., alpha-MnO₂The electrode is prepared by hydrothermal method, and can be referred to specifically

Zhang, P.; Zhang, S.; He, M.; Lang, J.; Ren, A.; Xu, S.; Yan, X., Realizing the Embedded Growth of Large Li2O2 Aggregations by MatchingDifferent Metal Oxides for High-Capacity and High-Rate Lithium OxygenBatteries. Adv. Sci. 2017, 4 (11), 1700172.

High purity O was used in all measurements₂ (99.999%). All materials used for cell assembly were stored in an argon-filled glove box.