阅读说明：本技术 一种同时兼具氧化还原介质和锂金属保护剂功效的锂空气电池用二茂钌添加剂 (Bis-ruthenium additive for lithium air battery with effects of redox medium and lithium metal protective agent ) 是由 和庆钢 唐艺钊 谢健 于 2021-06-23 设计创作，主要内容包括：本发明公开了一种同时兼具氧化还原介质和锂金属保护剂功效锂空气电池用二茂钌(Ruthenocene,Ruc)添加剂,将其应用于以碳棒修饰RuO-(2)/MnO-(2)分级结构正极材料(RuO-(2)/MnO-(2)@NC)为正极的锂空气电池,同时具有氧化还原介质及锂保护双效功能。本发明以在碳纸表面经电聚合生长并煅烧所形成的碳阵列,随后在表面逐步沉积MnO-(2)、RuO-(2)催化剂制备复合材料RuO-(2)/MnO-(2)@NC为正极材料,将Ruc溶解于电解液中作为添加剂以应用于该电池体系。所添加的二茂钌在锂空气电池电化学反应中充当氧化还原介质,同时克服了常见氧化还原介质的缺陷,对负极金属锂的稳定性有积极作用。Ruc应用于锂空气电池中,在400mA·g～(-1)的电流密度下,限定容量为500mAh·g～(-1)时,电池循环寿命达到260圈以上。(The invention discloses a Ruthenocene (Ruc) additive for a lithium-air battery with functions of a redox medium and a lithium metal protective agent simultaneously, which is applied to a carbon rod modified RuO 2 /MnO 2 Positive electrode material of hierarchical structure (RuO) 2 /MnO 2 @ NC) as the positive electrode, and has the double-effect functions of oxidation-reduction medium and lithium protection. The invention grows and calcines the carbon array on the surface of the carbon paper by electropolymerization, then gradually deposits MnO on the surface 2 、RuO 2 Preparation of composite RuO by catalyst 2 /MnO 2 @ NC is a positive electrode material, and Ruc is dissolved in an electrolyte as an additive to be applied to the battery system. The added ruthenocene serves as a redox medium in the electrochemical reaction of the lithium-air battery, overcomes the defects of the common redox medium, and has positive effect on the stability of the metal lithium of the cathodeThe application is as follows. Ruc applied to lithium air battery, at 400mA g ‑1 Has a limited capacity of 500mAh g at a current density of (1) ‑1 Meanwhile, the cycle life of the battery reaches more than 260 circles.)

1. A ruthenocene additive for lithium-air battery with redox medium and lithium metal protectant functions simultaneously is characterized in that the ruthenocene additive can be applied to a carbon rod to modify RuO₂/MnO₂Hierarchical RuO₂/MnO₂A lithium-air battery having @ NC as a positive electrode material.

2. The ruthenocene additive for lithium air batteries having both redox mediator and lithium metal protectant efficacy according to claim 1, wherein the ruthenocene additive is dissolved in a conventional electrolyte for lithium air batteries; the electrolyte for the conventional lithium air battery is obtained by dissolving 1M lithium bis (trifluoromethanesulfonyl) imide in tetraethylene glycol dimethyl ether.

3. The ruthenocene additive for a lithium-air battery, which has both redox mediator and lithium metal protectant functions as claimed in claim 2, wherein the concentration of the additive in the electrolyte is 0.01-0.5M.

4. The ruthenocene additive for lithium-air batteries having both redox mediator and lithium metal protectant efficacy according to claim 1, wherein said RuO₂/MnO₂The @ NC has a three-dimensional hierarchical structure, and takes a nitrogen-doped three-dimensional carbon array as a substrate, and MnO is gradually deposited on the surface of the carbon array₂And adsorption of RuO₂And (4) preparing.

5. The ruthenocene additive for lithium-air batteries having both redox mediator and lithium metal protectant efficacy according to claim 4, wherein said RuO₂/MnO₂The preparation of @ NC comprises the following steps:

1) taking mixed solution of pyrrole, sodium dihydrogen phosphate dihydrate, disodium hydrogen phosphate dodecahydrate and 4-sodium toluenesulfonate as electrolyte, preparing a three-dimensional polypyrrole array on the surface of carbon paper which is subjected to cleaning treatment and is provided with tabs through electropolymerization by a timing voltage method, wherein the electropolymerization applied voltage is 0.65-0.75V (vs SCE);

2) taking a three-dimensional polypyrrole array as a precursor, and adding N₂Calcining for 1-6 hours at the high temperature of 400-900 ℃ in a protective atmosphere to obtain a nitrogen-doped three-dimensional carbon array;

3) immersing the product obtained in the step 2) in a potassium permanganate solution of 0.01-0.5M, heating and stirring for 1.5-9 h to deposit MnO₂(ii) a 4) Immersing the product obtained in the step 3) in 0.1-0.5 mg/mL RuCl₃Slowly stirring the aqueous solution for 1-6 h to deposit RuO₂Granules are thereby producedPreparation of RuO₂/MnO₂@NC。

6. The ruthenocene additive for lithium-air batteries having both redox mediator and lithium metal protectant functions according to claim 1, wherein the decomposition path of the discharge product of the lithium-air battery in the charging reaction is: the ruthenocene is firstly converted into an oxidation state through an electrochemical reaction, and then a discharge product is oxidized, and the ruthenocene serves as an intermediate medium.

7. The ruthenocene additive for a lithium-air battery having both redox mediator and lithium metal protectant effects according to claim 1, wherein a stable LiF layer is formed on the surface of the negative electrode of the lithium-air battery.

Technical Field

The invention relates to an additive bis (cyclopentadienyl) ruthenium with redox intermediate medium function and lithium protection function, which can be added into lithium-air battery electrolyte and applied to modification of RuO by using a carbon rod₂/MnO₂Hierarchical structure (RuO)₂/MnO₂@ NC) as a positive electrode material.

Background

Fossil fuel resources are decreasing day by day, and the development and utilization of new clean energy are imminent. The lithium air battery has higher theoretical specific capacity and specific energy, the theoretical energy density of the lithium air battery is as high as 5210 W.h/kg, and the lithium air battery is close to gasoline, and is an ideal fossil fuel substitute, so the lithium air battery is gradually focused on people. The oxygen consumed by the anode of the lithium-air battery is taken from air and stored outside the battery, and the lithium-air battery is an open system, so that the theoretical capacity of the lithium-air battery is larger than that of a closed battery, and the lithium-air battery has the advantages of light weight, small volume and the like, so that the lithium-air battery is the most potential energy carrier in the future.

At present, the electrode reaction mechanism of the lithium-air battery is complex, and the commonly-thought main discharge product Li of the organic system lithium-air battery₂O₂Insoluble in organic electrolyte and non-conductive, precipitate at cathode and prevent O₂Diffusion and prevention of charge conduction, which in turn leads to discharge termination, so improvement of the air electrode is key to improving the performance of the lithium-air battery. While a significant problem in charging batteries is the discharge product Li₂O₂The decomposition process easily causes polarization, large overpotential and causes the reduction of the energy efficiency and the cycle performance of the lithium air battery. And the oxygen precipitation process needs higher potential, which easily causes the decomposition of organic electrolyte to form insoluble lithium carbonate, so that the performance of the lithium air battery is reduced. Therefore, Li can be improved by designing a positive electrode material with both space structure and catalytic activity₂O₂The problem caused by the accumulation.

The use of the cathode material with excellent space structure and high-efficiency catalytic activity can effectively relieve Li₂O₂The problem is still apparent when the catalytic sites on the surface of the positive electrode are coated with Li₂O₂After coveringThe electrochemical reaction efficiency of the lithium-air battery is reduced, and the electrode surface catalyst is the same as Li₂O₂In a solid-solid contact manner, and therefore, Li which is far from the catalytic site during charge decomposition is insufficient in contact tightness₂O₂The decomposition efficiency is limited. Redox Mediators (RMs) dissolved in the electrolyte solution improve this problem. Application of RM to changeable Li of lithium-air battery₂O₂Is first oxidized to the oxidation state RM on discharge⁺Subsequently RM⁺Reoxidation decomposition of Li₂O₂In the process, RM serves as an intermediate medium and can achieve high-efficiency Li decomposition₂O₂The effect of reducing the charging voltage. Since RM dissolves in the electrolyte, it can react with Li in the solid phase₂O₂Close contact, solve the defects of solid-phase anode materials.

However, RM has certain defects, the common RM has a shuttle effect, and the RM is oxidized into RM at a positive electrode during charging⁺And then, the lithium ions are easy to shuttle to the surface of the negative electrode, and the lithium metal of the negative electrode is easy to corrode due to the strong oxidizing property of the lithium metal, and the lithium metal is continuously consumed. Therefore, the lithium air battery using the cathode material having a steric structure and catalytic activity still has a problem of corrosion of lithium metal after RM is used as an additive, and the life of the battery cannot be further improved.

Disclosure of Invention

The invention uses carbon rod to modify RuO₂/MnO₂Hierarchical structure material (RuO)₂/MnO₂@ NC) is the anode of the lithium-air battery, and aiming at the performance and defects of the anode material in the lithium-air battery, the ruthenium dicyclopentadienyl which has the functions of oxidation-reduction media and lithium protection is added into the electrolyte to be used as an additive so as to make up the defects of the anode material.

The invention discloses a lithium air battery additive bis ruthenium with redox medium function, which can effectively reduce the charging voltage of a lithium air battery and improve Li₂O₂The decomposition efficiency of (a). Meanwhile, as an additive, the lithium ion battery has a good lithium protection function and can avoid the shuttle flying effect on lithium goldCorrosion of the genus. The quinary ring structure in the ruthenocene structure can promote the formation of a stable LiF layer on the surface of the lithium cathode during the electrochemical reaction, so that the uniform stripping and deposition of lithium are promoted, the lithium is prevented from being attacked by active molecules in long-term circulation, and the cycle life of the battery is obviously prolonged.

The technical scheme adopted by the invention is as follows:

taking 0.1-0.5M pyrrole, 0.1-0.5M sodium dihydrogen phosphate, 0.1-0.5M disodium hydrogen phosphate and 0.1-0.5M sodium 4-toluenesulfonate solution dissolved in the solution as electrolyte, adopting a timing voltage method, and carrying out single-side electropolymerization on the surface of clean carbon paper with a lug by using a current of 0.8-3 mA, wherein the polymerization electric quantity is 2-5C, so as to obtain the three-dimensional ppy array. Place the ppy array in a tube furnace, hold N₂And calcining the mixture for 1 to 6 hours at the high temperature of 400 to 900 ℃ in the atmosphere to obtain the nitrogen-doped carbon array. Immersing the carbon array in 0.001-0.05M KMnO₄In the solution, slowly stirring is maintained at 30-80 ℃, and the solution is kept for 1.5-9 hours to obtain deposited MnO₂Has a hierarchical structure. Will deposit MnO₂The three-dimensional carbon array is immersed in RuCl of 0.1-0.6 mg/mL₃·xH₂In the solution of O, NaOH solution is used for adjusting the pH value to be 3.5-6.5, the solution is slowly stirred for 1-6 h at the temperature of 20-60 ℃, and then the product is taken out and is placed in N₂Calcining for 2-6 hours at the temperature of 100-400 ℃ in the atmosphere to obtain the carbon rod modified RuO₂/MnO₂Graded three-dimensional positive electrode material (RuO)₂/MnO₂@ NC). Mixing RuO₂/MnO₂The @ NC is used as a positive electrode material to assemble the battery, meanwhile, the cyclopentadienyl ruthenium is added into the electrolyte to serve as an additive to serve as a redox medium and a protective agent, and the stability of the lithium air battery is improved together with the synergistic effect of the positive electrode material.

The ruthenocene can be used as a redox medium in the invention, and Li can be improved through the change of the valence state of the ruthenium atom at the center of the ruthenocene in the charging process₂O₂The voltage during battery charging is shown as the potential during the oxidation reaction of ruthenocene, which is lower than the charging voltage of the conventional lithium air battery, thereby achieving the purpose of reducing the charging overpotential。

Compared with the conventional redox medium, the ruthenium cyclopentadienyl in the invention has unobvious corrosion effect on the lithium cathode due to the shuttle effect, and has promotion effect on the stability of the lithium metal of the cathode due to the special structure of the five-membered ring in the structure.

The protection of the ruthenocene on the negative lithium metal can promote the uniform stripping and deposition of lithium on the surface of the negative electrode during the charging and discharging of the battery, and a stable LiF layer is formed on the surface of the lithium negative electrode through electrochemical reaction, so that the lithium is prevented from being attacked by active molecules in long-term circulation, the formation of LiOH on the surface of the negative electrode lithium is reduced, and the protection has good promotion effect on the overall stability of the lithium metal and the battery.

The ruthenocene has two functions and is used as an oxidation-reduction medium and a protective agent as well as a positive electrode material RuO₂/MnO₂The action of @ NC forms complementation, and the cycle life of the lithium-air battery is prolonged in cooperation.

Drawings

FIG. 1 RuO obtained by stepwise preparation₂/MnO₂SEM picture of @ NC.

FIG. 2 shows the use of RuO₂/MnO₂And @ NC is a positive electrode, the cyclopentadienyl ruthenium and the lithium-air battery without the additive are added into the electrolyte, and the cyclic voltammetry curve is obtained at the scanning rate of 0.1mV and under the voltage window of 2.0-4.5V.

FIG. 3 shows the use of RuO₂/MnO₂Lithium air battery with @ NC as positive electrode and cyclopentadienyl ruthenium added into electrolyte at 400 mA.g^-1Current density of 500mAh · g^-1A cycle life map at a defined capacity.

FIG. 4 shows the use of RuO₂/MnO₂Lithium air battery with @ NC as positive electrode and cyclopentadienyl ruthenium added into electrolyte at 800 mA.g^-1Current density of 1000mAh g^-1SEM topography of negative electrode lithium after 10 cycles at defined capacity.

FIG. 5 shows the use of RuO₂/MnO₂Lithium air battery with @ NC as positive electrode and cyclopentadienyl ruthenium added into electrolyte at 800 mA.g^-1Current density of 1000mAh g^-1After ten cycles of the negative electrode lithium under the limited capacity of (2)Li1s, F1 s XPS test results.

FIG. 6 shows the use of RuO₂/MnO₂A lithium air battery with @ NC as the positive electrode and no additive in the electrolyte at 400mA · g^-1Current density of 500mAh · g^-1A cycle life map during cycling at the defined capacity of (2).

FIG. 7 shows the use of RuO₂/MnO₂A lithium air battery with @ NC as the positive electrode and no additive in the electrolyte at 800mA · g^-1Current density of 1000mAh g^-1SEM topography of the negative electrode lithium after ten cycles at the defined capacity of (a).

FIG. 8 shows the use of RuO₂/MnO₂A lithium air battery with @ NC as the positive electrode and no additive in the electrolyte at 800mA · g^-1Current density of 1000mAh g^-1The negative electrode lithium after ten cycles at the limited capacity of (2) and the results of XPS test on Li1s and F1 s.

FIG. 9 shows the use of RuO₂/MnO₂A lithium air battery having a positive electrode of @ NC and a lithium iodide added to the electrolyte at a current of 400mA g^-1Current density of 500mAh · g^-1A cycle life map at a defined capacity.

FIG. 10 shows the use of RuO₂/MnO₂A lithium air battery with @ NC as the positive electrode and lithium iodide added to the electrolyte at 800mA · g^-1Current density of 1000mAh g^-1SEM topography of the negative electrode lithium after ten cycles at the defined capacity of (a).

FIG. 11 shows the use of RuO₂/MnO₂A lithium air battery with @ NC as the positive electrode and lithium iodide added to the electrolyte at 800mA · g^-1Current density of 1000mAh g^-1Li1s of the negative electrode lithium after ten cycles at the defined capacity, F1 s XPS test result.

FIG. 12 shows the use of RuO₂/MnO₂A lithium air battery with @ NC as positive electrode and indium iodide added into electrolyte at 400 mA.g^-1Current density of 500mAh · g^-1A cycle life map at a defined capacity.

Detailed Description

Example 1

Preparation of RuO₂/MnO₂@NC：

Taking stoichiometric pyrrole, sodium dihydrogen phosphate dihydrate, disodium hydrogen phosphate dodecahydrate and 4-sodium toluenesulfonate, preparing a mixed solution containing 0.1M pyrrole monomer, 0.2M sodium dihydrogen phosphate, 0.2M disodium hydrogen phosphate and 0.2M 4-sodium toluenesulfonate, and placing the mixed solution in ultrasound for dispersing for 60 min. Cutting carbon paper with main body of 16 × 16mm²And leaving the tab, ultrasonically cleaning the tab by isopropanol to remove oil stains on the surface, ultrasonically cleaning the tab by deionized water, and drying the tab for use. The counter electrode is a platinum mesh, the reference electrode is a saturated calomel electrode, and the carbon paper is a working electrode. Utilizing an autolab204N electrochemical workstation, limiting the polymerization electric quantity to 3-4C by adopting a timing voltage method and a current of 1.5mA to obtain a polypyrrole array, and then placing the polypyrrole array in N₂Calcining the mixture for 1 to 4 hours at the temperature of 700 ℃ in the atmosphere to obtain the N-doped carbon array. The carbon array was exposed to 0.01M KMnO₄In the solution, reacting for 3h at 40-60 ℃ to obtain deposited MnO₂The three-dimensional carbon array of (1). Then MnO will be deposited₂The carbon array of (2) was immersed in 0.2mg/mL RuCl₃·xH₂Adjusting the pH value of the solution of O to about 3.5-6.5 by using NaOH solution, slowly stirring the solution for 1-6 h at the temperature of 30 ℃, taking out a product, and placing the product in N₂Calcining at 200 ℃ for 2h in atmosphere to obtain RuO₂/MnO₂The appearance of the three-dimensional cathode material of @ NC is shown in the attached figure 1 of the specification.

Assembling and testing the battery:

1) mixing RuO₂/MnO₂@ NC cut into 12mm diameter discs.

2) The electrode plates, the 2032 type lithium-air battery button battery case, the spring plates and the gaskets are assembled into the button battery in a glove box according to a certain sequence by taking 1M of lithium bis (trifluoromethane) sulfonimide tetraethylene glycol dimethyl ether solution as electrolyte and dissolving 0.01M of cyclopentadienyl ruthenium additive in the electrolyte.

3) The button cell is placed in a test tank filled with oxygen, the test tank is placed for 24 hours, an autolab204N electrochemical workstation is utilized, a cyclic voltammetry curve under the scanning rate of 0.1mV and the voltage window of 2.0-4.5V is adopted, an obvious oxidation peak appears near 3.85V in the cyclic voltammetry curve, and the conversion of a redox medium to an oxidation state corresponds to the conversion of the redox medium, which shows that the button cell can be used as the redox medium for the lithium air cell, and the instruction is shown in the attached figure 2.

4) Placing the button cell in a test tank filled with oxygen, standing for 2h, and testing with 400 mA.g in a Xinwei test system^-1Current density of 500mAh g^-1The battery cycle life can be tested by limiting the capacity, 268 times of training can be maintained, the charging voltage is below 3.8V in the early stage of the cycle, and the battery overpotential is obviously reduced, see the attached figure 3 in the specification.

Characterization of the shape and components of the lithium metal of the negative electrode:

1) with RuO₂/MnO₂@ NC for positive electrode material, lithium air battery with cyclopentadienyl ruthenium added into electrolyte, and electrolyte concentration of 800 mA.g^-1Current density of 1000mAh g^-1After the limited capacity is circulated for 10 times, the battery is transferred to a glove box and then disassembled, the lithium metal of the negative electrode is taken out, the appearance characterization of SEM is carried out, the surface of the lithium negative electrode can still keep a relatively flat state after being trained, the whole is relatively smooth, and the result is shown in the attached figure 4 of the specification.

2) With RuO₂/MnO₂@ NC for positive electrode material, lithium air battery with cyclopentadienyl ruthenium added into electrolyte, and electrolyte concentration of 800 mA.g^-1Current density of 1000mAh g^-1After the limited capacity is cycled for 10 times, the battery is transferred to a glove box and then disassembled, negative lithium metal is taken out, XPS fine spectrum test of Li1s and F1 s is carried out, Li1s results show that the surface of the lithium negative electrode contains lower LiOH, F1 s results show that the surface of the lithium contains a certain amount of LiF, the lithium negative electrode is stable in the battery, and has a certain inhibiting effect on corrosion of the lithium metal, and the results are shown in the attached figure 5 of the specification.

Comparative example 1

RuO₂/MnO₂The preparation and battery assembly of @ NC was the same as example 1 except that no additive was used in the electrolyte.

The cyclic voltammetry scanning is carried out under the same condition, a conventional oxygen precipitation peak appears at about 4.2V, and an oxidation peak appears when no redox medium exists, and the result is shown in the attached figure 2 of the specification.

The cycle life test is carried out under the same condition, 183 cycles can be maintained, and the result is shown in the attached figure 6 of the specification.

Negative lithium characterization tests were performed under the same conditions and the morphology showed a large number of fractured, large-sized particles on the surface, as shown in fig. 7 of the specification. The Li1s result shows that the surface of the lithium cathode contains higher LiOH, the F1 s result shows that the LiF content of the lithium surface is reduced, and the lithium metal surface is obviously corroded, and the result is shown in the attached figure 8 of the specification.

Comparative example 2

RuO₂/MnO₂The preparation and battery assembly of @ NC were the same as in example 1, except that 0.01M lithium iodide was dissolved in the electrolyte as an additive.

The cycle life test is carried out under the same condition, and the cycle life test can be maintained for 150 times, and the result is shown in the attached figure 9 of the specification.

The negative lithium characterization test is carried out under the same condition, and the appearance shows that a large amount of diaphragm residues appear on the surface, the corrosion of lithium metal is more serious, and the surface has almost no flat parts, as shown in the attached figure 10 of the specification. The Li1s result shows that the LiOH content of the surface of the lithium cathode is high, the F1 s result shows that the LiF content of the surface of the lithium cathode is low, the corrosion effect of the lithium cathode is obviously intensified, and the result is shown in the attached figure 11 of the specification.

Comparative example 3

RuO₂/MnO₂The preparation and battery assembly of @ NC were the same as in example 1, except that 0.0033M of indium iodide was dissolved in the electrolyte as an additive.

The cycle life test was carried out under the same conditions for only 110 cycles, and the results are shown in the attached FIG. 12 of the specification.