CN100427527C - Application of organosulfur polymers in cathode materials for secondary magnesium batteries - Google Patents

Abstract

The invention discloses an application of an organic sulfur polymer in the positive electrode material of a secondary magnesium battery. The organic sulfur polymer is used as the positive electrode, metal magnesium is used as the negative electrode, and Mg[AlCl ₂ (C ₄ H ₉ )(C ₂ H ₅ )] ₂ /tetrahydrofuran as the electrolyte to form a secondary magnesium battery. As the positive electrode material of secondary magnesium battery, organic sulfur polymer has the characteristics of large capacity and high voltage platform. The initial discharge capacity can reach more than 110mAh/g, and the stable discharge voltage platform can reach about 1.6V; compared with the current secondary magnesium battery Compared with the ideal material Mo ₃ S ₄ , organosulfur polymers have the advantages of simple preparation, low cost, and designable structure.

Description

Application of organosulfur polymers in cathode materials for secondary magnesium batteries

technical field

The invention relates to the application of a polymer in battery cathode materials, in particular to the application of an organic sulfur polymer in secondary magnesium battery cathode materials.

Background technique

With the decreasing reserves of fossil fuels represented by the three main energy sources of coal, oil and natural gas, chemical power sources have received great attention in the development and utilization of high-tech devices, green and low-energy transportation, and renewable energy. Among the existing primary and secondary batteries, lithium batteries have the highest energy density, so they are widely researched and applied. However, due to the high activity of metal lithium, its reliability and safety are difficult to be guaranteed, especially in large-scale power lithium secondary batteries, there are still many safety hazards. Therefore, traditional toxic and low-capacity lead-acid or nickel-cadmium batteries are still used in actual power sources. With the continuous emphasis on the environment and resources and the desire for electric vehicles, people have begun to develop some new, high-performance, low-cost green chemical power sources while improving the existing problems of batteries.

In view of the great success of lithium batteries, magnesium, which is on the diagonal line with lithium in the periodic table of elements, is considered to be the It is a negative electrode material for high energy density batteries with great development prospects; especially, magnesium has the advantages of low price, high safety and environmental friendliness, which makes magnesium batteries expected to make breakthroughs in terms of safety and price. It can be seen that the development of practical rechargeable magnesium batteries is of great significance. Although it cannot compete with lithium batteries used in small scales (such as portable electronic instruments), it has potential advantages in large-load applications and is considered to be very promising for electric vehicles. A green storage battery. my country's magnesium resources are very rich, the reserves rank first in the world, and the development of magnesium batteries has unique advantages. Rechargeable magnesium batteries are in the preliminary research stage, and there are many unresolved problems, which make the batteries far from being practical. However, the research on rechargeable magnesium batteries is expected to develop high-performance, low-cost, safe and environmentally friendly large-scale electric energy storage equipment.

At present, there are few researches on magnesium secondary batteries in the world. So far, only the rechargeable magnesium battery system of Israeli scientist D.Aurbach et al. is the relatively perfect system reported (D.Aurbach, Z.Lu, A Schechter, Y. Gofer, H. Gizbar, R. Turgeman, Y. Cohen, M. Moshkovich, E. Levi, Nature, 2000, 407:724). So far, there are only two cases of complete assembly and testing of magnesium secondary batteries in foreign countries, and corresponding patents have been applied for. At present, my country's work on magnesium batteries is still in its infancy, and has gradually begun to pay attention to research in this area in recent years (Yuan Huatang, Jiao Lifang, Cao Jiansheng, Liu Xiusheng, Zhao Ming, Wang Yongmei, Electrochemistry, 2004, 10: 460; Yuan Wangzhi, Lao Linger, Huang Yingcai, Journal of Guizhou Institute of Technology, 1996, 25:86; Yu Long, master's degree thesis of Xinjiang University, 2004).

In the research on intercalation/deintercalation materials for many secondary batteries, it is found that there are few positive electrode materials that can be used as magnesium batteries, mainly (P.Novák, R.Imhof, O.Haas, Electrochimica Acta, 1999, 45 : 351): MoO ₃ , Co ₃ O ₄ , V ₂ O ₅ and MV ₃ O ₈ (H ₂ O) _y (M=Li, Na, K, Ca _0.5 or Mg _0.5 ) vanadate, spinel type oxide, Todorokite type Mg _x MnO ₂ ·yH ₂ O, Nasicon structure Mg _0.5 Ti ₂ (PO ₄ ) ₃ and Mg _0.5+y (Fe _y Ti _1-y ) ₂ (PO ₄ ) ₃ , Cheverel phase Mo ₃ S ₄ . Among them, Mo ₃ S ₄ is a relatively ideal material at present, but it is difficult to prepare, and it needs to be synthesized at high temperature under vacuum or hydrogen atmosphere (D.Aurbach, Z.Lu, A.Schechter, Y.Gofer, H.Gizbar, R. Turgeman, Y. Cohen, M. Moshkovich, E. Levi, Nature, 2000, 407:724).

As a positive electrode material for lithium-ion batteries, organosulfur polymers are characterized by the combination of conductive polymers and organosulfides, which have both the electronic conductivity of the former and the high energy density of the latter (Yang Yusheng, Wang Weikun, Yuan Ke Guo, Cao Gaoping, Wang Anbang, Battery, 2002, 32:1). There are S-S functional groups in the molecular structure, which can undergo electrolytic polymerization-electropolymerization reaction and have electrochemical activity. Compared with inorganic transition metal compounds and conductive polymer cathode materials, organosulfur polymer cathode materials have the advantages of high specific capacity, low price, and low toxicity, and have become the most promising lithium ion cathode materials. The development of high specific capacity and long cycle life organosulfur polymer cathode materials will greatly promote the application of EV and HEV electric vehicles.

Contents of the invention

The purpose of the invention is to use the organic sulfur polymer as the positive electrode material of the secondary magnesium battery, to broaden the application of the organic sulfur polymer in the battery and improve the performance of the secondary magnesium battery.

The present invention uses the organic sulfur polymer as the positive electrode material of the secondary magnesium battery, wherein the organic sulfur polymer is polythiopolyaniline, polythiopolypyrrole, polythiophene or polyphenylene polythio. Specifically, dithiodiphenylamine, part of dithiopolyaniline, tetrathiodiphenylamine, poly 2'2-bisaminophenoxy disulfide, polybisaniline disulfide, polythiopoly(4- ethynylpyridine), polythiobenzene, polythiopolystyrene, polythiocyclopentadiene, polythiocarbyne, polythiopolyphenylene or polythiopolyethynylcyclopentadiene, etc.

The application method of organosulfur polymer of the present invention as secondary magnesium battery positive electrode material is as follows:

Grinding the organic sulfur polymer, adding 5-8 wt% acetylene black based on the organic sulfur polymer as a conductive agent, 5-10 wt% polytetrafluoroethylene emulsion based on the organic sulfur polymer (concentration is 50 ~60wt%) or polyvinylidene fluoride solution (with N-methylpyrrolidone as the solvent, the concentration is 0.02~0.04g/mL) as a binder, mixed into a paste, and pressed on the current collector under a pressure of 3~5MPa , put it in an oven with a temperature of 60-80°C and dry it, punch it into a pole piece with a punch of Φ12-16mm, press it under a pressure of 1-2MPa, and dry it in a vacuum oven at 100-120°C After 3 to 5 hours, the positive electrode was obtained; then transferred to an argon glove box, with metal magnesium as the negative electrode, 0.25mol·L ^-1 of Mg[AlCl ₂ (C ₄ H ₉ )(C ₂ H ₅ )] ₂ /tetrahydrofuran It is used as an electrolyte to make a secondary magnesium battery.

The current collector used in the present invention is copper foil, aluminum foil or nickel foam.

The polytetrafluoroethylene used in the present invention is the polytetrafluoroethylene used for the battery binder.

The polyvinylidene fluoride used in the present invention is polyvinylidene fluoride for battery binder.

The present invention uses organosulfur polymer as the positive electrode material of the secondary magnesium battery. The organosulfur polymer has an organic conductive group or a conductive polymer as the skeleton, and contains one or more -S-S-chemical bond structures inside the molecule. The conductive properties of conductive polymers and the characteristics of high energy density of organic sulfides; the use of -S-S- bond breaking and bonding to store and release the energy of magnesium batteries; the use of organic conductive groups or conductive polymers to generate energy for sulfides Intramolecular electrocatalysis, increase the reaction speed, increase the conductivity of the material, reduce the amount of conductive agent, and increase the specific capacity; when discharging, the molecular chain skeleton remains intact, and the S-S bond is still connected to the main chain skeleton after the break, cycle stability have been improved; increasing the length of the sulfur chains in organosulfur polymers can increase the specific capacity of the material.

Mo ₃ S ₄ is currently an ideal material for secondary magnesium batteries, but it is difficult to prepare and needs to be synthesized at high temperature in a vacuum or hydrogen atmosphere. The theoretical discharge capacity can reach 122mAh/g, the actual discharge capacity is about 100mAh/g, and the discharge voltage There are two platforms, around 1.2V and 1.0V respectively (D.Aurbach, Z.Lu, A.Schechter, Y.Gofer, H.Gizbar, R.Turgeman, Y.Cohen, M.Moshkovich, E.Levi, Nature, 2000, 407:724). The invention adopts the organic sulfur polymer as the positive electrode material of the secondary magnesium battery, which has the characteristics of large capacity and high voltage platform, the initial discharge capacity can reach more than 110mAh/g, and the stable discharge voltage platform can reach about 1.6V; and it has the advantages of simple preparation , low cost, structure can be designed and so on.

Description of drawings

Figure 1 is the first charge and discharge curve of some dithiopolyaniline as the positive electrode material of the secondary magnesium battery.

Fig. 2 is the second charge and discharge curve of some dithiopolyaniline as the positive electrode material of the secondary magnesium battery.

Detailed ways

The following examples further illustrate the present invention, but do not limit the scope of the present invention.

Example 1

Add 1.63 mg of acetylene black and 1.63 mg of polytetrafluoroethylene to the finely ground 20 mg of partially dithiopolyaniline (see literature for the synthesis process of the material: Tang Zhiyuan, Xu Guoxiang, Polymer Materials Science and Engineering, 2003, 19: 175). Emulsion (concentration: 60wt%), mixed into a paste, pressed on the copper foil under 4MPa pressure, placed in an oven with a temperature of 80°C for drying, punched into pole pieces with a punch of Φ12.5mm, and punched into pole pieces at a pressure of 1MPa After tableting under pressure, put it in a vacuum oven at about 100°C for 4 hours to dry to obtain 1.5 mg of positive electrode; then transfer it to an argon glove box, use metal magnesium as the negative electrode, and use 0.25 mol L ^-1 of Mg[AlCl ₂ (C ₄ H ₉ )(C ₂ H ₅ )] ₂ /tetrahydrofuran is used as an electrolyte to make a button-type secondary magnesium battery. The test charge and discharge current density is 25mA·g ^-1 , and the charge and discharge voltage range is 0.3V-2.0V. The first charge and discharge results are shown in Figure 1, and the first discharge capacity is 115mAh/g. The result of the second discharge is shown in Figure 2. After the second discharge, the discharge platform is basically the same, stable at 1.6V and 1.1V.

Example 2

Add 1.63 mg of acetylene black and 1.63 mg of polytetrafluoroethylene emulsion to 20 mg of finely ground tetrathiodianiline (see literature for the synthesis process of materials: Tang Zhiyuan, Xu Guoxiang, Yu Bitao, Liu Chunyan, Science and Technology Progress, 2001, 8:28). (Concentration: 60wt%), mix it into a paste, press it on the copper foil under the pressure of 4MPa, put it in an oven with a temperature of 80°C, and punch it into a pole piece with a punch of Φ12.5mm. After pressing down the tablet, put it in a vacuum oven at about 100°C and dry it for 4 hours to obtain 1.5 mg positive electrode; then transfer it to an argon glove box, use metal magnesium as the negative electrode, and use 0.25 mol L ^-1 of Mg[AlCl ₂ ( C ₄ H ₉ )(C ₂ H ₅ )] ₂ /tetrahydrofuran is used as an electrolyte to make a button-type secondary magnesium battery. The test charge and discharge current density is 25mA·g ^-1 , and the charge and discharge voltage range is 0.3V-2.0V. The first discharge capacity is 100mAh/g, and two platforms appear at 1.6V and 1.0V respectively, corresponding to the bond breakage at different positions of the -SSSS structure, and two platforms also appear during the charging process, which are different potential regions electrochemical reactions that take place inside. If the material is charged first, the first discharge capacity of 110mAh/g can be achieved.

Example 3

Add 1.63mg of acetylene black and 1.63mg polytetrafluoroethylene emulsion (concentration: 60wt%), mix it into a paste, press it on the copper foil under the pressure of 4MPa, put it in an oven with a temperature of 80°C and dry it, and punch it with a punch of Φ12.5mm After the pole piece is pressed under a pressure of 1MPa, put it into a vacuum oven at about 100°C and dry for 4 hours to obtain a 1.5mg positive electrode; then transfer it to an argon glove box, use metal magnesium as the negative electrode, and 0.25mol L ^{- 1} of Mg[AlCl ₂ (C ₄ H ₉ )(C ₂ H ₅ )] ₂ /tetrahydrofuran is used as the electrolyte to make a button-type secondary magnesium battery. The test charge and discharge current density is 25mA·g ^-1 , and the charge and discharge voltage range is 0.3V-2.0V. Two discharge plateaus appeared at around 1.5V and 1.0V, and the discharge capacity increased with the increase of the sulfur mass fraction in the synthesis product. When the sulfur mass fraction was 78%, the discharge capacity could be as high as 250mAh/g.

Example 4

Add 1.63 mg of acetylene black and 1.63 mg of polyphenylene to finely ground 20 mg of polythiopolyphenylene (see literature for the synthesis process of the material: Wang Weikun, Wang Anbang, Cao Gaoping, Yang Yusheng, Chemical Journal of Chinese Universities, 2005, 26:918). Vinyl fluoride emulsion (concentration: 60wt%), mixed into a paste, pressed on the copper foil under 4MPa pressure, placed in an oven with a temperature of 80°C for drying, and punched into pole pieces with a punch of Φ12.5mm, After tableting under a pressure of 1 MPa, put it in a vacuum oven at about 100°C for 4 hours to dry to obtain a 1.5 mg positive electrode; then transfer it to an argon glove box, use metal magnesium as the negative electrode, and use 0.25 mol L ^-1 of Mg[ AlCl ₂ (C ₄ H ₉ )(C ₂ H ₅ )] ₂ /tetrahydrofuran is used as an electrolyte to make a button-type secondary magnesium battery. The test charge and discharge current density is 25mA·g ^-1 , and the charge and discharge voltage range is 0.3V-2.0V. The first discharge capacity can reach 340mAh/g.

Comparative example 1

The best and most commonly used cathode material Mo ₃ S ₄ in secondary magnesium batteries was used as a comparison (D. Aurbach, Z, Lu, A. Schechter, Y. Gofer, H. Gizbar, R. Turgeman, Y. Cohen, M. Moshkovich, E. Levi, Nature, 2000, 407:724).

Add 1.63mg of acetylene black and 1.63mg of polyvinylidene fluoride solution (with N-methylpyrrolidone as solvent, the concentration is 0.02-0.04g/mL) to the finely ground 20mg of Mo ₃ S ₄ , mix it into a paste, Press it on the copper foil under the pressure of 4MPa, put it in an oven with a temperature of 80°C and dry it, punch it into a pole piece with a punch of Φ12.5mm, press it under a pressure of 1MPa, and put it in a vacuum oven at about 100°C Drying for 4 hours to obtain 1.5 mg positive electrode; then transferred to an argon glove box, using metal magnesium as the negative electrode, 0.25mol·L ^-1 of Mg[AlCl ₂ (C ₄ H ₉ )(C ₂ H ₅ )] ₂ / Tetrahydrofuran is used as the electrolyte to make a button-type secondary magnesium battery. The test charge and discharge current density is 25mA·g ^-1 , and the charge and discharge voltage range is 0.3V-2.0V. The first discharge capacity is 90mAh/g, and there are two discharge voltage platforms, 1.2V and 1.0V respectively.

Claims (1)

1. the application of organic sulfur polymer in positive electrode material of secondary Mg battery is characterized in that application method is as follows:

With the organic sulfur polymer porphyrize, adding is that the acetylene black of 5～8wt% of benchmark is as conductive agent with the organic sulfur polymer, the concentration that with the organic sulfur polymer is 5～10wt% of benchmark is that 50～60wt% ptfe emulsion or concentration are that the N-Methyl pyrrolidone solution of 0.02～0.04g/mL polyvinylidene difluoride (PVDF) is as binding agent, be mixed into paste, under 3～5MPa pressure, be pressed on the collector, after putting into temperature and be 60～80 ℃ baking oven oven dry, drift with Φ 12～16mm is washed into pole piece, behind the pressure lower sheeting of 1～2MPa, put into 100～120 ℃ dry 3～5 hours of vacuum drying oven, obtain positive pole; Transferring in the argon gas glove box, is negative pole with the MAGNESIUM METAL again, 0.25molL ^-1Mg[AlCl ₂(C ₄H ₉) (C ₂H ₅)] ₂/ tetrahydrofuran (THF) is an electrolytic solution, makes secondary Mg battery; Wherein organic sulfur polymer is polythio polyaniline, polythio polypyrrole, polythio Polythiophene or polythio polyhenylene; Collector is Copper Foil, aluminium foil or nickel foam; The tetrafluoroethylene that tetrafluoroethylene is used for the battery binding agent; The polyvinylidene difluoride (PVDF) that polyvinylidene difluoride (PVDF) is used for the battery binding agent.

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