Lithium-sulfur battery

Abstract

The invention relates to a lithium-sulfur battery. An electrolyte of the lithium-sulfur battery consists of solvent molecules, solute positive ions, and solute negative ions; the molar concentration of the solute in the electrolyte is 0.1-10M; the solute positive ions comprise one or more than two kinds of alkali metal positive ions, alkaline earth metal positive ions, quaternary ammonium ions, pyridinylamino ions, imidazolylamino ions, quaternary phosphonate positive ions, pyrimidinium positive ions, pyrazolium positive ions, pyridazinium positive ions, thiazolium positive ions, oxazolium positive ions, triazolium positive ions and phosphonium and ammonium positive ions, and the molar concentration of the solute positive ions is 0.1-10M. The charging process of the lithium-sulfur battery is opposite to that of a conventional lithium-sulfur battery, so that the problem that lithium polysulfide is dissolved into the electrolyte and diffused to a negative electrode is solved fundamentally; and the electrolyte is in a liquid state, so that the problem of electrode interface mass transfer existing in an all-solid-state electrolyte does not exist.

Description

technical field [0001] The present invention generally relates to an electrode using sulfur as an active material, and more specifically relates to the application of a lithium-sulfur battery. Background technique [0002] In 1962, Herbert and others applied for a patent for using elemental sulfur as the positive electrode of the battery, and the research and development of lithium-sulfur batteries officially kicked off. The data show that the abundance of sulfur in nature is about 0.048wt%, and it is a natural resource that has not been fully utilized. Sulfur in nature is mainly elemental sulfur (S 8 ) form, has the characteristics of low toxicity, low price, large storage capacity and low density, and has a specific capacity as high as 1,675mAh / g, which is currently known as the cathode material with the highest specific capacity. Lithium is also the metal with the most negative potential and the highest energy density in nature. The battery composed of lithium and sulfu...

AI Technical Summary

Problems solved by technology

However, due to the electronic / ion insulation of the positive elemental sulfur of the lithium-sulfur battery, the dissolution mobility of the intermediate product lithium polysulfide, and the inhomogeneity of the dissolution and deposition of metal lithium, the cycle and safety of the lithium-sulfur battery are very poor.

Research in the 20th century was limited to improving the reactivity of elemental sulfur by adjusting temperature and solubility, and it was difficult to solve the spontaneous reaction between lithium polysulfide and lithium metal and potential safety hazards. Lithium-sulfur batteries have not been fully developed, and people have shifted their work focus to Sodium-sulfur battery system with more stable high-temperature performance and lithium-ion battery system with better cycle performance

[0003] Despite the above advantages, lithium-sulfur batteries are still far away from practical use. The main problems at present include: (1) The lithium metal on the negative electrode reacts with the polysulfides dissolved in the electrolyte, and the elemental sulfur on the positive electrode side gradually The generated polysulfide enters the electrolyte, and then reacts with metal lithium, which eventually causes the loss of positive and negative active materials and the collapse of the region; (2) During the discharge process of the lithium-sulfur battery, the formed polysulfide enters the electrolyte and is highly rich The accumulated polysulfides lead to an increase in the viscosity of the electrolyte, resulting in a decrease in the conductivity of the electrolyte and a significant drop in battery performance; (3) The operating temperature of the lithium-sulfur battery system is as high as 300-400°C, which requires more expensive high-temperature-resistant materials and complex The preparation process to prevent the battery from burning

1) "Electrochimica Acta70, 2012, 344–348" reported the work of Sheng S. Zhang adding the additive lithium nitrate to the electrolyte. The addition of lithium nitrate can form a protective layer on the surface of the lithium negative electrode, but the protective layer It will be consumed gradually, and will gradually fail after a dozen charge and discharge cycles

2) "Journal of Power Sources" (Journal of Power Sources 183, 2008, 441–445) introduced another method, that is, adding toluene, methyl acetate, etc. to the electrolyte to inhibit the dissolution of polysulfides, but this The method is easy to cause a drop in the conductivity of the electrolyte

The lithium-sulfur battery is characterized by a relatively large volume change, and the dissolution and deposition of lithium ions are not fixed, so this solid ceramic film is difficult to withstand the long-term operation of the battery.

In summary, although the above method has a positive effect on organizing the shuttle effect of lithium polysulfides, it cannot essentially limit the dissolution of lithium polysulfides, and it cannot essentially prevent the possibility of lithium polysulfides diffusing to the negative electrode.

The coulombic efficiency of the developed lithium-sulfur battery is difficult to reach 100%, and the best level can only be between 95% and 99%.

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