A method for inhibiting polysulfide shuttles in lithium-sulfur batteries

Abstract

The invention relates to a method for inhibiting polysulfide ion shuttles in lithium-sulfur batteries. A complexing agent is added to the catholyte or the positive electrode of the lithium-sulfur battery to form a polysulfide ion complex at the cathode of the lithium-sulfur battery. Reduce the diffusion speed of polysulfide ions and slow down their diffusion speed to the negative electrode; the complex compound is formed by combining complexing agent and polysulfide ion; the complexing agent can be an organic compound containing nitrogen. The complexing agent will not affect the electrochemical activity of polysulfide ions, nor will it affect the dissolution and deposition reaction of metal lithium on the negative electrode; at the same time, it can prevent the side reaction between polysulfide lithium and lithium sheet, and protect the role of metal lithium.

Description

technical field [0001] The present invention relates generally to lithium-sulfur batteries, and more particularly to diffusion inhibition of polysulfide-containing ions within sulfur batteries. Background technique [0002] Lithium-sulfur batteries have been developed in the 1990s, but they have been silent for a while. Now, due to its incomparable high specific energy and other properties, it has received the attention of researchers again. Relevant research work at home and abroad has been quite active in recent years, and it is now at the critical stage of technological breakthroughs. Typical rechargeable batteries of this type include an anode with lithium metal as the active material, a lithium metal alloy as the active material, or a lithium metal / carbon composite as the active anode material. Such batteries include a cathode that contains sulfur as the active material. [0003] When charging a lithium-sulfur battery, lithium ions at the anode are reduced to lithium...

AI Technical Summary

Problems solved by technology

[0005] Despite the above advantages, lithium-sulfur batteries are still far from being practical. The current main problems include: (1) The lithium metal on the negative electrode reacts with the lithium polysulfide dissolved in the electrolyte, and the elemental sulfur on the positive electrode side gradually The generated lithium 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 lithium polysulfide enters the electrolyte and is highly rich The accumulated polysulfide lithium causes the viscosity of the electrolyte to increase, 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 Acta 70, 2012, 344–348" reported the work of Sheng S. Zhang adding complexing agent 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 will be consumed gradually, and will gradually fail after more than a dozen charge and discharge cycles.

2) "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 lithium polysulfide, 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.

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