Method for protecting negative electrode of lithium sulfur battery

Abstract

The invention discloses a method for protecting the negative electrode of a lithium sulfur battery. A lithium sulfur battery negative electrode protection additive layer is adhered to the surface of the anode of the lithium sulfur battery. An additive component forming the protection additive layer can be an inorganic compound or an organic compound; the inorganic compound is one or above two of metal oxides, nonmetal oxides, sulfides, phosphides, nitrides, borides and fluorides; and the organic compound is one or above two of ionic liquid molecules, amino acids, polycation electrolytes, polyanion electrolytes, cationic surfactants, polyoxyether and polythioether. The morphology of the liquid metal protection layer is dynamically changing, and does not physically shed or crack due to continuous dissolution and deposition of the lithium metal in order to effectively protect the negative electrode.

Description

technical field [0001] The present invention relates generally to lithium-sulfur batteries, and more particularly to the protection of lithium-metal negative electrodes contained in lithium-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 redu...

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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 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 area; (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 protection The layer will be consumed gradually, and it will gradually fail after more than a dozen charge and discharge cycles.

2) "Journal of Power Sources" (Journal of Power Sources183, 2008, 441–445) introduced another method, that is, adding toluene, methyl acetate, etc. to the electrolyte to inhibit the dissolution of polysulfides, but this method It is easy to cause a decrease 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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