Preparation method of positive electrode of lithium-sulfur battery

Abstract

The invention relates to a method for preparing a positive electrode of a lithium-sulfur battery, Fe 3 The preparation of the C@C / S composite material includes the following steps: drop the mixed solution B into the mixed solution A, and mix well to obtain the mixed solution C; freeze-dry the mixed solution C to obtain a lyophilized product; the mixed solution A includes urea , metal salt and surfactant and water, metal salt includes iron salt and / or ferrous salt; Mixed solution B includes glucose compound, silicon dioxide, acid and water; After the lyophilized product is carried out carbonization, separate out Fe 3 C@C composite material; Fe 3 C@C composites are mixed with sulfur-containing compounds and heat-treated to obtain Fe 3 C@C / S composite materials. Fe of the present invention 3 C@C composites can accelerate the redox reaction of polysulfides, effectively inhibit the shuttling of polysulfides and the formation of surface passivation layer, and finally obtain a lithium-sulfur battery with high surface capacity at low temperature.

Description

technical field [0001] The invention relates to the technical field of batteries, in particular to a method for preparing a positive electrode of a lithium-sulfur battery. Background technique [0002] Lithium-sulfur batteries have a high theoretical specific energy (2600 Wh kg -1 ), is considered to be one of the new secondary battery systems most likely to be practical after lithium-ion batteries. However, it has been 60 years since the lithium-sulfur battery was invented, and it has not yet achieved a real scale application, mainly due to the following two reasons: [0003] (1) Low areal capacity and high E / S ratio: Due to the electronic and ion insulating properties of elemental sulfur and the discharge product lithium sulfide itself, a large amount of conductive agent needs to be added to the positive electrode, resulting in the majority of lithium-sulfur battery positive electrode materials. Sulfur content < 64%, sulfur loading per unit area < 2 mg cm -2 , the...

AI Technical Summary

Problems solved by technology

However, when the sulfur loading is increased, more polysulfides will be enriched on the surface of the sulfur carrier during the discharge process, resulting in a slow redox conversion of polysulfides and a rapid passivation of the carrier surface (generated Li 2 S 2 / Li 2 S passivation layer), which reduces the effective reactive active sites and exacerbates the shuttle effect, which leads to rapid capacity fading of Li-S batteries

[0004] (2) Poor low-temperature performance: When exposed to extreme environments, excellent low-temperature performance is essential for practical secondary batteries

However, secondary batteries usually have poor electrochemical performance at low temperatures due to low ion diffusion and electrochemical reaction kinetics

For lithium-sulfur batteries, the low operating temperature also reduces the thermodynamic diffusion of polysulfides, triggers the enrichment of polysulfides on the surface of the carrier, and further causes severe shuttling of polysulfides.

[0005] In addition, there are currently few studies on low-temperature lithium-sulfur batteries, especially high-area-capacity lithium-sulfur batteries at low temperatures have not been reported.

The reported low-temperature lithium-sulfur batteries are all obtained under low-load conditions, and the sulfur load is generally between 1 and 3 mg cm -2 , the resulting low-temperature lithium-sulfur batteries have an areal capacity lower than the 4 mAh cm of current commercial lithium-ion batteries -2 , has no practical application value

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