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To understand the role of lithium sulfide clusters in lithium-sulfur batteries

wallpapers News 2021-04-28
To understand the role of lithium sulfide clusters in lithium-sulfur batteries
As a kind of electrode material, lithium sulfide (Li2S) not only has a higher capacity but also overcomes many problems caused by pure sulfur electrodes.In particular, the performance of nanoscale (Li2S) N clusters is much better than that of bulk size Li2S cells. However, the structure, stability and performance of (Li2S) N clusters, which are crucial for improving the performance of lithium-ion batteries, remain to be studied. The most stable structure of (Li2S)n (n = 1-10) is reliably determined by the advanced swarm intelligent structure prediction method. (Li2s)n (n≥4) clusters show interesting cage structure, which is beneficial to eliminate suspended bonds and improve structural stability. Compared with the Li2S monomer, each sulfur atom in the cluster coordinates with more lithium atoms, thus extending the length of the Li-S bond and reducing the activation energy of the Li-S bond. It is worth noting that the adsorption energy increases gradually with the increase of cluster size. In addition, B-doped graphene is a good AM compared to graphene or N-doped graphene. The predicted characteristic peaks of infrared, Raman and electron absorption spectra provide useful information for in situ experimental study.
 
With the growing demand for energy-intensive batteries that can overcome the limitations of traditional lithium (Li) ion technology, Li-S (Li-S) batteries are considered the most promising candidates due to their high energy density (2600 W h kg−1) and similar structure to lithium-ion batteries. However, practical applications of lithium-sulfur batteries are still hampered by inherent problems such as low conductivity of sulfur and lithium sulfide (Li2S), large volume variation of the electrode, and dissolving of intermediate lithium polysulfide (LIPS) during circulation. These limitations result in low sulfur utilization, low coulomb efficiency and rapid capacity decay of Li-S cells. Especially in the discharge process, the uncontrolled electrodeposition of the final discharge product Li2S is a key obstacle to realize the full utilization of sulfur. Due to its electronic and ionic insulating properties, the Li2S film covering the cathode causes early electrode passivation and subsequent large polarization.This prevents discharge before the loaded sulfur is fully used.When the current density is higher and the surface sulfur load is higher, this problem becomes more prominent, which hinders the rational design of practical lithium-sulfide batteries.

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