(中南大學(xué) 冶金與環(huán)境學(xué)院，長沙 410083)
摘 要: 選擇4種結(jié)構(gòu)相似但鏈長不同的鏈狀醚(Gn，n=1~4)和環(huán)狀醚1,3-二氧戊環(huán)(DOL)作為鋰硫電池的電解液溶劑，研究不同的醚種類及組成對鋰硫電池電化學(xué)性能的影響規(guī)律，探討溶劑性質(zhì)與鋰硫電池性能之間可能存在的內(nèi)部聯(lián)系。結(jié)果表明:高黏性溶劑會降低鋰硫電池的低電位放電平臺；使用純鏈狀醚作溶劑時，溶劑的施主數(shù)(DN值)與鋰硫電池性能密切相關(guān)，鋰硫電池在高DN值溶劑中雖易發(fā)生過充、庫侖效率低，但若控制DN小于19時，鋰硫電池循環(huán)期間放電容量更高。因此，在合理范圍內(nèi)，增加多硫化物在電解液中的溶解性有利于提高活性材料的利用率；而當引入DOL與鏈狀醚混合使用時，金屬鋰/電解液的界面性質(zhì)一定程度上決定鋰硫電池的性能水平，DOL由于成膜作用可以降低界面阻抗、改善鋰硫電池的循環(huán)性能，且鋰硫電池容量與庫侖效率均隨混合溶劑中 DOL含量的增加而逐步提高，但DOL含量不宜過高，鋰硫電池在適中的混合溶劑配比下才具有較好的循環(huán)穩(wěn)定性。
關(guān)鍵字: 鋰硫電池；電解液；醚；溶劑；電化學(xué)性能
（School of Metallurgy and Environment, Central South University, Changsha 410083, China）
Abstract:Four kinds of chain ethers with similar glyme-based structure and different chain length (Gn, n=1~4) and cyclic ether of 1,3-dioxolane (DOL) were selected as electrolyte solvent for lithium/sulfur (Li/S) battery. The effects of ether type and constitution on electrochemical performance of the cell were investigated, and possible relationships between basic properties of these ethers and cell performance were discussed. The results show that the low-potential discharging plateau of the cell will decline if the viscosity of the ether is high relatively. The cell performance is closely associated to the donor number (DN) of the ether when single chain ether is used as electrolyte solvent. For the case with high DN value, the severe overcharging behavior arises more easily, and the coulombic efficiency is lower than that of low DN value, but the higher reversible capacity can be obtained if the DN below is controlled to less than 19. So, increasing the solubility of polysulfides in the electrolyte within reasonable range is beneficial to improve the utilization of active material and the cell capacity. On the other hand, the interfacial properties between Li metal and electrolyte play a Key role in the cell performance when mixing different chain ethers with DOL. The presence of DOL reduces distinctly the impedance of the Li/electrolyte interface and improves the cycling capability of the cell. The discharge capacity and coulombic efficiency increase with the increase of DOL content in the mixed solvent system, but excess DOL in the electrolyte should be avoided. The optimized cycle performance appears in the appropriate mixing ratio of G1 to DOL.
Key words: lithium sulfur battery; electrolyte; ether; solvent; electrochemical performance
