Engineering Densely Packed Ion-Cluster Electrolytes for Wide-Temperature Lithium–Sulfurized Polyacrylonitrile Batteries

The electrolyte plays an essential role in the advancement of lithium–sulfur batteries (LSBs), as it not only transports the charge carriers but also extensively influences sulfur conversion mechanisms and electrode–electrolyte interphases formed on the electrode surface, thereby directly impacting battery performance. However, the majority of existing electrolytes suffer from incompatibility with either the Li anode or the sulfur cathode. Here, we develop a densely packed ion-cluster electrolyte (DPIE) through the strategic combination of a weakly solvating solvent and an inert diluent, resulting in the self-assembly of abundant compact ion-pair aggregates within its structure. This peculiar solvation structure promotes fast Li+ desolvation, the formation of robust electrode–electrolyte interphases, and the suppression of polysulfide dissolution. Leveraging the tailored DPIE, room-temperature Li||sulfurized polyacrylonitrile (SPAN) batteries demonstrate 300 stable cycles with a capacity retention of 97.8% and a steady Coulombic efficiency exceeding 99.9%. Even under a limited negative/positive areal capacity ratio of four, the Li||SPAN cells exhibit good stability over 250 cycles with 97.1% capacity retention. Furthermore, Li||SPAN batteries show impressive stability over a wide temperature range spanning from −20 to 60 °C and exhibit reversibility at −10 °C over 200 cycles. This electrolyte design enables LSBs with prolonged operational lifetimes, rapid charging capabilities, and expanded temperature tolerance.

电解液在锂硫电池（Lithium-Sulfur Batteries，LSBs）的研发进程中发挥着不可或缺的关键作用：它不仅负责传输电荷载流子，还会显著影响硫的转化机制以及电极表面生成的电极-电解液界面，进而直接影响电池的整体性能。然而，当前绝大多数电解液均存在与锂负极或硫正极兼容性欠佳的问题。本研究通过将弱溶剂化溶剂与惰性稀释剂进行策略性复合，成功开发出一种致密离子团簇电解液（Densely Packed Ion-Cluster Electrolyte，DPIE），其结构内可自组装形成大量紧凑的离子对聚集体。这种特殊的溶剂化结构能够促进锂离子（Li+）快速脱溶剂化，助力形成稳定可靠的电极-电解液界面，并有效抑制多硫化物的溶解。借助定制化的致密离子团簇电解液，室温下的锂||硫化聚丙烯腈（sulfurized polyacrylonitrile，SPAN）电池可实现300次稳定循环，容量保持率达97.8%，库仑效率（Coulombic Efficiency）稳定维持在99.9%以上。即使在负极/正极面容量（areal capacity）比仅为4的严苛条件下，锂||SPAN电池仍可实现250次以上的稳定循环，容量保持率为97.1%。此外，锂||SPAN电池在-20℃至60℃的宽温度区间内均展现出优异的循环稳定性，且在-10℃下可完成200次以上的可逆循环。该电解液设计方案可赋予锂硫电池更长的循环寿命、更快的充电速率以及更宽泛的温度适用范围。