Introducing ion-transport-regulating nanochannels to lithium-sulfur batteries
The ability of ion channels to facilitate the transport of some specific ions and meanwhile block other molecular or ionic species across the membranes of biological cells and intracellular organelles plays an important role in biological bodies for maintaining basic physiological activities. This feature is highly desirable in rechargeable lithium batteries because the electrochemical performances of some electrodes, such as sulfur cathodes, are greatly weakened by the dissolution of active material related anions into the electrolyte and the slow transport of lithium ions. Here, inspired by nature, a polymer membrane with negatively-charged nanochannels is applied to a sulfur-carbon cathode to overcome the poor cycling stability and rate capability of the lithium-sulfur battery. The polymer membrane possesses negatively charged nanochannels with a width dimension (ca. 2 nm) comparable to the Debye length, therefore is capable of regulating the ion transport by facilitating the transport of lithium ions and rejecting the migration of polysulfide anions. At 0.2 C and 1 C, the specific capacities keep at high levels of 1105 and 838 mA h g-1 after 100 cycles, respectively. Furthermore, at a high rate of 18 C, a high specific capacity of 612 mA h g-1 is retained over 250 cycles, with a high capacity retention of 91%.