As one essential component of the rechargeable batteries, the main function of the separator is to separate the positive and negative electrodes, restrict the free pass of electrons and prevent short-circuit of the battery. At the meantime, it allows the metal ions in the electrolyte to migrate freely between the electrodes [21, 22].
The separator has become a bottleneck restricting the safety and performance of rechargeable batteries. Developing suitable separators will be critical to the future development of the rechargeable batteries.
We expect that, in combination with advanced electrode materials and novel electrolytes, the development of materials and structures for the functional separator greatly enhances next-generation high-energy rechargeable batteries with high cycling stability comparable with conventional lithium-ion batteries.
In order to keep up with a nationwide trend and needs in the battery society, the role of battery separators starts to change from passive to active. Many efforts have been devoted to developing new types of battery separators by tailoring the separator chemistry.
The electrolyte bridges the positive and negative electrodes by forming an ion-conductive channel between them. As one essential component of the rechargeable batteries, the main function of the separator is to separate the positive and negative electrodes, restrict the free pass of electrons and prevent short-circuit of the battery.
In this review article, the scope is limited to liquid-electrolyte batteries but excludes solid-electrolyte batteries, in which the separator is not needed because the solid electrolyte bears dual functions of both the electrolyte and the separator.