Engineering and construction of multi-functional Janus separator for high-stability Li-CO2 battery.

Due to the high theoretical energy density, lithium-carbon dioxide (Li-CO2) batteries provide unique advantages when using CO2 to generate electricity. However, the issues with lithium dendrite generated by uneven deposition and quick cathode passivation continue to impede the development of Li-CO2 batteries. In this work, a Janus separator with dual functionalities is created using an in-situ growth and hydrothermal technique. It can be used to expand the cathode to alleviate the quick passivation of the cathode, in addition to inhibiting the growth of lithium dendrite. On the one hand, as an ion transport framework, Prussian blue (PB) nanocubes formed in-situ on the anode side can control the uniform transport of Li-ions and prevent the proliferation of lithium dendrites. The Prussian blue and reduced graphene oxide composite material (PB-rGO) on the cathode side, on the other hand, can be employed as an extension of the cathode, which not only contains more discharge products but also encourages their decomposition, playing a self-cleaning role. Moreover, the Li||Li symmetrical battery with Janus separator exhibits a steady cycle life of more than 1700 h. Also, when applied to a Li-CO2 battery, it demonstrates an extremely high discharge capacity of 12100 mAh g-1 and an exceptionally long cycle life of 3144 h.