Ultrathin zwitterionic polymeric interphases for stable lithium metal anodes

Lithium metal electrodeposits in the form of irregular morphological features, loosely termed dendrites, on planar anode substrates. The deposits may lead to rapid battery failure and safety concerns. Due to the highly reducing nature of Li (-3.04 V versus standard hydrogen electrode [SHE]), a solid electrolyte interphase (SEI) inevitably forms at the electrode/electrolyte interface, which regulates the subsequent electrodeposition of Li. Rational design of the chemical, mechanical, and ion transport properties of SEI plays an important role in determining the morphology of electrodeposited metals. We report on using initiated chemical vapor deposition (iCVD) to create ultrathin conformal zwitterionic polymeric inter phases with precise thicknesses in the range of 10-500 nm. It was found that zwitterionic moieties are able to tune the solvation environment of the lithium cation at the electrode/electrolyte interface, enabling compact, planar deposition of the lithium metal. These findings provide new directions for designing ionic polymeric inter phases for metal anodes.