Yue Gao1 Tianhang Chen1 Qingquan Huang1 Thomas Mallouk1 Donghai Wang1

1, The Pennsylvania State University, University Park, Pennsylvania, United States

Rechargeable battery technology based on the lithium (Li) metal anode is plagued by the unstable solid-electrolyte interphase (SEI), which grows upon cycling and is associated with dendritic/mossy Li deposition. A key challenge in improving SEI stability lies in regulating its chemical composition and nanostructure. Here we report a new approach that enables the design of SEI layers with tunable structure and stable properties. This involves the use of a reactive polymeric composite, which can generate a stable SEI layer in situ by reacting with Li to occupy surface sites and then electrochemically decomposing to form nanoscale SEI components. Cryo-TEM shows that the resulting SEI layer is composed of organic polymeric Li salts, nanoparticles of inorganic Li salts, and two-dimensional nanosheet components. This conformal nanocomposite SEI layer exhibits excellent passivation, homogeneity, ionic conductivity, and mechanical strength and stabilizes the interface for dendrite-free Li deposition in a conventional carbonate electrolyte. 950-cycle life was achieved in a full cell paired with a LiNi0.5Co0.2Mn0.3O2 cathode. Moreover, under lean electrolyte conditions, the full cells also show significantly extended cycle lives, owing to the excellent stability of the polymeric nanocomposite SEI.