Boosting stable lithium deposition via LiN-Enriched inorganic SEI induced by a polycationic polymer layer.

Lithium (Li) metal is a promising anode material for future high-energy rechargeable batteries due to its remarkable properties. Nevertheless, excess Li in traditional lithium metal anodes (LMAs) reduces the energy density of batteries and increases safety risks. Electrochemical pre-lithiation is an effective technique for regulating the lithium content of the anodes. However, Cu foil or other non-Li based substrates used for pre-lithiation often have inhomogeneous surfaces and high nucleation barrier, leading to uneven tip deposition of lithium metal and fragile SEI. Herein, we have designed an interfacial layer composed of nano-Si particles and cationic polymer (poly (diallyldimethylammonium chloride)) (denoted as Si@PDDA) to induce the formation of LiN-rich inorganic SEI and regulate the homogeneous plating/stripping of lithium. The uniformly dispersed nano-Si particles can decrease the Li nucleation overpotential through alloying reaction with lithium. The surface of Si nano-particles modified by PDDA contains numerous cationic sites, providing an electrostatic shielding layer to seeding the growth of Li metal and inhibiting dendrites formation. More promisingly, PDDA adsorbs electrolyte anions while transporting Li, significantly accelerating the decomposition kinetics of inorganic salts within the electrolyte. Therefore, a SEI film rich in LiN was formed on the anodes, ensuring the excellent interfacial stability and electrochemical cycling performance of LMAs. The symmetrical cells exhibit a cycle life of 900 h at 1 mA cm. Moreover, the practical full cells operate at a low negative/positive (N/P) capacity ratio (∼3) for over 160 cycles.