Hybrid additive strategy with decoupled delivery pathways for synergistic interphase regulation in lithium metal batteries

Stabilizing both anode and cathode interphases is critical for the practical implementation of high-energy lithium metal batteries (LMBs) under high-voltage and lean-electrolyte conditions. Here, a hybrid additive incorporation strategy is presented to regulate interfacial chemistry. In this design, lithium nitrate (LiNO 3 ) is embedded within an electrospun polyacrylonitrile (PAN) interlayer, while lithium difluorobis(oxalato)phosphate (LiDFBOP) is introduced into the electrolyte, enabling decoupled additive delivery for interfacial stabilization. The LiNO 3 /PAN interlayer enables the formation of an ionically conductive, Li 3 N-rich solid-electrolyte interphase (SEI) that promotes uniform lithium deposition and enhances interfacial kinetics, while LiDFBOP facilitates the formation of inorganic-rich interphases that reinforce both the SEI and cathode-electrolyte interphase (CEI) and suppress electrolyte decomposition and transition-metal dissolution. As a result, Li‖NCM811 full cells with high cathode loading (3.5 mAh cm -2 ), ultrathin lithium metal anodes (20 μm, N/P = 1.17), and a cut-off voltage of 4.4 V achieve 79% capacity retention after 300 cycles. The hybrid system also demonstrates stable operation in pouch cells with energy densities of approximately 350 Wh kg -1 and 1070 Wh L -1 under lean electrolyte conditions of 2 g Ah -1 , as well as in anode-free cells. This work highlights that rational design of additive delivery pathways provides an effective strategy for constructing robust interphases in high-energy lithium metal batteries.