Ultra-thin anodes with controlled thickness modified by in situ Li3N for high-energy-density lithium metal batteries

Abstract

The employment of thin lithium metal anodes (LMAs) to regulate plating/stripping behaviour can achieve high energy density lithium batteries. However, the routine Li metal foils inevitably face significant challenges in commercial availability due to the mechanical fragileness and poor machinability. Here, we provide a simple process to synthesize thin, freestanding LMAs with controllable thickness (10 ~ 50 μm) using graphene oxide (GO) substrate, and generate an in situ artificial interfacial layer of Li3N on the electrode surface, which enhances Li wettability and guides the homogeneous deposition of Li. The well-designed 3D structure shortens the Li+ transport path, and the nitrogen-doped carbon nanofibres (NCF) interspersed longitudinally between the graphene layers increase the electron transport efficiency and improve the electrical conductivity. The ultrathin material with controllable thickness reduces the lithium wastage, which is conducive to the realization of high-energy-density batteries. The ultra-thin lithium metal anode (denoted as NCF/rGO/Li3N) symmetric cell is capable of stable plating/stripping for more than 1500 h at 1 mA cm‒2. The NCF/rGO/Li3N||LFP full cell exhibits excellent performance in both liquid-based electrolytes and solid electrolytes. The NCF/rGO/Li3N||NCM811 pouch cell, with a low negative/positive (N/P) ratio (2.3), can offer an average energy density of 310 Wh kg‒1 with 93.5% capacity retention after 60 cycles. The excellent electrochemical performance of the thin LMA provides a promising avenue for achieving high-energy-density batteries.