Fluorinated graphene as a dual-functional anode to achieve dendrite-free and high-performance lithium metal batteries

Lithium metal batteries (LMBs) are suffering from dendrite growth and a low coulombic efficiency (CE) during cycling. The use of the 3D structured current collector as lithium host and an artificial solid-electrolyte interphase (ASEI) layer were both regarded as efficient methods to improve the anode performance. However, the reliable binder-free coating requires a controllable species (LiF) and conformability, which is still challenging. Herein, we propose a dual-functional coating layer that played the role of both lithium deposition host and the ASEI by predepositing fluorinated electrochemically exfoliated graphene (F-ECG) as a modifier on a working electrode in LMBs. With the ultra-strong interface and interlayer adhesion, the as-prepared coating layer could successfully prevent not only the peeling-off issue that usually happened in coating layers of carbon-based materials but also the expansion during charge/discharge cycles. Also, the LiF-rich film is constructed through the reaction of Li ions with the F species from F-ECG, exhibiting homogeneous Li plating/stripping without notable dendrite formation. As a result, the half-cell possesses a low nucleation overpotential (18 mV) and high stability for over 100 cycles with an average CE of 98.3%. The polarization profile shows remarkable performance for up to 250 h. Additionally, a full-cell LMB (NMC||F-ECG) is demonstrated to achieve excellent capacity retention of up to 72% after 70 cycles. The LiF-rich dual-functional coating layer based on F-ECG as a modifier successfully improves the long-term stability of working electrodes, paving the way to realizing potential LMBs.