Revolutionizing anode-free batteries with holey graphene interlayers: Achieving uniform lithium deposition and long-term stability

초록

The expansion of the electric vehicles (EVs) market has highlighted the need to develop batteries with high energy density and efficiency with stable performance. To address this need, researchers have proposed anodefree batteries, a promising solution that reduces battery volume by eliminating the need for anodes. However, anode-free batteries encounter challenges such as reduced cycle life and compromised cycling stability, mainly due to a shortage of lithium sources and the issue of lithium dendritic growth caused by irregular Li deposition. A critical concern is the formation of an unstable Solid Electrolyte Interphase (SEI) layer on current collectors, prompting numerous studies to address this challenge. This study proposes a novel approach involving the coating of copper (Cu) current collectors with holey graphene (HG) to enhance the stability of anode-free batteries. HG, known for its abundance of holes on the basal plane and a lower Fermi level compared with conventional graphene (GR) due to defects, proves effective in inhibiting electron transfer to the lowest unoccupied molecular orbital (LUMO) of the electrolyte. This inhibition prevents ongoing electrolyte decomposition and supports the formation of a stable SEI. In addition, HG suppresses lithium dendritic growth by promoting uniform Li deposition. This approach is attributed to the thin and uniform SEI structure initially formed on the surface of the HG. In testing anode-free batteries using HG, GR, and uncoated Cu, the HG-based anode-free full cell exhibited remarkable performance. It demonstrated a high coulombic efficiency (CE) of 99.6 % during 200 cycles, even without the inclusion of Li metal. Moreover, capacity characteristics of the full cell with the HG surpass those of a full cell using GR.

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