Functional separator strategy for lean electrolyte-based lithium metal batteries with nickel-rich cathodes

Abstract

Ensuring stable cycling of lithium metal batteries (LMBs) with nickel (Ni)-rich cathodes is challenging due to degradation caused by complex interfacial interactions at both electrodes, along with the intrinsic instability of the lithium metal anode (LMA). In this study, we propose a dual-coated functional separator strategy to address the multifaceted challenges in lean-electrolyte LMBs employing Ni-rich cathodes. The graphene-coating layer in the modified separator serves as a protective barrier, preventing byproducts formed between the LMA and electrolyte from migrating across the separator to the cathode. It also enhances lithium-ion transport by immobilizing a large portion of the electrolyte on the cathode-facing side. These effects promote more uniform reaction across the cathode, which in turn alleviates localized stress and suppresses microcrack formation. In addition, the aluminum oxide-coating layer serves as an artificial solid electrolyte interphase that mechanically suppresses dendritic lithium growth and functions as a hydrofluoric acid scavenger. The modified separator-incorporated pouch-type cell with high areal capacity of 4.2 mAh cm−2 and low electrolyte-to-capacity ratio of 3 μL (mAh)−1 exhibits the capacity retention of 96.0 % and a coulombic efficiency exceeding 99.8 % for 100 cycles. This study provides a promising pathway for the practical development of high-energy LMBs.