Artificial Li Ion Selective Transport Nanochannels via Defect Engineering of 2D Materials for High Performance Li Metal Batteries

Abstract Designing a functional separator to accomplish selective and uniform Li + transport is critical for preventing dendrite growth and stabilizing the interface layer of the Li electrode. However, commercially modified separators still face some challenges such as sluggish ion transport dynamics and much increased weight and thickness, which significantly impairs energy density of lithium metal batteries (LMBs). Herein, cation vacancies containing Ti 0.87 O 2 monolayer nanosheets are directionally stacked into an ultrathin 145 nm Li + ‐selective transport layer. The ultrathin functional layer guarantees the low electrode‐separator interface impedance and reduces the mass of the functional layer. The abundant Li + ‐selective nanochannels induced by cation vacancies enable high‐speed and uniform Li + transport flux and a high Li + transference number (0.83), thereby promoting the dense deposition of Li metal. Consequently, the symmetric Li||Li cell exhibits stable cycling of over 3000 h at 1 mA cm −2 for 1 mAh cm −2 . Remarkably, the Li||NCM811 pouch cell delivers a high energy density of up to 450.8 Wh kg −1 and enhanced cycling lifespan. This work inspires the rational design of advanced separators with ion transport management for high energy density LMBs.