Modulating the Inner Helmholtz Plane towards Stable Solid Electrolyte Interphase by Anion-π Interactions for High-Performance Anode-Free Lithium Metal Batteries

Anode-free lithium (Li) metal batteries (AFLBs) featured high energy density are viewed as the viable future energy storage technology. However, the irregular Li deposition and unstable solid electrolyte interphase (SEI) on anode current collectors reduce their cycling performance. Here, we propose a concept of anion-recognition electrodes enabled by anion-pi interactions to regulate the inner Helmholtz plane (IHP) and electrolyte solvation chemistry for high-performance AFLBs. By engineering the electrodes with electron-deficient aromatic-pi systems that possess high permanent quadrupole moment (Qzz), the anion-pi interactions can be generated to concentrate the anions on the electrode surface and tune the IHP structure to construct a stable anion-derived SEI layer, thus achieving highly reversible Li plating/stripping process. Through designing various current collectors with different Qzz values, the intimate correlations among the surface charge of the electrode, competitive adsorption of the IHP, and SEI structures are demonstrated. Particularly, the modified carbon cloth current collector with a high Qzz value (+35.1) delivers a high average Li stripping/plating Coulombic efficiency of 99.1 % over 230 cycles in the carbonated electrolyte, enabling a long lifespan and high capacity retention of LiNi0.8Co0.1Mn0.1O2-based AFLBs with a commercial-level areal capacity (4.1 mAh cm-2).