Highly Reversible Lithium Host Materials for High‐Energy‐Density Anode‐Free Lithium Metal Batteries

Anode‐free Li metal batteries are one of the finest prospects for increasing energy density beyond that of standard lithium‐ion batteries. Conversely, the absence of Li reservoir generates unwarranted volume expansion, permitting electrolyte depletion and rapid cathode capacity consumption. To address this issue, an anode‐free Li metal battery with an ion‐conductive layer coated Cu current collector Ag/L in typical carbonate‐based electrolytes is presented. The ion‐conducting layer causes stable solid electrolyte interphase development and allows for minimal volume expansion when utilizing stable Li hosts. Via density functional theory calculation and experimental measurements and analysis, the beneficial effect of Li hosting behavior of the ion‐conductive layer is demonstrated. Furthermore, anode‐free electrochemical performance with high discharge capacity retention, which is exceptional in a traditional carbonate electrolyte with LiNi0.8Mn0.1Co0.1O2 based cathode (4.2 mAh cm−2) and high current density (2.1 mA cm−2) is shown. To prove material compatibility, argyrodite sulfide solid electrolytes instead of liquid electrolytes, which show Coulombic efficiency of 97% at 50 cycles in all‐solid‐state Li half‐cells are used. The ion‐conducting layer coated Cu current collector (BPEI‐Ag/LiNO3) causes stable solid electrolyte interphase development and allows for minimal volume expansion when utilizing stable Li hosts. Furthermore, the BPEI‐Ag/LiNO3 electrode significantly enhances the cycling stability of anode‐free batteries in the carbonate‐based electrolytes with high areal capacity (4.2 mA h cm−2) and high current density (2.1 mA h cm−2).