In-situ construction of high-mechanical-strength and fast-ion-conductivity interphase for anode-free Li battery

The solid electrolyte interphase (SEI) with strong mechanical strength and high ion conductivity is highly desired for Li metal batteries, especially for harsh anode-free batteries. Herein, we report a pragmatic approach to the in-situ construction of high-quality SEI by applying synergistic additives of LiNO3 and ethylene sulfite (ES) in the electrolyte. The obtained SEI exhibits a high average Young’s modulus (9.02 GPa) and exchanging current density (4.59 mA cm−2), which are 3.0 and 1.2 times as large as those using the sole additive of LiNO3, respectively. With this improved SEI, Li-dendrite growth and side reactions are effectively suppressed, leading to an ultra-high Coulombic efficiency (CE) of 99.7% for Li plating and stripping. When applying this improved electrolyte in full cells, it achieves a high capacity retention of 89.7% for over 150 cycles in a LiFePO4||Li battery (∼12 mg cm−2 cathode, 50 μm Li) and of 44.5% over 100 cycles in a LiFePO4||Cu anode-free battery.