Abstract
Next-generation lithium metal batteries are expected to drive the practical applications that require high energy-density storage, such as, portable electronics and electric vehicles. However, the direct use of metallic lithium causes harsh safety issues, low-grade rate, and cycling performances due to unstable solid electrolyte interphase (SEI) and undesired lithium dendrite growth. Here, the ultrathin bilayer of graphite and SiO2 is deposited on Li foil (Graphite.SiO2@Li) using Radio Frequency (R-F) sputtering to address the inherent problem of lithium metal anode. The R-F sputtered electrodes can be cycled for more than 1300 h and 550 h at a current density of 0.5 mA cm-2 and 1 mA cm-2 respectively to reach a capacity of 1 mAh cm-2. Graphite.SiO2@Li anode coupled with Lithium titanate (LTO) and Lithium Nickel Cobalt Manganese oxide (NMC111) reaches higher capacity retention (96.78% and 98.57%) compared to bare Li (92.31% % and 82.73%) respectively. Higher capacity at higher rates and long stable cycling performances with low voltage hysteresis was achieved with the use of graphite.SiO2@Li anode. The graphite layer lowers the impedance, buffers the volume expansion issue, and helps to electrically connect the plated Li with the bulk Li electrode underneath. The higher electrolyte wettability of SiO2 provides much better Li-ion transportation, and ultrathin SiO2 film allows fast Li-ion diffusion and lithiation/delithiation to slow down the growth of Li dendrites. Besides, its high Young's modulus form robust SEI, the insulating property of SiO2 blocks the electron transport, and chemical stability prevent side reaction with the liquid electrolyte.