Dual-salt-additive electrolyte enables high-voltage lithium metal full batteries capable of fast-charging ability

Rechargeable batteries using lithium metal anode and Ni-rich cathode are considered promising because of their high energy densities. However, battery failure associated with lithium dendrite growth and cathode structure degradation strongly hinders their practical use, especially during high voltage or fast charge operations. Here, we report an advanced carbonate-based electrolyte consisting of the lithium tetrafluoroborate (LiBF₄) and lithium nitrate (LiNO₃) dual-salt additives via solvation structure manipulation. We find the LiBF₄ additive can not only improve the stability of the high-voltage NCM811 cathode, but also play a role in assisting the dissolution of LiNO₃ in carbonate electrolytes via its Lewis acidity. We reveal that the unique dual-salt-additive chemistry can effect synergistically to establish robust and highly conductive solid electrolyte interphases on both anode and cathode, which enables chunky lithium metal deposition and favors the structure stability of LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) under 4.4 V. The resulting fast interfacial kinetics significantly decreases the electrode overpotential and brings the ultrahigh capacity delivery of 185.6 mAh g⁻¹ at 5 C charge rate (~10 mA cm⁻²). The full battery shows the 80.3% capacity retention even after 250 cycles with thin Li anode (45 µm) and high-loading NCM811cathode (2.4 mAh cm⁻²).