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

Abstract

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 (LiBF 4 ) and lithium nitrate (LiNO 3 ) dual-salt additives via solvation structure manipulation. We find the LiBF 4 additive can not only improve the stability of the high-voltage NCM811 cathode, but also play a role in assisting the dissolution of LiNO 3 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 0.8 Co 0.1 Mn 0.1 O 2 (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 ). • LiBF 4 is found to overcome the solvation barrier of LiNO 3 in ester solvents via ion association. • The protective effect of LiBF 4 for high-voltage NCM811 cathode is revealed. • Chunky lithium metal deposition is achieved in ester electrolyte with the action of LiNO 3 . • The LiNO 3 renders both highly-conductive interfacial layers for Li anode and NCM811 cathode. • The 4.4 V-Li/NCM811 cell realizes the capacity of ~185.6 mAh g −1 even at 5 C charge rate (~10 mA cm −2 ).