Bianionic coordination solvation structure electrolyte for high-voltage lithium metal batteries

High-voltage lithium metal batteries (HV-LMBs) comprising Ni-rich cathodes (such as LiNi0.8Mn0.1Co0.1O2) and a lithium metal anode (LMA) are highly promising with an energy density of 500 Wh kg−1. However, the stability of the electrode/electrolyte interface of HV-LMBs presents significant challenges. In addition, LMAs have several limitations, such as dendrite growth, production of dead-Li0, and repeated collapse and reconstruction of the SEI layer. Ni-rich cathode materials suffer from rapid capacity decline and structural collapse. Herein, we report an electrolyte with a bianionic coordination solvation structure (CF1) with a high voltage window and significantly enhanced stability at the electrode/electrolyte interface. Raman spectra and molecular dynamics (MD) simulations confirmed the unique solvation structure of CF1. XPS and cryo-TEM indicate that a unique heterogeneous phase SEI of LiF-rich crystals is formed in the CF1 electrolyte, which facilitates the uniform and dense deposition of Li while inhibiting the growth of lithium dendrites. Moreover, the CF1 electrolyte has a high ionic conductivity (7.84 mS cm−1), which is favorable for rapid Li+ migration. An Li||Cu cell using the CF1 electrolyte achieved an average coulombic efficiency (CE) of 99.6%. Meanwhile, the Li||Li symmetric cell exhibits stable cycling for 1200 h (1.0 mA cm−2, 0.5 mAh cm−2). Furthermore, the Li||NCM811 full cell with the CF1 electrolyte was stable for 270 cycles, with 81% capacity retention at a cut-off voltage of 4.5 V (N/P = 2.5, 0.5 C). Our study presents a new approach for designing electrolytes for HV-LMBs, aimed at streamlining their practical implementation.