A Tailored Multifunctional Lithium Organosilicate Salt Constructing Robust Interphases for High Voltage Lithium Metal Batteries

ABSTRACT

Lithium metal batteries (LMBs) have attracted extensive attention due to their high energy density. However, when lithium (Li) metal is paired with high‐voltage cathode materials, its practical application is limited by issues such as continuous oxidative decomposition of electrolytes and the incompatibility between electrolytes and aggressive electrodes. Herein, we synthesize a fluorinated lithium organosilicate salt (i.e., lithium fluorobis(fluoropinacolatoborato)silicate, LiPBS) to address the aforementioned challenges. The results show that the LiPBS can form a protective and rigid‐flexible cathode electrolyte interphase (CEI) on the cathode surface. Simultaneously, PBS ⁻ readily forms a coordination ion pair (CIP) with Li ⁺ , constructing an inorganic‐rich solid electrolyte interphase (SEI) on the Li anode. Furthermore, Si─O groups in the LiPBS can effectively scavenge HF and H ₂ O from the electrolyte. These advantageous properties enable LiCoO ₂ (LCO, 1.89 mAh cm ⁻² )/Li (50 µm) coin and pouch cells to exhibit excellent cycling performance at high voltages and elevated rates‒for example, retaining 82% capacity after 250 cycles at 1 C and 4.5 V, compared to 80% retention after only 67 cycles for the LiPF ₆ ‐based counterpart. This performance is maintained even at an elevated temperature of 50°C. This work highlights the crucial role of lithium organosilicate salt in determining the electrochemical performance of LMBs.