Armor-like Inorganic-rich Cathode Electrolyte Interphase Enabled by the Pentafluorophenylboronic Acid Additive for High-voltage Li||NCM622 Batteries

Lithium metal batteries (LMBs) comprising Li metal anode and high-voltage nickel-rich cathode could potentially realize high capacity and power density. However, suitable electrolytes to tolerate the oxidation on the cathode at high cut-off voltage are urgently needed. Herein, we present an armor-like inorganic-rich cathode electrolyte interphase (CEI) strategy for exploring oxidation-resistant electrolytes for sustaining 4.8 V Li||LiNi0.6Co0.2Mn0.2O2 (NCM622) batteries with pentafluorophenylboronic acid (PFPBA) as the additive. In such CEI, the armored lithium borate surrounded by CEI up-layer represses the dissolution of inner CEI moieties and also improves the Li+ conductivity of CEI while abundant LiF is distributed over whole CEI to enhance the mechanical stability and Li+ conductivity compared with polymer moieties. With such robust Li+ conductive CEI, the Li||NCM622 battery delivered excellent stability at 4.6 V cut-off voltage with 91.2 % capacity retention after 400 cycles. The excellent cycling performance was also obtained even at 4.8 V cut-off voltage.

Automated summary

Lithium metal batteries (LMBs) with high-voltage nickel-rich cathode and Li metal anode have the potential for high capacity and power density, but electrolytes that can withstand oxidation on the cathode at high cut-off voltage are urgently needed. This study presents an armor-like inorganic-rich cathode electrolyte interphase (CEI) strategy using pentafluorophenylboronic acid (PFPBA) as an additive to explore oxidation-resistant electrolytes for sustaining 4.8 V Li||LiNi0.6Co0.2Mn0.2O2 (NCM622) batteries. The CEI, which consists of armored lithium borate and abundant LiF, improves the mechanical stability and Li+ conductivity, leading to excellent cycling performance and capacity retention even at 4.8 V cut-off voltage.