High energy density and durable pouch-cell graphite-based dual ion battery using concentrated hybrid electrolytes

Graphite-based dual-ion batteries (GDIBs) represent a promising battery concept for large-scale energy storage on account of low cost, high working voltage, and sustainability. The electrolyte concentration plays a critical role in determining the energy density and cycle life of GDIBs. However, the concentrated electrolytes show low Lithium ions (Li⁺) transport kinetics, reducing their intercalation and solid electrolyte interface (SEI) formation abilities. Moreover, the GDIBs in the high cut-off voltage suffer from electrolyte degradation, and corrosion of the current collector. Herein, we report a highly concentrated electrolyte formulation based on hybrid lithium hexafluorophosphate (LiPF₆) and lithium bis(fluorosulfonyl)imide (LiFSI) salts with a super-wide electrochemical stability window (6 V) and the ability to form SEI and passivation layer on graphite anode and current collector, respectively. By regulating the concentrated LiFSI electrolyte with LiPF₆ and solvent additive, the coulombic efficiency of the graphite cathode can be further improved to ∼98%. As a result, GDIB pouch cell exhibits a capacity of 21 mAh g⁻¹ (cell level) at 50 mA g⁻¹, and 98.2% capacity retention after 300 cycles. The resultant battery offers an energy density of 90.3 Wh kg⁻¹, along with a high energy efficiency of 87% and average discharge voltage of 4.3 V.