Electrolyte design for stable electrode-electrolyte interphase to enable high-safety and high-voltage batteries

Ethylene carbonate (EC)-free electrolyte is proposed to enhance the high-voltage and safety performances of practical pouch-type LiNi_0.6Co_0.2Mn_0.2O₂|Graphite (NCM622|Gr) cells. Herein, it was demonstrated that the EC-free electrolyte can effectively stabilize NCM622 cathode interface and well compatible with the graphite anode. At high operating voltage of 4.5 V, the practical pouch-type cell employing EC-free electrolyte presents superior capacity retention (85.9% after 200 cycles) and increased energy density (25.1%). More surprisingly, pouch-type cell with EC-free electrolyte can markedly address intrinsic safety concerns via increasing thermal runaway trigger temperature T₂ by ∼60 °C and extending the time from self-generated heat to triggering thermal runaway by more than 3 times. Furthermore, nail penetration test shows that the designed pouch-type cell doesn't even trigger thermal runaway such as fire and explosion. The work sheds light on EC-free electrolyte to develop the next generation of practical safer high-voltage NCM622|Gr batteries.