The sulfolane-based liquid electrolyte with LiClO₄ additive for the wide-temperature operating high nickel ternary cathode

An adequate wide temperature electrolyte for high nickel ternary cathode is urgent to further develop high energy density batteries. Herein, a comprehensive double-salt local high-concentration sulfolane-based electrolyte (DLi) is proposed with specific sheath structure to build stable interface on the LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) cathode at wide operating temperature between −60 and 55 °C. Lithium perchlorate (LiClO₄) in combination with high concentration lithium bis-(trifluoromethanesulfonyl) imide (LiTFSI) strengthens the internal interaction between anion and cation in the solvation structure, increasing Li⁺ transference number of the electrolyte to 0.61. Moreover, the structure and component characteristics of the passive interface layer on NCM811 are modulated, decreasing desolvation energy of Li⁺ ions, benefiting Li⁺ transport dynamics especially at low temperature, and also ensuring the interfacial stability at a wide operating temperature range. As a result, the cathode with DLi exhibits excellent high-temperature storage performance and high capacity retention of 80.5% in 100 cycles at 55 °C. Meanwhile, the Li||NCM811 cells can deliver high discharge capacity of 160.1, 136.1, and 110.3 mAh·g⁻¹ under current density of 0.1 C at −20, −40, and −60 °C, maintaining 84.5%, 71.8%, and 58.2% of the discharge capacity at 30 °C, respectively. Moreover, it enables NCM811 cathode to achieve a reversible capacity of 142.8 mAh·g⁻¹ in 200 cycles at −20 °C and 0.2 C. Our studies shed light on the molecular strategy of wide operational temperature electrolyte for high nickel ternary cathode.