Lamellar quasi-solid electrolyte with nanoconfined deep eutectic solvent for high-performance lithium battery

Electrolytes with high-efficiency lithium-ion transfer and reliable safety are of great importance for lithium battery. Although having superior ionic conductivity (10−3–10−2 S·cm−1), traditional liquid-state electrolytes always suffer from low lithium-ion transference number $$({t_{{\rm{L}}{{\rm{i}}^ + }}},\,\, < 0.4)$$ and thus undesirable battery performances. Herein, the deep eutectic solvent (DES) is vacuum-filtered into the ∼ 1 nm interlayer channel of vermiculite (Vr) lamellar framework to fabricate a quasi-solid electrolyte (Vr-DES QSE). We demonstrate that the nanoconfinement effect of interlayer channel could facilitate the opening of solvation shell around lithium-ion. Meanwhile, the interaction from channel wall could inhibit the movement of anion. These enable high-efficiency lithium-ion transfer: 2.61 × 10−4 S·cm−1 at 25 °C. Importantly, the $${t_{{\rm{L}}{{\rm{i}}^ + }}}$$ value reaches 0.63, which is 4.5 times of that of bulk DES, and much higher than most present liquid/quasi-solid electrolytes. In addition, Vr-DES QSE shows significantly improved interfacial stability with Li anode as compared with DES. The assembled Li symmetric cell can operate stably for 1000 h at 0.1 mA·cm−2. The lithium iron phosphate (LFP)∣Vr-DES QSE∣Li cell exhibits high capacity of 142.1 mAh·g−1 after 200 cycles at 25 °C and 0.5 C, with a capacity retention of 94.5%. The strategy of open solvation shell through nanoconfinement effect of lamellar framework may shed light on the development of advanced electrolytes.