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 ( $t_{{\mathrm{L}\mathrm{i}}^{+}}$, < 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 $t_{{\mathrm{L}\mathrm{i}}^{+}}$ 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.