Fast-Charging High-Specific Lithium Metal Batteries Enabled by Oleophilic Garnet Suspension Electrolyte

Abstract

Realizing fast charging in high-specific-energy lithium metal batteries (LMBs) remains a significant challenge. Here, a oleophilic garnet suspension electrolyte design is reported, using inorganic solid electrolyte modified by low-surface-energy 1H,1H,2H,2H-perfluorooctyl trichlorosilane (PFOTS), to address the dilemma of fast charging and high specific energy in LMBs. With the oleophilic suspension electrolytes, the ionic conductivity of carbonate electrolyte is increased by ≈20%. Importantly, Li⁺ transference number is increased by ≈50% (reaching 0.57). Furthermore, the oleophilic suspension electrolyte regulates the solid electrolyte interphase (SEI), resulting in improved Coulombic efficiency (from 98.9% to 99.5%) and decreased Li/electrolyte interfacial impedance (from 263 to 86.5 Ω). As a result, LMBs using LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) cathode and the oleophilic suspension electrolyte achieves a remarkable capacity retention of 81.7% at the 500th cycle under fast charging of 4 C rate. In the LMBs at high NCM811 loading of 18 mg cm⁻², a cyclability of 89% capacity retention after 200 cycles along with limited increase in electrode overpotential is accomplished at a critical current density of 1.08 mA cm⁻². The fast charging and remarkable cyclability are attributed to the enhancement of electrolyte transport capabilities and generation of a favorable solid electrolyte interphase at the Li surface.