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 _0.8 Co _0.1 Mn _0.1 O ₂ (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.