Comparative performance of LiFePO4 and LiNi0.6Co0.2Mn0.2O2 cathode materials for lithium batteries with solid–liquid hybrid electrolytes

Solid-state lithium metal batteries have excellent safety and energy density features compared to traditional lithium-ion batteries. However, they also suffer from large interface resistance and unstable contact with lithium metal resulting in a low rate and short cycle performance. Here, we utilize liquid electrolyte (LE) drips at the Li1.3Al0.3Ti1.7(PO4)3 (LATP)/electrode interface to form a solid–liquid hybrid electrolyte and reduce the interface impedance. In addition, the resulting solid–liquid electrolyte interface (SLEI) can prevent the reduction of LATP by lithium. Li/Li symmetric batteries exhibit excellent cycle stability of 500 h at 0.2 mA cm−1 when the volume ratio of liquid electrolyte to solid electrolyte LATP is 15% (SE-15% LE). The LiFePO4/SE-15%LE/Li battery system exhibit a high discharge capacity (151 mAh g−1) at 0.1 C and an excellent capacity retention rate (96.5% after 100 cycles at 25 °C). Moreover, the NCM622/SE-15% LE/Li battery system delivers an ultrahigh specific capacity of 184.3 mAh g−1 at 0.1 C. Overall, this study compares and explains the performance of the two cathode material systems.