Building continuous Li-ion transport channels from cathode to anode in solid-state lithium-metal batteries
Abstract
High ionic resistance at the electrolyte/electrode interfaces is considered one of the main challenges in developing solid-state lithium-metal batteries. Herein, homogeneous and continuous Li+ transport channels are constructed from the cathode to the anode to reduce the solid–solid interface resistance. This strategy involves the surface modification of polyvinylidene fluoride hexafluoropropylene (PVDF-HFP) and Li6.75La3Zr1.75Ta0.25O12 (LLZTO), which are the key components in the solid-state electrolyte, by chemically grafting zwitterionic sulfonate betaine (SB) to endow the ionic conductivity and improve the solid–solid interface compatibility. Therefore, a series of composite solid-state electrolytes were prepared by optimizing the contents of the polymer matrix (SB-PVDF-HFP), ceramic powder (SB-LLZTO), and lithium salt. The designed composite solid-state electrolyte was used as the electrolyte film and the ion-conductive binder phase in the cathode. The assembled Li/LiFPO4 cell delivered a reversible capacity of 146.6 mA h g−1 at 1.0 C, higher than the cell without surface modifications. Furthermore, the results of molecular dynamics simulation showed that higher diffusion coefficient (D) of Li+ with the modified components could promote the creation of fast Li+ transport channels in the bulk electrolyte and at the interface, facilitating the electrochemical performance of the solid-state battery.