Patterning and a Composite Protective Layer Provide Modified Li Metal Anodes for Dendrite-Free High-Voltage Solid-State Lithium Batteries

Safety is an extremely important factor when developing Li metal anodes for high-energy-density battery systems. Lithium dendrite formation is one of the major phenomena leading to serious safety issues and poor lifetimes of lithium batteries. In this study, we applied a combined surface modification strategy to obtain stable dendrite-free Li anodes for solid-state lithium batteries (SSLBs). We coated a polydopamine (PDA)-functionalized vapor-grown carbon nanofiber (VGCF)/lithiated-Nafion (LiNf) polymer composite (VGCF@PDA/LiNf) as a protective layer onto a patterned Li metal surface to provide selective lithiophilic sites for Li deposition. We also applied a sandwich-type hybrid solid polymer electrolyte (HSE) membrane (PVDF-HFP+LiTFSI+SN/Al-LLZO@PVDH-HFP+LiTFSI+SN/PVDF-HFP+LiTFSI+SN) to enhance ionic transport between the anode and cathode due to its high Li+ ionic conductivity (ca. 3.68 × 10–4 S cm–1). The resulting SSLB assembled using a high-voltage pristine LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode and the surface-modified Li anode delivered a higher discharge capacity at 0.1C and excellent cyclability at a rate of 0.2C (capacity retention >80% for 100 cycles) when compared with the corresponding SSLB incorporating the unmodified Li anode. Furthermore, the SSLB featuring a Li2MoO4-modified NCM811 cathode exhibited outstanding cyclability, with retention greater than 83% after 200 cycles at a rate of 0.2C. This attractive electrochemical performance resulted from the prevention of structural variation and dendrite formation of the cathode and anode by the Li2MoO4 coating and the VGCF@PDA/LiNf protective layer, respectively. Hence, this strategy might be suitable for developing high-voltage battery systems with high safety and long-term stability in future SSLB applications.