Porous SnO₂/C Nanofiber Anodes and LiFePO₄/C Nanofiber Cathodes with a Wrinkle Structure for Stretchable Lithium Polymer Batteries with High Electrochemical Performance

Stretchable lithium batteries have attracted considerable attention as components in future electronic devices, such as wearable devices, sensors, and body-attachment healthcare devices. However, several challenges still exist in the bid to obtain excellent electrochemical properties for stretchable batteries. Here, a unique stretchable lithium full-cell battery is designed using 1D nanofiber active materials, stretchable gel polymer electrolyte, and wrinkle structure electrodes. A SnO₂/C nanofiber anode and a LiFePO₄/C nanofiber cathode introduce meso- and micropores for lithium-ion diffusion and electrolyte penetration. The stretchable full-cell consists of an elastic poly(dimethylsiloxane) (PDMS) wrapping film, SnO₂/C and LiFePO₄/C nanofiber electrodes with a wrinkle structure fixed on the PDMS wrapping film by an adhesive polymer, and a gel polymer electrolyte. The specific capacity of the stretchable full-battery is maintained at 128.3 mAh g⁻¹ (capacity retention of 92%) even after a 30% strain, as compared with 136.8 mAh g⁻¹ before strain. The energy densities are 458.8 Wh kg⁻¹ in the released state and 423.4 Wh kg⁻¹ in the stretched state (based on the electrode), respectively. The high capacity and stability in the stretched state demonstrate the potential of the stretchable battery to overcome its limitations.