Self‐Standing Porous LiCoO₂ Nanosheet Arrays as 3D Cathodes for Flexible Li‐Ion Batteries

Self‐standing electrodes are the key to realize flexible Li‐ion batteries. However, fabrication of self‐standing cathodes is still a major challenge. In this work, porous LiCoO 2 nanosheet arrays are grown on Au‐coated stainless steel (Au/SS) substrates via a facile “hydrothermal lithiation” method using Co 3 O 4 nanosheet arrays as the template followed by quick annealing in air. The binder‐free and self‐standing LiCoO 2 nanosheet arrays represent the 3D cathode and exhibit superior rate capability and cycling stability. In specific, the LiCoO 2 nanosheet array electrode can deliver a high reversible capacity of 104.6 mA h g −1 at 10 C rate and achieve a capacity retention of 81.8% at 0.1 C rate after 1000 cycles. By coupling with Li 4 Ti 5 O 12 nanosheet arrays as anode, an all‐nanosheet array based LiCoO 2 //Li 4 Ti 5 O 12 flexible Li‐ion battery is constructed. Benefiting from the 3D nanoarchitectures for both cathode and anode, the flexible LiCoO 2 //Li 4 Ti 5 O 12 battery can deliver large specific reversible capacities of 130.7 mA h g −1 at 0.1 C rate and 85.3 mA h g −1 at 10 C rate (based on the weight of cathode material). The full cell device also exhibits good cycling stability with 80.5% capacity retention after 1000 cycles at 0.1 C rate, making it promising for the application in flexible Li‐ion batteries.