Self-Standing Porous LiCoO2 Nanosheet Arrays as 3D Cathodes for Flexible Li-lon 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 LiCoO2 nanosheet arrays are grown on Au-coated stainless steel (Au/SS) substrates via a facile hydrothermal lithiation method using Co3O4 nanosheet arrays as the template followed by quick annealing in air. The binder-free and self-standing LiCoO2 nanosheet arrays represent the 3D cathode and exhibit superior rate capability and cycling stability. In specific, the LiCoO2 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 Li4Ti5O12 nanosheet arrays as anode, an all-nanosheet array based LiCoO2//Li4Ti5O12 flexible Li-ion battery is constructed. Benefiting from the 3D nanoarchitectures for both cathode and anode, the flexible LiCoO2//Li4Ti5O12 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.