The manufacturing of flexible electronics requires flexible batteries. However, the development of high-performance flexible batteries has been rather slow. A majority of the available techniques are impractical and too expensive for industrial applications because of the type of equipment needed for preparing these flexible electrodes. Therefore, in this study, we developed a simple approach for fabricating free-standing flexible cathodic electrodes. The process involves the slurry casting of a well-dispersed electrode mixture comprising the active material, carbon fibers, polymer, plasticizer, and lithium salts. By adjusting the weight ratios, we realized the best trade-off between flexibility and specific capacity. The prepared free-standing flexible cathodic electrodes of lithium manganese oxide exhibited remarkably long cycling performance over 5000 cycles at 10 C versus Li metal anode with a coulombic efficiency (C.E.) > 99% The pouch cell also had excellent cycling performance of over 500 cycles at 5 C with a C.E. > 99%. This method is simple and uses current battery production line equipment without the need for new specialized equipment. This could be cost-effective and efficient for manufacturing free-standing electrodes.